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Fishery Bulletin 92(2). 1994 



to posterior direction. Pelvic fins 

 were precocious and heavily pig- 

 mented. Pelvic buds were visible 

 by 4.0 mm; pelvics had a full 

 complement of elements (I, 5) by 

 6.0 mm. Pectoral rays began to 

 develop by 5.0 mm and a full 

 complement (17) was present by 

 8.0 mm. Sequence of fin comple- 

 tion was pelvics - soft dorsal and 

 anal rays - dorsal spines - pecto- 

 rals. A full complement of elements 

 in all fins by 8.0-8.5 mm marked 

 the beginning of transition to the 

 juvenile stage (Table 2). 



Temporal and spatial 

 distribution 



Alantic spadefish larvae were col- 

 lected from May through Septem- 

 ber primarily in the north-central 

 Gulf. Larvae were usually col- 

 lected between June and August, 

 density being highest during June 

 and catch highest during August 

 (Table 3). Larval Atlantic spade- 

 fish were especially abundant 

 near the Mississippi River delta 

 during August 1988, when 19 of 

 72 neuston tows (26%) associated 

 with riverine frontal zones col- 

 lected larvae. During August 

 1984, however, <5% of neuston 

 tows (rc = 162) from other areas of 

 the north-central and western 

 Gulf not associated with the delta 

 captured larvae. Only one Atlan- 

 tic spadefish larva was collected 

 east of Mobile Bay, Alabama (long. 

 88°00' W). This 4.0-mm specimen 

 was found off Apalachicola Bay 

 (Florida) during August 1984 at a 

 station 13 m deep (Fig. 4). Salin- 

 ity at this station (34.2 ppt) was the highest re- 

 corded with a positive catch during the study. The 

 largest specimen collected in surface-towed nets was 

 12.5 mm; this observation may indicate that larvae 

 move out of surface waters by this size. 



Overall, >85% of Atlantic spadefish larvae were 

 collected in surface waters >28.0°C (median: 28.TC, 

 mean: 28.7°C, range: 25.0°-32.2 <, C), at salinities be- 

 tween 26.7 and 31.3 ppt (median: 28.8 ppt, mean: 

 28.4 ppt, range: 11.8-34.2 ppt), and at station depths 

 <238 m (median: 83 m, mean: 139 m, range: 9-470 m) 



Table 3 



Density (number of larvae/100 m 3 ) and catch (number of larvae/10 neus- 

 ton tows) of Atlantic spadefish larvae (Chaetodipterus faber) from the 

 northern Gulf of Mexico. Months are combined across years (1982-1986, 

 and August 1988). Not all months were sampled each year. Numbers 

 in parentheses are positive catch stations over total stations sampled 

 by month. Monthly density estimates were calculated by dividing sum 

 of larvae by either sum of volume water filtered (VWF) overall, or sum 

 of positive station VWF. Monthly catch estimates were calculated by di- 

 viding sum of larvae by number of stations sampled overall or by num- 

 ber of positive catch stations. 



' Total VWF - 43,730 m 3 , positive catch station VWF - 1,799 m 3 , number of larvae col- 

 lected was 111. 



2 0.02/100 m 3 . 



3 Total VWF - 22,207 m 3 , positive catch station VWF - 381 m 3 , number of larvae collected 

 was 5. 



4 0.03/100 m 3 . 



5 Total VWF - 35,174 m 3 , positive catch station VWF - 796 m 3 . number of larvae collected 

 was 12. 



(Fig. 5). However, distribution of larvae versus sta- 

 tion depth was strongly influenced by two very large 

 neuston-net collections of 192 and 64 larvae during 

 August 1985 which represented 40% of all larval 

 Atlantic spadefish taken. These two stations were 

 located in waters near the shelf edge, 50 and 75 km 

 east of the Mississippi River delta (28.1°C, 30.1 ppt, 

 235 m deep; 27.9°C, 28.1 ppt, 238 m deep, respec- 

 tively). Other stations had 27 or fewer larvae. Dis- 

 tribution of larvae versus station depth without the 

 two large collections shifted median station depth 



