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Common Prey Fish

Note: This article first appeared in the Sept/Oct 1992 issue of The Conservationist magazine. Recently updated. Authors- Russell McCullough & Eileen C. Stegemann. Eleventh in a 14-part series describing the Freshwater Fishes of New York.

Common Prey Fish Of New York

At some point in each fish's life, it is food (or prey) for another fish species. Larger, stronger fish or predators seek out and eat smaller fish or prey. This is just a fact of nature. But certain fish species, such as those described below, are considered prey or forage fish for their entire lives.

The term prey fish is actually a loose term used by people to refer to certain non-game fish species that are the main food items for popular sportfish. As a rule, a fish is considered a prey fish if it remains small enough in size during its entire life cycle and it occurs in large enough numbers to adequately feed a predator fish population. In addition, these fish are generally not used by people other than for bait.

But while prey fish are mostly considered a significant food source for popular gamefish, it is important to remember that they are also an essential and integral part of a healthy fish community. Prey fish help maintain balance in the fish community. They play the role of predator by eating the larvae of other fish species, including young sportfish, as well as play the role of competitor by eating the same foods as other fishes. If something happens to the prey fish population, the entire fish community is affected.

In New York State, there are five species of fish considered primary prey fish: alewife, rainbow smelt, slimy sculpin, gizzard shad, and trout-perch.

Alewife

picture of alewife
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New York's waters are home to two forms of alewives: a sea-run form which reaches 15 inches in length, and a landlocked form which averages five to six inches in length. While both forms are prey for other fish species, it is the landlocked alewife (known to some as sawbelly or mooneye) that is especially important to New York State freshwater game fish and as such, will be discussed here.

The alewife is a small river herring with a gray-green back and silvery iridescent sides. It occurs in open water areas of large lakes and can be found as deep as 300 feet. A schooling fish, the alewife forms large groups in midwater. Alewives are native to larger rivers that run to the Atlantic Ocean (Delaware and Hudson Rivers) and colonized inland waters through canals or introductions. In New York, it is found in most of the Finger Lakes, parts of the Genesee and Delaware river systems, parts of the Lake Champlain watershed and, most notably, in the Great Lakes.

The alewife is an important forage fish for a number of popular gamefish species. In Lake Ontario, despite recent population declines, it remains the most important component of the forage fish community. Chinook and coho salmon, brown trout, rainbow trout/steelhead, and lake trout all rely upon alewives for their primary food source. In addition, smallmouth bass, walleye, and northern pike also consume a significant amount of alewives. As a result, abundant populations of alewives are necessary for ensuring that these gamefish grow to the large sizes that Lake Ontario is known for.

Recent research has revealed that alewives may also be affecting gamefish in adverse ways. Alewives are known to feed aggressively on the fry on some native species, including lake trout and yellow perch. Also, Atlantic salmon in the Finger Lakes and lake trout in Lake Ontario suffer reproductive impairments due to a deficiency of thiamine (vitamin B1), which is thought to be linked to a diet of predominantly alewives. Alewives contain high concentrations of an enzyme that breaks down thiamine, which, when liberated during digestion in the gut of a predator, destroys thiamine from the meal before it can be absorbed.

Alewives spawn (or reproduce) from the spring until mid-summer. Adult fish move from deep water to shallow water areas near beaches in lakes or in ponds over sandy or gravelly bottoms. Eggs are scattered at random and then abandoned. Young alewives eat zooplankton, adding insect larvae to their diets as they mature.

Alewife populations typically undergo extreme fluctuations in their numbers. During some years, Lake Ontario alewife populations have suffered large die-offs. Because of the problems associated with these population fluctuations, DEC and the Ontario Ministry of Natural Resources have adjusted stocking levels of trout and salmon to avoid an imbalance between the supply of alewives and their prey.

Rainbow Smelt

picture of rainbow smelt
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The rainbow smelt is a slender, elongated, pale fish that averages seven to eight inches in length. A distant relative of trout, salmon and whitefish, it has a greenish back and silvery sides with a bright silver stripe and brown or black spots. The large teeth and distinctive curved canines found in the mouth help distinguish this fish from the whitefish.

The rainbow smelt inhabits large, cool lakes and rivers. It is an important food item for a number of popular sportfish, including walleye, landlocked Atlantic salmon, lake trout and other trout, and salmon species. In New York, rainbow smelt are found in Lake Champlain, most of the Finger Lakes, Canadarago Lake, Neversink Reservoir, Lake George, some smaller Adirondack Lakes, the Great Lakes, the Lower Hudson River, and on Long Island.

Spawning takes place in the spring from March to May. Adult smelt migrate into tributary streams or onto shoals and scatter their adhesive eggs. The eggs sink and stick to the gravel bottom. After hatching, young smelt feed on zooplankton. Adult smelt eat crustaceans, insects, and other fish. In addition to their importance as a prey fish, rainbow smelt provide excellent fishing opportunities. Anglers catch smelt by ice fishing in the winter and dipnetting in the spring. In Canadian waters of Lake Erie, rainbow smelt are an important commercial fish species. As with alewives, a diet rich in smelt may result in a thiamine deficiency in predators.

