For what it's worth, I'm a member of the Keuka Lake Assocation and the Seneca Lake Pure Waters Assocation along with a couple of other things. Not that any of that matters much to you but I have been at some of the meetings over the past year where both Keuka College and the DEC gave presentations.
That being said, I'll throw in my 2 cents coupled up with some personal experience over past decade or so. Forgive me for the long response but I suppose the more information shared is better than less. Tried to keep it relatively organized.
First, nice video on pg. 3 of this thread where the scientist from Hobart College speaks. Similarly, on pg. 5, shaneo19 has some nice posts along with jerktroller who also mentions Keuka College & the DEC.
Anybody else notice an issue with the pike & pickerel?
Those of you who have fished the lake over the past 10-15 years probably noted that the pike population really exploded 10-12 years ago. Then, almost in one year, it plummeted. In the late winter prior to their decline, almost every pike I caught had red splotches on them. Not holes from lamprey. We saw some of that too. What I'm referring to are areas of their skin where the color had all washed out leaving only what looked like the fish equivalent to a brush burn. If you've ever seen photos of fish with VHS, it appears eerily similar.
Some historical considerations:
Sk8man, on pg. 5, mentioned how the waters on Seneca had become more turbid as we moved from the 50s & 60s into more recent decades.
Weed growth declines as water clarity decreases. Less light penetration = less photosynthesis = less plant growth.
Pike fishing declined as we moved from the 70s into the 80s. Why is this?
Ahh... pike eggs have an adhesive. They stick to the weeds. No weeds means the eggs go into the mud and considerably fewer survive.
Zebra mussels arrive and the waters clear. Light penetration increased significantly. Lo and behold, there is an explosion of weed growth. With the weeds so, too, come an increase of warm water fishes. The weedy environment is more hospitable to them. Weeds provide hiding places for juvenile fish.
However, with the zebra mussels also came less productive water. They are filter feeders. Notice how your smelt are gone? Yeah, those zebra mussels outcompeted them. Also consider that the lake, just like a piece of land, can only produce so much. You can't plant 10 acres worth of corn on one acre of land. In other words, however ever many tons of invasive mussel species there are in the lake would probably be about how many more tons of smelt and alewife, etc. existed prior to their introduction.
Don't believe this enzyme and the associated disruption of the vitamin B process in salmonoids matters? Here's a scientific paper that discusses the topic in great detail:
Of course, you can just skip most of it and scroll down to the "Conclusions" section at the end
While there has been an explosion of agriculture, which can include vineyards, along the lake(s) over the past 20-30 years, I tend to agree with some of the other posters here that it would not seem to align with the recent, abrupt decline. Of course, there is the possibility that the majority of farms, etc. switched to some new product but there is no evidence of such.
Similarly, the presentations which I saw earlier this year discussed that the the water quality in the lakes was generally very good. However, they also stated that the lakes would not be as historically productive due to the impact these invasive species have had. The ecosystem has changed.
Now, back to that pike problem
The DEC did confirm VHS in the canal as well as Conesus Lake but not in Seneca Lake proper. It's a pity none of us got any of those sick pike over to the DEC / Cornell. Let's, for a moment, consider that VHS or whatever it was, caused the abrupt decline of esocids in the lake. Let's also consider the explosion of alewife that folks on here have mentioned.
Did you know that alewife predate heavily on perch fry? I didn't... until recently.
So now you'd have a lake with few esocids (i.e. few predators keeping those hordes of alewife out of the shallows) but also loaded with minnow-based forage that predate heavily on panfish fry. Sound like this could be our lake?
From time-to-time over the past 8-10 years, there have been days where maybe I've caught 5-7 pike & pickerel in combination. As I'm generally a catch-n-release angler, I couldn't tell you what was in their stomachs but what I can tell you is that they were absolutely gorged. These fish tended to be visibly fatter than those that I had caught, say, 10+ years ago. Not that those that I had caught in the past were not well-fed fish. The pike & pickerel in Seneca have, generally, always been fast growing, thick fish. The few that I encounter in recent years are just stuffed.
It is ironic that so many fishermen complained about the pike and pickerel not understanding that, similar to lions on the Serengeti, they help to weed out the sick, weak and injured. Predators usually improve the genetic quality of this fish population.
Predators, Perch, etc.:
In my opinion, this points to an over-abundance of bait and a scarcity of predators. Some have also mentioned that, in the past, when bait increased, the bite decreased. This would make sense as the fish would be less active / hungry. The DEC has mentioned this too.
As for Keuka, the DEC said there was a recent decline in the alewife population. Not surprisingly, the perch seem to be doing well in Keuka. Both Keuka and Cayuga (especially the north end), are loaded with pickerel but they tend to be much thinner than those I've encountered in Seneca.
During the presentation at Keuka College, the DEC expressed concern over the rainbow population. They believe that the young rainbow trout entering the lakes from the streams as juveniles are being predated upon more heavily than in the past.
Here's a .pdf of a slideshow that details a variety of nutrient-related topics on Seneca Lake:
Similar to the charts in the above document, this paper also mentions that the salinity has actually decreased:
While salinity has apparently decreased over the decades since their peak, some have expressed concern over the lack of testing:
Keep sharing information:
In any event, I hope that the above information is helpful to our discussion both on here and externally.
Meanwhile, I guess we can continue to hope for tighter lines in the future