How Low Can They Go?

The United States Geological Survey records stream discharge (a measure of how much water is in a stream) at thousands of locations around the country. Here is a graph from the USGS discharge station in Loyalsockville showing current conditions in blue and what discharge has normally been over last 89 years in orange triangles. Stream discharge in Loyalsock is now <10% of historic average.

It takes years to coordinate, design, and execute a telemetry study.  When the wheels started spinning on this project I wasn’t even a graduate student at Penn State.  So, needless to say, there is no way to plan around unpredictable things like weather.  Coming off a relatively mild summer last year, all we could do was cross our fingers and hope that this summer would have the hot and dry conditions that are predicted to become more common in future years.
 


​In this game of field work Russian roulette, we won. Loyalsock Creek is barely trickling. The pools that were once too deep to wade through barely touch my knees. Between Tuesday and Thursday we saw stream temperature rise as much as 7°F. The ground is now so dry that stream flows are still decreasing even after heavy overnight rains.
 
I’m not sure how much lower the streams can go, but we’ll soon find out.  The forecast predicts even hotter and dryer weather for the next week. For the fish, this means several things.  First, rising stream temperatures are going to create stressful conditions that put fish at a high risk of mortality. So, if you’re reading this and considering going fishing, it may be better to hold off until stream temperatures decrease a bit (which may be awhile).  It’s a well-known fact that angling mortality dramatically increases at high temperatures because fish have a harder time recovering from hooking stress.
 
Second, fish are becoming sitting ducks for predators. With lower flows pools are shallower and many undercut banks and rock crevices that are good for hiding are no longer under water. Further, fish have a higher metabolism at higher temperatures. This means they are willing to put themselves in riskier situations and spend more time trying to forage at the risk of being nabbed by a bird or opossum. The last two weeks we’ve found many more tags in banks or dangling from trees.  Unfortunately (but also interestingly) many of the predated fish have histories as being some of the more mobile fish in the study. This observation fits in with a lot of ecological theories of animal behavior, but it’s too soon to tell if we have enough data to definitively say that the “mover” fish are more prone to predation.

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Tracking tags on land is harder than in water. In water they are confined to a stream, but on land they can be just about anywhere like this tag found dangling on a tree branch. Probably safe to say this was from a bird.

This past week we also surpassed 1000 detections, biopsy samples were delivered to the USGS Leetown Science Center in WV to start analysis, and plans are inching forward for August tagging.  I continued to be overwhelmed by the support and interest that everyone has shown for this project. This week we started a conversation with a local news station about doing a segment about my project.  So, stay tuned, literally, as The Troutlook may wind up on a television near you.

One last thing, on Tuesday I electrofished some trout to practice new suture techniques and accidentally caught a fish that was tagged in May. As you can see from the photos below, the fish was looking great with a completely healed incision and no infection from the antenna exit site.