ecological assessment of the sensitivity of...

ECOLOGICAL ASSESSMENT OF THE SENSITIVITY OF LENNYMORE

BAY, LOUGH NEAGH TO SMALL SCALE WATER ABSTRACTION.

Dr Chris Harrod, D. Phil., B.Sc. (Hons)

School of Biological Sciences

Queen's University, Belfast

Medical Biology Centre

97 Lisburn Road

Belfast BT9 7BL

028 9097 2271

[email protected]

Ecological assessment of the sensitivity of Lennymore Bay, Lough Neagh to small scale water abstraction.

Project R5655BBC: School of Biological Sciences, Queen’s University, Belfast of 41

SUMMARY

1. As part of a proposed development of a biomass-fuelled power plant near Glenavy, Co.

Antrim, the developers have proposed the construction and operation of a small-scale

abstraction plant to supply water (pipe diameter = 0.45 m, abstracted flow = 160 m3.h-1)

from a site located on the shore of Lough Neagh (Lennymore Bay).

2. School of Biological Sciences, Queen’s University, Belfast were commissioned to conduct an

assessment of the likely sensitivity of this area of Lough Neagh in terms of the construction

and operation of the proposed abstraction plant.

3. The assessment involved a combined field and desk-based approach. The field component

involved a rapid assessment of the current status of several important components of the

aquatic ecology of Lennymore Bay. Fish, zooplankton and benthic macroinvertebrates were

surveyed at 15 sites located on a semi-random grid, including one site located close to the

location of the abstraction plant.

4. At the time of sampling, zooplankton densities ranged between 444 and 22 440

individuals.m-3 at the fifteen sites sampled. The zooplankton community was dominated by

cyclopoid copepods, followed by calanoid copepods. Cladoceran zooplankton were found in

extremely low densities. Comparison of average zooplankton size indicated that zooplankton

at several sites were reduced in size, including the site located close to the proposed

abstraction, possibly reflecting the impact of fish predation. Multivariate analysis of spatial

structuring within the zooplankton community indicated that the site adjacent to the

proposed abstraction plant was generally similar (>70%) to all but two of the other sites

surveyed.

5. The sediments of Lennymore Bay largely consist of sand and other hard substrates, and as

such are difficult to sample in order to assess benthic macroinvertebrate community

structure. Ekman grab sampling revealed that the abundance and diversity of

macroinvertebrates was generally low at the survey sites. At two sites, it was impossible to

actually sample benthic macroinvertebrates due to the nature of the substrate, including the

site adjacent to the proposed abstraction.

6. Results indicated that Lennymore Bay supports a diverse and abundant fish community,

dominated by roach (Rutilus rutilus) and pollan (Coregonus autumnalis), with lesser

contributions by bream (Abramis brama), brown trout (Salmo trutta), gudgeon (Gobio

gobio), perch (Perca fluviatilis), three-spined sticklebacks (Gasterosteus aculeatus) and

Atlantic salmon (Salmo salar). Unusually, no European eels (Anguilla anguilla) were captured

during the two day survey, even though local commercial fishermen reported capturing eels

in the area.

7. Univariate and multivariate statistical analyses showed evidence of spatial structuring within

the fish community, with several sites supporting significant populations of juvenile pollan

and roach, including the site adjacent to the proposed abstraction plant.



8. Using the information gathered during sampling in May 2009, previous data gathered by the

author and colleagues, and information from the scientific literature the likely ecological

impacts of the construction and operation of the abstraction facility on fish and other

aquatic taxa were estimated.

9. Our results indicate that that several areas of Lennymore bay, including an area offshore of

the proposed abstraction site represent nursery areas for juvenile fish, including pollan. The

littoral area adjacent to the proposed abstraction site supports putative pollan spawning

habitats.

10. Construction of the abstraction facility is likely to have minimal impact on the aquatic

ecology, assuming that inputs of contaminants and suspended solids are minimised and

construction is timed to avoid periods of pollan spawning and egg incubation.

11. In order to estimate the risk of entrainment, the swimming capacity of eel, pollan and roach

was compared with the velocity of the water drawn into the abstraction plant. Eels > 130

mm are unlikely to be at risk of entrainment due to their swimming capacity. The benthic

nature of eels of all sizes will further limit the likelihood of entrainment of this economically

and conservationally important species. However, the poor swimming capacity of larval

pollan and roach indicates that if present in the abstraction area, these species are at risk of

entrainment. Fishes are characterised by high levels of fecundity, and the estimated

numbers of larvae lost weekly to abstraction represent the annual reproductive output of <1

female roach or pollan, prior to the action of other mortality factors.

12. The risk of entrainment of fish can be minimised through design and the provision of

suitable screening of the water intake, and this should be considered in the construction of

any abstraction facility.

13. The significant risk to abstraction operations associated with the entrainment and possible

settlement of zebra mussels (Dreissena polymorpha) are described.



Table of Contents: Ecological assessment of the sensitivity of Lennymore Bay, Lough Neagh to small scale water

abstraction. ............................................................................................................................................. 1

1. INTRODUCTION: .............................................................................................................................. 6

1.1 Background ............................................................................................................................. 6

1.2 Lough Neagh: .......................................................................................................................... 6

1.2.1 Physico-chemical characteristics .................................................................................... 6

1.2.1.1 Hydrology .................................................................................................................... 6

1.2.1.2 Bathymetry.................................................................................................................. 7

1.2.1.3 Hydrodynamics ........................................................................................................... 7

1.2.1.4 Sediments.................................................................................................................... 8

1.2.1.5 Water temperature ..................................................................................................... 8

1.2.1.6 Dissolved oxygen ......................................................................................................... 8

1.2.1.7 Water chemistry.......................................................................................................... 9

1.2.2 Ecological characteristics .............................................................................................. 10

1.2.2.1 Primary Producers ..................................................................................................... 10

1.2.2.2 Zooplankton .............................................................................................................. 11

1.2.2.3 Invertebrates ............................................................................................................. 11

1.2.2.4 Fish ............................................................................................................................ 11

1.2.2.5 Birds .......................................................................................................................... 13

1.2.2.6 Mammals .................................................................................................................. 13

1.2.3 Socio-economic characteristics ..................................................................................... 14

1.2.3.1 Cultural heritage ....................................................................................................... 14

1.2.3.2 Fishery ....................................................................................................................... 14

1.2.3.3 Other human uses of Lough Neagh .......................................................................... 14

1.3 Aims....................................................................................................................................... 14

2. MATERIALS AND METHODS .......................................................................................................... 16

2.1 Field study ............................................................................................................................. 16

2.1.1 Sampling ........................................................................................................................ 16

2.1.2 Sample processing ........................................................................................................ 17

2.1.3 Statistical analyses ........................................................................................................ 17

2.2 Assessment of abstraction impacts ...................................................................................... 18

3. RESULTS......................................................................................................................................... 19

3.1 Field study ............................................................................................................................. 19



3.1.1 Zooplankton .................................................................................................................. 19

3.1.2 Benthic macroinvertebrates ......................................................................................... 21

3.1.3 Fish community structure ............................................................................................. 23

3.1.4 Fish population structure .............................................................................................. 27

3.1.4.1 Pollan......................................................................................................................... 27

3.1.4.2 Roach ......................................................................................................................... 27

3.1.4.3 Bream ........................................................................................................................ 28

3.1.4.4 Brown Trout .............................................................................................................. 29

3.1.4.5 Three spined sticklebacks ......................................................................................... 29

3.1.4.6 Gudgeon .................................................................................................................... 29

3.1.4.7 Perch ......................................................................................................................... 29

3.1.4.8 Salmon ...................................................................................................................... 29

3.2 Ecological effects of abstraction ........................................................................................... 29

3.2.1 Installation of the abstraction facility ........................................................................... 29

3.2.2 Impacts during the operation of the abstraction facility .............................................. 30

3.2.3 Entrainment of other taxa. ........................................................................................... 33

4. CONCLUSIONS ............................................................................................................................... 34

5. REFERENCES .................................................................................................................................. 36



1. INTRODUCTION:

1.1 BACKGROUND

Rose Energy Ltd submitted a planning application in June 2008 (reference S/2008/0630) for a

biomass fuelled power plant on a site off Ballyvannon Road, near Glenavy, adjacent to the industrial

plant of Ulster Farm By-products. The proposed development requires water for cooling and

electrical generation purposes. As such, it is proposed to construct and operate (Fig.1: Irish Grid J

121 721) a small-scale water abstraction plant (pipe diameter 0.45 m, abstraction flow 160 m3.h-1,

abstraction velocity = 0.28m.s-1) to provide water from Lough Neagh and pump the water to the

proposed power plant site via a 1.9 km long, 280 mm diameter pipeline. Rose Energy commissioned

the School of Biological Sciences, Queen’s University Belfast (QUB), on 21 May 2009 to assess the

possible ecological impacts of the construction and operation of the proposed abstraction plant.

This report has been prepared by Dr Chris Harrod, Lecturer in Fish and Aquatic Ecology at QUB, and

includes data collected in May 2009. The potential impacts of the installation and operation of the

proposed abstraction facility has also been assessed using data collected from previous work, from

information gathered from relevant scientific literature, and through discussions with relevant

experts and lough-users.

