Fisheries Bycatch Flashcards
What is bycatch?
The unintended capture or entanglement of species in fishing gear
Major driver of mortality for marine mammals
Define depredation
Marine mammals will try to capture prey items that are stuck in fishing gear which could potentially result in then becoming bycatch
What are some different types of fishing gear?
- Gill net (mesh size = dependent on target species)
- Traps or pots (used for benthic organisms (lobsters / crabs))
Are long-lived or short lived species more vulnerable to bycatch
- Long-lived species
- Ex: marine mammals, seabirds, sharks, sea turtles
Describe the dynamics of bycatch
- 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)
What are some marine mammals that are particularly vulnerable to bycatch?
- Small populations
- Cetaceans and sirenians (limited rates of potential increase)
What are some marine mammals that are particularly resilient to bycatch?
Pinnipeds (relatively high rates of increase)
What is the most endangered mammal species globally and why?
The Vaquita porpoise is the most endangered mammal species globally likely due to its restricted range being in a heavily fished area
How does bycatch of the Vaquita porpoise occur?
- 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)
Describe the recovery plan for the Vaquita
- 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%
Was the recovery plan for the Vaquita’s successful?
- Little evidence of illegal fishing BUT…
- Limited sightings of Vaquita
(so not really)
Describe the acoustic monitoring program for the Vaquita’s
- 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
Was the captive breeding program for the Vaquita successful?
- No
- Vaquita’s reacted poorly to being held in captivity
- Rescue efforts = suspended
About how many Vaquita’s are alive today?
Approximately 10 :(
Describe the New Hampshire Pinger Experiment
- 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
What are some questions that have been raised in regards to the New Hampshire Pinger Experiment?
- Can the results be generalized
- What is the mechanism of deterrence
- Do porpoises habituate
- Does this work in a real life fishery
What are some issues with the New Hampshire Pinger Experiment?
- Cost
- Practicality
- Enforcement (how do you ensure fishers are using pingers?)
- Are pingers a dinner bell to pinnipeds or other cetaceans?
Describe the take reduction plan for harbor porpoises
- 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
Was the take reduction plan for harbor porpoises successful?
- Yes!
- By 2001 the anthropogenic mortality for the harbor porpoise was < PBR
- It continues to stay below PBR today!
Has enforcement of the TRP for harbor porpoises been a success?
- 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
What is the pelagic observer program?
- 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
Describe pilot whale bycatch with pelagic longlines
- Pilot whales = suction feeders and will typically steal tuna from pelagic longline (depredation)
- Bycatch = primarily in the late Summer, Fall, or early Winter
What are some mitigation efforts that have been taken to reduce the bycatch of pilot whales?
- Acoustic deterrents (there is evidence of habituation)
- Decrease in mainline length
- Decrease soak time
Efforts have been largely unsuccessful
What is an alternative mitigation effort that can potentially decrease Pilot whale bycatch?
- 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
Describe the spatial aspects of pilot whale longline overlap
Pilot whales occur inshore where longlines are more dispersed resulting in a great deal of overlap
How can pilot whale distribution be predicted?
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
How can observed environmental conditions be used to mitigate pilot whale interference with longlines?
- 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
In recent years, how have climate models been used to shape management efforts to minimize impacts on marine mammals?
- 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
