Bycatch Flashcards
Target catch
Species or species complex that is the target of fishery
Incidental catch
Non-target species that are retained (retention may be dependent on catch rate of target species)
Bycatch
Catch that is not retained (returned to the sea – dead or alive)
Bycatch may be….
Dead
Living at the time of release (Survival depends on conditions and environmental factors)
Non-regulator discard driving factors
Non-target species of limited value
Target species that are damaged, diseased or too small for the market (e.g., cannery)
regulator discard driving factors
Protected species
Size limit (minimum size, slot limit)
Closed season or area
Protected sex
Quota already filled
Retention limit (exceeds allowable fraction of target catch or bag limit)
Global discards cut by ~50%+ 1980s–2010s
WHy?
Greater utilization of bycatch species (aquaculture feed)
More selective fishing methods
Management measures prohibiting or limiting bycatch
Country-level mandates
EU landing obligation (no discards since 2019, though some exemptions)
Iceland, Norway, Namibia prohibit discarding
What is another possibility associated with the decline in bycatch?
Possible that bycatch populations have decreased relative abundance
What are ways to manage bycatch?
Limit overall effort (also reduces target catch)
Time/area closures
Bycatch reduction equipment
Incentivize selective fishing
Time/area closures is related to
Relative abundance of target species and bycatch species are spatial/temporally variable
What does bycath reduction engineering require?
difference in biology (size, movement, behavior, etc.) between target and bycatch species
U.S. Gulf of Mexico Shrimp
“Gulf shrimp” includes white, brown, and pink shrimp
Fishery operates using bottom trawls (twin otter trawls most common)
Economically important fishery → $300M+/yr
Abundance environmentally driven
Bycatch in shrimp fishery
During 1990s, high bycatch rates became an increasing concern (bycatch made up ~84% of total catch by weight)
~90% of age 0 red snapper mortality due to shrimp bycatch
Turtle Excluder Device (TED)
Early designs (‘88 – ‘03)
97% turtle exclusion
4% fish bycatch reduction
0-6% shrimp reduction
2021 NMFS requires TEDs be used in skimmer trawls >40ft