653 
Stock discrimination of school 
mackerel, Scomberomorus 
queenslandicus, and spotted mackerel, 
Scomberomorus munroi, in coastal 
waters of eastern Australia by 
analysis of minor and trace 
elements in whole otoliths 
Gavin A. Begg 
Zoology Department, University of Queensland 
St. Lucia, Queensland 4072, Australia 
Present address. Northeast Fisheries Science Center 
National Marine Fisheries Service, NOAA 
166 Water Street, Woods Hole, Massachusetts 02543 
E-mail address.Gavin.Begg@noaa.gov 
Mike Cappo* 
Darren S. Cameron** 
Steve Boyle* 
Michelle J. Sellin** 
* Australian Institute of Marine Science 
PMB No. 3, Townsville, Queensland 4810, Australia 
** Southern Fisheries Centre 
Queensland Department of Primary Industries 
PO Box 76, Deception Bay, Queensland 4508, Australia 
Abstract .—The concentrations of 1 1 
elements in individual whole sagittal 
otoliths from school mackerel ( Scomber- 
omorus queenslandicus ) and spotted 
mackerel ( Scomberomorus munroi ) col- 
lected in east coast waters of Queens- 
land, Australia (16°S to 28°S) were de- 
termined by using inductively coupled 
plasma atomic emission spectroscopy 
(ICP-AES). Spatial and ontogenetic 
variation in otolith elemental composi- 
tion was examined to make inferences 
about the stock structure of these spe- 
cies. Stepwise canonical discriminant 
analyses of the concentrations of 
barium, potassium, magnesium, man- 
ganese, sodium, phosphorus, sulphur, 
and strontium were used to differenti- 
ate groups of fish. These analyses iden- 
tified an optimum grouping of at least 
two stocks of school mackerel and a 
single stock of spotted mackerel in the 
study region, although our results 
showed that the most informative com- 
parisons were made among fish of the 
same year class. The age of fish in col- 
lected samples produced strongly sig- 
nificant effects on mean elemental com- 
position of otoliths. These patterns of- 
fered independent support for hypoth- 
eses about stock structure from previ- 
ous tagging, catch monitoring, ageing, 
and reproductive studies. Discrimina- 
tion between school and spotted mack- 
erel stocks will enable the species to be 
managed on the basis of stock structure 
throughout their east coast distribution. 
Manuscript accepted 25 February 1998. 
Fish. Bull. 96:653-666 (1998). 
Spanish mackerels of the genus 
Scomberomorus have restricted 
ranges and are found in coastal 
waters of eastern Australia within 
the confines of the 20°C isotherm 
(Munro, 1943). Throughout their 
range they form the basis of impor- 
tant commercial, recreational, and 
artisanal fisheries, which are char- 
acterized by mixed gear types, sea- 
sonal availability at widespread 
points of capture, and movement or 
migration through various coastal 
jurisdictions (Trent et al., 1987; 
Johnson et al., 1994). These traits 
make it necessary, but difficult, to 
identify the stock structure of Scom- 
beromorus species for effective fish- 
eries management. 
Tag-recapture information, catch 
and effort data, reproductive stud- 
ies, larval surveys, and protein elec- 
trophoresis have recently been used 
to determine the stock structure of 
king mackerel (Scomberomorus cav- 
alla) in the Gulf of Mexico and At- 
lantic Ocean (Sutter et al., 1991; 
Johnson et al., 1994). In northern 
Australia, stock structure of the 
large narrow-barred Spanish mack- 
erel (Scomberomorus commerson) 
has been inferred from protein elec- 
trophoresis (Shaklee et al., 1990), 
whereas hypothetical stock struc- 
tures have been developed for the 
“lesser” mackerels — school mack- 
erel (Scomberomorus queenslandi- 
cus) and spotted mackerel (Scorn- 
