Zimmermann and Goddard: Biology and distribution of Atheresthes stonvas and A evermanni 



369 



Barss 7 ). Growth rates of males may decline as they 

 become mature, whereas females, to support the 

 greater reproductive burden of egg production, con- 

 tinue their rapid growth rate and become mature at 

 a larger size (see Roff, 1982). 



Difference in size gives arrowtooth flounder fe- 

 males a survival advantage over males because larger 

 fish are better able to avoid predation. Larger fish 

 are also better able to capture and consume larger 

 items of prey, such as walleye pollock, Thercigra 

 chalcogramma, which are an important part of their 

 diet (Yang and Livingston, 1986). Perhaps this size 

 difference accounts for the high percentage of females 

 in the arrowtooth flounder population. 



Although the possibility of cannibalism influenc- 

 ing the sex ratio of arrowtooth flounder cannot be 

 ignored, it is unlikely because cannibalism is uncom- 

 mon in arrowtooth flounder (Kabata and Forrester, 

 1974; Yang and Livingston, 1986). 



Although the von Bertalanffy growth curve param- 

 eters tested as significantly different between male and 

 female Kamchatka flounder, the difference in length 

 at age between the sexes was less than the difference 

 for arrowtooth flounder and perhaps did not afford a 

 significantly higher survival rate for the females. There 

 were no length-at-age results for Kamchatka flounder 

 previously reported in the literature. 



The unusually high percentage of females in the 

 arrowtooth flounder population, the greater length 

 at age of female arrowtooth flounder over female 

 Kamchatka flounder, the greater depth preference 

 of Kamchatka flounder over arrowtooth flounder, and 

 the geographic boundaries of the two species defined 

 in the study area all indicate significant interspecies 

 differences. We therefore recommend that arrowtooth 

 and Kamchatka flounder be treated as separate spe- 

 cies in resource assessment surveys and for manage- 

 ment purposes. Additional information should be 

 gathered on possible differences in mortality of the 

 male and female arrowtooth flounder, the reason for 

 the greater depth preference of Kamchatka floun- 

 der, and whether or not the Kamchatka flounder popu- 

 lation in the study area is successfully reproducing, or 

 whether it is migrating into the area from the west. 



Acknowledgments 



We thank the many individuals involved in the bot- 

 tom trawl surveys, both in the collection of data at 



7 Hosie, M. J, and W. H. Barss. 1977. Age and length at matu- 

 rity of arrowtooth flounder. Atheresthes stomias, in Oregon 

 waters. Oregon Dept. of Fish and Wildlife, Marine Field Labora- 

 tory, P.O. Box 5430, Charleston, OR 97420. Unpubl. manuscr. , 9 p. 



sea and in the editing of the data into its final for- 

 mat. We express our thanks to the captains and crews 

 aboard the Alaska, Ocean Hope 3, Miller Freeman. 

 Ocean Hope 1, Green Hope, Argosy, and Alsea for 

 providing safe and efficient platforms from which to 

 conduct our operations. We thank Mark Conrad and 

 Ren Narita from the Fishery Observer Program of 

 the AFSC for providing data on catch occurrences of 

 Kamchatka flounder in the Gulf of Alaska. Kent Scott 

 and Julie Lyons of the Age and Growth Unit of the 

 AFSC improved upon the previous method of ageing 

 Atheresthes otoliths. Comments and suggestions from 

 several co-workers, and especially one anonymous 

 reviewer, greatly improved the quality of this manu- 

 script. Finally, thanks go to Jim Ianelli, Dan Kimura, 

 Peter Munro, and Steve Syrjala for their statistical 

 assistance with our data analysis. 



Literature cited 



Allen, M. J., and G. B. Smith. 



1988. Atlas and zoogeography of common fishes in the 

 Bering Sea and northeastern Pacific. U.S. Dep. Commer., 

 NOAATech. Rep. NMFS 66, 151 p. 

 Bakkala, R. G„ J. J. Traynor, K. Teshima, A. M. Shimada, 

 and H. Yamaguchi. 



1985. Results of cooperative U.S. -Japan gToundfish inves- 

 tigations in the eastern Bering Sea during June-Novem- 

 ber 1982. U.S. Dep. Commer., NOAATech. Memo. NMFS 

 F/NWC-87, 448 p. 

 Draper, N. R., and H. Smith. 



1981. Applied regression analysis. 2nd ed. John Wiley and 

 Sons, Inc., New York, NY. 

 Greene, D. H., and J. K. Babbitt. 



1990. Control of muscle softening and protease-parasite 

 interactions in arrowtooth flounder, Atheresthes stomias. 

 J. FoodSci. 55(21:579-580. 

 Harrison, R. C. 



1993. Data report: 1991 bottom trawl survey of the Aleu- 

 tian Islands area. U.S. Dep. Commer., NOAATech. Memo. 

 NMFS-AFSC-12, 144 p. 

 Kabata, Z„ and C. R. Forrester. 



1974. Atheresthes stomias (Jordan and Gilbert. 1880) (Pi- 

 sces: Pleuronectiformes) and its eye parasite Phrixo- 

 cephalus cincinnatus Wilson 1908 (Copepoda: Lernaeo- 

 ceridael in Canadian Pacific waters. J. Fish. Res. Board 

 Can. 31:1589-1595. 

 Kimura, D. K. 



1990. Testing nonlinear regression parameters under 

 heteroscedastic. normally distributed errors. Biometrics 

 46:697-708 

 Kinder, T. H„ and J. D. Schumacher. 



1981. Hydrographic structure over the continental shelf of 

 the southeastern Bering Sea. In D. W. Hood and J. A. 

 Calder (eds. ), The eastern Bering Sea shelf: oceanography 

 and resources, vol. 1, p. 31-52. U.S. Dep. Commer, NOAA. 

 Office of Marine Pollution Assessment, Juneau, Alaska. 

 Moiseev, P. A. 



1953. Cod and flounders of far-eastern waters. [Fisheries 

 Research Board of Canada, Trans. Series 1191 Izvestiya 

 TINRO, vol. 40, p. 1-287. 



