Shell Mass, Biomass, Condition, and Reproductive State of the Invasive Bivalve Mytilopsis leucophaeata (Conrad, 1831) (Dreissenidae)

Abstract

Basic information on shell dimensions, calcimass and periostracum mass, biomass, and the relation between the condition and reproduction of Mytilopsis leucophaeata was analyzed for a population in the North Sea Canal, the Netherlands. The mean dry flesh weight of individuals with a mean shell length of 12.5 mm showed a peak at the end of June. The mussel reached the highest mean dry flesh weight in the month before the spatfall started. The gonad index (GI) was high in June, followed by a period of decrease until September and a period of increase until November. The condition index (CI) peaked in June and decreased during the remainder part of the year. The range of CI was highest in May when the gonadal development progressed and was smallest in June when the gonadal development was complete. The CI decreased during the rest of the year. Quantile regressions showed a highly significant relation between CI and shell length. Based on the regression coefficients, the CI was maximal at a shell length of 11.4 mm and minimal at 12.5 mm. Condition index variation was highest within a shell length range of 10-15 mm.

One more place to call home: the invasive bivalve Mytilopsis leucophaeata reaches the Maricá-Guarapina lagoon system (Rio de Janeiro, Brazil)

“…The highest mean density of M. leucophaeata was recorded at the station 14 (PVC deck), reaching 43,375 ± 46,537 specimens/m 2 (one replicate with up to 95,225 specimens/m 2 ), contrasting with 2,833 ± 823 specimens/m 2 and 5,925 ± 2,606 specimens/m 2 from stations 17 (soft sediment) and 21 (rocks), respectively (Figure 7). There is a large proportion of juveniles at station 14, instead of more adults and few juveniles at station 17 (Figure 8), regarding the size of 10 mm as conservative for the beginning of the reproductive stage for the 'North lineage' (Van der Gaag et al 2020) and yet unknown for the 'tropical lineage'.…”