McFARLAM) F.T AI..: RPX'Rl'ITMENT I'ATrKRNS IN FRFCNCH CRUNTS 



Table 2. — Comparisons of fertilization and settlement dates for recently recruited postlarval French) 

 grunts with the lunar cycle and the state of the tides. F and N are full and new moons; S and N are spring 

 and neap tides; It and U are rising and falling tides of intermediate amplitude between a spring and a neap 

 tide. The peak date for settlement represents the maximum influx of postlarvae, which occurred on 

 average 3 d before the maximum number of French grunts appeared on a site. Values are the sums from all 

 20 census sites. Rows are aligned so that the most likely fertilization date precedes each settlement date. 

 Vertical lines and summed numbers for days between peaks are best estimates of weekly peaks to yield 

 the dominant biweekly peaks (see mean values at bottom of table). 



'These two peaks are from sites adjacent to the 20 study sites and were abandoned after April. 

 'The peaks for these dates approximate weekly fertilization and recruitment pulses interspersed be- 

 tween the biweekly peaks for recruitment (see also Fig. 6). 



dividual settlement date and fertilization date to the 

 time of full moon (Fig. 5). Several features stand out: 

 1) The settlement data are less noisy than the fertili- 

 zation data; this is explained, in part, by the more 

 strongly expressed weekly patterns in the fertiliza- 

 tion data. 2) Although settlement is clearly associ- 

 ated with the quarter moons, it does occur during 

 other periods of the lunar cycle as well (see also 

 Table 2, Fig. 2). 3) Fewer PL-l's are present on the 

 sites during full moons than during new moons. 



The relation of settlement pulses to daily tidal ex- 

 cursions (Fig. 6) indicates that settlement was most 



often associated with rising or falling (intermediate) 

 stages of the tidal cycle than with spring or neap 

 tides. A more extensive evaluation of the results 

 reveals that out of 22 identifiable settlement pulses, 

 17 occurred during intermediate tides, 3 with spring 

 highs, and 2 during neap tides. Also, out of 26 fertili- 

 zation periods, 16 occurred during intermediate 

 tides, 7 on spring highs, and 3 during a neap tide. 



If a specific state of the moon, such as the quarter 

 moons, is the significant environmental factor that 

 determines the timing of fertilization and/or settle- 

 ment of French grunts, then the state of the tides 



419 



