Bycatch

By Kathleen Castro and Erik Williams

What is it?

Bycatch describes living creatures that are caught unintentionally by fishing gear. Unlike target species—animals specifically targeted for capture—bycatch is unwanted and often unused. Sometimes bycatch may be kept or sold; for example, and angler who catches a legal-sized bluefish while fishing for striped bass may keep the catch to eat at home or to sell, if he has a proper license. Other times, bycatch cannot be used—for example, if it is undersized or a protected species—and must be thrown back. This returned bycatch is called discard.

The problem

Everyone who fishes, whether for a living or recreation, catches bycatch. Unwanted bycatch is usually thrown back into the water; however, handling and exposure sometimes injure the bycatch, which may die after being discarded. Although this discard may serve as food for other species when it is thrown back, it is not recruited into, and does not become a part of, the reproducing population. As a result, discard not only affects the current population, but influences the species’ opportunity to replenish itself.

The National Marine Fisheries Service (NMFS), the government agency that manages fisheries, has called bycatch "the problem of the 1990s." Although the extent of the problem has not been satisfactorily determined, three areas of particular concern have been identified by NMFS:

• User conflicts, which happen when one fishery discards fish that are important to another;
• Laws, under which animals caught as bycatch are protected by the Endangered Species Act or the Marine Mammal Protection Act;
• Public regard, through which the public can affect fishing revenues by voicing opinions about the wastefulness of bycatch.

Bycatch in the Northeast

One of the main reasons bycatch is a problem in many fisheries is that different species of animals are found together: this is called a multispecies fishery. It is possible to catch any mix of whiting, flounders, hake, squid, cod, butterfish, or other species on a given day in a given place. Since these fishes attain different sizes when fully grown, it is hard to target only one of them in their shared habitat. However, efforts to adapt fishing gear to specific target species have resulted in more selective fishing. Appropriately, such gear is termed "selective."

Gear problems

Hook and line, and long-line:
Since most fish will bite a hook, it is hard to be selective with this gear. But anglers and commercial fishermen both can make their hooks more selective by using knowledge of fish behavior—for example, choosing bait, jigs, lures, and hook sizes known to catch their target species.

Traps:
In the Northeast, traps are used for catching lobsters, crabs, whelk, and some finfish. Because traps can attract both nonlegal and nuisance bycatch, they may be constructed in different sizes and shapes to be more selective to the behavior of the target species. Lobster traps must include escape vents to allow for the release of smaller, sublegal animals.

Gill net:
An important fishery in the Northeast and throughout the world, gill net fishing uses a panel of webbing, usually made of clear, monofilament line, that can be set at any depth. Fish can’t see the net, so they swim right into it and are caught. Gill net bycatch includes animals that are too large to pass through the webbing.

Bottom trawl:
This is the single most important fishing method in the Northeast, yet it produces the most noticeable bycatch problem. An bottom trawl is a funnel-shaped net that is dragged on the bottom of the sea. Much of the bycatch in an bottom trawl might not survive because it is damaged in the net, brought up from the depths too quickly, or thrown back too late.

Solutions

Fishermen and scientists have been working for many years to resolve the inefficiency and wastefulness of bycatch. One early response to the problem was the inclusion of escape vents and variably spaced laths, or slats, in traps to allow escape of nontarget species. More recently, educational programs for recreational anglers in catch-and-release fishing have helped minimize harm to fish. And the introduction of the Turtle Excluder Device (TED) in the southern shrimp fishery, and the similarly designed Fish Excluder device—the Nordmore Grate—in the Gulf of Maine fishery, has helped assure the release of nontarget animals from shrimp trawls. Other promising areas of research include the use of sound devices attached to gill nets to ward off dolphins and whales, and new designs of bottom trawls that take into account fish behavior.

As these examples attest, much progress has been made in reducing bycatch. With continued interest and concern, progress will continue, particularly in the following avenues:

Research and Development:
Ongoing research into fish behavior, application of new knowledge to the development and modification of fishing gear, and continued efforts to pinpoint specific bycatch problems should generate practical solutions to this important issue.

Education:
The availability of current information about the actual impacts of bycatch, and the progress being made in controlling the problem, should help clarify the issues and encourage cooperation in developing solutions. Conferences and other forums for public discussion enhance prospects for solutions.

Cooperation:
Cooperation among the public, the government, academia, environmentalists, and the fishing industry is essential if any proposed bycatch solution is to be effective. Such cooperation has a head start in the collaboration of fishermen, NMFS, and New Hampshire Sea Grant on the use of "pingers"—small acoustical devices—to warn harbor porpoises away from gill nets. In this, as in other responses to bycatch issues, the goal is the same for everyone—fish for the future.

Web site:

FAO Fisheries (Includes State of World’s Fisheries and Aquaculture)

Book:

Petruny-Parker, M.E., K.M. Castro, M.L. Schwartz, L.G. Skrobe, and B. Somers (eds.) 2003. Proceedings of the new England Bycatch Workshops. Rhode Island Sea Grant, Narragansett, R.I. 52pp. pdf.

BARNACLE

by Prentice Stout

Non-stalked barnacle

Barnacles are animals that are related to shrimp and lobsters. Because of the structure of their bodies, they have been placed in the phylum Arthropoda. Arthro means jointed, and poda means foot; hence, "jointed foot."

The taxonomy (that is, the classification) of the barnacle family, in addition to placing them in the phylum Arthropoda, also puts them in the class Crustacea and the order Cirripedia. Crustacea, in Latin, means "the shelled ones," and Cirripedia, roughly translated, means an animal with feet that are slender and wispy, like cirrus clouds.

Stalked barnacle

The most common barnacle belongs to the order Balanus. It is called the acorn barnacle (balanos, in Greek, means acorn). The species Balanus nubilus, found in Puget Sound, can reach a diameter of nearly a foot and is said to be good to eat.

Barnacles have existed since Jurassic times, the period in the earth's history during which dinosaurs lived. Fossils more than 150 million years old have revealed the presence of barnacles, whose ancestry can be traced back nearly 400 million years.

An eleventh century myth tells a story about one kind of barnacle, the goose barnacle (Lepas). The monks of those days were forbidden from eating meat during Lent, and they claimed that the barnacle goose, a bird, was simply a "grown up" goose barnacle. They argued that, being a fish, the barnacle goose could be eaten. Perhaps with a little imagination, the stalk, shell, and feathery cirri (feet) of the goose barnacle do look like those of an embryonic bird. in any event, the myth helped out those monks who wanted a hearty meal and gave the barnacle goose its name.

Barnacles live only in salt water. There are two kinds, the stalked barnacle (goose barnacle) and the nonstalked barnacle (acorn, or sessile, barnacle). Most barnacles are hermaphroditic; that is, they have both male and female reproductive organs. However, most barnacles must be fertilized by a neighbor, and that is one reason why they grow in large colonies. One scientist has estimated that the barnacles living along a half mile stretch of coastline can release a trillion young a year; many of these are eaten by other animals.

If barnacles are allowed to accumulate on a ship's hull, the ship will travel slower in the water, or it will have to burn more fuel to keep up its speed, than it would otherwise. A sixmonth growth of barnacles can result in having to burn 40 to 45 percent more fuel to maintain cruising speed. Removing barnacles from ships' hulls costs ship owners more than $125 million a year.

Although many new ideas have been tested, the best way to keep barnacles from growing on a ship's hull is still to paint the hull with copper bottom paint. The paint, which contains copper oxide, forms a toxic film that keeps cyprides (young, swimming barnacles) away from the hull.

