This past month has seen a variety of efforts here at the office, field season is still in full swing and we have been busy! We have been trapping fish in Tule Lake just across the border from California. We have had a little bit of success, but we were largely catching small fish and have not found suckers in the lake. We moved our traps to the deepest part of the lake, which was more successful. We managed to catch larger fish, mostly chub species. We also caught the largest sucker we have caught all season, most likely a short nosed sucker. Unfortunately we are having problems with our boat, so we may be unable to set traps for the rest of the season.
Short nose Sucker caught in Tule Lake
We have also been trapping at the Lower Klamath National Wildlife Refuge. We have caught three suckers so far in the largest pond, the only pond where we are supposed to have fish. We were able to get a pit tag ID on the last two suckers. They were placed in the pond last year and have doubled in size over the winter. This is really good data to have because it suggests that we can take salvage fish to be reared to a more hearty size in a relatively quick manner.
Sucker of unknown species caught at Lower Klamath National Wildlife National Refuge
This past week the Bureau of Reclamation (BOR) needed help conducting sampling at the Fish Evaluation Station (FES). FES is a way of estimating how many fish, with an emphasis on suckers, get entrained in irrigation canals throughout the season. In the past the BOR has sampled for 24 hours, they found that fish rates were higher at night, so they began sampling from 8pm to 2am for intervals in 30 minutes, pulling the trap net every half hour on the hour. Suckers are measured and weighed and evaluated for physical abnormalities. The number of other species caught is also estimated.
This year we wanted to figure out if 1) the fish we are catching are all unique individuals or if the same individuals are getting recycled 2) if we can keep suckers and rear them to a more hearty size and then rerelease them. To figure out if the same fish were getting captured in the trap net we VIE tagged sculpin and chub. These species were chosen because they are showing up in a manageable number; the sculpin was also chosen because its life history is similar to the suckers. We conducted the experiment through August, when we stopped because of low fish numbers. We are still analyzing the data from this experiment, but we think it will give us really valuable data that will help us better determine the number of fish that are being entrained in the irrigation canals each year.
We also held half the suckers from each pull to help determine if we can rear suckers caught in the FES trapping effort. We held suckers in tanks for the week and took the survivors to net pens in Upper Klamath Lake. We were unsure how well this experiment would work because the suckers coming through were believed to already be in bad health. While the data is still being analyzed from observation, it appears that as the sampling went on we were able to hold less suckers because less were coming through the traps. However, it looks like a greater percentage survived. It will be interesting to see if this holds to be true after the data is analyzed statistically. We conducted this experiment through August as well and stopped because of low sucker capture.
This past week I helped BOR conduct the sampling because they were short staffed. While we did not continue the recirculation study, we did try and hold suckers. However there was a low fish catch which included suckers. We caught just seven suckers all week and were only able to hold one. We are unsure why the fish capture is so low this year, though there are several theories including bad water quality and that it was a low spawning year.
Trap net at the Fish Evaluation Station
Sucker holding tanks at Fish Evaluation Station
My internship is wrapping up, as I have about a month left. That means that it is final report time! I am analyzing the data for the monitoring at the Lower Klamath National Wildlife Refuge. I am really excited to see what the data can tell me. I am especially excited to do some analysis with Geographic Information Systems. I have a lot of GPS points for predator evidence and I am interested to see if it there is a pattern to where predator activity is occurring. I am also getting to write a field note for the project, which will be a great chance to work on public outreach. The last month should be busy but rewarding.