Trophic dynamics and biological cycles of fish from the middle slope of the Catalan Sea (NW Mediterranean) have been investigated. Samples were collected on a seasonal basis from 600 to 1000 m depth between February 2007 and February 2008. Gut contents of 7 dominant species from several families (Macrouridae, Gadidae, Myctophidae and Scyliorhinidae) were analysed and biological indicators (weights of gonads and livers and C/N ratios of muscle) were measured. Additionally, food availability was estimated through analyses of densities of potential prey and of indicators of organic matter sources. The fish fed upon benthos, hyperbenthos and zooplankton, each species with a distinctive diet. Macroplankton feeders changed diets in October to eating mesopelagic decapods. Benthos feeders changed diets from April to June/July by increased consumption of hyperbenthos and detritivores. Feeding intensity (F) was related with food availability (from Generalised Linear Models).Consistently, F of plankton consumers was related to the abundance of mesopelagic prey and to proxies of surface inputs (i.e. lipids in sediment). In contrast, F of benthos feeders was related to availability of benthic and hyperbenthic prey and to indicators of food both from the vertical inputs from surface production and from organic matter settled in the sediment. Vertical flux from surface production partially controlled temporal trends in gonadosomatic index. Relationships between the different biological indicators were almost species specific, but increased feeding intensity preceded gonad growth in most species. Most fishes reproduced between autumn and early spring, with different timing of reproduction observed between species feeding on similar prey

2013 Annual Symposium of the Fisheries Society of the British Isles (FSBI Symposium 2013) Deep Sea Fish Biology, 8-11 July 2013, Glasgow

Peer Reviewed