Overfishing in the Pacific?

A new simple method of stock assessment on tropical reef fisherieson tropical reef fisheries

Jeppe Kolding & Einar Hjørleifsson

Actually, first ever stock assessmentassessment

on the inshore fisheriesin Southern pacific

Fisheries Statistics & Stock A t T i iAssessment Training

14-26th January 2008,

University of the South PacificUniversity of the South Pacific, Apia, Samoa

Commissioned byCommissioned byUnited Nations University Fisheries Training Program

(Reykjavik)Commonwealth Secretariat

(London)

Background• Stock assessment in small-scale, multi-gear

multi species fisheries must get a picture ofmulti-species, fisheries must get a picture of the whole, not small fragments of the parts.Si l i t d th d t• Single species assessment and methods not appropriate.

• Data for above not available.• Full fledged length-based assessment too g g

data demanding, too laborious, and not necessary when estimates of biomass and ycatch are available.

MethodsMethods

Pacific Regional Oceanic and Coastal Fisheries DevelopmentCoastal Fisheries Development

ProgrammePROCFi h (EU)PROCFish (EU)

“ implementing of the first comprehensive multi country comparative..implementing of the first comprehensive multi-country comparative assessment of reef fisheries (including resource and human components) ever undertaken in the Pacific Islands..”

13 countries included

Under Water Visual CensusUnder Water Visual Census

Distance-sampling Underwater Visual Census (D UVC)Visual Census (D-UVC)

Each diver records the number of fi h fi h ifish, fish size, distance of fish to the transectto the transect line, and habitat + quality, using pre-printed

d tunderwater paper.

4 habitat types

Sheltered coastal reef Lagoon intermediate reef

Lagoon back-reef Outer reef

Fishing methods….

PROCfish Surveys –Socio economic dataSocio-economic data

The fishing ground (in red) is delineated using information from fishers. Reef areas within the fishing area (in green; interpreted from satellite data) are then identified Theinterpreted from satellite data) are then identified. The remaining non-reef areas within the fishing grounds are labelled as lagoon (in blue).

Household surveys for estimating catches:catches:

Abundance, composition and sizes

Fi fi h i fi ld h t f ti tiFinfish size field survey chart for estimating averagelength of reef and lagoon fish (including 5 size classesfrom A=8 cm to E=40 cm, in 8 cm intervals)., )

MethodsMethods

• Biomass (B) = average standing stock sizeBiomass (B) = average standing stock size– We assume that the UVC surveys are

representative for the annual averagerepresentative for the annual average• Catch (C) = cumulated total catch over 1 year

1 year evens seasonal effects and gives annual– 1 year evens seasonal effects and gives annual values of F (unit = yr-1)

All data (> 120 000 records) entered an• All data (> 120 000 records) entered an analysed in Pasgear 2

Pasgear 2

Version 2.3 (Build 31.10.2007)Jeppe Kolding and Åsmund SkålevikJeppe Kolding and Åsmund Skålevik

www.cdcf.no/data/pasgear

Concepts

• From the standard catch equation then qfishing mortality (F) is simply defined as the fraction of the average population taken by g p p yfishing.

C F B F CB= ⋅ ⇒ = B

ConceptsConcepts• Biomass is renewable (born, grows and dies)

• Biological production (P) = is the total amount of tissue generated in a population in a particular space during a given period of time (this includes fish dying within the period).

• Catch is also fraction of the production

C F B x P x= = ≤( )1C F B x P x= ⋅ = ⋅ ≤( )1PPB

Z P Z B= ⇒ = ⋅( )Allen 1971

ConceptsConcepts• Exploitation rate (E)

= fraction of the production taken by fishing (catch) over a time period g ( )

= ratio of fishing mortality to total mortality

E C F B F F= =

⋅= =E

P Z B Z F M⋅ +

ConceptsConcepts• The Maximum Sustainable Yield (MSY),

has a theoretical maximum value of around half the total production, thus:

MSY P Z B=≈ ≈

⋅2 22 2

PE

P

PMSY ≈ ≈2 0 5. = reference limitP

Stock assessmentCourtesy of ProcFish

Species B Catch F M Z E

- Kg Kg/yr C/B ? LFQVBGF

F/Z

F+M

LiteratureLiteratureFishBaseVBGFLongevityLongevity

Exploitation rate and size(example form Zambia)

0.8

R2 = 0 770.6

0.7

Z)

Tilapia rendalli

R 0.77

0.4

0.5

atio

n ra

te (F

/Z

Large predators

0.3

Mea

n ex

ploi

t

C. gariepinus and S. robustusin seinesTilapia sparmanii

0.1

0.2 medium sized cichlids

small species

M. macrolepidotus

0.00 5 10 15 20 25 30 35 40 45 50

size range of exploitation (L00-L50%, cm)

