Personality and movement in wild populations
The field portion of White's study is taking place in three stream tributaries that run into Loyalsock Creek, located in northern Pennsylvania's Lycoming and Sullivan Counties. Using electrofishing to catch and release fish, White has assessed the personality of 300 wild brook trout individuals. She has also collected blood and tissue samples and implanted radio telemetry trackers in 150 trout to follow their movements. A few trends are appearing in her initial results.
"So far, personality in this natural population has really varied," said White. "Some localized populations show boldness in 80 to 90 percent of individuals; others have only 10 percent. Our working theory is that personality is variable, and there's not a standard proportion of bold or shy fish in all populations. Personality expression also has genetic and environmental drivers. For example, in areas where brown trout limit brook trout from exploring habitats, it could be driving shy behavior. Brown trout also grow faster and could be eating bold young brook trout that are actively moving and easier to predate, which means fewer bold brook trout will survive and reproduce."
White is looking forward to analyzing trends in the movement behaviors recorded for the tagged fish.
"Movement is one of the most critical survival behaviors because the species needs individual fish that can find specific habitats," said White. "And we need to try to conserve genetic groups that know how to move to the right temperature habitats like cold groundwater upwellings in streams, or areas where they can avoid brown trout competition. When we look through the data, I think we'll see these fish are behaving in ways we haven't thought about before, such as moving between stream tributaries to find optimal habitat."
Through genetic analysis of the tissue and blood samples she has collected, White also hopes to learn about the role genetics may play in brook trout adaptation. Pairing genetics and field observations may uncover individuals who joined a population from other locations, and contributed outside genes that are expressed in personality, movement behaviors and tolerance to changes like warming conditions.
One of the key brook trout questions centers around which genes generate the heat-shock proteins that help fish preserve healthy cells during warmer conditions — and what environmental influencers prompt the trout to turn those genes on or off. So far, research has suggested brook trout express the genes under not only thermal increases, but other environmental stressors such as low water levels; the genes are also being expressed at an early age, and when fish are still occupying temperatures several degrees below the upper-end of their thermal tolerance.
"It could mean they could adapt to warming water temperatures better than expected," said White. "If they are producing the proteins readily, they may develop some resistance and survive longer, at least if temperatures are warming at a slow pace."