Overview of the biology of Flexopecten glaber in the North Western Adriatic Sea (Italy): A good candidate for future shellfish farming aims?

摘要

To assess the potential for rearing in smooth scallops (Flexopecten glaber) from the North Western Adriatic Sea, various biological traits were studied in both fished and reared individuals. Condition and gonadosomatic indices, gonadic cycle, biochemical components and histopathological conditions were investigated in adults from commercial fishing. Throughout two consecutive years, juvenile scallops were collected by means of artificial collectors and maintained in an experimental rearing facility. Growth, onset of sexual maturity, size/age at first maturity were investigated in reared individuals. In fished scallops, spawning and resting periods occurred mostly between July and September and from October to December, respectively. Gonadosomatic index and condition index increased from January to June and decreased from July to October; these main variations corresponded to gametogenesis and spawning, respectively. In both somatic and gonadic tissues, proteins were the major biochemical component (about 80%), with no evident seasonal variation. In somatic tissues, total carbohydrates were always higher than lipids; in gonads, lipids exceeded total carbohydrates for most of the year, peaking at maximum values when only mature or spawning animals were found. Observation and quantification of abnormal features of gonadic tissues, like oocyte atresia, haemocytic infiltration, neoplasia, and presence of parasites, suggest the overall good health conditions of scallops in the study area, no serious threat due to diseases being evident. In reared scallops, sexual maturity was attained within the first year, thus indicating F. glaber as a fairly early maturation species compared with other scallop species. The first maturity event occurred in about 330 days from the immersion of the collectors, at mean shell height values ranging from 22.4 to 25.1 mm, well below the minimum landing size (40mm) established by the EU for queen scallop fishery in Atlantic waters. Appreciable growth rates and a relatively short grow-out period, precociousness in maturation, high availability of wild spat, easily and inexpensively collected, absence of diseases and other mortality factors are promising elements to introduce the cultivation of F. glaber in the North Western Adriatic coastal waters.