A Qualitative and Quantitative Study of the Plankton of the Quoddy Region in 1957 and 1958 with Special Reference to the Food of the Herring

Abstract

Investigations of the composition, abundance, and distribution of plankton communities within the Passamaquoddy region of New Brunswick and Maine were carried out in 1957 and 1958. Studies of the food of herring and possible relationships between zooplankton abundance, feeding activity, fat content, and catches of herring were included in the program. Similar quantities of zooplankton were found outside Passamaquoddy Bay and in Cobscook Bay. Slightly smaller volumes were taken in the passages into the Bay, but only one-fifth as much was taken in samples inside Passamaquoddy Bay. Differences in zooplankton abundance suggest incomplete mixing of outside waters with those of Passamaquoddy Bay. The smallest volumes of zooplankton were taken in the spring and the largest in the summer months. Overall zooplankton volumes were much higher in 1958 than in 1957.There was evidence that herring were feeding in the upper water layers. A period of low feeding activity from March to August was followed by a period of active feeding from September to November. There was a positive correlation between feeding activity and fat content of herring but no relationship between quantities of zooplankton and feeding activity could be established. Nor. was it possible to demonstrate any relationship between zooplankton volumes and catches of herring over a period of 10 years.Higher zooplankton volumes are foreseen for Passamaquoddy Bay after the dams are built. Volumes in Cobscook Bay are expected to reach values similar to those of Passamaquoddy Bay while those outside should remain unchanged.