Ditty and Shaw: Larval development and distribution of Lobotes surinamensis 



39 



cleared-and-stained 10.2-mm specimen had three 

 supraneurals, six branchiostegal rays, four upper 

 and four lower procurrent caudal rays, 11+13 ver- 

 tebrae, 27 dorsal rays (XII, 15), and 14-15 anal rays 

 (III, 11-12). Scales first appeared at 9.0-9.5 mm and 

 marked the beginning of transition to the juvenile 

 stage. 



Spatial and temporal distribution 



Overall, 75% of tripletail larvae in this study (Ap- 

 pendix Table 2) occurred at surface water tempera- 

 tures >28.8°C (median=28.9°C, range=27.6-31.0°C), 

 at salinities >30.3 ppt (median = 31.3 ppt, 

 range=22. 0-36.0 ppt), and at stations >70 m deep 

 (median=205 m, range=l-2707 m) (Figs. 3 and 4). 

 Larvae <5.0 mm were collected only at stations >110 

 m deep. The two smallest larvae (2.2 and 2.4 mm) 

 were taken on 28 July 1987 in a Tucker trawl 



sample at a station 110 m deep off Southwest Pass 

 of the Mississippi River (Appendix Table 2). Other 

 life stages were collected throughout the study area 

 (Fig. 5, Appendix Table 2). 



Tripletail larvae were taken almost exclusively 

 from July through September. Two specimens were 

 collected in neuston nets outside this time period, 

 one taken on 21 May 1983 (7.0 mm) and the other 

 by GCRL on 9 October 1968 (10.2 mm) (Appendix 

 Table 2). Salinity (36.5 ppt) and station depth (2,707 

 m) for the May specimen were the maximums re- 

 corded for a station where larvae were collected 

 during this study (Appendix Table 2). 



Larval tripletail were collected primarily near the 

 surface. Only 2 of 528 oblique bongo-net collections 

 between July and September yielded tripletail lar- 

 vae («=6, 6.0-9.0 mm, 18 September 1985). Of 537 

 total surface net tows taken during this same time 

 period, only 31 tows (5.8%) collected tripletail lar- 



67% 



N = 77 



28 29 30 31 

 TEMPERATURE (C) 



22 26 27 28 29 30 31 32 33 34 35 36 

 SALINITY (PPT) 



<5 5-50 51-180 >180 



DEPTH (M) 



Figure 3 



Summary of hydrographic data from positive catch stations for larval tripletail (Lobotes surinamensis) in 

 the northern Gulf of Mexico. Percent catch is sum of larvae by interval divided by total number of tripletail 

 larvae collected overall. Discrepancies in n (number of larvae), among parameters, are the result of missing 

 hydrographic data. Depth is station depth. 



