Review and ConclusionsReview and Conclusions

D. RobertsD. RobertsQueen’s University, BelfastQueen’s University, Belfast

Since the appearance of humans Strangford Lough has Since the appearance of humans Strangford Lough has been exploited by them – first, in prehistoric periods, by been exploited by them – first, in prehistoric periods, by hunter-gatherers then by farmershunter-gatherers then by farmers

Because population density was low, early exploitation Because population density was low, early exploitation was probably sustainable although the landscape started was probably sustainable although the landscape started to change as a result of agricultureto change as a result of agriculture

In Medieval times exploitation increased and this In Medieval times exploitation increased and this continued into post-medieval and recent times with continued into post-medieval and recent times with increasing exploitation for food, minerals, recreation and increasing exploitation for food, minerals, recreation and waste disposal and agricultural intensificationwaste disposal and agricultural intensification

The most recent changes i.e. changes in benthic and The most recent changes i.e. changes in benthic and intertidal communities, as we have heard, led to the intertidal communities, as we have heard, led to the present study which was charged with trying to identify present study which was charged with trying to identify probable causesprobable causes

A number of changes have been documented over A number of changes have been documented over the last 40-50 years and their causes and the last 40-50 years and their causes and consequences suggested consequences suggested

The presentation is in two parts:The presentation is in two parts:

review longer historical perspectivereview longer historical perspective

review of present study [SLECI]review of present study [SLECI]

PERIODPERIOD Molluscs Molluscs oysters, oysters, limpets, limpets, cockles, cockles, winkles, winkles, whelkswhelks

CRUSTACEA CRUSTACEA crabs, lobster, crabs, lobster, prawns prawns

FinfishFinfish

Herring, Herring, salmon, salmon, whitefishwhitefish

SeaweedSeaweed

Dulse, Dulse, LaminariaLaminaria, , fucoids fucoids

Habitat/ Habitat/ species species changeschanges

PrehistoricPrehistoric

10,000-1,600 10,000-1,600 BPBP

MediaevalMediaeval

1,600-400 BP1,600-400 BP

Post- medievalPost- medieval

1717thth C C

1818thth C C

1919thth C C

Fish traps

ND ND Fish traps

ND

oyster fishery ND ND ND ND

oyster fishery

ND herringseaweed industry

seaweed grids

oysters decline

ND herring decline

seaweed collapse

minimalMiddenMiddenss

ND ND ND

Historical Perspective (Historical Perspective (McErlean et al., McErlean et al., 2002)2002)

ND

ND = no data

PERIODPERIOD MolluscsMolluscs CRUSTACEACRUSTACEA FinfishFinfish SeaweedSeaweed Habitat/ Habitat/ species species changeschanges

2020thth C C

1900-1920s1900-1920s

1930-1960s1930-1960s

1970s-1980s1970s-1980s

1990s-20001990s-2000

NDCollapse of oysters

ND Herring decline

ND

NDND Herrin

g collapse

NDSpartina introduced

Oyster aquaculture; scallop fishing

Potting: Cancer, Homarus, Nephrops

ND NDModiolus damage (Brown ’89); Skate absent

Historical Historical PerspectivePerspective

Oyster restoration aquaculture: Pecten; Mytilus

Potting: portunids ND

experimental seaweed aquaculture

Modiolus damage confirmed; Sargassum

ND = no data

Subtidally the major documented changes between the Subtidally the major documented changes between the earlier studies and the present study have been in earlier studies and the present study have been in biogenic reefs of biogenic reefs of Modiolus:Modiolus:

Habitat/species changes confirmed/recordedHabitat/species changes confirmed/recorded

by SLECIby SLECI

Large-scale reductions in the extent, reported by Large-scale reductions in the extent, reported by recent surveys were confirmed by both direct recent surveys were confirmed by both direct observation and broadscale mappingobservation and broadscale mapping

Densites have declined and community structure Densites have declined and community structure has changedhas changed

Other subtidal communities were largely unchanged in Other subtidal communities were largely unchanged in both species composition and abundance when both species composition and abundance when compared with earlier studiescompared with earlier studies

Indeed all major habitat types/ biotope complexes Indeed all major habitat types/ biotope complexes reported by Ulster Museum sub-littoral surveys in the reported by Ulster Museum sub-littoral surveys in the 1970s and 1980s are still present1970s and 1980s are still present

However, population structure at the However, population structure at the remaining intact sites studied is comparable remaining intact sites studied is comparable to earlier studies and there is evidence of to earlier studies and there is evidence of recruitmentrecruitment

Habitat/species changes confirmed/recordedHabitat/species changes confirmed/recorded

by SLECIby SLECI

Intertidally:Intertidally:

