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

Abstract

An investigation into armorhead Pseudopentaceros wheeleri recruitment variation at Southeast Hancock Seamount (in the central North Pacific) focused on the examination of recruit characteristics, primarily those derived from otolith-increment analysis. Otoliths from recruits were sampled from years representing relatively strong (509 metric tons [t] in 1980), moderate (58 t in 1986), and weak (1 t in 1989) recruitment biomass. Recruit body length was also examined among these 3 years and from 10 additional years, providing even higher recruitment contrast. Transverse sections of sagittal otoliths were prepared, and yielded information on the mean and variability in pre-recruit pelagic duration and increment-width profiles. Mean length of female recruits, and to a lesser extent of mean pelagic duration, decreased with increasing recruitment strength. Although generally similar in shape, the mean increment-width sequence spanning the first 1.8 yr of the 2+ yr pelagic phase differed among recruit years. Transitions in sequential increment-width (inflection points) were exhibited among all recruit years and occurred primarily within the first pelagic year interval. The weak 1989 recruit year was most distinct among recruit years in exhibiting lower increment widths at each of these inflection points.

History, Biology, and Conservation of Pacific Endemics 2. The North Pacific Armorhead, Pentaceros wheeleri (Hardy, 1983) (Perciformes, Pentacerotidae)

“…The 2 -2 + yr old pe lagic du ra tions obtained for all (n = 96) sea mount re cruits sam pled over three re cruit years by Humphreys (2000) was at var i ance with youn ger ages (1 + yr olds) of sea mounts re cruits reported by Uchiyama and Sampaga (1990). A new oto lith -based age deter mi na tion study to pro vide age of de mer sal stage fi sh based on FI at age (since growth in length ceases dur ing the de mer sal stage) is required in or der to pro vide the data nec es sary for conducting age -based stock as sess ments.…”

“…Humphreys and Tagami (1986) sim ply stated that ag gre ga tions of P. wheeleri were pres ent over the sum mits of the SE -NHR sea mounts at night but were typ i cally ab sent dur ing the day time. Humphreys (2000) con sid ered postrecruitment move ment of P. wheeleri between sea mounts un like ly, but presented no ev i dence for this sug ges tion.…”

“…These au thors suggested the in fl u ence of ocean o graphic pro cesses on re cruit ment vari a tion, but no such stud ies have yet been made. Humphreys (2000) found sig nifi cant neg a tive cor re la tion be tween mean body length of female re cruits and re cruit ment strength on the south east Hancock Seamount.…”

“…However, age de ter mi na tion of older fi sh was con sid ered dif fi cult as DGIs be come pro gres sively smaller in width with age. Humphreys (2000) detected set tle ment marks on sag it tal oto lith trans verse sec tions, which were char ac ter ized by an abrupt de crease in the width of DGIs, and a change to an erod ed, less dis tinct ap pear ance of the in cre ments, or the pres ence of two or more prominent and closely spaced check marks. An im por tant lim i ta tion of the Uchiyama and Sampaga (1990) study in volved oto lith age counts based on ex am i na tion of unsectioned oto liths.…”

Morphology of pelagic fish eggs identified using mitochondrial DNA and their distribution in waters west of the Mariana Islands

“…Seamounts that are located far offshore have been suggested to have unique ecosystems that provide particular types of habitats for fishes for shelter or feeding (Wilson and Kaufmann 1987;Rogers 1994). Various fish species such as Anguilla japonica (Tsukamoto et al 2003), Maedia abyssalis (Fujikura et al 1998), Pseudopentaceros wheeleri (Humphreys 2000) and Sebastes spp. (Dower and Perry 2001) appear to spawn at or near seamounts.…”