Résumé
The in situ reproductive activity of the copepods Centropages ponticus and Temora stylifera was investigated in autumn 2006 in the Bizerte Channel in relation to abiotic factors and phytoplankton composition. Egg production rate (EPR), hatching success (HS) and nauplii survival rate of both species were measured from samples taken daily over 45 days from September 28 to November 11 and then weekly over 8 supplementary weeks. Over this period, C. ponticus and T. stylifera had mean EPRs of 13.7 0.3 and 35.2 3.8 eggs f(1) day(1), and mean HS of 24.4 1.6 and 50.4 5.5, respectively. EPR and HS remained fairly stable for C. ponticus throughout the study period compared with T. stylifera in which reproductive traits fluctuated considerably. Changes in EPR and HS for both species resulted from environmental parameter variations and in particular, from phytoplankton composition, with slight decreasing EPR and HS observed after the important phytoplankton blooms. Centropages ponticus, a lagoon species, was able to withstand high turbidity, whereas T. stylifera, a marine species, had low EPR and HS under turbid conditions. The low HS recorded for C. ponticus, in particular in December, may be due to production of resting eggs.