Attitude Goes a Long Way

Brook trout behaviors could help the animals adapt to habitat change.
Researcher Shannon White (left) with assistants implants a transmitter into a wild brook trout, which will allow her to track the fish's movement and monitor its behavior.

Researcher Shannon White (left) with assistants implants a transmitter into a wild brook trout, which will allow her to track the fish's movement and monitor its behavior.

Certain traits and behaviors may help brook trout populations adapt to habitat pressures, including warming climate conditions and resource competition, according to Shannon White, a Ph.D. student in Penn State's ecology program.

White explains that protecting brook trout is imperative because the animals are ecologically and economically important. "They're the only native stream-dwelling trout in the eastern United States and they net billions of dollars in recreational fishing and tourism revenue," she says. "They also play an essential role as a consumer of specific stream invertebrates, and as a food source for birds and other predators."

To investigate how behavior affects brook trout responses to habitat changes, White has employed several laboratory experiments in constructed aquatic environments. In one, she introduced the fish to a maze environment with a food source situated near visual cues such as a plant or rock; later, the maze was rearranged to see if the animals could relocate their food near the same cues. White also recorded the behaviors of the fish before they were introduced to the maze. Fish can generally be categorized as either "bold" or "shy," and they readily demonstrate their behavior when placed in a small personal tank. Shy fish remain still or cower in a corner, while bold fish actively seek an escape by swimming in circles or jumping.

White found that shy fish learned to relocate their food source based on the position of environmental cues, while bold fish traveled the maze without locating food.

"Bold fish aren't as good at forming small spatial maps, but they move more and go looking for new locations when their habitat changes, while shy fish stay close to home and try to solve problems they encounter," explains White. "It's good to have a mix of these behaviors. Bold fish can colonize new areas if a population is impacted by a habitat change; shy fish will stay put in their original area and maintain a trout presence. If you wipe out either, you have problems."

In the wild, White has assessed the behavior of 300 wild brook trout. She has also collected blood and tissue samples for genetic testing and implanted radio-telemetry trackers in 150 trout to follow their movements. Twice a week, she records the tagged individuals' newest locations and monitors environmental conditions such as the stream temperature in locations they are occupying.

"So far, behavior in this natural population has really varied," she says. "Some localized populations show boldness in 80 to 90 percent of individuals; others have only 10 percent. So our working theory is that behavior is variable, and there's not a set proportion of bold or shy fish that's standard in all populations."

Now at the mid-point of her research, White is beginning to see potential for her studies to add tools to brook trout conservation plans.

"In a lot of management strategies, we might think in terms of conserving brook trout as a species, or Pennsylvania's brook trout, or a watershed's brook trout," says White. "The idea of conserving specific behaviors isn't always something we consider, but it's something we might insert into a management plan if we know the important factors to conserve. It's a management tool on a different scale."

--Amanda Yeager