1.2 LOUGH NEAGH:

Lough Neagh is a strikingly large body of water (Fig. 1), with a total area of 383 km2 and comprises

the largest area of freshwater in the British Isles. Although there is a current absence of routine

monitoring of many key taxa, Lough Neagh remains one of the most researched bodies of

freshwater in the British Isles (Wood and Smith, 1993; Wood, 1998).

1.2.1 Physico-chemical characteristics

1.2.1.1 Hydrology

The Lough Neagh catchment drains an area of ca. 4 450 km, equivalent to approximately 43 % of

Northern Ireland, and includes a small area of the republic of Ireland (Carter, 1993a). Six major

afferent rivers (Fig. 1) flow into Lough Neagh (Main, Balinderry, Six Mile Water, Moyola, Blackwater

and the Upper Bann), and a single efferent river, the Lower Bann, drains to the north into the

Atlantic Ocean, via the smaller Lough Beg. Two smaller rivers, (Glenavy and Crumlin) flow into Lough

Neagh to the north of the proposed abstraction point. The catchment is partly delimited by upland

areas; to the west the Sperrin Mountains, to the north-east, the Antrim Plateau, and to the south-

east, the Mountains of Mourne (Carter, 1993a). The Lough Neagh catchment, like much of Northern

Ireland is primarily agricultural, with large areas of improved grassland being given over to dairy and

beef production (Carter, 1993a; Wood, 1998). The average annual precipitation in the catchment is 1

095 mm.y-1 (Betts, 1982 – in Carter, 1993a).



1.2.1.2 Bathymetry

Although Lough Neagh is extremely large, it is relatively shallow (Fig. 1). The lough bed is flat, with a

mean depth of only 9.8 m, and less than 3 % of the lough area is deeper than 16 m (Douglas, 1997).

Only in the north-western area of the lough is there a significant deepwater area (maximum depth =

34 m). Lough water levels have been subject to various regulatory schemes over the past 150 years

in order to reduce flooding and improve navigation (Harron and Rushton, 1986; Carter, 1993a).

Water levels are currently regulated at +12.5 m O.D. Belfast through the operation of sluice gates at

Toome. Lennymore bay is largely shallow, with most areas falling below 6 m (Figs. 1 & 2).

Figure 1: Lough Neagh showing afferent and efferent rivers, main bays and simplified bathymetry. Also shown is the approximate location of the proposed abstraction point in Lennymore Bay.

1.2.1.3 Hydrodynamics

Although its catchment is largely bounded by upland areas, Lough Neagh itself is extremely exposed,

with a maximum effective fetch of ca. 30 km (Douglas and Rippey, 2000). This, combined with its



shallow nature and the strong south-westerly winds (mean wind speed 5 m.s-1) characteristic of the

region (Hueston, 1993), ensures that the water column rarely stratifies and is typically isothermal

and well oxygenated (Carter, 1993b; Hueston, 1993). However, biological activity is such that during

periods of high temperature and low winds, water column dissolved oxygen concentrations can fall

rapidly (Griffiths, 2007). Wind-driven circulation of the water column causes resuspension and

mobilisation of the lough’s sediments (Douglas and Rippey, 2000). Sediment resuspension can

liberate phosphorous, which in turn can promote phytoplankton growth (Gibson and Stewart, 1993).

However, Jewson (1976) demonstrated that light penetration could sometimes be so reduced by

sediment resuspension as to limit phytoplankton growth.

1.2.1.4 Sediments

Lough Neagh acts as a net sediment trap for materials transported from elsewhere in the catchment

by the afferent rivers (Carter, 1993b; Douglas, 1997). The bottom sediments of Lough Neagh can be

largely divided into two principal zones, the littoral (< ca. 6 m) and the profundal, which are divided

by a transitional zone (Carter, 1993b). The sediments of the littoral zone are typically coarse-grained

(e.g. sands, gravels, mixed sands and clays) whilst the larger profundal area is dominated by fine-

grained biogenic muds (Carter, 1993b). The shoreline of Lough Neagh includes rocky, exposed bays

and sheltered sandy bays, some of which support reed beds and stands of macrophytes. The

proposed abstraction point is located on the shore of Lennymore Bay (Fig. 1), which is largely sandy

although it includes areas of gravel, cobble and rocky substrate (Winfield and Wood, 1988; McKenna

et al., 2008).

1.2.1.5 Water temperature

The seasonal pattern of water temperature is less marked in Lough Neagh than would be predicted

by its latitude (54°), which is similar to Labrador (Canada), and Moscow. Water temperatures can fall

to ca. 1°C between January to March, but in most winters median monthly temperatures remain

above 4°C (Table 1), and Lough Neagh very rarely freezes. Water temperatures increase through

spring, reaching a peak during August in most years, (median August1969-99 temperature =16.4°C). The

water column generally remains isothermal, but can stratify during periods of relative calm (Gibson

and Stewart, 1993; Harrod, unpublished data). Median annual temperature between 1968-1999 was

9.8°C (Table 1). There is a certain amount of interannual variation in water temperature, and

Griffiths (2007) reported that water temperatures rose significantly between 1994 and 2005, whilst

the annual period during which temperatures exceeded 16 °C doubled during this period.

1.2.1.6 Dissolved oxygen

As noted above, Lough Neagh is extremely exposed to winds, and hence is typically well mixed, with

thermal stratification only occurring during rare periods of calm. However, when these events occur,

the extreme productivity of the sediments and water column ensures that oxygen is rapidly stripped

from the water column (Gibson and Stewart, 1993).



Table 1: Descriptive statistics summarising monthly variation in Lough Neagh surface temperature between 1968 – 1999 (Data source: Dr Bob Foy, AFBI & Dr David Griffiths, University of Ulster)

Month Median 25th 75th

January 4.0 3.0 5.0

February 4.0 3.0 4.6

March 5.0 4.0 5.8

April 7.6 6.5 8.5

May 11.0 10.0 12.4

June 14.1 13.0 15.6

July 16.0 15.0 17.4

August 16.4 15.7 17.5

September 14.3 13.4 15.5

October 11.5 10.0 12.4

November 7.8 6.6 9.0

December 5.8 5.0 6.4

Annual 9.8 5.5 14.3

1.2.1.7 Water chemistry

A large component of the scientific interest directed towards the lough has been focused towards

describing, understanding and countering the effects of cultural eutrophication (Wood and Smith,

1986). Following detailed assessment of the nutrient budget of Lough Neagh, it was shown that the

critical nutrient limiting was phosphorous (Smith, 1993). Water quality today is now indicative of a

hypereutrophic lake system (OECD, 1982), with elevated concentrations of phosphorous, and

chlorophyll a (Table 2).

Table 2: Some physico-chemical characteristics of Lough Neagh. Note: samples collected at ca. 11 m, from the open lough at Irish Grid reference J 02351 70705 between January 1998 and November 1999 (Carter and Griffiths, 2001).

Variable (unit) Median value 25th quartile 75th quartile Max n

Secchi depth (m) 1.5 1.20 1.86 2.1 14

Dissolved O2 (% saturation) 90 88 99.5 128 14

Total suspended solids (mg l-1) 6.25 4 10 12 14

pH 8.08 7.01 8.57 9.2 14

BOD (mg l-1) 1.14 0.39 2.98 4.6 14

COD (mg l-1) 36.3 24.8 53.3 82.3 12

Total phosphorus (mg l-1) 0.17 0.12 0.23 0.40 14

Soluble Reactive phosphorus (mg l-1) 0.05 0.03 0.10 0.26 14

Ammonium (mg l-1) 0.04 0.01 0.10 0.14 14

Nitrate (mg l-1) 0.61 0.23 1.30 3.1 14

Nitrite (mg l-1) 0.08 0.02 0.26 0.82 14

Chloride (mg l-1) 20 20 21.25 36 14

Hardness (mg l-1 Ca CO3) 113.7 111.1 125.5 163.3 13

Conductivity (µS cm-1) 290.5 279 300.5 483 14

Chlorophyll a (mg l-1) 41.73 18.33 82.55 93 14



1.2.2 Ecological characteristics

Although extremely eutrophic and isothermal (see above), Lough Neagh supports populations of

several thermally sensitive taxa more characteristic of cold, oligotrophic systems – e.g.

Monodiamesa ekmani (Carter and McLarnon, 1999), Mysis relicta (Griffiths, 2007) , and the pollan,

Coregonus autumnalis (Harrod et al., 2001; 2002). The existence of these sensitive species reflects

Ireland’s recent glacial history, which limited colonisation by species more typical of temperate

Europe, whilst the typically well-oxygenated waters of Lough Neagh have probably facilitated their

continued survival in what now is a temperate, hypereutrophic lake (Wood et al., 2000).

The Lough Neagh ecosystem has undergone marked shifts in both its structure and productivity

following lake enrichment, and the establishment of an array of invasive species including fish –

roach (Rutilus rutilus) and alien macroinvertebrates – Gammarus tigrinus, G. pulex, Crangonyx

pseudogracilis, (Battarbee and Carter, 1993; Fitzsimons and Andrew, 1993; Dick, 1996a; b). A notable

recent invader is the zebra mussel (Dreissena polymorpha) which was recently (2005) identified in

Lough Neagh (Pers. Com. Dr Derek Evans, AFBI). Where invasive, this bivalve has had marked

ecological consequences (Ward and Ricciardi, 2007), including Northern Ireland (Maguire and Grey,

2006), and settlement densities have been such to interrupted power plant operations through

reduced water flows (Kovalak et al., 1993; LePage, 1993).

