Seasonal cycles of egg production of two planktonic copepods, Centropages typicus and Temora stylifera, in the north-western Mediterranean Sea

Abstract

Reproduction of the dominant copepods Centropages typicus and Temora stylifera was studied at a permanent station in the Ligurian Sea (north-western Mediterranean). Seasonal patterns of egg production, clutch size, egg size and female prosome length were followed from January 1998 to December 1999. Female carbon content and weight-specific egg production were compared in autumn 1998 and spring 1999. Reproductive patterns of C. typicus and T. stylifera were very similar, indicating that reproduction was affected by the same environmental factors. Reproductive activity was highest in autumn in both species and years. A second peak of egg production was observed in early summer, which was less intense in 1999 after a bloom of salps. Egg production rates reached maximal values of 33.5 and 33.3 eggs female-1 day-1 and annual means of 10.8 and 11.7 eggs female-1 day-1 in Centropages and Temora, respectively. Maximal weight-specific egg production was 0.21 day-1 in both species in November 1998, when female carbon contents were 6.7 (C. typicus) and 12.0 μg (T. stylifera). No statistical relationship between egg production and food availability or temperature was detected. Reproductive activity did not reflect the seasonal abundance patterns, with C. typicus dominating in spring and T. stylifira in autumn.