Age- and Sex-Dependent Migrations of Striped Bass in the Hudson River as Determined by Chemical Microanalysis of Otoliths

Abstract

Patterns of habitat utilization and migration of Hudson River striped bass,Morone saxatilis, were estimated using otolith microchemical analysis to chart age- and sex-dependent movements. Otoliths from 25 males and 25 females were analyzed for seasonal and age-specific patterns in strontium: calcium level. These levels were converted into salinity estimates based upon a relationship derived from experimental studies. Seasonal patterns in salinity habitation indicated annual up-estuary migrations in mature age-classes of males and females, and may represent spawning migrations. Early emigration of young striped bass (<3 yr old) into polyhaline and euhaline waters was observed for both sexes, but females tended to reside at higher salinities throughout their life span. Otolith microchemical analysis indicated that 68% of the sampled females and 28% of the sampled males spent significant portions of their lives in euhaline coastal waters. A positive relationship between down-estuary movements and age was observed for both sexes, supporting the hypothesis of size-related dispersion and anadromy in striped bass populations. Individuals collected during the same season or from the same segment of the river had similar lifetime salinities. This result suggests that group cohesion (schooling) could persist for substantial periods of an individual’s life span. The most cohesive group was fall-collected males, which may reside permanently in fresh water and estuarine waters. Cohesive migratory groups would have important implications for investigations on effects of contaminants and fishing pressure on Hudson River striped bass.