Fish-hatching.—In China the hatching of fish is extensively practised. The sale of spawn for this purpose forms an important branch of trade in China. The fisherman collects with care, on the margin and surface of water, all the gelatinous matters that contain spawn of fish, which is then placed in an egg - shell, which has been fresh emptied, through a small hole ; the hole is then stopped, and the shell is placed under a sitting fowl. In a few days the Chinese break the shell n warm water (warmed by the sun), where they are hatched ; the young fish aro then kept in water until they are large enough to be placed in a pond. This plan in some measure counteracts the great destruction of spawn by trawl-nets, which have caused the extinction of many fisheries. Dr. Francis Day, a Madras medical officer, made great efforts to introduce ova of exotic fish into India, and made recommendations for the protection of young fry. A few drops of a weak solution of permanganate of lime, added night and morning, sweetens water, and supplies oxygen, and thus diminishes the mortality in fish-hatching.
Luminous Fishes.—The abdominal surface of sharks is said to be luminous, but due to the presence of small invertebrata ; and shoals of fish are said frequently to emit flashes of light, per ceptible even at great depths. The sand-launce, at night, has a silvery brilliancy, and the cod and other fish after death emit a phosphorescent light. Certain pelagic or deep-sea fishes, as Argyropelecus, Sternoptyx, I chthyococcus, Maur-lens, Gon °stoma, Chauliodus, Stomias, etc., possess luminous organs of a circular form, some being as impressions, others as slight prominences of the skin. In Britain, the pearl - sides (Maurolieus borealis, Farre/i) is one of these fishes.
Weapons.—Sheat fishes or siluroids are generally well armed. They have mostly strong dorsal and pectoral spines, often serrated, with which they can inflict dangerous lacerated wounds. In the marine and estuary forms the armature is invariably spinal. Species of Polyacanthus inflict punctured wounds; and the serrated spines on the tails of the skates cause lacerated wounds. The siluroid Thalasso phryne has a distinct poison gland ; while the Synanc,eia verrucosa has a tube at each of its dorsal spines, and a poison gland at its base. The wounds are very venomous.
Alausa toli, Cuv. and Val., inhabits the sea of Penang, Malayan Peninsula, Singapore, Borneo, Java, Sumatra, Pondicherry, river Cauvery, and Bombay. Total length, 1 foot 9 inches. Like A. ilisha in Bengal, the A. toli is, by the English of the Straits Settlements, denominated shad or sable-fish, and is equally valued for its flavour.
Both are, however, somewhat oily, very rich, and bony. A. toli is remarkable as forming in the Indian Archipelago a distinct and important branch of fishery, principally for the sake of its roe. It is the kind of shad to which Mr. Crawfurd refers as frequenting the great river Siak in Sumatra, and of which the dried roe, of enormous size, constitutes au article of commerce (Craw furd, Hist. Ind. Archipel. p. 440 ; Royle on the Production of Isinglass, p. 76). Mr. Moor, in Notices of the Indian Archipelago, etc., says (p. 29), at Bukit Batu (opposite to and a little to the southward of Malacca), a place on the main of Sumatra within the strait formed by the island of Banka, exists an extensive fishery of the trubu fish. The fi,sh itself is sufficiently known in all the neighbouring seas, but found with a roe only here (that is to say in shoals, for it is plentiful at Penang, Malacca, and Singapore), which makes it certain that it repairs to this favoured place for the purpose of spawning. The trubu, about a cubit long, is taken in 3 and 4 fathoms water on a mud bank. About 300 boats are engaged at all seasons in the fishery, with the exception of four days during dead neap tides. The roes are an article of trade seaways, and the dry fishes are sent into the interior of Sumatra. The raja of Siak draws a revenue from this fishery of 72,000 guilders yearly, receiving a certain duty upon the quantity taken. From the rate and amount of this duty, it is ascertained that the quantity of fish caught yearly amounts t,o between fourteen and fifteen millions. In the Malayan markets the roe iti called Telur ikan, the fish-roe. Like the preparation of fermented fish and shell-fish, Balachan, it is largely used by the Malays and Chinese to season and make their food palatable, and it is no less a favourite relish with Europeans in Sumatra. The fresh roe is thoroughly salted, and next partially dried, so as to retain a slight moisture, in which state it is by hundreds closely placed in casks, and thus exported. In the Malayan settlements the price is from 3 to 4 Spanish dollars per hundred. The dealers there export considerable quantities to China, after having taken the precaution to re-pack the roes between layers of salt, and to sprinkle them with arrack. To dress them, they are soaked for about half an hour in water, and then fried. As the roe appears in commerce, it is of an elongated flat shape, measuring from 6 to 8 inches in length, about 2 in breadth, and of an inch in depth, of a deep amber colour. Tho single eggs aro larger than those of A. ilisha.