tion patterns of slightly larger postlarvae (see table 1 

 in McFarland and Kotchian 1982). Postlarval grunts, 

 however, cannot be identified by sight at the species 

 level. We will refer to these smallest postlarvae as 

 PL-1 grunts. These recently settled postlarvae are 

 diurnal plankton feeders (McFarland 1980) as, 

 presumably, is the preceding pelagic larval stage. 

 Although the postlarvae show strong social tenden- 

 cies to school during daytime, they are solitary at 

 night (Helfman et al. 1982); the same pattern is 

 found in older juveniles and adults (Ogden and 

 Zieman 1977). The typical stereotyped twilight 

 migrations of older juvenile and adult grunts (Hob- 

 son 1968; Ogden and Ehrlich 1977; McFarland et al. 

 1979), however, are not present, nor are the agonis- 

 tic behaviors typical of all later stages (McFarland 

 and Hillis 1982). 



During collateral studies on the population dyna- 

 mics of grunts, on agonistic behavior in juveniles 

 (McFarland and Hillis 1982), and age determinations 

 of grunts (Brothers and McFarland 1981), we noted 

 that recently settled PL-l's appeared in pulses. To in- 

 vestigate this periodicity, an extensive area of bot- 

 tom in Tague Bay and a series of shallower discrete 

 reef sites were censused repeatedly for PL-l's. In 

 addition, subsamples of PL-l's were collected 

 throughout the census period for size and age deter- 

 minations. 



Tague Bay Census Measurements 



Sixteen flagged iron stakes were set 10 m apart 

 along the bottom of Tague Bay parallel to the bay's 

 barrier reef at a depth of ca. 5m. The bottom was 

 characterized by sandhills produced by the burrow- 

 ing activity of thalassinid shrimps, with stands of the 

 seagrasses Thalassia testudinum, Syringodium 

 filiforme, and Halodole wrightii between the 

 mounds. Censuses of the total number of postlarvae 

 were made using scuba, recording the numbers of 

 grunts encountered along a 5 m wide transect. The 

 census included all postlarval grunts observed over 

 an area of 800 m^ of bay bottom. Because almost all 

 juvenile grunts in the immediate vicinity were 

 French grunts, we presume the census data mostly 

 represent this species. Of 85 PL-l's collected on 

 this site, all were identified as French grunts. The 

 census began on 25 February 1979, and was con- 

 tinued at variable intervals through 31 August 1980. 

 Although numbers of older grunts were also record- 

 ed, here we report only the numbers of the smaller 

 and youngest postlarvae (mean SL = 8.5 mm). This 

 census is hereafter referred to as the "sandhill" 

 site. 



FISHERY BULLETIN: VOL. 83, NO. 3 



Reef Census Measurements 



A series of 20 individual sites in a shallow sandy 

 area (1-3 m depth) along a 200 m stretch of the 

 Tague Bay barrier backreef were monitored for post- 

 larval settlement. The sites varied somewhat in size 

 and structure, but were composed of small clumps of 

 Montastrea annularis and/or Porites porites. Six- 

 teen of the sites were in depths of 1 to 2 m; four were 

 in 2 to 3 m depth. Reef areas varied from 0.1 to 8 m^; 

 vertical relief from 20 cm to 1.5 m. Daily censuses 

 were obtained as often as possible from 25 April 

 1980 through 25 May 1981. The census schedule was 

 intensified especially from 6 May through 27 Decem- 

 ber 1980 (172 censuses over 236 d). Counts on each 

 site on each census day included the total numbers of 

 PL-l's, older postlarvae, juvenile grunts (see McFar- 

 land and Kotchian 1982), damselfishes (all species 

 lumped), and the common sea urchin, Diadema an- 

 tillarum, within the spines of which the middle-sized 

 juveniles often seek refuge (see Helfman et al. 1982). 

 In this reef area, which is surrounded by coral sand 

 and lacks seagrass beds, juvenile white grunts were 

 never encountered, only French grunts. We con- 

 clude therefore that recruits were all French 

 grunts. 



Reproductive Activity and 

 Aging of French Grunts 



Spawning in grunts has not been observed or 

 reported in the literature (Breder and Rosen 1966; 

 Hobson 1968; Johannes 1978; Lobel 1978; our per- 

 sonal observations and field observations of P. Colin 

 and of E. S. Hobson). An indirect method was used 

 to provide information on whether grunts spawned 

 in some periodic manner, as so many reef fishes do 

 (Johannes 1978; Lobel 1978; Colin 1982). 



The age of French gnmts can be established in 

 days, for example, by counting the number of micro- 

 structural growth increments laid down in the 

 lapillus (Brothers and McFarland 1981). The method 

 is especially useful for aging the younger life history 

 stages (< 100 d). By ascertaining the actual age of an 

 individual grunt in days, it becomes possible to 

 establish the specific date on which it was spawned. 

 The method requires a correction, however, because 

 the first "daily" growth increment deposited in the 

 otolith does not coincide with fertilization of the egg. 

 Our best "estimate" for the age at formation of the 

 first distinct increment in the otoliths of French 

 grunts is the third day after fertilization (for details 

 see Brothers and McFarland 1981; this revised esti- 

 mate is based on laboratory-reared porkfish, the con- 



414 



