Fishermen and women enjoy the natural beauty of the lakes and rivers they haunt, and the peacefulness and solitude of the sport. But what really gets us out there is catching fish. “The tug is the drug” is a T-shirt slogan that captures the reason we’re out there in all kinds of weather. Experienced Seneca Lake anglers have noted that many fish populations have dropped precipitously in recent years. This has been especially true of the warm water species (northern pike, bass, perch and other panfish), but we’ve also seen a reduction in catch rate of the cold water/trout species.

I live on the lake and fish it throughout the year for a number of species. I’m a fairly casual fisherman, though the thoughts contained here are influenced by reports from some more serious fishermen. First a quick summary of changes noted in fishing success will be provided, followed by a discussion of potential factors for the changes seen. Brad Hammers, New York State Department of Environmental Conservation (NYS DEC), Region 8, Fisheries Biologist, was kind enough to provide input on this article. Where Brad’s view differs from mine, or provides additional information, I’ve included his response in italics.

With no personal experience, I’ve heard many reports from winters’ past of fishing weed bed edges for large catches of big northern pike. When I moved full time to the lake in 2010, I would see and catch some northerns during winter perch fishing. In recent years, that fish has become rare in my area of the lake. (Brad- A 2014-15 fish community survey found a fair number of northern pike throughout the lake, and we have reports of good pike fishing in the last couple of years).

The bass fishing that was once excellent has degraded significantly, though there are some signs of a recent rebounding. (Brad- The ‘14-15 survey found a moderate number of smallmouth bass. Uncertain now, but had planned a bass survey for this spring, along with other fish surveys, to compare Seneca to other NY waters).

Fishing for large perch in large numbers was common in Seneca Lake, recognized as strong as its famous lake trout fishing. The last few years have seen a dramatic decline of perch anglers, who have now largely moved to other lakes to pursue this quarry. Experienced perch anglers are still getting some fish, but it’s a much tougher game to find a school and catch a few fish these days. Very disturbing to me is an apparent lack of small fish . (Brad- The ’14-15 survey found large numbers of perch. Hearing from anglers that perch are there but are more finicky.)

Lake trout fishermen report reduced catches and smaller fish, whether pulling copper, running down riggers, or jigging. The trout derby has seen fewer fish of smaller sizes in recent years. (Brad- Stocking levels were reduced due to increased natural recruitment in the mid 2000’s. Recent surveys indicate decreased natural recruitment. Less stocking, lower recruitment, and increased sea lamprey population likely causes of lower adult lake trout numbers. DEC is now increasing stocking levels.)

Smelt fishing (net dipping) was once a spring-time ritual across the Finger Lakes. Now that fish seems to be gone from these water bodies. (Brad- Smelt likely at an undetectable level.)

There have been many changes to the lake ecosystem that are likely contributing to these observations of our fish populations and fishing success. Discussions with experienced fishermen and inputs from biologists have been distilled down to some observed changes with potential impact to the fishery. One overriding theme is the large impact of invasive species.

• The invasive zebra and quagga mussels have created a huge change to the lake’s ecosystem. They represent an immense level of filter feeding and no doubt a major shift to the food chain. There have been changes in recent years from a predominance of zebra to quagga mussels, and we see them completely covering the lake bottom to extreme depths.
• Alewife (saw belly) populations appear to be very large in Seneca Lake since I’ve been here.  It is common to see huge schools on your “fish finder” sonar and see the vibrations in your down rigger lines as they pass through the mass. They are not native to our waters, and they are the major prey fish in the food chain for the larger sport fish species. Predatory species with a primary diet of alewives can suffer reproductive impairments due to a deficiency of thiamine. Alewives also feed on perch and lake trout fry, and it’s reasonable to assume some relationship between their population levels and that of these other species.
• Due to timing & high flow conditions, Seneca Lake tributaries have not been systemically treated for lamprey eels. In years when treatment does not occur, we see heavy lamprey predation on trout species. (Brad- This is a major player, especially on the cold-water fishery. 2018 treatment was very successful, and another treatment is planned for 2021.)
• Disease in our fisheries (Viral hemorrhagic septicemia, also known as VHS, whirling disease, other) may be a factor. (Brad- Closest VHS detection has been in the Seneca Canal near Waterloo.)
• The Rudd is an invasive fish that seems to be gaining numbers in Seneca Lake. Typically pan fish in size, schools of these silvery fish with red-orange lower fin areas can be seen and caught in shallow areas of the lake. Their impact is not well known, but they certainly create a competition for native and more desirable species. (Brad- Impacts unknown. Resemble a golden shiner and may provide forage for bass and pike.)
• The Round Goby has not yet been officially found in Seneca Lake. It is well established in Cayuga Lake, will be here in numbers at some point, and will further change the lakes ecosystem.  They are likely here already, but not in large numbers. Dr. Susan Cushman, at Hobart William Smith Colleges and Finger Lakes Institute is very interested in any reports of Round Gobies from Seneca Lake.
• Another potential factor in our fishery is the aquatic plant structure in the lake that provides sanctuary and nutrition for the food chain. Seneca Lake has an invasive species, Eurasian Watermilfoil, as the primary plant in our near shore areas. Though this plant looks similar to native milfoils, there is some evidence that chemical differences may affect the prey fish food chain.
• The NYS DEC Region 8 Fisheries biologist held a public review of the Seneca Lake fishery data in the fall of 2018 at Hobart and William Smith Colleges.
• • The DEC has numerous data sources for the trout and salmon species. Their data recognizes a reduced catch rate in these species as compared to previous years, but indicate they are near target levels. I have caught fewer in recent years, and I observe much fewer on the fish finder while trolling. I believe numbers are down substantially, but you can still catch trout if you put the time in. 
  • The DEC also recognizes the importance of lamprey eels and the recent issues with treatment in tributary streams. They are working to remedy these situations.
  • The DEC has minimal data on warm water species and communicated an intent to collect more information on these species.
  • DEC biologists are interested in getting more data and encourage Seneca Lake fishermen to participate in the Angler Diary Program.

It’s curious to me how similar and yet different this lake is from our nearest neighbors, Keuka and Cayuga Lakes. While they suffer from most of the same invasive species, the response in their fisheries seems quite different.

Many thanks to Todd Cook for initiating the thread of emails that prompted this article. The view that invasive species are a major factor in the changes we see in the Seneca Lake fishery seems to be well founded. The lake will change and adapt to these and other impacts, while anglers will continue to search out their quarry. To help assess the lake fishery and biology as it changes, and to support actions to improve it, Seneca Pure Waters intends to pursue a more active partnership with the fisheries area of NYS DEC Region 8.