1.2.2.1 Primary Producers

Primary production in Lough Neagh (> 500 g C m-2.y-1) is dominated by phytoplankton (Jewson,

1993b). The phytoplankton community is dominated for much of the annual cycle by blue-green

algae (mostly Oscillatoria redekei and O. agardhii), although diatoms (e.g. Stephanodiscus astraea

and Aulacoseira italica subsp. sub-artica) form a major peak in the spring, but which become limited

by the availability of silica (Gibson, 1993). Phytoplankton primary productivity is ultimately

controlled by the availability of nutrients, but in the turbid, well mixed water column of Lough

Neagh, the availability of light acts as a further regulatory factor (Jewson, 1976; 1993b). Jewson

(1993a) detailed the benthic algae of Lough Neagh, which due to the turbid nature of the lough

(Jewson, 1977) are restricted to a relatively limited coastal strip, where water depths do not exceed

3 m. Included in the benthic algae is an abundant population of the rare diatom Cymbellonitzschia

diluviana (Jewson, 1993a).

The turbulent, wind-driven nature of Lough Neagh restricts the distribution of macrophytes to

sheltered bays and the numerous fishing quays located around the shore (Harron and Rushton,

1986; Davidson, 1993). The distribution of submerged vegetation, which includes various

Potamogeton spp., spiked water milfoil (Myriophyllum spicatum), and Canadian pondweed (Elodea

canadensis), is further limited by the restrictive euphotic zone (ca. 3 m during summer, (Jewson,

1977). Although much reduced following the successive lowering of lake levels, areas of reedswamp

are still apparent. These include stands of the reed canary grass (Phalaris arundinacea) and common

spike grass (Eleocharis palustris) both of which are relatively resistant to wave action (Davidson,

1993). In more sheltered areas, there are considerable stands of other emergent macrophytes,

including the common reed (Phragmites australis). During summer months large populations of free-

floating plants (e.g. Lemna spp.) can develop in sheltered bays and fishing quays (Harrod pers. obs.).



1.2.2.2 Zooplankton

The zooplankton of Lough Neagh underwent marked shifts in community structure between their

first description in 1913 (Dakin and Latarche, 1913) and the late 20th century (Fitzsimons and

Andrew, 1993; Kirkwood, 1996). Currently Cyclops abyssorum dominates the zooplankton, followed

by Eudiaptomus gracilis, with Daphnia hyalina and D. longispina occurring at elevated densities

between May and October.

1.2.2.3 Invertebrates

The aquatic macroinvertebrates of Lough Neagh have been researched to varying degrees, but the

greatest focus has been on population studies of chironomid larvae (Carter, 1973; 1976; 1977; 1978;

Carter and Murphy, 1993; McLarnon, 1997), whilst the more diverse macroinvertebrate community

of the littoral zone has been less well-studied (Hynes, 1958b; Murphy and Carter, 1984; Carter and

Murphy, 1997). The chironomid larvae (known locally as Lough Neagh flies) are extremely abundant

(e.g. several thousand individuals.m-2), and on emergence as adults, they form large breeding

swarms which can cause considerable local nuisance. Bigsby (2000) conducted a detailed

examination of the distribution and abundance of the benthic fauna in the context of their

availability to overwintering diving ducks and fish. He demonstrated that chironomid larvae

dominated the benthic fauna, and that species diversity was inversely related with increased depth.

Bigsby indicated that the macroinvertebrate community of Lennymore bay as unusual in that it

supported some taxa not recorded elsewhere in his study and that sediment limited his ability to

sample at some depths (e.g. 6 m).

Lough Neagh supports one of only four extant populations of the thermally-sensitive epibenthic

shrimp, Mysis relicta, in the British Isles (Väinölä, 1994). The life cycle and behaviour of the Lough

Neagh population was detailed by Andrew & Woodward (1993). Griffiths (2007) noted that Mysis

year-class strength declined by a factor of 10 between 1995-2005, and he showed that this decline

was associated with recent increases in lough temperature. Mysis plays an important ecological role

in the lough both as a putative predator of zooplankton and as an important trophic resource for

pollan, eels, perch and brown trout populations (Anon, 1967; Bigsby, 2000; Harrod, 2001).

1.2.2.4 Fish

In reflection of their historical and current importance to human populations, the fishes of Lough

Neagh have been well researched, although little is known of the ecology of the commercially

important European eel (Anguilla anguilla) population (Winfield et al., 1993; Kennedy, 2000; Rosell

et al., 2005). It was not until the 1970s that ecologists began to study the fish of Lough Neagh in

detail. Cragg-Hine (1973) provided an early warning of the arrival of the invasive roach into the

Lough Neagh catchment. The majority of the research conducted during the 1970s was focussed on

the pollan. Ferguson examined the genetics of pollan during the 1970s (Ferguson, 1974; 1975), and

in a joint study with Himberg and Svärdson was finally able to establish its taxonomic position as

Coregonus autumnalis (Ferguson, 1974; 1975; Ferguson et al., 1978), a fish more typically distributed

in Arctic Russia and North America (McPhail, 1966). Wilson and Pitcher studied the ecology of the

pollan in detail in the 1970s (Wilson, 1983; Wilson and Pitcher, 1983; Wilson, 1984b; a; Wilson and

Pitcher, 1984a; b; 1985). More recently, Harrod and co-authors have examined the population

ecology, conservation status, reproductive ecology and parasitism of the pollan stock (Harrod, 2001;

Harrod et al., 2001; 2002; Harrod and Griffiths, 2004; 2005a; b). Other studies have examined the



autecology of brown trout (Crozier, 1983), perch (Montgomery, 1990), and roach (Tobin, 1990). The

monograph by Wood and Smith (1993) contained detailed summaries of the studies conducted on

Lough Neagh fishes up to the late 1980s including a first examination of the fishes of Lough Neagh at

a community level (Winfield et al., 1993). Lough Neagh supports the largest freshwater fishery in

the British Isles, and the largest and most important eel fishery in Western Europe (Rosell et al.,

2005). Although commercially important, recent quantitative sampling indicates that the eel is the

third most abundant fish in Lough Neagh (Table 3).

Following the decline of pollan from other Irish lakes (Harrod et al., 2001; Harrod et al., 2002), Lough

Neagh supports the last viable population in Europe, enhancing its conservation status. Although

currently abundant (Table 3), pollan are subject to a range of threats including invasive species,

parasites, unregulated exploitation and climate change (Graham and Harrod, 2009). Like many

fishes, the early life stages are particularly sensitive. Pollan spawn in late November/December over

shallow hard-bottomed areas in the sub-littoral (Dabrowski, 1981; Harrod and Griffiths, 2004),

including areas close to proposed abstraction point (Winfield and Wood, 1988). Pollan require water

temperatures < 5°C before spawning can occur (Dabrowski, 1981), and once spawned, eggs develop

over the winter and hatch in early March. Coregonid eggs are extremely susceptible to siltation of

spawning grounds (Büttiker, 1986).

Lough Neagh is probably most famous for its eels, but apart from some early attempts to assess the

stock and to examine the trophic ecology of eels during the late 1950s and 1960s (Hynes, 1958a; c;

1959; Anon, 1967), there is little relatively little known about the ecology of the eel in the Lough.

AFBI biologists are currently generating the basic biological information required to support the eel

fishery (Rosell et al., 2005). Although eels are in decline throughout their distribution (Dekker et al.,

2003), the Lough Neagh eel population remains relative abundant through stocking by glass eels

from other locations.

Although the pollan population is the principal species of conservation concern, the lough also

supports genetically isolated ecotypes of brown trout, the dollaghan (Crozier, 1983), and an unusual

freshwater-feeding population river lamprey, both of which are of considerable conservation

importance. The fish community has recently undergone considerable shifts with regard to its

structure and recent surveys by Queen’s University, Belfast revealed that the lough is dominated by

roach (Table 3).



Table 3: Relative abundance of Lough Neagh fishes assessed during a lough-wide seine net survey (2006: n hauls = 122).

Species Mean numerical contribution

% (n = 12 589)

Roach (Rutilus rutilus) 41.1

Pollan (Coregonus autumnalis) 35.6

Eel (Anguilla anguilla) 11.1

Perch (Perca fluviatilis) 6.7

Bream (Abramis brama) 1.8

Brown trout (Salmo trutta) 1.4

3-spined stickleback (Gasterosteus aculeatus) 0.8

Gudgeon (Gobio gobio) 1.2

River Lamprey (Lampetra fluviatilis) 0.3

Roach x Bream hybrid 0.1

1.2.2.5 Birds

The bulk of the conservation attention to date has been directed at the lough’s bird community as

with Lough Beg, the lough supports internationally important and extremely abundant populations

of overwintering and resident wildfowl. In recognition of this importance to birdlife, they have been

given statutory protected at an international, European and national level, being designated as a

Ramsar site, a Special Protection Area (SPA) under the European Community’s Birds directive, and an

ASSI. The Lough Neagh and Lough Beg SPA represents the most important site for diving ducks in

Britain and Ireland, hosting overwintering populations of ca. 40 000 pochard (Aythya farina), 30 000

tufted duck (Aythya fuligula), 14 000 goldeneye (Bucephala clangula)and 5 000 scaup (Aythya

marila) during the early 1990s (Bigsby, 2000; Evans, 2000; Maclean et al., 2006). However, since the

early 1990s concern has been raised due to large, and significant declines in the numbers of three of

these species (Allen and Mellon, 2006; Maclean et al., 2006). For instance, over the winter of

2003/04, an estimated 9 000 tufted duck, 8 000 pochard, 4 000 goldeneye and 2 600 scaup

overwintered in the SPA (Maclean et al., 2006). Although scaup numbers have subsequently

recovered, the declines in the other diving ducks were shown by Maclean et al. (2006) to be an order

of magnitude larger than declines recorded from anywhere in Britain or Ireland over the same

period, and were not associated with similar trends anywhere in Europe.

