714 



Fishery Bulletin 90(4). 1992 



Figure 2 



Photomicrograph (400 x ) of the transverse-sectioned 

 sagittal otolith of a 23.5 mm SL juvenile Atlantic 

 bumper Chlorosrombrus chrysui~us observed under 

 ultraviolet light. The lower light band displays the up- 

 take of calcein during the immersion process. 



equivalent to the number of days the fish was held in 

 captivity. The slope (1.02) of a least-squares linear 

 regression (Fig. 3) was not significantly different from 

 1.0 (i-test, p>0.05), confirming daily increment forma- 

 tion in otoliths of larval and juvenile Atlantic bumper. 



Larval Atlantic bumper have circular sagitta, with 

 a central core. Yolksac larvae (O.SmmSL, preserved 

 length) lacked increments. However, all other aged fish 

 between 1.0 and 5.0 mm (preserved length; N 158) had 

 countable increments (i.e., 1-11 increments or 3-13 

 days old; Fig. 4). Growth models were based only on 

 2-13 day-old fish. 



Larval Atlantic bumper growth rates during the first 

 two weeks of life were best described using a linear 

 model. A separate growth curve was estimated for the 

 5-7 August 1986 data (Table 1). Growth curve com- 



Y = 0.25 + 1.02X, R =0.99 

 N = 9 



01 23456789 10 11 



Number of Increments 



Figure 3 



Regression of the number of otolith growth increments subse- 

 quent to the fluorescent calcein mark on the number of days 

 each fish was held in captivity before sacrificing. Numbers 

 associated with points represent overlapping values. 



^ 1986 (N = 90) 

 [ZD 1987 (N = 70) 



^ 



^ 



-S^ K^ 



10 11 12 13 



Age (days) 



Figure 4 



Age distribution of Atlantic bumper Chloroscombrus chfysurux 

 larvae captured off the Louisiana-Mississippi barrier islands. 

 1986-87. 



parisons for the two cruises in September 1986 (days 

 8-9 and 22-24) showed no significant differences 

 within month (intercept, p 0.44; slope, p 0.48). Similar- 

 ly, no significant difference was found between the two 

 September cruises in 1987 (days 8-10 and 24-26; in- 

 tercept, p 0.07; slope, p 0.42). Therefore, the paired 

 September data sets were combined into a single 

 regression for each year (1986 and 1987; Table 1). 

 Atlantic bumper length-frequencies displayed no sig- 

 nificant differences (p 0.93) between the two different 

 mesh sizes (202 vs. 333^m) during the 1987 daytime 



