Seasonal reproduction of the blue mussel (Mytilus galloprovincialis) from two locations in southern New Zealand

Abstract

ABSTRACT Blue mussels, Mytilus galloprovincialis, are a widespread and ecologically important species in New Zealand coastal ecosystems, yet, there is limited information on the seasonality and variability in reproduction among populations. The reproductive cycle of M. galloprovincialis was studied monthly over 1-year in two southern New Zealand populations (Aramoana (45.7787°S, 170.7037°E) and Timaru (44.3905°S, 171.2498°E)). Tissue indices were determined, and gonads examined histologically. At both sites, males and females displayed synchronous changes in condition indices and gonad indices, with both indices generally greater in the Timaru population than in the Aramoana population. Both sampling sites presented with comparable seasonality of reproduction with spawning over spring and summer months (September to February). Gametogenic development occurred over the autumn and early-winter period (March to August). Spatial differences in reproduction coincided with differences in phytoplankton food abundance (greater in Timaru), while there were only small differences in sea temperatures between sites. This study indicates the likelihood of spatial variation in reproductive biology between M. galloprovincialis populations, even across small spatial scales (<200 km).