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Little Fish, Big Impact
A SUMMARY OF NEW SCIENTIFIC ANALYSISManaging a crucial link in ocean
food webs
A R E P O RT F R O M T H E L E N F E S T F O RA G E F I S H TA S K F O RC E
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What Are Forage Fish?
• Crucial species in food webs
• Small, often schooling pelagic species
• Sardines, anchovies, sand eels, krill, herring…
• Feed on plankton and transfer energy to upper trophic levels
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37% of the world’s marine catch is forage fish
(Alder et al. 2008)
Anchoveta processing plant. Paracas, Peru 2011
Fish meal
Fish oil
3
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Important Forage Fish Characteristics
• Historical view: forage fish are beyond the capacity of man to deplete.
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Collapses have occurredCalifornia sardine-
1950s
Peruvian anchoveta- 1970s
Namibian sardine-1970s
Japanese sardine- 1990s
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Task Force Members
Dr. Ellen K. Pikitch, ChairDr. P. Dee BoersmaDr. Ian L. BoydDr. David O. ConoverDr. Philippe CuryDr. Tim EssingtonDr. Selina S. HeppellDr. Edward D. HoudeDr. Marc Mangel
Dr. Daniel PaulyDr. Éva PlagányiDr. Keith SainsburyDr. Robert S. Steneck
Objective: Develop consensus recommendations on sustainable management of forage fish which accounts for their vital role in ocean ecosystems.
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Task Force Approach
• Workshops and site visits
• Review of theory and practice
• Case studies - ecosystems
• Data – forage fish and predators
• New science• Ecopath models• Ecosim models• Predator Response to
Exploitation of Prey (PREP) equation
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Forage Fisheries Case Studies: Learning from
examples
1. Antarctic
2. Baltic Sea
3. Barents Sea
4. Benguela Current
5. California Current
6. Chesapeake Bay
7. Gulf of Maine
8. Humboldt Current
9. North Sea
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Case Study: Barents Sea
An Effective Threshold
To protect the world’s largest stock of cod, Norway and Russia prohibit fishing for capelin if its biomass falls below 200,000 tonnes. Since adopting this rule, capelin collapses attributable to fishing have not been repeated, and many fish stocks are now abundant.
capelin
Norway Russia
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Foraging Distance & Magellanic Penguins
Foraging-trip distance predicted Magellanic penguin reproductive success in Punta Tombo, Argentina. (Boersma and Rebstock 2009)
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Cury, Boyd et al 2011, Science
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Cury et al. Science 2011;334:1703-1706
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Meta-analysis:
one third for the birds
7 marine ecosystems
14 seabird species
438 years of observation
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Minimum Biomass Threshold
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Approximate locations of the 72 Ecopath models used
in this analysis
Pikitch, Rountos et al. 2012, Fish and Fisheries
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16
Mackerel
Horse Mackerel
Other large pelagics Hake
FlatfishesMedium demersals
Medium sciaenids
Chondrichthyans
Jumbo squid
Benthic elasmobranchs
SeabirdsPinnipeds
Cetaceans
Forage Fish
Ecological Importance
Sea robin
95%
15%
62%
83%
29%
46%
28%
10%
12%
3%
3%22%
39%
33%
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Ecological Importance of Forage Species
The Task Force found that 75% of the ecosystems studied have at least one highly or extremely dependent predator.
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Forage Fish
Mackerel
Horse Mackerel
Other large pelagics Hake
FlatfishesMedium demersals
Medium sciaenids
Jumbo squid
Benthic elasmobranchs
Chondrichthyans
Economic Importance
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Economic Value of Forage Fish
FORAGE FISH DIRECT VALUE
FORAGE FISH SUPPORTIVE VALUE
Direct value of commercial catch = $5.6 billion
Supportive commercial value = $11.3 billion
Total global commercial value = $16.9 billion Value in 2006 dollars
First ever estimate of total value of forage fish to all fisheries
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Ecosim modeling approach
• Ecosystem Modeling Setup• Ecosim with MSE Batch Module: Allows for
examination of implementation error and a wide variety of harvest strategies
• 10 Ecosystem models • 2 upwelling (N. Humboldt & Northern
California)• 1 Semi Enclosed Sea (Baltic Sea) • 3 Non-Upwelling Coastal (Gulf of Mexico,
North Sea, Western English Channel)• 3 Arctic-High Latitude (Aleutian Islands,
GoA, Barents)• 1 Estuaries/ Bay (Chesapeake Bay)
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Forage fish are valuable as prey
Many predators are highly dependent on forage fish...
Predators that have a higher proportion of forage fish in their diet generally exhibit greater declines as forage fish abundance decreases.
…and decline when forage fish decline.
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Minimum Biomass Threshold
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Results: Critical biomass levelsCritical forage fish biomass needed to avoid a 50% decline in predators.
Predator Diet (% forage fish)
Biomass needed (proportion of B0) for
95% confidence of successAll
groupsSeabirds
25% 0.79 0.7450% 0.85 0.8875% 0.88 0.90Max 0.90 0.91
R = Predator Decline (as %); D = Diet Dependency (as a fraction of the total diet); B = Forage Fish Biomass
Results from PREP Equation (Predator Response to Exploitation of Prey):
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Comparing Fishing Strategies
Six fishing strategies were compared using simulation models. Here we compare the most precautionary strategy with conventional management.
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Only Precautionary Management Protects Predators and Fisheries
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Focus on predatorsConsider spatial & temporal managementCut forage fishing in half and leave twice as much fish in the ocean compared with conventional management in many ecosystems.Tailor management to available information
Key Recommendations
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A Lower Ceiling on Forage Fishing
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A Higher Floor on Forage Fish Biomass
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Credit: themaxfiles.blogspot.com
fireflyafrica.blogspot.com
Time and space-based management
Scope of Management Strategies
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Concluding Remarks
Step toward ecosystem-based management
Benefits both the ecosystem and fisheries Maintains ecological roles and support
services Reduces risk of forage fishery collapse May increase catch of commercially
valuable fish Positive incentives for increasing
knowledge
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Special Thanks To:
Task Force Members
Christine Santora, Project Director
Konstantine Rountos
Kristin Broms
Tess Geers
Natasha Gownaris
Steve Munch
David Conover
Jesse Bruschini
Shaily Rahman
Joel Rice
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Comparison ofharvest control rules
Constant yield and constant fishing (CF) mortality rules.
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Comparison ofharvest control rules
Biomass limit rules.
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Comparison ofharvest control rules
Hockey stick rules.
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Predator Criterion
Adopt harvest strategies and management measures so that there is a greater than 95 percent chance that fishing on forage fish will not deplete any dependent predator population to levels that would meet the IUCN “vulnerable” criteria.
“Dependent Predator Performance Criterion”
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