Seasonal growth and allometric indices of the mussel Mytilus galloprovincialis Lamarck, 1819, from the coastal zone of the Black Sea in relation to environment quality, mollusc sex and shell coloration

Abstract

For the first time, experimental data on the seasonal shell growth rate and its allometric indices H/L (ratio of height to length), D/L (ratio of width to length) of M. galloprovincialis are presented in relation to environment quality, mussel sex, size and shell coloration. In this field experiment mussels of two size groups with the shell lengths of 35 and 60 mm were selected. Mussels of both sizes were placed in cages and deployed in a conditionally clean water area of mussel-and-oyster farm and in a harbour under anthropogenic impact. The length (L), height (H) and width (D), of the mussel shells were measured every season. In the 35-mm group, it was noted that in the post-spawning winter period males grew faster than females and the growth rate of mussels with the black shell coloration was higher than that of mussels with brown shells. For mussels of both sexes with the shell length of 35 mm from the conditionally clean water area, the growth rate was three times as high as for males and females from the polluted area; in the 60-mm group, it was twice as high. Mussels with the shell length of 35 mm were more sensitive to unfavorable conditions, which fact renders them more efficient in environmental monitoring. The most indicative was the H/L index, which can be adopted as a water area pollution index. Environment quality (including pollution, food availability and hydrodynamic conditions) of the compared water areas had a significant impact on the shell length growth and allometric indices of mussels.