INCOFISH WP7 Sustainability indicators

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INCOFISH WP7Sustainability indicators

• School of Biological Sciences and Business
  School,
• University of Aberdeen
• Graham J. Pierce, Jianjun Wang, Cristina Pita,
  Begoña Santos
• Charlotte Main, Katie Longo, Ioannis Theodossiou,
  Tara Marshall
• Doug Beare, Simon Greenstreet

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Scottish fisheries

• Demersal fish (26 of landings, 35 of value)
• Haddock, whiting, saithe, monkfish, plaice, cod
  (etc)
• Management quotas, MLS, mesh size, closures
• Issues include declining stocks, discarding of
  small fish, by-catch of small fishes, e.g. in
  nephrops fisheries
• Pelagic fish (59 of landings, 30 of value)
• Mackerel, herring, horse mackerel, etc
• Quotas stock sizes have fluctuated widely
• Shellfish (15 of landings, 35 of value)
• Nephrops, scallops, lobster, crabs, squid etc
• Increasing importance, especially for smaller
  boats

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Work carried out by University of Aberdeen

• Logistics
• 6 months of INCOFISH funding for WP7 22 months
  shared between WPs 2, 4, 6, 7 ( students, etc)
• All official data held by FRS marine lab
  (landings, surveys, market sample data)
• Work in year 1
• Interview surveys of Scottish fishermen
  (CP,IT,GP)
• Analysis of historical data to underpin indicator
  selection (does size matter?)
• Trends in fish size and abundance (JW, GP, DB)
• Effects of reducing fishing mortality on cod (CM,
  TM)
• Trends in squid size, abundance and catches (GP,
  JW)
• Other readily available indicators
• Ecological indicators for demersal fish (KL, SG,
  GP)
• Ecological indictors for pelagic systems (BS, GP)

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Interview surveysCristina Pita Ioannis
TheodossiouGraham Pierce

• Opinions and attitudes of fishermen to management
  tools
• Target 200 interviews, West Coast Moray Firth
• Interviews completed to date 25
• Preliminary observations
• Antipathy towards conservation measures (e.g.
  MPAs) due to lack of consultation
• Widespread lack of respect for existing
  regulations (e.g. requirement to discard small
  fish)

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Do trends in fish size in trawl surveys provide
an indication of stock status for gadoids?

• Jianjun Wang, Graham Pierce
• Doug Beare (FRS Marine Laboratory Aberdeen)

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Demersal surveys and fisheries

• Selected results
• Area northern North Sea (ICES subdivision IVa)
• Species whiting, cod
• Whiting MLS27cm mature 25cm (2 y) lifespan
  5-8 y
• Cod MLS 35cm mature 45cm (3-4 y) (Fish ruler
  68cm)
• Data sources
• FRS trawl survey database (catches at length, per
  hour)
• ? Catch rates at length, by subdivision, by year
  or season
• ? Average length by ICES subdivision by year or
  season
• ICES ACFM reports (Spawning stock biomass, by
  area)

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• Since 1982, average length of whiting in survey
  trawl hauls has declined, following the fall in
  SSB
• Based on summed survey hauls across all months
  (i.e. ignores seasonal variation, changes in
  survey methods, etc)

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1960-2003

• Significant correlation at lag 0 average whiting
  length is high in years of high SSB (and remains
  high for 6 years)
• Significant correlation at lag -8 it takes 8
  years for high average length to feed through to
  high SSB

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Whiting further analysis by length class

• Maximum length in trawl surveys 77 cm
• Length Classes C1 L lt27 C2 27 ltL lt37 C3 37
  lt L lt 47 C4 L gt 47 cm

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Whiting further analysis by length class

• SSB most strongly correlated with abundance of
  largest fish negatively correlated with
  abundance of small fish

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Cod

• Since 1982, average length of cod in survey trawl
  hauls has declined, although less fast than the
  decline in SSB
• Based on summed survey hauls across all months
  (i.e. ignores seasonal variation and changes in
  survey methods)

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Cod further analysis by length class

• Maximum length in trawl surveys 142 cm.
• Length Classes C1 L lt35 C2 35 ltL lt70 C3 70
  lt L lt 105 C4 L gt 105 cm
• Since 1982, trend in catch rate for length class
  3 follows SSB

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Rebuilding depleted cod stocks should fishing
mortality on older fish be reduced?

