Hooked on fish

Kevin Stierhoff still remembers the day he caught his first fish. Photographs capture a young boy with an unmistakable gleam in his eye and a huge grin on his face. The pride in his accomplishment is evident.

From that day on, Stierhoff says, he was hooked on fish. Now a doctoral candidate in the College of Marine Studies, he credits his big brother and his dad, both avid fishermen, with sparking that interest. They showed him how to bait his hook, cast his rod and reel one in. It wasn’t long before Stierhoff could identify most of the fish he caught. His interest continued, and soon he was studying marine biology at Salisbury University in Maryland.

After graduating in 1998, he went fishing for another mentor and found one in Timothy Targett, professor of marine biology-chemistry at UD. Under Targett’s guidance, Stierhoff has researched the effects of low dissolved oxygen levels on fish with impressive results, conducting research in Delaware and in Japan, as well as presenting the results of his work at two international conferences.

Stierhoff says his “landing” at the College was a bit serendipitous. “Just by luck, I found out that Tim was beginning a new line of fisheries research and needed a lab technician,” he says. “Tim had already gotten several applications, and he actually discouraged me from applying, since he felt that he had enough applicants.”

Still, Stierhoff persisted and asked Targett if he could send him his résumé. That initiative, coupled with his enthusiasm, convinced Targett that he was the right person for the job. Stierhoff and Targett say they hit it off that summer, and a few months later when Stierhoff began applying to graduate school, UD was his first choice.

“I liked Tim’s style. He allowed me to pursue my interests, but he was always there when I needed him,” Stierhoff says. “I was very interested in Tim’s research, which I had already begun working on.”

Targett says he never regretted his decision to hire Stierhoff and has enjoyed mentoring him over the years. He has watched Stierhoff evolve from a novice in his lab to the most senior member of his research team.

“Kevin is committed to his work and very persistent,” Targett says. One year, Targett’s Thanksgiving Day dinner was interrupted by a call from the lab. It was Stierhoff; his student had been spending the holiday trying to resolve a feeding problem with the fish.

Stierhoff’s research at UD has focused on the effects of low levels of dissolved oxygen (hypoxia) on the juvenile stage of key mid-Atlantic fish species, including the summer flounder (Paralichthys dentatus) and weakfish (Cynoscion regalis). Low levels of oxygen typically occur during the summertime in shallow coastal waters, such as Delaware’s Inland Bays.

Even at sub-lethal levels, hypoxia can affect the growth, survival and distribution of fish that use these waters as nursery grounds. The results of Stierhoff’s research will further the understanding of the ecological impacts of low oxygen on estuarine fish, as well as assist management officials in developing strategies to protect them.

A crucial part of the research was finding a way to measure the growth of juvenile fish under different levels of dissolved oxygen. “The growth of fish is affected by many variables, such as temperature and light intensity,” Stierhoff says. “To find out how one of those variables—dissolved oxygen, in this case—affects fish growth, you need to design your experiments so that this variable can be isolated and precisely controlled.”

To accomplish this task, Stierhoff helped create an elaborate aquarium system that has the capability to maintain constant oxygen levels, as well as mimic or replicate the natural fluctuations that occur in shallow coastal systems over the course of a day.

Targett says Stierhoff was instrumental in constructing the aquarium system, from building the structures to plumbing the tanks to connecting the wires that run all the individual components. This initiative by a student is something that Targett says he encourages.

“I try to approach my relationship with my students not so much as a professor versus a student, but as a colleague who expects them to have good ideas and do good things,” he says.

The aquarium system is one of a kind and has attracted attention from scientists throughout the world. The levels of dissolved oxygen in the water are controlled through a computer, which does all of the monitoring and adjustment as well as recording the data that otherwise would require a person to be in the lab around the clock.

In addition to conducting research in Delaware’s Inland Bays, Stierhoff assisted Targett on a collaborative project in Japan.

He also has presented the results of his research at the fifth International Flatfish Symposium on the Isle of Man and presented a paper in Brazil at the sixth International Congress on the Biology of Fish. The travel has been invaluable, the professor and student say, because it opens doors for future collaborations with other researchers.

Early this year, Stierhoff began a postdoctoral appointment with the University of California and the Southwest Fisheries Science Center Laboratory.

“There is a lot of oneself invested in one’s students, and now for Kevin to have such a good career opportunity is very rewarding,” Targett says. “In education, those are some of our best rewards—having good students who go on to do good things.”

—Kari K. Gulbrandsen, EG ’91M