Distribution, standing stock, growth, mortality and production of Strongylocentrotus pallidus (sea urchin) in the northern Barents Sea.

Median values at single stations varied from 14 to 46 mm, showing a significant inverse relationship to water depth. Biomass, estimated by combining photographic abundances, size frequencies and a size-mass function established with trawled specimens, ranged between <0.1 and 3.0 g ash-free dry mass m-2, averaging about 1.0 g ash-free dry mass m-2. An analysis of skeletal growth bands in genital plates was carried out with 143 trawled individuals ranging in test diameter (D) from 4 to 48 mm.

Assuming these bands to represent annual growth marks, the ages of the specimens analysed ranged between 3 and 42 years. A von Bertalanffy function was fitted to size-at-age data to model individual growth pattern (D∞ = 102.3 mm, k = 0.011 year-1, t0 = 0.633 year). The annual mortality rate Z of the population in the northern Barents Sea was estimated from a size-converted catch curve to be 0.08 year-1.

Applying the weight-specific growth rate method, the average P/B ratio and the mean annual production of this population were estimated as 0.07 year-1 and 0.076 g AFDM m-2 year-1, respectively. In conclusion, S. pallidus is characterized by slow growth, low mortality, high longevity and low productivity. Because of its relatively high biomass, it is considered to contribute significantly to total benthic standing stock and carbon flux in the study area.