The run

The Herring Run area, small center of commerce and history, had been my starting point, but I had hardly begun to follow the alewives on their whole migratory route between salt water and the ponds above. First of all I had some background of local hearsay to bring into question. Did the herrin’ really go all the way down to South America in the wintertime? Was it true that each fish returned to the stream it was born in? Did they come inland on their spawning journey and then die, like the west coast salmon? I overheard a man say, “Poor fish! All that work just to die!” But that was one interpretation I could dispose of early, having seen them go back to salt water the year before. Did they only come in from the Bay at night or on foggy evenings? To find out would take more watching and waiting than I had done so far.

You might deduce this much to start with: the alewives, only a few at first, started to come inland in the spring when the brackish waters from the Stony Brook outlet were warmer than the Bay into which they flowed, if only by a few degrees. They responded with sensitivity to the temperature. If the earliest fish were the oldest, it was possible that the later runs also corresponded to age groups, guessing by their size, and that the youngest came last of all. Evidently schools of alewives stay together during their ocean life according to the years when they were spawned. Yet why, between March and June, any given schools would come in when they did would be hard to tell.

There are places where you can watch the alewives approach, at the junction between tidal and inland waters. At Damariscotta, Maine, they swim up a wide tidal river until a fresh-water stream flows into it from a height above. I was told that the fish are seen massing and circling, sometimes for days, at this point, until by some communicated decision, or joint response—perhaps to pressure of numbers, combined with the right temperature conditions—they start going up. A cold snap may make them drop back to tidewater. In the same way, cold weather may discourage their coming in from Cape Cod Bay.

You can also see them schooling in the Cape Cod Canal at the entrance to the Bournedale run, but not at Stony Brook where the outlet flows into the Bay through low sand dunes, or sand flats at low tide. Whatever the local topography may be, the alewives are evidently attracted to the warmer currents and the lack of salinity in a stream where it flows into salt water.

In general the cause of their moving in together from the offshore depths is their sexual development. I have heard the speculation that this is affected by the increase in light at this stage of the season, but unfortunately know no more about it. In any case at the age of four, or sometimes three, they are ready to spawn, to follow out the new force that is in them, on an old track. Their timing, when to migrate, is a question of generation, a decision that has to be made once again in the earth’s timeless schedule. Perhaps there is a comparison to be made once more with the weather, in which the element of surprise is constant during the usual course of the season, the intangible variant still plaguing prediction. The turns to storm or sunshine have their own order in the years beyond the immediate one. Who knows when anything will happen? Suddenly the cicadas start to sing in the August trees. Why that day or hour? Because “conditions are just right”? Perhaps, if we could ever track down all the conditions. Natural acts may be repetitive, but no flight, or song, or new growth has ever existed before at exactly the same time, pitch, or ratio. They are part of the indefinite context of generation.

What about the alewives during their years in the sea? Very little seems to be known. According to Fishes of the Gulf of Maine by Bigelow and Schroeder: “The alewife is as gregarious as the herring, fish of a size congregating in schools of hundreds of individuals (we find record of 40,000 fish caught in one seine haul in Boston Harbor) and apparently a given school holds together during most of its sojourn in salt water. But they are sometimes caught mixed with menhaden, or with herring. Alewives, immature and adult, are often picked up in abundance in weirs here and there along the coast, and it is likely that the majority remains in the general vicinity of the fresh-water influences of the stream-mouths and estuaries from which they have emerged, to judge from the success of attempts to strengthen or restore the runs of various streams.... But it is certain that some of them wander far afield, for catches up to 3,000 to 4,000 pounds per haul were made by otter trawlers some 80 miles offshore, off Emerald Bank, Nova Scotia at 60 to 80 fathoms, in March 1936.”

They also say, with circumspection: “It seems likely from the various evidence that the alewives tend to keep near the surface for the first year or so in salt water, and while they are inshore when older. But practically nothing is known of the depths to which they may descend if (or when) they move offshore, there being no assurance that those taken by trawlers were not picked up, while the trawls were being lowered or hauled up again.”

The view that most of the alewives stay in coastal waters near the fresh waters where they were hatched seems to be generally accepted, though the proof is sometimes hard to find. They occur at various depths in the sea as well as considerable distances offshore. They are as likely to be found in deep as in shallow waters. I am told there are recorded views that landlocked alewives winter in the deep waters of Lake Ontario, and that shad, a close relative, have been found with near-bottom animals in their stomachs. I also have the information that during the summer of 1956 draggers in Passamaquoddy Bay were catching a large quantity of alewives and that “it looked as if they were near bottom.” Despite some having been picked up in weirs close to the shore at various times during the year, they have not commonly, if at all, been taken by draggers on the continental shelf except when approaching the shore during the spawning season. In other words their oceanic whereabouts have not been pinned down. All we can say, still presuming stocks are local along the coast, is that mature alewives move in from deeper waters offshore in the springtime, progressively later from south to north.

