Coexistence in North Sea fish communities: implications for growth and natural mortality
1 National Institute of Aquatic Resources, Technical University of Denmark, Charlottenlund Slot, DK–2920 Charlottenlund, Denmark
2 Norwegian College of Fishery Science, University of Tromsø, N–9000 Tromsø, Norway
3 DFO Science Advisory Secretariat, Department of Fisheries and Oceans, 200 Kent Street, Ottawa, Ontario, Canada K1A 0E6
4 Institute for Marine Resources and Ecosystem Studies, PO Box 68, 1970 AB IJmuiden, The Netherlands
Correspondence to H. Gislason: tel: +45 33963361; fax: +45 33963333; e-mail: hg{at}difres.dk
Gislason, H., Pope, J. G., Rice, J. C., and Daan, N. 2008. Coexistence in North Sea fish communities: implications for growth and natural mortality. – ICES Journal of Marine Science, 65: 514–530.For a fish community to persist over time, all species must be able on average to replace themselves on a one-for-one basis over their lifetime. We use this principle and a size-based equilibrium model where asymptotic length is used as a functional trait to investigate how natural mortality should scale with size within and across pelagic and demersal species of North Sea teleosts. The model predicts natural mortality to scale with body length raised to a power of –1.66 at current levels of exploitation. Additionally, natural mortality of demersal species should be proportional to asymptotic length raised to a power of 0.80, so generating a higher natural mortality at a given length for large species than for small ones. The model also suggests that the exponent in the scaling of the von Bertalanffy growth parameter K with asymptotic length should be more negative for pelagic than for demersal species. We test our results by analysing independent estimates of predation mortality, the scaling of maximum recruitment per unit of spawning-stock biomass with asymptotic length, and the general relationship between K and asymptotic length for demersal and pelagic families of fish. All tests are consistent with our modelling results.
Keywords: coexistence, fish communities, growth, life history, natural mortality, net reproductive rate, replacement, size-based model, size structure, stock–recruitment
Received 22 February 2007; accepted 5 January 2008.
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