LIFE-HISTORIES OF NEOMYSIS INTEGER, AND ITS COPEPOD PREY, EURYTEMORA-AFFINIS, IN A EUTROPHIC AND BRACKISH SHALLOW LAKE

Data was collected on the population structure and fecundity of the my sid Neomysis integer and the calanoid copepod Eurytemora affinis in Hi ckling Broad, a shallow and eutrophic brackish lake, over a two-year p eriod 1988/89. Standing biomass and production rate estimates were mad e using estimates of size-specific dry weights and development times o btained from laboratory measurements, field observations and informati on found in the literature. Both mysid and copepod are capable of a ra pid response to favourable conditions and have high rates of birth, gr owth and production. E. affinis reproduces throughout the year with an estimated annual (May 1988-May 1989) production of 20 g dry wt m(-2). Copepod standing biomass was less in 1989 compared with 1988 owing to an overall reduction in copepod body-size and a reduction of size at maturity. There was a suggestion from the data that this was caused by predation from a greater number of large (>9 mm body-length) mysids i n 1989 compared with 1988. N. integer is highly seasonal in its growth with distinct peaks of recruitment in May and July. Annual (May 1988- May 1989) production of the mysid was estimated as 5.8 g dry wt m(-2). Although E. affinis is the only available prey of N. integer in the l ake, the mysid population appears independent of changes in that of th e copepod and probably avoids negative predator-prey feedback mechanis ms owing to an ability to feed on epiphytic algae.