Parasites as indicators of biological processes, with special reference to sockeye salmon (Oncorhynchus nerka)

Abstract

This paper reviews the applicability of parasites as indicators in studying the biology of their hosts, using examples drawn primarily from the extensive research that has been conducted on the sockeye salmon (Oncorhynchus nerka) by scientists of the former Soviet Union and Canada. The data obtained by these researchers has contributed to our knowledge of the feeding and wintering migrations of populations, i.e., local stock complexes, of sockeye and other Pacific salmon. In some local stocks of sockeye salmon, millions of fish carry such biological tags as specific parasites and scale marks that facilitate the study of their seasonal migrations. Parasite indicators are also useful in distinguishing fish of various subpopulations and trophic groups within populations of freshwater species, while an analysis of the parasite fauna of juvenile fish may reveal those fish hosts that inhabited the river in the recent geological past but are now locally extinct. In regulating subpopulations of sockeye salmon, parasites are the effect rather than the cause of mortality. The above examples are evidence of the successful application of parasites for studying biological processes.