Female cobia, Rachycentron canadum, were sampled on their spawning grounds in the Northern Gulf of Mexico to study changes in proximate analysis (protein, lipid, carbohydrate, and ash) of the ovaries during gonadal maturation. Four major stages of oocyte development were studied: stage 1, previtellogenesis; stage 2, vitellogenesis; stage 3, final maturation; and stage 4, postovulation. Cobia are multiple spawning fish; therefore, ovaries engaged in a sequential round of oogenesis were distinguished as stages 1' and 2'. Protein was the major constituent of cobia ovaries and its contribution of cobia ovaries and its contribution remained fairly constant (49-55% fo the dry weight) throughout all stages of development. Lipid was the second most abundant component but the levels, ranging from 21 to 41%, changed depending on the stage of ovarian development. Lipid concentration increased from stage 1 through 3 and decreased slightly in stage 4; it was lower in stage-1 than in stage-1' ovaries but was the same in stages 2 and 2'. Carbohydrate was the least aboundant component (3-4%) whereas ash ranked third (6-20%). Most cobia were in prespawning condition (stages 1-3) when they arrived in the northern Gulf of Mexico in April and May; some prespawning fish (stages 1 and 2) were also observed in August and September about a month or two before migration to the overwintering grounds normally ocurs. Cobia undergoing sequential spawning episodes (stages 1' and 2') were captured from April through August. Gonosomatic indices (GSI) were calculated both for ovarian developmental stage and for month of capture. Mean GSI increased as ovarian development proceeded and decreased during postovulation; GSI for month of capture was highest during April and May when the prespawning fish first appeared in northern Gulf of Mexico waters.
Biesiot, P. M.,
Caylor, R. E.,
Franks, J. S.
(1994). Biochemical and Histological Changes During Ovarian Development of Cobia, Rachycentron Canadum, from the Northern Gulf of Mexico. Fishery Bulletin, 92(4), 686-696.
Available at: https://aquila.usm.edu/fac_pubs/6572