Spawning and Exploitation of Atlantic Herring ( Clupea harengus ) at Escuminac in the Southwestern Gulf of St. Lawrence, Spring 1983

Abstract

An Atlantic herring (Clupea harengus L.) spawning bed at Escuminac, Miramichi Bay, in the southwestern Gulf of St. Lawrence was surveyed by scuba divers in May 1983. The bed extended 2 200 m along the shore with a mean offshore width of 400 m. Herring were distributed over a depth range of 0.8-3.3 m. The substrate consisted of bedrock and rubble, with Irish moss (Chondrus crispus) and, to a lesser extent, rockweed (Fucus sp.) being the major macrophytes. Bottom temperature ranged from 6.5° to 9.3°C during the incubation period which lasted for 14-16 days. Non-viable herring eggs constituted about 5% of those examined for stage of development in late May. Intensity of egg deposition varied from a few scattered eggs to patches which were 4-5 layers deep and was significantly correlated with algal abundance. Mean density of eggs over the entire bed about 10 days after spawning was nearly 25 000 eggs per m2. After adjustment of the estimated deposition of eggs for loss due to predation by fish, use of mean fecundity and mean weight values indicated that the total number of eggs on the spawning bed were produced by approximately 930 400 mature herring (or about 210 tons). The catch of mature herring off Escuminac from the prespawning and spawning concentrations in 1983 was about 4 400 tons, which implies an exploitation rate of 95%. Aerial photographic surveys of fishing activity off Escuminac in 1983 indicated very large concentrations of herring gillnets on and around the spawning ground, and it is believed that these nets caught most of the mature herring before they could spawn.