Effects of temperature and energy use on fish passage and spawning success of American shad
American Shad (Alosa sappdissima) are the most numerous and economically important anadromous species on the east coast of the United States. Yet in many river systems their populations have experienced declines, primarily due to the impacts of dams and habitat loss. Although fish passage facilities have been constructed to mitigate the impacts of dams, many of these have not provided adequate passage success for self-sustaining populations or populations at levels that meet management goals. The negative impacts of fish passage facilities may be exacerbated by high temperature late in the migratory period, a phenomenon that is likely to become worse with higher freshwater temperatures associated with climate change. Migratory delays associated with low rates of dam passage appear to substantially aggravate this effect. Previous research has established that energetic considerations are a critical component of adult American shad migration, spawning success and itero/semelparity. Modelling studies have found that energetics is an important issue for understanding the influence of temperature on migration, spawning success and iteroparity in American shad. Key components of these models have relied on information from other species because the influence of temperature on maximum sustained swimming capacity, burst swimming capacity and oxygen demand of American shad are currently unknown, leading to great uncertainty in model predictions.
We will use a combination of field and laboratory approaches to understand the influence of temperature on migration and spawning success of American shad. The overall goal of the project is to determine the impacts of temperature, energy use, and efficiency of fish passage facilities on the spawning success of American shad. To achieve this goal this project will pursue the following specific objectives:
1) Determine how thermal conditions experienced during migration affect energy use and swimming capacity, 2) Examine how energy use by migrating shad affects migration and spawning success and 3) Discover if there are significant energetic differences between early and late run fish and between sexes that affect migration and spawning success. These results will be used to quantify effects of dam-induced delays, cumulative effects of dams and the effects of climate change on American shad migration, spawning success and population sustainability. The findings can be applied by managers to determine minimal performance criteria for dams and predict the impacts of annual and climate-induced changes in temperature on the sustainability of American shad populations.
Ted Castro-Santos, USGS Conte Anadromous Fish Research Center, Turners Falls, MA, USA.
Dr. Shannon Bayse, USGS Conte Anadromous Fish Research Center, Turners Falls, MA, USA.
Funded by USGS Science Support Program