NOTES 



OBSERVATIONS ON TWO SPECIES OF 



DOLPHIN (Coryphaena) FROM THE 



TROPICAL MID-ATLANTIC 



Large numbers of adult do\\-A\m, Coryphaena 

 hippnnis Linnaeus, aggregated at night around 

 the U.S. Coast and Geodetic Survey Ship Dis- 

 coverer as it drifted in the tropical mid-Atlantic 

 Ocean in February 1969 (see Stoner, 1969). 

 Only juveniles of Coryphaena equlselis Linnae- 

 us, however, were caught under the night light. 

 This note presents additional details of colora- 

 tion and meristic counts of juvenile C. equiselis 

 and reports on mid-oceanic concentrations of 

 adult C. hippurus. 



The drift track of the RV Discoverer on the 

 Atlantic Trade Wind Expedition (ATEX)— lat 

 13M8' N long 39°03' W to lat 09°55' N long 44° 

 3.5' W, February 5 to 22, 1969 — is shown in Fig- 

 ure 1 (see also PotthofF, 1969). The surface 

 temperature of the water during the drift pe- 

 riod ranged from 25.3° C to 26.8° C and the 

 water depth from 1,757 fm to 2,753 fm. 



Gibbs and Collette (1959) reported that very 

 small juvenile C. hippurus resembled miniature 

 feathers with dark and light bars alternating 

 along their bodies and dorsal and anal fins. Very 

 small C. equiselis, in contrast, tended to be uni- 

 formly dark along their sides, sometimes dis- 

 playing weak bars along their fins. During the 

 drift, 78 juvenile dolphin were caught by dip net; 

 all were identified as C. equiselis on the basis of 

 pigmentation on the caudal and pelvic fins 

 (Giljbs and Collette, 1959) and vertebral counts 

 (Collette et al., 1969). In the present sample, 

 specimens ranging from 25 mm SL to 90 mm SL 

 all had dark vertical bars on their bodies; the 

 bars were most pronounced over the anal fin on 

 the ventral half of the fish (Figure 2). The 

 smallest C. equiselis juveniles (less than 25 mm 

 SL) tended to be darker, with less pronounced 



50" 



-r— I — I — I — I — TTT — I — I — r 

 45° 40° W 35° 



Figure 1. — Drift track of the- RV Discoverer during the 

 Atlantic Trade Wind Expedition (ATEX). The square 

 on the insert map represents the area covered by the 

 map. 



' Contribution No. 194, National Marine Fisheries 

 Service, Tropical Atlantic Biological Laboratory, Miami, 

 Fla. 33149. 



Figure 2. — Coryphaena equiselis, 40 mm SL from the 

 tropical mid-Atlantic Ocean, caught aboard the RV 

 Discoverer, 19 February 1969. 



bars or no bars on the body, and specimens 

 larger than 90 mm SL had no bars on their 

 bodies. A single specimen of 230 mm SL ex- 

 hibited no juvenile coloration. The caudal fork 

 margin was dark, as were the pelvic fins; how- 

 ever, the vertebral count (14 + 19 = 33) was 

 that of C. equiselis not C. hippurus (Collette 

 et al., 1969). Sixty-three of the juvenile speci- 

 mens were cleared and stained to obtain verte- 

 bral counts (Table 1), leading to their positive 

 identification as C. equiselis. In counting 



877 



