The influence of life history dynamics and environment on the determination of year class strength in North Sea herring (Clupea harengus L.)

Authors

  • R. D. M. NASH,

    Corresponding author
    1. Port Erin Marine Laboratory, University of Liverpool, School of Biological Sciences, Port Erin Isle of Man IM9 6JA, British Isles
      *e-mail: richard.nash@imr.no
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    • Present addresses:Institute of Marine Research, PO Box 1870 Nordnes, N-5187 Bergen, Norway.

  • M. DICKEY-COLLAS

    1. Department of Agriculture and Rural Development, Agriculture and Environmental Sciences Division, Newforge Lane, Belfast, BT9 5PX, UK
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    • RIVO, Postbus 68, 1970 AB Ijmuiden, The Netherlands.


*e-mail: richard.nash@imr.no

Abstract

The inter-annual variability in year class strength (1976–2000) of North Sea herring (Clupea harengus) was investigated using Paulik diagrams based on survey data and Virtual Population Analysis. The herring life cycle was split into five stages: spawning stock biomass (SSB), egg production, larvae, fish with 0 winter rings on the otolith (0-wr), 1-wr and 2-wr. Surveys were used as indices and Paulik analysis revealed relationships between stages. In 80% of the years, year class strength reflected SSB. Poorer than expected year classes were determined during the larva to 0-wr phase, whilst stronger than expected year classes were apparently determined during the 0-wr to 1-wr stage. There was no clear relationship between survival of young stages of herring and the abundance of Calanus finmarchicus but the year class strength of 0-wr and 1-wr had a negative relationship to bottom water temperature. Lower sea water temperatures in the North Sea are associated with higher Calanus abundance. The analysis shows that the strength of aberrant year classes of North Sea herring is determined between the pelagic larval and the juvenile stages.

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