overfishing in the pacific?
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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).
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