The development of a barnacle takes place in two stages: a larval stage called the naupli, and a cyprides stage. In both of these stages of development the barnacles swim about freely, making up part of the mass of microscopic plants and animals collectively called plankton. During the later, cyprides stage they are attracted to other barnacles and use their front two antennae to crawl to a likely spot, where they will glue themselves and remain for life. The life span of most barnacles is from three to five years.

Inside its shell, the barnacle actually stands on its "head" and uses its "feet" to rake the plankton, which it eats. When the shell becomes too small to house the growing animal, a chemical is secreted which dissolves the inside of the shell and simultaneously builds up the outside. The barnacle's shell is made of limestone.

Barnacle cement, the substance the animals use to glue themselves to ships' bottoms and to rocks, has attracted the interest of doctors. A layer of this cement three tenthousandths of an inch thick over one square inch will support a weight of 7000 pounds. It is even stronger than epoxy cement. At temperatures above 6000°F the glue will soften but not melt, and at 380°F the cement will not crack. It does not dissolve in most strong acids, alkalies, organic solvents, or water. If man could learn to manufacture this cement, which barnacles have been using for millions of years, it could be used to mend broken bones and hold fillings in teeth.

Catch-and-Release Fishing

By Erik Williams and Malia Schwartz

Every recreational angler in every part of the country must at one time or another release fish. Minimum size regulations require many anglers to release sub-legal-sized fish or "shorts." Rivers, lakes, and reservoirs are areas where catch and release are particularly important. The increasing popularity of recreational fishing has led to the problem of too many people, too few fish. In some areas, only catch-and-release fishing is allowed. The increase in recreational anglers is not just limited to inland fisheries. Marine recreational angling is having a great impact on certain fish stocks as well. One of the primary means of allowing all these anglers to continue fishing and maintain healthy fish stocks is catch and release. Catch and release, whether it is voluntary or required, must be done properly if it is to succeed in having the fish survive. This fact sheet should help anglers to release fish properly to increase the likelihood that the released fish will survive.

Why Catch and Release?

With the cost of a typical fishing trip, the uncertainties of success, and the appeal of a fish dinner, why should anglers want to adopt the practice of catch and release? Aside from certain regulations, such as bag limits or size limits, there are a number of good reasons for releasing a portion of the catch alive.

First, catch and release offers a sensible way to extend the fishing trip after a reasonable or legal catch limit has been reached. If the trip involves a guide or charter service, catch and release can prolong an enjoyable recreational opportunity, giving anglers more value for their money.

Second, several recent studies have suggested that as anglers gain expertise in a particular fishery or fishing technique, they often develop an interest in "limiting their kill instead of killing their limit."

Why Do Hooked Fish Die?

Fish that are caught and released may die for several reasons, but the two primary causes are stress and wounding. Stress results from the fish fighting after being hooked. Internally, the physical exertion causes an oxygen deficit in the tissues, forcing the muscles to function anaerobically (without oxygen). This causes lactic acid to build up in the muscle tissue, and then to diffuse into the blood. Lactic acid acts as an acid in the blood, causing the pH of the blood to drop. Even slight changes in pH can cause major disruptions of the metabolic processes, ultimately killing the fish. If the fish is quickly released, its blood pH usually returns to normal and the fish will be unaffected. Some fish, after a long tow, may appear to live once released, but the imbalance in the blood chemistry may kill them as late as three days after being caught. In most cases, the means of preventing this type of mortality is to not keep the fish in action for a long period of time, unless the intent is to keep it.

The other primary cause of mortality is wounding by the hook. Injuries caused by hooks can range from very minor to lethal. The degree of injury is dependent on the location of the hook wound. Higher mortalities will occur in fish that are hooked in the gill or stomach areas, while lower mortalities occur in fish that are hooked in the lip, jaw, or cheek areas. Baited hooks are more likely to result in a gill or stomach hooking that artificial lures. Treble hooks, for obvious reasons, will result in more puncture wounds and subsequently higher mortalities. Barbless hooks facilitate release and decrease "out-of-water" time, but for reasons yet unclear, may not significantly reduce mortality, especially when used with bait.

There are other kinds of physiological stress that can lead to higher mortalities in released fish. Fish may not be able to adjust to changes in pressure or to higher surface water temperatures. Also, when a fish is handled or comes in contact with dry surfaces, such as landing nets or dry hands, its mucous layers – commonly called slime layers – may be partially removed, presenting an opportunity for bacteria or pathogens to invade the skin.

Burping and Puncturing

When certain fish are brought up from depths greater than 40 feet too quickly, their swim bladders, which normally control buoyancy, can overinflate from rapid depressurization. Burping is a technique used on a fish with an overinflated swim bladder. The fish is massaged in the belly region in an attempt to release the excess air in the swim bladder. Puncturing involves using a needle or ice pick to poke a hole in the fish’s exposed swim bladder. Both of these techniques are currently being advocated in other parts of the country. However, if the procedure is not carried out correctly, more damage than good may be done to the fish.

The success of burping depends on the species of fish. Some fish, such as largemouth bass, perch, striped bass, cod, hake, and black sea bass, do not have a connection from their gut to their swim bladder. If a fish’s gut is not connected to its swim bladder, then burping is impossible. Puncturing is a very controversial technique. To date, there is no evidence that puncturing will increase a fish’s chance of survival.

The best advice for releasing fish with overinflated swim bladders is to let them go as quickly as possible.

NEVER ATTEMPT TO BURP OR PUNCTURE A FISH WITHOUT KNOWING WHAT TO DO!

Catch-and-Release Guidelines

These guidelines provide basic information on the most beneficial catch-and-release methods for most small- to medium-sized freshwater and marine fish:

1. If you plan to fish with artificial lures, such as plugs and spoons, consider replacing treble hooks with single hooks. Single hooks are quicker and easier to remove, especially when dealing with such predatory fish as bluefish and northern pike. Consider pinching the barb on your hooks, since this will make releasing the fish much easier.
2. Plan your release strategy. Decide whether to keep or release any fish prior to angling or at least before removing the fish from the water. Familiarize yourself with any regulations in effect for the species targeted, and gather any items that will facilitate handling and releasing the fish.
3. When a fish is hooked, use a steady, deliberate retrieval technique. This can reduce the amount of stress a hooked fish undergoes when pulled up from the depths too quickly, or when physically exhausted from an overly slow retrieve.
4. Once you have decided on releasing the fish, avoid netting or even removing it from the water if possible. Use needle-nosed pliers to pry the hook from the fish while it is still in the water. Fish that can be lifted by the leader – the short length of line used to attach the end of the fishing line to the lure or hook – can easily be released over the rail using a "dehooker." These devices, whether homemade or purchased, are gaining in popularity in the bluefish industry – to avoid the fish’s nasty teeth – and are useful for releasing a number of other species. A dehooker may simply be a metal rod with a handle at one end and a small upturned hook at the other end. If live bait or a lure is deeply embedded in the fish’s gullet, cut the leader close to the fish’s mouth and let the fish keep the hook. Studies have shown that fish can get rid of the hook up to 120 days later.
5. When landing the fish, it is important to minimize out-of-water time and any fish contact with surrounding surfaces or objects.

• Avoid using landing nets if possible. If a landing net must be used, one with a neoprene bag rather than natural twine should be used. Neoprene removes less of the fish’s mucous coat.

• Do not use a gaff!

• Keep hands moistened. This helps prevent removal of the fish’s natural protective mucous layer, and reduces the chance of subsequent infections in the fish’s skin.

• Minimize handling, particularly of the gills and soft underbelly. Gently prevent the fish from battering itself on surrounding hard surfaces. Place the fish on an old piece of foam cushion and place a wet rag or gloved hand over the fish’s eye. These two actions can do much to subdue even unruly tuna and bluefish.

