Fecundity and biomass of plaice (Pleuronectes platessa L.) in the northern Celtic Sea

Fecundity was measured of plaice sampled in the outer Bristol Channel, due to spawn in 1990, and of plaice from off south-eastern Ireland, due to spawn in 1992. Different regression relationships of fecundity with length were found but the absolute fecundity was similar in both locations: fecundity at 35 cm was 105 000 in the Bristol Channel and 115 000 off Ireland. These values are also similar to estimates from Cardigan Bay in 1989 and in the Irish Sea and Cardigan Bay in 1953, and the fecundity off Ireland is not greater than was found in 1959. The large changes in fecundity seen in North Sea plaice have not been detected in western populations. Mean egg-production-based estimates of the biomass of mature female plaice that spawned in the outer Bristol Channel in 1990 are 1374-1580 t(C.V. 11%). This is consistent with the current ICES-tuned VPA assessment of the plaice in Divisions VIIf + g, although methods of comparison risk significant bias.