This weekend begins a new trout season and will bring many anglers out on the water. There are two things to keep in mind when fishing in the early season: trout metabolism and food availability. Actually, these are two things to keep in mind year round, and for all types of fishing. But what it means to keep these in mind varies from species to species and season to season.
As has been well noted and is easily noticed, water levels in local rivers and streams are already quite low, and the water is exceptionally clear for this time of year. Early this week I was out casting on Otter Creek, one of the few rivers in Vermont open year round for catch-and-release fishing. The water levels were what I normally expected in late August — and even then only if it is a dry summer.
There was also very little silt or discoloration in the water. I could see the bottom clearly in thigh deep current. Low clear water means fish can see food, which is good. It also means they are easily spooked. Which is bad. And water this low now bodes very poorly for August. Normally when I approach the opening of fishing season, I’m not hoping for more snow or for a chilling rain, but when I awoke on Monday to the patter of rain on my roof and a thermometer reading of 40 degrees, and read that we are in for a few days of this weather, I did not complain.
Despite our spate of 80-degree temperatures a few weeks ago, the water is still not particularly warm. On Tuesday, I checked the temperature of Lewis Creek where it passes through the southern edge of Hinesburg. I got a reading of 42.8 degrees. Though warmer than usual at this time of year, that’s still chilly for trout. And that was just past noon, the warmest part of the day, and well downstream from its colder sources up in Starksboro.
Now ideal temperatures for trout metabolism vary from species to species, but in all trout that can be found in Vermont it is considerably warmer than the water temperatures are right now. The Salmonidae family (which contains the fish we know as trout and salmon) is divided into three major genii that can be found in North America. The genus Oncorhynchus includes rainbow trout, cutthroat trout, and numerous varieties of Pacific salmon. While cutthroat prefer colder higher elevation streams, I have read that rainbow trout can tolerate water all the way up to 80 degrees if it is well aerated. In terms of feeding, somewhere around 60 degrees plus or minus 5 is ideal. The genus Salmo includes brown trout and Atlantic salmon. Although I don’t think browns can tolerate water in the same upper extreme as rainbows, they do have a similar temperature range in terms of ideal feeding metabolism.
Members of the Salvelinus genus are more commonly known as char, and prefer the coldest water of all the so-called trout. Most members of the char genus, which includes brook trout and lake trout, are found in the colder waters further north or at much higher elevations than Vermont. Even brook trout — whose Latin species name fontinalis refers to their preference for dwelling in cold springs or “fountains” — tend not to reach peak activity until temperatures get up in the range from about 48 to 55 degrees. Of all the trout in Vermont, only lake trout thrive in temperatures in the low 40s, and will go deep when the surface temperature of a lake drops below about 44. But while they can be caught in rivers in the west where they sometimes come up out of lakes to chase food, I’ve never heard of a lake trout taken out of a Vermont stream.
What this all means for early season fishing is that, while trout do have to eat year round, they are less likely to be moving about feeding actively on a cold April day. Bouncing a nymph slowly along the bottom of a stream is much more likely to get results than pulling a fish imitation such as a streamer or a large lure quickly through the current — even if the later approach might be very successful for large trout in another month. Also most species of aquatic insects that are active at this time of year tend to be smaller: midges and little black stoneflies and the smallest varieties of mayflies. As much as I love to drift a big golden stonefly through a favorite hole to attract the attention of a big fish, a much smaller fly is more likely to look realistic in April. Most of my early season and cold-water success fly fishing has been on my smallest flies: nymphs of size No. 16, No. 18, and No. 20. Rarely anything bigger than No. 14.
Having given all those warnings, I will say that there is success to be had. While my comments above about metabolism and water temperatures are reasonable general guidelines, in fact the change of water temperature can have as much impact as the absolute temperature. For example, trout are more likely to be feeding in water that has just gone up from 40 to 44 degrees than in water that has just dropped from 48 down to 44. Part of this may have to do with the amount of oxygen in the water. Water that has just gone from 55 to 60 will have more oxygen than water that has just dropped from 65 to 60. But more has to do with the sudden rush of aquatic insect activity that is often triggered even by small rises in temperature that might happen on a warm and sunny spring day.
Four weeks ago I was fishing over on a Lake Champlain tributary in New York. There was still snow on the ground, but it was a beautiful sunny day. Though the water temperature was only in the 30s, it went up a couple degrees in the later morning. There was a great hatch of little black stoneflies. The snow was covered with them. And over a 40-minute period after lunch I hooked several nice rainbow and brown trout on little imitation stoneflies.
Otter Creek is fishing well right now. While fishing a couple miles downstream of downtown Middlebury on Monday, I saw one nice fish hit the surface. Unfortunately, I was not expecting any surface action and was not fishing a dry fly at the moment. The fish was hitting something other than my fly. I don’t think I will be going to dry flies any time soon. But I do expect the first week or two of this new season to be as good as or better than any early season I’ve had in recent memory.