Variaciones en los índices de crecimiento de Chamelea gallina (Mollusca: Bivalvia) en las poblaciones del sur de Europa y su relación con variables ambientales

This study reports relative growth, shell length-age keys and growth performance indices (overall growth performance and phi prime) for the stripped venus Chamelea gallina from the Huelva coast (SW Spain). The morphometric relationship shell height (SH)/shell length (SL) presented isometric growth whereas SL/shell width (SW) and SL/weight (W) displayed negative allometric growth. Shell length at age was estimated through length-frequency distribution (LF) and internal shell growth bands (IB: by acetate peel method). C. gallina population consists mainly of three age classes with shell lengths around 13-15 mm for the first year, 25 mm for the second year and 30 mm for the third year. The von Bertalanffy growth curves estimated by these methods were: SLt=44.30 [1-e-0.38(t + 0.04)] (LF) and SLt=36.11 [1-e-0.79 (t + 0.45)] (IB). The OGP (LF: 4.516 and IB: 4.571) and phi prime (LF: 2.873 and IB: 3.013) values obtained in the present study are within the range of values proceeding for C. gallina populations from Gulf of Cádiz. Nevertheless, it was observed differences in growth performance indices throughout the distribution area of this species. In order to understand how the different combinations of thermohaline conditions and food availability influence growth performance, a comparative analysis of a number of case studies reported in literature (Gulf of Valencia, Ancona, Nerteva estuary, Northern Marmara Sea, Faro and Black Sea) and novel estimations presented here was carried out in relation to environmental variables. We used annual mean and annual standard deviation of the monthly means of sea surface salinity (SSS), temperature (SST) and chlorophyll-a concentration (chl-a) at the different locations from SeaDatanet (SDN, www.seadatanet.org) Joint Research Activity deliverables. Principal component analysis grouped the study areas as a function of the environmental setting and C. gallina growth indices. The first component was related with salinity, temperature and its intra-annual variability. The second component aggregated chl-a concentration, its variability and the growth index. The analysis suggests that the lowest growth performances featuring Black Sea populations were correlated with low temperature, low salinity and low chl-a that exhibit large intra-annual fluctuations. On the contrary, the highest growth performances observed in the Gulf of Cádiz occur in parallel with higher temperature (but also with a reduced seasonal range), salinity and chl-a concentration.Consejería de Agricultura y Pesca (Junta de Andalucía – European Fisheries Fund