Distribution of flatfish eggs in the 1989 egg surveys in the southeastern North Sea,and mortality of plaice and sole eggs

From January to July 1989 eight egg surveys were carried out in the southeastern North Sea. The first three surveys were designed to estimate the egg production of plaice (Pleuronectes platessa) and cod (Gadus morhua). The other five surveys were aimed at the eggs of sole (Solea solea) and horse mackerel (Trachurus trachurus) Of a selection of the samples collected in 1989 all fish eggs were identified to species. This paper presents data on the distribution, timing and intensity of spawning of the flatfish species plaice, flounder (Platichthys flesus), dab (Limanda limanda), long rough dab (Hippoglossoides platessoides), sole, solenette (Buglossidium luteum), turbot (Scophthalmus maximus) and scaldfish (Arnoglossus laterna).Egg mortality was studied in plaice and sole and compared to previous estimates. Plaice egg mortality in 1988 and 1989 was higher than in 1987, coinciding with higher ambient temperatures. Egg production in sole was recorded earlier in the year in 1988 to 1990 than in 1984, and at lower ambient temperatures. Sole egg mortality rates were shown to be lower in 1988 to 1990 than in 1984.