On the ecology of the dragonet Callionymus lyra L. in the southern North Sea

Abstract

The present paper evaluates data collected in the southern North Sea between 1972 and 1984 on geographical distribution, density, growth, mortality, biomass, production and food requirements of the dragonet Callionymus lyra L. Catches never exceeded 1500 individuals per 10 000 m 2 and the dragonet showed a clear pattern of abundance with highest densities in the coastal zone and decreasing numbers going offshore. Mortality rates appeared to be rather constant over the age groups with z = 0.55 y −1. The dragonet population mainly consisted of 1, 2 and 3-year-old individuals with a mean length at the end of the year of 7.5, 15 and 19 cm, respectively. Production values were at least 159 g AFDW·10 000 m −2·y −1. Predation pressure exerted by the dragonets amounted to at least 795 g AFDW·10 000 m −2·y −1. The correspondence between the von Bertalanffy growth curve in this study and that of 1948 ( Chang , 1951) suggests absence of effects of eutrophication in the area on the growth of dragonets between 1948 and 1980s. The main difference with 1948 was the absence of large individuals, probably as a result of increased fishery in the area.