continued for the fiill 6 hours that the fish were 

 observed to spawn, the female would lay about 

 150 eggs each time, in order to lay 8,000 eggs. 

 The rate and number, of course, may vary 

 with the size of tlie female, her readiness to 

 spawn, and the sexual vigor of either male or 

 female. Generally, females which weighed 

 from 1 to 4 pounds produced about 4, 000 eggs 

 per pound of body weight. Fish of larger size 

 usually spawned about 3, 000 per pound of body 

 weight. 



EFFECTS OF DISTURBANCES ON Sl'AWNING 



One might suppose that the females in 

 our experiments were rendered somewhat in- 

 sensitive to external stimuli because of the 

 intense internal or hormonal stimuli created by 

 the introduction of the pituitaries. However, 

 this reasoning would not apply to the males 

 which were not injected with hormones, unless 

 the males were secondarily affected and stimu- 

 lated to a high degree of sexual awareness by 

 the injected females by reason of her actions or 

 because of secreted hormones. 



The following observations suggest, at 

 least, that when the female is under the influ- 

 ence of exogenous gonadotropins, disturbance 

 does not interfere with the successful comple- 

 tion of the spawning act: 



1 . The aquariums in which spawning occur- 

 red were placed on tables in an area where 

 workers and visitors frequently passed. 



2 . A pair of catfish began spawning at 8:50 

 p.m. after they had been moved several times 

 the previous day to try out various pairing com- 

 binations with other fish. 



3 . Two pairs spawned under bright lights 

 which were being used in connection with a 



n wie camera . 



4 . The male of a spawning pair being 

 photographed under bright llg^t ate the first 

 eggs deposited. However, after he was fed 

 liver, the pair successfully spawned, but the 

 photography was discontinued. Since other 

 pairs spawned under bright lights, hunger rather 

 than excitement was probably the cause of the 

 egg eating. 



5. Moving either a spawning male or female 

 to another aquarium with other fish and then 

 back to their resident aquarium and mate failed 

 to delay spiawnlng in any Instance . 



STAGES OF CEVELOPMENT AND PERIOD 

 OF INCUBATION 



We are in accord with the sequence of 

 embryonic development as given by Murphree 

 (1940), see table 2. The actual day when the 

 respective developmental stages occur vary ac- 

 cording to the temperature . Inasmuch as channel 

 catfish spawn between 70° and 85° F., with the 

 optimum temperature around 80° F., the period 

 of Incubation within this temperature range is 

 from 5 to 10 days (Toole 1951). We witnessed 

 hatching in 5 days; but at mean temperatures of 

 about 80° F., the time from the first deposition 

 of eggs to the time when the first egg hatched 

 ranged from 6 to 7 days. One lot of eggs (re- 

 ferred to as "a spawn") began hatching in 5 days 

 and 19 hours, and all eggs were hatched 6-1/2 

 hours later. Eye spots may be observed by 

 close examination late on the third day at tem- 

 peratures of 82° F., but may be inconspicuous 

 up to 5 days at temperatures of 79° F. These 

 results concur with reports in the literature, 

 see table 3. 



Eggs that were laid first were the last 

 to hatch . A gradient of oxygen tension between 

 the top and bottom eggs probably accounted for 

 the difference in hatching time. Minute differ- 

 ences in temperature between the top and bottom 

 appeared rather unlikely especially in the aquar- 

 ium experiments. 



CARE OF EGGS 



It is a well-established fact that the male 

 channel catfish cares for the eggs after the 

 spawning is finished. However, we observed 

 that the female cared for the eggs from the stand- 

 point of aeration during the period of spawning; 

 at least her activities at the time might serve 

 that purpose. The paddling of the male when he 

 lay next to the female did accomplish some aera- 

 tion, but the male did not assume the responsi- 

 bility until spawning was over . At the end of the 

 spawning period the male for the first time began 

 paddling on the top of the eggs, while the female 

 rested quietly to one side. In one Instance, after 



