My last two columns dealt with lake stratification and its impacts on water temperature and oxygen levels. In this column, I would like to tie the whole stratification scenario into how it can benefit a knowledgeable angler.
In review, after the ice off when the surface temperature reaches 4C, the lake will turn over mixing the entire water column at that temperature. I will call this time the spring fishing season. Due to the nature of the turnover and mixing, often time oxygen will be in short supply until the lake begins to get oxygen input from the surface.
The north shore of a lake’s shallows warms up the quickest, inviting the fish to move there as it becomes comfortable for them to do so. With the lack of any significant insect emergences, the trout will feed on the bugs available in the weeds and reeds along the shoreline. These would be water beetles of different species, damsel and dragonfly nymphs in various stages of development, as well as leeches and scuds. As the water continues to warm and the lake begins to stratify, aquatic insects begin to emerge. First the chironomids, then the mayflies, followed by the damsel and dragonflies, and finally the caddis flies (sedges).
This now takes us into season two, early summer, when the upper layer of warm water has descended, and the fish begin to seek out comfort zones. From what I have read, it varies for different species. Rainbow Trout prefer temperatures ranging from 10 to 15.5C (51 to 60F) with an optimum temperature of 12.7C (55F), with Kokanee having similar preferences. Both Lake Trout and Brook Trout have a slightly different preference, ranging from 7.2 to 12.7C (45 to 55F). What this means to the angler is that as the surface water warms to greater depths, the fish will also go deeper seeking out their comfort zones. In the absence of a decent thermometer, an effective fish finder will locate the depths where the fish are at any given time.
Come fall, the third season, the surface water cools, and the thermocline becomes less stable, allowing the fish to begin to ascend upwards staying within their comfort zones, providing them with access once again to the littoral zone (where weeds occur in a lake) and the insects and other aquatic organisms that live there. Both the summer and fall seasons see a few minor insect emergences, mainly chironomids and caddis flies; however, the water boatman and backswimmer beetles can be found doing their mating flights in late September to mid-October.
These flights can get the trout’s attention with a lot of focus being on these beetles, foregoing their usual fare of nymphs, scuds, and leeches that usually make up most of their diet at this time. Just before the ice comes on and the water is cool, the fish can often be found feeding in the same shallow zones they were foraging in during the spring.
The fourth season provides ice fishing opportunities that present unique challenges, with different fish species occupying different depths. Rainbow and Brook Trout will most often be found in the shallower areas of a lake where the food is plentiful. Kokanee will be found stratified at various depths up to 18 meters, but most often in the 6-to-10-meter range. Lake trout on the other hand can be found much deeper in the water column, a lot of times just off the bottom.
While I have dealt with numerous generalities in this brief overview, the ardent angler will be aware of these seasonal changes and adjust their tactics accordingly.
