FISHERY BULLETIN: VOL. 85, NO. 1 



taken over deep v^ater after sunset indicated that 

 spawning began and ended during a relatively brief 

 period near the predicted spawning time and that 

 most females in the early night samples were 

 spawners. Ten samples were taken within ± 40 min 

 of the predicted spawning time. In four of these, 

 96-100% of the mature females in each (a total of 

 85 examined) carried hydrated ova. Most of those 

 with hydrated ova appeared to have not yet started 

 to spawn, i.e., the hydrated ova were not complete- 

 ly separated from the ovarian tissue and smaller 

 oocytes. In the other six samples, 0-75% of the 

 females (total = 114) carried hydrated ova; most of 

 these appeared to be either partially or nearly com- 

 pletely spent. The largest oocytes in those with no 

 hydrated ova were usually <0.65 mm— about the 

 same size as the largest unhydrated oocytes in those 

 with some hydrated ova present. Only 17 of the 

 specimens without hydrated ova were examined 

 histologically; POF were present in 13. Although it 

 is not possible to separate spawners from non- 

 spawners unequivocally on the basis of oocyte size 

 (see below), the small size of the oocytes and the high 

 fraction with POF among those examined indicate 

 that most of the fish without hydrated ova from 

 these samples had just finished spawning. 



Later in the night, the frequency of females with 

 hydrated ova decreased, and nonspawning fish ap- 

 peared to occur more frequently. In 16 samples 

 taken between 40 min and 2 h after predicted 

 spawning time the percentage of females that 

 carried hydrated ova ranged from to 80%. Most 

 values were <25%, and only 24% of total of 332 ex- 

 amined carried hydrated ova. Most of those with 

 hydrated ova appeared at least partially spent; many 



carried only a few at the posterior end of the ovi- 

 ducts. In 14 of these samples, most of the females 

 without hydrated ova were probably recent 

 spawners. The largest oocytes present were <0.65 

 mm long, and POF were present in 19 of 20 fish ex- 

 amined histologically. In two other samples, how- 

 ever, several of the females carried larger unhy- 

 drated oocytes; POF were present in only 6 of 10 

 examined from one of these samples. Among the 20 

 samples taken later in the night (2-4 h after pre- 

 dicted spawning time), only 5 of 254 mature females 

 carried hydrated ova, and oocytes >0.65 mm were 

 present in many of the others. POF were present 

 in only 10 of 20 females examined from two of these 

 samples. 



Spawning Frequency and 

 Oocyte Development Rate 



Oocyte size-frequency data for 135 fish taken be- 

 tween and 3.25 h after spawning time indicated 

 that spawners carried smaller oocytes than non- 

 spawners. Few of these fish had clearly defined 

 modes of unhydrated oocytes, so LMX (or NMX if 

 hydrated ova were present) was used as a measure 

 of oocyte development. The 20 specimens without 

 POF carried significantly larger oocytes than those 

 with either POF or some hydrated ova present 

 (Table 2). Although there was some overlap in the 

 size ranges of the two groups (Fig. 2), most of the 

 other fish taken during this period but not examined 

 histologically had relatively small oocytes and were 

 probably recent spawners. 



Oocyte size-frequency data from fish taken inshore 

 in the morning, 14-16 h after last spawning time. 



Table 2.— Means and ranges of largest oocyte in the most advanced (first) or next mode of 

 oocytes for nefiu taken over spawning areas at night and in shallow areas during the morning 

 and afternoon. For night fish which had tome hydrated ova present, the datum used was 

 the largest unhydrated oocyte. Collection times were adjusted to hours since estimated time 

 of the most recent spawning. For night and morning, "S" indicates fish that spawned the 

 night of or the night before collection; for afternoon, "S" indicates fish about to spawn the 

 next night. Similarly, "NS" indicates fish that had not spawned the night of or before collec- 

 tion or were not about to spawn the next night. Probability values between three pairs are 

 based on f -tests. 



P < 0,001 



P < 0.001 



P< 0.001 



132 



