The Death Nell Tolls For Tropical Fish In Long Island

Lion Fish In Long Island Estuary

Coming to the edge of a straight-as-an-arrow mosquito ditch, I scan the verdant salt marsh that surrounds me. The air is filled with a bracing aroma of salt-filled air; it holds a hint of what to me smells like iodine. A willet, flashing its showy black-and-white wing calls out its piercing "pill-will-willet," as it crosses a back channel that meanders through the island next to mine. Turning to take in the view behind me, I catch the flight of several terns passing over the main channel with typical tern buoyancy and lightness. They're searching with heads down for movement at the water's surface, sure evidence of the small fish that comprise their diet. On the horizon, through the mid-August haze, I see the ornate brick tower that heralds visitors to world famous Jones Beach State Park.

The tide is rising quickly and flooding the ditch. The muddy banks, habitat to a healthy community of ribbed mussels -- the poor cousin to the blue mussel of mussels marinara fame -- are now submerged. A school of darting striped killifish catches my attention; perhaps made nervous by my presence, they scamper in all directions seeking refuge amidst the Spartina cordgrass jungle that lines the channel. Suddenly, drifting in the channel's rapid current is an unfamiliar looking fish: about five inches long, with a distinctive pouty look and a long tail. It's splotchy with a conspicuous dark line that runs diagonally from the belly through the pectoral to the dorsal fin. What is most attention-catching about the fish, though, is its position in the water. Instead of swimming in a horizontal position, it is drifting in the rising current with its body dipped face down at a 45 degree angle. I match its outline, pattern and swimming behavior in a field guide to fishes of the Atlantic Coast -- it is an orange filefish.


This fish is part of an annual event that is both fascinating and sad -- the arrival, each spring and summer, of several dozen species of beautiful tropical and subtropical fish into Long Island's estuaries. Here they mingle with the marine fish sought by anglers -- striped bass, blackfish, bluefish, weakfish, flounder, fluke and porgy. But unlike these other fish that either move out of Long Island's coastal waters with the onset of cold weather or are adapted to surviving the seasonal drop in water temperature, the tropical species don't leave and are not tolerant of significant declines in water temperature. For most tropical fish, the trip into Long Island waters carries no return ticket; by December they will have perished from either predation or the cold.

The list of finned visitors hailing from tropical locales is long: butterflyfish, angelfish, triggerfish, grouper, squirrelfish, surgeonfish and filefish. Notable species include the blue tang, an electric purple and blue specimen; the strange looking bluespotted cornetfish, possessing a mouth fully one third the length of its body; and the striped burrfish, a species related to blow fish, with a body that has the wonderful pattern of a child's discovery maze. And there are fish with colorful names: the lookdown, the sergeant major, the beaugregory.


The influx of tropical fish into Long Island is most common in the south shore bays -- Jamaica, South Oyster, Great South, Moriches and Shinnecock. The reason for this restriction has to do both with the position of Long Island along the Atlantic Coast and the force primarily responsible for bringing these species north -- the powerful Gulf Stream current.


The Gulf Stream is part of a circular group of clockwise currents known as the mid-Atlantic gyre. Ranging 20 to 40 miles in width, the Gulf Stream averages between two to four knots (giving rise to the apt description: "a river within a sea." It is a high salinity current, with concentrations averaging about 36 ppm (average seawater is slightly more than 32 ppm). It begins as a current flowing out of the Gulf of Mexico around the tip of Florida, where it is referred to as the Florida current.


Many tropical and subtropical species spawn in waters off the southeastern United States from Cape Hatteras south. While most eggs and young presumably hatch and develop within their normal range, some are captured in the planktonic and larval stages by the Gulf Stream and swept northward. As it glides north, the Gulf Stream stays fairly close to the Atlantic coastline, until it reaches Cape Hatteras. At this point, the current arcs to the east and runs parallel to Long Island, about 200-250 miles to the south. While the Gulf Stream is the mechanism by which tropical fish are carried northward, it doesn't account fully for how they make it into Long Island's south shore bays.