1. Return the fish to the water headfirst. In most cases, it is best to point the fish’s head straight down and allow the fish to plunge down into the water.

Sources:

Klauber, A. 1992. Catch & Release. In: Nor’easter: Magazine of the Northeast Sea Grant Programs. Fall/Winter 1992.

Malchoff, M.H., M.P. Voiland, and D.B. MacNeill. 1992. Guidelines to Increase Survival of Recreational Sport Fish. Cornell Cooperative Extension Fact Sheet.

Catch-and-Release Fishing

By Erik Williams and Malia Schwartz

Every recreational angler in every part of the country must at one time or another release fish. Minimum size regulations require many anglers to release sub-legal-sized fish or "shorts." Rivers, lakes, and reservoirs are areas where catch and release are particularly important. The increasing popularity of recreational fishing has led to the problem of too many people, too few fish. In some areas, only catch-and-release fishing is allowed. The increase in recreational anglers is not just limited to inland fisheries. Marine recreational angling is having a great impact on certain fish stocks as well. One of the primary means of allowing all these anglers to continue fishing and maintain healthy fish stocks is catch and release. Catch and release, whether it is voluntary or required, must be done properly if it is to succeed in having the fish survive. This fact sheet should help anglers to release fish properly to increase the likelihood that the released fish will survive.

Why Catch and Release?

With the cost of a typical fishing trip, the uncertainties of success, and the appeal of a fish dinner, why should anglers want to adopt the practice of catch and release? Aside from certain regulations, such as bag limits or size limits, there are a number of good reasons for releasing a portion of the catch alive.

First, catch and release offers a sensible way to extend the fishing trip after a reasonable or legal catch limit has been reached. If the trip involves a guide or charter service, catch and release can prolong an enjoyable recreational opportunity, giving anglers more value for their money.

Second, several recent studies have suggested that as anglers gain expertise in a particular fishery or fishing technique, they often develop an interest in "limiting their kill instead of killing their limit."

Why Do Hooked Fish Die?

Fish that are caught and released may die for several reasons, but the two primary causes are stress and wounding. Stress results from the fish fighting after being hooked. Internally, the physical exertion causes an oxygen deficit in the tissues, forcing the muscles to function anaerobically (without oxygen). This causes lactic acid to build up in the muscle tissue, and then to diffuse into the blood. Lactic acid acts as an acid in the blood, causing the pH of the blood to drop. Even slight changes in pH can cause major disruptions of the metabolic processes, ultimately killing the fish. If the fish is quickly released, its blood pH usually returns to normal and the fish will be unaffected. Some fish, after a long tow, may appear to live once released, but the imbalance in the blood chemistry may kill them as late as three days after being caught. In most cases, the means of preventing this type of mortality is to not keep the fish in action for a long period of time, unless the intent is to keep it.

The other primary cause of mortality is wounding by the hook. Injuries caused by hooks can range from very minor to lethal. The degree of injury is dependent on the location of the hook wound. Higher mortalities will occur in fish that are hooked in the gill or stomach areas, while lower mortalities occur in fish that are hooked in the lip, jaw, or cheek areas. Baited hooks are more likely to result in a gill or stomach hooking that artificial lures. Treble hooks, for obvious reasons, will result in more puncture wounds and subsequently higher mortalities. Barbless hooks facilitate release and decrease "out-of-water" time, but for reasons yet unclear, may not significantly reduce mortality, especially when used with bait.

There are other kinds of physiological stress that can lead to higher mortalities in released fish. Fish may not be able to adjust to changes in pressure or to higher surface water temperatures. Also, when a fish is handled or comes in contact with dry surfaces, such as landing nets or dry hands, its mucous layers – commonly called slime layers – may be partially removed, presenting an opportunity for bacteria or pathogens to invade the skin.

Burping and Puncturing

When certain fish are brought up from depths greater than 40 feet too quickly, their swim bladders, which normally control buoyancy, can overinflate from rapid depressurization. Burping is a technique used on a fish with an overinflated swim bladder. The fish is massaged in the belly region in an attempt to release the excess air in the swim bladder. Puncturing involves using a needle or ice pick to poke a hole in the fish’s exposed swim bladder. Both of these techniques are currently being advocated in other parts of the country. However, if the procedure is not carried out correctly, more damage than good may be done to the fish.

The success of burping depends on the species of fish. Some fish, such as largemouth bass, perch, striped bass, cod, hake, and black sea bass, do not have a connection from their gut to their swim bladder. If a fish’s gut is not connected to its swim bladder, then burping is impossible. Puncturing is a very controversial technique. To date, there is no evidence that puncturing will increase a fish’s chance of survival.

The best advice for releasing fish with overinflated swim bladders is to let them go as quickly as possible.

NEVER ATTEMPT TO BURP OR PUNCTURE A FISH WITHOUT KNOWING WHAT TO DO!

Catch-and-Release Guidelines

These guidelines provide basic information on the most beneficial catch-and-release methods for most small- to medium-sized freshwater and marine fish:

1. If you plan to fish with artificial lures, such as plugs and spoons, consider replacing treble hooks with single hooks. Single hooks are quicker and easier to remove, especially when dealing with such predatory fish as bluefish and northern pike. Consider pinching the barb on your hooks, since this will make releasing the fish much easier.
2. Plan your release strategy. Decide whether to keep or release any fish prior to angling or at least before removing the fish from the water. Familiarize yourself with any regulations in effect for the species targeted, and gather any items that will facilitate handling and releasing the fish.
3. When a fish is hooked, use a steady, deliberate retrieval technique. This can reduce the amount of stress a hooked fish undergoes when pulled up from the depths too quickly, or when physically exhausted from an overly slow retrieve.
4. Once you have decided on releasing the fish, avoid netting or even removing it from the water if possible. Use needle-nosed pliers to pry the hook from the fish while it is still in the water. Fish that can be lifted by the leader – the short length of line used to attach the end of the fishing line to the lure or hook – can easily be released over the rail using a "dehooker." These devices, whether homemade or purchased, are gaining in popularity in the bluefish industry – to avoid the fish’s nasty teeth – and are useful for releasing a number of other species. A dehooker may simply be a metal rod with a handle at one end and a small upturned hook at the other end. If live bait or a lure is deeply embedded in the fish’s gullet, cut the leader close to the fish’s mouth and let the fish keep the hook. Studies have shown that fish can get rid of the hook up to 120 days later.
5. When landing the fish, it is important to minimize out-of-water time and any fish contact with surrounding surfaces or objects.

• Avoid using landing nets if possible. If a landing net must be used, one with a neoprene bag rather than natural twine should be used. Neoprene removes less of the fish’s mucous coat.

• Do not use a gaff!

• Keep hands moistened. This helps prevent removal of the fish’s natural protective mucous layer, and reduces the chance of subsequent infections in the fish’s skin.

• Minimize handling, particularly of the gills and soft underbelly. Gently prevent the fish from battering itself on surrounding hard surfaces. Place the fish on an old piece of foam cushion and place a wet rag or gloved hand over the fish’s eye. These two actions can do much to subdue even unruly tuna and bluefish.

1. Return the fish to the water headfirst. In most cases, it is best to point the fish’s head straight down and allow the fish to plunge down into the water.

Sources:

Klauber, A. 1992. Catch & Release. In: Nor’easter: Magazine of the Northeast Sea Grant Programs. Fall/Winter 1992.

Malchoff, M.H., M.P. Voiland, and D.B. MacNeill. 1992. Guidelines to Increase Survival of Recreational Sport Fish. Cornell Cooperative Extension Fact Sheet.

Eelgrass (Zostera marina)

by Prentice K. Stout

To the scuba diver, eelgrass is a jungle, to many marine invertebrates and fish it is a haven and nursery. It is food for ducks and geese, and a fascinating study area for the scientist.

