fin, but sometimes it was injected through 

 the abdomen or into the muscles of the back. 

 We preferred the area just behind the pelvic 

 fin (fig. 4). The muscles of this region 

 closed the needle wound and prevented the 

 loss of materials more effectively than did 

 other areas, and early experience indicated 

 that inflammatory ulcers were less likely 

 to occur with intraperitoneal injections. 



Frequency, Number, and 

 Size of Injection 



To determine the relation between 

 frequency, size, and number of injections 

 required to induce spawning in channel cat- 

 fish, 20 females that were considered equal 

 in gonadal development were selected and 



divided into 5 groups . ;:■ 



2/ 



The test fish 



were injected with carp pituitaries at one 

 of the following dosages: Group I, 8 milli- 

 grams per pound of body weight each 96 hours 

 (8 mg/lb/96 hrs); Group II, 6 mg/lb/72 hrs; 

 Group III, 4 mg/lb/48 hrs; Group IV, 2 mg/ 

 lb/24 hrs; and Group V, 1 mg/lb/12 hrs 

 (table 1). If these dosages are prorated 

 on a 24-hour basis, it is obvious that each 

 female in the experiment received 2 milli- 

 grams per pound of weight each 24 hours, 

 even though the dosage and interval of in- 

 jection was different in the 5 groups. 



The death of 4 fish from various 

 injuries (male bites, handling) and 5 

 instances of altered frequencies due to 

 experimental errors limit evaluation of the 

 data, but these conclusions may be drawn: 

 (1) Fish in every dosage category spawned; 

 therefore, the frequency and size of the 

 dosage were probably not critical within 

 the limits of this experiment. (2) The 

 total amount of pituitary materials used to 

 induce spawning in a fish varied from 3 mil- 

 ligrams to 32 milligrams per pound of body 

 weight. (3) With the exception of 1 fish, 

 which spawned with 1 injection of 4 milli- 

 grams per pound of body weight, the fish 

 that received the greatest number of injec- 

 tions (5) at the lowest dosage (1 mg/lb) 

 spawned with the least amount of pituitary 

 material. These data suggest that the gona- 



2J Contiol groups were usually not set up at tliis period in our 

 investigations, since many previous, controlled experi- 

 ments had indicated that the environmental requirenaents 

 of tile channel catfish are so strict that tiiey will not spawn 

 in small aquaiia without pituitary injections. We have 

 never had uninjected fish spawn in aquaria. 



Figure 4. — Female is held in a. plastic screen net while 

 pituitary injections with penicillin-G is being 

 administered by glass hypodermic syringe and 

 a No. 20 needle into the body cavity near the 

 base of the pelvic fin. 



dotropic level necessary to produce spawning 

 was maintained more effectively by low dos- 

 ages frequently injected than by higher 

 dosages less frequently given. The fish in 

 other categories had received at least 6 

 milligrams per pound by the time these fish 

 had received 5 milligrams, and only 3 had 

 spawned. Low doses frequently injected may 

 save pituitary materials, but the saving is 

 not very signif iccUit . On the other hand, 

 high doses require less frequent injections 

 and may be more convenient for the f ish- 

 culturist. 



SUCCESS OF SPAWNING FOLLOWING 

 INJECTIONS 



During the 1957 season (May through 

 July), 40 percent of the females that 

 spawned had received 6 roilligreuns or less 

 of pituitaries per pound of body weight, 

 and 80 percent had received 12 milligrams 

 or less. To some extent these figures 

 reflect the procedure used, since most of 

 the fish were given 2 milligrams of pitui- 

 tary per pound of body weight in each in- 

 jection, and most fish responded positively 

 after 3 injections (tajjle 2). 



Twenty females were selected for 

 hormone spawning from adults collected from 

 the Red River below Lake Texoma.' Thirteen 

 females were injected with carp pituitaries 

 (Nos. 1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 

 13, 20; table 2), 2 with flathead pituitar- 

 ies (Nos. 44, 45), 2 with channel catfish 



