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Bycatch - PowerPoint PPT Presentation


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Bycatch Fish 323 Structure of lecture Definition Consequences How it happens Solutions Case studies Shrimp turtles Tuna porpoise Vaquita Seabirds *2 Definition Total fishing mortality excluding that accounted directly by the retained catch of target species (OECD,1997). Includes:

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bycatch

Bycatch

Fish 323

structure of lecture
Structure of lecture
  • Definition
  • Consequences
  • How it happens
  • Solutions
  • Case studies
        • Shrimp turtles
        • Tuna porpoise
        • Vaquita
        • Seabirds *2
slide3

Definition

  • Total fishing mortality excluding that accounted directly by the retained catch of target species (OECD,1997).
  • Includes:
  • Targeted species that are discarded
  • Non-targeted species (incl those targeted in other fisheries)
  • [Ghost-fishing]
impacts
Impacts
  • Threatened species (esp long-lived species with low maximum reproduction)
  • Reduced abundance of commercial species
  • Changes in ecosystem function
scale6
Scale
  • Alaska longline fishery: 10,000-20,000 seabirds per year
  • Global longline fishery: 1.4 billion hooks catch 50-60,000 Leatherback Turtles per year
  • Gulf of Mexico shrimp trawl fishery: 2-5 million lb of red snapper per year (compared to 9 million lb in recreational and commercial fisheries)
repercussions
Repercussions
  • Bycatch of species protected under the ESA or MMPA may lead to fisheries disruption and even closures (e.g. closure of swordfish fishery off Hawaii).
  • For targeted species, the TAC should include all fishing mortality – if bycatch is high in other fisheries, there may be no quota left for the targeted fishery.
  • Attempts to ban imports have led to international trade disputes.
why does it happen
Why does it happen?

Fishing gears:

  • There is potential for bycatch in all gears, but some gears are ‘dirtier’ than others.
  • Some gears are more selective and/ or allow unwanted fish to be released in good condition.
why does it happen15
Why does it happen?

Discarding of targeted species:

  • Size regulations
  • High-grading
  • Catch and release fisheries
potential solutions
Gear modifications

Short-term (or permanent) area closures

Changes in timing of fishing activities, seasonal closures

Reduce fishing pressure

Bycatch quotas (require observers)

Compensatory mitigation

Creation of new markets for bycatch species

Potential solutions
potential solutions18
Need to be:

Technically feasible

Financially and economically viable

Enforceable

Potential solutions
slide24

c=control

ssl=single streamer line

psl=paired streamer line

Cooperative research

summary
Summary
  • By-catch is ever present in fisheries – it can be reduced, but probably rarely eliminated.
  • Solutions need to be technically feasible, financially and economically viable, and enforceable – incentives are an important element in eliminating the problem.