Resolution of multiple cohorts in the Loligo forbesi population from the west of Scotland

M A Collins, P R Boyle, G J Pierce, L N Key, S E Hughes, J Murphy

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Length-frequency analysis was employed to resolve multiple cohorts in the Loligo forbesi population from coastal waters to the west. of Scotland. In both male and female squid two principal cohorts were identified, recruiting to the fished population in April and November. Both cohorts spawned during the winter months (November to April), producing a single extended spawning season, with the April recruits of larger size at spawning than the November recruits. In the males the April recruits appeared to separate into two cohorts of different growth rates, thus producing three rather than two sizes at maturity. The abundance of L. forbesi was low during the summer months, indicating that the squid had moved outside the range of the fishery, perhaps into deeper water. Abundance declined during the spawning season, which is interpreted as post-spawning mortality. Abundance declined earlier in the males than females, producing a female biased sex ratio during most of the spawning season. The two periods of recruitment are not compatible with a 1 year life cycle and single extended spawning season and explanations of this are discussed. (C) 1999 International Council for the Exploration of the Sea.

Original languageEnglish
Pages (from-to)500-509
Number of pages10
JournalICES Journal of Marine Science
Volume56
Publication statusPublished - 1999

Keywords

  • squid
  • loliginid
  • growth
  • life history
  • IRISH WATERS
  • REPRODUCTIVE STRATEGIES
  • SCOTTISH WATERS
  • LIFE-HISTORY
  • CEPHALOPODA
  • LOLIGINIDAE
  • RECRUITMENT
  • VULGARIS
  • MATURATION
  • FISHERY

Cite this

Collins, M. A., Boyle, P. R., Pierce, G. J., Key, L. N., Hughes, S. E., & Murphy, J. (1999). Resolution of multiple cohorts in the Loligo forbesi population from the west of Scotland. ICES Journal of Marine Science, 56, 500-509.

Resolution of multiple cohorts in the Loligo forbesi population from the west of Scotland. / Collins, M A ; Boyle, P R ; Pierce, G J ; Key, L N ; Hughes, S E ; Murphy, J .

In: ICES Journal of Marine Science, Vol. 56, 1999, p. 500-509.

Research output: Contribution to journalArticle

Collins, MA, Boyle, PR, Pierce, GJ, Key, LN, Hughes, SE & Murphy, J 1999, 'Resolution of multiple cohorts in the Loligo forbesi population from the west of Scotland', ICES Journal of Marine Science, vol. 56, pp. 500-509.
Collins MA, Boyle PR, Pierce GJ, Key LN, Hughes SE, Murphy J. Resolution of multiple cohorts in the Loligo forbesi population from the west of Scotland. ICES Journal of Marine Science. 1999;56:500-509.
Collins, M A ; Boyle, P R ; Pierce, G J ; Key, L N ; Hughes, S E ; Murphy, J . / Resolution of multiple cohorts in the Loligo forbesi population from the west of Scotland. In: ICES Journal of Marine Science. 1999 ; Vol. 56. pp. 500-509.
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N2 - Length-frequency analysis was employed to resolve multiple cohorts in the Loligo forbesi population from coastal waters to the west. of Scotland. In both male and female squid two principal cohorts were identified, recruiting to the fished population in April and November. Both cohorts spawned during the winter months (November to April), producing a single extended spawning season, with the April recruits of larger size at spawning than the November recruits. In the males the April recruits appeared to separate into two cohorts of different growth rates, thus producing three rather than two sizes at maturity. The abundance of L. forbesi was low during the summer months, indicating that the squid had moved outside the range of the fishery, perhaps into deeper water. Abundance declined during the spawning season, which is interpreted as post-spawning mortality. Abundance declined earlier in the males than females, producing a female biased sex ratio during most of the spawning season. The two periods of recruitment are not compatible with a 1 year life cycle and single extended spawning season and explanations of this are discussed. (C) 1999 International Council for the Exploration of the Sea.

AB - Length-frequency analysis was employed to resolve multiple cohorts in the Loligo forbesi population from coastal waters to the west. of Scotland. In both male and female squid two principal cohorts were identified, recruiting to the fished population in April and November. Both cohorts spawned during the winter months (November to April), producing a single extended spawning season, with the April recruits of larger size at spawning than the November recruits. In the males the April recruits appeared to separate into two cohorts of different growth rates, thus producing three rather than two sizes at maturity. The abundance of L. forbesi was low during the summer months, indicating that the squid had moved outside the range of the fishery, perhaps into deeper water. Abundance declined during the spawning season, which is interpreted as post-spawning mortality. Abundance declined earlier in the males than females, producing a female biased sex ratio during most of the spawning season. The two periods of recruitment are not compatible with a 1 year life cycle and single extended spawning season and explanations of this are discussed. (C) 1999 International Council for the Exploration of the Sea.

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KW - life history

KW - IRISH WATERS

KW - REPRODUCTIVE STRATEGIES

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KW - LIFE-HISTORY

KW - CEPHALOPODA

KW - LOLIGINIDAE

KW - RECRUITMENT

KW - VULGARIS

KW - MATURATION

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