Seasonal dynamics in Nephrops norvegicus (Decapoda: Nephropidae) catches off the Catalan coasts (Western Mediterranean)

The commercial fishery for Nephrops norvegicus in the Western Mediterranean is mainly centred on fishing grounds on the slope at depths between 200 and 500 m. Seasonal variations in catches of this species were studied using commercial data spanning nearly a decade, as reported by fishermen's association registers of the Catalan trawlers harboured in Barcelona. Time series of monthly landings data (i.e., total kg of captured individuals) were screened with periodogram analysis revealing a six monthly-based periodicity. Form estimate analysis showed a major peak occurring in spring-summer and a minor peak in autumn. These results were evaluated by considering the effect of seasonal variations in light intensity and photoperiod duration as main environmental factors modulating emergence behaviour in the species. Other factors affecting behaviour, such as moulting and reproduction, were also taken into account. (C) 2004 Elsevier B.V. All rights reserved.