Secondary production of a nereid species, Perinereis aibuhitensis in the intertidal mudflat of the west coast of Korea

Abstract

For effective management of marine polychaete resources, it is necessary to obtain information about the standing stock, population dynamics, growth and mortality rates, and annual production of the target species. To investigate annual production of Perinereis aibuhitensis in an intertidal zone of the west coast of Korea, monthly sampling was conducted for 15 months from September 1990 to November 1991. Mean population density of P. aibuhitensis was 129 indiv.m(-2) and mean biomass was 77.9 g (wet).m(-2) in silty sediment. The maximum density was 230 indiv.m(-2) and occurred in July, and the maximum biomass, 134.8 g (wet).m(-2), occurred in May. The minimum density and biomass appeared in December 1990 with 52 indiv.m(-2) and 34.7 g (wet).m(-2), respectively. The Perinereis population consisted of five cohorts distinguishable from size frequency distributions. Four cohorts appeared during the main recruitment period of July to September, and an additional cohort appeared in March. For some cohorts the life span of most individuals was less than 1 year. The instantaneous growth rates of younger cohorts were in the range of 0.68.month(-1) to 0.81.month(-1) while those of older cohorts were lower and ranged from 0.1.month(-1) to 0.2.month(-1). Seasonal change in the growth rate was found with rapid growth in summer. Total mortality rate of cohorts was in the range of 0.3.month(-1) to 0.4.month(-1), which corresponded approximately to 3.6.year(-1). The annual production of P. aibuhitensis was estimated as 267.6 g (wet).m(-2).yr(-1) or 29.4 g (dry).m(-2).yr(-1) or 25.4 g (AFDW).m(-2).yr(-1), and the P/B ratio was 3.4.