Ditty et. al: Larval development, distribution, and abundance of Coryphaena hippurus and C. equiselis 



28! 



of pompano dolphin were regressing by 11-12 mm. 

 A small spine was present anteriorly along the 

 maxilla of each species by 5 mm (Figs. 1 and 2). The 

 maxillary spine (difficult to locate because of its 

 position and size) pointed dorso-laterally and was 

 slightly better developed in pompano dolphin than 

 in common dolphin of similar size. A posttemporal 

 spine was present in both species by 9 mm and was 

 most easily observed when specimens were viewed 

 dorsally. The anterior portion of the lacrimal bone 

 was prominent in dolphinfish larvae; the lacrimal 

 was more pronounced in pompano than in common 

 dolphin by late flexion (Figs. ID and 2D). 



Minute teeth were present anteriorly on the up- 

 per and lower jaws of each species by 3.8 mm. Num- 

 ber and size of teeth increased with SL. A pair of 

 canine-like teeth were present in 10-mm pompano 

 dolphin and 11-mm common dolphin. 



Spatial and temporal distribution 



Larval dolphinfish were collected during all months 

 sampled, but small larvae of both species were found 

 primarily during warm months. Preflexion larvae of 

 common dolphin occurred mainly from April through 

 November. One common dolphin larva (7.0 mm) was 

 also collected during December (21, 1983), at a sta- 

 tion due south of Caminada Pass, Louisiana (23.5°C, 

 station depth: 531 m). Larval pompano dolphin were 

 collected from March through October; larvae <10 

 mm were collected through late September. Only one 

 pompano dolphin larva (5 mm) was collected during 

 March (13, 1982; water temperature: 18°C), at a 

 bongo-net station 29 m deep off Caminada Pass, 

 Louisiana. Two pompano dolphin larvae (18.3 and 

 22.5 mm) were collected during October (14 and 17, 

 1983), but they were probably spawned during late 

 September. 



Larvae of common dolphin and pompano dolphin 

 were collected primarily at water temperatures 

 >24°C (90% of larvae) and salinities >33 ppt (>75%) 



(Table 2, Fig. 3). The pompano dolphin collected 

 during March was the only larva of either species 

 taken at <21°C. Based on water temperatures when 

 common dolphin larvae usually occurred (>24°C) and 

 using Pauly and Pullin's ( 1988) relationship between 

 egg diameter and water temperature to predict de- 

 velopment time in other marine fishes, we estimate 

 a common dolphin egg of 1.4 mean-mm diameter 

 would hatch in about 38 hours at 25°C and 26 hours 

 at 30°C (Table 3). Few common dolphin larvae and 

 no pompano dolphin were collected at <25 ppt (Table 

 2; Fig. 3). 



Larval dolphinfish of both species were widely 

 distributed in neritic and oceanic waters of the Gulf 

 and most were collected near the surface. Over 90% 

 of common dolphin and about 80% of pompano dol- 

 phin occurred over the outer continental shelf and 

 in oceanic waters; preflexion larvae were usually 

 taken in oceanic waters (stations >180 m deep) (Ap- 

 pendix Fig. 3). Overall, larval common dolphin were 

 significantly more abundant than pompano dolphin 

 (Kruskal-Wallis, P<0.0001, df= 362; Table 4). Lar- 

 val common dolphin were also collected at more sta- 

 tions than were pompano dolphin (15.0% versus 

 5.1%> of all stations sampled, respectively; Table 4). 

 Only 3.1% of oblique bongo-net samples (1982-86, 

 rc=1819) took common dolphin larvae (no. larvae=83, 

 length=6.5 mm, range=3.2-21.8 mm) and <0.01% 

 captured pompano dolphin (no. larvae = 10, x 

 length=4.6 mm, range=4.0-8.7 mm). 



Differences in catch of common dolphin and pom- 

 pano dolphin, respectively, were not significant 

 among seasons or between day and night. About 

 25% of spring and 18% of fall neuston stations col- 

 lected larval common dolphin, but <9% of those sta- 

 tions sampled during summer (Table 4). Larval pom- 

 pano dolphin were collected at 7% of spring neus- 

 ton stations, 2% of summer stations, and 8% of fall 

 stations (Table 4). Only two neuston tows collected 

 >13 larvae of either species; these two tows ac- 



