O'Malley et al.: Effects of exploitation evident in age-based demography of Pristipomoides flavipinnis and P. auricilla 
325 
The objective of this research was to compare size and 
age information, length at age, growth, and total and nat¬ 
ural mortality rates for 2 deepwater snappers between 
areas with contrasting fishing histories. The lack of fish¬ 
ing effort for goldeneye jobfish at the offshore banks in 
American Samoa since the mid-1980s and for goldflag 
jobfish in the islands of the Mariana Archipelago north of 
Zealandia Bank allows comparison of life history param¬ 
eters between exploited and unexploited areas. Moreover, 
the calculated total mortality rate for an unfished area 
is equivalent to the natural mortality rate. We compared 
mortality estimates produced by using an age-based 
catch curve analysis (for the unfished areas, total mor¬ 
tality equals natural mortality) to those produced by 
using 2 natural mortality estimators that were developed 
from comparative life history studies that incorporated 
maximum ages and growth parameters to predict natu¬ 
ral mortality rates (Then et al., 2015). This study is the 
first detailed age and growth study of an eteline snapper 
in the Samoa or Mariana Archipelago to use the nascent 
methods of age-based life history parameters reported in 
Newman et al. (2015, 2017). 
Materials and methods 
Sampling 
Samples of goldeneye jobfish were collected during 
research cruises in the Samoa Archipelago in March 
2012 and March 2016 and in the Territory of the Wallis 
and Futuna Islands in October 2012 (Fig. 1). Fish sam¬ 
pled from Wallis and Futuna were added to the samples 
from the Samoa Archipelago offshore banks (unfished) 
because of their close proximity and negligible exploita¬ 
tion history (Adams and Chapman 7 ). Goldflag jobfish 
were collected during research cruises in the Mariana 
Archipelago in June and July 2014. The Guam Biosam¬ 
pling Program of the NOAA Pacific Islands Fisheries 
Science Center also provided samples from the commer¬ 
cial fishery operating around Guam and nearby offshore 
banks. 
Fish were sampled during research cruises conducted 
in the Samoa and Mariana Archipelagoes, by using stan¬ 
dard vertical drop lines hauled with hydraulic or elec¬ 
tric reels from depths between 90 and 300 m. Research 
sampling in Wallis and Futuna also used vertical drop 
lines at similar depths between 100 and 400 m (Williams 
et al., 2017). 
Each sampled fish was measured to the nearest millime¬ 
ter (in fork length [FL]) and weighed to the nearest gram. 
Gonads were removed and preserved in 10% buffered 
formaldehyde. Medial transverse sections of the preserved 
gonads were later embedded in paraffin wax, sectioned at 
' Adams, T., and L. Chapman. 2004. Overview of deepwater snap¬ 
per fisheries in the SPC region. Fourth SPC heads of fisheries 
meeting, 30 August-4 September. Seer. Pac. Community, Info. 
Pap. E-IP5, 9 p. 
5 pm, mounted on slides, and stained with Mayer’s hae- 
matoxylin and eosin. These histological slides were used 
to determine the sex of each fish. Sagittal otoliths were 
extracted, cleaned, and stored dry. 
Otolith preparation and aging criteria 
Thin otolith sections were prepared by first mounting the 
whole otolith to a glass slide by using thermal adhesive so 
that the primordium was aligned with the short edge of 
the slide and the sulcus acusticus was aligned perpendic¬ 
ular to the long edge of the slide. The otolith was ground 
transversely and perpendicular to the sulcus to within 
close proximity of the primordium by using 1600-grit 
diamond-coated lap on a grinding wheel. The otolith was 
removed from the slide edge and remounted with the 
previously ground section facing downward; then it was 
ground to a thickness of 130-150 pm. The resulting thin 
section was rinsed in 0.5% HC1 for 20 s, rinsed with fresh 
water, dried, and mounted to a clean slide with a glass 
cover slip. 
Aging criteria for goldeneye jobfish and goldflag job¬ 
fish were developed by experienced readers of deepwa¬ 
ter snapper otoliths during an international workshop 
on the life history of deepwater snappers and groupers 
(Newman et al., 2017) and refined during subsequent 
meetings. Thin sections were examined by using a dis¬ 
secting microscope under transmitted light at 10-50x 
magnification. Fish ages were estimated by enumerat¬ 
ing visible opaque zones that were assumed to be formed 
annually. This pattern of otolith material deposition 
has been validated for other deepwater snappers in the 
Indian Ocean (Newman and Dunk, 2003) and in the 
South and North Pacific Oceans (Newman et al., 2016; 
Wakefield et al., 2017; Williams et al., 2017). Thin oto¬ 
lith sections were read with no knowledge of location, 
date of capture, or fish size. Final decimal age estimates 
were determined by using the number of opaque zones, 
the birth date (peak spawning period: North Pacific, 
1 June; South Pacific, 1 December; Moffitt, 1993), and 
capture date. 
Aging precision and bias, and age determination 
A subsample of otolith sections {n= 50) was read inde¬ 
pendently by 2 experienced readers (goldeneye jobfish: 
C. Wakefield and senior author; goldflag jobfish: R. Nichols 
and senior author). Aging precision (i.e., consistency in 
replicate otolith readings between readers) was assessed 
by using a modified form of the Beamish and Fournier 
(1981) index of average percent error (IAPE) (Wakefield 
et al., 2017): 
lr,D (X:; —X;) 
7APE = -X (1) 
n J_1 x- 
where n = number of samples; 
= the ith count of the jth fish; and 
fj = the median count for the jth fish. 
