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-- S w o r d f i s h --
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| Q 1. | ||
| What material composes the "sword" of the swordfish? |
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| Q 2. | ||
| What is the sword of a swordfish composed of? |
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| Q 3. | ||
| What is the best method of cleaning swordfish swords so that they will turn white? The only way I know of, immersing the swords in salt water, is very time-consuming. |
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| Q 4. | ||
| Would like some information on the swordfish caught off Block Island in the summer. How far north does it migrate? Is it found off Florida, California and in the Mediterranean? |
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| Q 5. | ||
| Some time ago I caught a broadbill swordfish off No Man's Land, Massachusetts. It appeared normal in every respect and weighed about 350 pounds. However, at the market I was told that the fish was a "jellied" type. The meat presented a mealy, soft appearance. Could you tell me what is known about this disease or condition? |
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| Q 6. | ||
| Are there swordfish in Florida waters? |
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| Q 7. | ||
| Is the dark meat in swordfish good or bad to eat? One of my friends says this is some form of cancer that affects the fish and should be removed-never cooked and eaten. I say this is not so. Who is right? |
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| Q 8. | ||
| What is the best method of cleaning swordfish or marlin bills so they will turn white? |
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| Q 9. | ||
| Recently a seven foot broadbill swordfish was caught inside a harbor at Abaco Island, Bahamas. Are there any other reports of swordfish being taken in shallow waters? |
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| Q 10. | ||
| I am sending you what I believe to be the bill of a small broadbill swordfish. I took it from the stomach of a 30 pound dolphin caught in the Straits of Florida. If it is a swordfish bill, how could a dolphin of this size have swallowed it? I was not aware that swordfish ran in the Straits. Have you heard of many being caught in this area? |
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| Q 11. | ||
| How could I determine the sex of the broadbill swordfish that I caught in the waters east of Martha's Vineyard? |
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| Q 12. | ||
| It is my understanding that the swordfish is very rare. If this is true, could you clarify the rumor that restaurants serving swordfish are actually serving shark meat. I have eaten shark meat, in Europe during World War II, but I cannot remember its flavor. |
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| Q 13. | ||
| I recently noticed a mako shark and a swordfish going at each other. I wasn't aware that they are natural enemies. Also, I've seen a number of swordfish stranded in shallow water. There didn't seem to be anything wrong with them. Can you explain this behavior? |
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| Q 14. | ||
| When I was at Bailey’s Island, Maine, someone caught a fish which, when compared to a published picture, appeared to be Luvaris imperialis. Could you provide information about this unusual fish? |
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| Q 15. | ||
| I caught two broadbill swordfish at night and both had a brownish-gray appearance with a light-colored underside. The taxidermist who mounted the fish, however returned them to me with a definite dark-blue upper half I have also seen illustrations of the swordfish with a bronzelike color: What is the true, natural color of this fish? |
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| Q 16. | ||
| I have heard that the swordfish is able to keep the temperature of its brain above that of the surrounding water? Can that be possible? |
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| Q 17. | ||
| Is the "sword" of the swordfish made of bone? |
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| Q 18. | ||
| I have been involved in the swordfish harpoon fishery for the past five years. The fish are visually located when they fin, that is, when they rest at the surface with their tail and dorsal fin exposed. Why do swordfish fin? Also, why does the number of fish finning vary greatly from year to year? |
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| Q&A 1. | What material composes the "sword" of the swordfish? |
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| The "sword" or "bill" of the swordfish is composed of thickened and hardened bone covered by a hard and somewhat spiny skin. In the very young swordfish both jaws are elongated and contain teeth, but the teeth are eventually lost and the upper jaw soon outgrows the lower one. Swordfish have been known to drive their swords through several inches of planking when hooked, but stories of them deliberately killing whales by spearing them to death are entirely without foundation. |
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| Q&A 2. | What is the sword of a swordfish composed of? |
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| Swordfish, sailfish and marlin "swords" are composed of hard, compact bone covered with a horny sheath of skin. Although the sword is commonly supposed to be the "nose" of the ,fish, the bones farming this structure are actually the enormously expanded maxillary, or upper jaw bones. In the very young stages of the fish, the jaw bones are quite short, but they grow progressively longer as the fish matures. |
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| Q&A 3. | What is the best method of cleaning swordfish swords so that they will turn white? The only way I know of, immersing the swords in salt water, is very time-consuming. Nova Scotia, Canada |
