Putative fishery-induced changes in biomass and population size structures of demersal deep-sea fishes in ICES Sub-area VII, North East Atlantic Ocean

Jasmin A. Godbold, David M. Bailey, Martin Collins, John D. M. Gordon, Waldemar A. Spallek, Imants G. Priede

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Abstract

A time series from 1977–1989 and 2000–2002 of scientific trawl surveys in the Porcupine Seabight and adjacent Abyssal Plain of the NE Atlantic was analysed to assess changes in demersal fish biomass and length frequency. These two periods coincide with the on-set of the commercial deep-water fishery in the late 1970s and the on-set of the regulation of the fishery in the early 2000's and allowed us to investigate changes in the relationship between total demersal fish biomass and depth between the pre- and post commercial fishing periods, changes in the biomass (kg km2) depth distribution and length frequency distribution of the most dominant fish species. Our results show a decline in total demersal fish biomass of 36% within the depth range of the commercial fishery (< 1500 m). Whilst there were significant declines in target (e.g. Coryphaenoides rupestris decreased by 57%) and non-target (e.g. Coryphaenoides guentheri and Antimora rostrata) species, not all species declined significantly. Changes in the overall length-frequency distribution were detected for 2 species (Coryphaenoides armatus, Synaphobranchus kaupii), but only at depths greater than 1800 m (outside the maximum depth for commercial trawling). This suggests that whilst there is evidence for likely fisheries impacts on the biomass distribution of the demersal fish population as a whole, species-specific impacts are highly variable. It is clear that changes in population structure can extend beyond the depth at which fishing takes place, highlighting the importance for also considering the indirect effects on deep-sea fish populations.
Original languageEnglish
Pages (from-to)10757-10783
Number of pages27
JournalBiogeosciences Discussions
Volume10
Issue number1
Early online date10 Aug 2012
DOIs
Publication statusPublished - 25 Jan 2013

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size structure
Atlantic Ocean
demersal fish
marine fish
deep sea
population size
fishery
fisheries
biomass
ocean
fish
fishing
abyssal plain
trawling
fisheries law
population structure
vertical distribution
deep water
time series analysis
time series

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Putative fishery-induced changes in biomass and population size structures of demersal deep-sea fishes in ICES Sub-area VII, North East Atlantic Ocean. / Godbold, Jasmin A.; Bailey, David M.; Collins, Martin; Gordon, John D. M.; Spallek, Waldemar A. ; Priede, Imants G.

In: Biogeosciences Discussions, Vol. 10, No. 1, 25.01.2013, p. 10757-10783.

Research output: Contribution to journalComment/debate

Godbold, Jasmin A. ; Bailey, David M. ; Collins, Martin ; Gordon, John D. M. ; Spallek, Waldemar A. ; Priede, Imants G. / Putative fishery-induced changes in biomass and population size structures of demersal deep-sea fishes in ICES Sub-area VII, North East Atlantic Ocean. In: Biogeosciences Discussions. 2013 ; Vol. 10, No. 1. pp. 10757-10783.
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abstract = "A time series from 1977–1989 and 2000–2002 of scientific trawl surveys in the Porcupine Seabight and adjacent Abyssal Plain of the NE Atlantic was analysed to assess changes in demersal fish biomass and length frequency. These two periods coincide with the on-set of the commercial deep-water fishery in the late 1970s and the on-set of the regulation of the fishery in the early 2000's and allowed us to investigate changes in the relationship between total demersal fish biomass and depth between the pre- and post commercial fishing periods, changes in the biomass (kg km2) depth distribution and length frequency distribution of the most dominant fish species. Our results show a decline in total demersal fish biomass of 36{\%} within the depth range of the commercial fishery (< 1500 m). Whilst there were significant declines in target (e.g. Coryphaenoides rupestris decreased by 57{\%}) and non-target (e.g. Coryphaenoides guentheri and Antimora rostrata) species, not all species declined significantly. Changes in the overall length-frequency distribution were detected for 2 species (Coryphaenoides armatus, Synaphobranchus kaupii), but only at depths greater than 1800 m (outside the maximum depth for commercial trawling). This suggests that whilst there is evidence for likely fisheries impacts on the biomass distribution of the demersal fish population as a whole, species-specific impacts are highly variable. It is clear that changes in population structure can extend beyond the depth at which fishing takes place, highlighting the importance for also considering the indirect effects on deep-sea fish populations.",
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AB - A time series from 1977–1989 and 2000–2002 of scientific trawl surveys in the Porcupine Seabight and adjacent Abyssal Plain of the NE Atlantic was analysed to assess changes in demersal fish biomass and length frequency. These two periods coincide with the on-set of the commercial deep-water fishery in the late 1970s and the on-set of the regulation of the fishery in the early 2000's and allowed us to investigate changes in the relationship between total demersal fish biomass and depth between the pre- and post commercial fishing periods, changes in the biomass (kg km2) depth distribution and length frequency distribution of the most dominant fish species. Our results show a decline in total demersal fish biomass of 36% within the depth range of the commercial fishery (< 1500 m). Whilst there were significant declines in target (e.g. Coryphaenoides rupestris decreased by 57%) and non-target (e.g. Coryphaenoides guentheri and Antimora rostrata) species, not all species declined significantly. Changes in the overall length-frequency distribution were detected for 2 species (Coryphaenoides armatus, Synaphobranchus kaupii), but only at depths greater than 1800 m (outside the maximum depth for commercial trawling). This suggests that whilst there is evidence for likely fisheries impacts on the biomass distribution of the demersal fish population as a whole, species-specific impacts are highly variable. It is clear that changes in population structure can extend beyond the depth at which fishing takes place, highlighting the importance for also considering the indirect effects on deep-sea fish populations.

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