Bycatch

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Bycatch

• Fish 323

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Structure of lecture

• Definition
• Consequences
• How it happens
• Solutions
• Case studies
• Shrimp turtles
• Tuna porpoise
• Vaquita
• Seabirds 2

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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

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Impacts

• Threatened species (esp long-lived species with
  low maximum reproduction)
• Reduced abundance of commercial species
• Changes in ecosystem function

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Scale
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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)

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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.

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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.

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The dirtiest 20 by-catch fisheries in the world
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Bycatch from a shrimp trawl
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The cleanest 10
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Why does it happen?

• Discarding of targeted species
• Size regulations
• High-grading
• Catch and release fisheries

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Global marine bycatch/ discards
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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

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Potential solutions

• Need to be
• Technically feasible
• Financially and economically viable
• Enforceable

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Shrimp-Turtle
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Tuna-Dolphin
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Vaquita
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Seabirds
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ccontrol sslsingle streamer line pslpaired
streamer line
Cooperative research
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Compensatory mitigation
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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.