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| The best method of bleaching swordfish swords is to immerse them in a 1 to 2 % solution of potassium hydroxide in sunlight for about a week. This breaks down the fleshy material, leaving the white bone. The swords should then be washed thoroughly in fresh water and dried. Many people prefer not to remove the fleshy material but to dry the swords thoroughly, paint them in a color as close to the natural color as possible, and cover the paint with several coats of clear lacquer. |
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| Q&A 4. | Would like some information on the swordfish caught off Block Island in the summer. How far north does it migrate? Is it found off Florida, California and in the Mediterranean? Birmingham, Michigan |
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| The swordfish occurs around the world in tropical and temperate waters, and lives in all three areas you mention. The young are often taken in net collections but little is known about the spawning area itself. Apparently breeding occurs, at least in the Atlantic, mostly in tropical waters. The young then proceed toward higher latitudes. Young swordfish are found commonly in the Florida Current, although only occasional adults are seen there. Swordfish appear in the areas of Block Island, Nantucket Shoals and George's Bank in late Mayor early June, but seldom do they reach the area of Nova Scotia or the Gulf of Maine before July. In this northern region they are most common in July and August. Few swordfish have been recorded to or beyond the Gulf of St. Lawrence. In the eastern Atlantic it might be presumed that they extend farther northward due to the influence of the Gulf Stream, but none are recorded from the northern waters of western Russia. |
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| Q&A 5. | Some time ago I caught a broadbill swordfish off No Man's Land, Massachusetts. It appeared normal in every respect and weighed about 350 pounds. However, at the market I was told that the fish was a "jellied" type. The meat presented a mealy, soft appearance. Could you tell me what is known about this disease or condition? Pittsburgh, Pennsylvania |
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| Jellied condition in fishes has several causes. In a recent study of this condition in flounder it was attributed to lack of protein, due to the failure of fish living in very cold water to recover body protein loss after spawning and absorbing water to replace it. In swordfish, tuna and other large pelagic fishes it seems to be caused by parasites. A report entitled "Jellied Swordfish" was distributed in 1937, by The Atlantic Biological Station, St. Andrews. N. B., Canada. |
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| Q&A 6. | Are there swordfish in Florida waters? Guilford, North Carolina |
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| Swordfish are seldom taken by anglers in the waters off Florida, although they apparently are not as rare as their absence from angler catches would indicate. Recently Cuban fishermen have caught swordfish in considerable numbers out of Key West and along the Keys. Several are caught each year off the Florida coast, especially out of Fort Lauderdale. Adult swordfish probably live at considerable depths in southern waters; they are known to spawn around Florida as well as at other places off the South Atlantic coast and in the Gulf of Mexico. Young swords commonly are taken from dolphin stomachs and from plankton tows. For further information refer to a paper by George F. Arata in Bulletin of Marine Science of the Gulf and Caribbean, Volume 4, Number 3 (1954). |
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| Q&A 7. | Is the dark meat in swordfish good or bad to eat? One of my friends says this is some form of cancer that affects the fish and should be removed-never cooked and eaten. I say this is not so. Who is right? La Canada, California |
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| Swordfish and marlins, as well as the fishes of the tuna family, all have a lateral band of darker muscle just below the skin. It is probably not the presence of many blood vessels in this muscle that accounts for the color, but larger amounts of the respiratory pigment myohematin in the sarcoplasm of the muscle fibers, which maintains the high metabolic activity of these fishes. In some tunas, for example the temperature of this muscle is 9° Centigrade higher than the surrounding water and several degrees warmer than that of the adjacent muscle, but these figures were probably recorded from a fish which was exhausted by a fisherman. The meat is perfectly good, although somewhat bitter because of the blood in it. The Japanese prefer this meat, which they call "chiai," and it is dried and used as candy by them. It is extremely nutritious, and in no way related to cancer. While most persons remove this meat because of the flavor, perhaps proper preparation would cause it to lose its bitterness. |
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| Q&A 8. | What is the best method of cleaning swordfish or marlin bills so they will turn white? Wedgeport, Nova Scotia |
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| Bills can be bleached by immersing them in a 1 to 2 per cent solution of potassium hydroxide in sunlight for about a week. This breaks down the fleshy material, leaving the white bone. The sword should then be washed in fresh water and dried. |
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| Q&A 9. | Recently a seven foot broadbill swordfish was caught inside a harbor at Abaco Island, Bahamas. Are there any other reports of swordfish being taken in shallow waters? Cincinnati, Ohio |
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| The occurrence you relate is uncommon but not unique. In late 1965, two lifeguards wrestled ashore a 300-pound swordfish (Xiphias gladius) that had ventured into the surf of Miami Beach. IOF Board member P.A.B. Widener has seen swordfish in shallow water in the Bahamas. Swordfish live in relatively cool water. Off Florida and the Bahamas they are generally found quite deep - from 300 to 600 feet. Only on dark days or at night do they seem to venture to the surface. Possibly, specimens found in shallow water are sick. Another possibility is that they become confused or trapped after pursuing prey from deep water into the shallows. |
