FRESH-WATER FISHES 

 CHAPTER 8 



The fishes rival the birds and the mammals in popular appeal and com' 

 prise one of the three major groups of the animal kingdom generally affected 

 by the game laws. The sale of fishing equipment each year is enormous, and 

 sporting books and magazines devote countless pages to discussions of the 

 paraphernalia and technique of the angler. The familiar game fishes, however, 

 make up only a small proportion of American fresh-water fishes. The recent 

 popularity of home and public aquaria has created a fancy for other interest' 

 ing or beautiful species. Although the popular tropicals come from Central 

 and South America, several of the forms commonly sold in pet shops are native 

 to the southern states. It is a surprise to many people to learn that there are 

 also many attractive and interesting small fishes in northern ponds and rivers. 



Not true fishes but related to them are the lampreys, frequently called 

 lampreyeels. As a matter of fact the eel is a true fish which, by the loss of 

 some structures, has come to resemble the lamprey slightly. The latter can 

 be distinguished from eels and all other fishes by a row of gill openings on 

 each side, its lack of paired fins and its jawless, and usually round, mouth. 

 From this round mouth is derived the scientific name of the group to which it 

 belongs, the Cydostomes. All lampreys start their lives in fresh water, hatch' 

 ing from eggs their parents have deposited and covered with sand or gravel in 

 nests in the river or lake bed. Lampreys have a larval stage, called the am- 

 mocoete, corresponding somev.'hat to the tadpole stage of the frog. The ex' 

 ternal differences between larvae and adults are not very marked, but the dif' 

 ferences in internal anatomy are great. The chief external difference lies in 

 the mouth region, the larva having a pair of lips overhung by a hood as wide 

 as the body. In the adult the hood is gone and so are the lips, only a circular 

 depression, which becomes armed with epidermal ''teeth", remaining. Few 

 people besides the fishermen who gather them for bait ever see the larval lam' 

 preys, for they live concealed in burrov^s in the sand or gravel and feed on 

 minute organisms which the water brings to them. Two or more years are 

 passed in this secluded existence before the animals transform into adults. It 

 is known that some species are unable to feed as adults, living on material 

 stored in their tissues until they reproduce. Others prey on fish and may live 

 for several years as adults before reproducing. With the disc'like structure 

 around the mouth acting as a suction cup, the parasitic lamprey attaches itself 

 to a fish, rasps a hole in the body wall by means of its epidermal teeth, and 



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