Seasonal Ingestion Rates of Pontopareia hoyi (Amphipoda) in Lake Ontario

Pontoporeia hoyi in Lake Ontario do not feed continually, their guts averaging 48% full. Feeding intensity of immature amphipods follows the changes in percent of carbon of the settling organic matter, being highest during the late spring and fall. Gut filling time ranged from 6.7 to 3.4 h at 5 and 14 °C Daily ingestion of organic matter ranged from 0.05 g∙m−2∙d−1 at the deepest station sampled (125 m) to 0.17 g∙m−2∙d−1 at the shallowest (35 m). The organic matter ingested by the Pontoporeia present represented 8.8 and 7.9% of the average daily rate of organic matter deposited at these two stations respectively. The lakewide estimate of the organic matter consumed by Pontoporeia in Lake Ontario was about 19 g∙m−1 during 1981 and 21 g∙m−2∙yr−1 during 1982.