FISHERY BULLETIN: VOL. 69, NO. I 



interpreted as additional evidence tiiat a two- 

 hormone system exists for reproductive control 

 in fishes similar to the FSH-LH system of birds 

 and mammals (see Ahsan and Hoar, 1963; Hy- 

 der, 1970, for details). HCG is LH-like while 

 PMS is FSH-like; fish pituitary extracts show 

 strong LH and slight FSH activity in mammals,, 

 but there is a great deal of conflicting evidence 

 and interpretation (Sundararaj and Goswami, 

 1966; Hoar, 1969). Other evidence indicates 

 that PMS acts like a combination of FSH and 

 LH when tested in mammals (Ball, 1960), but 

 this effect can be modified by the dosage used. 

 Hoar (1969) pi-esently considers it likely that 

 teleost pituitaries contain only a single gona- 

 dotropin. 



Sundararaj and Goswami (1966) demonstrate 

 how wide the range of conflicting results can be, 

 when they report that hypophysectomized cat- 

 fish, HeteropnenMes fossilis, spawned ripe eggs 

 after injection with appropriate concentrations 

 of LH, HCG, PMS, and DOCA, while FSH 

 brought about ripening but no spawning (LH 

 contamination was possible) . PMS did cause 

 ovulation in striped bass (Stevens, 1966) . HCG 

 has been used successfully in other fish spawn- 

 ing studies (e.g., Sneed and Clemens, 19.59; 

 Stevens, 1966). The fact that both PMS and 

 HCG can lead to successful spawning and, yet, 

 reflect basically antagonistic systems in mam- 

 mals should make these hormones prime targets 

 in future experiments. 



It is quite evident that considerable work re- 

 mains to be done to untangle the connections be- 

 tween hydration and ovulation, which are cer- 

 tainly i-elated events, but may be controlled by 

 different hormones acting at different threshold 

 levels. 



The puzzling fact that one out of four .50 lU 

 HCG fish hydrated and spawned while three out 

 of three 100 I U fish hydrated Ijut never spawned, 

 might be explained by postulating that a "criti- 

 cal dose" exists, with doses above or below this 

 level being unable to induce the complete se- 

 quence of spawning events. The three 50 lU 

 fish which did not hydrate would perhaps have 

 spawned if their GSI had been above 5 Sf . A 

 "critical dose" phenomenon might also be in- 



volved in the observed difference in hydration 

 and the comjilete lack of spawning obtained with 

 5 mg and 10 mg carp pituitary, as both groups 

 showed GSI values above 5 % ; in this case the 

 "critical dose" might lie between 5 mg and 10 

 mg. 



Carp is considered a universal donor by Cle- 

 mens and Sneed (1962) and was successfully 

 used to spawn several species of freshwater 

 fishes. Bioassay with goldfish showed 100 lU 

 HCG to be equivalent to 0.5 mg acetone-di'ied 

 carp pituitary (Sneed and Clemens, 1959), and 

 ovulation was obtained with 100-1600 lU HCG 

 and 0.5-3.0 mg carp. Most other workers also 

 report no inhibition of spawning from very 

 large doses, but they all point out the critical 

 nature of exceeding some lower threshold dose 

 to initiate ovulation. The strength of pituitary 

 extracts for spawning is assumed to be related 

 to the reproductive status of the donors, a datum 

 not given by the company selling the carp pitui- 

 taries used in the present experiments. Salmon 

 pituitaries, however, were removed only from 

 fish graded at the hatchery for optimal ripeness 

 and the glands were taken within 15 min of 

 death. Nonetheless, from the results of this 

 study 1 mg of salmon pituitary appears to be 

 5 to 10 times more potent than 1 mg carp and 

 about equal to 50 lU HCG or PMS, although 

 definite qualitative differences in response exist. 

 A truly valid comparison of the strength of var- 

 ious fish pituitary preparations can of course be 

 made only by standardized bioassay (for reviews 

 of methods see Clemens and Sneed, 1962; Das 

 and Kahn, 1962; and Yamazaki and Donaldson, 

 1968a and 1968b). 



It is clear that the effects of hormones vary 

 with the GSI level of the experimental fish. Most 

 of these spawning experiments were carried out 

 over a 2-month period beginning in mid-Ajn-il 

 and ending in mid-.June, while the GSI was 

 gradually decreasing in the stock of fish used for 

 the experiments. Thus, it is difficult to directly 

 compare the effects of 50 lU and 100 lU HCG, 

 as they were tested almost 2 months apart and 

 the average GSI values of the experimental fish 

 may have been somewhat different. The effect 

 of the population's declining GSI is clear in the 



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