PW11 Integrating Sublethal Responses and Ecologically Relevant Endpoints
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(PW188) Relating chronic toxicity responses to population-level effects: modeling effects on wild salmon populations.

Spromberg, J1, Meador, J1, 1 NOAA Fisheries, Seattle, WA, USA

ABSTRACT- Standard laboratory toxicity tests assess the physiological responses of individual organisms to exposure to toxic substances under controlled conditions. Time and space restrictions often prohibit the assessment of population-level responses to a toxic substance. Compounds effecting various toxicity endpoints, such as growth, fecundity, behavior or immune function, alter different demographic traits and produce different population-level impacts. Chronic effects of immune suppression, reproductive dysfunction and somatic growth impairment were examined using life history matrix models for Chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch ), and sockeye salmon (O. nerka ). Immune suppression acted through reductions in age-specific survival. Output from the chronic reproductive impact models lowered the population growth rate () to a lesser extent than impacts to survival. A 10% reduction in fecundity, survival of adults during the spawning migration, and spawning behavior of adults, all produced a similar for the respective species. Growth reduction models incorporating effects to both survival and reproduction produce greater effects than each would individually. Stressors effecting similar changes in often produced diverse changes to the age distribution. Sensitivity and elasticity analyses show that changes to the first-year survival rate produce the greatest per unit effect on . In addition, alteration in abundance of mature females also strongly influences . Differences observed between species showed that the number of reproductive ages and time to reproductive maturity were important components in population-level responses. These results indicate the importance of linking toxicity measurement endpoints to the demographic traits that they affect, and help generate toxicity tests that are more relevant for the focal species. Further models are planned for chum salmon (O. keta ) and pink salmon (O. gorbuscha ). Life history modeling provides a useful tool to develop testable hypotheses regarding impacts on specific populations as well as to conduct comparisons between populations.

Key words: chronic toxicity, life history modeling, salmon, population-level effects

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