Fishery Bulletin/U S Dept of Commerce National

358 Abstract.-The biology and distri bution of arrowtooth, Atheresthes sta Biology and distribution of mias, and Kamchatka, A. el1ermanni. flounder were examined in Alaskan arrowtooth, Atheresthes stomias, waters to determine whether there were sufficient differences to justify and Kamchatka, A. evermanni, treating them as separate species in resource assessment surveys conducted flounders in Alaskan waters by the National Marine Fisheries Ser vice. Geographic ranges of the two flounder species overlap in Alaska wa Mark Zimmermann ters; both occur in the eastern Bering Pamela Goddard Sea and western Aleutian Islands re gion. However. only arrowtooth flounder Alaska Fisheries Science Center occur throughout the eastern Aleutian National Marine Fisheries Service. NOM Islands region and the GulfofAlaska. 7600 Sand Point Way NE. Seattle. Washington 98 J 15-0070 Arrowtooth flounder were abundant over a wide range ofdepths (76-450 m) and were more abundant than Kam chatka flounder in catches shallower than 325 m. Kamchatka flounder were abundant only in deep trawl hauls (226-500 m) and were more abundant Arrowtooth flounder, Atheresthes Canada and offthe Washington and than arrowtooth flounder in catches at stomias, and Kamchatka flounder, Oregon coasts for use in animal depths greater than 375 m. Arrowtooth A. evermanni, were not always feeds as well as for human con flounder were also abundant over a treated as separate species in re sumption (Kabata and Forrester, wide range of bottom-water tempera tures (2.1°-4.6°C), whereas Kamchatka source assessment bottom trawl 1974), Softening of the flesh, prob flounder were abundant in a much nar surveys oftheAlaska Fisheries Sci ably caused by an enzyme released rower range of bottom temperatures ence Center (AFSC) prior to 1991 from a myxosporean parasite (3.8°-4.2°CI. By percentage. females because of their similarity in ap (Greene and Babbitt, 1990 >, has lim dominated the arrowtooth flounder pearance, lack ofcommercial impor ited the marketability ofarrowtooth population in the eastern Bering Sea (68.6%) and Aleutian Islands region tance, and the limited abundance of flounder as food. Recent work, how (59.6%), whereas the Kamchatka floun Kamchatka flounder in comparison ever, has shown promise in produc der population was 55.9% and 47.5% with arrowtooth flounder. They ing marketable flounder products, female, respectively. The females of were both grouped as arrowtooth such as arrowtooth flounder fillets both species attained greater length at flounder and possible differences (Greene and Babbitt, 1990), arrow age than did the males. The difference in growth between the sexes was between them were not thoroughly tooth flounder surimi <Wasson etal., greater among arrowtooth flounder and documented. Most of the previous 1992; Porter et al., 1993; Reppond may account for the preponderance of research conducted on Atheresthes et al., 1993>, and Kamchatka floun females in the arrowtooth flounder spp. has treated them as a species der surimi (Haga et al.2). Poten population. complex. The few comparative stud tially, a fishery targeting arrow ies of Atheresthes spp., based on tooth flounder in Alaskan waters morphometrics (Norman, 1934; could have an effect on the Alaskan Wilimovsky et al., 1967; Yang, population ofKamchatka flounder. 1988), genetics (Ranck et al.. 1986), Knowledge ofthe biology ofthe two diet (Yang and Livingston, 1986), species may provide crucial infor and geographic distribution (Shun mation neededfor theirproperman tov, 1965; Wilimovsky et al., 1967; agement and conservation. There Allen and Smith, 1988), have docu fore, since 1991, these species have mented few differences between the been considered as two separate two species. Arrowtooth flounder accounts for 55% of the flatfish biomass in the 1 Brown. E. S. 1994. Alaska Fisheries Science Center, Resource Assessment and western GulfofAlaska (Brown!); it Conservation Engineering Division. 7600 is the dominant flatfish ofthat area, Sand Point Way NE, Seattle, WA 98115. and yet it has not supported a large Personal commun. fishery. Arrowtooth flounder have 2 Haga. H.• R. Shigeoka, and T. Yamauchi. 1980. Method for processing fish con Manuscript accepted 9 January 1996. been caught commercially in small taminated with sporozoa. U.S. Patent Fishery Bulletin 94:358--370 (1996>. fisheries off the Pacific coast of 4,207,354. Jun. 10. Zimmermann and Goddard: Biology and distribution of Atheresthes stomias and A. evermanni 359 species during resource assessment surveys con per eye ofarrowtooth flounder interrupts the profile ducted by the AFSC. ofthe head and can be seen from the blind side. The The purpose ofthe present work was to document upper eye ofthe Kamchatka flounder does not inter the geographical overlap ofthe two flounder species rupt the head profile. Fish whose upper eye was not in Alaskan waters and to describe the ecological dif located with any certainty or which had a damaged ferences, such as length at age, sex-ratios, and depth upper eye