kinds of pituitaries at different intervals 

 of time. The significant point is that 

 these fish were spavraed with pituitary in- 

 jections after they had proved refractory 

 to regular pen treatment. 



On July 5, 1957, a number of unspawned 

 females were obtained from the draw tubes 

 of the power plant at Lake Texoma. Twenty 

 of these were selected for pituitary injec- 

 tions. One female escaped during the exper- 

 iments, but the other 19 were induced to 

 spawn. Three of the 19 spawned only part 

 of their eggs, but the remaining 16 spawned 

 completely. One female spawned after 2 

 injections. All fish were injected with 

 the same dosage, 2 milligra^is per pound of 

 fish weight each 24 hours, but various 

 donor species were used. It appears that 

 these fish were particulcirly receptive to 

 pituitary injections, and therefore spawned 

 readily. 



Two weeks later, July 18, about 40 

 unspawned females were obtained from the 

 same source. Autopsies of a few of these 

 fish revealed that deterioration of the 

 eggs had begun in some fish. The eggs had 

 lost their gloss and some were whitish in 

 color. We selected the most promising of 

 these females and injected them with pitui- 

 taries. A total of 28 was injected, but 

 only 6 spawned successfully (Nos. 14, 15, 

 16, 17, 18, 19; table 2), which suggested 

 that in southern Oklahoma the optimum 

 spawning time had passed by mid-July, 



Degree of Spawning Success 



The degree of spawning success in- 

 creased as the spawning season progressed 

 and new information was gained. We at- 

 tempted to induce spawning in 124 females 

 with pituitary materials. Fifty (40 per- 

 cent) of these females did not spawn. Of 

 these, 10 were abandoned as being in poor 

 reproductive condition, 7 escaped due to 

 improperly constructed aquarium lids, 12 

 died of injuries inflicted by the male, 5 

 died with infections (before the routine 

 use of penicillin was adopted), 2 were over- 

 injected with streptomycin, 2 were autopsied 

 for information on gonadsil condition, 6 

 died unaccountably, and 6 died from handling, 

 bruises, and glass cuts (broken aquaria). 

 It is obvious that the unsuccessful attempts 

 may be categorized as incomplete sexual 

 development in the femeile, infections due 

 to injections and male bites, and human and 



mechanical faults, all of which appear to 

 be correctible in future work. 



BEHAVIOR OF MALES 



Many of the females of the late group 

 were severely bitten by the males, which 

 accounted for several deaths. The males 

 appeared to be more belligerent toward the 

 females than in any previous experiment. 

 One possible explanation of the increased 

 aggressiveness of the males was the physio- 

 logical condition of the females. Most of 

 our observations suggest that when the 

 female is receptive and is easily induced 

 to spawn with pituitary injections the male 

 does not bite her severely. Losses of 

 females due to male bites occurred mostly 

 early in the spawning season (May) and late 

 in the season (late July). Very few died 

 from this cause from June through mid-July. 



Only one experiment with one female 

 was conducted to determine the possible 

 reason for abnormal male aggressiveness. 

 This female was paired with several males, 

 all of which vigorously attacked her. She 

 was then placed by herself and injected 

 with pituitaries. After about 20 hours she 

 was similarly tested with several males, 

 with results as before. She was given a 

 second injection and the next day again 

 paired with several males. The males did 

 not attack her and she was placed with the 

 original male that had been selected for 

 her. Normal spawning occurred after the 

 third injection. These observations have 

 led us to believe that the physiological 

 condition of the female, as related to 

 spawning, in a large measure influences the 

 behavior of the male. Perhaps, in future 

 work, the losses due to male bites can be 

 reduced by injecting the female with one or 

 two doses of pituitaries before pairing her 

 with a male. 



It is not necessary for the male to 

 bite the female to achieve normal spawning. 

 Many of the females that successfully 

 spawned did not show any marks caused by 

 male bites. Some were only slightly marked 

 by the males' teeth. In fact, there ap- 

 peared to be some correlation between ease 

 of spawning and lack of male bites; i.e., 

 the more susceptible the female was to 

 induced spawning the less severe the bites, 

 whereas in the case of unripe females and 

 females delayed beyond the normal spawning 



10 



