FISHERY BULLETIN: VOL. 81, NO. 2 



TABLE 1. — Collection dates and number of yellowtail flounder 



examined. 



TL, then eviscerated and weighed to the nearest 

 gram wet weight. Both ovaries from a subsample of 

 the examined specimens were weighed to the nearest 

 0.1 g. A GSI was calculated for these individuals as 

 ovary wet weight (g) divided by eviscerated wet 

 weight (g) and expressed as a percentage. 



Based on the macroscopic appearance of the ova- 

 ries, fish were classified into one of five maturity 

 stages following a modification of the International 

 Scale of Sexual Maturity first proposed by Hjort 

 (1910) (Table 2). 



A portion of ovarian tissue was removed from the 

 anterior third of the eyed-side ovary from 25 fish on 

 each sampling date (except November 1977) and fix- 

 ed in Davidson's solution. The histological technique 

 employed was developed for fish gonads by the 

 Florida Department of Natural Resources (reported 



in Yevich and Barszcz 1977). Tissues were embed- 

 ded in Paraplast, 2 sectioned at 6 /mi, and stained 

 using Harris' hematoxylin and Eosin Y. 



Slides of tissue were prepared and scanned at 400X 

 magnification. The first 200 oocytes encountered 

 were classified based upon the degree of chromatin 

 condensation, size and staining characteristics, num- 

 ber and placement of nucleoli, and morphological ap- 

 pearance of the cytoplasm and follicle cells. In 10 fish 

 randomly chosen from the 25 individuals of each 

 sampling date, diameters of the first 50 oocytes en- 

 countered were measured to the nearest micrometer 

 using an ocular micrometer. Measurements were 

 taken only on oocytes sectioned through the nucleus. 

 Such measurements have been shown to be rep- 

 resentative of true oocyte diameters (Foucher and 

 Beamish 1980). The mean diameter of each oocyte 

 type was calculated from the 10 fish in every sample. 

 A one-way analysis of variance (ANOVA) was used to 

 test the null hypothesis that no significant differ- 

 ences in mean diameter were present between sam- 

 ples. When significant differences were found, 

 Student-Newman-Keuls test was employed to ex- 

 amine the differences between samples. 



Percent frequency distributions of the different 

 oocyte types were calculated for each sample by 

 dividing the total number of that type by the total 

 number of oocytes examined in the sample. These 

 fractions were then expressed as percentages. Since 

 the probability of an individual oocyte being cut in a 



2 Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



TABLE 2. — Macroscopic and microscopic characteristics of the different maturity stages in yellowtail flounder. 

 Stages modified from Hjort (1910). Oocyte developmental stages are described in text. 



Maturity stage 



External appearance 



Histological appearance 



I. Immature virgin 



II. Developing virgin, 

 recovering spent 



III. Developing, maturing 



IV. Ripe 



V. Spent 



Ovaries small (2-6 cm], slender, conical, pinkish, 

 and generally translucent. Enveloped in a layer of 

 silvery epithelium. No oocytes visible to the naked 

 eye. 



Ovaries relatively small (6-1 2 cm), rounded, red- 

 dish, and translucent. Ovarian wall thick. Vas- 

 cularization slight. 



Ovaries larger in size (>12 cm) and occupying 

 most of ovarian cavity. Visible oocytes large, yel- 

 lowish in color, and opaque. Ovarian wall thin, 

 translucent, and granular in texture due to under- 

 lying developing oocytes. 



Ovaries very large and distending the body wall. 

 Some oocytes yellowish and opaque, others trans- 

 parent (hyaline) producing a speckled appear- 

 ance. Vascularization heavy. Ovarian wall thin. 

 Ova run from vent upon slight pressure. 



Ovaries flaccid, bloodshot. All visible remaining 

 oocytes clear. 



Mainly Stage II and IV oocytes, few >50 )im, A 

 few Stage I and III oocytes also present. All 

 oocytes with lightly basophilic cytoplasm. Ova- 

 rian wall from 25 to 75 Jim thick. 



Stage II. IV, and V oocytes predominate. Stage IV 

 oocytes are abundant early in this maturity stage, 

 but tend to decline as Stage V oocytes increase 

 later in the period. Most oocytes < 1 50 (im diam- 

 eter. Ovarian wall from 250 to 400 /im thick. 



Mainly Stage III and VI oocytes, but small num- 

 bers of Stages I. II, IV, and V also present. Stage VI 

 oocytes increase in diameter to reach about 370 

 jum just prior to the ripe/running stage. Ovarian 

 wall from 1 00 to 200 /im thick. 



Stage III, VI, and VII oocytes predominate Stage 

 VII oocytes are irregular in shape, about 400 /im in 

 diameter, and often present in the lumen of the 

 ovary. Ovarian wall from 50 to 100 /im thick. 



Many empty and collapsed follicles with relatively 

 few oocytes. Stage III and IV oocytes pre- 

 dominate, with many in transition between these 

 two stages. Small numbers of Stage I, II, and 

 resorbing oocytes also present. Ovarian wall irom 

 250 to 400 Jim thick. 



342 