Lough Neagh also provides excellent foraging habitat for large numbers of cormorants

(Phalacrocorax carbo), a predator of pollan, roach and eels (Warke et al., 1994; Brown, 2009). Local

wildfowlers exploit both the migratory wildfowl and the abundant resident population of mallard

(Anas platyrhynchos). Although conservationally important, there have been few studies of the

ecology of the birds of Lough Neagh. Evans (2000) examined diving duck behaviour and ecology,

whilst trophic ecology was examined by both Winfield (1991) and Bigsby (2000).

1.2.2.6 Mammals

Otters (Lutra lutra) are occasionally seen on the shoreline of Lough Neagh, and otter traffic

mortalities have been recorded on roads adjacent to the lough (Harrod Pers. Obs.).



1.2.3 Socio-economic characteristics

1.2.3.1 Cultural heritage

Lough Neagh has played a fundamental role in the history of Ireland (Bardon, 1992). Excavations at

Ireland’s first recorded settlement at Mount Sandel, on the banks of the Lower Bann River,

demonstrated that Mesolithic settlers relied on fishes migrating between the lough and the Atlantic

Ocean via the river (Woodman and Mitchel, 1993). Later in Ireland’s history, native Irish peoples

were displaced to the shores of Lough Neagh during the plantations of English and Scottish settlers

in the 16th and 17th century, and represent the ancestors of today’s fishing community (Donnelly,

1986). After over a century of legal wrangling, the fishing community finally gained control of the

fishery in 1971, and today operates as a co-operative.

1.2.3.2 Fishery

The commercial fishery currently employs ca. 300 people, (Kennedy, 2000); reliable figures regarding

its worth are not available, but it is likely to be in the region of several million pounds a year.

Although the cultural value of fishing is immense and probably undervalued, it also provides much-

needed employment and income in what is one of the European Union’s most deprived regions. The

fishery principally exploits eels, taking immature brown eels from the lough using long lines and

draft nets and mature silver eels are trapped during their downstream migration. The majority of

eels are exported live to Holland. Pollan and other scale-fish also contribute to the fishery, but at a

far reduced annual yield. Rosell et al. (2005) showed that although catches have declined recently,

ca. 500 t of eels are still removed annually. Clearly the long-term sustainable management of eels is

of paramount importance to many Lough Neagh stakeholders and any proposed development

should consider the potential impacts to the eel fishery.

1.2.3.3 Other human uses of Lough Neagh

Large volumes of Lough Neagh water are abstracted daily to supply Belfast and other population

centres (ca. 2 105 m d-1 - (1998), whilst the lough and its afferent rivers receive effluent from STWs.

The sediments of Lough Neagh are also commercially exploited. Sand is extracted from the lough

bed in considerable, but unquantified volumes using large suction dredges mounted on sand barges.

Currently, recreational use of the open water of Lough Neagh is minimal. Some cruising and yachting

takes place, but it is far less developed than in lakes of comparable size elsewhere (e.g. Lough Erne

and Loch Lomond).

1.3 AIMS

This study aimed to provide an assessment of the likely environmental impacts of the construction

and operation of a small-scale water abstraction scheme located on the shore of Lennymore Bay,

Lough Neagh. This report details a rapid assessment of the aquatic ecology Lennymore Bay, that was

conducted to identify any particular sensitivities associated with the location selected for the



proposed abstraction point. The report also provides an assessment of the likely environmental

impacts of abstraction operations on several key taxa.



2. MATERIALS AND METHODS

2.1 FIELD STUDY

This study was designed to provide a rapid assessment of the ecology of Lennymore Bay, and to

identify any particular sensitivities associated with the proposed abstraction of water. Due to the

limited time available, sampling was conducted over two days (25-26 May 2009) at 15 sites located

on a semi-random grid system (Table 1, Fig. 2). This approach aimed to provide a wide-scale

indication of variation in the lough bed, and associated fish, benthic macroinvertebrate and

zooplankton communities of Lennymore bay. These data were then examined statistically in order to

examine differences between sites. These results were considered in the context of whether the

ecology of the area adjacent to the proposed abstraction point was particularly sensitive to the likely

impacts of abstraction.

Table 4: Location and depth of sites sampled as part of the current study. Note that site RE12 was located ca. 150 m offshore of the proposed abstraction point.

Site Irish grid Depth (m)

RE01 IJ 09892 74603 3.0

RE02 IJ 10575 74509 5.0

RE03 IJ 11393 74676 2.7

RE04 IJ 10136 73772 6.5

RE05 IJ 10937 73817 6.5

RE06 IJ 11555 73968 3.6

RE07 IJ 10356 72995 2.5

RE08 IJ 11133 73166 3.4

RE09 IJ 11928 73046 2.9

RE10 IJ 09933 72030 2.7

RE11 IJ 11127 72100 4.2

RE12 IJ 11898 72102 3.5

RE13 IJ 09686 70854 5.1

RE14 IJ 10549 71186 4.2

RE15 IJ 11477 71689 3.1

Figure 2: Schematic map of Lennymore Bay showing location of sampling points (RE01-RE15) and simplified bathymetry. RE12 was located offshore of the proposed abstraction point.

2.1.1 Sampling

With the kind permission of the fishery owner, the Lough Neagh Fishermen's Co-operative Society

Ltd, Toome Bridge, biologists from the School of Biological Sciences, Queen’s University, Belfast

sampled 15 different locations across Lennymore Bay (Table 1, Fig. 2). At each site, surface



temperature (± 0.1°C) and water depth (± 0.1 m) was recorded using a combined hand-held

thermister and depth sounder. Where the lough bed was suitable (i.e. hard substrates such as rock,

cobble or boulders cannot be sampled using this method), a single sample of sediment and

associated benthic macroinvertebrate fauna was collected using an Eckmann grab (area = 225 cm2).

Zooplankton were collected through a single vertical haul of a zooplankton net (250 µm-mesh,

diameter = 0.3 m, length = 0.9 m). Fish were collected through a single haul of a Lough Neagh draft

(seine) net (net dimensions: length = 82.3 m, depth = 4.6 m, mesh in walls = 3.8 cm, mesh in cod-end

= 1.3 cm) operated by a local commercial eel fisherman. Once collected, all samples were placed on

ice and returned to the School of Biological Sciences, Queen’s University Belfast for subsequent

processing.

2.1.2 Sample processing

Sediment samples were passed through 500 µm sieves, and the remaining material was placed into

white trays, where macroinvertebrates were picked out prior to identification. Sediments were

retained for visual description of the dominant sediment characteristics (clay, silt, sand or gravel).

Macroinvertebrates were identified to the lowest practical taxonomic resolution (family to species)

using a binocular microscope and relevant identification keys and enumerated. The density of each

taxon was estimated as n.m2.

Zooplankton samples were fixed in 70% ethanol and allowed to settle overnight in graduated flasks.

The settled volume was estimated volumetrically, and a 1 ml subsample was collected using a wide-

mouthed pipette. From this subsample, individual zooplankton were counted and identified as

cladocerans (e.g. Daphnia hyalina, D. longispina) , cyclopoid (e.g. Cyclops abyssorum, C. vicinus) or

calanoid (e.g. Eudiaptomus gracilis) copepods and enumerated. Using the relative abundance of

zooplankton in each sub-sample relative to the settled volume and the length of the zooplankton

haul at each site, the density of each zooplankton taxon at each site was estimated as n.m-3. The

mean length of twenty individuals of each zooplankton taxon (cladoceran, cyclopoid and calanoid

copepods) was estimated at each site to provide an indication of food resources for

zooplanktivorous fishes (e.g. juvenile pollan and roach).

Fish were identified to species and enumerated. Individual fork length (± 1 mm) and wet mass (±

0.1g) were recorded. Fish community structure at each site was calculated in terms of proportional

contribution to catch by number and biomass. Data were also calculated in terms of as densities

(n.ha-2) and biomass (kg.ha-2) per site. Due to their ecological importance, the abundance and

biomass of pollan and roach were calculated separately for juvenile (≤ 100 mm) and adult (>100

mm) size classes.

2.1.3 Statistical analyses

Statistical analyses included univariate and multivariate approaches. ANOVA of rank-transformed

data (SYSTAT 12.02.00) was used to compare variation in fish and zooplankton size between sites.

Bonferroni-adjusted post-hoc comparisons were used to identify the cases where data from Site

RE12 differed significant from other sites. Fish, macroinvertebrate and zooplankton community



structure was examined between sites using multidimensional scaling (MDS) ordinations and group-

average cluster analysis based on square-root transformed Bray Curtis similarity matrices within

PRIMER 6 (Clarke and Warwick, 2001).

