CLARKE: FECUNDITY AND SPAWNING FREQUENCY OF NEHU 



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HOURS SINCE SPAWNING TIME 



Figure 2.— Maximum oocyte size vs. estimated hours since the 

 most recent spawning time for 460 nehu collected at different times 

 of the day from Kaneohe Bay, HI. Large open circles represent 

 fish that either were spawning or had spawned at or near hours 

 (i.e., the night of or the night before collection) or were unlikely 

 to spawn at 24 h (i.e., the next night). For such fish taken 0-3 h 

 after estimated spawning time, the data points indicate the largest 

 unhydrated oocyte. Triangles represent fish that had not spawned 

 at h or were apparently going to spawn at 24 h. Small solid circles 

 represent fish which were not examined for postovulatory follicles 

 and could not be assigned to the above groups on the basis of oocyte 

 size alone. Solid and dashed lines indicate the mean and ± 1 stan- 

 dard deviation of maximum oocyte size (horizontal lines) for fish 

 represented by circles and triangles, respectively, for three dif- 

 ferent time intervals (vertical lines) considered in Table 2. 



indicated that oocyte size of both spawners and non- 

 spawners had increased considerably over nighttime 

 values. The LMX of the 10 specimens without POF 

 averaged significantly higher than that of the 10 

 with POF (Table 2). The mean LMX for spawners 

 had increased to almost the same value observed for 

 nonspawners in the night samples, while that for 

 nonspawners was almost at the size at which hydra- 

 tion begins. Other fish taken at the same times, but 

 not examined histologically, already carried some 

 hydrated ova (Fig. 2). 

 Data from later in the day indicated that the pre- 



vious night's nonspawning fish do in fact begin 

 hydrating ova and eventually become the spawners 

 of the next night. Hydrated or hydrating ova oc- 

 curred in about half the fish taken inshore between 

 16 and 24 h after last spawning, and most of the 

 rest of the fish had considerably smaller oocjftes 

 (Fig. 2). In 67 of 138 specimens taken inshore more 

 than 20 h after the last spawning time (and thus 4 

 h before the next spawning time), the largest mode 

 was clearly separated from smaller oocytes; LMX 

 was >0.75 mm; and at least some ova were hy- 

 drated. The NMX of 59 fish in this group averaged 

 slightly but significantly (^-test, P > 0.001) smaller 

 than the largest unhydrated oocytes of spawning 

 fish from offshore early night samples (Table 2, line 

 5 vs. line 1). This indicates that during hydration 

 and spawning of the current batch, which require 

 no further increase in dry weight or energy content, 

 the oocytes in the next batch were already starting 

 to advance toward the next spawning. 



Although some of the remaining fish in the late 

 afternoon ( -i- 20 h) samples could conceivably have 

 begun hydrating oocytes and spawned by evening, 

 most appeared to be spawning fish from the night 

 before that were to become the nonspawners of the 

 next night. LMX was >0.70 mm in only 9 of the 71 

 fish in this group, and about 25% of the 45 examined 

 for oocyte size frequency did not have a clearly 

 separated mode. The mean LMX of these 45 fish did 

 not differ significantly {P > 0.05) from that of the 

 nonspawners from the early night samples (Table 

 2, line 6 vs. line 2). The LMX did, however, aver- 

 age significantly (P < 0.005) higher than that of the 

 previous night's spawners in the morning samples 

 (Table 2, line 6 vs. line 3), thus indicating continued 

 oocyte growth between morning and late afternoon. 



In summary, the data indicate that most mature 

 female nehu spawn every other day. The largest 

 oocytes present just after spawning increase sub- 

 stantially in size by the next morning and appear 

 to reach the size found in nonspawning night fish 

 by late afternoon. The largest oocytes in nonspawn- 

 ing fish at night are almost at the point where hydra- 

 tion begins by morning, and appear to begin hy- 

 drating then or shortly afterwards such that the 

 previous night's nonspawners are nearly ready to 

 spawn by late afternoon. 



Alternative cycles are either impossible or diffi- 

 cult to reconcile with the data. If spawning were 

 more frequent, i.e., every day, there would be no 

 nonspawners. This was essentially the case in most 

 night samples taken over the spawning areas, but 

 the day samples averaged about 50% spawners as 

 would result from an every other day cycle. Less 



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