Department of Environmental Conservation 2020 Seneca Lake Fish Surveys 

Dan Corbett, Vice President of Water Quality

Seneca Lake Pure Waters Association

Members of Seneca Lake Pure Waters Association recently met with representatives of the New York State Department of Environmental Conservation (DEC) to review the fish survey work done during the 2020 season. Brad Hammers, the Region 8 fisheries biologist, explained the work that was conducted and his initial impressions of the work. The formal data entry and quality checks are ongoing, and information should be included in the statewide data base by the end of January. More detailed analysis and results from these surveys should be available sometime in the spring; Brad has agreed to help us to disseminate that information.

A fairly extensive set of surveys was planned for 2020 to address concerns expressed by fishermen and lake users. The Covid pandemic and work practice uncertainties resulted in a late start to the survey season, but happily most of the work was completed. DEC plans to conduct these major fish surveys every 3-4 years on key lakes.

Preliminary Summary of Findings

Shallow water surveys targeting warm water species were done for the first time on Seneca Lake. There have been many concerns from anglers about a drop off of fishing success for many of the warm water species (perch, bass, pike, and other pan fish). The pandemic resulted in a delayed start to this work (late June). This is nighttime electro shocking from boats, near shore, and the primary species targeted were bass and yellow perch populations. You may have noticed the activity of lighted boats along the shore during late evening hours. Fifteen to 18 sites were sampled, from the north, south and central lake shore regions. Roughly 60-70% of the bass found were smallmouth versus largemouth and they were generally in good condition. Bass numbers were not as high as seen in Keuka Lake, but may be about average for New York lakes. Perch numbers were quite low, which may be due to the late seasonal start and warmer water temperatures. All species found are recorded during these surveys. While minimal sunfish were found, alewives and bullheads were plentiful.

 Smallmouth Bass pictured

Deep water netting surveys primarily targeting lake trout were done for two weeks in July. This type of sampling has been done since the 1970s. Thirty-two sites around the lake were sampled at a depth where 50°F temperature meets the lake bottom, and then deeper (at and below the thermocline). Good numbers of lake trout were found, and they were in good condition with minimal lamprey marks. Most were stocked fish, evidenced by a clipped fin, indicating only 20 - 25% natural reproduction. Lack of natural reproduction fits with the high numbers of alewives as a food source, and the early mortality syndrome caused by thiamine levels.

Forage netting (0-45 feet) was done for two weeks in September and showed a very high level of alewives – the highest in the cold-water western Finger Lakes. No round gobies were found in any of the surveys, and remain unconfirmed in Seneca lake.

Sampling (electro shocking) of Catharine Creek was done during the spring spawning run, as has been done in past years. Good numbers of fish were seen and were generally in good shape. However, fish were heavily marked by lamprey eels. Lamprey larvae surveys were done in Catharine Creek, the Watkins Glen canal, and the Keuka Outlet delta area near Dresden. No larvae were found at the Keuka Outlet delta, but were found up to Pine City in Catharine Creek, and in the Watkins Glen canal. Lampricide treatment is planned for 2021, which is typically done every 3 years.

Stocking of lake trout will likely be increased due to low levels of natural reproduction. Brown trout were heavily stocked in 2020 and will likely not be stocked in 2021. Atlantic salmon (pictured) will continue to be stocked at similar levels. Rainbow trout are stocked in Catharine Creek each year at a level of approximately 10,000.

Fisheries management plans are being developed for all the Finger Lakes. There will be an overall regional plan, and a plan for each lake, hopefully early in 2021. We’ll keep an eye open for that as it will contain good information on the current fishery status and future plans.