Off the shore of Hatteras Island, where the inner edge of the Gulf Stream flows northward over the outer continental shelf, the marine life is unlike that of any other area in the Atlantic. Here the powerful ocean river helps foster an extraordinarily rich diversity of life, including Sargassum mats concealing strange creatures and exotic sea beans, whales and sea turtles, sunfish and flying fish, and shearwaters and Bermuda petrels. During his long career as a research scientist, David S. Lee made more than 300 visits to this area off the North Carolina coast, documenting its extraordinary biodiversity. In this collection of twenty linked essays, Lee draws on his personal observations and knowledge of the North Atlantic marine environment to introduce us to the natural wonders of an offshore treasure.
In the following excerpt from Gulf Stream Chronicles: A Naturalist Explores Life in an Ocean River (pp. 37-41), Lee examines the life, anatomy, and flight patterns of the Hirundichthys affinis, a four-winged flying fish found in the Gulf Stream.
I looked up in time to see a flying fish sailing past at eye level, 15 feet above the water. Turning to Captain Harry Baum, I asked whether any had ever landed in this boat. While he was telling me that in 26 years of fishing in the Gulf Stream, that had never happened, an 11-inch-long flying fish crash-landed on the deck below. I rushed down, secured my prize, and hurried back to the bridge to ask Captain Baum if his boat had ever been struck by lightning. What I thought was the best one-liner of the day was not appreciated. The captain proceeded to recount the times his boat had been struck, how insurance companies refused to insure electrical navigational equipment, and how, when . . . well, you get the idea.
During the warm months, flying fish are commonly seen in the Gulf Stream off North Carolina. So at times when there is not much going on aboard ship, and when other creatures of the open sea are scarce, I watch fish fly. It’s sort of a mindless pastime, but always interesting. The movement of the boat, or perhaps the sound of the engine, seems to make them take flight. Usually they take to the air when we are 10 or 20 yards away. Occasionally whole schools of 50 or more launch themselves simultaneously, but normally there is simply one here or two here and there. In the course of an hour it is not uncommon to see several hundred take flight. Sometimes I try to estimate flight distance or duration, the sole scorekeeper in the outer continental shelf fish Olympics. Watching flying fish I was reminded of the lines from Kipling’s poem “Mandalay”: “Where the flyin’-fishes play, / An’ the dawn comes up like thunder . . . ,” wishing I could recall more of the verses and wondering about the real order of the ones I remember.
After my earliest excursions to the Gulf Stream, I combed libraries for information on flying fish. Information was scattered, mostly repetitive trivia, but in combination, an interesting dossier was pieced together. Much of the literature contained only summaries of the family Exocoetidae in general, keys to species occurring in various oceans and things like that. Of the 25 species known to live in U.S. waters, 17 occur in the Atlantic, including 2 species shared with the Pacific. As best I could figure, about 15 of these species have been found off North Carolina, but these numbers include flying-fish relatives like ballyhoos, halfbeaks, and flying halfbeaks—fishes that think flight simply involves jumping out of the water. Still, there are at least 12 species of flying fish that I might be seeing in the Gulf Stream. I could recognize five, perhaps six, different types, but really I had no way of knowing what species I was seeing. This predicament was somewhat alleviated by the fact that flying fish come in two basic models, two winged and four winged. The four-winged types have large pectoral and pelvic fins and look a lot like little biplanes.