Slimy Sculpin

picture of slimy sculpin
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Rather unusual in appearance, the slimy sculpin is a small fish (three to five inches long) with an enlarged, flattened head; a smooth, scaleless, brown colored body; and large, winglike pectoral (front side) fins. Small prickles or spines are located behind the pectoral fin and its eyes are positioned high on the head and close together.

Especially common in Lake Ontario and in waters in the Catskills and the Adirondacks, this fish is found in areas scattered across New York State. It is a bottom dweller and prefers cold, rocky streams and lakes with some shelter.

Spawning occurs in stony creeks or lake shallows during the spring. The eggs are laid in nests built in rock crevices. Male sculpins remain with the nest to protect the eggs and young. Adult slimy sculpin eat a variety of organisms, including insect larvae, large bottom dwelling invertebrates, and some small fish.

Slimy sculpins are an important prey fish for lake trout, brook trout, and northern pike. In addition, they are occasionally used as bait by anglers.

Gizzard Shad

picture of gizzard shad
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The gizzard shad is New York's only true freshwater member of the herring family. It has a distinct appearance with a blunt, rounded snout overhanging the small mouth, and a long filament on the back end of the dorsal (back) fin. Its deep body is generally silver with bluish upper sides and back. A medium-sized fish, adult gizzard shad average ten to 14 inches in length.

The gizzard shad is a quiet water fish that inhabits lakes, bays, and sluggish rivers. Although it can tolerate high turbidity, it prefers clear water. In New York, this shad occurs in the Mohawk River/Barge Canal, Chautauqua Lake, the Hudson River below Albany, the Great Lakes system, and in the Oswego and Genesee drainages.

Gizzard shad spawn during the summer in shallow water. Females scatter the adhesive eggs which sink to the bottom and stick to whatever they come into contact with. Gizzard shad are filter feeders and are one of New York's few freshwater fishes that eat mostly plant material, phytoplankton and algae.

While most anglers consider gizzard shad a nuisance species, they are an important food source for several gamefish, especially walleye. However, unlike the other prey fish mentioned here, gizzard shad are only vulnerable to predation during the early life stages. Adult shad are usually too large for most freshwater predators to effectively handle.

Trout-perch

picture of trout perch
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The trout-perch is a small, nearly transparent fish that averages three to four inches in length. Looking somewhat like a cross between a trout and a perch, it has an adipose (top rear) fin like a trout and spiny fin rays like a perch. A New York native, it is found in waters across the State.

Trout-perch occur in a variety of habitats ranging from shallow streams to a 200 feet depth in the Great Lakes. Bottom dwelling fish, they are usually found over sand and gravel and seem to avoid areas of rooted aquatic vegetation. They spawn in shallow, rocky streams from May through August. As in many other fish species, the adhesive eggs are scattered and then abandoned.

In lakes, adult trout-perch remain in deeper water during the day and then move into shallower water at night to feed on aquatic insects and small crustaceans. While anglers rarely encounter these fish, trout-perch are an important food source for walleye, northern pike, burbot, lake trout, brook trout, sauger, yellow perch, and freshwater drum.

Prey Fish and People

Prey fish play an important role in the fishing industry. Not only are they collected and used for bait, but the imitation of their appearance, behavior, and habits are the foundation of the tackle industry. Many lures are designed to attract sportfish by copying their prey.

Larger fish, such as trout, salmon, walleye, and bass, often develop what is called a search image. Simply stated, this means that after feeding primarily on a single preyfish species for so long, a fish will seek out food that looks and acts just like that preyfish. For years, anglers have used this knowledge of a species' search image to guide them in what methods and tackle to use while fishing. For example, anglers fishing for trout on Lake Ontario use lures which imitate the shape, color, and actions of alewives.

Understanding key behavior of prey fish provides anglers with other valuable information, as well. For instance, knowing the location of prey fish allows the angler to predict where the predators will be. Anglers have known for a long time that schools of small fish jumping out of the water indicates there are larger fish below feeding on these fish. By concentrating their fishing efforts in these areas, anglers increase their chances for success.

As stated earlier in this article, prey fish are a critical source of food for many of our popular sportfish. And while prey fish may not have a direct value consumptively for fisherman, they are a key to ensuring health populations of sportfish. Recognizing this, DEC places much importance on monitoring and managing New York State's important prey fish populations. For without these little fish, there would be no big fish.

Scientific Names

Many species of fish look alike, making it difficult to tell them apart. In addition, many types of fish have different common names in different parts of the country. To distinguish one organism from another, biologists give each a scientific name that is unique to that organism. The names are derived from the Latin language and consist of a genus and a species. The genus name is first and is capitalized. The species is second and is in lower case. Both the genus and species are either underlined or italicized when written. While several organisms in the same "family" share a common genus name (like family members sharing a last name), they have different species names. Occasionally, two members of a family are so similar that one is considered a subspecies of the other. In these cases, the organisms are given two species names. Here are the common and scientific names of New York's prey fish:

Scientific Names of Fish Species
Common Name Scientific Name
alewife Alosa pseudoharengus
rainbow smelt Osmerus mordax
slimy sculpin Cottus cognatus
gizzard shad Dorosoma cepedianum
trout-perch Percopsis omniscomaycus

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