Fishery Bulletin 101(1) 



180 



Figure 1 



Sampling localities for 328 adult (circles) and 96 juvenile (squares) Pacific halibut, Hippoglossus 

 stenolepis, in the northeast Pacific. OR = Oregon-northern California, WA = Washington, VI = Van- 

 couver Island, SQC = southern Queen Charlotte Islands, NQC = northern Queen Charlotte Islands, 

 SAl = southeast Alaska site 1, SA2 = southeast Alaska site 2, KP = Kenai Peninsula, KI = Kodiak 

 Island, NI = Nagai Island, UP = Unimak Pass, WAL = western Aleutian Islands, SB = southern Bering 

 Sea, PI = Pribilof Island, SMI = St. Matthew Island. Individual hauls with at least 10 fish (for a total 

 of 202 fish) are shown as solid circles. Other collection sites are shown as stippled circles. See Table 

 1 for sample sizes. 



reviews by Lester, 1990;Moser, 1991;Williamset al., 1992). 

 With respect to flatfish, Gibson ( 1972) used parasitological 

 data to distinguish three groups of Platichthys flesus and 

 Krzykawski and Wierzbicka (1982) used parasitological 

 data and other information to distinguish between Bar- 

 ents Sea and Labrador stocks of Greenland hahbut, Rein- 

 hardtius hippoglossoides. Khan et al. (1982) and Arthur 

 and Albert (1993) used parasites to distinguish between 

 Atlantic and Gulf of St. Lawrence stocks of/?, hippoglos- 

 soides, and Boje et al. (1997) used parasites to indicate 

 differences among Greenland stocks of Greenland halibut 

 and stocks from the western Atlantic. No similar work on 

 flatfishes has been done in the Pacific and, with the excep- 

 tion of Krzykawski and Wierzbicka ( 1982) and Boje et al. 

 (1997), there has been no attempt to distinguish between 

 stocks of a species across a significant portion of the spe- 

 cies' range. 



In this article, we use discriminant analysis on counts of 

 some of the parasites from adult Pacific halibut to deter- 

 mine if they form discrete groups or stocks in the north- 

 east Pacific. We do a similar analysis on the juvenile fish 

 and compare the results to the adult analysis to determine 

 when separation is likely to occur 



Materials and methods 



A total of 328 adults ( >55 cm fork length) from 15 composite 

 localities, ranging from northern California to the vicinity 

 of St. Matthew's Island in the Bering Sea and 96 juveniles 

 (10-55 cm) from five localities ranging from the north- 

 ern Queen Charlotte Islands to the Bering Sea (Fig. 1), 

 were caught by staffs of the IPHC and the U.S. National 

 Marine Fisheries Service during the summers of 1990-92 

 (using longlines and trawls). Most localities (for the adult 

 samples) included fish taken from several hauls; however, 

 202 fish came from 13 individual hauls, each of which con- 

 tained at least 10 fish. Fish were bagged individually and 

 immediately frozen at sea for later examination. 



Fish and parasites were processed by using standard 

 parasitological techniques (see Blaylock et al., 1998a). We 

 followed Bush et al.'s (1997) definitions for prevalence, 

 abundance, and intensity. Parasites used in the analyses 

 were chosen according to the guidelines of Arthur and 

 Albert (1993). Only those species with infections of long 

 duration, that do not multiply in the host, and that have 

 a relatively high abundance in at least one geographic 

 locality were used. Of the 59 parasite taxa identified from 



