Bioenergetics of sauger in Watts Bar Reservoir

This 17-nionth study describes the energy budget of sauger [Stizostedion canadense (Smith)] in Watts Bar Reservoir, Tennessee, in order to assess the effects of prey fluctuations on that major predator. Direct field determinations of consumption and laboratory determinations of metabolism are organized in the balanced energy equation of Winberg (1956) to predict the growth in energy value of typical sauger in two year classes. The Winberg equation is modified to include the energetic costs of specific dynamic action and the efficiency penalty of catabolizing body energy stores to realistically reflect energetics principles. Directly measured caloric growth and predicted growth over the growing season (March-October) agree within 5.0 to 13.2% for the two age classes modeled, thus verifying the model application. Predicted and observed gains over the winter were much more divergent, suggesting that the physiological assumptions of the balanced energy equation are invalid for describing the winter energetics of sauger. Further investigations of the growth efficiency of percids at low temperatures, or observations of field activity in the winter, or both are warranted.

Watts Bar sauger grew quickly in comparison to other populations. Modeling indicated that this rapid growth was the result of storing energy obtained by winter predation upon threadfin shad (Dorosoma petenense) and young-of-the-year gizzard shad (Dorosoma cepedianum), of heavy feeding upon shad in early summer, of prey switching to species of equal or superior energy value, and of maintaining minimum levels of metabolic energy expenditures. In early summer sauger fed heavily on vulnerable shad which were concentrated in coves to spawn. Predation upon shad was again very heavy when winter cold stress rendered them vulnerable. Cold stressed shad are also susceptible to impingement upon powerplant intake screens and shad predation by sauger was correlated with impingement of shad at Kingston Steam Plant both winters of study.