14 



Fishery Bulletin 101(1) 



10 ~ 



I 6 



en 

 £ 4 



Larvae from station 41 

 L = exp(-0.052 + 0.1 68t) 

 = 0.95, n= 



Larvae from station 42 

 L = exp(0.147 + 0.1 24t; 

 r^= 0.91, n= 23 



n r 



7 9 



Age (days) 



11 



13 



Figure 3 



Age versus length data for Atlantic bumper larvae (/! = 140) collected at nine 

 stations in the northcentral Gulf of Mexico during 14-16 September 1991. High- 

 lighted are the age-length relationships at two adjacent stations where growth 

 rates differed. L = notochord or standard length in mm; t = larval age in days. 



A 



0.151 

 0.13 

 11 

 009 

 0.07 1 

 05 



11 



15 16 



T 1 r 



24 25 30 31 



B 





11 



15 



16 



24 

 Station 



25 



30 



31 



Figure 4 



(irowth coofTicients (horizontal bars) for vermilion snapper 

 larvae collected at seven stations in the northcentral Gulf of 

 Mexico during 14-16 September 1991. Vortical lines represent 

 9.')7( confidence intervals around the growth coefficients, and 

 numbers above bars depict sample sizes. (Al shows age versus 

 In length growth coefficients, and iBl shows age versus In dry- 

 weight growth coefficients. 



Differences in age versus dry-weight growth coefficients 

 were also significantly different (ANCOVA; P=0.03) and 

 once again stations 15 and 25 (Fig. 4B) were significantly 

 different (STP). Vermilion snapper larvae gained weight 

 faster at station 15 where an 11.0-d-old larva had an esti- 

 mated dry weight of 0.28 mg. At station 25 the estimated 

 dry weight of this same larva was only 0.17 mg. Although 

 vermilion snapper larvae were collected at most of the sta- 

 tions within the study area (Fig. 1), abundances were low 

 at shallow (12-14 m depth) stations immediately south 

 of the Mississippi-Alabama coast, and larvae were never 

 collected at stations within Chandeleur Sound. These sta- 

 tions were very shallow (4-9 m). 



Although our study did not assess microzooplankton 

 prey availability, macrozooplankton dry-weight estimates 

 varied widely over space and time. At the 33 stations east of 

 Chandeleur Sound where larvae of vermilion snapper and 

 Atlantic bumper used in our study were captured, macro- 

 zooplankton dry-weight estimates at 20 stations exceeded 

 3g/100 m'*, and at eight of those stations values exceeded 

 5g/100 m'^. Seven days later only at five of the 33 stations 

 were macrozooplankton dry-weight estimates >3g/100 m' 

 and at no station did estimates exceed 5g/100 m-^. 



Mortality estimates 



Atlantic bumper was generally the most abundant spe- 

 cies in plankton collections; 32,241 larvae were collected 

 during six cruises conducted in September of 1990, 1991, 

 and 1993. Mortality rates were not estimated for Atlantic 

 bumper larvae collected during the two cruises conducted 

 in September 1992 because abundances of larvae were 

 very low. When station abundance data were pooled for 

 each of the six cruises, size-frequency distributions gener- 



