STOCK COMPOSITION, GROWTH, MORTALITY, 



AND AVAILABILITY OF PACIFIC SAURY, 



COLOLABIS SAIRA, OF THE NORTHEASTERN 



PACIFIC OCEAN 



Steven E. Hughes^ 



ABSTRACT 



Recent international interest in the Pacific saury (Cololahis saint) resource of the north- 

 eastern Pacific Ocean prompted studies to determine the stock's composition, structure, 

 growth, mortaUty, and availability. 



During August-September 1969-71, data were obtained from more than 5,000 fish 

 sampled from 19 individual schools captured between southern California and Vancouver 

 Island, B.C. Length and age frequency distributions indicate fish grow to 340 mm in 

 length during their 6-year lifespan. Larger fish apparently migrate farthest north and 

 consequently age at full recruitment off Washington is III or IV, and II off Oregon. 

 Spawning is e.xtended over most of the year and the stock is believed homogeneous. First 

 maturity appears to be reached during the second year. Numbers of males and females 

 were nearly equal until age IV when females began to predominate. Length-weight 

 regressions are presented by sex. Berlalanffy growth parameters were calculated: K = 0.42, 

 Lx = 342 mm, and lo = -0.72 years. The total instantaneous mortality coefficient was 

 estimated at 1.25-2.20. 



Data on distribution and availability suggest a viable domestic fishery on this species is 

 unlikely. 



In 1969, an investigation of the distribution, 

 availability, and biology of Pacific saury, 

 Cololabis saira, in the northeastern Pacific 

 Ocean was begun by our laboratory. This study 

 was a direct result of a tenfold decrease in 

 combined Japanese and Soviet landings of the 

 species in the northwestern Pacific Ocean since 

 1958. Unusually high market demand ci'eated 

 international interest in the unexploited stock 

 in the eatern Pacific Ocean. 



Initial studies were concerned primarily with 

 the development of sampling and harvesting 

 gears (Ellis and Hughes, 1971). This paper 

 contains results of research on the biology and 

 availability of saury, except for parasite studies 

 which were treated separately (Hughes, 1973). 

 The purpose of the paper is to provide initial 

 information on stock composition, growth, and 

 mortality and to supplement previous studies 

 of distribution and abundance. Data were ob- 

 tained during research vessel surveys, conduct- 

 ed primarily during August and September 

 1969 off the California coast, and during August 



' Northwest Fisheries Center. National Marine 

 Fisheries Service. NOAA, 2725 Montlake Blvd. £., Seattle, 

 WA 98112. 



Manuscript accepted July 1973. 



FISHERY BULLETIN:' VOL. 72. NO. 1. 1974. 



and September 1970 and 1971 off the Washing- 

 ton and Oregon coasts. 



STATUS OF KNOWLEDGE 



Parin (1960) reported that the Pacific saury 

 inhabits the northern Pacific pelagic zone and 

 has a continuous range from Asia to North 

 America. Sokolovskii (1969) inferred from 

 studies of parasites and biological and mor- 

 phometric characteristics of the species that 

 there exist within its total range, stocks dis- 

 tinguishable from one another — western (Asian), 

 central (Aleutian), and eastern (American) — 

 that there is no clear boundary between these 

 stocks, and that there are rather wide zones of 

 mixture of the stocks. The eastern stock ranges 

 from Baja California to the Gulf of Alaska 

 (Ahlstrom and Casey, 1956; Clemens and 

 Wilby, 1961). Novikov and Kulikov (1966) 

 found that in the eastern Pacific Ocean, saury 

 occupied an extensive coastal region 50-70 

 miles wide between lat. 41° and 48°N during 

 August-October, but that major concentrations 

 were irregularly distributed. Their survey 

 indicated the most dense aggregations occurred 

 off southern Oregon during August, October, 



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