Sea lamprey parasitism on lake trout has been attributed to population decline by directly causing an increase in mortality rates of lake trout populations. Indeed, several studies have estimated how lamprey predation affects mortality of lake trout and have included such effects into population models. Less understood are the sub-lethal effects of sea lamprey parasitism on lake trout. Are survivors of sea lamprey parasitism able to function ecol-ogically as expected? If not, we are likely underestimating the full effects of sea lamprey parasitism on lake trout pop-ulation dynamics. Preliminary data indicate that a modest level of lamprey scarring can be associated with reduced hormone levels, reduced lipid levels and reduced fecundity. Current stock assessment models used to generate lake trout harvest quotas rely on accurate fecundity schedules to estimate spawning stock biomass per recruit (SSBR) values. If female survivors of parasitism are mistakenly assumed to be equivalent to mature-reproductive fish, this could cause an over-estimation of SSBR, which would over-estimate harvest quotas. Furthermore, we can also reas-onably assume that the condition and energy content of the lake trout are reduced due to sea lamprey parasitism, and this could result in slower growth and reduced fecundity. Reduced fecundity, and subsequently lower spawning stock biomass, could be attributed not only to smaller size at maturity but also to reduced energy stores and impaired endo-crine function. We propose to estimate the sublethal effects of parasitism (delayed maturity, reduced fecundity and growth) based on molecular and physiological biomarkers and to incorporate these effects into population models that will quantify by how much we are underestimating the effects of lamprey predation on lake trout populations.
ESTIMATING THE SUBLETHAL EFFECTS OF LAMPREY PARASITISM ON LIPIDALLOCATION, REPRODUCTION AND POPULATION DYNAMICS OF LAKE TROUT
Great Lakes Fishery Commission $ 108,800.00USDEstimates
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