• Charlotte Main
• Supervisor C. Tara Marshall

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Aims Methods

• Aim assess effect of fishing mortality reduction
  directed at particular age classes of cod (Gadus
  morhua)
• Data
• Database for northeast Arctic cod (Gadus morhua)
  stock
• Population growth rate, r, calculated for each
  cohort 194788
• Methods
• Simulate reduced fishing mortality on individual
  age classes (ages 3-13 multiply F by values
  ranging between 0.9 and 0)
• Calculate average effect on r for each age class
  and cohort
• Calculate increase in total egg production for
  each cohort using cohort-specific mean egg
  production-at-age

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Final r-values versus age at which F is reduced
and extent to which mortality is reduced (F
multipliers)
Age
? Increasing reduction of fishing mortality
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Mean increase in r with F reduction at age,
1947 cohort
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Age at which maximum effect of F reduction is seen
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Length at which maximum effect of F reduction is
seen
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(Increase in egg production)
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Results

• Maximum average increase in r resulted from a
  reduction in fishing mortality on age 7 cod (mean
  length 70cm)
• Reducing fishing mortality on older/larger fish
  is less useful (due to their low abundance)
• Effects on egg production vary between cohorts
• Notes
• r was calculated for each cohort without
  consideration of interaction between cohorts
• consequences at population level (integrated
  across all cohorts) remain to be explored

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Indices of squid stock status

• Graham Pierce
• Jianjun Wang

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Loligo life cycle and fishery
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Squid biology and fisheries

• Does catching (small) squid early in the season
  affect later catches?
• Does catch in the breeding season or total catch
  affect subsequent recruitment?
• Is average length an indicator of stock
  abundance?

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Squid catch early v late
High early season catches generally associated
with high late season catches (abundance driven)
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Spring survey catches and sizes v autumn landings

• There is a stock-recruitment relationship

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Prediction of autumn trawl fishery squid catches
(N North Sea, Oct-Dec) from quarterly trawl
survey data (NPUE, Length)

• Avg NPUE 4a,b Q1 R0.425, P0.017
• Avg NPUE 4a,b Q2, R0.028, P0.918
• Avg NPUE 4a,b Q3, R0.178, P0.441
• Avg NPUE 4a,b Q4, R0.273, P0.208
• Avg L 4a,b Q1, R0.198, P0.353
• Avg L 4a,b Q2, R-0.194, P0.526
• Avg L 4a,b Q3, R-0.098, P0.672
• Avg L 4a,b Q4, R-0.064, P0.808

Avg NPUE 6a Q1, R0.607, P0.004 Avg NPUE 6a Q2,
R-0.235, P0.486 Avg NPUE 6a Q3, R-0.865,
P0.058 Avg NPUE 6a Q4, R0.027, P0.900 Avg L 6a
Q1, R0.089, P0.710 Avg L 6a Q2,
R0.617,P0.140 Avg L 6a Q3, insufficient
data Avg L 6a Q4, R-0.593, P0.005

• Growth overfishing is not (yet) an issue
• Autumn catches can be predicted from winter
  surveys (stock-recruitment relationship)
• Squid are smaller on west coast in autumn in
  good years

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The effect of fisheries on fish biodiversity
FISH BIODIVERSITY AN INDICATOR OF ECOSYSTEM
EFFECTS OF FISHERIES? Catherine S. Longo, Simon
P. R. Greenstreet Graham J. Pierce
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BIODIVERSITY - DISTURBANCE RELATIONSHIP
Within a trophic level, diversity ( evenness)
changes as a consequence of disturbance (e.g.
predation, fishing mortality)
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- BECAUSE
1. Diversity is affected by disturbance
(predation/fishing) within each trophic
level
2. Aquatic communities are size-structuredsize
can be used as a proxy for trophic level
3. Fisheries are size-selective
- OUR HYPOTHESIS IS
NO FISHING
INTENSE FISHING
THEREFORE We expect different size-classes to
respond differently to fishing disturbance
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Methods
- The dataset North-western North Sea
FRS marine lab trawl surveys , 1926-96
- Fishing disturbance hours/year commercial
trawl fishing
- Biomass/diversity size-spectra
class 8 (28 29 ) (256
512) g
Normalized biomass divided by corresponding
x-axis log class width
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1. LINEAR FIT OF SPECTRUM
2. ANOVA within EACH SIZE-CLASS

SPATIAL COMPARISON (Pooled data 1982-1996)
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TEMPORAL COMPARISON
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The effect of fisheries on fish biodiversity
Fishing has different effects on the DIVERSITY of
fish according to their SIZE, suggesting a
predatory release effect

• Small, non-target, fish are increasing in
  abundance but their diversity is declining

2. The assemblage appears increasingly dominated
by a small r-selected species Norway
pout (Trisopterus esmarkii)
Size-structured data on diversity and biomass
are readily available from trawl surveys and
provide useful ecological indicators of demersal
trawl fishery sustainability
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INCOFISH WP7Sustainability indicators

• Sustainability indicators
• for pelagic systems

Begoña Santos, Graham Pierce
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April October
April
Biomass Numbers
October
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RDA for species composition, GAM for diversity
April
Longitude
Depth
October
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Back to fish rulersimplementation issues

• Participation
• Fishers
• Consumers, retailers, processors
• Government, EC, ICES, scientists
• Protecting small fish
• Certification (discard-safe big fish?)
• Monitoring and enforcement
• Gear modification
• Multispecies fisheries?
• EFH and protected areas for small fish

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Protecting small fish

• Whiting in the North Sea spatial segregation of
  younger and older fish in survey catches in
  February (Zheng et al., 2001)
• Age-specific spatio-temporal models of essential
  fish habitat could allow targeting of older fish