2.2 ASSESSMENT OF ABSTRACTION IMPACTS

The likely impacts of the installation and operation of the proposed abstraction facility on the

aquatic ecology of Lennymore Bay was assessed through consideration of the data generated

through the current survey, existing literature and previous knowledge of the lough’s ecology. The

risk of fish mortality through entrainment into the abstraction pipe was estimated by modelling the

swimming capacity and the abstraction velocity for a series of species (Hoagman, 1974; Sprengel and

Lüchtenberg, 1991; Mann and Bass, 1997).



3. RESULTS

3.1 FIELD STUDY

3.1.1 Zooplankton

The zooplankton community at each site was dominated by cyclopoid copepods (Table 5: mean

density = 7 232, range = 794 – 16 928 ind.m-3), followed by calanoid copepods (mean density = 1

682, range 794 – 5 632 ind.m-3). Cladoceran zooplankton (the preferred prey of juvenile fishes) were

found in extremely low densities (mean = 75, range 0 – 555 ind.m-3).

Table 5: Estimated density of three zooplankton taxa (ind.m-3

) recorded from each sampling site in Lennymore Bay during May 2009.

Site Calanoid Cyclopoid Cladoceran Total

RE01 173 245 26 444

RE02 1 962 8 659 555 11 176

RE03 1 437 3 355 125 4 917

RE04 5 632 16 773 35 22 440

RE05 838 9 572 0 10 410

RE06 1 646 11 630 63 13 382

RE07 614 794 0 1 408

RE08 2 744 7 165 0 9 909

RE09 607 4 871 0 5 478

RE10 2 691 6 696 102 9501

RE11 880 10 317 24 11 220

RE12 1 512 5 260 32 6 804

RE13 665 2519 0 3 184

RE14 2 976 16 928 31 19 936

RE15 865 3 703 127 4 706

Mean

(± SD)

1 682

(1 394)

7 232

(5 149)

75

(140)

8 994

(6 263)

Multivariate comparisons of zooplankton community structure using MDS (Fig. 3A) and cluster

analysis (Fig. 3B) indicated some considerable differences between the sites at the time of sampling.

However, the site located adjacent to the proposed extraction point (RE12) was broadly similar to

the bulk of the sites (e.g. > 70% similar to all but RE01 and RE07).



Figure 3: A) Multidimensional ordinations (MDS) of zooplankton community structure at various sites from Lennymore Bay, Lough Neagh. Each point represents a single vertical haul, and in the MDS ordination proximity represents increased similarity. A stress value <0.2 represents a useful two-dimensional representation of the data (Clarke & Gorley, 2006). B) Dendogram based on group average cluster analysis of Bray-Cutis similarities. Both figures indicate that in terms of the structure and abundance of the zooplankton community, RE12 (marked in red) was largely similar (> 60% similarity) with most sites at the time of sampling.

Due to the association between zooplankton size and the availability of suitable food for larval and

juvenile fishes, mean zooplankton size was compared between sites for the zooplankton taxa using

ANOVA of ranked data (Fig. 4). In all taxa, mean length differed between sites (Calanoid: F14, 285 =

7.84, P < 0.0001; Cyclopoid: F14,283 = 3.33, P < 0.0001; Cladoceran: F13, 145 = 4.28, P < 0.0001).

Zooplankton from RE12 were relatively small-bodied compared to other sites, and post-hoc

comparisons indicated that in several cases this difference was significant (see sites marked with * in

Fig. 4). There was no correlation with the relative abundance of juvenile (≤ 100 mm) fishes and the

mean size of zooplankton collected at the various sites (Spearman’s rank: all rs <0.16, n = 14, P > 0.6).



Figure 4: Variation in mean (± 95% CI) zooplankton length recorded from the 15 sampling sites in Lennymore Bay. Site RE12 (located adjacent to the proposed abstraction point) is highlighted in red to aid comparisons. Sites marked with an asterisk are significantly different from values recorded from RE12. Statistics shown here are based on raw data, whilst statistical comparisons were conducted by ANOVA on rank-transformed data.

3.1.2 Benthic macroinvertebrates

Sediments at two sites (RE01 and RE12) were unsuitable for use of an Ekman Grab, hence no

macroinvertebrates were collected, even after repeated attempts. As noted previously (Carter,

1993b; Bigsby, 2000; McKenna et al., 2008), all the areas of Lennymore Bay successfully sampled by

grab sampling, were dominated by sand and other ‘hard’ sediments (Table 6). As such, the density of

macroinvertebrates were markedly reduced, i.e. by two orders of magnitude in some cases, relative

(Table 6) to those reported from the lough’s softer profundal sediments (Carter and Murphy, 1993;

Bigsby, 2000). The sampling period also coincided with an chironomid emergence event (Carter,

1975), which may have further depressed the number of individuals recorded from each grab. Note

that alternative sampling techniques may have recorded macroinvertebrates at RE01 and RE12.



Table 6: Dominant sediment recorded from grab samples and variation in density (n.m-2

) of different macroinvertebrate taxa recorded from each of the sampling sites in May 2009. Note that due to the hard nature of the substrate (i.e. pebbles, cobbles, boulders or bedrock), benthic macroinvertebrates could not be sampled at two sites: RE01 and RE12 (-).

Site Do

min

ant

sed

ime

nt

Ch

iro

no

mid

ae la

rvae

Ch

iro

no

mid

ae p

up

ae

Olig

och

aeta

e

Hyd

rid

ae

Ce

rato

po

gon

iidae

Gam

mar

idae

Cae

nid

ae

Tric

lad

s

Hyd

rob

iidae

RE01 ? - - - - - - - - -

RE02 Sand 133.3 8.9 22.2 0.0 4.4 0.0 0.0 0.0 8.9

RE03 Rock/Sand 0.0 0.0 128.9 0.0 4.4 0.0 0.0 0.0 0.0

RE04 Gravel 8.9 0.0 0.0 0.0 0.0 0.0 0.0 4.4 0.0

RE05 Gravel 13.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

RE06 Sand 26.7 0.0 48.9 0.0 0.0 0.0 0.0 0.0 13.3

RE07 Sand/silt 102.2 8.9 142.2 4.4 4.4 4.4 35.6 0.0 0.0

RE08 Sand 0.0 0.0 44.4 0.0 0.0 0.0 0.0 0.0 0.0

RE09 Sand/silt 17.8 8.9 0.0 0.0 0.0 4.4 4.4 0.0 0.0

RE10 Sand/silt 13.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.4

RE11 Sand/silt 0.0 0.0 22.2 4.4 0.0 0.0 0.0 0.0 0.0

RE12 ? - - - - - - - - -

RE13 Sand 22.2 4.4 137.8 0.0 4.4 0.0 0.0 0.0 0.0

RE14 Sand/Gravel 0.0 0.0 35.6 0.0 4.4 0.0 0.0 0.0 0.0

RE15 Sand/silt 71.1 0.0 4.4 0.0 22.2 0.0 0.0 0.0 0.0

Mean 31.5 2.4 45.1 0.7 3.4 0.7 3.1 0.3 2.1

(± SD) (43.2) (3.9) (54.8) (1.7) (6.1) (1.7) (9.8) (1.2) (4.3)

Multivariate comparisons (Fig. 5 A&B) indicated that at the time of sampling, there was considerable

spatial variation in macroinvertebrate community structure at the different sites. As noted above, it

was impossible to sample at RE01 and RE12 due to the substrate, precluding any comments on the

macroinvertebrate community at RE12.



Figure 5: A) MDS ordination and B) cluster analysis of benthic macroinvertebrate data collected at sites within Lennymore Bay. Note that no macroinvertebrates were collected from either site RE01 or RE12 due to the nature of the substrate.

3.1.3 Fish community structure

Total survey catch included 833 individual fish from a total of 8 species. Assuming a positive linear

relationship between abundance and catch per unit effort, at the time of sampling, the Lennymore

Bay fish community was dominated (Tables 7 and 8) by roach (58%), followed by pollan (34%) and

bream (5%). Other species were captured (brown trout, perch, gudgeon, three-spined stickleback)

but made a restricted contribution to the survey catch. A notable absence from the survey catch was

eel: no eels were captured over the entire survey. This was unusual, as according to local fishermen

eels were captured by long-line fishermen across Lennymore Bay at the time of sampling.

Table 7: Abundance of different fish species in each sample,

Site 3 Spined

stickleback Bream Brown trout Gudgeon Perch Pollan Roach Salmon

Total catch

RE01 0 0 1 0 0 2 206 0 209 RE02 0 18 0 0 0 4 2 0 24 RE03 0 18 0 4 8 20 164 0 214 RE04 0 0 0 0 0 9 0 0 9 RE05 0 0 0 0 0 9 2 0 11 RE06 1 0 2 0 0 21 8 0 32 RE07 0 0 0 0 0 28 2 0 30 RE08 0 0 0 0 0 123 1 0 124 RE09 1 0 0 0 0 49 5 0 55 RE10 0 0 0 0 1 6 4 0 11 RE11 0 8 0 0 0 3 40 0 51 RE12 0 0 1 0 0 5 9 0 15 RE13 1 0 0 0 0 2 33 0 36 RE14 0 0 0 0 0 1 2 0 3 RE15 0 0 0 0 2 1 5 1 9

Mean 0.2 2.9 0.3 0.3 0.7 18.9 32.2 0.1 55.5 (± SD) (0.4) (6.5) (0.6) (1.0) (2.1) (31.7) (63.6) (0.3) (70)



Table 8: Estimated abundance of fishes expressed in terms of individuals.ha-1

.

