Synonymy and Life History of the North Pacific Pelagic Armorhead, Pseudopentaceros wheeleri Hardy (Pisces: Pentacerotidae)

Abstract

Specimens of the nominal rpeciea Pscudopcntacrror whcclcri Hardy and P. pectoralis Hardy were examined morphologically and electrophoretically to test the validity of the two speciea. Samples were collected primarily from the Hancock Seamountr of the muthem Emperor-northern H8waiian Ridge as well as from the North Pacific open ocean and northweatern Hawaiian Irlands. Morphometric resulta indicate continuity between P. wheelmi and P. pectoralis. No evidence of rpeciea aeparation waa revealed in analysea of meristic and electre phoretic data. W e conclude that the North Pacific pelagic armorhead conrists of a ringle, metamorphic rpecies, which we. aa firrt reviaerr. elect to a l l P. whcclm'. A hypothesir ir propoaed that attributa morphological variation to different l i f e history rtages.

Otolith-based assessment of recruitment variation in a North Pacific seamount population of armorhead Pseudopentaceros wheeleri

“…Armorhead undergo a lengthy epipelagic prerecruit phase in subarctic North Pacific waters distant from the SE-NHR seamounts. At the time of annual spring -early summer recruitment (settlement and recruitment into the fishery are synonymous), recruiting individuals have attained maximum size (primarily 28 to 33 cm fork length, FL) but remain nonreproductive (Humphreys et al 1989). Post-recruit movement of armorhead between seamounts is considered unlikely.…”

“…Armorhead cease somatic growth after recruitment, mature, spawning annually during November to March (Japan Fisheries Agency 1974, Sasaki 1974, Bilim et al 1978, and may survive 4 to 5 yr at the seamounts. During seamount residence, individuals gradually become emaciated and experience an irreversible decline in somatic weight (Humphreys et al 1989, Somerton & Kikkawa 1992. Annual increases in armorhead biomass at these seamounts is therefore solely dependent on recruitment.…”

Feeding ecology and daily ration of the pelagic armorhead, Pseudopentaceros wheeleri, at Southeast Hancock Seamount

“…As mentioned earlier, armorhead arrive at the seamounts with tremendous fat reserves which, because of the cessation of somatic growth, are ultimately used for maintenance and reproduction (Humphreys et al 1989). In years subsequent to recruitment, the loss in fat apparently increases the need or desire to feed because the proportion of fish actively feeding increases.…”

“…Young armorhead are either transported or undergo an active migration from the seamounts to the epipelagic waters of the subarctic and transitional Northeast Pacific and Gulf of Alaska where they reside for the next 1.5 to 2.5 years acquiring enormous fat reserves (Boehlert & Sasaki 1988, Humphreys et al 1989, Uchiyama & Sampaga 1990. After attaining a size of 26-33 cm fork length (FL), armorhead return to the seamounts where they quickly assume demersal habits and begin maturation (Humphreys et al 1989).…”

“…It is now known, however, that armorhead arrive at the seamounts with an extraordinarily large amount of stored fat which is subsequently metabolized over the remaining 3 to 4 years of their lives (Humphreys et al 1989). Armorhead eventually lose weight to such an extent that they become emaciated and moribund (Humphreys et al 1989, Somerton & Kikkawa 1992. In the final stages of their lives, their striking changes in body shape are accompanied by morphological changes such as thinning of the gut lining that are characteristic of those induced by starvation (R.L.…”