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.
* * * * *
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.