Brook Trout, Salvelinus fontinalis
The water in this frothy brook is decidedly colder than it was a few weeks ago. As autumn approaches the weather will only get cooler and we can expect a corresponding drop in water temperatures as well. Cold water in these upper reaches of Taylor Brook will encourage brook trout to migrate upstream from deeper pools in down stream areas in search of breeding habitat for the upcoming spawning season. I am checking out some pools that are situated below shaded, steep drop offs, places where gravel collects; the precise habitat needed for brook trout spawning.
Today I am using a kick net. This information gathering device is really quite simple. It is about as low tech as one can get in gathering ecological data. The net has a long handle. At the end there is a broad, very fine meshed net. The dimensions of the net are about two feet wide by about a foot wide. The beige net (it was once bright white many years ago), so finely meshed that a grain of sand can’t pass through, is relatively shallow-about 6 inches in depth. The idea is to hold the net downstream from yourself, disturb all of the gravel in a square meter area by kicking at the gravel with your feet (hence the name kick net) in an effort to try to catch benthic invertebrates (essentially water loving bugs) in the net. These benthic invertebrates reveal data about both water quality and available forage, both critical elements when it comes to brook trout. We can estimate water quality by identifying the particular species that are caught in the net. Benthic invertebrates have a wide variety of preferred habitats and we are looking for those that indicate clean, well oxygenated water. The raw numbers of benthic invertebrates, larval dobsonflies, caddisflies, mayflies, diptera, craneflies, stoneflies, midges, and annelids will give us an indication of both food quality and amount. Brook trout will migrate into or near breeding areas as soon as the water cools down, optimally they are looking for water temperatures in the mid-fifties (Fahrenheit), where they will gorge for a while prior to the spawn. Brook trout in out area typically spawn in mid to late October. The spawn seems to be occurring later in recent years; perhaps a result of our ever changing climate.
On this particular day my kick net yields about one hundred specimens per sampling. This is about average for our area and it can vary from season to season and from day to day. The most common critters are mayflies, diptera, and stoneflies. There are lesser numbers of caddisflies, hellgramites, and annelids. I will have to wait to get back to my office to key out the exact species that I’ve sampled but based on past experience this is a healthy crop indeed and one that indicates very clean and well oxygenated water. Brook trout are a true water quality barometer. If they are present the water is clean, seldom turbid (except for after large storm events), cold, and full of oxygen. Their mere presence tells me I am a lucky man. Living near clean water in this world is an ever lessening opportunity.
There is nothing quite so precious as clean, clear, cool water. In New England we are very fortunate to have many streams with nearly perfect water quality. Hill towns and remote areas with steep slopes, ample water, and thriving cold water streams are ripe for one of the regions premier fish, the brook trout.
Brook trout (Salvalinus fontinalis) are the only native trout in our area. Actually they are not trout at all. They are truly a char, a close family cousin to the trout group. Locally they are often referred to as square tails or speckled trout. Some consider the brook trout to be the most beautiful of all fresh water fish. I would have a difficult time disagreeing with this opinion. The dark mottled back, dark green to bluish gray sides, a contrasting red to orange underbelly, and dorsal and anal fins that are edged with a bright white stripe are a combination of patterns and colors that is both striking and awe inspiring. Their awe striking beauty is somewhat of a mystery. The best theory that I’ve heard is that the most brilliant fish use their stunning appearance as part of the defense of their mating territory. Perhaps what humans call beautiful instills fear in other trout. Who knows?
This beautiful fish is elusive. If you are lucky you will catch a glimpse of one darting from an overhanging bank or a crevice under a rock while walking the shore line of a small brook or stream. You will only get to see one up close if you are an angler or someone who hangs out with an angler. In these parts a mature brook trout will top out at about 7 to 9 inches in length. A nine inch fish could be 6 years old, a very long life considering all those who prize their delectable flesh. Beyond humans, brook trout are foraged by otter, kingfisher, heron, mink, and even raccoons (if they can trap one in a shallow pool!). As a predator they likely know they will be predated; a sobering fact of our biological world.
I am most interested in the upcoming spawn. The female brook trout will locate good breeding grounds. Pools with a gravelly bed, high oxygen content, and very cold temperatures are perfect. Most of the chosen pools are well shaded, out of the way places that get little disturbance. The female prepares the bed by creating a nest or Redd as it is referred to by biologists. The female uses her tail to sweep the gravel creating a nesting area of 1 to 2 square feet in size. There she will deposit up to 400 eggs, later to be fertilized by a dominant male. After the eggs are fertilized the female uses her tail again to cover the eggs with gravel. The primary critical objective is for the eggs to get a steady supply of oxygen while they incubate. Two or three months later, depending upon the water temperature, the eggs will hatch. These hatchlings, called sac fry, will remain in the Redd until the yolk sac s fully absorbed. They will venture away from their birthing grounds when they are about 1.5 inches in length where most will fall prey to a variety of predators, stream conditions, or just plain bad luck.
It is interesting to note that the brook trout that live primarily in lakes or large ponds and use feeder streams for breeding habitat are significantly bigger but not genetically different from those brook trout that spend their whole lives in small streams. It is not unusual for a brook trout in a lake to reach 24 inches and 5 pounds. I’ve personally caught some in the 20 inch and 4 pound range in northern Maine.
So on this day when I have chosen to spend a couple of hours doing an informal aquatic census I feel privileged. I am lucky to be breathing clean air, standing in clean water, and thinking pure thoughts about one of our glorious creatures. And though I’m sure the brook trout has absolutely no appreciation of me I am in awe of them.
And as long as they are present I know that this brook is pristine. That is if you describe pristine as being clean, pure, and alive.. I can’t imagine wanting a brook to be any other way.
Written for the Heath Herald in September 2013.