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Olla's fish were captured off Palm Beach in March 1964, anesthetized and flown to Sandy Hook. When they revived, the lights had been arranged to simulate Florida daylight. Originally there were 10 fish, each about a pound and a half, but two of them succumbed to a fungus infection. The remaining eight have been healthy and have gained a pound each. Shortly after the fish arrived, Olla and several assistants began a round-the-clock observation program. The scientists were curious to see if the fish, like many birds and mammals, had an internal rhythm or pattern of activity related to light. He found that bluefish are never really at rest—a fact that may account for their scrappiness. Olla was able to measure their rate of activity by noting the time it took the fish to swim between two broad lines marked in the tank. When the blues were active they covered the 12-foot course in as little as nine and a half seconds; when they were "resting" they took up to 16 seconds to swim the distance. Olla and his team found that bluefish are diurnal, that is, they are most active during daylight hours. The daily pattern of activity is almost always the same. The blues are slow-moving at night, but shortly before dawn there is an increase in swimming speed, which reaches a peak between the hours of 11 a.m. and 2 p.m. After that the rate starts to slow, though there is sometimes a sudden rise at twilight. Olla's findings are of such significance (they might even have relevance to the workings of man's biological clock in outer space) that he delivered a paper on the subject before the American Association for the Advancement of Science.
Olla has found that bluefish have keen eyesight in good light. "We're positive that these bluefish can see a bait or lure in the air before it hits the water," Olla says. "We've thrown baitfish to the other end of the tank, and the blues follow them at tremendous speeds and grab them as they hit."
Olla notes that when blues feed they flash their two pelvic fins, usually held tight against their sides. "I'm not sure, but it might be a signaling device to the rest of the school to keep them all in a state of excitement," he says. "If fish on an edge of the school come across food, their flashing fins would let the others know where the food is. But this is just conjecture."
The eight blues at Sandy Hook normally travel in a school. The school disperses when the fish are feeding and, after having fed, it regroups again. When frightened, the fish dive for the bottom and go into a pod, a very compact school in which their bodies press against one another. Frightened blues in a pod swim actively and refuse to feed. Blues can be frightened by unusual sounds or disturbances in the water. A blue's heart normally beats about 60 to 70 times a minute but, unlike mammals, its heart slows when it is frightened. By testing heart deceleration with a sensitive electrocardiograph, Olla was able to note the blues' responses to sounds, and he found that they can hear sounds ranging from less than 100 to 3,100 cycles per second. This range is nowhere near as extensive as man's, but in practical terms it means that, while they are not able to hear voices above water, they can detect the slap of an oar or the plop of an anchor. Moreover, blues also can detect water movements through their lateral lines, a sort of sixth sense that fish possess. The lateral lines are a row of receptors along each side. "If you started kicking in the water," Olla says, "a bluefish 50 feet away might not hear it, but he would get the message through the lateral line."
There is no external way of determining the sex of bluefish, but Olla thinks it likely that he has both males and females. The fish are so acclimated that he is cautiously hopeful they may attempt to spawn this year. So little is known of bluefish spawning that biologists have even been hard put to identify bluefish eggs and larvae. In an attempt to remedy this, John R. Clark and David G. Deuel succeeded in July 1964 in artificially fertilizing bluefish eggs with sperm taken from ripe fish. Bluefish eggs had been artificially fertilized on two previous occasions, most recently by a Russian biologist, but the drawings showing eggs and larvae were not adequate for identifying samples taken at sea. At Sandy Hook the eggs took 46 to 48 hours to hatch in beakers of seawater, and Clark and Deuel succeeded in keeping one larval blue alive for a record seven days. At regular intervals specimens of eggs and larvae were preserved, and drawings made of them will be of great value in identifying spawn at sea. A bluefish egg is quite small, about the size of this letter o. At the University of Connecticut marine lab Dr. William A. Lund Jr. also has been working on the early life history of bluefish. Lund is of the opinion that bluefish spawn close to shore in his area, and Clark feels this is also true along the Jersey coast, where there apparently are two spawning periods, one in May, the other in July. "It is vital for us to know the eggs and larvae and their whereabouts and the forces at work," Clark says. "We would like to know about possible mortality from polluted water or warm water. If there are discrete stocks, subject to different conditions in different places, we want to know about them. Spawning may be affected by a cold spring. There may be predators at work in July. It is an accepted thing in fishery management that you're going toward some practical goal. Perhaps some day all the wetlands will be destroyed and the spawning and nursery grounds gone. Some day we may need hatcheries for marine fish."
