The title of the division Acanthopterygii, or thorny-finned, is founded on the principle that every genus and sub-genus thereof has one or more of the fins supported on, or preceded by, strong, sharp spines, capable of inflicting a severe wound, and forming a very efficient weapon of defense, so that the boldest and most voracious of fishes rarely venture to seize them. All the genera have two dorsal fins—the first, or foremost, of which is invariably supported on spines, as opposed to soft branched rays; while the second, or hindmost, is of soft texture, preceded by one or more hard spines—two pectoral fins, both soft-rayed—one ventral, and one anal, each of which is often preceded by one or more spines—and one caudal, or tail fin, which is the main propelling power of the animal. On the number of the hard spines supplementary to the soft fins, are founded the different families; and on the number of spines in the first dorsal, the dental system, and some other parts of the bony structure, the lesser or individual distinctions. On color, as distinctive of genera, or even varieties, little or no reliance can be placed, unless confirmed by distinct variations in the bony formation; since in all fishes there is observed to exist a great range of hues, shades, and even positive colors, arising sometimes from mere casual influences operating on individual specimens, sometimes from accidents of light or shade affecting peculiar situations, and most frequently of all from the soil and character of the feeding-grounds, and from the various mineral or earthy substances held in solution by the waters they frequent.
These latter influences frequently modify the same fish in different streams, even of the same region and neighborhood, and flowing over soils apparently identical, to such an extent, that the casual observer not unnaturally believes them to be distinct varieties, if not species, and can be with difficulty convinced, on the immutable evidences of structural sameness.
This fact has led, in a great measure, to the complicating and confounding the science of Natural History, by the undue multiplication of names, species, and genera, where no specific differences exist; rendering the science infinitely difficult to the beginner, and causing the unlearned to undervalue the lore of the naturalist, and to deny the reality of all scientific distinctions whatsoever.
On differences of structure, such as the situation and texture of the fins, the number of spines or soft rays in each, the form of the gill covers, the character and position of the teeth, perfect reliance may be placed, as indicating unchangeable specific characteristics, by observation of which the educated naturalist will name at a glance the species, genus and subgenus of any fish, unseen before; and will unerringly determine his habits, his food, and in some degree his habitation.
Thus of the Percoid family we distinguish the subgenera Perca, perch proper, from Gristes and Centrarchus, to which are referred the types black basse of the lakes, and the little rock basse of the St. Lawrence basin, by the fact that the Percæ have one spine to the ventrals and two to the anal. The Gristes one to the ventrals and three to the anal. The Centrarchi one to the ventrals and six to the anal.
And in like manner, by the number of spines supporting the first dorsal, we are enabled to pronounce on the truth or untruthfulness of the many subdivisions of the perch family, as predicated by the fishermen of various regions, and insisted on by credulous naturalists, such as Dr. Smith, of Massachusetts, whose book is rendered absolutely valueless by the readiness which he displays in adopting every local legend concerning new varieties, and classifying new species; until, if we believe him at all, we must believe that every several stream and pool from Maine to Minnesota has its own distinct variety of perch; nor of perch only, but of trout, and, more or less, of every finny tenant of the waters.
The truth appears to have been at length firmly established, and to be this—that there is but one clearly defined and distinct perch, perca flavescens, the yellow perch, found in the United Stales—the perca fluviatilis, common river perch of Europe, does not exist at all in American waters, though it is so closely connected with our fish that a casual observer would pronounce them identical—that the supposed subgenera of perca granulata, or rough-headed perch, perca argentea, silver perch, perca acuta, or sharp-nosed perch, and perca gracilis, said to be peculiar to the small lake of Skaneateles, in the interior of New York, are not sufficiently made out as permanent varieties; and that the variations of color from dark green, and greenish brown, to bright yellow, silvery, and something nearly approaching to orange, are merely local, casual, and individual differences, and not general, permanent, specific distinctions.
The following luminous description of this game and excellent fish is borrowed from Dr. Richardson’s Taura-boreali-Americana, or natural history of the Northern Regions of America, including parts of the United States, and the British Provinces as far north as to the Arctic Ocean. The specimen from which it was compiled was caught at Penetanguishine, on the great Georgian bay of Lake Huron, but will answer for fish of this genus taken in any part of America which they may chance to frequent; so small is their variation in any respect but that of color, which appears to vary in obedience to no fixed law of locality or latitude, except that it appears to me that of the fishes taken in estuaries and at the mouths of tidal rivers, the color is deeper and the tints fade from cerulean black along the dorsal outline to olive green on the flanks, with a silver belly; while in clear lakes and fresh streams, they change from olive-green on the back to bright golden yellow on the sides and belly.
THE YELLOW PERCH.
Color.—General tint of the back greenish-yellow; of the sides golden-yellow with minute black specks; and of the belly whitish. Nine or ten dark bands descend from the back to the sides, and taper away toward the belly; the alternate ones are shorter, and on the tail and shoulders they are less distinctly defined: the longest band is opposite to the posterior part of the first dorsal fin, on which there is a large black mark.