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



283 



Table 4 



Mean catch (no. larvae/10 neuston tows) of common dolphin (Coryphaena hippurus) and pompano dolphin (C. 

 equiselis) larvae in the northern Gulf of Mexico by month. Collections for 1982-1984 are throughout the Gulf 

 and those from 1986 to 1989 are primarily around the Mississippi River delta. Mean catch is calculated over 

 all stations sampled by month; months are combined across years. Grand mean catch per 10 tows is calcu- 

 lated by dividing total number of larvae collected by all stations sampled. Numbers in parenthesis are posi- 

 tive catch stations over total stations sampled. 



Tax a 



.V 



March 



April 



Mai 



June 



July 



August September October November Grand Total 



C. hippurus 517 0.0(0/13) 3.4 122/100) 7.6(58/221) 2.9(29/208) 0.5(3/92) 0.5(13/248) 13.4(29/163) 3.9(4/33) 16.7(2/3) 4.8(160/1081) 

 C. equiselis 85 0.8(1/13) 1.2(10/100) 0.9(15/221) 1.0(8/208) 0.2(2/92) <0.1 (1/248) 1.8(16/163) 0.6(2/33) 0.0(0/3) 0.8(54/1081) 



Number of larvae. 



counted for about 40% of all common dolphin lar- 

 vae taken. Both collections occurred off the Missis- 

 sippi River delta, one during September 1986 (n=161, 

 195 m station depth ) and the other during May 1988 

 (n-52, 63 m station depth). 



Discussion 



Early preflexion larvae (<4.0-4.5 mm) of pompano 

 dolphin are separated from those of common dolphin 

 by having melanophores along the caudal peduncle 



and scattered throughout the caudal finfold (Figs. 

 1 and 2). Number and placement of spines along the 

 outer shelf of the preopercle also separate species 

 (Table 5). Separation of dolphinfishes is particularly 

 difficult between 4.5 and 8.0 mm because preopercle 

 spines are often difficult to count on larvae not 

 cleared and stained. At >8 mm, common dolphin are 

 more easily separated from pompano dolphin by 

 having pigment on the developing pelvic fins and 

 bands of pigment laterally on the body and median 

 fins (Figs. 1 and 2; Table 5). Differences in caudal- 

 fin pigmentation also separate species by early 



