456 



Fishery Bulletin 91(3), 1993 



to represent different stages of the demersal seamount 

 phase (Humphreys et al., 1989). This variation inter- 

 grades from the deep-bodied, overall bluish-gray col- 

 oration of presumably recent recruits (fat morphotype) 

 through progressively leaner forms of uniformly brown- 

 ish coloration (intermediate and lean morphotypes). 

 Relative body depth refers to the ratio of body depth 

 at first anal spine to FL and hereafter is called the 

 fatness index (FI; Somerton and Kikkawa, 1992). Us- 

 age of FI values recognizes that these variations form 

 a continuum rather than discrete changes and has re- 

 placed classification by morphotype (Somerton and 

 Kikkawa, 1992). Declining FI reflects the transforma- 

 tion by individuals as the elapsed time of seamount 

 residence increases. During this phase, somatic growth 

 ceases upon recruitment, and stored energy reserves 

 are eventually mobilized for reproductive development 

 and spawning. These processes contribute to the de- 

 cline in FI and ultimately lead to death (Humphreys 

 etal., 1989). 



The discovery of large aggregations of armorhead 

 over the summits and upper slopes of SE-NHR sea- 

 mounts (Fig. 1) during exploratory work by the former 

 Soviet Union in 1967-1969 (Komrakov, 1970) led to a 

 full-scale bottom trawl fishery in this region by both 

 Japanese and the former Soviet trawl fleet (Uchida 

 and Tagami, 1984). By the end of 1975, the cumulative 

 combined fleet catch of armorhead was some 880,000 

 metric tons (t). Total annual catch of armorhead by 

 the Japanese trawl fleet declined dramatically after 

 1976 (Humphreys et al., 1984) and continues to re- 

 main low throughout the SE-NHR region (R. 

 Humphreys, unpubl. data). In 1977 the Hancock Sea- 

 mounts, located in the southermost portion of the SE- 

 NHR trawl fishery, came under U.S. jurisdiction with 

 the implementation of the 200-mile fishery conserva- 

 tion zone (Humphreys et al., 1984). During 1978-1984, 

 several Japanese trawlers were allowed to fish the 

 Hancock Seamounts but were regulated by permit and 

 an annual catch quota (Uchida and Tagami, 1984; 



-UJt 



1 \ 



Koko Seamount 



Kimmei Seamount 



_ Oaikakuji Seamount -^ 



Yuryaku Seamount 

 MILWAUKEE 



SEAMOUNT 

 . GROUP 

 J<ammu Seamount 



Xolahan Seamount 



-32°- 



■^.C-H Seamount 



N W Hancock Seamount 

 Q Cs Ihancock 



& sSSSSt  ".SEAMOUNTS ; 



..Seamount No 10 



Seamount No M  



-29°- 



, , Lodd Seomount 



'Nero Seamount." 



.MIDWAY 'IS.. 



=-PEARL 8 - 



*J HERMES REEF 



:.Seomount No 9 



Seomount No 8 



LISIANSKI 



171" E 172° 



173° 174° 175° 



176° 177° 178° 179° 180° 179° 178° 177° 176° 175° 174° W 



Figure 1 



The major habitat of dermersal armorhead is located over the southern Emperor-northern Hawaiian Ridge (SE-NHR) seamounts 

 extending from Koko Seamount to the northwest down through the Hancock Seamounts in the southeast region. 