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| Q&A 10. | I am sending you what I believe to be the bill of a small broadbill swordfish. I took it from the stomach of a 30 pound dolphin caught in the Straits of Florida. If it is a swordfish bill, how could a dolphin of this size have swallowed it? I was not aware that swordfish ran in the Straits. Have you heard of many being caught in this area? Fort Lauderdale, Florida |
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| You are correct in your identification of the specimen as a broadbill. We estimate the fish to have been between 26 and 30 inches long. Actually, a swordfish of this size is not very heavy, being shaped rather like a needle-fish. By the time it grows to about 3 to 31/2 feet it has taken on a much chunkier appearance. Swordfish are relatively common in the Straits of Florida, but are seldom seen or caught by sports fishermen. In our plankton tows we find many small swordfish, from 1/4 inch to 2 inches, during nearly every month of the year. Apparently there are some very large swordfish in deeper waters, and for years the Cuban fishermen have taken these on hand lines. From time to time small swordfish of 3 to 5 pounds are taken by anglers drift fishing, and we take swordfish of various sizes from the stomachs of dolphin and blue marlin. |
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| Q&A 11. | How could I determine the sex of the broadbill swordfish that I caught in the waters east of Martha's Vineyard? Bronxville, New York |
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| There is no way known to determine the sex in this group of fishes through external examination. This means that the only way to find the sex of a swordfish, or any other species of billfish, is to cut open the body cavity and examine the gonads. In many groups of fishes this is a fairly easy matter, as the ovary is round, orange and granular, and the testis is flat, white, and smooth. The billfishes, however, present difficulties in this respect, because frequently the ovary is flat, and the testis arranged in a "celled" fashion. As the breeding season approaches, the small eggs in the ovary become more evident, and sex determination is made easier. Unfortunately, none of the fishes caught in northern waters are approaching maturity. The authors of The Fishes of the Gulf of Maine found over a period of many years only three fishes with ovaries containing eggs in early stages of development. They state that the occurrence of fish with even tiny eggs in an extremely unusual event in New England. Thus there is no easy way to identify the sex of a broadbill swordfish caught in New England waters. The body cavity must be opened and the paired gonad examined. In adults, a cross-section of the gonad should reveal some tiny eggs, unless it is in the refractive period that occurs right after spawning, when all mature eggs have been shed. |
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| Q&A 12. | It is my understanding that the swordfish is very rare. If this is true, could you clarify the rumor that restaurants serving swordfish are actually serving shark meat. I have eaten shark meat, in Europe during World War II, but I cannot remember its flavor. Boca Raton, Florida |
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| Swordfish are abundant in several parts of the world. In the United States the main fisheries operate off New England, North Carolina, and Southern California. Swordfish are not rare in Florida waters, but are not actively fished for market, except out of Key West. Most of the swordfish served in restaurants in this country is in the form of frozen steaks originating out of New York, New England or North Carolina. There is also a considerable fishery for swordfish in the Atlantic and the Pacific by Norwegian, Japanese, and Canadian longlining vessels, and some of this catch reaches U.S. markets. There is thus probably little shark meat sold as swordfish in this country. Although shark meat is quite good, it requires some preparation to render it edible, and there would be little economic impetus for such deception. |
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| Q&A 13. | I recently noticed a mako shark and a swordfish going at each other. I wasn't aware that they are natural enemies. Also, I've seen a number of swordfish stranded in shallow water. There didn't seem to be anything wrong with them. Can you explain this behavior? Tasmania, Australia |
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| There have been a number of sightings by fishermen of mako sharks fighting with swordfish, especially off Long Island, New York. The two species are commonly found together in this area and for some unknown reason they occasionally fight. A story from the Bahamas told of a swordfish stabbing a mako shark. Concerning swordfish lying torpid in the water: they are commonly found where the water temperature changes rapidly since this is where much food is found. It is possible that these fish become ill and are carried into areas from which they cannot escape, having lost their ability to do so. The reasons for this are as yet unknown. |
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| Q&A 14. | When I was at Bailey’s Island, Maine, someone caught a fish which, when compared to a published picture, appeared to be Luvaris imperialis. Could you provide information about this unusual fish? Louisville, Kentucky |
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| The louvar, Luvaris imperialis, is indeed an uncommon species. Although it inhabits almost all of the oceans, most catches have been made in temperate waters off the Pacific coast of the United States, especially off California. Most of the specimens have been taken in tuna purse seines, but a fair number have been found after they were cast ashore; and some have been found dead or dying at the surface in open waters. This species may reach a length of 6 feet 2 inches and a weight of 305 pounds. Its delicate, white flesh is considered to be delicious eating. Further information about the louvar may be found in Deep-Water Teleostean Fishes of California by Fitch and Lavenberg (University of California Press, Los Angeles and Berkeley, California, 1968). |
