Abstract. — Arrowtooth floun- 

 der, Atheresthes stomias, were 

 sampled for macroscopic maturity 

 stage, and females were sub- 

 sampled for gonosomatic index 

 (GSI) from commercial trawl land- 

 ings from July 1991 to July 1992 

 and during the NMFS triennnial 

 bottom trawl survey from Septem- 

 ber to November 1992. Arrowtooth 

 flounder are batch spawners and 

 spawn from fall to winter off Wash- 

 ington at depths of at least 366 m 

 (200 fm). Hydrated oocytes were 

 first seen in September 1991 when 

 mean GSI for yolked oocyte-bear- 

 ing females approximately 

 doubled. Postovulatory follicles 

 were present in all macroscopic 

 stages of mature ovaries sampled 

 for histology in late December 

 1991. By March 1992 all mature 

 females were spent; females with 

 hydrated oocytes were again seen 

 in November 1992. Arrowtooth 

 flounder show a group-synchro- 

 nous pattern of oocyte develop- 

 ment. Catch rates from trawl log- 

 book data suggest that the mature 

 population migrates seasonally, 

 from depths of about 183 m (100 

 fm) in summer to depths exceeding 

 475 m (260 fm) in winter. Fork 

 length at which 50% of fish were 

 sexually mature (L 50% ) calculated 

 from survey data was 28.0 cm for 

 males and 36.8 cm for females, 

 similar to estimates from Washing- 

 ton commercial trawl data but less 

 than estimates from Oregon in the 

 1970s. Female L 50% varied season- 

 ally. Problems of bias associated 

 with sampling commercial trawl 

 landings for size at maturity are 

 discussed. 



Maturity, spawning, and seasonal 

 movement of arrowtooth flounder, 

 Atheresthes stomias, off Washington 



Martha H. Rickey 



Marine Resources Division 



Washington Department of Fish and Wildlife 



600 Capitol Way N 



Olympia. Washington 98501-1091 



Manuscript accepted 27 June 1994. 

 Fishery Bulletin 93:127-138 (1995). 



Arrowtooth flounder, Atheresthes 

 stomias, is a large, predatory flat- 

 fish ranging from the Bering Sea to 

 central California (Hart, 1973). It 

 is estimated to be the single most 

 abundant species in the Gulf of 

 Alaska and has shown significant 

 increases there in both population 

 numbers and biomass. 1 Arrowtooth 

 flounder is typically not considered 

 a high-value species in the Wash- 

 ington trawl fishery, but recent 

 landings have been substantial. In 

 1990-92 more arrowtooth flounder 

 were landed from areas off Wash- 

 ington than any other groundfish 

 species except Pacific whiting, 2 and 

 management interest in arrowtooth 

 flounder has intensified. Little de- 

 tailed information is available on 

 arrowtooth flounder in the eastern 

 Pacific Ocean. Kabata and For- 

 rester (1974) studied parasitic in- 

 fection of arrowtooth flounder off 

 British Columbia and noted the 

 population length and age structure 

 as well as diet, but did not examine 

 maturity. Pertseva-Ostroumova 

 (1960) examined Atheresthes repro- 

 duction and larval development in 

 the Bering Sea, but spawning data 

 on A. stomias was limited and con- 

 clusions regarding time and depth 

 of spawning were based primarily 

 on the closely related Kamchatka 

 flounder, A. evermanni. More recent 

 genetic and food-habit studies have 

 documented differences between 

 arrowtooth flounder and Kam- 

 chatka flounder in the Bering Sea 



(e.g. Ranck et al., 1986; Yang and 

 Livingston, 1986; Yang, 1988), but 

 none have examined their reproduc- 

 tion. Unpublished arrowtooth floun- 

 der size-at-maturity estimates have 

 been made from data collected off 

 Oregon. 3 This study was designed to 

 provide new estimates of size at ma- 

 turity and a time series of reproduc- 

 tive development and spawning of 

 arrowtooth flounder off Washington. 



Methods 



Maturity data were collected from 

 three sources: 1) Washington com- 

 mercial trawl landings ("market"- 

 sized fish) sampled biweekly from 

 July 1991 to July 1992 at shoreside 

 processing plants; 2) fish normally 

 discarded at sea because of their 

 small size, brought in by fishermen 



1 Wilderbuer, T. K., and E. S. Brown. 1992. 

 Flatfish. In Stock assessment and fishery 

 evaluation report for the 1993 Gulf of 

 Alaska groundfish fishery, Section 3. N. 

 Pac. Fish. Manage. Counc, Anchorage, AK, 

 25 p. 



2 Pacific Fishery Management Council. 

 1993. Status of the Pacific coast ground- 

 fish fishery through 1993 and recom- 

 mended biological catches for 1994: stock 

 assessment and fishery evaluation. (Docu- 

 ment prepared for the Council and its ad- 

 visory entities.) Pac. Fish. Manage. Counc, 

 2000 SW First Ave., Ste. 420, Portland, OR 

 97201. 



3 Hosie, M. J., and W. H. Barss. 1977. Age 

 and length at maturity of arrowtooth floun- 

 der, Atheresthes stomias, in Oregon waters. 

 Oregon Dep. Fish Wildl. unpubl. manuscr., 

 13 p. 



127 



