56 MAINTAINING FISHES 



series of injections of ground fish pituitary or A.P.L. 

 is used. Spawning by "ripe" fishes can usually be 

 triggered by one injection or in some cases simply by 

 moving the fish to fresh water. 



Fish pituitary is prepared by obtaining pituitaries 

 from large fishes (carp has been widely used) from 

 the wild, preferably in the spring just prior to spawn- 

 ing time. The excised pituitaries are dehydrated in 

 acetone, dried and stored in tightly sealed contain- 

 ers. They will remain active for one or two years. For 

 use the dried glands are ground, suspended in sterile 

 water and injected in the coelom. If inflammation be- 

 comes a problem, penicilHn g may be mixed with the 

 pituitary suspensions. Two problems are associated 

 with the use of fish pituitary. It is not generally avail- 

 able and must be obtained from the wild, and the 

 dosage is difficult to calculate inasmuch as the level 

 of activity of the material is usually not known. About 

 the only approach to determining the dose for indi- 

 vidual conditions is by trial and error. 



Recently Sneed and Clemens (1959) reported 

 chorionic gonadotrophin to be satisfactory for trigger- 

 ing spawning in a number of fishes. For the channel 

 catfish they recommend 8OO1U per pound of fish. 



The use of pituitary is greatly simplified if ripe fish 

 are taken from the wild or from outside pools and the 

 pituitary reUed upon solely to trigger spawning. For 

 an excellent review of the use of pituitary in spawning 

 fishes the reader is referred to Atz and Pickford 

 (1959). 



EATING OF EGGS AND FRY: SomC fish SUCh aS 



the swordtails and platies will reproduce readily but 

 are inclined to eat their young unless vegetative cover 



