MiFAKLANI) KT AI, : KKCKl'ITMKNT I'AITKRNS IN FRKNCH CRrNTS 



DAYS BEFORE AND AFTER FULL MOON 



5 14 10 5 5 10 15 



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 3 

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MOON PHASE 



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P'iGiiRE 6. - Relation between the periodic settlement pulses of postlarval grunts during 1980, the phases of the moon, and the procession of 

 spring and neap tides. Shaded areas represent relatively uniform series of neap or spring tides; unshaded areas are either increasing or 

 decreasing intermediate tides (see Table 2). The sequence of days reads from left to right across each row. The first day of each calendar 



month is indicated by the letters, e.g., A at top = April 1980 J = January 1981. Closed circles represent the large and intermediate-sized 



pulses (> 100 PL-l's); open circles are settlement pulses with < 100 individuals (see Table 2). Closed and open circles with the letter w are 

 weekly recruitment pulses interspersed between the more common biweekly peaks (see Table 2). The two abruptly changing vertical lines in- 

 dicate the actual dates of the quarter moons at different times of the year, as determined from the Nautical Almanac for 1980. The mean 

 deviations of those pulses most closely associated in each month with the quarter moons are: first quarter moon = 1.7 d + 1.9 (SD). third 

 (juarter moon = 0.9 d + 0.8 (SD). Maximum tidal excursions for spring tides occurred in May and June, and in October and November, as did 

 the maximum recruitment of PL-l's to the census sites (Fig. 2, Table 2). 



of the settlement pulses and fertilizations were 

 associated with quarter moons and intermediate 

 tides (Table 2), attempts were made to isolate the 

 significant categories by combining the data (springs 

 -I- neaps versus intermediate tides; full + new moons 

 versus quarter moons). Nonsignificance occurred in 

 all combinations with the exception of tides and 

 settlement (g-test = 9.91 > x^,.:,,,, = 3.84). 



The relationship between fertilization and settle- 

 ment of French grunts and the state of the tides and 

 lunar cycle is obviously complex and difficult to 

 unravel without ambiguity. Larger sample sizes 

 (data over several years) would help, but perhaps 

 more important would be specific data on current 

 regimes at actual spawning sites and in the general 

 vicinity of settlement sites. The highly significant but 

 independent effects of moon and tidal state likely 

 point at the importance of favorable currents to 

 successful larval recruitment. 



Settlement of Postlarvae in Space and Time 



From May through December 1980, when the cen- 

 sus frequency was high, there were 16 consecutive 

 quarter-moon periods. On the 20 census sites, there- 

 fore, a total of 320 separate pulses (16 x 20) could 

 have been observed if settlement did occur during 

 the quarter moons. During this period 161 pulses 

 were actually observed on the 20 sites during 

 quarter moons. When the number of PL-l's settling 

 was high, most sites recruited fish (90% for May- 

 June, 75% for October-November). In winter, when 

 the number of fish settling was low, recruitment 

 nevertheless occurred on at least 4 or more sites dur- 

 ing the quarter moons. 



The periodic appearance of PL-l's on 11 of the 20 

 sites was virtually continuous at each quarter moon, 

 and similar in general pattern to that depicted by the 

 pooled data (e.g., site 11, Fig. 2). On 4 sites, 



421 