ResultsResults

Relative importance by familyRelative importance by family

Average biomass by family

Size distributions

Ln-transformed distributions“ it l ”“community slope”

Overall results

Across IslandsAcross Islands

# of sites and transects by country

Country Site

1

Site

2

Site

3

Site

4

Site

5

Tota

l

Country S S S S S T

Fiji 53 24 25 18 25 145FSM 25 45 24 94Marshall Isl. 18 20 19 18 75N 50 50Nauru 50 50Niue 50 50Palau 24 24 22 24 94PNG 24 18 24 18 84Samoa 24 24 28 25 101Solomon Isl. 22 23 23 24 92Tonga 17 24 16 51 22 130Tuvalu 24 24 24 24 96Tuvalu 24 24 24 24 96Vanuatu 24 24 24 24 96Total 18 20 12 22 23 1107

Mean fish density by country

“..large-size families, such as Lethrinids LutjanidsLethrinids, Lutjanids, Serranidsand Scarids, were recorded in very low numbers, which would indicate intense fishingpressure and targeting of these families.” ProcFISH (2005)(2005)

(Thaman & Hassal 1998; FAO 2002; ADB 2000; SOPAC 2005) have cited concerns on resource status and over-exploitation

Density by habitaty y

Number of transects by habitaty

ed/O

ther

hes

ot y

et d

efin

e

oast

al re

ef

agoo

n pa

tc

ack

reef

uter

reef

otal

Country No

Co

La Ba

Ou

To

Fiji 3 27 28 43 44 145FSM 18 16 33 27 94Marshall Isl 24 27 24 75Marshall Isl. 24 27 24 75Nauru 50 50Niue 50 50Palau 17 23 26 28 94PNG 18 18 17 31 84PNG 18 18 17 31 84Samoa 22 13 34 32 101Solomon Isl. 27 14 17 18 16 92Tonga 51 68 11 130Tuvalu 10 9 17 60 96Vanuatu 39 6 8 43 96Total 30 216 222 234 405 1107

Density by all habitats Except outer reef

Density by habitat: Outer reefy y

Community structure: Log b b l thnumber by length

Community slopes [LnNO = a + slope * length]Community slopes [LnNO a slope length]

Nauru

Fiji

Palau

Samoa

Niue

Tonga

FSM

Solomon Isl.

PNG

Niue

Tuvalu

Marshall Isl.

Vanuatu

0.00 0.05 0.10 0.15 0.20 0.25 0.30

Catch vs. human population density (effort)

45

Samoa

Solomon Isl

y = 6.678x0.7939

R2 = 0.530435

40

SamoaSamoa

Solomon Isl.

25

30

km2

per y

ear]

Samoa

Solomon Isl.15

20

Cat

ch [t

per

k

FSM

FSM

PNGPNG

Solomon Isl.

Solomon Isl.Marshall Isl.

Vanuatu

VanuatuTuvalu

Palau

NiueFiji

FijiFiji

5

10

FSMPalauPalauPalauFijiFijiFiji

00 1 2 3 4 5 6 7

Households per km2

Fish density vs. fishing ‘density’

Solomon Ngela350

400

Tuvalu Nukufetau Vanuatu Uri-UripivVanuatu MaskelynesSolomon Marau

Palau Koror

R2 = 0.0053

250

300

S l R

Marshall ArnoFiji LakebaPNG TsoilaunungPNG AndraTuvalu Funafuti

Fiji Mali

200

250

sity

[kg/

500m

2]

Marshall AilukMarshall LauraPalau AiraiFiji MuaivusoFiji LakebaFSM YyinSolomon Chubikopi Samoa Salelavalu Samoa VaisalaPalau NgarchelongVanuatu PaunagisuSamoa Manono-uta Samoa VailoaFSM RiikenVanuatu Moso

Marshall LikiepPalau Ngatpang

Solomon Rarumana

100

150Den

s

Fiji Dromuna Niue All NiueMarshall AilukMarshall LauraPalau Airai

50

00 10 20 30 40 50 60

Number of households per km2

Fish density vs. ‘effort’ (# households)

Solomon Ngela

R2 = 0.0669

350

400

Nauru All Nauru

Tuvalu NukufetauVanuatu Uri-UripivVanuatu MaskelynesSolomon Marau

Palau KororTuvalu Niutao

250

300

S l R

Marshall ArnoFiji Lakeba PNG TsoilaunungPNG AndraTuvalu Funafuti

Tuvalu VaitupuFiji Mali

200

250

sity

[kg/

500m

2]

Marshall AilukMarshall Laura Palau AiraiFiji MuaivusoFiji LakebaFSM Yyin Solomon ChubikopiSamoa SalelavaluSamoa VaisalaPalau NgarchelongVanuatu PaunagisuSamoa Manono-utaSamoa VailoaFSM RiikenVanuatu Moso

