Patterns of migration in Hudson River striped bass as determined by otolith microchemistry

Ontogenetic patterns of migration in Hudson River striped bass were measured using microprobe analysis of strontium (Sr) in otoliths. Otoliths of 88 adult striped bass collected in 1994 and 1995 were analyzed for Sr content, from which past histories of habitat use-as measured by salinity-were constructed. Marginal increment analysis of otoliths was conducted to correctly assign microprobe measurements to time of year (season). We classified striped bass into distinct, cohesive migratory contingents. Contingents exhibited four dominant spatial behaviors: (1) long-term residence in the upper Hudson Estuary; (2) long-term residence in the lower Hudson Estuary and western Long Island Sound; (3) coastal habitat use; (4) abrupt mid-life habitat shifts between freshwater and saltwater environments. A freshwater-oligohaline resident behavior was observed for 94% of individuals collected near Troy Dam, located at the uppermost tidal extent of the Hudson River. As further evidence of their residency, these individuals were also highly contaminated by polychlorinated biphenyls (PCBs) due to a local point source. Striped bass may establish residence in the upper estuary because of enhanced foraging opportunities below the Troy Dam. Our study supported Clark's contingent hypothesis, demonstrating that divergent habitat use patterns occur throughout the life-spans of Hudson River striped bass. (C) 2003 Elsevier Science B.V. All rights reserved.