Growth parameters of deep-water decapod crustaceans in the Northwestern Mediterranean Sea: a comparative approach |
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Authors: | J B Company F Sardà |
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Institution: | (1) Institut de Ciències del Mar (CSIC), Passeig Joan de Borbó s/n, E-08039 Barcelona, Spain Fax: 0034 (0) 93 221 7340 e-mail: batista@icm.csic.es, ES |
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Abstract: | Relative and absolute growth were studied in 17 species of deep-water decapod crustaceans, spanning nine families of six
different infra-orders, in the Northwestern Mediterranean Sea. The overall maximum abundance of these species lay between
200 m and 750 m (i.e. upper- and mid-slope species). Relative and absolute growth rates were compared by contrasting the slopes
of the size–weight relationships for the different species and calculating the von Bertalanffy growth-equation parameters
asymptotic length (L
∞
) and growth rate (k). The size–weight relationships differed significantly as function of the species' life habits. The results revealed a significant
decrease in weight relative to size in mesopelagic species (which carry out diel vertical migrations), an almost isometric
relationship between size and weight in the less mobile nektobenthic species, and a significant increase in weight relative
to size in strictly benthic species. The mean allometric coefficient for each group increased significantly from mesopelagic
to benthic species. However, no general trend was observed in the growth-performance index, Φ (an index used to compare absolute
growth rates between species, as a function of habit and depth of maximum abundance for all species combined), suggesting
that the deep-water decapod crustaceans studied have similar absolute growth rates. Nevertheless, comparison of growth-parameter
and growth-performance index values within families did reveal differences. Mesopelagic species of the families Sergestoidae
and Pasiphaeidae showed slightly increased growth rates with increasing depth of distribution. Nektobenthic species of the
genus Plesionika followed a trend opposite to that shown by mesopelagic species, with a higher growth rate for the shallowest-dwelling species
(P. heterocarpus) than the deepest-dwelling species (P. acanthonotus). Taking growth as one of the major components of an organism's energy budget, the growth rates for the decapod crustacean
species in this study were significantly lower than those reported in the literature for shallow-water penaeid crustacean
species (which are distributed in higher-temperature habitats than deep-water Mediterranean crustaceans) and higher than those
reported for mesopelagic myctophid fish species. Hence, the well-defined growth trends shown by deep-water decapod crustacean
species in the Northwestern Mediterranean Sea, compared to the less well-defined trends in the other taxa, is discussed in
the framework of the overall dynamics of their ecosystem.
Received: 25 May 1998 / Accepted: 27 September 1999 |
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