Site

3 Spined

stickleback Bream Brown trout Gudgeon Perch Pollan Roach Salmon Sum

RE01 0 0 1.9 0 0 3.8 387.3 0 393

RE02 0 33.8 0 0 0 7.5 3.8 0 45

RE03 0 33.8 0 7.5 15.0 37.6 308.3 0 402

RE04 0 0 0 0 0 16.9 0 0 17

RE05 0 0 0 0 0 16.9 3.8 0 21

RE06 1.9 0 3.8 0 0 39.5 15.0 0 60

RE07 0 0 0 0 0 52.6 3.8 0 56

RE08 0 0 0 0 0 231.2 1.9 0 233

RE09 1.9 0 0 0 0 92.1 9.4 0 103

RE10 0 0 0 0 1.9 11.3 7.5 0 21

RE11 0 15.0 0 0 0 5.6 75.2 0 96

RE12 0 0 1.9 0 0 9.4 16.9 0 28

RE13 1.9 0 0 0 0 3.8 62.0 0 68

RE14 0 0 0 0 0 1.9 3.8 0 6

RE15 0 0 0 0 3.8 1.9 9.4 1.9 17

Mean 0.4 5.5 0.5 0.5 1.4 35.5 60.5 0.1 104.4

(± SD) (0.8) (12.1) (1.1) (1.9) (3.9) (59.6) (119.6) (0.5) (131.7)

Fish community structure was analysed using multivariate statistics (Fig. 9) and indicated that at the

time of sampling there was some structuring in the fish community between the different sample

sites. The catch at RE12 was limited, with a total of 15 individuals of three species. However, in

terms of community structure based on abundance, it was broadly similar with several sites,

especially RE10.

Figure 6: A) MDS ordination and B) cluster analysis of fish abundance data collected at sites within Lennymore Bay. These figures indicate that there was some variation in fish community structure at each site at the time of sampling. In terms of the abundance of the species collected at the different sites, RE12 appears broadly similar to other sites.

Tables 9 and 10 detail the survey catch in terms of biomass per haul and biomass per ha. Again,

roach dominated the survey catch, contributing 56% to the total survey catch. Pollan contributed



29% by biomass, whilst bream contributed 9%. Although only 4 brown trout were captured, they

contributed 6% to the total catch, due to their large individual size (max. mass = 1 250 g).

Table 9: Biomass of fishes captured at each site (g).

Site

3 Spined

stickleback Bream Brown trout Gudgeon Perch Pollan Roach Salmon Sum

RE01 0 0 315 0 0 133 8 002 0 8 450

RE02 0 628 0 0 0 163 32 0 823

RE03 0 1 553 0 53 122 1 465 3 233 0 6 427

RE04 0 0 0 0 0 506 0 0 506

RE05 0 0 0 0 0 701 62 0 763

RE06 4 0 123 0 0 1 154 287 0 1 567

RE07 0 0 0 0 0 3 012 244 0 3 256

RE08 0 0 0 0 0 63 68 0 130

RE09 2 0 0 0 0 407 137 0 546

RE10 0 0 0 0 117 121 201 0 438

RE11 0 259 0 0 0 118 1 428 0 1 805

RE12 0 0 1 250 0 0 45 109 0 1 404

RE13 2 0 0 0 0 140 1 695 0 1 837

RE14 0 0 0 0 0 52 64 0 116

RE15 0 0 0 0 3.6 99 324 38 464

Mean 1 163 113 4 16 545 1 059 3 1 902

(± SD) (1) (421) (326) (14) (42) (807) (2 120) (10) (2 425)

Table 10: Biomass of fishes captured at each site shown as kg.ha-1.

Site

3 Spined

stickleback Bream

Brown

trout Gudgeon Perch Pollan Roach Salmon Sum

RE01 0 0 0.6 0 0 0.2 15.0 0 15.9

RE02 0 1.2 0 0 0 0.3 0.1 0 1.5

RE03 0 2.9 0 0.1 0.2 2.8 6.1 0 12.1

RE04 0 0 0 0 0 1.0 0.0 0 1.0

RE05 0 0 0 0 0 1.3 0.1 0 1.4

RE06 0.007 0 0.2 0 0 2.2 0.5 0 2.9

RE07 0 0 0 0 0 5.7 0.5 0 6.1

RE08 0 0 0 0 0 0.1 0.1 0 0.2

RE09 0.004 0 0 0 0 0.8 0.3 0 1.0

RE10 0 0 0 0 0.2 0.2 0.4 0 0.8

RE11 0 0.5 0 0 0 0.2 2.7 0 3.4

RE12 0 0 2.3 0 0 0.1 0.2 0 2.6

RE13 0.004 0 0 0 0 0.3 3.2 0 3.5

RE14 0 0 0 0 0 0.1 0.1 0 0.2

RE15 0 0 0 0 0 0.2 0.6 0.1 0.9

Mean 0.001 0.31 0.21 0.01 0.03 1.03 2 0.01 3.6

(± SD) (0.002) (0.79) (0.61) (0.03) (0.08) (1.52) (4) (0.02) (4.6)

The survey catch included relatively large numbers (Table 11) of juvenile (≤ 100 mm) pollan (21%)

and roach (15%), indicating that certain areas of Lennymore Bay (see RE03, RE08 and RE09) may act



as a nursery area. Although the total catch at RE12 was low, it was dominated in terms of abundance

by juvenile pollan and roach.

Table 11: Contribution to total survey catch by juvenile (< 100 mm) roach and perch.

Abundance

(n)

Biomass

(g)

Site

Pollan

≤ 100 mm

Roach

≤ 100 mm

Total survey

catch

Pollan

≤ 100 mm

Roach

≤ 100 mm

Total survey

catch

RE01 0 0 209 0 0 8449.6

RE02 0 1 24 0 1.6 823.3

RE03 0 101 214 0 191.8 6426.5

RE04 0 0 9 0 0 505.5

RE05 0 0 11 0 0 763.3

RE06 2 1 32 1.3 2.1 1566.9

RE07 2 0 30 3.4 0 3256.2

RE08 123 0 124 62.6 0 130.2

RE09 44 4 55 16.3 8.7 546.2

RE10 4 0 11 1.3 0 437.9

RE11 0 3 51 0 4.6 1805.2

RE12 4 6 15 1.3 5.4 1404.3

RE13 0 3 36 0 3.1 1836.9

RE14 0 0 3 0 0 116

RE15 0 2 9 0 13.8 464.2

Multivariate analysis (Figure 7) of survey catches in terms of mass provided more evidence of spatial

structuring within the Lennymore Bay fish community at the time of sampling. Sites RE08 and RE12

were least similar (40% similar) to all the others sites sampled. These were both sites that were

dominated by small-bodied individuals (Table 11).

Figure 7: A) MDS ordination and B) cluster analysis of fish biomass data collected at sites within Lennymore Bay. Note that the community structure of RE12 estimated in terms of biomass appears dissimilar from the other sites.



3.1.4 Fish population structure

3.1.4.1 Pollan

Fork length of pollan varied between 28 and 262 mm (Fig. 8A). Large numbers of fish smaller than 50

mm were captured, indicating recent successful reproduction. As pollan typically reach a mean

length of ca. 140 mm in their first summer of life, these small pollan will have hatched in March 2009

and can therefore be considered young of the year (YOY). Median fork length varied significantly

between sites (Fig 8.B: Kruskal-Wallis test H = 181.8, d.f. = 14, P < 0.001). Individual pollan mass

varied between 0.2 and 202.4 g. Median mass varied significantly between sites (Kruskal-Wallis test

H = 188.4, d.f. = 14, P < 0.001). Several sites (RE08, Re09, RE10 and RE12) were dominated by YOY

pollan (Fig. 8B), indicating that these areas may be nursery areas.

Figure 8: A) Frequency histogram showing size structure (fork length) of pollan captured during May 2009. Dashed lines show mean length at age for pollan as estimated by Harrod (2001). Note the large numbers of small (<50 mm) bodied 0+ pollan. B) Box-whisker plot showing variation in median (± interquartile range) pollan size captured at each of the 15 sampling locations. Note the small average size of individuals captured at sites RE08-10 and RE12, indicating that at the time of sampling that these areas were used by young of the year individuals.

3.1.4.2 Roach

Fork length of roach varied between 39 and 235 mm (Fig. 9A), with a large contribution by juvenile

individuals. Median fork length varied significantly between sites (Fig 9.B: Kruskal-Wallis test H =

103.7, d.f. = 13, P < 0.001). Individual roach mass varied between 0.6 and 235.4 g. Median mass

varied significantly between sites (Kruskal-Wallis test H = 104.3, d.f. = 13, P < 0.001).