Eelgrass communities are excellent study habitats for those willing to get wet. Situated as they are close to the shores of quiet salt ponds and lagoons, a person with flippers and a snorkel can spend many productive hours swimming over these aquatic fields. A study of these areas heightens an understanding of their value both in the total coastal process and as a habitat for many commercially valuable marine species.

Recognizing Zostera is not hard - they have thin leaves about 12 to 20 inches long (31 to 53 centimeter) with parallel edges and three veins running along their length. While they are alive they are green, but when cast up on the shore they turn black, and eventually grayish-white when bleached by the sun.

Eelgrass is not a seaweed or algae; it is a true flowering plant and a monocot (a plant having a single seed leaf). This places it in a category unique among marine species. During the spring, as the water warms, millions of pollen grains are released and come in contact with the style of the female flowers. Deep in the ovary, fertilization takes place, and in August the eelgrass plants produce hundreds of tiny seeds. These units of reproduction sink to the muddy bottom or are carried away by currents to other sites, where they create new colonies.

Studies reveal that eelgrass communities are valuable as sediment traps that help stabilize the coastal zone. Because their leaves are so closely packed together they also act as dampers reducing the motion of the water. Suspended materials carried by currents move into these areas, where the waters are calmer, and there they sink to the bottom. The closely packed leaves also provide a haven for young fish species such as flounder and mummichogs. Larger, predatory species find it difficult to hunt in this aquatic jungle.

Birds such as geese and ducks consume the leaves of Zostera as a principal food source. In September, the leaves break away from the roots. Some float away, carried by currents; others fall to the bottom where at least 85 percent of them decompose. Certain microscopic organisms called Detritivores begin to break it down into smaller particles, and these become surrounded by bacteria and fungi. They, in turn, are consumed by filter feeders such as clams and scallops. Deposit feeders (sea urchins) and the sediment feeders (worms and snails) also consume this marine "soup." The adult and larval forms of these invertebrates become food for larger life forms such as fish. It is a continuous cycle of life and death and life again. So important is Zostera's role in this food cycle that estimates reveal that more than 20 species of commercially valuable fish species feed in these eelgrass meadows at some point in their lives.

The surface of the leaves form a substrate for many invertebrate species. In 1937, R.C. Stouffer subdivided the eelgrass invertebrate community into four major categories: those on the plants, among the plants, on the mud surface, and in the mud. Perhaps the invertebrates most easily seen in New England waters are two related worms that secrete about themselves a hard tube of calcium carbonate. Spirobus borealis and Spirobus spirillum look alike, but a little study reveals that Spirobus spirillum coils to the right and Spirobus borealis to the left. If placed in a marine aquarium, these worms will emerge displaying delicate plume-like appendages. Another species, the Bryozoans, will appear as a flat crust growing on the blades, but a magnifying glass or microscope will show the individual animal, or Zooecia, that makes up this colony.

A nursery, or shelter, and a food source for animals, eelgrass has also provided many benefits to humans. In some Scandinavian countries eelgrass was used as roof thatch and upholstery. Burned, it gave not only heat but soda and salt. Early historical records indicate that in the United States eelgrass brought $20 to $30 a ton as insulation and sound-deadening material. In the 1920s and 30s, the Samuel Cabot Company (which still markets stains) sold a product called Cabot's Quilt, which consisted of two layers of building paper with a layer of eelgrass stitched between in quilt fashion for insulation. A researcher's studies indicate that a six-inch layer of eelgrass spread to a density of 1.5 pounds per square foot has the insulation efficiency of six inches of fiberglass insulation. Further studies reveal that Zostera will burn if subjected to a flame but will not support combustion by itself.

The vital importance of eelgrass was first noted by Danish biologists in 1890, but it was revealed dramatically in 1931 when a serious fungal disease and a change in ocean currents that brought warmer waters to the extensive Atlantic Zostera meadows teamed up to kill this species. With this catastrophic decline, which killed over 90 percent of the North Atlantic eelgrass population, many species of ducks and geese vanished. In addition, lobster, crabs, scallops, clams, and other invertebrates declined. A vital part of the food chain in coastal areas had been removed, and the decline in Zostera also caused significant problems with coastal erosion. It was not until 1945 that a recovery began. Zostera is now once again abundant.

It is easy to see that eelgrass and the organisms that live in its grassy confines do not exist in isolation; each species is involved in a number of relationships and interactions. These relationships and interactions have two consequences: a flow of energy from the autotrophs (green plants and algae that make their own food) to the heterotrophs (organisms that eat green plants or each other) and the continuous cycling of inorganic materials which move through living (biotic) organisms and back to the environment. Such a complex combination of living and nonliving elements in a natural setting is referred to as an ecosystem. Ecosystems are large and complex. We can narrow this complex down to "habitat": that portion of an ecosystem in which a particular organism lives. Eelgrass lives in the salt pond ecosystem but has its own habitat within that ecosystem. A further refinement can be made by stating that organisms sharing a common habitat and interacting with each other create a community.

Lobster Shell Disease

By Barbara Somers

What is shell disease?
Researchers in the Northeast region first noticed shell disease in the 1980s. At that time, the disease appeared as little black spots affecting lobsters' shells. But in the past several years, shells have sometimes become fully infected by the disease, with the worst cases rotting the shells entirely.

Shell disease is caused by bacteria that invade from the outside of the lobster through pores in its cuticle-or the outermost layer of the shell-that cannot be seen by the naked eye. There is a range in the severity of the disease from shallow pits that eat away at the cuticle and cause those unsightly black spots to ulcerations-holes that fully penetrate the shell, causing the shell and the membranes underneath it to fuse together. This can stop the lobster from releasing its shell and can cause it to become stuck during the molting process and die. A lobster needs to molt in order to grow. It has been suggested that molting may be a defense mechanism against shell disease. By molting, the animal can get rid of the disease, if only temporarily, by losing its shell.

The disease does not taint the lobsters' meat, but makes shells so unattractive that they are too unappetizing to serve whole. The meat may be used for canning. Larger female lobsters are the most severely affected because they retain their shell for a longer period of time while carrying eggs. It can weaken lobsters so much that they are unable to carry their eggs to term and there have been several instances of molted shells found with the eggs still attached.

Some preliminary studies suggest the lobsters may be contracting the disease from alkylphenols, chemicals that are byproducts from industrial sources. These compounds are found in everything from detergents to surfactants (a surface-active substance), paints, and plastics, and have been found in higher concentrations in lobsters with shell disease than in unaffected animals. These compounds may be interfering with the lobster's normal hormonal system and stimulating the animal to begin molting too early. In the laboratory, it has been found that levels of the molting hormone in shell diseased lobsters are much higher than unaffected lobsters. Egg-bearing females do not molt during the nine-month period when they are carrying their eggs. More lobsters are getting shell disease, and the problem has spread from southern New England waters all the way to Maine. Thirty percent of lobsters in coastal areas of southern New England and Long Island Sound are now affected by shell disease. It's still unclear what's causing it to spread. Shell disease is not contagious from lobster to lobster, and biologists suspect that environmental factors such as water temperature or polluted run-off may be weakening the lobster's immune system and allowing the bacteria to grow faster than the lobster can fight it.

See also: The American Lobster fact sheet

Salt: In the Oceans and in Humans

by Prentice K. Stout

Salt is an essential component of human diets. All fish, reptiles, amphibians, birds, and mammals carry within their veins the elements of sodium, potassium, and calcium in almost the same proportions as the oceans. The "sea" within us has the same saltiness as the Precambrian seas of three billion years ago. Rachel Carson, in her book The Sea Around Us, gives us a clue to our origins: "When the animals went ashore to take up life on land, they carried part of the sea in their bodies, a heritage which they passed on to their children and which even today links each land animal with its origins in the ancient sea."

