Damian Brady and Kevin Stierhoff, graduate students at the University of Delaware College of Marine Studies’ Hugh R. Sharp Campus in Lewes, received awards at the Sixth International Congress on the Biology of Fish in Manaus, Brazil, for their research on weakfish and summer flounder. The congress, which was held in August, was hosted by the Physiology Section of the American Fisheries Society and attracted more than 600 people from at least 20 countries.
Weakfish (Cynoscion regalis) and summer flounder (Paralichthys dentatus) are two economically and ecologically important fisheries in the Delaware Bay. The adult weakfish, which became Delaware’s state fish in 1981, is named after its fragile mouth tissue that is easily torn by hooks. The summer flounder is a bottom-dwelling flatfish that lies on its right side, with its eyes on its left side. Although they can grow much larger, both species reach sexual maturity at approximately 10–11 inches.
Brady, a master’s student in marine biology–biochemistry at the Lewes campus, received his award for the best oral presentation in the symposium on “Fish Locomotion.” He discussed how juvenile weakfish and summer flounder behave in response to declining levels of dissolved oxygen in the water. Low levels of dissolved oxygen can occur during the summertime in shallow coastal waters used by these fish as nursery grounds.
According to Brady, fish use specific behavioral strategies to minimize stress induced by the low-oxygen conditions. These strategies include avoidance, recovery, and acclimation. “My results are being incorporated into a computer model that will help predict the impact of decreasing water quality on populations of juvenile weakfish and summer flounder,” says Brady, who was able to “keep cool under fire” when a computer malfunction interrupted his presentation for several minutes.
Stierhoff, a doctoral candidate in marine biology–biochemistry at the Lewes campus, received a $1,000 merit-based student travel grant, which enabled him to attend the congress and present a paper on his research. A committee of fisheries biologists selected Stierhoff, among others, for the grant after reviewing the abstracts submitted by 65 students and postdoctoral scientists representing 15 countries.
During his presentation, Stierhoff showed data from both laboratory and field studies indicating that the growth of juvenile fish is adversely affected by conditions of low dissolved oxygen. In the laboratory phase of his study, he monitored the growth rates of fish using a state-of-the-art aquarium system that can control the levels of oxygen in the water. This data will be correlated to data obtained from fish living “in the wild,” which have been exposed to low dissolved oxygen conditions in Delaware’s Inland Bays during the summer nursery season.
Brady and Stierhoff’s work is part of a regional effort, which includes scientists from North Carolina and Louisiana, to predict the impact of changing oxygen conditions on the growth, survival, and distribution of several important fish species in the Mid-Atlantic region.