626 



Abstract.— We sampled inner shelf 

 habitat in the northeast Gulf of Mexico, 

 for age-0 red snapper. Lutjanus cam- 

 pechanus. to estimate growth rates and 

 seasonality, as well as to identify nurs- 

 ery habitats. We collected 7507 age-0 

 red snapper in 1994 and 1995. from 536 

 10-min trawl tows. Red snapper first 

 settled to benthic habitat in June after 

 reaching 17.4 mm standard length 

 ( age=26 d ). In both years, catch per unit 

 of effort (CPUE=number/10-min tow) 

 peaked July through September, then 

 declined in the fall as fish were leaving 

 the habitat before winter Most fish 

 (SO-Sl^f ) were caught at one location, 

 13 km south of Mobile Bay, Alabama. 

 At this location in 1995, the August 

 CPUE ±SE (712 ±243) far exceeded all 

 previous estimates. Based on otolith 

 microincrements, hatching-date fre- 

 quencies showed distinct cohorts in 

 June and July 1994 and May and June 

 1995. Growth rates for the June (0.77 

 mm/dt and July (0.71 mm/dl cohorts in 

 1994 were significantly faster com- 

 pared with growth rates for May (0.51 

 mm/d ) and June (0.67 mm/d ) cohorts in 

 1995. Density-dependent mechanisms 

 may be operating with faster growth 

 rates and lower CPUEs in 1994, com- 

 pared with slower growth rates and 

 higher CPUEs in 1995. However, envi- 

 ronmental constraints may also be op- 

 erating, as indicated by the slow growth 

 rate of the May 1995 cohort that prob- 

 ably resulted from colder temperatures. 

 Newly settled red snapper were aggre- 

 gated on the inner shelf, at a particu- 

 lar location and time period. These con- 

 centrations indicated an important nurs- 

 ery habitat just south of Mobile Bay, Ala- 

 bama, from July through September. 



Nursery habitats, growth rates, 



and seasonality of age-0 red snapper, 



Lutjanus campechanus, 



in the northeast Gulf of Mexico* 



Stephen T. Szedlmayer 



Joseph Conti 



Marine Fish Laboratory 



Department of Fisheries and Allied Aquacultures 



Auburn University 



8300 State Highway 104 



Fairhope, Alabama 36532 



E-mail address (for S T Szedlmayer) sszedlmaS'acesag auburn edu 



Manuscript accepted 20 August 1998. 

 Fish. Bull. 97:626-635 (1999). 



To enhance survival some fishes 

 spawn many times within a given 

 season (Lambert an<d Ware, 1984). 

 This strategy may produce several 

 distinct cohorts at the juvenile stage 

 within that season (Szedlmayer et 

 al., 1990), and individual cohorts 

 may have an advantage over oth- 

 ers owing to biotic and abiotic envi- 

 ronmental factors (Miranda and 

 Hubbard, 1994). For example, faster 

 growth may increase survival be- 

 cause fish grow past size-specific 

 predators more quickly than slower 

 growing fish (Houde, 1987; Sogard, 

 1997). 



Red snapper, Lutjanus campe- 

 chanus, have an extended spawning 

 season ( Moseley, 1966; Collins et al., 

 1996) and within-year variations in 

 early life stages might be expected, 

 but information on the age-0 juve- 

 nile stage of red snapper is sparse, 

 especially at first settlement. Baugh- 

 man ( 1943 ) suggested that immature 

 fish came close to shore, but this 

 observation was based on only five 

 juvenile red snapper. Ogren and 

 Brusher (1977) indicated inshore 

 nursery areas for age-0 red snapper 

 in the deeper portions of St. Andrew's 

 Bay, Florida, but catch rates were 

 low — a total of 62 fish in 312 10-min 

 trawl tows. Bradley and Bryan 

 (1975) caught young red snapper 

 during summer months and sug- 



gested that juvenile red snapper 

 sought deeper water as they grew 

 older, albeit their catch rates were 

 also low, with a maximum of 10 fish/ 

 10-min tow. Holt and Arnold ( 1982) 

 showed a bimodal size distribution 

 in juvenile red snapper from June 

 through December, but this pattern 

 was derived from separate year 

 classes, where red snapper reached 

 1 10-130 mm during their first year, 

 220-230 mm during their second 

 year. Age-0 red snapper were con- 

 spicuously absent from that study 

 in July, and only 26 age-0 red snap- 

 per were collected in three years of 

 August samples. Szedlmayer and 

 Shipp (1994) reported a catch rate 

 for age-0 red snapper in July 1991 

 that exceeded all previous studies 

 (130 fish/10-min tow), but their ef- 

 fort was low with only 17 trawl tov/s 

 in July, August, and October. 



Despite these previous efforts, no 

 study has specifically targeted age-0 

 red snapper just after settlement. 

 Thus, we suspected that the primary 

 nursery habitats used by first settlers 

 had not been adequately sampled. In 

 the present study we examine the 

 early life stage of red snapper just af- 

 ter settlement. We determine growth 

 rates, distribution, seasonality, and 



Contribution 8996031. Auburn University 

 Alabama Agriculture Experiment Station, 

 Auburn University, Fairhope, AL 36532. 