For humans, salt is as essential as water. We can perish from too little salt as we can of thirst. Salt regulates the exchange of water between our cells and their surrounding fluids. One component of salt, sodium (Na), is involved in muscle contraction including heartbeat, nerve impulses, and the digestion of body-building protein. Humans contain about eight ounces of salt. The amount of salt is regulated in our bodies by our kidneys and by perspiration.

What is salt? It is a compound and has a cubic crystalline form when seen under a scanning electron microscope. Its chemical formula is NaCl, or sodium (Na) chloride (Cl). The chlorine part (ion) accounts for 55% of the dissolved solids in sea water, while the sodium accounts for 30%.

The combined oceans contain about four and one-half million cubic miles of salt—enough to cover the entire depth of the United States to a depth of one mile.

Where did all this salt come from? Part of the salt content of earth came from the breakup of rocks by frost and erosion. The salt was locked in these rocks, and as the rain fell the dissolved salts were carried into the sea. The balance of the sea's salt was leached form the rocks beneath the sea's surface.

The sea is about 3.5% salt. Stated another way: for every 1,000 pounds of water, 35 pounds are salt; or we can say that the average salt content is 35 parts per thousand. In areas closer to the shoreline, this figure will vary because of evaporation and dilution. There is evidence that the salinity of the oceans has changed little since their formation. Through the process of evaporation and freshwater input, the salinity balance stays the same. In addition, much salt returns to land through salt spray or through the salt crystals that form nuclei for raindrops. It then finds its way back to the oceans.

Salinity is vital for animals that live in the ocean. Most marine organisms in the open ocean have body fluids whose salinity closely approximates that of the water around them. However, problems arise for marine organisms who live in the coastal environment. In the intertidal zones and estuaries, wide fluctuations demand mechanisms that will increase water uptake or remove salt. Some animals protect their internal salinity with shells or scales. Oysters thrive in low-salinity waters of 7 to 18%, but their predators (mainly starfish) cannot. Some species of fish can readily adapt to rapid changes in salinity, such as the common mummichog or killfish (Fundulus heteroclitus), which can tolerate a wide range of salinity. Perhaps this adaptation has permitted it to thrive in these stressful habitats. Particularly susceptible to salinity fluctuations are the eggs of many vertebrates and invertebrates.

Myths have arisen about salt. To spill salt at the table requires throwing a pinch over the left shoulder for good luck.

There are some examples of art that celebrates salt. In the Kunsthistorische Museum in Vienna resides a magnificent sixteenth-century Golden Salt Cellar, product of the craftsmanship of Benvenuto Cellini. Perhaps because of the myth about spilled salt, Leonardo da Vinci's famous "Last Supper" has a spilled saltcellar in front of Judas.

Salt could be used in Central Africa in the 1800s to purchase a bridge. The French, who detested the salt tax, the gabelle, began a revolution that helped to repeal the tax. In India, Mahatma Gandhi led a march to the ocean in protest against the British law that forbade Indians from making their own salt. "Why," reasoned Gandhi, "should they not march two hundred and forty miles to the shore where the salt from the sea was free?"

Poland's Wieliczka salt works is a museum made up of chambers with sculptures and chandeliers in salt 400 feet underground. Near Hutchinson, Kansas, a storage company operates the world's largest warehouse in a salt mine 650 feet beneath the surface—it covers 300 acres.

Some 14,000 uses have been found for salt. It is used in adhesives, batteries, explosives, meats, and metals. Before the days of refrigeration, people used to cure meats, thus preventing spoilage.

The next time you shake out some salt remember that it demands your attention. We all spent the first months of our lives in a sac of saline solution. We are dependent on this humble compound.

SHARKS

By Tony Corey

The word "shark" might evoke images of the massive, spike-toothed maw of the great white shark immortalized in Jaws. The great white as the archetypal shark emphasizes the dramatic characteristics often associated with sharks—imposing size, formidable jaw and crushing bite, swift and sure attack. But there is such diversity among animals carrying the name "shark" that the Hollywood stereotype can scarcely measure up.

Three hundred fifty species of sharks are identified worldwide, including 73 species known to inhabit U.S. Atlantic coast, Gulf of Mexico, and Caribbean waters. What identifies them all as sharks is the combination of paired fins, including pectoral fins whose rear edges are free rather than attached to the head; five to seven gill slits; and rough, sandpapery skin. Beyond these common characteristics, a wealth of variations distinguishes one shark species from another.

In size, they range from the appropriately named pigmy shark—smaller than 12 inches (30 cm)—to the enormous whale shark—at 40 feet (12 m) the largest fish in the oceans. In shape, they vary their missile-like profile with features such as the exaggerated tail (upper caudal lobe) of the thresher sharks or the wide, flattened head of the hammerhead sharks. One species may have a spined dorsal fin (the spiny dogfish); another may have whiskerlike nasal appendages, or barbels (the nurse shark).

Teeth, often an identifying characteristic, vary in shape and configuration according to diet and feeding habits. Those huge, triangular teeth familiar from Jaws have serrated edges that equip the white shark for cutting into a fare of seals, sea lions, porpoises, even sea turtles. The voracious sand tiger shark has long, slender, smooth-edged teeth with a small cusplet on either side; these teeth grasp small prey such as crabs, lobsters, and various finfish. Interestingly, the largest sharks—whale and basking sharks—are filter feeders, straining small organisms from the water. Both species have teeth featuring a single cusp curved backward. And both species have an exceptional number of teeth: The whale shark, for example, has 300 rows of dentition with hundreds of teeth in each row.

Evolutionary fitness

Fearsome teeth may contribute to sharks' hunting success, but other adaptations also enhance their effectiveness as predators. Sensitive smell receptors, eyes that can adapt to dim light, a receptor system that senses movement in the water, and electroreceptors that can detect prey buried in the sand secure the shark's status as apex predator.

While hunting capabilities have rewarded sharks as predators, reproductive adaptations have protected them as prey. Internal fertilization and production of fully developed young enhance sharks' evolutionary fitness. Although sharks are less prolific than many marine species, their reproductive strategies help ensure survival of the offspring that are produced. Pups are large and fairly developed at birth, so they have fewer potential predators than larval offspring.

Unlike bony fishes, shark young have the advantage of developing within the protection of the mother's body. Most sharks reproduce by ovoviviparity—producing embryos that hatch from eggs and then continue to grow in the uterus until fully developed. A few species, including whale sharks and some nurse sharks, still reproduce by laying eggs externally, a method known as oviparity. The eggs are protected by a tough, fibrous case that usually attaches to plants or rocks on the sea bottom till the young hatch. Hammerheads, smooth dogfishes, and most requiem sharks (the Carcharhinus family) reproduce by viviparity. This is the most advanced mode of reproduction, with the young nourished through the mother's placenta.

The same reproductive factors that have allowed sharks to dominate marine environments make them vulnerable to stock depletion in the face of intense human exploitation. Though born fully developed, sharks grow slowly and mature late—as late as 12 to 18 years of age in some species. They have a long reproductive cycle—generally one year but as long as two years for the spiny dogfish. And they produce few young per brood—usually two to 12, sometimes more depending on the species. In some cases, the small litter results from oophagy—literally "egg-eating": Embryos nourish themselves in the uterus by consuming the unfertilized eggs or smaller embryonic siblings. Consequently, only one embryo in each of two uteri survives to birth. All these factors combine to limit sharks' reproductive potential and hinder recovery from overfishing.

