NOTES 



FECUNDITY OF THE WIDOW ROCKFISH, 



SEBASTES ENTOMELAS, 



OFF THE COAST OF OREGON 



During the past several years a strong fishery 

 has developed for the widow rockfish, Sebastes 

 entomelas. Historical records and the trace 

 amounts captured in early demersal fish surveys 

 (Alverson et al. 1964) contrast sharply with re- 

 cent catches. Between 1963 and 1977, for exam- 

 ple, total catches from 16 to 666 metric tons (t) 

 were landed in Washington, Oregon, and north- 

 ern California as compared with 19,526 1 in 1980 

 (Demory 1 ). Traditional demersal fish surveys 

 have undersampled this species because of both 

 its level of aggregation and its midwater habits 

 (Alverson et al. 1964; Gunderson and Sample 

 1980) and have therefore not recognized the 

 value of the resource. The increased importance 

 of S. entomelas in the west coast trawl fishery has 

 resulted in increased effort to obtain biological 

 information necessary for management of the 

 fishery (Lenarz and Gunderson 2 ). 



This note is intended to describe the fecundity 

 of S. entomelas off Oregon as a function of length 

 and weight, adding to the limited information 

 available from samples collected in 1957 through 

 1959 and described by Phillips (1964). 



Materials and Methods 



Sebastes entomelas ovaries were collected in 

 December 1980 and January 1981 during port 

 sampling in Newport, Oreg., by the Oregon De- 

 partment of Fish and Wildlife. All samples were 

 taken from commercial midwater trawling ves- 

 sels which had fished off central Oregon (lat. 

 42°30' to 45°00'N). While the port sampling was 

 random with respect to size, the samples selected 

 for fecundity analysis were size stratified, and 

 large and small samples were relatively over- 

 represented. Each specimen was measured to 

 the nearest centimeter in fork length (FL) and 



weighed to the nearest 10 g; otoliths were re- 

 moved for subsequent age determination. Ova- 

 ries used for fecundity estimates in the present 

 study were those with yolked oocytes correspond- 

 ing to maturity stage 3 of Barss and Echever- 

 ria, 3 although eggs were counted in a few fer- 

 tilized ovaries which, when collected, showed no 

 signs of extrusion. Whole ovaries were preserved 

 in Gilson's solution modified as described in Gun- 

 derson et al. (1980). The solution was changed 

 after approximately 1 wk, and after two more 

 weeks the ovaries were teased apart with forceps 

 and shaken at regular intervals to facilitate sepa- 

 ration of ovarian tissue from oocytes. Finally, 

 after approximately 3 mo, the ovaries were put 

 through a coarse strainer under running water, 

 which aided in separating oocytes from ovarian 

 tissue. 



Oocyte counts were made by the wet sub- 

 sampling method (Bagenal and Braum 1968). 

 Oocytes were placed in a beaker and the contents 

 were diluted to a final volume dependent upon 

 the size of the ovary, but varying from 200 to 

 2,000 ml. The oocytes and water were placed on a 

 magnetic stirrer and stirred until a homogeneous 

 mixture was obtained. Six subsamples (2 ml 

 each) were taken by pipette and placed in vials. 

 Three to six subsamples were counted (depend- 

 ing upon variability of the first three counts) 

 under a binocular microscope. Since all ovaries 

 were mature and within a month of fertilization, 

 there was no difficulty in discerning and count- 

 ing maturing oocytes. Fecundity was estimated 

 by multiplying the mean number of maturing 

 oocytes per milliliter by the volume of water and 

 oocytes from which the subsamples were drawn. 



Results and Discussion 



Sixty-eight ovaries from S. entomelas were col- 

 lected, three in December 1980 and 65 in Janu- 

 ary 1981. Four of the ovaries showed signs of fer- 

 tilization; although counts were taken on these 

 four specimens, they were not included in the 



'Robert L. Demory, Oregon Department of Fish and Wild- 

 life, Newport, OR 97365, pers. commun. January 1982. 



2 Lenarz, W. H., and D. R. Gunderson. 1980. Summary of 

 the widow rockfish workshop. Unpubl. manuscr. South- 

 west Fisheries Center Tiburon Laboratory, National Marine 

 Fisheries Service, NOAA, Tiburon, CA 94920. 



3 Barss, W. H., and T. Echeverria. 1980. Maturity of 

 widow rockfish (Sebastes entomelas) from the northeastern 

 Pacific, 1977-1981. Unpubl. manuscr. Southwest Fisheries 

 Center Tiburon Laboratory, National Marine Fisheries Ser- 

 vice. NOAA, Tiburon, CA 94920. 



FISHERY BULLETIN: VOL. 80. NO. 4. 1982. 



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