were distinguished by number ofgill rakers and temperature preferences that allow such exter (Yang, 1988). After sorting, each species was weighed nally similar species to coexist. Incorporation ofthis separately. Fish size was recorded as fork length, and information into future AFSC surveys may prove es the sex ofeach fish was detennined by making an inci sential for the management ofthe two species. sion posterior to the abdomen on the blind side and by visually inspecting the gonadal tissue. Comparisons were made between the abundance Materials and methods ofthe two species in CPUE (kglha.l by depth interval and water temperature interval. When there were a Data were obtained from bottom trawl surveys con sufficient number of hauls, depth was divided into ducted from research vessels over the continental 25-m intervals and temperature into 0.1DC intervals. shelf«200 m) and slope (200-800 m) ofthe eastern When there were few hauls, catches were grouped Bering Sea and off the Aleutian Islands «500 m). into 100-m depth intervals and 1.0DC intervals. For The surveys were conducted from June through Sep trawl hauls in which both species were caught, a lo tember 1991. Sample design, fishing gear and meth gistic model was developed to show the relationship ods, catch sampling procedures, and data analyses between the proportion ofarrowtooth flounder in the are described by Goddard and Zimmermann3 for the total Atheresthes catch and depth; eastern Bering Sea shelfand slope and by Harrison (993) for the Aleutian Islands. The bottom trawl (In(p/ 1- p) = a +f3x), used in the Bering Sea shelf survey was different from that used in the Bering Sea slope andAleutian where p is the proportion of arrowtooth flounder in Islands region. The bottom trawl used on the Bering the total Atheresthes catch rate, 1 - p is the propor Sea shelf had smaller meshes in the net wings and tion ofKamchatka flounder in the total Atheresthes body and was used without roller gear; therefore it catch rate, a and f3 are constants, and x is the depth fished heavily on the bottom. The bottom trawl used in meters. on the Bering Sea slope and in Aleutian Islands re The geographic distributions ofboth species were gion was used with bobbin roller gear and had larger described from our thorough but depth-limited bot meshes in the net wings and body. Additional data tom trawl survey data, supplemented by data sup were incorporated from the western Gulf ofAlaska plied by the Fishery Observer Program oftheAFSC, bottom trawl survey «500 m) conducted in 1993 but which also supplied species composition data on were used only for defining geographic ranges. Nets catchesfrom deep waters inthe GulfofAlaska. Non were towed at approximately 5.5 kmlhr (3 knots) for linear regressions related mean length ofarrowtooth 30 minutes, covering a distance of2.8 km (1.5 nmi). and Kamchatka flounder by haul to depth; Mean net width, as measured with SCANMAR net BM mensuration gear, was multiplied by the distance L=L~ _Ae , traveled to calculate the area swept by the net. Catch per unit of effort (CPUE) was calculated for each where L is estimated length, L~ is theoretical maxi species for each tow in kilograms per hectare mum length, M is depth in meters, and A and Bare (kglha). Either micro-bathythermograph probes fixed constants. to the net or expendable bathythermograph probes Initial observations indicated an unusually high dropped at the haul sites recorded bottom tempera percentage of females in the arrowtooth flounder tures (±O.lDCI. population. Juvenile fish from which the sex could Arrowtooth and Kamchatka flounders were distin not be determined, generally less than 20 cm in guished by the position oftheir upper eyes. The up- length, were not included in the analysis. The per centage offemales in the arrowtooth flounder popu 3 Goddard, P.• and M. Zimmermann. 1993. Distribution, abun lation was compared against the percentage of fe dance, and biological characteristics ofgroundfish in the east males in the Kamchatka flounder population for both ern Bering Sea based on results of the U.S. bottom trawl sur the Aleutian Islands and the eastern Bering Sea. vey during June-September 1991. AFSC Processed Rep. 93 15, 342 p. Alaska Fisheries Science Center, Nat!. Mar. Fish. Comparisons were also made against the other ma Serv.• NOAA, 7600 Sand PointWay NE, Seattle. WA98115-0070. jor flatfish species in the eastern Bering Sea to de- 360 Fishery Bulletin 94(2), J996 termine whether the unusually high percentage of showed that this approximation ofthe test statistic, females in the arrowtooth flounder population, seem which tests for differences between all growth curve ingly an odd occurrence, was also typical ofthe other parameters simultaneously, can be useful for test species from the same area caught in the same sur ingvon Bertalanffygrowth parameters. The test sta vey. Additional comparisons could not be made from tistic was compared against values from the F-dis data gathered in theAleutian Islands because ofthe tribution at the a=0.05 level ofsignificance.

Load more