Growth and mortality of mussels (Mytilus edulis L.) reared in lantern nets in Loch Kishorn, Scotland

Abstract

One-year old rope grown mussels (Mytilus edulis L.) were held in experimental lantern nets at 2 m and 6 m depths in Loch Kishorn on the west coast of Scotland. Growth, mortality and shell morphology were monitored from May 1993 to August 1994. Water temperature. salinity. transparency and food availability were also determined. These showed a clear seasonal cycle, in consequence, growth of mussels was relatively rapid from May to November and very slow during the rest of the year. Depth had a insignificant effect on shell length and tissue growth (P>0.05) due to similar environmental factors. Shell length growth and tissue growth exhibited different seasonal patterns and mussels reached marketable size of 50 mm over 2 years old. Shell morphology was similar at both depths (P>0.05) while shell weight was significantly higher at 2 m than 6 m (P<0.05). The natural cumulative mortality rate was found to be 13.6 % at 2 m and 16.7 % at 6 over the 15 months experimental period (P>0.05). Most of the mortalities were occurred just after stocking and attributed to stress due to handling of mussels.