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MAR 370 > Fisheries Bycatch > Flashcards

Fisheries Bycatch Flashcards

1
Q

What is bycatch?

A

The unintended capture or entanglement of species in fishing gear
Major driver of mortality for marine mammals

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2
Q

Define depredation

A

Marine mammals will try to capture prey items that are stuck in fishing gear which could potentially result in then becoming bycatch

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3
Q

What are some different types of fishing gear?

A
  • Gill net (mesh size = dependent on target species)
  • Traps or pots (used for benthic organisms (lobsters / crabs))
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4
Q

Are long-lived or short lived species more vulnerable to bycatch

A
  • Long-lived species
  • Ex: marine mammals, seabirds, sharks, sea turtles
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5
Q

Describe the dynamics of bycatch

A
  • Dependent on the maximum sustainable yield (MSY) for a species
  • Target species typically have a higher MSY than bycatch species (because they can reproduce / replenish their numbers quickly)
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6
Q

What are some marine mammals that are particularly vulnerable to bycatch?

A
  • Small populations
  • Cetaceans and sirenians (limited rates of potential increase)
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7
Q

What are some marine mammals that are particularly resilient to bycatch?

A

Pinnipeds (relatively high rates of increase)

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8
Q

What is the most endangered mammal species globally and why?

A

The Vaquita porpoise is the most endangered mammal species globally likely due to its restricted range being in a heavily fished area

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9
Q

How does bycatch of the Vaquita porpoise occur?

A
  • Artisanal fisheries
  • Fishing income is a key part of the economy in the villages near the Vaquita’s range
  • Illegal fishery for totoaba (believed to have special medicinal purposes)
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10
Q

Describe the recovery plan for the Vaquita

A
  • Implemented in 2008
  • Fishing ban inside the Vaquita refuge (50% of population occurred here)
  • Two year gill net ban in 2015 by Mexican president
  • Increased enforcement / compensation for fishermen
  • 2018 Mexican government enlarged the Vaquita protected area by 50%
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11
Q

Was the recovery plan for the Vaquita’s successful?

A
  • Little evidence of illegal fishing BUT…
  • Limited sightings of Vaquita
    (so not really)
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12
Q

Describe the acoustic monitoring program for the Vaquita’s

A
  • Passive acoustic monitoring program was established from 2011-2015 to monitor Vaquita populations
  • BUT…many detectors were lost due to illegal fishing for totoaba within the Vaquita protected area
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13
Q

Was the captive breeding program for the Vaquita successful?

A
  • No
  • Vaquita’s reacted poorly to being held in captivity
  • Rescue efforts = suspended
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14
Q

About how many Vaquita’s are alive today?

A

Approximately 10 :(

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15
Q

Describe the New Hampshire Pinger Experiment

A
  • Placed pingers on gill nets in an effort to deter marine mammals
  • The results of the experiment seemed to prove that it was a success as there were only 2 porpoises that were caught compared to 25 porpoises caught in the gill nets without pingers
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16
Q

What are some questions that have been raised in regards to the New Hampshire Pinger Experiment?

A
  • Can the results be generalized
  • What is the mechanism of deterrence
  • Do porpoises habituate
  • Does this work in a real life fishery
17
Q

What are some issues with the New Hampshire Pinger Experiment?

A
  • Cost
  • Practicality
  • Enforcement (how do you ensure fishers are using pingers?)
  • Are pingers a dinner bell to pinnipeds or other cetaceans?
18
Q

Describe the take reduction plan for harbor porpoises

A
  • Harbor porpoise stock = strategic (anthropogenic mortality > PBR)

In the gulf of Maine:
- Time - area closures
- Pingers required on gill nets

In the Mid-Atlantic:
- Area closures
- Gear restrictions

19
Q

Was the take reduction plan for harbor porpoises successful?

A
  • Yes!
  • By 2001 the anthropogenic mortality for the harbor porpoise was < PBR
  • It continues to stay below PBR today!
20
Q

Has enforcement of the TRP for harbor porpoises been a success?

A
  • Not really
  • 2003 federal observers monitored 217 sink gill net trips
  • 173 trips were not in compliance with TRP
  • 18 trips were fishing in closed areas
  • 155 trips were fishing without pingers
21
Q

What is the pelagic observer program?

A
  • Government fisheries observers collect data from US commercial fishing vessels
  • Observe target catch and bycatch
  • Provides valuable data on how many marine mammals are killed and injured in fisheries
22
Q

Describe pilot whale bycatch with pelagic longlines

A
  • Pilot whales = suction feeders and will typically steal tuna from pelagic longline (depredation)
  • Bycatch = primarily in the late Summer, Fall, or early Winter
23
Q

What are some mitigation efforts that have been taken to reduce the bycatch of pilot whales?

A
  • Acoustic deterrents (there is evidence of habituation)
  • Decrease in mainline length
  • Decrease soak time
    Efforts have been largely unsuccessful
24
Q

What is an alternative mitigation effort that can potentially decrease Pilot whale bycatch?

A
  • Identifying areas and times where fishermen would have a high risk of interacting with pilot whales (dynamic management)
  • Fishermen then use information to determine where to fish to decrease the likelihood of bycatch
25
Q

Describe the spatial aspects of pilot whale longline overlap

A

Pilot whales occur inshore where longlines are more dispersed resulting in a great deal of overlap

26
Q

How can pilot whale distribution be predicted?

A

Pilot whale distribution can be predicted by using a small number of environmental variables (ex: sea surface temperature, sea level anomalies (eddies) etc.) which are used to quantify pilot whale habitat use

27
Q

How can observed environmental conditions be used to mitigate pilot whale interference with longlines?

A
  • Environmental conditions can be used to develop models that predict whale distributions
  • Environmental conditions at observed longlines can predict the probability of pilot whale occurrence
  • Fishermen can use this information to determine where / where not to fish
28
Q

In recent years, how have climate models been used to shape management efforts to minimize impacts on marine mammals?

A
  • Climate models can be used to predict where marine mammals are likely to be in the future
  • This approach can be used to shape management efforts to minimize the impacts on marine mammals and fishers

MAR 370 (14 decks)

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