ZosteraZostera and and Ostrea Ostrea have declined and increased within have declined and increased within the last 100 years, the last 100 years, AscophyllumAscophyllum has declined over has declined over recent years and the local distributions of recent years and the local distributions of Gibbula Gibbula umbilicalisumbilicalis and and Osilinus lineatusOsilinus lineatus have changed have changed

Habitat/species changes confirmed/recordedHabitat/species changes confirmed/recorded

by SLECIby SLECI

There has been: There has been: a general decline in commercial fishinga general decline in commercial fishing a steady but regulated expansion in aquaculturea steady but regulated expansion in aquaculture no major changes in pollutant loadings apart from no major changes in pollutant loadings apart from

tin and chromium levels which have both declined tin and chromium levels which have both declined blooms of some algal speciesblooms of some algal species

We have witnessed a number of introductions of non-We have witnessed a number of introductions of non-native and non-local species, both native and non-local species, both

deliberate: deliberate: SpartinaSpartina, , Crassostrea gigasCrassostrea gigas, , Ostrea edulisOstrea edulis and and Pecten maximusPecten maximus

and and

Accidental: Accidental: SargassumSargassum

Other ChangesOther Changes

In the 1970s & 80s In the 1970s & 80s ModiolusModiolus beds were known to be beds were known to be extensive in Strangford Lough (Seed & Brown, 1977; extensive in Strangford Lough (Seed & Brown, 1977; Erwin, 1978, Erwin Erwin, 1978, Erwin et alet al, 1990)., 1990).

In the early 1990s certain areas, particularly those In the early 1990s certain areas, particularly those occupied by the occupied by the M. modiolus/ Chlamys variaM. modiolus/ Chlamys varia community, community, were impacted by mobile fishing gear (Service & were impacted by mobile fishing gear (Service & Magorrian, 1997). Magorrian, 1997).

Brown (1989) published report suggesting trawling Brown (1989) published report suggesting trawling has damaged has damaged M modiolus M modiolus communities in Strangford communities in Strangford LoughLough

Trawling and dredging are known to damage biogenic Trawling and dredging are known to damage biogenic reefs and seabed communities (Watling & Norse, 1998; reefs and seabed communities (Watling & Norse, 1998; Cranfield Cranfield et al.et al. 2003). 2003).

As a result of recommendations by DARD (formerly As a result of recommendations by DARD (formerly DANI a number of legislative measures were introduced in DANI a number of legislative measures were introduced in 1993 to manage fishing activity. 1993 to manage fishing activity.

Judging by fishing returns for species such as scallops Judging by fishing returns for species such as scallops ((PectenPecten & & AequipectenAequipecten), fishing using mobile bottom gear ), fishing using mobile bottom gear peaked between the late ‘80s and early ’90speaked between the late ‘80s and early ’90s

In their 1997 paper Service and Magorrian suggested In their 1997 paper Service and Magorrian suggested that reduction in fishing activity would afford the that reduction in fishing activity would afford the opportunity to follow recoveryopportunity to follow recovery

SLECI found no evidence of recovery of SLECI found no evidence of recovery of Modiolus Modiolus reefs reefs in impacted areasin impacted areas

Communities damaged by bottom gear and discards Communities damaged by bottom gear and discards attract predators and may be subject to heavy predationattract predators and may be subject to heavy predation

Evidence for this is provided by increasing starfish Evidence for this is provided by increasing starfish abundance in visual fast counts of benthic video abundance in visual fast counts of benthic video surveys between 1993 and 2002 and the observation surveys between 1993 and 2002 and the observation of large starfish in the SLECI diving surveyof large starfish in the SLECI diving survey

Damage to the reef structure and its epifauna, Damage to the reef structure and its epifauna, especially sponges, increases its vulnerability to especially sponges, increases its vulnerability to predation (see Bloom, 1975, Pitcher & Bingham, 2002)predation (see Bloom, 1975, Pitcher & Bingham, 2002)

In impacted areas we have heard that K-selected In impacted areas we have heard that K-selected (long-lived) species are generally decreasing and r-(long-lived) species are generally decreasing and r-selected (short-lived) species are increasing in both selected (short-lived) species are increasing in both ModiolusModiolus and infaunal communities and infaunal communities

Experience ElsewhereExperience Elsewhere

Studies by Cranfield Studies by Cranfield at al.at al. -1999 & 2003 in the Foveaux -1999 & 2003 in the Foveaux Strait, New Zealand, where oStrait, New Zealand, where oyster dredging has yster dredging has occurred over 130 years,occurred over 130 years, contribute to our understanding contribute to our understanding of interactions between fishing and biogenic reefs :of interactions between fishing and biogenic reefs :

