Population trends of bycatch species reflect improving status of target species

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4 Citations (Scopus)

Abstract

Synthesis studies of fish stocks worldwide suggest improving status of mainly target species that are fully assessed. Other analyses, primarily based on catch data alone, but which include a wider range of species as well as bycatch, present a different view. Catch only analyses could be more robust if fishery independent data were used and discards accounted for. We develop a model that uses only survey biomass at length and landings data to estimate fishing mortality, spawning stock biomass (SSB) and discards. An analysis of species from the North Sea shows the model results compare well with most fully assessed stocks. When applied to bycatch species with limited data, trends in fishing mortality and SSB typically reflect those of the target species. In the last decade mean fishing mortality rates have tended to decline while mean spawning stock biomass (SSB) has increased. Despite increasing SSB, recent mean recruitment appears to have been lower than previously which may limit future biomass recovery. Species usually associated with more northerly distributions appear to show the greatest effect of weaker recruitment which may be linked to climate. Estimated discards have tended to decline in magnitude as a result of reduced fishing mortality and associated lower total catches. The model offers a simple way to use both landings and survey data to obtain more detailed population trends for data limited species.
LanguageEnglish
Number of pages16
JournalFish and Fisheries
Early online date9 Jan 2018
DOIs
Publication statusE-pub ahead of print - 9 Jan 2018

Fingerprint

bycatch
Biomass
fishing mortality
Target
biomass
spawning
Population
Mortality
North Sea
Fisheries
catch statistics
Climate
Mortality Rate
Survey Data
Trends
population trend
Fish
Fishes
fisheries
Recovery

Keywords

  • target species
  • bycatch
  • fishing mortality
  • spawning stock biomass (SSB)
  • discards

Cite this

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title = "Population trends of bycatch species reflect improving status of target species",
abstract = "Synthesis studies of fish stocks worldwide suggest improving status of mainly target species that are fully assessed. Other analyses, primarily based on catch data alone, but which include a wider range of species as well as bycatch, present a different view. Catch only analyses could be more robust if fishery independent data were used and discards accounted for. We develop a model that uses only survey biomass at length and landings data to estimate fishing mortality, spawning stock biomass (SSB) and discards. An analysis of species from the North Sea shows the model results compare well with most fully assessed stocks. When applied to bycatch species with limited data, trends in fishing mortality and SSB typically reflect those of the target species. In the last decade mean fishing mortality rates have tended to decline while mean spawning stock biomass (SSB) has increased. Despite increasing SSB, recent mean recruitment appears to have been lower than previously which may limit future biomass recovery. Species usually associated with more northerly distributions appear to show the greatest effect of weaker recruitment which may be linked to climate. Estimated discards have tended to decline in magnitude as a result of reduced fishing mortality and associated lower total catches. The model offers a simple way to use both landings and survey data to obtain more detailed population trends for data limited species.",
keywords = "target species, bycatch, fishing mortality, spawning stock biomass (SSB), discards",
author = "Cook, {Robin M.} and Heath, {Michael R.}",
year = "2018",
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doi = "10.1111/faf.12265",
language = "English",
journal = "Fish and Fisheries",
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TY - JOUR

T1 - Population trends of bycatch species reflect improving status of target species

AU - Cook, Robin M.

AU - Heath, Michael R.

PY - 2018/1/9

Y1 - 2018/1/9

N2 - Synthesis studies of fish stocks worldwide suggest improving status of mainly target species that are fully assessed. Other analyses, primarily based on catch data alone, but which include a wider range of species as well as bycatch, present a different view. Catch only analyses could be more robust if fishery independent data were used and discards accounted for. We develop a model that uses only survey biomass at length and landings data to estimate fishing mortality, spawning stock biomass (SSB) and discards. An analysis of species from the North Sea shows the model results compare well with most fully assessed stocks. When applied to bycatch species with limited data, trends in fishing mortality and SSB typically reflect those of the target species. In the last decade mean fishing mortality rates have tended to decline while mean spawning stock biomass (SSB) has increased. Despite increasing SSB, recent mean recruitment appears to have been lower than previously which may limit future biomass recovery. Species usually associated with more northerly distributions appear to show the greatest effect of weaker recruitment which may be linked to climate. Estimated discards have tended to decline in magnitude as a result of reduced fishing mortality and associated lower total catches. The model offers a simple way to use both landings and survey data to obtain more detailed population trends for data limited species.

AB - Synthesis studies of fish stocks worldwide suggest improving status of mainly target species that are fully assessed. Other analyses, primarily based on catch data alone, but which include a wider range of species as well as bycatch, present a different view. Catch only analyses could be more robust if fishery independent data were used and discards accounted for. We develop a model that uses only survey biomass at length and landings data to estimate fishing mortality, spawning stock biomass (SSB) and discards. An analysis of species from the North Sea shows the model results compare well with most fully assessed stocks. When applied to bycatch species with limited data, trends in fishing mortality and SSB typically reflect those of the target species. In the last decade mean fishing mortality rates have tended to decline while mean spawning stock biomass (SSB) has increased. Despite increasing SSB, recent mean recruitment appears to have been lower than previously which may limit future biomass recovery. Species usually associated with more northerly distributions appear to show the greatest effect of weaker recruitment which may be linked to climate. Estimated discards have tended to decline in magnitude as a result of reduced fishing mortality and associated lower total catches. The model offers a simple way to use both landings and survey data to obtain more detailed population trends for data limited species.

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