Life cycle, growth and production in estuarine populations of the polychaetes Nereis virens and N. diversicolor

Life cycle, growth, mortality and production of the polychaetes Nereis virens and N. diversicolor were studied in Norsminde Fjord, Denmark. When 3 yr old, N. virens showed synchronous spawning induced at new moon in April when water temperature was 10–12°C. Nereis diversicolor showed a prolonged spawning during early spring and summer at an age of 12–18 months. Average weight‐specific growth rate for N. virens and N. diversicolor were O.0062 and 0.0050 d −1 , respectively; showing a reduced rate with age. Annual mortalities of 76–77% and 98%, respectively, reduced N. virens to 1.2–1.4% and N. diversicolor to 1.2–2.3% of the initial population at the time of spawning. Annual production of N. virens and N. diversicolor was 23.73 and 27.17 g AFDW m −2 , tantamount to an annual turnover (P/ B ) of 2.52 and 2.60, respectively.