Abstract. - Female yellowtall 

 rockfish Sebastes flavidus, a vivipa- 

 rous species employing intralumenal 

 gestation following fertilization of 

 ovulated eggs, were caught from 

 Cordell Bank (seamount 20 miles 

 west of Pt. Reyes, central California) 

 on a monthly basis from May 1985 

 through April 1986 to determine 

 their annual reproductive cycle. 

 Since histological methods provide 

 precise and detailed information, this 

 method was employed to (1) examine 

 oocytes and embryos to describe 

 developmental stages, and (2) pro- 

 vide temporal assessment of the an- 

 nual reproductive cycle. The descrip- 

 tion and staging scheme developed 

 provide a basis to compare reproduc- 

 tive developmental patterns between 

 cycles and populations. 



Oogonia (Stage I) and early peri- 

 nucleolus (Stage II) oocytes were 

 present in samples from all months. 

 Progressive growth of oocytes from 

 early- to late perinucleolus (Stage III) 

 was evident in spent and recovering 

 ovaries, indicating the end of a repro- 

 ductive year and the beginning of a 

 new reproductive cycle. Initial yolk 

 accumulation (Stage IV) occurred in 

 July, and final yolk accumulation 

 (Stage V) was predominant from 

 September through January. In Feb- 

 ruary, the majority of samples dis- 

 played fertilized ova in early-celled 

 stages of embryonic development. 

 Gestation continued for about 30 

 days with parturition occurring be- 

 tween January and March. Mature 

 oocytes were also collected in March, 

 suggesting the Cordell Bank yellow- 

 tail population has a prolonged re- 

 productive season extending into 

 April. 



Annual reproductive cycle of 

 oocytes and embryos of yellowtail 

 rockfish Sebastes flavidus 

 (Family Scorpaenidae) 



Michael J. Bowers 



Tiburon Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service, NOAA 



3 1 50 Paradise Drive, Tiburon, California 94920 



Manuscript accepted 9 March 1992. 

 Fishery Bulletin, U.S. 90:231-242(1992). 



Sixty species of rockfish (genus Se- 

 bastes) have been recorded in waters 

 off the California coast; twenty spe- 

 cies are utilized by commercial and 

 recreational fisheries (Lenarz 1986). 

 Rockfishes display a wide variety of 

 life history patterns with respect to 

 their habitat and seasonality of repro- 

 duction (Wyllie Echeverria 1987). 

 The majority of investigations on 

 rockfish reproduction have focused 

 on the development, occurrence, and 

 identification of larvae and juveniles. 

 Evaluating annual reproductive suc- 

 cess as a direct consequence of varia- 

 tions in oocyte viability has received 

 less attention. 



The Sebastes complex contributed 

 approximately 37,806 mt to west 

 coast fisheries in 1985 (PFMC 1990) 

 and management of this resource is 

 heavily dependent upon predictions 

 of strong and weak year-classes. 

 Since no single trait accurately rep- 

 resents reproductive capacities of 

 fish populations (Eldridge et al. 

 1991), fisheries management is based 

 on a variety of information. Year- 

 class strength estimates may be en- 

 hanced by understanding factors 

 influencing annual fluctuations in 

 reproduction. Reproduction within 

 this genus is characterized by intra- 

 limienal gestation, followring fertiliza- 

 tion of ovulated, mature eggs. This 

 process is somewhat unique among 

 teleosts occurring only in scorpaenids 

 and zoarcids (Wourms et al. 1988). 

 The investigation described here 



focuses on the development and tem- 

 poral occurrence of oocytes and em- 

 bryos within the ovary of yellowtail 

 rockfish Sebastes flavidus. Character- 

 ization of oocyte growth and embry- 

 onic development provides a basis for 

 assessing reproductive performance. 

 This study is part of a larger effort 

 to acquire information on the repro- 

 ductive biology of yellowtail rockfish 

 to ultimately determine factors that 

 influence reproductive success. 



Although characteristics of oocyte 

 growth are generally similar among 

 teleosts (Wallace and Selman 1981), 

 numerous ovary maturity scales and 

 oocyte classification schemes exist 

 (Yamamoto 1956, Htun-Han 1978, 

 Robb 1982, Howell 1983). These clas- 

 sification schemes are useful for 

 determining reproductive strategies 

 (synchronous, group-synchronous, or 

 asynchronous) and evaluating aspects 

 of reproductive trends. Each oocyte 

 staging system is, however, less like- 

 ly to be adapted for teleosts outside 

 the genus of original study due to the 

 variety of reproductive strategies. 

 An oocyte classification scheme to 

 assess the reproductive status of the 

 marine, viviparous genus Sebastes in 

 the Eastern Pacific has not been 

 reported. Taking these factors under 

 consideration, the objectives of the 

 study reported here were two-fold: 

 (1) to describe oocyte and embryonic 

 development in Sebastes flavidus 

 through one complete reproductive 

 cycle, and (2) establish a staging 



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