Condition and recruitment of Aristeus antennatus at great depths (to 2300 m) in the Mediterranean: environmental links and implications for management

XIX Iberian Symposium on Marine Biology Studies (SIEBM), 5-9 September 2016, Porto, PortugalDepth relationships and seasonal trends in the biological condition and recruitment of the red shrimp Aristeus antennatus have been analyzed along down to 2300 m, over all the slope in the Balearic Basin (western Mediterranean). The analysis is based on a composite year (2008-2012 period) and identifies environmental causes of the trends. We found good reproductive and general biological condition of A. antennatus (Gonado-somatic index, GSI) at 800-1300 m in summer (June-July), depths below the fishing grounds. Mating and spawning were at depths below the more saline waters of the Levantine Intermediate water mass. Recruits Smallest juveniles (recruits, ca. 1 yr age) were exclusively distributed below 1000 m, associated with high near-bottom O2 concentration, low turbidity and high C/N in sediments implying favourable trophic conditions. A seasonal migratory pattern is suggested for females, which move shallower to the upper slope during periods of water-mass homogeneity (autumn-winter) to feed in canyons, increasing their energy reserves (hepatic gland weight, HSI). Females move downslope (800-1100 m) to spawn (high GSI) during periods of water mass stratification (late spring-summer). HSI of A. antennatus females decreased linearly with depth down the slope in February and in October-November, i.e., before and after the reproductive period. This nutritional condition of females in these periods is consistent with more consumption of benthic prey (ophiuroids, polychaetes, Calocaris macandreae) at the canyon heads (Cartes, 1994) in late autumn and winter. Our results confirm/suggest: i) how important it is to study the biology of deep-sea species over the whole depth range they inhabit and not only over fishing grounds, and ii) that changes in environmental conditions linked to the progressive warming of Mediterranean Deep Water (WMDW) with a parallel increase of salinity could provoke a decrease of O2 in water masses at below 1000 m, affecting A. antennatus recruitment and its life cycle, which is extensible to other deep-sea speciesThis study was financed within the framework of the MICYT projects BIOMARE and ANTROMARE (CTM2009-12214-C02-01-MAR), and it was also possible thanks to the multi-methological design work contained in proposals like TRENDSEAS (CTM2014-54018-C3)Peer Reviewe