As well as removing the reefs and oysters, dredging As well as removing the reefs and oysters, dredging resulted in the release of large volumes ofresulted in the release of large volumes of biogenic biogenic sediments which were deposited elsewhere and the sediments which were deposited elsewhere and the seafloor reverted to underlying pebble gravel so that seafloor reverted to underlying pebble gravel so that the substrates underlying biogenic reefs were exposedthe substrates underlying biogenic reefs were exposed

Before dredging, bryozoan reefs and associated Before dredging, bryozoan reefs and associated oysters (oysters (OstreaOstrea [ [TisostreaTisostrea] ] chilensischilensis) were tidally ) were tidally oriented in areas of strong current oriented in areas of strong current

Other sites showed the development of biogenic Other sites showed the development of biogenic reefs of reefs of Modiolus areolatusModiolus areolatus which were also tidally which were also tidally orientedoriented

They concluded that attempts to rebuild a fishery may They concluded that attempts to rebuild a fishery may be more successful if combined with habitat restorationbe more successful if combined with habitat restoration

The Foveaux StraitThe Foveaux Strait experiences strong tidal experiences strong tidal currents which accelerate this processcurrents which accelerate this process

Surveys in 1998 revealed that some sites which had Surveys in 1998 revealed that some sites which had been unfished for 49 years showed no regeneration of been unfished for 49 years showed no regeneration of biogenic reefsbiogenic reefs

Relevance to the present studyRelevance to the present study

Although the Foveaux Strait is in a near open ocean Although the Foveaux Strait is in a near open ocean situation and Strangford Lough is enclosed, there are situation and Strangford Lough is enclosed, there are parallels in that both experience strong tidal flowsparallels in that both experience strong tidal flows

In Strangford Lough, strong tidal flows surge through In Strangford Lough, strong tidal flows surge through the Narrows and through the central channels the Narrows and through the central channels becoming dissipated in the upper reaches of the Lough becoming dissipated in the upper reaches of the Lough

It is possible that any impact on It is possible that any impact on ModiolusModiolus reefs will be reefs will be accelerated by tidal currents and the release of sedimentaccelerated by tidal currents and the release of sediment

AscophyllumAscophyllum may have declined as a result of a may have declined as a result of a combination of increased grazing by limpets and changes combination of increased grazing by limpets and changes in wind patterns in wind patterns

INTERTIDAL CHANGESINTERTIDAL CHANGES

ZosteraZostera densities declined as a result of disease and densities declined as a result of disease and may be expanding now in response to improved water may be expanding now in response to improved water clarityclarity

Recent increases inRecent increases in Ostrea Ostrea are probably a result are probably a result of restoration and over-summering commercial of restoration and over-summering commercial stocks but this may have occurred fortuitously at the stocks but this may have occurred fortuitously at the time when time when Modiolus Modiolus densities were declining so that densities were declining so that oysters can capitalise on primary production no oysters can capitalise on primary production no longer being used by longer being used by ModiolusModiolus

Strangford Lough is a complex systemStrangford Lough is a complex system

It has been used by humans since prehistoric times It has been used by humans since prehistoric times with changes in resource exploitation in response to with changes in resource exploitation in response to changes in demands and different levels of impact changes in demands and different levels of impact from relatively benign to localised extinction of speciesfrom relatively benign to localised extinction of species

The most recent impact has been the severe decline in The most recent impact has been the severe decline in ModiolusModiolus biogenic reefs and changes in their associated biogenic reefs and changes in their associated communitiescommunities

SUMMARY and CONCLUSIONSSUMMARY and CONCLUSIONS

Other recent changes include increases in Other recent changes include increases in ZosteraZostera and and Ostrea ; Ostrea ; decreases in decreases in AscophyllumAscophyllum and and distributional changes in distributional changes in Gibbula umbilicalisGibbula umbilicalis and and Osilinus lineatusOsilinus lineatus

Although apparently well studied our understanding Although apparently well studied our understanding of the Lough is incompleteof the Lough is incomplete

Long-term data are fragmentary and monitoring has Long-term data are fragmentary and monitoring has been inadequately coordinated - i.e. fisheries and been inadequately coordinated - i.e. fisheries and environmental data, environmental/habitat monitoringenvironmental data, environmental/habitat monitoring

AcknowledgementsAcknowledgements

Principal InvestigatorsPrincipal Investigators

Bernard Picton, UM; Matthew Service, DARDBernard Picton, UM; Matthew Service, DARD

InvestigatorsInvestigators

Carys Ann Davies; Annika Mitchell; JamesCarys Ann Davies; Annika Mitchell; James

Strong; Heather Moore; Samantha Vize;Alex Strong; Heather Moore; Samantha Vize;Alex

Portig; Jane Preston; David SmythPortig; Jane Preston; David Smyth