MANUAL OF FISH-CULTURE. 189 



water, and must have a very abuudant growth of myrioiihyllum or 

 other water plauts. lu the latitude of Washington, D. C, spawning 

 takes place in April. The fish makes no nest, but deposits its eggs on 

 water-plants, gravel, stones, and other substances. The eggs being 

 adhesive, like those of most cyprinoid fishes, become attached as soon 

 as ejected, and so remain until hatched. The eggs are about iV inch in 

 diameter. They are extremely tender, and it is important that at the 

 time of spawning the water be of an even temperature. 



Under favorable conditions the eggs develop rapidly, and at a mean 

 temperature of 56'=^ F. hatch in 5 or 6 days. In suitable ponds, with 

 plenty of shade and a healthy growth of plants, the natural food that 

 the fry will secure renders artificial feeding unnecessary for a month or 

 more. After the fifth or sixth week the young may be given small 

 quantities of cooked corn-meal mixed with flour. They take finely 

 divided fish flesh, bivalves, and crayfish, but the main dependence 

 should be on the corn-meal flour mixture. 



At the end of six months the young have attained a length of 3 inches, 

 and in a year are 6 inches long. Maturity is attained at an age of 3 

 years. 



THE STURGEONS. 



There are six species of sturgeon in the waters of the United States. 

 The common and the short-nose sturgeons {Acipenser stiirio and ^4.. 

 brevirostris) are found only on the Atlantic Coast, ascending rivers to 

 spawn. The white sturgeon and green sturgeon (A. transmontanus and 

 A. medirostris) inhabit only the waters of the Pacific Coast. The lake 

 sturgeon or rock sturgeon {A.ruhicundus) exists in the Great Lakes, the 

 Upper Mississippi Valley, and other ;iortheru interior waters. The 

 shovel-nose sturgeon or white sturgeon {Scaphirhynchus platyrhynchus) 

 is found in the Mississippi and other streams of the Southern and 

 Western States. 



While all of the sturgeons are edible and caught for market, the 

 most valuable species are the common sturgeon and the lake sturgeon, 

 which alone have been artificially projiagated. 



The catching of sturgeon for market is a business of comparatively 

 recent origin. A few years ago enormous numbers were annually killed 

 and thrown away by salmon, shad, and whitefish fishermen, to whom they 

 were of no value. The special apparatus employed in taking sturgeon 

 consists of gill nets and set lines, but many are caught in pound nets, 

 seines, etc., set primarily for other fish. The principal fisheries are in 

 the Great Lakes, Delaware River, and Sacramento River. The present 

 yearly value of the yield is about $300,000. Very important secondary 

 products are derived from the sturgeon, namely, caviar, isinglass, and oil. 



The sturgeon fishery is declining, and affords a remarkable illustra- 

 tion of the comparative facility with which the supply of river and lake 

 fishes may be exhausted by indiscriminate fishing. In some localities 

 the change in the sturgeon fishery within a single decade has been from 

 a condition of great abundance, with little appreciation of the value of 



