CHAPTER XIII.
FINNY LIGHT-BEARERS--(SURFACE FORMS).
On calm nights the splash of the oars and the fall of spray from the bow of the boat startle many fishes resting at or near the surface, which dart away like comets, leaving a blaze of light behind, and giving the impression that they are light-givers or phosphorescent. This does not always follow; as, while many possessors of luminous spots undoubtedly approach the surface at night, as _Scopelus_ (Plate X., Fig. 1), many owe their brilliant appearance to the luminosity of the medium in which they swim; in other words, the vigorous motion of their fins produces the same effect and result that is attained by darting the hand through water bearing phosphorescent animals. If such a display is produced by one fish, we may well imagine that a school moving rapidly would create a light of considerable intensity.
Drifting over a school of menhaden, and peering down among them, each fish seems outlined in a golden halo; while coruscations of light appear to flash from the fishes as they move along, the presence of the school being indicated upon the water by a pale luminous spot.
In more active fishes, as the mackerel, the display is still more brilliant, often presenting a blaze of light upon the surface, visible from the masthead of a vessel for a long distance, and often resulting in the capture of an entire school; as the mackerel-men, aware of the light produced by the fish, keep a lookout in the foretop; and upon its discovery, the great net is passed around it, the fishes becoming victims to the light they inadvertently produce. When the mackerel are tossed into the boat, they roll over in a golden mass in their struggles, hurling a cloud of spray into the air over boat, net, and men. In handling these fishes, phosphorescent matter will sometimes come off upon the hands, and the gleaming fluid is seen running from the bodies; so, possibly, in some instances, the fishes possess a luminous secretion, as in the case of the shark of Dr. Bennett.
The sunfish (Plate XVIII., Fig. 3), an extremely common form on our eastern shores, appears to have a wide geographical range. In American waters, it is known as the sunfish, presumably from its oval shape. Two fins only are present, these being opposite one another, the tail represented by a mere ridge. The sunfish attains a height, from the tip of one fin to that of the other, of seven feet, and sometimes more, weighing several hundred pounds.[44]
Some years ago, while at the little fishing-village of Mayport, at the mouth of the St. John’s River, Florida, one of these huge fishes ran aground on the bar, actually drawing too much water to cross. Its struggles attracted so much attention, that a boat was sent out, and the monster captured. I sent a photograph of the fish north, and the latter was afterwards purchased by the New-York Aquarium. It was the largest specimen of this fish I ever saw on exhibition.
So sluggish are they, that, at Ogunquit, Me., the fishermen frequently ran alongside of them as they rolled about at the surface, and, thrusting a boat-hook into the small mouth, hauled them aboard; or, if too heavy, lashed them to the side, in which position they were towed ashore, where the liver, the only valuable portion, was secured; though the muscular tissue was sometimes appropriated by the boys of the neighborhood, who found it a good substitute for India-rubber as an interior for base-balls.
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In a large specimen which I examined, the skin was covered with a remarkable mucilaginous envelope, in which were numerous parasites; while in the mouth was a large goose-barnacle, which was situated just far enough in to escape being crushed by the formidable teeth. If asked to select a fish showing evidences of possible phosphorescence, I should name the sunfish, as the curious envelope of mucus seems particularly adapted as the seat of this remarkable phenomenon; but I have not only never observed its luminosity, but have been unable to obtain a direct statement from any one in this country as to its light-emitting quality. I give it a place among the luminous fishes, on the authority of T. Spencer Cobbold, M.D., F.L.S., who says, in referring to it, “It is nearly circular in form; and the silvery whiteness of the sides, together with their brilliant phosphorescence during the night, has obtained for it, very generally, the appellation of sun or moon fish.”
Karl Semper, in his “Animal Life,” says: “The fishermen of Nice assert that the moonfish (_Orthagoriscus mola_) is luminous;” but as no scientist, that I am aware of, makes a definite statement of personally observing its light, we will leave the moon or sun fish among the forms which are possibly phosphorescent, yet not proven so.
Statements are often made regarding the phosphorescence of whales and other cetaceans; but the wondrous displays which they undoubtedly produce as they rise, perhaps to escape the ferocious attacks of the killer, are due only to the myriads of small light-givers,--_medusæ_, _salpæ_, crustaceans, and others,--which when disturbed become luminous.
Among the well-known phosphorescent fishes, the _Scopelus_, found in the greater depths, rises at times, at night, to the surface. _Scopelus humboldtii_ (Plate X., Fig. 1), has a double row of luminous spots on each side of the abdomen. One of the spots, enlarged in reflected light, is shown in the same plate.
The phosphorescence of _Myctophum crenulare_, an ally of _Scopelus_, has been observed; and, at least on the Pacific coast, this little fish probably rises to the surface, a specimen an inch and a half in length having been taken from the stomach of an albicore (_Orcynus alalonga_) in the Santa Barbara Channel. In this specimen a phosphorescent spot was seen on each mandible near the symphysis, thirty-three along the abdomen, six in front of the ventral fins, six more between the latter and the origin of the anal, and twenty-one between the front of the anal fin and the base of the tail; quite enough, if all are luminous, to outline the little creature in lines of vivid brightness.
The long, arrow-like gars are peculiarly surface forms, it being evidently only with extreme difficulty that they leave the surface. Allied to them is _Hemiramphus_, in which the lower jaw only is elongated; and, according to Günther, this interesting fish has a gleaming phosphorescent pustule at the tip of its tail, a circumstance that makes it one, not only of the most unique of the surface forms, but of all the finny light-bearers. Many other forms known to possess luminous spots undoubtedly visit the surface at night, just as many large predatory fishes then come well in shore. Indeed, the night is the feeding-time of the southern fishes; at least, the season when they are upon their travels.
At Tortugas, on the Florida reef, the shoal to the west of the key was deserted during the day, except by schools of mullet, small barracuda, and a few others; but at night the sandy shoal seemed fairly alive with large fishes. Man-eaters, ten or fourteen feet long, ranged up and down, readily taking the hook; and nearly all the large fishes, which by day lived upon the outer reef or in the channel, could be taken here; while loud splashes and vivid displays of phosphorescence told that the large rays, indeed the great manta itself, ventured in shore in nocturnal rambles.