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Modelling the growth of herring from four different stocks in the North Sea
Heath, M.; Scott, B.; Bryant, A.D. (1997). Modelling the growth of herring from four different stocks in the North Sea. J. Sea Res. 38: 413-436
In: Journal of Sea Research. Elsevier/Netherlands Institute for Sea Research: Amsterdam; Den Burg. ISSN 1385-1101, more
Peer reviewed article  

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Keywords
    Biomass; Growth models; Larvae; Clupea harengus Linnaeus, 1758 [WoRMS]; ANE, North Sea [Marine Regions]; Marine
Author keywords
    herring (Clupea harengus, L); growth model; larval dispersal; annual variation; stock characteristics

Authors  Top 
  • Heath, M.
  • Scott, B.
  • Bryant, A.D.

Abstract
    Variations in growth of the 1961–1983 year classes of North Sea herring larvae and juveniles from four different stocks in the North Sea have been modelled in a two-stage process. First, the ERSEM transport model and a database of temperature conditions in the North Sea have been used to simulate the year-specific dispersal and timing of recruitment of larvae to a model of juvenile growth. The juvenile model was forced by temperature and continuous plankton recorder (CPR) data, and migration was modelled from survey data on the relative distribution of stock components in the North Sea. The model explains the observed differences in mean growth from hatching to 1.5 years old of herring of different stock origins over the period 1970–1981, and therefore it has been concluded that the growth differences are generated mainly by the hydrographic conditions and plankton abundance along the drift trajectory of the larvae and migration route of the early juveniles. Comparison of the time series of modelled size-at-age for juveniles from the Shetland stock with observations for the same period shows that the model explains short-term year-to-year variability in growth, correctly identifying extreme years, but fails to explain the longer-term underlying trends. The model performed best over the period 1970–1981 when population biomass was uniformly low, and deviated during 1961–1969 when biomass was declining from high levels. The inclusion of population biomass as an independent explanatory variable in the comparison of model results with the longer-term data accounts for up to 58% of the total variance in the observations. Thus, it is concluded that hydrographic and planktonic conditions in the North Sea account for the short-term year-to-year variability in growth, but the major underlying trends over the last 40 years are due primarily to density dependence.

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