Nature Notes: As Waters Warm

It’s the fish and fishing season. Long Island has a lot of different kinds of fishes and a lot of different kinds of fishermen and fisherwomen. If we count the tropicals that are more and more common in the south bays with each passing year, we have more than 200 different species of fish to pick from.
    Where did they come from and how did they get here?
    Let’s start with the marine fish, the ones that support the greatest number of fishers, both recreational and commercial. Ten thousand years ago when Long Island was cold and barren and still contained blocks of ice left from the retreating glacier, the seas were salty and barely above the freezing mark and the fish fauna was very limited in variety. The warmer water marine fish that are so plentiful today had retreated to southern waters thousands of years earlier as the ice sheet advanced over the upper half of North America and Eurasia and the seas became frigid. A handful of fishes, mostly belonging to the cod and salmon families, plied the offshore waters, there were no freshwater fishes, per se, and no fisher people to catch what few there were.
    As the Atlantic Ocean gradually warmed, the marine fishes that had retreated moved up from the tropics and subtropics into Long Island and New England waters. The northward flowing Gulf Stream abetted this process, carrying several species passively into northwestern and northeastern Atlantic waters. As it melted, the glacial ice filled up the pores in the glacial sediments, creating our groundwater deposits, while runoff from it produced streams that ran toward the Atlantic, creating the major river ways that are with us today such as the Connetquot, Carmans, and Forge Rivers.
    Rivers that ran toward Long Island Sound — the Nissequoge and Wading Rivers, for example — were created as the glacier retreated farther to the north. The largest Long Island river of all flowed easterly from between the two glacial moraines, the Ronkonkoma and Harbor Hill moraines, dumping into the Atlantic Ocean by way of the Peconics separating the Twin Forks.
    Diadromous fishes like the Atlantic salmon, brook trout, and alewives that can function in both salt and fresh waters ran up these rivers to spawn. After spawning the salmons and the alewives would run back down to the sea to feed and get ready for next year’s upstream run. American eels also entered fresh waters from the sea, not as reproductively mature adults, but as tiny elvers no thicker and half as long as strands of spaghetti. They would spend several years in fresh water while they grew to maturity, then descend back to the ocean, ultimately traveling all the way down to the Sargasso Sea, south of Bermuda, to spawn.
    A group of marine fishes such as the killifishes and silversides had already evolved to tolerate brackish waters. Indeed, one silverside, what the commercial fishermen call “white bait” did just as well in fresh water as in salt water, while one of the killies, banded killifish, became an almost exclusively fresh water species. The white perch in the striped bass family also evolved to do as well in fresh water as salt. Today it is found in some Long Island ponds in a completely landlocked state.
    It’s not hard to imagine how the marine fishes and the diadromous fishes settled in Long Island waters, but it is difficult to imagine how Long Island got its freshwater fish fauna, as Long Island has been separated from mainland North America for thousands of years.
    One hypothesis is that while the Island was still young and the land extended much farther offshore than it does now — in some spots as much as two miles — there was a kind of network of fresh water, a chain of puddles, as it were, stretching from New Jersey to Staten Island to Long Island. This chain of puddles allowed freshwater fish such as the brown bullhead, yellow perch, mud minnow, pumpkinseed sunfish, two species of pickerels, a darter, a dace, and a few other freshwater fishes to “hop” along this chain, a couple all the way to Fort Pond and Lake Montauk before it was permanently opened to Block Island Sound in the mid-1920s.
    This hypothesis would also explain in part how the blue-spotted salamander (which cannot tolerate salt water and breeds in fresh water) became established in Montauk, but nowhere else on Long Island. Such a nebulous waterway, not stopping at Montauk Point, but extending north along the Atlantic Coast all the way to the Canadian Maritimes, would also explain how the Prince Edward Island spotted salamander, genetically identical to the Montauk one, got that far north. Similarly, such a waterway would solve the riddle of how a freshwater turtle, the red-bellied turtle, became indigenous to southeastern New Jersey, the Delmarva Peninsula, and southeastern Massachusetts, including Cape Cod.
    Popular freshwater game fishes native to the Midwest and eastern America and now common in Long Island lakes and ponds that didn’t get here of their own volition, including largemouth bass, smallmouth bass, bluegill, rainbow trout, and carp, were introduced. The carp had the longest trip, it came all the way from Eurasia. Such introduction, popularly known as “stocking,” was carried out officially by fish and game entities and thus widely publicized, but also by individuals and fishing clubs, often secretly and far from the public eye.
    What of the future? It won’t be too many years before a tropical or two carried to our southern shores by eddies spinning off from the Gulf Stream begin breeding here. Rock jetties and groins will substitute as coral reefs to make them feel more at home. Then, too, if global warming is proven to be more than a hypothesis, southern marine fishes like the channel bass, several snappers, and others will extend their ranges to include Long Island waters. By chance establishment of tropical fishes, range extensions of southern marine fishes, and continued stocking and introduction, the Long Island fauna will increase. Fishing could become better than ever.