The next step in bringing tropical fish to Long Island's shore has to do with the formation of what oceanographers refer to as "warm-core rings," circular clockwise currents about 100 miles across and many hundreds of feet deep. The Gulf Stream undulates, at times looking like a river with sinuous curves and oxbows and, as with rivers that cut through land, the oxbows of the Gulf Stream occasionally pinch off. With land rivers this means a new channel and a stationary oxbow that becomes a backwater swamp, but when Gulf Stream oxbows pinch off, they don't remain stationary. When the oxbow looks like the letter "u," the rings spin off to the south of the Gulf Stream. However, when it looks like the letter "n," warm-core rings are formed. They spin to the north and west, carrying the warm water entrained within them closer to the south shore of Long Island. The warm-core rings bring the fish to within 75-100 miles of the shore.


By now, the fish have reached the edge of the continental shelf. Up to this point in their journey, most of them were in larval form incapable of swimming, having drifted north in the Gulf Stream current. But now, many of the juvenile fish go through a stage called flexion in which they grow a tail enabling them to swim, albeit rather weakly. "Once they go through flexion and form a tail, they are much more capable of swimming. Not only can they swim horizontally, but also vertically; this enables them to move into different layers. Since layers of water move in different directions, they may follow a layer that brings them toward shore," notes Robert Cowen, a professor of marine sciences at SUNY Stony Brook, who has studied the phenomenon for several years.


As the warm-core rings move into shallower water, they begin to break apart. At this point, the larval fish become entrained within the coastal current that runs east to west along Long Island's south shore. A combination of wind driven currents and tide surges are the final events that deposit the still tiny fish into these embayments.


Not all the tropical fish coming into Long Island's waters do so as drifting juveniles. Schools of adult gray triggerfish, for example, will often visit during the summer months only to move off once water temperatures drop. "We see schools of gray triggerfish in Shinnecock Bay in late summer, with each school having a dozen to 15 fish. I know people that tend them, and they look forward to feeding them at dockside throughout the bay," notes Howard Reisman, a professor of ichthyology at Southampton College. The motives of the fish feeders may not be altruistic, however. Triggerfish are tasty and people fish for them, catching the tamed fish quite easily.


Tropical fish seem not to reach Long Island Sound or the western reaches of Peconic Bay, at least not in any appreciable numbers. Reisman has found tropical fish, though, in Tobaccolot Pond situated on the eastern, ocean-facing side of Gardiner's Island, but not in the ponds on its sheltered western side. Gardiner's Island, where Captain Kidd buried treasure several hundred years ago, near the extreme eastern end of Peconic Bay. As might be expected, no species were observed in a pond situated on the sheltered western end of the Island. Tropical fish are common in New Jersey's coastal embayments. They also find their way up the Hudson River.


Late summer is the best time to observe tropical fish. Most species arrive several weeks to months before, but being so small (probably one to one and one-half centimeters long) are hardly noticeable. Most tropical species find refuge in eelgrass beds, the same habitat critical to the development of many other marine species including, most notably, the bay scallop. They grow quickly, feeding on the plethora of marine invertebrates and other food items available in these all important underwater communities. By the waning weeks of summer, they've reached thumbnail size and are clearly seen.


I was reminded how abundant tropical species can be in Long Island's south shore bays while visiting the marine laboratory owned by Southampton College. Earlier that mid-September day, students in Professor Reisman's ichthyology class had conducted a number of sweeps through the eel grass beds of Shinnecock Bay. They had caught several hundred specimens of snowy and red hind groupers, spotfin butterflyfish, bluespotted cornetfish, and crevalle jack; a single trunkfish and red goatfish; and a number of fish that go by the name of permit. Reisman estimates to have captured 50-55 tropical and subtropical species from Shinnecock Bay since his classes began seining in the embayment more than a decade ago.


Most, if not all, of the fish will perish, although individuals survive longer than one might guess. A New Jersey study of tagged butterflyfish determined that they survived into mid-December. The fish either succumb to the cold or become so moribund they become easy prey for the native predatory fish adapted to Long Island's icy marine waters. "It's a one-way trip for these fish," Cowen notes succinctly.

The Future of Tropical Fish

The future is brighter for the tropical fish caught by Southampton College students. A few are kept at the laboratory for public display and for research by marine science students and faculty. Surplus fish are made available to other aquariums along the East Coast, including the New York Aquarium at Coney Island. Tropical fish that spent the summer in the eelgrass beds of Long Island's south shore bays will, at these aquaria, swim in exhibits depicting their typical coral reef habitats -- the same environments that their brethren, not swept up by the Gulf Stream, inhabit in the wild ocean.

For additional Information go to http://aquatic-source.com/