Brown-Peterson et al.: Reproductive biology of Rachycentron canadum 
19 
Table 2 
Percentage of cobia in each ovarian maturity class for SEUS (Morehead City, NC, to Cape Canaveral, FL). Monthly data from 
1996 and 1997 were combined. Percentage atresia was calculated for each development stage for ovaries with alpha- or beta-stage 
atresia only. 
Month of capture 
Class 
February 
(n= 3) 
March 
(n=31) 
April 
(22=10) 
May 
(>2 = 10) 
June 
(n= 6) 
Early developing 
66 
41.9 
20 
0 
0 
% atresia 
100 
92 
0 
— 
— 
Mid-developing 
34 
16 
10 
0 
0 
% atresia 
100 
80 
100 
— 
— 
Late developing 
0 
41.9 
70 
100 
100 
% atresia 
— 
85 
66 
60 
0 
Spent 
0 
0 
0 
0 
0 
% atresia 
— 
— 
— 
— 
— 
Regressed 
0 
3.2 
0 
0 
0 
% atresia 
— 
0 
— 
— 
— 
Table 3 
Percentage of cobia in each ovarian maturity class for EGOM (Crystal River to Ft. Meyers, FL). Monthly data from 1996 and 1997 
combined. Percentage atresia was calculated for each development stage for ovaries with alpha- or beta-stage atresia only. 
Class 
Month of capture 
March 
(n= 2) 
April 
(n= 7) 
May 
(n= 3) 
June 
(22= 2) 
July 
(22=6) 
August 
(22=6) 
September 
(22=3) 
October 
(21=11) 
November 
(22 = 13) 
December 
(22=7) 
Immature 
100 
0 
0 
50 
0 
16 
0 
18 
7 
0 
Early developing 
0 
29 
0 
0 
0 
0 
0 
0 
0 
0 
% atresia 
— 
50 
— 
— 
— 
— 
— 
— 
— 
— 
Mid-developing 
0 
14 
66 
0 
0 
0 
0 
0 
0 
0 
% atresia 
— 
0 
50 
— 
— 
— 
— 
— 
— 
— 
Late developing 
0 
57 
33 
50 
83 
67 
33 
0 
0 
0 
% atresia 
— 
50 
0 
0 
0 
50 
0 
— 
— 
— 
Spent 
0 
0 
0 
0 
17 
0 
0 
18 
8 
14 
% atresia 
— 
— 
— 
— 
0 
— 
— 
100 
100 
100 
Regressed 
0 
0 
0 
0 
0 
17 
66 
64 
85 
86 
% atresia 
— 
— 
— 
— 
— 
100 
100 
86 
45 
83 
Histological analysis showed that all males from all ar- 
eas were ripe during all months. Spermatogenic activity 
varied over the reproductive season, but males captured 
during February-May exhibited active spermatogenesis 
throughout the testis. No spermatogenesis occurred dur- 
ing August and September, but the testis contained sper- 
matozoa. Males from EGOM during October through De- 
cember had spermatozoa in the testis, although 50% or 
more of the males in November and December had the tes- 
tis classified as spent. 
Histological examination of ovaries revealed all classes 
of maturity, from early developing through regressed. Dif- 
ferences in monthly ovarian maturity between correspond- 
ing months in 1996 and 1997 were minimal; thus, month- 
ly data were combined (Tables 2-5). A majority of ovaries 
from female cobia were in the late developing class by 
March in the NCGOM (Table 4) and by April in SEUS 
(Table 2) and EGOM (Table 3). Data from the WGOM (Ta- 
ble 5) were limited to only a portion of the reproductive 
season. Ovarian recrudescence began in February in the 
