The Water: Seasonal Variations: The Isothermal Winter
Seasonal Variations: The Isothermal (Winter Mixing) Period
After the thermocline breaks down, the high winter wind, long fetch, and uniformly cool water all help to keep Cayuga Lake well mixed from December through April and beyond. Cayuga, Seneca, and a few other Finger Lakes belong to a relatively small group of lakes that stratify in the summer, yet are too deep and windblown to freeze over in the winter. Because of this tendency Cayuga only has one 'turnover' period when the thermocline dissipates in late fall and the lake begins mixing. In contrast, ice-covered lakes are inversely stratified during the winter, nearly always maintain some form of a thermocline, and experience both fall and spring turnover periods.
Most fish retreat to the depths and become inactive during the winter, at least measured by weight! Cornell research shows that during the winter, most of the biomass in the lake (baitfish and trout primarily) is found in a layer from 40-60 meters (approx 130-210 feet) deep, with some fish shallower and some a little deeper. The alewives are generally between 150-250 feet and most of the lake trout are too. Some rainbows, browns, and salmon can be found near the surface during the winter but often these fish will also search the depths for food. Additionally, pike, pickerel and perch are all active in the winter and remain on the surface, so there are plenty of fishing opportunities, and searching out the warmest water you can find is the name of the game. AES Cayuga, formerly and affectionately "Milliken Station", has a warm water discharge that attracts many trout and pike each winter. Creek mouths are another place to look for fish, as well as shallow flats on a sunny day- especially with an onshore breeze. Even a slight variation in water temperature can attract and concentrate fish.
The water currents during this period are similar to the summer stratified currents, except the lake bottom acts as the thermocline boundary. The surface currents remain very similar to summer patterns, while the subsurface return currents often follow the lake floor instead of being concentrated around the thermocline. This is all just a fancy way to say, during the winter the wind still makes surface waves and currents but the subsurface currents could be anywhere! High winter winds ensure that plenty of mixing goes on during these months.
In recorded history there have been a handful of long frigid winters where Cayuga Lake has frozen over. Apparently it happened in 1856, 1875, 1885, 1912, 1936, 1962 and 1979 among other possible years. I'm not sure how many of these dates are substantiated, or if the lake had to be 100% frozen to qualify. Most of this information comes from "When Cayuga Freezes Over", from the Seneca County website's history section. It seems that at least several freezings were quite solid and the lake surface was frozen for a month or more! One family describes seeing the lake bottom in 150' of water, which I found interesting... that's pretty clear! That was in 1962. In the 1800's iceboats were reported, as well as skating from King Ferry to Kidder's Landing. Pretty cool, and it shows how things have changed.
In modern times Cayuga has been remarkably ice-free. Global warming or natural climate variability? We shall see, though I suspect the former. The pattern is a good match for climbing global temperatures, and if we don't act now on our greenhouse emissions, the Finger Lakes will become even warmer. The coldwater fish are moving deeper? Gee, what a surprise, the temperature is rising! This certainly isn't the whole picture: Newly introduced exotic species and changes in lake chemistry have a large effect on the lake as well, I'm not "blaming" everything on global warming but it is certainly something to keep in mind. It stands to reason if the climate is getting warmer the lakes will get warmer too. It is a fact that variations in the annual heat budget affect the ecology of the lake system. String together a few warm winters and you will see some year-round effects. Until recently the lakes have maintained a relatively balanced heat budget, but many lakes in the area (including Lake Ontario) have been setting temperature records in the past few years.
Overall the weather is cold and open water fishing is tough. Shore fishing at Milliken Station and Taughannock Falls State Park is often the best bet, as well as ice fishing for panfish and pike at the North and (less often) South ends of the lake. The smallest Finger Lakes ice over completely and can also provide good fishing.