Figure 9: A) Frequency histogram showing size structure (fork length) of roach captured during May 2009. Dashed lines show mean length at age for Lough Neagh roach as estimated by Tobin (1990). Note the large numbers of small (<100 mm) bodied roach. B) Box-whisker plot showing variation in median (± interquartile range) roach size captured at each of the 15 sampling locations. Note that no roach were captured at site RE04.

3.1.4.3 Bream

Bream were only captured at three sites (RE02, RE03 and RE11). All bream captured were relatively

small (Fig 10, range: length = 106-308 mm, mass = 13.2 – 549.8 g). Statistical comparisons indicated

that bream size differed between these sites (length: H = 10.2, d.f. = 2, P = 0.006; mass: H = 12.0, d.f.

= 2, P = 0.002). Although growth data are not available for Lough Neagh bream, Fig. 10 indicates that

they have recently successfully reproduced due to the large contribution of relatively small bodied

individuals.

Figure 10: Frequency histogram showing size structure of bream captured in Lennymore Bay during May 2009.



3.1.4.4 Brown Trout

Only four brown trout were captured during the current study from 3 sites: RE01, RE06 and RE12.

This clearly precludes any detailed analyses. Brown trout fork length varied between 160-445 mm,

and mass between 57.3 – 1250 g. The large bodied trout captured at site RE12 was associated with

small pollan and roach, and raised the possibility that it was piscivorous. However, examination of its

stomach contents revealed that prior to capture it had been feeding on chironomid pupae.

3.1.4.5 Three spined sticklebacks

A total of three sticklebacks were captured, ranging in length between 56 and 66 mm. The largest

individual was a gravid female, with a notable large mass of 3.5 g.

3.1.4.6 Gudgeon

Four gudgeon were captured, all from a single site RE03. They ranged in fork length between 78 and

120 mm, and in mass between 5.9 and 22.8 mm.

3.1.4.7 Perch

The survey catch included 11 perch, with 8 captured at RE03, a single individual at RE10 and two

individuals at site RE15. Perch size ranged between 47 and 156 mm (fork length) and 1.4 and 56.6 g

(mass).

3.1.4.8 Salmon

A single salmon smolt (142 mm, 37.8 g) was captured at RE15.

3.2 ECOLOGICAL EFFECTS OF ABSTRACTION

3.2.1 Installation of the abstraction facility

The construction of the proposed abstraction facility will involve the evacuation of existing material,

e.g. soil, and the use of potential contaminants such as fuels and cement. As such, there is the risk of

contamination of littoral areas of the lough e.g. through suspended solids entering Lough Neagh,

which could have a detrimental effect on water quality. The shallow littoral areas located offshore

of the proposed abstraction facility are likely to support pollan spawning grounds, and as such are

sensitive to any increased sedimentation in this area (Auld and Schubel, 1978; Fudge and Bodaly,

1984). Pollan spawn in late November to mid December, and eggs develop on the spawning grounds

from this period until the following March. Hence, any construction should take place outside this

sensitive period.



3.2.2 Impacts during the operation of the abstraction facility

The literature describes a series of environmental impacts of water abstraction, including the uptake

of larval and juvenile fishes in abstracted water, a process known as entrainment (Dempsey, 1988).

In order to estimate the probability of entrainment information is required regarding the volume of

water abstracted, its flow rate, the density and swimming capacity of any susceptible fishes in the

abstraction area.

Although they represent a very important component of the lough fish community for commercial,

ecological and conservation purposes, eels > 130 mm should be able to swim faster than the velocity

(0.28m.s-1) in the proposed abstraction pipe, even if heavily infected with Anguillicola crassus

(Sprengel and Lüchtenberg, 1991). Furthermore, due to the benthic nature of all sizes of eels found

in Lough Neagh, it is unlikely that eels will become entrained, and they should not be impacted by

the abstraction of water.

In order to examine the likely consequences of entrainment on the fishes of Lough Neagh, we

concentrated on two species that are abundant in Lough Neagh: pollan and roach. The Lough Neagh

pollan population is internationally important (Harrod et al., 2001; Harrod et al., 2002) and their

presence in Lough Neagh supports the Lough’s designation as a Ramsar site (JNCC, 2008). Pollan are

subject to a range of threats including possible competition from roach, eutrophication, parasitism

(Harrod et al., 2001; Harrod et al., 2002; Harrod and Griffiths, 2005a), climate change (Graham and

Harrod, 2009) and predation (Brown, 2009). The capture of large numbers of young-of-the-year

pollan in several sites (RE08, RE09, RE10 and RE12) during the current study indicates that

Lennymore Bay supports important nursery grounds for this threatened species. Pollan spawn on

hard-bottomed areas, (Dabrowski, 1981; Harrod and Griffiths, 2004), and have been previously

shown to spawn at a site located ca. 500 m to the north of the proposed abstraction point (Winfield

& Wood, 1988: Irish Grid: J121 726). Discussion with local fishermen also highlighted the importance

of the hard-bottomed areas in Lennymore Bay for pollan spawning, including the areas around site

RE12 and directly offshore from the proposed abstraction point. Larval pollan typically hatch in

March at a length of ca. 10 mm (Dabrowski, 1981; Harrod, 2001), growing to a size of ca. 140 mm in

their first summer of life (Harrod, 2001). Coregonid larvae are planktonic during the first weeks of

life (Hoagman, 1974; Dabrowski, 1981; Harrod, 2001). As such, they often aggregate along lake

shores, including in Lough Neagh, where they can be observed ca. 2 -3 days after hatching. The only

quantitative assessment of pollan larval densities was conducted by Dabrowski, who estimated

median (± interquartile range) larval density as 0.15 (0.034-0.32) individuals.m-3.

Although roach only invaded the Lough Neagh catchment in the early 1970s (Cragg-Hine, 1973), they

are extremely numerous in the lough and currently dominate the fish community (Section X.X). As

such they are likely to be at an elevated risk of entrainment. Pinder (2001) estimated the larval size

range of roach as 6.5 to 17 mm. There are no reliable data on roach larval densities in Lough Neagh.

However, estimates of roach larval densities vary between 0.26-1.14 individuals.m-2 (Mehner and

Thiel, 1999; Persson et al., 2000), with a median (IQR) of 0.64 (0.31-1.1). Large numbers of small-

bodied post-larval roach (sized 20 – 50 mm) are present in shallow littoral areas and fishing quays

throughout the summer (Griffiths and Kirkwood, 1995).



The probability of entrainment of larval roach and pollan was calculated using various assumptions.

Using a pipe diameter of 0.45 m, with an abstraction rate of 160m2.h-1, this reflects an abstraction

velocity of 0.28 m.s-1. The likelihood of fish being taken into the abstraction pipe (known as

entrainment) is a function of their swimming capacity, their size and water temperature. The actual

impact of water abstraction activities reflects the density of susceptible larvae in the area adjacent

to the abstraction and the volume of water removed.

The swimming capacity of roach was estimated through multiple regression to estimate critical

water velocities (the water velocity at which 50% of individuals are displaced) from Mann and Bass

(1997). Here, critical water velocity = -14.06 + 13.8TL + 0.69T, where T = water temperature (°C) and

TL = larval total length (mm). Critical water velocities were modelled for a range of roach larval sizes

(6-17 mm) and water temperatures (6-18°C).

No similar data are available to estimate the critical water velocity for pollan or any other coregonid

fish. However, Hoagman (1974) provided information on the effects of larval size and water

temperature on the burst swimming speed of a congeneric species of pollan (Coregonus

clupeaformis). Using data in Hoagman (1974), multiple regression was used to estimated pollan

burst swimming velocity (cm.s-1) as -7.217 +0.676T+0.669TL, where T = water temperature (°C) and

TL = larval total length (mm). Critical water velocities were modelled for a range of sizes (10-30 mm)

and water temperatures (6-12°C) potentially encountered by pollan larvae.

The results of the modelling indicate that both roach (Fig. 11A) and pollan (Fig. 11B) are susceptible

to entrainment throughout their larval life stage. Below, the possible ecological impacts of

abstraction activities are estimated.

Figure 11: Variation in estimated maximal swimming capacity in roach (A) and pollan (B) larvae at a range of larval sizes and water temperatures. The surface shown in A) is based on a model of critical water velocity (m.s

-1) for roach larvae produced by Mann & Bass (1997) where critical water velocity is the velocity at

which 50% of individuals are displaced. The surface shown in B) is based on the estimated burst swimming capacity in a congener of pollan (Coregonus clupeaformis) described by Hoagman (1974). Note that although the swimming capacity of both larval species increases with individual size and water temperature, it appears that under these conditions larvae would be unable to escape from the abstraction stream (velocity 28 cm.s

-1).



In an attempt to assess the environmental impact of water abstraction, previous workers have

attempted to estimate the number of adult equivalents required to replace those individuals lost to

the population through abstraction (Dempsey, 1988; Turnpenny, 1988). This approach requires a

reliable estimate of mortality rates, which are not available for Lough Neagh fishes. An alternative,

less robust approach is to use estimates of fecundity to predict the number of spawning females

required to produce the individuals lost due to abstraction. Fish fecundity is typically high (Harrod

and Griffiths, 2004; Lappalainen et al., 2008) and large numbers of larvae can be produced by

relatively few females. However, it must be remembered that larval mortality is extremely high.

