FISHERY BULLETIN: VOL. 70, NO. 4 



later stage of vitellogenesis. The ovaries of all 

 fish in the September nature sample were in the 

 quiescent phase (Stage II), 



After 57 days at 27°C, testicular weights were 

 significantly lower (P < 0.05) than those of the 

 initial July controls. The testes of all fish were 

 in the quiescent phase (Stage 1), even after 134 

 days. In contrast, the testes of all fish in the 

 November sample from nature were in Stage 3. 



Ovarian weights of fish exposed to 27°C (both 

 the September and November samples) did not 

 differ significantly from those of the initial July 

 controls, but they were significantly lower 

 (P < 0.01) than ovarian weights of both 13°C 

 groups. The ovaries of the 27°C treated fish 

 revealed only resting oocytes (Stage II). How- 

 ever, the ovaries of fish in the November sample 

 from nature were in Stage III, IV, or V. 



Thus, low temperatures promote gonadal re- 

 crudescence in Gillichthys, independent of photo- 

 period. Short photoperiods may accelerate the 

 rate of gonadal recrudescence at low tempera- 

 tures. A short photoperiod, however, failed to 



initiate gonadal recrudescence at high temper- 

 ature. High temperatures act by blocking vitel- 

 logenesis and the transformation of spermatogo- 

 nia to spermatocytes. 



The influence of constant temperature and 

 photoperiod on testicular recrudence was exam- 

 ined again in July 1968, using 13° or 20°C, with 

 a short (8L/16D) and a long (15L/9D) photo- 

 period. A fifth group was exposed to 24°C at a 

 long photoperiod (15L/9D). Each group was 

 sampled after 45, 70, and 120 days (Figures 2 

 and 3). 



In the initial July controls testes were regres- 

 sing (Stage 0). At 24°C testicular weights re- 

 mained low throughout the experiment; in Sep- 

 tember and November testicular weights at this 

 temperature were significantly lower (P < 0.05) 

 than those of the initial July controls. More- 

 over, at 24 °C testes remained in the regression 

 or quiescent phase (Stage or 1) throughout the 

 experiment (Figure 3). 



At 20°C testicular weights remained essen- 

 tially the same as in the initial July controls 



90 



80 



70 



'60 



.50 



40- 



•5 30- 



20 



10- 



Iniliol 

 Controls 

 (15 July) 



I5L 8L I5L 8L I5L 

 24° 



20° 



13° 



28 August 



15L 8L I5L SL I5L 

 24° 20° 13° 



V 



22 September 



th 



* 



I5L 8L I5L 8L I5L 

 24° 20° 13° , 



I November 



Figure 2.— EflFect of 24°, 20°, and 13°C treatments at short (8L/16D) and 

 long (15L/9D) photoperiods on testicular weight in Gillichthys mirabilis. 

 Mean testicular weight is represented by histograms; the mean is bracketed 

 by one standard error. Shaded histograms represent testicular weight of 

 samples collected in nature; open histograms, experimental groups. Light 

 (hours given per 24 hr), temperature, and dates on which fish were sacrificed 

 are recorded below the histograms. For sample sizes, see Figure 3. 



1140 