Steve Ross, a friend who specializes in marine fishes, identified the specimen that crashed onto the deck of Captain Baum’s charter boat as Hirundichthys affinis, one of the four-winged fishes flying about. Was this the species I was regularly seeing, or were there several types of large, silvery, blunt-nosed, four-winged fishes in the area? The solution was to get more specimens. I had read that people in the Caribbean capture flying fish at night by placing a lantern next to a sail. The fish fly into the light, hitting the sail and flopping into the boat. I considered variations on this theme and then went out and purchased several boxes of No. 9 shotgun shells for my 12-gauge. It took almost one box of shells for me to see that I constantly shot well behind the fish, often missing them by several yards. Gad, sometimes I wasn’t even that close. There was no speculating about the miss; the shot pattern clearly sprayed the water. My failed attempts provided the captain with great amusement and he delighted in announcing my score over the radio to the rest of the charter-fishing fleet. The fish flew faster than I thought and it took a number of shells from a second box before I learned how to lead them. Altogether I hit six or eight fish using two boxes of shells. We retrieved four specimens, the others sank. All were the same large, silver-colored, four-winged flying fish.
I have seen other types that are quite distinctive in coloration, but to date I have been unable to collect or identify them. Except for Hirundichthys, most of these seem to live in Sargassum. One is an inch-long species with tan, blotched wings that has a maximum flight distance of several yards as it scoots from one Sargassum patch to another. A second, biplane type, with velvet black wings, also lives in the Sargassum. It grows to six or eight inches, but also seems limited to short flights. I have not seen flying fish of any type in the winter months. Their seasonality suggests that they are migratory and are not simply being passively transported by the Gulf Stream.
Though flying fish are scattered widely throughout the warm oceans of the world, and I knew there were a number of local species I could watch, I really only had one identified. I limited my note taking to Hirundichthys affinis. I estimated the longest flights to be between 100 and 125 yards and they lasted for 10–20 seconds. (One Pacific species has been reported to fly a quarter of a mile.) Usually the fish flew less than a few feet or so above the surface, but in strong winds they were sometimes lifted 6 to 10 feet into the air. Based on the forward trolling speed of the charter boats, I estimated flight speeds to be about 35 mph, partly explaining my difficulty in collecting specimens with a shotgun. (Researchers with high-tech equipment have since documented top speeds of up to 40 mph.) The fish would typically fly out at angles of 20° or so from their presumed predator or charter boats, but if we got too close, the direction of flight would often shift to near 45°. In flight, the fish angle upward, so on takeoff and landing the tail always touches the water last and first. With their sculling tail movement they sometimes made two or three composite flights in succession, at times ricocheting from the top of a wave and continuing their flight. Successive flights tended to be shorter in time and distance—the fish simply ran out of gas. Unlike the two-winged species, four-winged flying fishes exhibit a controlled flight even in strong winds. While the two-winged varieties waffle about erratically in the air, I observed that Hirundichthys flew straight, or even banked and changed direction. On calm days, the ripples of their lopsided, lobed tail fins left trails on the surface runways.
The specimens I collected ranged in size from 10–12 inches long and weighed 97 to 258 grams. Pectoral fin lengths ranged from 5 to 6 inches, making the total wingspan somewhat greater than the length of the fish. By tracing out the wings on a piece of paper and calculating the area, I ascertained that the wing-loading ratio (combined surface area of both pectoral and pelvic fins divided by the weight of the fish) was about the same as that of a Cessna. When the dimensional relationships of various species of flying fishes are compared to each other, and to flying insects, birds, and bats, the ratios of weight-to-wing area and wing length all show logarithmic coordinates producing a line whose slope is three. OK, that’s enough math.
These fish were spawning off the Carolina coast in August. Dissecting the specimens showed that about half of the females had recently laid eggs and the others soon would. While not a shocking piece of biological information, documentation of such tidbits eventually adds up to understanding the biology of poorly understood species such as flying fish. I was impressed with the large swim bladders of my specimens. The same device that provided buoyancy for surface-scooting oceanic fish allowed the ones I collected to float long enough for me to scoop them from the sea.
For years, the mechanism by which flying fish were able to fly was the focus of much debate. Did they flap their enlarged pectoral fins as birds and insects flap their wings? Careful observation and high-speed photographic images eventually showed that flying fish Continue reading ‘Excerpt: Gulf Stream Chronicles, by David S. Lee’ »