During the period 1998-1999, pollan larvae were recorded from shallow littoral habitats in the

North-West of Lough Neagh for ca. 2-4 weeks post-hatching (Harrod, pers. obs.). The location of the

proposed abstraction point is on the eastern shore, where due to the prevailing south-westerly wind

(Carter, 1993a), pollan may be found inshore for longer periods. The velocity of the proposed

abstraction stream is probably greater than that of the burst swimming speed of pollan throughout

their larval period (Fig.11B). Hence, there is a risk that pollan larvae could be potentially taken into

the abstraction pipe. As noted above, Dabrowski (1981) estimated median (±IQR) densities of pollan

larvae as 0.15 ±0.286 individuals.m-3. With an estimated abstraction rate of 26 880 m3.week-1, the

median (± IQR) weekly mortality rate can be estimated as 4005 ±7688 pollan larvae per week.

Harrod & Griffiths (2004) estimated mean (±SE) absolute fecundity in pollan as 8377 ± 221 eggs per

female, suggesting that the median (± IQR) weekly loss of pollan larvae is equivalent to the

reproductive output of 0.48 (0.1-1.0) females. Note that this does not take into account other larval

mortality factors.

There are no reliable data on roach larval densities in Lough Neagh. However, estimates of roach

larval densities vary between 0.26-1.14 individuals.m-2 (Mehner and Thiel, 1999; Persson et al.,

2000), with a median (IQR) of 0.64 (0.31-1.1). Assuming that roach larvae are distributed equally

throughout the water column, the median (IQR) mortality rate can be estimated as 17 284 (8 333-29

568) roach larvae per week. Although Lough Neagh roach were studied by Tobin (1990), her

estimates of fecundity were based on a very small (n = 7) sample size. Therefore, using a fecundity-

size relationship developed from a recent meta-analysis (Lappalainen et al., 2008) and a reliable

estimate of mean adult spawning size (mean length = 154 mm) from spawning roach sampled in the

Glenavy River (Harrod 2009) mean absolute fecundity was estimated at 63 660 eggs per female. This

indicates that the median (± IQR) estimated weekly loss of roach larvae to abstraction is equivalent

to the annual reproductive output of 0.27 (0.13 - 0.46) females before other mortality factors are

considered.

Three spined sticklebacks commonly spawn in fishing quays similar to the area selected for the

proposed abstraction point (Harrod, pers. obs.). It is not known whether other species, e.g. perch or

gudgeon spawn in these areas, but clearly there is the scope for entrainment of other fishes than

pollan or roach.

Entrainment can be minimised through effective screening and design of the abstraction pipe

(Turnpenny, 1981). Turnpenny (1981) presented formulae by which optimal mesh sizes can be

calculated for different sizes and shapes of fishes. This is a relatively simple exercise, but requires

data on the morphology of larval and juvenile fishes, which were not available at the time of writing.



3.2.3 Entrainment of other taxa.

Lough Neagh supports abundant populations of several planktonic invertebrate taxa, including a

declining (Griffiths, 2007) but conservationally important (JNCC, 2008) population of Mysis relicta

and various zooplankton species that may be subject to entrainment. Mysis are rarely encountered

in the shallow littoral of Lough Neagh (Andrew and Woodward, 1993; Bigsby, 2000) and as such are

unlikely to be taken into the abstraction stream. Smaller-bodied zooplankton (e.g. Daphnia spp. and

copepods) are present in extremely large densities during some periods of the year (Fitzsimons and

Andrew, 1993), and are very likely to be drawn into the abstraction system. However, zooplankton

densities in the lough are often high (op. cit.) and as such the impact of the proposed abstraction

system is likely to be minor.

One component of the zooplankton community that could have significant impact on operation of

the abstraction facility is the zebra mussel (Sprung, 1993). This invasive bivalve has recently invaded

Lough Neagh and although originally restricted to Kinnegoe were recently recorded by commercial

fishermen from Bartin’s Bay, ca. 7.5 km south-west of the proposed abstraction point (Dr Derek

Evans, AFBI, Pers. com.).Following spawning, larval zebra mussels have a short (1 – 5 week)

planktivorous life stage. In well mixed water columns such as those found in Lough Neagh (mean

annual wind-speed 5 m.s-1), veligers will typically be distributed throughout the water column

(Fraleigh et al., 1993). Following this period, the veligers can settle in immense densities (16 000 –

270 000 indivuduals.m-2)(Jenner and Janssen-Mommen, 1993; Leach, 1993). Zebra mussels

preferably settle on hard substrates (Kilgour and Mackie, 1993; Leach, 1993) and water intake pipes

can provide ideal substrates at they not only provide suitable settlement substrates with low

predation risk, whilst the water flow provides a continual source of food (Klerks et al., 1993).

Once settled in water intake systems, fouling by zebra mussels can and has caused significant

impacts on operations at waterworks, power stations and other large-scale abstracters of water in

Europe and North America e.g. by restricting flow, clogging screens, and preventing valves from

operating (Kovalak et al., 1993; LePage, 1993). Once attached, zebra mussels can be controlled

through a range of measures including mechanical cleaning (Kovalak et al., 1993), chlorination

(LePage, 1993), or other chemical treatments (Klerks et al., 1993). Jenner and Janssen-Mommen

(1993) suggested that the settlement of veligers in water abstraction systems can be controlled

through the installation of fine-meshed (100 µm) screens. The feasibility of using such fine-meshed

barriers in Lough Neagh is questionable, due to the risk of clogging.



4. CONCLUSIONS

This study has examined the likely sensitivity several component of the aquatic ecology of

Lennymore Bay, Lough Neagh to the proposed small-scale abstraction Lennymore Bay as part of a

proposed development of a biomass-fuelled power plant near Glenavy, Co. Antrim. The developers

have proposed the construction and operation of a small-scale abstraction of cooling water from a

site located on the shore of Lough Neagh (Lennymore Bay).

The School of Biological Sciences, Queen’s University, Belfast were commissioned to conduct an

assessment of the likely sensitivity of this area of Lough Neagh in terms of the construction and

operation of the proposed abstraction plant. The assessment involved a combined field and desk-

based approach. The field component involved a rapid assessment of the current status of several

important components of the aquatic ecology of Lennymore Bay. Fish, zooplankton and benthic

macroinvertebrates were surveyed at 15 sites located on a semi-random grid, including one site

located close to the location of the abstraction plant.

At the time of sampling, zooplankton densities ranged between 444 and 22 440 individuals.m-3 at

the fifteen sites sampled. The zooplankton community was dominated by cyclopoid copepods,

followed by calanoid copepods. Cladoceran zooplankton were found in extremely low densities.

Comparison of average zooplankton size indicated that zooplankton at several sites were reduced in

size, including the site located close to the proposed abstraction, possibly indicating the effects of

fish predation. Multivariate analysis of spatial structuring within the zooplankton community

indicated that the site adjacent to the proposed abstraction plant was generally similar (>70%) to all

but two of the other sites surveyed.

The sediments of Lennymore Bay largely consist of sand and other hard substrates, and as such are

difficult to sample in order to assess benthic macroinvertebrate community structure. Ekman grab

sampling revealed that the abundance and diversity of macroinvertebrates was generally low at the

survey sites. At two sites, it was impossible to actually sample benthic macroinvertebrates due to

the nature of the substrate, including the site adjacent to the proposed abstraction.

Results indicated that Lennymore Bay supports a diverse and abundant fish community, dominated

by roach and pollan, with lesser contributions by bream, brown trout, gudgeon, perch, three-spined

sticklebacks and Atlantic salmon. Unusually, no European eels were captured during the two day

survey, even though local fishermen recorded their capture using an alternative gear (long-lines).

Univariate and multivariate statistical analyses showed evidence of spatial structuring within the fish

community, with several sites supporting significant populations of juvenile pollan and roach,

including the site adjacent to the proposed abstraction plant.

Using the information gathered during sampling in May 2009, previous data gathered by the author

and colleagues, and information from the scientific literature the likely ecological impacts of the

construction and operation of the abstraction facility on fish and other aquatic taxa were estimated.

Our results indicate that that several areas of Lennymore bay, including an area offshore of the



proposed abstraction site represent nursery areas for juvenile fish, including pollan. The littoral area

adjacent to the proposed abstraction site supports putative pollan spawning habitats.

Construction of the abstraction facility is likely to have minimal impact on the aquatic ecology,

assuming that inputs of contaminants and suspended solids are minimised and construction is timed

to avoid periods of pollan spawning and egg incubation.

In order to estimate the risk of entrainment, the swimming capacity of eel, pollan and roach was

compared with the velocity of the water drawn into the abstraction plant. Eels > 130 mm are

unlikely to be at risk of entrainment due to their swimming capacity. The benthic nature of eels of all

sizes will further limit the likelihood of entrainment of this economically and conservationally

important species. However, the poor swimming capacity of larval pollan and roach indicates that if

present in the abstraction area, these species are at risk of entrainment. Without knowledge on the

actual abundance of fish susceptible to entrainment in abstraction area it is difficult to comment on

the likely ecological impact. Using likely densities from the literature, it appears that the numbers of

larval fish lost to abstraction are likely to be relatively minor. It should be noted that the risk of fish

entrainment can be minimised by design, including the installation of a suitable mesh cover on the

abstraction pipe.

The risk to abstraction operations associated with the entrainment and possible settlement of zebra

mussels (Dreissena polymorpha) are significant and should be considered by the developers.



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