Herring Recruitment in Maine Coastal Waters: An Ecological Model

Abstract

An ecological model of larval herring survival in Maine coastal waters demonstrated, quantitatively, that herring recruitment is the result of a complex interaction of many processes, no one of which is truly dominant. Herring larval abundance measured on a series of spring cruises from 1965 to 1973 was used to estimate survival. Two-year-old recruitment to the Maine sardine fishery was established in the larval stage in some years, but not until the brit stage in other years. A sensitivity analysis of the model showed that food supply in winter and autumn and the quantity and distribution of spawning were primary factors controlling recruitment in years when the larval stage was critical. Density-dependent predation on brit by opportunistic pelagic and demersal predators was proposed as a mechanism determining recruitment in years of high larval herring survival. In the model, the Maine coast was divided into four spatial sectors of different area and characteristics. The western coastal waters from the headlands to the 100-m isobath made the largest contribution to recruitment in most years. Maine herring management regulations that limit fishing on spawning aggregations of herring should increase larval herring survival along the Maine coast in most years.