The migrations of bluefish up and down the coast also are being studied at Sandy Hook. The biologists are trying to find out why bluefish frequent certain waters. Last summer, for instance, bluefish, from two inches to six pounds, swarmed up the Hudson River as far as Peekskill, N.Y., almost 50 miles from the harbor mouth. Snapper blues were seined out of brackish water at Croton with pumpkinseed sunfish. What is it that attracts them? Are they just roaming, or are they following the baitfish up the river? Where do they go from the river, Long Island Sound or the Jersey coast?
To find out about the comings and goings of bluefish, Clark began tagging them in 1962. Deuel has continued the work. So far they have tagged 14,000, and the lab has received 850 returns. At first Clark used rod and reel and, although this was fun, it was too slow. Deuel now catches blues in a strong monofilament net, and he can tag about 30 in an hour. To his surprise, he has taken about 60% of the netted fish close to the bottom. Larger blues, those five pounds or over, are, for some reason, rarely caught in the net. Lund, up in Connecticut, has had the same experience. Lund has gone after the larger blues by trolling handlines, and he has caught them up to 15 pounds. He catches the big ones in The Race, a celebrated fishing ground near the mouth of Long Island Sound.
Lionel A. Walford, director of the Sandy Hook lab, theorizes that the blues found off Delaware Bay in May probably belong to a population that stays in the northeast the year round and does not migrate to Florida as previously thought. "There may be one population, if not two, that remains in northern waters the year round," Walford says. Deep-sea trawls have taken bluefish over the Hudson gorge in midwinter, and a biologist in North Carolina has informed Walford that swordfish caught 50 miles offshore in February had bluefish in their stomachs. "According to temperature charts, there is a band of 50� to 55� water extending along the edge of most of the continental shelf from southern New England down. A small population of cold-tolerant blues could winter in this band. Another population, probably the principal one that summers off the New Jersey and New York coasts, seems to be associated with 59� to 64� water. This temperature range extends all winter long in a narrow band from just south of Cape Hatteras to northern Florida. We think that many blues can be found in this band during winter. The opinion of the scientists at Sandy Hook is that although bluefish wintering in Florida are feeding and maturing sexually, their principal spawning occurs as they journey northward. The northward migration is not triggered by temperature alone, because the fish leave before the water temperature changes. After spawning, the eggs drift and the parent fish continue north, eventually joining the northern stock. The offspring summer in estuarine areas of North Carolina. That winter they go out on the shelf and return again to North Carolina the following summer. By the second winter they are ready to go to Florida.
"There are several local populations on the coast. One of these is primarily northern and cold-tolerant, and there is another warm-water stock which summers in Chesapeake and North Carolina waters and then travels to southern Florida and perhaps northern Cuba. Judging from tag returns, a member of this warm-water population will sally forth into New Jersey or Long Island waters," Walford says. Bluefish are not as numerous along the Gulf Coast as they are on the East Coast, and the populations do not mix very much. For some reason that biologists have not been able to fathom, the fish in the Gulf of Mexico tend to stay on one side or the other of the Mississippi River. Walford does not rule out the possibility, however slim, that some of the blues on the East Coast, particularly the bigger fish which prefer the off-shore areas, migrate across the Atlantic to the Azores or North Africa. "This is a possibility we must test," he says. "I think enough of this possibility to have our tags printed in French and Spanish as well as English."
Last year was a poor one for blues off Jersey but, according to forecasts filed with the Atlantic States Marine Fisheries Commission by state biologists, the waters from Montauk to Cape Cod should again teem with blues. Walford hopes that any anglers who catch tagged fish or note any unusual occurrences will report their findings to the laboratory. Information of this nature will help disclose the life history of the blue. Walford says, "It's as though we were looking at a very fuzzy picture that is starting to come into focus."