Development of general condition and flesh water content of long-time starved mytilus edulis-like under experimental conditions
Mussels of the family Mytilidae are known for the two commercial important species in Europe, Mytilus edulis (Linneaus, 1758) (blue mussel) and Mytilus galloprovincialis (Lamarck, 1819) (Mediterranean mussel). To guarantee adequate production and quality in aquaculture general condition of the stock is routinely monitored, either by shell growth rate, soft body weight or condition index (CI). This study tested over 218 days (about 8 months) the starvation capability of blue mussels from the Baltic Sea, a low salinity environment, under fully controlled conditions. Because these mussels, genetically, represent two different species, M. edulis and M. trossulus (Gould, 1850), we examined a combination of both, as common in the western Baltic Sea. During experimental time the water temperature was kept at 15°C (±1°C) and 15 PSU (±1 PSU). Test animals physiology was verified by standard procedures, e.g. by CI, shell length growth rate and flesh water content. M. edulis-like mussel starvation capacity was high, 93 of 100 tested animals survived the entire 8 months. The CI decreased from initial 20.0 to 5.2 (loss of 74%) as well as the soft body weight retrospectively from initial 1.95 to 0.54 g (loss of 72%). The water content of the soft body increased from initial 95% to 98.4%. Regarding the total length of the mussels a decrease was found which ranged between the initial stocking sizes of the mussels (3.28 cm (±0.58 cm). We herewith demonstrate first results of the correlation of decreasing general condition, determined by CI and flesh weight, and an increase of flesh water content of blue mussels.