Effects of stocking density on survival, growth and biochemical composition of cultured mussels (Mytilus galloprovincialis, Lamarck 1819) from an offshore submerged longline system

Abstract

AbstractThis study examined an offshore submerged mus-sel longline system, in the Black Sea, from May2009 to May 2010. The system was allowed1 year for spat collection. After a 1-year spat col-lection period, some spat collectors were leftuntouched (NS), and some spat collectors weregrazed and socked (S) for a grow-out study in May2009. The effects of stocking density on thegrowth and survival of the S and NS mussels wereexamined. The biochemical composition of the mus-sels was also determined. Environmental factorsincluding temperature, salinity, chlorophyll a, totalsuspended matter, inorganic matter and organicmatter were monitored monthly during the experi-mental period. In May 2010, the mean length andlive weight of the S and NS mussels were60.46 0.60 mm and 53.34 0.37 mm, respec-tively, and 20.50 0.50 g and 13.11 0.26 grespectively. Mean moisture and ash were 82.35 0.47% and 6.67 0.44% respectively. Mean car-bohydrate, protein and lipid were 27.74 2.40%,57.68 2.15% and 7.91 0.68% respectively.These results indicate that a submerged offshoremussel culture system in the Black Sea can becommercially convenient. In addition, stock man-agement via thinning out of the spat can consider-ably increase the marketable size of mussels,reduce harvest time and produce better growth.Keywords: Mussel, offshore, density, growth,survival, biochemicalIntroductionUnited Nations Food and Agricultural Organiza-tion (FAO) statistics indicates that mussels are oneof the most popular cultured species. The culturingof mussels has increased from 1307 thousandtonnes to 1812 thousand tonnes in the last fewdecades (FAO/Fishstat Plus 2012).For a long time, mussel farms have been limitedto sheltered coastal lagoons (Burbridge, Hendrick,Roth & Rosenthal 2001). According to Danioux,Loste and Paquotte (1997), coastal lagoons haverich and easily accessible but fragile environmentsthat have been exploited to their maximum spatialand biological capacity. These researchers havealso stated that several risk factors, at times simul-taneously, have limited the expansion of themussel farming activity in the restricted lagoonenvironment: (i) the necessary intensification ofproduction to reduce production costs; (ii) pollu-tion from industrial and domestic sources, whichproduces high mortality at times and (iii) thelimited renewal of the environment due to a lackof strong tides, which brings with it a dystrophiccrisis and anoxia risk. Inshore sites have alsoproven to have lower growth and higher diseaserates, with greater risks of contamination fromoveruse and other activities. Due to these chal-lenges, to date, the mussel production achievedhas not increased enough to meet demand. As aresult, offshore mussel culture has been suggestedas a solution to meet the growing demand(Langan 2008).