Marshall LikiepPalau Ngatpang

Solomon Rarumana

100

150Den

s

“.. The total annual catchfrom the coastal sheltered reef is extremely high, and so

l ti d fi hFiji Dromuna Niue All NiueMarshall AilukMarshall Laura Palau Airai

50

are population and fisherdensity..” ProcFISH (2005)

00 200 400 600 800 1000 1200 1400

Number of households

Fishing mortality (F) vs ‘effort’Fishing mortality (F) vs. effort0.35

Tuvaluy = 0.0002xR2 = 0.1626

0.25

0.30

Nauru

Samoa

Tuvalu0.20

Site

F

Need re-examinationareas are likely wrong

SamoaSamoa0.10

0.15

S

F = 0.23 per year meansCatch = 20% of biomass

FijiFijiFiji

FijiFSM

FSMMarshall IslandsMarshall Islands

Marshall Islands

M h ll I l d

Niue

Palau

P lPapua New Guinea Papua New Guinea

Samoa

Solomon IslandsSolomon Islands

Solomon Islands

Solomon IslandsTuvalu

TuvaluVanuatuVanuatu

VanuatuVanuatu

0.05 Very low fishing pressure

FijiFijiFijiFSMMarshall IslandsMarshall IslandsPalauPalauPalau TuvaluVanuatu0.00

0 200 400 600 800 1000 1200 1400

Number of housholds

F vs effort (# households)F vs effort (# households)0.10 • Weak correlation

0 07

0.08

0.09 • With few exceptions overall values low

• F < 5 % per yearOverfished

?

Solomon Islands

Samoa

Palau

0.05

0.06

0.07

Site

F

Vanuatu

Tuvalu

Solomon Islands

Solomon Islands

Solomon IslandsSolomon Islands

NiueMarshall Islands

M h ll I l dFSMFiji

0.03

0.04

S

VanuatuVanuatu

VanuatuTuvalu

Solomon IslandsPapua New Guinea

Papua New Guinea

PalauPalau PalauMarshall Islands

Marshall Islands

Marshall IslandsFSM

FSMFijiFiji

Fiji

0.00

0.01

0.02

0 100 200 300 400 500 600 700

Number of housholds

Final comments

FIJI ISLANDS

Solomon Islands

Solomon Islands

• Vast archipelago of 992 islands, 347 inhabited• Landmass is 28 000 km2• Landmass is 28,000 km2

• EEZ is 1.63 million km2

• Reef area is 5 750 km2• Reef area is 5,750 km• Population around 538,000 persons• Annual growth rate in 1999 was 2 8%Annual growth rate in 1999 was 2.8%

(doubled to 4.4% in 2005 - one of the highest)• 40% below 15yrs, 58% between 15 – 64 yrs, 2%40% below 15yrs, 58% between 15 64 yrs, 2%

over 65 yrs• Fish consumption per capita is 33 kg/yr

Current Monitoring• International (BINGOs) and local NGOs are

monitoring their respective MPA project sites• SILMMA (Solomon Is Locally Managed Marine• SILMMA (Solomon Is. Locally Managed Marine

Areas) Network

1. TNC – The Nature Conservancy2. WWF – World Wide Fund3 WFC World Fish Center3. WFC – World Fish Center4. FSPI – Foundation of the South Pacific People

International5. TDA – Tetepare Descendent Association6. RCF – Roviana Conservation Foundation

Not a single fisheries biologist on the Islands

RecapRecap

• 992 islands, 347 inhabited992 islands, 347 inhabited• EEZ is 1.63 million sq km• Reef area is 5 750 sq kmReef area is 5,750 sq km

• 65 % of area is ALREADY and MPA !!!• 65 % of area is ALREADY and MPA !!!• World most optimistic target = 30%• Fishing pressure less than 5% of biomass• Fishing pressure less than 5% of biomass• Why are 7 conservation NGO’s present

b t 0 fi h i bi l i t ?– but 0 fisheries biologists?

Thanks for the attention

Find the fisheries biologistg

15 most common families for which D-UVC is kno n as an efficient s r e methodis known as an efficient survey method

• Acanthuridae (surgeonfish); Acanthuridae (surgeonfish);• Balistidae (triggerfish);• Chaetodontidae (butterflyfish);• Holocentridae (squirrelfish);( q );• Kyphosidae (drummer and seachubs);• Labridae (wrasse);• Lethrinidae (sea bream and emperor);• Lutjanidae (snapper and seaperch);• Mullidae (goatfish);• Nemipteridae (coral bream and butterfish);

P thid ( lfi h)• Pomacanthidae (angelfish);• Scaridae (parrotfish);• Serranidae (grouper, rockcod, seabass);• Siganidae (rabbitfish); and• Siganidae (rabbitfish); and• Zanclidae (moorish idol).