Protection from excessive harvesting and from practices such as finning, in which the valuable dorsal fin is removed and the carcass discarded, has been only patchy. Being highly migratory species, sharks are not constrained by international boundaries. They move up and down the coast or from estuaries to offshore or deepwater habitats, depending on species, season, and life stage. As they migrate, they slip in and out of regulatory jurisdiction and beyond the reach of national protection or conservation programs.

In 1999, the National Marine Fisheries Service (NMFS) finalized a fishery management plan for domestic management of sharks and for protection of their habitat in U.S. waters. Even without the international cooperation essential for effective management of highly migratory species, the NMFS management plan takes steps to prevent or end overfishing, rebuild depleted stocks, and identify and protect habitat for species included under NMFS management.

Protective management of sharks comes in response to rapid, intensive development of the fisheries. Although fished commercially for food and medicinal applications since the 1930s, sharks were considered an underutilized resource as late as the 1970s. Accelerating commercial catches through the 1980s and an expanding recreational fishery contributed to the stock decline addressed by managers in the 1990s.

Prehistoric to modern roles

Sharks have been adaptable enough to survive for more than 400 million years. Fossils in rocks from the Devonian period indicate that primitive sharks were small creatures less than 3.5 feet (100 cm) long, preyed upon by larger armored fishes that ruled the seas. On their way to becoming the dominant marine predators they are today, sharks evolved skeletons from true bone to cartilage. The lighter, more elastic cartilaginous skeleton helps these fast-moving distance swimmers maintain their position in the water. For identification purposes, it also defines them, along with rays, skates, and deepwater chimeras, as members of the class Chondrichthyes.

As predators near the top of the food web, sharks have few natural enemies other than humans. Their value to humans may vary according to species, geographic location, and management status. Along the Northeast coast, species such as blue sharks, makos, sand tiger sharks, and dogfishes have a market history.

Blue sharks have little value as food fish, but historically were captured for their fins. The practice of finning is now banned, and blue sharks are fished primarily for sport. Growing to 12 feet or more, these sharks are distinguished by their bright blue metallic-hued color and very long, narrow, pointed pectoral fins.

Makos have both commercial and recreational significance. The shortfin mako is the premier species for shark meat. And because it is one of the fastest fishes, and a fighter capable of leaping several times its length from the water, it is highly prized as a gamefish. The less familiar longfin mako is not so actively targeted.

Similar in appearance, the two makos were not recognized as separate species until 1966. About 13 to 15 feet long, both have dark blue coloring that lightens increasingly down the sides and belly; both have crescent-shaped tails, conelike snouts, and long, slender teeth. The primary difference is the length of their pectoral fins. Shortfin makos have shorter fins, about half to three-quarters the length of the head, while longfin makos have fins about equal to head length. Shortfin makos also display snow-white coloring around the mouth and snout.

Sand tiger sharks are popular for aquarium displays because they adapt better to captivity than most species. Their fierce-toothed appearance enhances their "shark" image, while their coloring—gray to light brown with scattered brownish spots—distinguishes them from other species.

Dogfishes are probably the most important commercial species in the Northeast. Spiny dogfish in particular gained prominence in the fishery with the depletion of cod, haddock and other groundfish stocks. Spiny dogfish meat is marketed in England for use in fish and chips. Smooth dogfish are more likely to have nonfood uses: in aquarium displays or as lab animals.

Despite their designation as dogfishes, smooth and spiny dogfishes are different families (Triakidae and Squalidae, respectively). Similar in size at 4 to 5 feet, they differ mainly in fin structure, with the spiny dogfish having dorsal fins each preceded by a single spine. The smooth dogfish has no spines, but has dorsal fins of nearly equal size.

REFERENCES
National Oceanic and Atmospheric Administration. Final Fishery Management Plan for Atlantic Tuna, Swordfish, and Sharks. Prepared by: Highly Migratory Species Management Division, Silver Spring, Maryland.

Castro, J.I. The Sharks of North American Waters. Texas A&M University Press. College Station. 1983.

Stevens, J.D. (consult. ed.). Sharks. Facts on File Publications. International Publishing Corp., Limited, New York, Oxford. 1987.

Shark Attacks

Steering clear of "Jaws"

By Tony Corey

"Respect" is the watchword when the subject is sharks. These intriguing animals are not to be feared necessarily, suggests one fisheries biologist, and not to be dismissed, certainly, but they are to be respected—respected for their size, for their power, and for their capacity to inflict considerable harm.

Shark sightings off Narragansett Town Beach in summer 2003 have made the scientist’s notion of respect a little more real for Rhode Islanders seeking a day of sun and surf. The sightings, though brief and uneventful, closed the beach for a couple of days and alerted Rhode Islanders to the presence of various sharks along the state’s coast. Familiar in southern and deep ocean waters, Atlantic sharks are highly migratory creatures: Different species travel as far south as Argentina, as far north as Newfoundland, and as far inland as bays, harbors, and estuaries. Summertime brings them to the northern range of their distribution, with some species routinely visiting Rhode Island waters. Among these, the blue shark, shortfin mako, sand tiger, sandbar shark, and the smaller, more familiar spiny dogfish and smooth dogfish cruise offshore or into shallow coastal waters. All these species are suspects in the Narragansett sightings; none is a type usually associated with attacks on humans.

Sharks have gained a fearsome reputation over the past half century, nurtured in part by media exploitation of the shark mystique. The exaggerated Hollywood image of Jaws, combined with highly publicized recent shark attacks that generated the media tag "Summer of the Shark" in 2001, has riveted public attention and colored public perception. Although media coverage tends to heighten awareness and reporting of shark attacks, it may also promote a perception that attacks are on the rise.

Worldwide, according to the International Shark Attack File (ISAF), the number of confirmed, unprovoked attacks has indeed increased steadily over the past century. However, the increase is directly correlated to an increase in human population: There are more people on the coasts, and there are more people engaged in recreation in the water, so there are more opportunities for encounters. Additionally, an improved ability to discover and investigate attacks, thanks to better technology and communication, has enhanced awareness and documentation of encounters. So, even though numbers of shark attacks are up, the rate of attacks is not, ISAF reports. In fact, since 2000, a downward trend both in numbers and in severity of attacks shows a drop in incidents from 85 to 72 to 60 in 2000, 2001, and 2002, respectively, and a drop in fatalities from 13 to 5 to 3 in the same years.

Not shark food

Sharks rarely attack humans without provocation. Like most animals, they bite what they perceive as food. Their most frequent human targets—surfers, followed by swimmers and divers—and their method of attack suggest "mistaken identity." The sudden, violent, single-strike approach that characterizes most attacks on humans is the most efficient strategy for hunting prey. A shark that mistakes a wet-suited diver or a surfer for a seal quickly learns this is not its normal food and usually abandons the attack. Such mistaken-identity encounters are the most common type of attack, and the resulting injuries—usually small lacerations, especially on the lower legs—are seldom life threatening.

More serious are the "bump and bite" and "sneak" attacks. These encounters usually occur in deeper waters and involve swimmers or divers. The shark initiates a bump-and-bite attack by circling its victim, typically bumping the target before attacking. Resulting injuries are usually severe and sometimes fatal. The sneak attack is a sudden assault that comes without warning. This is the kind of attack associated with sea disasters, as sharks engage in feeding or antagonist behaviors. Injuries sustained in such an attack are usually severe and often fatal.

Only a few species of sharks are implicated in the majority of unprovoked attacks: the white shark of Jaws infamy, the bull shark, and the tiger shark. These are not among the species that normally frequent Rhode Island waters.

