The run

There is no such thing, I have been told by men who were in the business of making them, as a good or even adequate fishway. There is always an imbalance between the purposes they serve and the results. All the same, fishways are the best we can do to remedy a situation that blocked great populations of fish from entry to their natural routes. They are built to try and bring back what man has taken away; though it should be said that they are as much in man’s interest as the alewife’s. Commerce is the main benefactor of their success.

Fishways help open up free passage to the fish, and so increase their numbers. In a good fishway alewives can be counted or sampled. They can be taken out and transferred to other areas that are to be stocked with them. In other words, the removal of obstacles and the construction of a fish ladder means, in most cases, that a run can either be introduced or improved, and, above all, kept under control.

The trouble is that they cannot be built so as to result in free-and-easy passage for the fish at all times. In fact, if they are not properly placed, they can even be a hindrance. A fishway requires engineering and research in its preparation. They vary greatly, of course, according to local conditions. A fish ladder’s length depends on the distance of the slope down which a flow is directed, or the kind of banks, rocks, or stream formation through which it is built. I imagine there are no ideal specifications. For alewives, fishway construction depends in general on the size and habits of the fish and the nature of the waters in which they travel. The great fish ladders built for salmon at the Bonneville Dam, on the Columbia River, have pools in them that are forty feet wide, sixteen feet long, and six feet deep, each being a foot above the other. One foot is no problem to the salmon, which have been known to leap as high as ten.

At Stony Brook the pools on the down, or north, side of the road are ten in number and various in size, extending some distance downstream. The first six are smaller and deeper than the others, being so designed as to round a bend in the stream. Their depth, subtracting several inches of sand that keeps washing down from the road, is about two feet.

On the upper side, above the seining pool, leading from one of the pond outlets, is a straight ladder, some twenty feet long. Its pools are four and a half feet square and twenty-eight inches deep, each being about five inches above the other, thus graduating to fit the slope.

Whatever their design, fishways are all built so as to assure the alewives quick transit from one pool to another. In most cases they seem to work satisfactorily, but unless they are well managed they can effect full use of the stream by the migrant fish. Alewives have their own crowd pressure and motion, their way of moving on, and any reduction in their numbers at any one time or counterpressure, keeping them back, may result in a decline because less will get to the ponds to spawn.

Fishways are more rigid than a natural stream bed, though sometimes less hazardous. Water levels change; the flow varies both in angle and pressure; and managers of a good fishway must be constantly on the alert for new conditions. A marked increase or decrease in the volume of water, especially as it is reflected at the head of a fish ladder, which usually has a gate or wooden dam of some kind, may create a barrier instead of an aid. Unless the adjustment in the dam is just right the head of water coming down may be almost impossible for a fish to surmount.

Alewives are not like the muscular west coast salmon with their spectacular leaps, as if shot by a giant sling. An alewife does not leap over a pool and up a falls so much as swim through it rapidly, being a much smaller fish and in smaller streams. If a head of water coming over a dam or sluice is at the wrong pitch, the fish will not be able to climb it. In designing a fishway an engineer has to take into account the relationship between the water head and the angle of the flow below it, which has to be translated into how far an alewife can swim at what speed.

A fish is supported by water—an advantage over cumbersome human beings in their own surrounding medium, the air—its specific gravity being close to that of its own body. The fish is so made as to swim through the water with as little resistance as possible. It also gets energy from the water, orienting itself by the current, or the various changes of pressure in the flow, the way a bird uses currents in the air. In so far as a bird is streamlined too, and finds in air pressure and weight the means to fly up and forward, their actions have something in common. A bird, like an alewife, may lose its momentum if the angle of climb gets too steep. Swimming and flying take place in fluid surroundings.

The difficulty in making an artificial aid like a fishway comes from the problem, in part, of understanding a fish’s behavior; of meeting its needs; arranging its passage; trying, if not to control nature, at least to be a substitute for it. The positive results are plain to see, but there is something almost as elusive about it as trying to explain a fish in human language.

At one point along the Herring River in Harwich is a concrete fish ladder, twenty-five feet long and six feet wide. The pond above was high, after this same rainy spring, and the waters were roaring and frothing down. The alewives migrating upstream were being held back. Only a few I noticed were getting through. The flow had tremendous, deep force, so that the resting pools were not serving their function, and most of the fish that did manage by extraordinary effort to reach the head of water at the top were not able to pass it.

The racing torrent dropped to a wide, shallow basin which ended in the river winding on within its banks. A continuous long line of fish kept swimming through to the bottom of the ladder, where they would vainly skip and twist and strain through the water’s force. Then they swung back in a semicircular arc across the basin and re-formed at its edge. There was a wide shiver on the water. They wheeled as in a dance, or like the planets in pursuit of light, where they ran up again into the flood. It happened time after time, in this futile but concurrent motion, a beauty to watch—its tension, effort, and relief were exactly co-ordinated with the water. These fish were the water. But I saw in them the mechanics of breath ... contraction and expansion; and systole, diastole, balance and counterbalance, within the dynamics of all nature. They showed the push of life against a current, its running back and leaping forward, its fulfillment and defeat. It was the alewife circle again, as we have ours, in a motion of entirety; but almost impossible to translate.

“You never enjoy the world aright,” wrote Thomas Traherne, “till the sea itself floweth in your veins.” In the knowing and encompassing sense of his word enjoy, we will never know alewives until the motion, lift, light, weight, and changing beauty of the water is in some degree a part of us. In any case, we will never build the perfect fishway.