Diet and feeding of Neomysis mercedis Holmes (Crustacea, Mysidacea) from the Fraser River Estuary, British Columbia

Abstract

N. mercedis in the Fraser River estuary is a predator on the meiobenthos, especially harpacticoid copepods. No clear seasonal differences are seen in its use of food resources. The consumption rate of N. mercedis feeding from natural sediments varies with body size and temperature as C = 3.81 W0.782 T0.515, where C is the consumption rate of meiofauna in micrograms dry weight per animal per hour, W is the mysid size in milligrams dry weight, and T is the temperature in degrees Celsius. The weight dependence of the ingestion rate is identical to that of the metabolic rate but the temperature dependence is significantly lower. The mysid selectively feeds on the organic fraction of the sediments but only 1/2 of the ingested material (by weight) is of biological origin. In mid-April, mysid predation may result in a 12% per day mortality rate on harpacticoid copepods. Thus, mysid predation may strongly influence meiofaunal densities.