FISHERY BULLETIN: VOL. 81, NO. 2 



found (P<0.001). Since this variable was dependent 

 on fish length, and since mean fish length was 

 significantly different between samples (ANOVA, 

 P<0.05), the sample means of GSI were adjusted for 

 length using analysis of covariance (Snedecor and 

 Cochran 1973). 



Adjusted mean monthly GSI values showed a 

 seasonal pattern (Table 3). Values were highest in 

 early April, then fell sharply to their lowest value by 

 late July. From July through September GSI values 

 remained low, then began to rise gradually to reach 

 about 1 1% by the following January and February. A 

 sharp increase was observed from late February 

 through early April. 



Histology of the Ovaries 



The ovarian wall is comprised of three tissue layers 

 (Fig. 1A). The outermost layer (tunica albuginea) is 

 fibrous connective tissue. Internal to this are two 

 layers of smooth muscle tissue. Fibers of the external 

 layer are oriented perpendicularly to the long axis of 

 the ovary, while fibers of the inner smooth muscle 

 layer run parallel to the long axis. Ovigerous folds 

 (lamellae) arise from inner layers of the ovarian wall 

 and extend into the lumen. Margins of these folds are 

 covered by epithelial cells. The entire ovary is en- 

 closed in a thin peritoneum. 



Oogenesis was divided into seven developmental 

 stages based upon the cytological characteristics of 

 the cells. Although the developmental stages through 

 which teleost oocytes pass are quite similar from 

 species to species (Wallace and Selman 1981), the 

 nomenclature used, and the number of stages de- 

 fined, differs considerably between investigators. 

 The terminology used here generally follows that of 

 Yamamoto (1956a). The developmental stages are 

 defined as follows: 



nucleoli located near periphery of nucleus. Nu- 

 cleoplasm slightly basophilic. Cytoplasmic vol- 

 ume greater than in oogonia and deeply basophilic. 

 Surrounded by a single layer of flattened follicle 

 cells (theca). 



Stage HI— Resting (Fig. 1C): Small to inter- 

 mediate in size (23-140 fim), and spherical in 

 shape. Nucleus spherical and large. Chromatin 

 dispersed, granular, and lightly basophilic. Three 

 to ten deeply basophilic nucleoli arranged peri- 

 pherally just inside nuclear envelope. Cytoplasm 

 divided into two concentric zones; the inner deep- 

 ly basophilic and dense, and the outer only slightly 

 basophilic and less dense. Boundary between 

 zones usually poorly defined. Single layer of flat- 

 tened follicle cells surround oocyte (theca). 



Stage IV — Late perinucleolus (Fig. ID): Small to in- 

 termediate in size (39-174 juxn) and spherical in 

 shape. Nucleus spherical and large. Chromatin 

 material dispersed, causing nucleoplasm to ap- 

 pear granular. Five to twenty deeply basophilic 

 nucleoli arranged peripherally around inner sur- 

 face of nuclear envelope. Cytoplasm lightly baso- 

 philic. Oocyte surrounded by a single layer of 

 flattened follicle cells (theca). 



Stage V — Early maturing (Fig. 2A, B): Intermediate 

 to large in size (52-260 jurn), and spherical in 

 shape. Nucleus large and spherical. Chromatin 

 material dispersed. Ten to twenty basophilic 

 nucleoli arranged peripherally, just inside nuclear 

 envelope. Cytoplasm containing either yolk ves- 

 icles (Fig. 2 A) or yolk globules (Fig. 2B) in its outer 

 region. Follicle is composed of a thin inner acido- 

 philic zona radiata and two outer layers of follicle 

 cells; an inner granulosa and an outer theca. 



Stage I— Oogonia (Fig. IB): Small (5-29 jiim), spheri- 

 cal to slightly oval in shape. Nucleus spherical and 

 large, occupying most of cell. Chromatin material 

 appearing as thin threads. One prominent, deeply 

 basophilic nucleolus located at periphery of nu- 

 cleus. Nucleoplasm clear. Cytoplasm very thin 

 and faintly basophilic. Usually associated with a 

 single potential follicle cell. Most often found in 

 small groups, or "nests" of 4 or 5. 



Stage II— Early perinucleolus (Fig. IB): Small 

 (10-78 jum), and angular to round in shape. 

 Nucleus spherical and large. Chromatin material 

 forming chromosomes characteristic of meiotic 

 prophase. Two to five deeply basophilic large 



344 



Stage VI— Late maturing (Fig. 2C, D): Large (104- 

 474 jum), and spherical in shape. In early stages 

 (Fig. 2C), nuclear envelope is distinct, nucleo- 

 plasm is lightly acidophilic, and numerous nucle- 

 oli are located peripherally in nucleus. Cytoplasm 

 is completely full of yolk globules. In later stages 

 (Fig. 2D), nuclear envelope is indistinct, and 

 nucleus is irregularly shaped. Nucleoli dispersed 

 throughout the slightly acidophilic nucleoplasm. 

 Lampbrush chromosomes often apparent. Nucle- 

 us may be located either centrally or toward the 

 periphery of the cell. Zona radiata thick, and 

 radial striations are apparent. Two layers of folli- 

 cle cells are located external to the zona radiata; 

 an inner granulosa and an outer theca. 



