PLANTS AND OTHER CONSIDERATIONS 57 



is available in the tank or unless the adults are kept in 

 nets which permit the young fish to escape. Zebra fish 

 and goldfish will lay eggs but frequently eat the eggs 

 immediately after they are laid. To avoid this prob- 

 lem, gravel may be used in zebra tanks. The eggs fall 

 into the interstices of the gravel and are protected. 

 Goldfish may be permitted to spawn on mats of dried 

 Spanish moss or grass roots, and immediately after 

 spawning is complete the mats are moved to another 

 tank. 



FIGHTING BETWEEN SEXES: Fighting IS often 

 associated with reproduction. In some cases a change 

 in size relationship between the sexes will reduce this 

 problem. At times permitting the female to reach a 

 more advanced state of development before placing 

 the male with it will correct the problem. Mr. Shell of 

 Alabama Polytechnical Institute in breeding Tilapia 

 uses small females and large males. They are placed in 

 a trough with a divider which permits the smaller fe- 

 males to pass but not the males. The female thus as- 

 sociates with the male at will (SheU unpublished). 



stripping: Stripping is a routine procedure in 

 the culture of trout and salmon and is practical for 

 some other, but not all, fishes. It has the advantage of 

 giving exact information as to the time of fertilization 

 and age of embryo. Crosses can sometimes be made 

 by this method between forms which otherwise will 

 not mate. Using the stripping technique, fishes which 

 often eat their own eggs may be used for experimen- 

 tation. (Strawn, Kirk, and Hubbs 1956). 



Ripe males and females are used for stripping. The 

 process involves gently pressing the mature eggs from 



