Chlorinated Hydrocarbons: Pollutants or Indicators of Fish Stock Structure

Abstract

Chlorinated hydrocarbons are used in industry for many purposes. They are ubiquitous in the environment. Being soluble in lipids, they tend to accumulate in living organisms and consequently in the food chain. In an attempt to identify the herring stock units (Clupea harengus harengus) present in the St. Lawrence Estuary and the Chaleur Bay, we have measured the degree of contamination by some organochlorinated compounds, of herrings fished in both locations. The purpose of the study is to establish the presence of many discrete stocks units or of only one homogeneous stock brought about by large scale straying of individuals from one group to another. Adult herrings are thought to migrate to spawning areas in spring or autumn depending on whether they were born in spring or autumn. The juveniles are believed to remain close to where they were born for about three years before they join their parent stock migrations. If one area is contaminated by chlorinated pesticides, these products will accumulate in the herring fat and could possibly be used for fingerprinting if straying is negligible. The data obtained indicate that the populations studied are marked by their environment and that they probably have their own life cycle and their own migration pattern. A study of the genetic structure of these herring populations is being concurrently made.