An introduction to the study of fishes

by Albert C. L. G. Günther

Serranus; Chirus, Ophiodon, Zaniolepis; Sebastes; Nautichthys, Scorpœnichthys, Cottus, Centridermichthys, Hemilepidotus, Artedius, Prionotus, Agonus; Cyclopterus, Liparis; Anarrhichas, Neoclinus, Cebidichthys, Stichœus, Centronotus, Apodichthys; Psychrolutes; Auliscops.

Embiotocidœ.

Gadus. Hippoglossus, Psettichthys, Citharichthys, Paralichthys, Pleuronectes, Parophrys.

Osmerus, Thaleichthys, Hypomesus; Engraulis, Clupea.

Syngnathus.

III.—The Equatorial Zone.

As we approach the Tropic from the north, the tribes characteristic of the Arctic and Temperate zones become scarcer, and disappear altogether: to be replaced by the greater variety of Tropical types. Of Chondropterygians, the Chimœridœ, Spinacidœ, Mustelus, and Raja, do not pass the Tropic, or appear in single species only; and of Teleosteans, the Berycidæ, Pagrus, the Heterolepidina, Cottus and allied genera, Lophius, Anarrhichas, Stichæus, Lepadogaster, Psychrolutes, Centriscus, Notacanthus, the Labridæ and Embiotocidæ, the Lycodidæ, Gadidæ, and marine Salmonidæ disappear either entirely, or retire from the shores and surface into the depths of the ocean.

With regard to variety of forms, as well as to number of individuals, this zone far surpasses either of the temperate zones; in this respect, the life in the sea is as that on the land. Coast fishes are not confined to the actual coast-line, but abound on the coral reefs, with which some parts of the Atlantic and Pacific are studded, and many of which are submerged below the water. The abundance of animal and vegetable life which flourishes on them renders them the favourite pasture-grounds for the endless variety of coral-fishes (Squamipinnes, Acronuridæ, Pomacentridæ, Julidæ, Plectognathi, etc.), and for the larger predatory kinds. The colours and grotesque forms of the Fishes of the Tropics have justly excited the admiration of the earliest observers. Scarlet, black, blue, pink, red, yellow, etc., are arranged in patterns of the most bizarre fashion, mingling in spots, lines, bands; and reminding us of the words of Captain Cook when describing the coral-reefs of Palmerston Island: “The glowing appearance of the Mollusks was still inferior to that of the multitude of fishes that glided gently along, seemingly with the most perfect security. The colours of the different sorts were the most beautiful that can be imagined—the yellow, blue, red, black, etc., far exceeding anything that art can produce. Their various forms, also, contributed to increase the richness of this sub-marine grotto, which could not be surveyed without a pleasing transport.”

Of Chondropterygians the Scylliidæ, Pristis (Saw-fishes), Rhinobatidæ, and Trygonidæ attain to the greatest development. Of Acanthopterygians Centropristis, Serranus, Plectropoma, Mesoprion, Priacanthus, Apogon, Pristipoma, Hæmulon, Diagramma, Gerres, Scolopsis, Synagris, Cæsio, Mullidæ, Lethrinus, Squamipinnes, Cirrhites, some genera of Scorpænidæ, Platycephalus, Sciænidæ, Sphyræna, Caranx Equula, Callionymus, Teuthis, Acanthurus, Naseus, are represented by numerous species; and the majority of these genera and families are limited to this zone. Of Pharyngognaths the Pomacentridæ, Julidina, and Scarina, are met with near every coral formation in a living condition. Of Gadoids, a singular minute form, Bregmaceros, is almost the only representative, the other forms belonging to deep water, and rarely ascending to the surface. Flat-fishes (Pleuronectidæ) are common on sandy coasts, and the majority of the genera are peculiar to the Tropics. Of Physostomi only the Saurina, Clupeidæ, and Murænidæ are represented, the Clupeidæ being exceedingly numerous in individuals, whilst the Murænidæ live more isolated, but show a still greater variety of species. Lophobranchii and Sclerodermi are generally distributed. Branchiostoma has been found on several coasts.

Geographically it is convenient to describe the Coast fauna of the tropical Atlantic separately from that of the Indo-Pacific ocean. The differences between them, however, are far less numerous and important than between the freshwater or terrestrial faunæ of continental regions. The majority of the principal types are found in both, many of the species being even identical; but the species are far more abundant in the Indo-Pacific than in the Atlantic, owing to the greater extent of the archipelagoes in the former. But for the broken and varied character of the coasts of the West Indies, the shores of the tropical Atlantic would, by their general uniformity, afford but a limited variety of conditions to the development of specific and generic forms, whilst the deep inlets of the Indian ocean, with the varying configuration of their coasts, and the different nature of their bottom, its long peninsulas, and its archipelagoes, and the scattered islands of the tropical Pacific, render this part of the globe the most perfect for the development of fish-life. The fishes of the Indian and Pacific oceans (between the Tropics) are almost identical, and the number of species ranging from the Red Sea and east coast of Africa to Polynesia, even to its westernmost islands, is very great indeed. However, this Indo-Pacific fauna does not reach the Pacific coast of South America. The wide space devoid of islands, east of the Sandwich Islands and the Marquesas group, together with the current of cold water which sweeps northwards along the South American coast, has proved to be a very effectual barrier to the eastward extension of the Indo-Pacific fauna of coast fishes; and, consequently, we find an assemblage of fishes on the American coast and at the Galapagoes Islands, sufficiently distinct to constitute a distinct zoological division.