When I’m doing monotonous field work I often purposefully get a song stuck in my head to help pass the time. This week Johnny Cash’s “Ring of Fire” was a perfect fit for the conditions in Loyalsock. Streams continue to heat up and dry out, and the weather forecast shows no end in sight. Fish movement has largely stalled and tags are now found almost exclusively in pools where there is some refuge from predation and somewhat lower water temperatures. Last week I wrote about how fortunate we were for such severe conditions, but I’ve since changed my tune and have had to completely overhaul the upcoming sampling schedule to avoiding stressing during tagging. But, if there’s one thing I know for sure, it’s that field work never continues as planned.
Now that we’ve hit a bit of a lull in the telemetry updates I can introduce another aspect of my project. From movement to genetics, we spend a lot of time collecting data on individual fish. Why? Well, we are interested in what causes individuals to behave differently and while it could be genetic differences it could also be due to differences in personality.
Yes, I just said that fish have personalities. And, much like humans, there is a bit of a ‘nature vs. nurture’ debate about what causes personality to develop. We know that both genes and environment are involved, but we’re curious as to whether certain genes tend to produce certain personalities. More importantly, we want to know if certain personalities tend to move more than others.
In humans, the five major personality traits, also known as the “Big Five” by psychologists, are openness, conscientiousness, extraversion, agreeableness, and neuroticism. While we can’t exactly measure a fish’s neuroticism, there are reliable test for fish that measure such things as aggression, exploratory tendency, and sociability. The most tested personality trait in fish is boldness, and it’s the trait we are attempting to relate to fish movement and genetics.
In addition to being comparable among many other studies, boldness is also relatively easy to measure. You simply place a fish in a tank, allow it a few minutes to calm down, and then record the amount of time the fish spends moving around and in the center. The idea is that when a fish is scared it will try to seek shelter by the sides of the tank. The less a fish is scared in this new environment the more it spends moving around and the bolder it is.
Last year I assessed boldness for nearly 400 fish across 16 sites in Loyalsock. This is one of the first field studies of personality, and by far the largest sample size (the next largest is probably well under 100 individuals). This year we will assess personality for tagged fish to look at how our personality assessments relate to genetic and telemetry data. Ultimately we’d like to find the driver for personality, and provide some information about how and why personality should be considered in conservation plans. For example, stocking only fish that are bold and move really far may not be advantageous when trying to re-establish a population or when surrounding habitat is not suitable for trout.
There’s also other reasons to consider personality in conservation (for example, some personalities are smarter than others), but you’ll have to stay hooked for that.
Behavior was filmed with an overhead camera and I'm in the process of quantifying boldness. I use special software to track the fish around the tank so I can determine how much time it spends moving around the tank (which is indicative of boldness) vs. on the sitting on the side (a sign of shyness).