FISHERY BULLETIN: VOL. 85, NO. 2 



now yellow to golden in color because of a prepon- 

 derance of yellow yolky oocytes in the ovarian 

 lamellae. This initial phase of GSI increases con- 

 tinued through early November, at which time two 

 distinct groupings of females within the population 

 became apparent: those with GSIs remaining <2, 

 and those with GSIs ranging between 10 and 21. 

 Average GSIs in the latter group rose only slightly 

 thereafter, ranging from 13 to 22 by early Decem- 

 ber. The lower GSIs of the rest of the population 

 remained unchanged throughout the remainder of 

 this study. 



During the 1984-85 season, females with high 

 GSIs continued to be caught until mid-January, at 

 which time larger females (>20 cm SL) apparently 

 left the Inlet because none were caught during the 

 3 additional weeks of intensive collecting. In con- 

 trast, during the 1985-86 season, females with high 

 GSIs were only collected through mid-December. 

 Although a few mid-size females were collected 

 through late January of this year after the expen- 

 diture of considerable collecting time and effort, all 

 proved to have small GSIs. 



Oocyte Stages 



A primary purpose of this project was to document 

 the oocyte growth and development that accom- 

 panied these GSI changes during prespawning 

 ovarian recrudescence. Two oocyte development 

 stages of primary interest to us were 1) the stage 

 at which yolk accumulation or vitellogenesis begins, 

 and 2) the stage during, or following, vitellogenic 

 growth when the oocyte first becomes competent 

 to resume meiotic maturation and thereby develop 

 into a fertilizable egg. 



We previously showed two large proteins at M^ 

 = 104,000 and 90,000 to be the major yolk proteins 

 present in mullet oocytes at the end of vitellogenic 

 growth (Greeley et al. 1986b). As evidenced by the 

 de novo appearance of these marker proteins (Fig. 

 2), vitellogenesis in the striped mullet begins in 

 oocytes that are between 0.16 and 0.18 mm in diam- 

 eter. In this study, oocytes 0.16 mm in diameter and 

 smaller are thus considered to be previtellogenic, 

 a broad classification including both primary 

 growth- and yolk vesicle-stage oocytes as described 



200- 



21.5 



14.4- 



104 

 90 



t 



0.14 0.16 0.18 0.20 

 OOCYTE DIAMETER (mm) 



Figure 2.— Polyacrylamide gel electrophoresis of oocyte 

 proteins indicating de novo appearance of yolk proteins in 

 vitellogenic oocytes (0.18 mm in diameter) of the Mugil 

 cephalus, with comparison to smaller previtellogenic and 

 larger vitellogenic oocytes (see text). Molecular weight 

 standards are indicated on the left for comparison; the 

 molecular weights of the two major yolk proteins are shown 

 on the right (arrows). 



190 