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| Q&A 15. | I caught two broadbill swordfish at night and both had a brownish-gray appearance with a light-colored underside. The taxidermist who mounted the fish, however returned them to me with a definite dark-blue upper half I have also seen illustrations of the swordfish with a bronzelike color: What is the true, natural color of this fish? Corpus Christi, Texas |
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| The natural color of the broadbill swordfish is somewhat variable depending upon light conditions and time of day. When a swimming broadbill is observed in bright sunlight from a boat, its back appears to be an iridescent purplish-blue-black as is typical of many large pelagic fishes. The dark-hued back is sometimes separated from the white belly by a bronze stripe. Freshly boated swordfish, however, taken at night with conventional tackle or on longlines are generally bronze colored on the dorsal surface and sides with a silvery whitish belly. With time, the bronze color fades and the purplish pigment on the back becomes more pronounced. Experienced longline captains, who have observed freely swimming swordfish at night, report that these animals are a purplish-blue color. They believe that the bronze color pattern is most likely due to the stress involved in landing them. |
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| Q&A 16. | I have heard that the swordfish is able to keep the temperature of its brain above that of the surrounding water? Can that be possible? Butte, Montana |
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| Yes. Temperatures in the cranial cavities of free-swimming, acoustically tagged swordfish (Xiphias gladius) were 18° to 25°F warmer than the surrounding water, in experiments reported in Science, 216:1327-1329 (June 18, 1982). A brain heater consisting of a mass of specialized tissue associated with one of the eye muscles is most likely responsible, author Francis G. Carey said. Analysis of this tissue indicated an unusually high metabolic rate needed for generating heat. A circulatory countercurrent heat exchanger that supplies this tissue with blood and a layer of insulating fat around the brain and its heater minimize heat loss to other parts 9f the body. The brain heater presumably lessens the effect of the great temperature fluctuations on the central nervous system during the extensive daily vertical migrations by this cold-blooded fish. Similar structures and brain temperature elevations have been recorded from other billfishes as well. |
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| Q&A 17. | Is the "sword" of the swordfish made of bone? Santa Ana, California |
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| Yes. The characteristic swordlike structure of the swordfish (Xiphias gladius) is composed primarily of maxillary and premaxillary bones covered by skin. It is an extension of the upper jaw. In its early larval stages, the swordfish has upper and lower jaws of about equal length, comprising approximately one-fourth of its body length. In this stage, it also has teeth in both jaws. As development progresses, the fish loses all its teeth, and its upper jaw grows more rapidly than the lower one. The result is an elongated, flattened upper jaw that may total one-third of the length of the adult fish. Some researchers believe that the swordfish, sometimes called the broadbill, swiftly slashes its "sword" sideways in order to strike out at the smaller fishes and squids that comprise its prey. |
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| Q&A 18. | I have been involved in the swordfish harpoon fishery for the past five years. The fish are visually located when they fin, that is, when they rest at the surface with their tail and dorsal fin exposed. Why do swordfish fin? Also, why does the number of fish finning vary greatly from year to year? Dana Point, California |
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| During the day, adult swordfish (Xiphias gladius) are found predominantly in deep water, where they are known to feed at depths exceeding 1,000 feet. Their large eyes are a testimony to their life in the dimly lit depths. Swordfish regularly rise to the surface waters to feed at night and return to deep water before dawn. But, the West Coast harpoon fishery relies on the swordfish being at the surface during the day! A small percent of the swordfish population will lie at the surface, or fin, during daylight hours. This phenomenon occurs predominantly in areas where the surface water temperature is between 70°F and 60.5°F, restricting the major part of the California fishery to an area between San Diego and Point Conception during summer. It is believed that swordfish bask in the warmer surface waters to aid digestion. Further south where the deep water is warmer, this behavior is not necessary. Although swordfish are found in deep waters further north, it is not yet known why they do not come to the surface and fin. Possibly, the surface waters are not warm enough to make a substantial difference in digestion, so that time spent finning would be "lost"; that is, the fish cannot feed while finning, and they gain no benefit from an increased digestion rate. Yearly variations in the number of swordfish finning could be due to warmer or cooler surface water temperature in the area usually fished, or could be due to variations in the swordfish population. If the total number of fish has been reduced or if the fish are distributed more toward the cooler or warmer areas within their range, fewer fish will fin. |
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Rosenstiel School of Marine & Atmospheric Science Library
University of Miami, FL USA 4600 Rickenbacker Causeway, Miami, Florida 33149 Phone: 305 421 4060 Fax: 305 421 9306 E-mail: libcirc@rsmas.miami.edu |
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