FISHERY BULLETIN: VOL. 73, NO. 4 



temperatures induce gonadal involution in 

 Notemigonus. Pinealectomy under these condi- 

 tions prevents gonadal regression, stimulating 

 gonadal development and spaw^ning. Body lipid 

 reserves were significantly greater in pinealec- 

 tomized fish than in shams maintained on the 

 9L/15D-25°C regime. Under the other pho- 

 toperiod-temperature regimes, pinealectomy 

 resulted in changes in body fat reserves without 

 appreciably altering reproductive activity. Possi- 

 bly then, changes in lipid metabolism due to 

 pinealectomy may influence reproductive activity, 

 but apparently the effects of pinealectomy on fat 

 deposition are not totally dependent on changes in 

 sexual activity. 



Spawning Season 



The effects of pinealectomy on body fat stores 

 were again examined during the early spawning 

 season (late April, Table 3). 



In sham operated fish maintained at 25°C (both 

 photoperiod groups), the lipid index was sig- 

 nificantly lower than that of the initial controls. 

 Body lipid reserves were also significantly deplet- 

 ed in sham operated female fish exposed to the 

 9L/15D-25°C regime, but not in sham operated 



Table 3.-The effects of pinealectomy on body lipid reserves in 

 Notemigonus maintained on various photoperiod-temperature 

 regimes during the early spawning season (21-day treatment). 



'Dry lipid index = mg lipid, less gonadal lipids/g dry body wt. 

 ^Gonosomatic index = wt of gonads (g)/g body wt x 100. 

 •Significantly (P<0.05) different than sham operated controls 

 maintained under same photoperiod-temperature regime. 



females maintained on the 15.5L/8.5D-25°C 

 regime compared to the initial controls. Low 

 temperature treatment during the spawning 

 season caused a significant increase in body lipid 

 content of sham operated female fish regardless of 

 photoperiod. The short photoperiod-low tempera- 

 ture regime stimulated fat deposition in sham 

 operated males; however, body lipid levels did not 

 differ significantly in the initial controls and sham 

 operated males maintained on the long pho- 

 toperiod-low temperature regime. 



At 25°C, body lipid stores were slightly higher in 

 sham operated female fish maintained on a long 

 photoperiod than in females exposed to a short 

 photoperiod; the reverse was true for males. At 

 15°C, sham operated fish maintained on a short 

 photoperiod were significantly fatter than sham 

 operated fish on the long photoperiod regime. 



Lipid reserves were significantly lower in 

 female pinealectomized than in sham operated 

 female fish exposed to the 15.5L/8.5D-25°C 

 regime. In fish (both sexes) maintained on the long 

 photoperiod-low temperature regime, body lipid 

 stores were significantly greater in pinealec- 

 tomized than in sham operated control fish. Body 

 fat content was significantly greater in both sexes 

 of pinealectomized fish than in shams exposed to 

 the 9L/15D-25°C regime. In contrast, lipid content 

 in pinealectomized fish was significantly lower 

 than in sham operated animals on the 9L/15D- 

 15°C regime. 



Body lipid reserves were not significantly 

 different in pinealectomized female fish main- 

 tained on the 9L/15D-15°C regime compared to 

 the females exposed to the 15.5L/8.5D-15°C 

 regime. Fat composition of pinealectomized 

 females exposed to the long photoperiod-low 

 temperature regime did not differ significantly 

 from fat composition in sham operated females 

 which experienced the short photoperiod-low 

 temperature regime. No significant difference 

 was observed in body fatness in pinealectomized 

 females on the 9L/15D-25°C regime and sham 

 operated females on the 15.5L/8.5D-25°C regime. 

 Similarly, body lipid stores were approximately 

 the same in pinealectomized females maintained 

 on the long photoperiod-warm temperature 

 regime and in sham operated females exposed to 

 the short photoperiod-warm temperature regime. 



Many of the fish maintained on the 15.5L/8.D- 

 25°C regime spawned; under these conditions 

 pinealectomy resulted in the initiation of gonadal 

 regression. Compared to sham operated animals 



770 