As dramatic as they are, shark attacks are rare and largely preventable. People are 30 times more likely to be struck by lightning than attacked by a shark and are far more likely to die of stings or bites from bees, wasps, or snakes than from sharks. Still, the risk exists, and shark sightings warrant attentive response. The likelihood of shark attack can be lessened by adherence to these precautions:

• Always stay in groups; sharks are more likely to attack a solitary individual
• Stay fairly close to shore to avoid being isolated and cut off from ready assistance
• Avoid being in the water during darkness or twilight hours when sharks are most active and have a competitive sensory advantage
• Stay out of the water if bleeding from an open wound or if menstruating—a shark's olfactory ability is acute
• Remove shiny jewelry—the reflected light resembles the sheen of fish scales
• Avoid waters with known sewage or active sport or commercial fishing, especially if you see bait fishes or feeding activity. Diving seabirds are good indicators of such action
• Keep in mind that sightings of porpoises do not indicate the absence of sharks—both often eat the same food items
• Use extra caution when waters are murky; avoid uneven tanning and bright colored clothing—sharks see contrast particularly well
• Refrain from excess splashing; do not allow pets in the water because of their erratic movements
• Exercise caution when occupying the area between sandbars or near steep drop-offs— these are favorite hangouts for sharks
• Stay out of the water if sharks are known to be present, and evacuate the water if sharks are sighted
• Avoid harassing a shark if you see one

Information taken primarily from the International Shark Attack File (ISAF), a compilation of all known shark attacks from the mid-1500s to the present. In existence since 1958, the ISAF is administered by the American Elasmobranch Society, the foremost international society of scientists studying sharks, skates, and rays, and by the Florida Museum of Natural History (FLMNH). FLMNH maintains the ISAF Web site, http://www.flmnh.ufl.edu/fish/Sharks/ISAF/ISAF.htm.

Additional information from Guide to Sharks, Tunas & Billfishes of the U.S. Atlantic & Gulf of Mexico, 2003, a joint publication of Rhode Island Sea Grant and NOAA Fisheries.

See also: Sharks in Rhode Island waters slideshow on Projo.com. Note: Viewing this slideshow requires Macromedia Flash Player.

Striped Bass

by Amanda Argentieri

The striped bass, Morone saxatilis, has long been one of the most important commercial and recreational species found along the Atlantic coast. Also known as the striper, rockfish, linesider, and roller, the striped bass has been a sought-after finfish since the colonial era. New England Indians and European settlers caught and dried the fish in abundance. Along with cod, striped bass was one of the first natural resources to be regulated by early conservation measures. For example, in 1639, the Massachusetts Bay Colony passed a law that neither species could be sold as fertilizer. By 1776, New York and Massachusetts prohibited all sales of the fish in the winter months. Continuous harvesting of striped bass continued into the 20th century, but a severe decline in total landings experienced in the 1970s resulted in the development of increased regulation and conservation actions. Today, the striped bass is still a popular species fished both commercially and recreationally. However, preservation and protection remain primary issues in the management of this fishery.

Physical Characteristics
The adult striped bass, known for its size and fighting ability, weighs on average 4 to 7 kilograms (kg) (8 to 15 pounds (lbs)). However, bass exceeding 23 kg (50 lbs) are caught every year. The length of the fish also varies considerably from 46 to 140 centimeters (18 to 55 inches (in)). Its coloring can be light green, olive, steel blue, black or brown, with a white or silver iridescent underside. This stout-shaped fish also can be identified by its seven to eight continuous horizontal stripes on each side of the body from gills to tail.

Distribution
The striped bass is found along the western Atlantic coast from the St. Lawrence River in Canada to the St. Johns River in Florida. The species also inhabits the waters west of the Swanee River, Fla. to Lake Pontchartrain, La. In addition, striped bass has been successfully introduced along the Pacific coast and to inland reservoirs and lakes nationwide. Striped bass is classified as an anadromous fish, meaning it migrates from salt water to fresh water during the spawning season. North of Cape Hatteras, some striped bass stocks participate in coastal migrations—north in the summer, and south during the late fall and winter.

Habitat
Striped bass prefer large bodies of deep, clear water with a temperature between 65F and 70F (18C and 21C). Mature bass can be found in a variety of inshore, estuarine, and freshwater habitats depending on the location and season. Most striped bass remain in inshore waters, and are not usually found more than eight kilometers (five miles) from the coast. Young bass are typically found in river systems and estuaries, which are critical spawning and nursery grounds for the species.

Reproduction
The spawning activities of striped bass are triggered by an increase in water temperature, and occur near the surface in fresh or slightly brackish waters. Depending on the latitude, adult striped bass travel inland to their natal rivers to spawn during the late spring or early summer. Male bass reach sexual maturity at two years, while females usually do not spawn until age four. During the spawning process, the female releases her eggs into the water column to be fertilized by the males. The fertilized eggs must remain in the water column—any that settle to the bottom are smothered and killed. Depending on the water temperature, the eggs can hatch 25 to 109 hours after fertilization. The larvae are 2.0 to 3.7 millimeters (0.08 to 1.5 in) at hatching. The duration of the larval stage is 23 to 68 days, depending on water temperature. The larvae begin feeding after 6 to 8 days. By day 30 to 50, the larvae have transformed into juvenile fish, taking the body shape of an adult bass.

Diet
Striped bass are nocturnal feeders. Larval striped bass feed on zooplankton, while the diet of juvenile bass consists of insect larvae, small crustaceans, mayflies, and other larval fish. Adult bass are considered piscivorous (fish-eating). They eat almost any kind of small fish as well as several invertebrates, particularly crabs and squid.

Fishery
Striped bass are caught commercially using gill nets, pound nets, hook-and-line, and haul seines. Both the commercial and recreational striped bass fisheries rely heavily on the production from populations spawning in the Hudson, Delaware, and Roanoke rivers, and the Chesapeake Bay system. Historically, Chesapeake Bay has produced the majority of the striped bass found along the Atlantic coast. However, poor juvenile production in the 1970s and 1980s caused a severe decline in commercial and recreational landings. The cause of this sudden decline has been attributed to several factors, including overfishing, poor water quality in spawning and nursery areas, contaminants, natural stresses, and pollution.

Protection & Management
The rapid deterioration of the striped bass fishery was addressed at both the state and federal level through legislation and management plans. In 1984, Congress passed the Striped Bass Conservation Act, which allowed the Atlantic States Marine Fisheries Commission to develop an Interstate Fisheries Management Plan for Striped Bass. Under the plan, states along the eastern seaboard were required to comply with certain size limits, seasonal closures, recreational daily bag limits, and annual commercial catch quotas to help rebuild the stocks. In 1995, Atlantic striped bass was officially declared a restored stock, and the strictest regulatory measures were relaxed.

Other methods of conservation include water pollution control, artificial stocking, and the use of hormones to promote female ovulation. Also employed are fishways, a device that allows striped bass to swim past dams and other obstructions while migrating upstream to spawn. In addition, scientists and aquaculturists have successfully crossed the striped bass with white bass to create a silvery hybrid with dark, broken lines. This hybrid is raised in fish farms and sold in fish markets.

The striped bass fishery is thriving once again, but under tight regulation. Scientists, fishermen, and state and federal governments continue to examine methods to protect this species by improving conservation techniques and enforcing proper management measures.

References

Collette, B.B., and G. Klein-MacPhee (eds.). 2002. Bigelow and Scroeder’s Fishes of the Gulf of Maine, Third Edition. Smithsonian Institution Press, Washington.

Groman, D.B. 1982. Histology of the Striped Bass. American Fisheries Society, Bethesda.

Setzler, E.M. et al. 1980. Synopsis of Biological Data on Striped Bass, Morone saxatilis (Walbaum). Dept. of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Washington.

