FISHERY BULLETIN: VOL. 69. NO. I 



15n 



LaboratoTLj Bairdiella 1969 





5- 



15r 

 10 





leUSD 14C 



i^F 



I I I I I I I I L_ I I 



J J A 



MONTH 



N 



lOL*^ 16L 



14C 



l\l-.-I' 



-rn 



I I I I 



J L. 



J J A 



MONTH 



N 



Figure 2. — GSI of female Bairdiella icistia captured during the spawning season and maintained under the 

 following laboratory conditions: (a) 16L:8D, 22° C; (b) 16L:8D, 14° C; (c) 10L:14D, 22° C for 2 months; 

 then, photoperiod was increased 15 min/day to 16L:8D; (d) 10L.14D, 14° C for 2 months; then, photope- 

 riod was increased 15 min/day to 16L:8D. Mean GSI of all fish at capture (May 13, 1969) was 12.2 %. Dashed 

 value in (d) indicates GSI of five fish injected with 1 mg of salmon pituitary 1 day prior to last sampling per- 

 iod. Horizontal line at 5 % GSI indicates approximate minimum level necessary for successful hormone-induced 

 spawning. 



studies served as controls when they were sched- 

 uled to be sampled at the same time as the in- 

 jected fish. In all cases the gonad index 

 responded positively to hormone treatment. 

 Differences seen in the tabular data (Tables 3, 

 4, and 5) were due to the number of injections, 

 strength and type of hormone injected, the water 

 temperature and the GSI value of the fish at 

 the beginning of the experiment. 



In Tables 3, 4, and 5 the symbols (S, E, + , — ) 

 record the initial (2 days after the first in- 

 jection) and the maximal (at some point during 

 the series of injections) response noted for each 

 group of fish. Two factors, water temperature 

 and GSI, were found to have an im])ortant bear- 

 ing on the results observed following hormone 

 injection. Fish kept in 14° C water showed the 

 most consistent and largest positive response 

 to long-term hormone injections which were giv- 



Table 3. — GSI of Bairdiella icistia given five injections, 

 every other day for 9 days (17-26-IX-1969). Photope- 

 riod was 16L:8D and temperature 14° C during this e.\- 

 periment. The response of the fish to injection was as- 

 sessed every day and the maximal response is indicated 

 by S (= spawned viable eggs), E (= obtained non- 

 viable eggs), -f (= swollen papillae observed, no eggs 

 obtained), or — (^ no observed response). The sec- 

 ond column under each heading indicates the reproductive 

 status of the fish 2 days after the first injection. The 

 third column (in parentheses) indicates the maximum 

 reaction noted during the experiment. 



166 



