Everything Gill Lice!

Hello everyone, it has been a very hot and busy week for me here in Wisconsin! One of my main research interests during this internship, which I haven’t really touched on this blog, is gill lice on brook trout. Specifically, I am interested in a species called Salmincola edwardsii which is a parasitic copepod that attaches to the gills, operculum, and fins. These parasites can harm the host fish by interfering with gas exchange and making the fish more susceptible to stressors such as warming water temperature and disease. Of importance is also that this specific species of gill lice does not infect brown trout which are an invasive species and are threatening native brook trout populations. In Wisconsin streams, these parasites are relatively common and have become a topic of growing concern. The combination of stress from invasive brown trout, warming stream temperatures, and infestation by S. edwardsii could become a lethal combination for the beloved brook trout. This week we went out to one of the most heavily infested streams in Wisconsin and inspected some of the fish. Below are some pictures of infected brook trout with many of them having 20 or more parasites attached to their gills. Being able to see infected fish first hand and observe the damage that these parasites can have when found in large numbers was really cool!

This is our setup when we inspect fish collected from the stream using electroshocking. The fish are first placed in a bucket with a small amount of anesthetic called AQUI-S. Then the fish are measured on one of the wooden measuring boards, weighed, and then inspected for gill lice.

The picture above shows the gills of a brook trout infected with S. edwardsii. The smaller circle contains just one individual parasite while you can see at least 5 parasites in the bigger circle.

This picture shows the healthy and uninfected gills of brown trout, a stark contrast to the heavily infected brook trout.