Wirtanen, L.J., and R.H. Ray. 1970. Striped Bass Morone saxatilis (Walbaum): 1970 Report on the Development of Essential Requirements for Production. U.S. Dept. of the Interior, Fish and Wildlife Service, Bureau of Sport Fisheries and Wildlife, Division of Fish Hatcheries, Atlanta.

Websites

NOAA Fisheries Northeast Fisheries Science Center

Chesapeake Bay Program: Striped Bass

Swordfish

By : Malia Schwartz, Deborah Grossman-Garber, and Henry Milliken

The swordfish (Xiphias gladius Linnaeus 1758), also called the broadbill, is the only member of the family Xiphiidae. As its name implies, this magnificent fish is characterized by an upper jaw that extends to form a flat, sharp-edged "sword." Swordfish are impressive jumpers and powerful fighters—thrilling for anglers and boaters alike.

Physical Characteristics

The swordfish has a stout, fairly rounded body and large eyes. The first dorsal fin (rising from the back of the fish) is tall and crescent-shaped. The second dorsal fin is quite separate from the first and very small. Both are soft-rayed—having thin, bony rods that extend from the base of the fin and support the fin membrane. The anal fins approximate the shape of the dorsal fins, but are noticeably smaller. Ventral fins, found on the underside of fish, are absent. There is a strong, longitudinal keel, or ridge, on either side of the caudal peduncle (the base of the tail where the tail fins project from), which leads to a broad, crescent-shaped tail. Adult swordfish have neither teeth nor scales.

The swordfish snout elongates into a true sword shape. Measuring at least one-third the length of the body, it is long, flat, pointed, and very sharp. The lower jaw is much smaller, though just as pointed, ending in a very wide mouth.

The bodies of swordfish fry (recently hatched fish larvae) are quite different form those of the adults. Their upper and lower jaws are equally prolonged; bodies are long, thin, and snakelike; they are covered with rough, spiny scales and plates; tails are rounded; and they have just one long dorsal and anal fin.

Swordfish coloration varies greatly among individuals. The dorsal side can range from dark brown to grayish-blue. This dark shading can extend anywhere from halfway down the side to almost the full extent of the body. The remaining area of the skin is tinged silvery white.

In Northeast waters, only the spearfish bears any resemblance to the swordfish. It is distinguished from the swordfish by its rounded sword, small teeth, a long, continuous dorsal fin, and ventral fins.

Size

Swordfish are very large fish. Today, the average fish caught in the commercial fishery weighs between 90 and 150 kilograms (1 kilogram equals 2.2 pounds). While fish over 200 kg are unusual, the largest recorded in the North Atlantic ocean weighed 550 kg. The largest fish to be caught on a tackle weighed 274 kg. These larger fish measure approximately 4.5 meters in length (1 meter equals 3.3 feet)—with a 3 meter body and a 5 meter sword.

Female swordfish grow faster, live longer, and are proportionally heavier than their male counterparts. Research shows that by 1 year of age, the female is already almost 4 kg. During the next 2 years, she triples her weight of the previous year. By age 4, the female is likely to weigh 70 kg, and at age 5, 110 kg. Similar data for males and older swordfish are inconclusive.

Longevity

Swordfish reach sexual maturity at about 2 to 3 years of age, and live for at least nine years. While they may survive longer, no such documentation exists. The majority of swordfish caught in the North Atlantic sport fishery are thought to be 4 to 5 years old.

Distribution

Swordfish are pelagic fish—living within the water column rather than on the bottom or in coastal areas. They are typically found at depths of between 180 meters and 580 meters, and are found worldwide in temperate and tropical waters. They are believed to prefer waters where the surface temperature is above 15°C (58°F), although they can tolerate temperatures as low as 10°C (50°F). There seems to be some correlation between larger size and the ability to tolerate colder temperatures. Few fish under 90 kg are found in waters less than 18°C (64°F).

Swordfish are summer and fall visitors to New England waters, entering the warming Atlantic coastal waters from far offshore in the Gulf Stream around June and departing in late October. Evidence suggests that such onshore-offshore seasonal migrations are more prevalent than are migrations between the northern feeding areas off Cape Hatteras and the southern spawning grounds off Florid and the Caribbean.

Behavior

Swordfish are not schooling fish. They swim alone or in very loose aggregations, separated by as much as 10 meters from a neighboring swordfish. They are frequently found basking at the surface, airing their first dorsal fin. Boaters report this to be a beautiful sight, as is the powerful jumping for which the species is known. This jumping, also called breaching, is thought by some researchers to be an effort to dislodge pests, such as remoras or lampreys. It could also be a way of surface feeding by stunning small fish as they jump out of the water, making the fish more easily captured for food.

Swordfish feed daily, most often at night when they rise to surface and near-surface waters in search of smaller fish. They have been observed moving through schools of fish, thrashing their swords to kill or stun their prey and then quickly turning to consume their catch. In the western North Atlantic, squid is the most popular food item consumed. But fish, such as menhaden, mackerel, bluefish, silver hake, butterfish, and herring also contribute to the swordfish diet.

Swordfish are vigorous, powerful fighters. When hooked or harpooned, they have been known to dive so quickly that they have impaled their swords into the ocean bottom up to their eyes. Although there are no reports of unprovoked attacks on humans, swordfish can be very dangerous when harpooned. They have run their swords through the planking of small boats when hurt.

The adults have few natural enemies, with the exception of large sharks and sperm and killer whales. They are easily frightened by small boats, yet paradoxically, large craft are often able to draw very near without scaring them. This makes swordfish easy to harpoon.

Fisheries

Today, swordfish are caught in gill nets, with harpoons, and, most successfully, on longlines consisting of a main line, usually several miles long, which is supported in the water column by floats and from which baited hooks are suspended. In addition, swordfish are often an incidental catch in the tuna fishery.

The sport fishery normally fishes for swordfish by trolling and drift-fishing, using rod-and-reel gear. The catch rate has increased considerably since fishermen began in the mid-1970s to fish for swordfish at night using drifting baited lines.

Once almost unsalable, swordfish meat gained in popularity during World War II and continued through the early 1970s. In 1971, the U.S. and Canadian swordfish fishery was essentially terminated following U.S. Food and Drug Administration (FDA) restrictions imposed on the sale of swordfish found to have levels of mercury in the flesh higher than 0.5 parts per million (ppm).

But gradually, the U.S. fishery began to rebound. In 1979, the FDA raised the acceptable mercury level to 1.0 ppm, based, in part, on a National Marine Fisheries Service study, showing that a 1.0 ppm action level would adequately protect consumers. Finally, in 1984, the FDA switched from enforcing the mercury action level based on total mercury concentration to methyl mercury concentration. This change occurred for two reasons: (1) It was determined that methyl mercury was the toxic component of the total mercury concentration, and (2) a test specific for methyl mercury became available. Since then, both catch and fishing effort have been exceedingly high in the Atlantic Ocean, with swordfish meat commanding top prices in the marketplace.

While swordfish sold on commercial markets is closely monitored to make sure that methyl mercury levels remain below the 1.0 ppm action level, most experts urge those concerned about chemical contaminants to take certain precautions:

1. Eat a variety of different fish; don’t restrict yourself to swordfish.
2. Avoid eating excessive amounts of any single type of fish.
3. Avoid eating the internal organs of the fish—they typically contain higher contaminant concentrations than the flesh.
4. When catching your own swordfish, check and follow all applicable health advisories.
5. High-risk individuals—pregnant women, women of childbearing age, and children under age 15—should limit their consumption of swordfish. Pregnanat or nursing mothers should limit their consumption to once a month.
6. If you choose to eat a sport-caught swordfish that may contain elevated levels of contaminants, trim away fatty areas and use cooking methods like baking or broiling, to allow fats and juices to drain away.