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Fishery Bulletin 111(4) 
West Pacific, extending from East Africa to Fiji, north 
to the Ryukyu Islands and south to Australia (Allen, 
1985). In Southeast Asia, this species is called jenahak 
or ang cho and is important in both wild-harvest fish- 
eries and sea-cage mariculture (Tanaka et al., 2011). In 
Australia, this species is known as “Golden Snapper” or 
“Fingermark” and is a dominant, large lutjanid of the 
nearshore community of reef fishes from the Kimber- 
ley region (-124° E) in northwestern Australia, across 
northern Australia, and down the Queensland coast to 
at least 23° S (Travers et al., 2009). Juvenile and young- 
er adult John’s Snapper generally are associated with the 
lower reaches of mangrove-lined estuaries (Kiso and Ma- 
hyam, 2003) and eventually move offshore toward fring- 
ing and coastal reefs (Tanaka et al., 2011). Large adults 
in Australia are found schooling in turbid waters around 
hard substrata and complex topography in muddy coastal 
areas and occasionally on deeper, sandier trawl grounds 
offshore (Marriott and Cappo, 2000). 
Australia’s northern coastline is mostly uninhabit- 
ed by humans or sparsely populated and remote from 
domestic markets. The Northern Territory is the only 
state that reports landings of John’s Snapper. The 
coastal hook-and-line fishery of the Northern Territory 
reported landings of only 8.64 metric tons (t) in 2009, 
5.34 t in 2010, and 4.38 t in 2011 (Northern Territory 
Government 1 ). John’s Snapper is a prized sportfish in 
Australia and Malaysia, but skilled fishing techniques 
and approaches, such as night fishing and live squid 
baits, often are required to catch one. Sportfishing and 
spearfishing interest in John’s Snapper is expanding in 
northern Australia with both the development of char- 
ter operations in remote locations and the rapid devel- 
opment of marine electronics for use on small boats to 
echolocate fish. Most charter boat operators and many 
top anglers practice catch and release for this species. 
Longevities of <10 years have been published for 
John’s Snapper from the reading of scales (Andaman 
Sea; Druzhinin, 1970) and from a single length-fre- 
quency composition (Bay of Bengal; Khan, 1986). The 
growth parameters from these studies still compose the 
major information source for John’s Snapper (FishBase, 
http://www.fishbase.org/search.php; Froese, 2011). Both 
techniques are well known to have serious bias where 
size is uncoupled from age and where under-aging can 
lead to a three-fold overestimation of natural mortal- 
ity for lutjanids (Newman et al., 2000), thus inflating 
estimates of potential fishery yield. 
The primary objectives of this study were, therefore, 
1) to describe the age composition, growth, and mortali- 
ty of John’s Snapper on the basis of age estimates from 
sectioned otoliths; 2) to quantify spatial variability in 
the length, otolith weight at age, and gonad weight at 
length of populations of John’s Snapper along a lati- 
1 Northern Territory Government. 2012. Fishery Status Re- 
ports 2011, 162 p. Northern Territory Government, Depart- 
ment of Primary Industry and Fisheries, Darwin, NT, Aus- 
tralia. Fishery Report No. 111. [Available from http://www. 
nt.gov au/d/Content/File/p/Fish_Rep/FRl 1 1 pdf.] 
tudinal gradient, and 3) to examine catch records for 
other large lutjanids for signs of latitudinal variation 
in maximum size in the Indo-West Pacific. 
Materials and methods 
Sampling methods and locality 
Filleted fish frames or whole specimens (identified using 
Allen, 1985) were collected during the period of Febru- 
ary 1989-April 2002 from fish processing facilities, re- 
search surveys, sportfishing charter operators, anglers, 
and spearfishing individuals in 4 regions: the coast of 
the Kimberley (Western Australia); the Arafura Sea 
(Northern Territory); coast of Cape York (Queensland); 
and the coast from Townsville to Cairns (Queensland) 
(Fig. 1). The fork lengths (FL) were recorded in milli- 
meters, and, where whole fish were available (rz— 129), 
whole weights (W^r) were measured in grams. Sagit- 
tae (hereafter, referred to as “otoliths”) were removed 
from under the gill covers, washed, dried, weighed, and 
measured. Notable gaps in full information occurred 
because volunteers contributed mainly eviscerated 
fish frames. Of the 948 fish that were aged, 863 had 
reliable FL and 928 had reliable otolith weights. Sex 
was determined by macroscopic examination for 786 
fish, but whole gonad weights (Wq) were measured, in 
grams, for only 277 of them. 
Estimation of fish age 
Three transverse sections were cut from otoliths em- 
bedded in resin with a low speed circular saw and 
diamond watering blade in the vicinity of the primor- 
dium. The sections were 0.25-0.50 mm thick, depend- 
ing on width of the otolith, and were lightly polished 
on wet ebony paper (1000 grade) and lapping film (9 
and 3 pm). The sections were mounted in resin on mi- 
croscope slides under cover slips. Opaque zones — an- 
nuli or annual growth rings — were counted along the 
ventral margin of the sulcus acousticus under reflected 
light against a dark background (see Newman et al., 
2000). These zones are deposited annually from spring 
to early summer (Cappo et al., 2000). Categorization 
of otolith margins indicated that deposition of opaque 
zones occurred over a period of 9 months, with a low 
peak in October for the eastern regions (Cape York and 
north Queensland). 
The index of average percent error (IAPE) (Beamish 
and Fournier, 1981) among readers and readings (east- 
ern regions: IAPE=4.18 ±1.01%, n= 55; Kimberley: 
IAPE=3.96 ±0.92%, rc= 55), was below a benchmark 
IAPE of 5% acceptable for long-lived species (Allman 
et al., 2005), and there was no significant drift in in- 
crement counts in age bias plots (see Campana et al., 
1995). 
A preliminary analysis of monthly mean gonadoso- 
matic index (GSI) values (percentages) was made to 
