Exon-primed, intron crossing DNAmarkers (EPICs)were screened forMendelian-like allele size polymorphisms
in three stingray species (Himantura gerrardi, Neotrygon kuhlii and Taeniura lymna) from the central Indo-West
Pacific, where they are commercially exploited. Four to 7 size-polymorphic intron loci were selected in a
species, and were subsequently tested as genetic markers of stock structure. Sharp genetic differentiation was
observed between populations within each species across the Indo-Malay-Papua archipelago (Weir and
Cockerham's ^θ-values reaching 0.153–0.557 over a few thousand kilometers). A trend of increasing genetic
differentiation with increasing geographic distance was apparent in N. kuhlii, in which populations distant by
3000 km were differentiated by an estimated ^θ ~0.375. This value was an order of magnitude higher than
usually reported in coastal benthic teleost fishes and indicates strong sub-population structure. This is likely,
at least partly, a consequence of the sedentary benthic habits of N. kuhlii at all life stages. Because replenishment
of overexploited populations of N. kuhlii and two other stingray species from the central Indo-West Pacific is
unlikely at ecological timescales, management should be planned at the local geographic scale.