Humphreys et al.: Identification of Pseudopentaceros wheelen "recruits 



461 



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1 -Epipelagic 



2-Seamount, without mature 



Microcotyle Tnacropharynx 

 3-Seamount. Fl^j0.26 

 4-Seamount, with mature 



Aficrocotyle macropharynx 

 5-Seamount. FK0.26 



n =400 n=243 



= 167 



T 



JL 



12 3 4 5 



Armorhead groupings 

 Figure 5 



Visceral fat-somatic index by each grouping of armorhead 

 Pseudopentaceros wheeleri. The mean is indicated by the mid- 

 point horizontal line within each box, one standard deviation 

 about each mean is denoted by the box, and the range is 

 displayed as the horizontal lines above and below the box. 



ined, and its high prevalence among seamount 

 armorhead during all sample periods, support the no- 

 tion that infestation of this parasite originates at the 

 seamount. The prevalence of immature M. macro- 

 pharynx, particularly for those armorhead with FI 

 <0.26, indicates that infestation at the seamount is 

 probably a continuing process. The presence of M. 

 macropharynx in all 775 seamount armorhead with FI 

 of <0.26 also negates the likelihood of a sizable propor- 

 tion of seamount armorhead becoming uninfested over 

 time. 



The maturation rate of M. macropharynx on 

 armorhead remains undetermined, but Thoney (1986) 

 has found the oncomiracidia of the morphologically 

 similar M. sebastis capable of maturing within 12 days 

 on the gills of black rockhsh Sebastes melanops (Girard) 

 off northern California. Although armorhead are dif- 

 ferent hosts, inhabit greater depths, and are geographi- 

 cally distant from black rockfish, the temperature range 

 (12°-17°C) used by Thoney (1986) to determine the 

 maturation time of M. sebastis is similar to that found 

 on the summit and upper slope of SE Hancock Sea- 

 mount. Assuming this rapid maturation also occurs 

 among M. macropharynx infecting armorhead, we pro- 

 pose that armorhead with exclusively immature M. 

 macropharyx have probably only recently become in- 

 fested and have seamount residence times that differ 

 little from those of uninfested armorhead. The 0.26 FI 

 value may represent a lower FI limit for potential new 

 recruits, for only 6% of seamount armorhead without 



mature M. macropharynx had FI values <0.26 and the 

 lowest FI value of the epipelagics examined was 0.26. 

 However, an unknown proportion of armorhead with 

 FI >0.26 perhaps recruit during the previous year at 

 sufficiently high FI values that these FI values still 

 remain above 0.26 when sampled the following year. 

 Even in this situation, such individuals would be in- 

 fected with mature M. macropharynx by the time they 

 are sampled the following year and therefore not mis- 

 taken for new recruits. The presence of M. macro- 

 pharynx probably cannot identify recruits that arrived 

 one or several months before sampling if initial infec- 

 tion occurs soon after recruitment and M. macro- 

 pharynx mature some two weeks thereafter. Hence, 

 our technique can detect only new recruits among the 

 recruit-of-the-year population and is therefore limited 

 to determining whether recruitment is a continuous 

 process. 



Of the two condition indices, VFSI shows little prom- 

 ise as an indicator of new recruits, for the VFSI values 

 in epipelagic and seamount individuals broadly over- 

 lap, regardless of FI and the presence or absence of 

 mature M. macropharynx. Conversely, virtually no over- 

 lap in HSI values occurs between epipelagic individu- 

 als and any of the seamount armorhead groupings. 

 Preliminary results of sagittal otolith increment enu- 

 meration on epipelagic individuals (>27.5cm FL) and 

 SE Hancock armorhead without mature M. macro- 

 pharynx indicates a common age around 2.5 years 

 (R. Humphreys, unpubl. data). This appears to sug- 

 gest that those epipelagic individuals examined either 

 remain pelagic or represent "strays" who will eventu- 

 ally or have begun a delayed movement that will re- 

 sult in recruitment to a SE-NHR seamount but a pro- 

 tracted epipelagic phase. The higher mean HSI value 

 of these epipelagics versus seamount armorhead (FI 

 >0.26) un-infected by mature M. macropharynx sug- 

 gests that HSI decreases somewhere during the period 

 between movement to the seamounts and time of cap- 

 ture after seamount recruitment. To explain the higher 

 mean HSI of epipelagics and evaluate its efficacy as a 

 recruitment indicator, this forementioned period must 

 be examined in relation to both time and distance. 



Of the 27 epipelagic individuals with FLs com- 

 parable to seamount populations (>27.5cm FL) and 

 least distant from the SE-NHR seamounts, 22 were 

 collected around lat. 45°N, long. 155°W; some 2,860 km 

 northeast of the SE-NHR seamounts. Summertime cap- 

 tures of smaller (22-26 cm FL) epipelagics are also 

 frequent from the above general location and indicate 

 an age of some 1.5 years (Boehlert and Sasaki, 1988; 

 R. Humphreys, unpubl. data). Since recruit-of-the-year 

 seamount armorhead are age 2.5 years (R. Humphreys, 

 unpubl. data), these smaller individuals apparently rep- 

 resent the year class which recruit to the SE-NHR 