What might seem to be a curious exception to the rule is a run in St. John Harbor, New Brunswick, that occurs in the dead of winter. Alewives are taken there in late January and early February; but I find that this may not be so peculiar a phenomenon as it sounds. To begin with, St. John Harbor is joined with the Bay of Fundy, and when the fish move into it they are still at sea. The reasons for their move at that time is not clear, but as there appears to be winter seining of alewives farther down the coast along the shores of neighboring Charlotte County, it is at least not unbelievable. The alewives then start through the harbor and move up the St. John River to their spawning grounds in the usual migratory months of April and May. I am told by the St. Andrews Biological Station that: “The inflow of the St. John River, particularly in April and May, dilutes the harbor water, especially at the surface. Whether it attracts alewives to the harbor or carries them there by deep circulation is a question.” This last point brings up the problem, quite beyond my powers to understand, of how the alewives orient themselves, how they find or are attracted to the waters in which they spawn. We may know very little about their life at sea, but their ability to find a particular stream or river may be an even greater mystery, which is not lessened by the probability that they have been there before. Whether as first-year spawners or repeaters the alewives seem to come back to the streams from which they migrated during the first summer and fall of their lives—when they were not more than a few inches in length. Not consistently—a certain amount of shifting between schools and change of locale may go on. Many go astray like migrating birds, or men out of crowds perhaps, but in general they do tend to return to their home streams. As a proof of this, ponds that were empty of alewives have been stocked with them, and the spawn returned as adults in three or four years’ time. This is the “parent stream” theory. With salmon it has apparently been shown to be a fact; although it is not so much the stream they were born in to which they return as the stream in which they grew up. Salmon eggs have been taken out of one river, moved to another, and then the hatched fry were tagged. They migrated to the sea and returned to spawn in the second river where they had their growth.

So what is to account for the alewives being able to find a “parent stream” that might be only a few yards wide, out of all the great stretches of the Atlantic coastline? They left it when they were no more than one and two-fifths to four inches long, but somehow, growing up in the sea, they must always have been oriented to that home base. They may have stayed reasonably near by, but even so this ability is hard to fathom.

Disregarding the question of how they arrived at that point, how could they tell one stream from another? They enter innumerable rivers, streams, inlets, some of them in close proximity. One theory has it that they are able to find their home waters by their characteristic odor, their special composition, to which they were conditioned when young. Even so, how did they get there? How can fish way offshore in waters of a consistent temperature, without any landmarks, tell which direction will take them to their home street? It is quite likely that they would be able to detect the outlet waters where they merged with the sea, but a stream may not reach very far, perhaps a few hundred yards or more at low tide, before being totally absorbed. All the way along the coasts, rivers and streams pour in fresh water, mixed in the estuaries so that it is brackish when it reaches the sea. The sea water increases in salinity as it gets deeper over the continental shelf. An alewife may detect very slight differences in salinity comparatively far out, but we are still not much closer to realizing how it finds its way.

What it amounts to is that no particular factors seem to be able to explain this directional ability of theirs. Not the response to changing currents in the spring sea, not the perception by fish of varying pressures in salt water, or of differences in salinity, nor their possible ability to use the sun as a reference point in navigation ... none of these approaches have yet solved the great mystery. Do they have some special sense, some perceptiveness, about which we know nothing? Scientists have measured and probed their reactions for a long time, but so far have not found any evidence of a special sensory ability. Biologically, fish do have several unique characteristics. For example, they have an “air bladder” by means of which they are able to adjust themselves to changing densities in the water. They also possess a “lateral line” organ, consisting of a tube or canal under the skin filled with mucus and connected to the nervous system. This sense, closely associated with hearing, enables them to detect vibrations of a very low intensity in the water and to avoid obstacles, such as an approaching bank or another fish. Aside from that, fish can smell, they have sight, and they have a sense of touch and taste.

These known senses are what scientists count on in investigating the migratory behavior of fish. They test their responses to different stimuli. On that basis, one of the most recent directions to be explored centers around the environmental factors which the fish are subjected to, such as currents, temperatures, the physical and chemical nature of the waters through which they swim. These factors are supposed to guide them successively on their migrations and to be so consistent year after year that the responsive fish return to their streams of origin because they never got off the track. Different schools, or age groups, of alewives would go to separate streams, because they responded differently, as Gerald B. Collins puts it in his study of alewives at Bournedale, “to the existing patterns of environmental stimuli.” Homing, from the environmentalists’ point of view, is neither a matter of memory nor mystery.

I do not have enough knowledge behind me to discuss such a method or approach, but it does seem to have the advantage of comprehensiveness, of taking the whole journey in. It does not depend on any single factor to explain migratory behavior, and it provides a good long track of exploration, step by step.

Whether the migrant fish behave as mechanically as this suggests, or whether the factors involved are separately either as consistent as they are supposed to be, or amount in the aggregate to as much as they should, remains to be seen. We are still in the realm of theory, however rationally expressed, and do not know yet how the fish find their destination.

Can a fish judge its course by the sun, or by the circulation of the waters of which it is so much a part? Can we talk about a homing instinct, or orienting ability, in connection with it? What are we defining? I don’t think I beg the question by finding it pertinent that civilized human beings have to some extent lost their ability to find their way in the woods, or no longer rise and sleep with the sun, or that they are not aware of the changing tides. Some old directional knowledge may still be innate in us, though we seem to think we have no need of it. Our puzzle, or lack of definition, may lie with ourselves as much as the alewives. In any case, what we try to find out by fact or abstraction is already known to the fish.

They are still ahead of us. So much of their motion seems to be a part of the race as a whole, synonymous with its great water world, that it is almost as if they found their way like the wind and tides, elemental forces that we find it hard to evaluate. We try to pin down that which expands immeasurably beyond us.