Abstract. -Recruitment of indi- 

 viduals from the epipelagic phase to 

 the demersal armorhead Pseudo- 

 pentaceros wheeleri population at 

 Southeast (SE) Hancock Seamount 

 has typically been recognized by the 

 influx of fish with a high fatness in- 

 dex (FI; body depth relative to fork 

 length). Reliance on this index was 

 dictated by the peculiarity of the sea- 

 mount life history stage in which 

 armorhead cease somatic growth 

 soon after recruitment to the sea- 

 mount and FI declines during sea- 

 mount residence until death. Lim- 

 ited sampling opportunities and 

 variability in FI at the time of re- 

 cruitment preclude the exclusive use 

 of FI as a means of identifying newly 

 arrived recruits among recruits-of- 

 the-year and hence the timing of an- 

 nual recruitment. Settlement and 

 recruitment to the seamount popu- 

 lation are synonymous. Efforts to de- 

 velop a method of identifying new 

 recruits were initiated by an exami- 

 nation of epipelagic and seamount 

 (SE Hancock) armorhead for differ- 

 ences in macroparasites as well as 

 hepatosomatic and visceral fat-so- 

 matic indices. Of the two condition 

 indices, the hepatosomatic index 

 held the most potential but was con- 

 sidered too labile because pre- 

 recruits probably experience de- 

 creases that vary according to ener- 

 getic demands during seamount 

 migration. The monogenean gill 

 parasite Microcotyle macropharynx 

 was highly prevalent among sea- 

 mount individuals in all sampling 

 periods but absent from epipelagics. 

 Based on probable rapid infection 

 and maturation, identification of new 

 recruits was based on the absence 

 of mature M. macrophaynx. Results 

 indicate that significant new recruit- 

 ment occurred only during the late 

 spring to midsummer sampling pe- 

 riods, and the mean FI of new sea- 

 mount recruits was lower than that 

 of comparable size epipelagics. 



Use of a monogenean gill parasite 

 and feasibility of condition 

 indices for identifying new recruits 

 to a seamount population 

 of armorhead Pseudopentaceros 

 wheeleri (Pentacerotidae) 



Robert L. Humphreys Jr. 



Honolulu Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service. NOAA 



2570 Dole Street, Honolulu, Hawaii 96822-2396 



Mark A. Crossler 



Honolulu Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service, NOAA 



2570 Dole Street. Honolulu, Hawaii 96822-2396 



Present address: School of Business Administration 

 University of Oregon, Eugene, Oregon 97402 



Craig M. Rowland 



Honolulu Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service, NOAA 



2570 Dole Street, Honolulu, Hawaii 96822-2396 



Present address: U.S. Fish and Wildlife Service, PO Box 50167, Honolulu. 

 Hawaii 96850 



Manuscript accepted: 19 March 1993 

 Fishery Bulletin 91:455-463 ( 1993) 



The armorhead Pseudopentaceros 

 wheeleri (Hardy) in the North Pacific 

 Ocean initially occupies an epipelagic 

 and then demersal habitat during its 

 life history. Progeny originate from 

 winter spawning of the demersal 

 armorhead population associated 

 with the summit and upper slopes of 

 the southern Emperor-northern Ha- 

 waiian Ridge (SE-NHR) seamounts 

 (Fig. 1) (Bilim et al., 1978; Borets, 

 1979). Larvae are initially found in 

 surface waters around the seamounts 

 (Fedosova and Komrakov, 1975; 

 Borets, 1979) but soon move or are 

 advected into subarctic waters of the 

 central and northeastern Pacific 

 (Boehlert and Sasaki, 1988). Here 

 they feed in oceanic surface waters 

 and undergo somatic growth, accu- 

 mulate energy reserves, but experi- 

 ence no reproductive development. 

 These epipelagic individuals appear 



deep-bodied and display a striking 

 pattern of blue and silver blotches 

 along their dorsal and lateral regions. 

 The process and timing by which 

 epipelagic individuals recruit back to 

 the SE-NHR seamounts is not well 

 understood (Boehlert and Sasaki, 

 1988). Individuals are primarily 28- 

 33 cm fork length (FL) upon recruit- 

 ment to the SE-NHR seamounts 

 (Humphreys et al., 1989). Since re- 

 cruits are similar in length and co- 

 occur among the resident seamount 

 population, settlement and recruit- 

 ment to the seamounts are consid- 

 ered synonymous events ( Humphreys 

 et al, 1989). Unlike the epipelagics, 

 the seamount population is demer- 

 sal and virtually uniform in length, 

 but morphologically variable. Three 

 morphological variants (the "fat," "in- 

 termediate," and "lean" morphotypes) 

 were previously recognized and found 



455 



