Spatial subdivision among assemblages of Spanish mackerel, Scomberomorus commerson (Pisces: Scombridae) across northern Australia: implications for fisheries management

Abstract

Aim This study investigated the use of stable d 13 C and d 18 O isotopes in the sagittal otolith carbonate of narrow-barred Spanish mackerel, Scomberomorus commerson, as indicators of population structure across Australia.Location Samples were collected from 25 locations extending from the lower west coast of Western Australia (30°), across northern Australian waters, and to the east coast of Australia (18°) covering a coastline length of approximately 9500 km, including samples from Indonesia. MethodsThe stable d 13 C and d 18 O isotopes in the sagittal otolith carbonate of S. commerson were analysed using standard mass spectrometric techniques. The isotope ratios across northern Australian subregions were subjected to an agglomerative hierarchical cluster analysis to define subregions. Isotope ratios within each of the subregions were compared to assess population structure across Australia.

Stock structure of Grey Mackerel, Scomberomorus semifasciatus (Pisces: Scombridae) across northern Australia, based on otolith stable isotope chemistry

“…Stable isotope analysis of sagittal otolith carbonate is a quick and inexpensive technique to study the degree of mixing between fish populations. Previous studies on a range of fish species (Edmonds and Fletcher 1997;Edmonds et al 1999, Newman et al 2000Ashford and Jones 2007;Newman et al 2009) have indicated that over a wide latitudinal (and temperature) range, significant differences between areas should be detectable in otolith stable isotopes if fish populations in various areas remain separate from each other.…”

“…Previous studies have used stable isotopes within the otolith carbonate of fish to delineate separate stocks or management units and thus the degree of mixing of fish populations among different areas (Edmonds and Fletcher 1997;Kennedy et al 1997;Schwarcz et al 1998;Edmonds et al 1999;Newman et al 2000Newman et al , 2009. Stable isotopes are neutral, nonradioactive variants of an element and, as a result of their slightly different atomic masses; their relative incorporation into fish otoliths can be modified by environmental conditions or biological activity (Campana 1999).…”

“…Knowledge of the stock structure of fish populations aids in the development of rational management plans that facilitate ecologically sustainable development by defining the appropriate spatial scale required for fisheries management (Newman et al 2000(Newman et al , 2009. Information on stock structure is particularly important for fish species that are highly targeted and heavily exploited and/or are being managed as a single homogeneous stock or management unit across a wide spatial area.…”

“…An important consideration in the rational management of fisheries is the ability to determine the stock structure of the targeted fish species (Begg et al 1999;Newman et al 2000Newman et al , 2009. Knowledge of the stock structure of fish populations aids in the development of rational management plans that facilitate ecologically sustainable development by defining the appropriate spatial scale required for fisheries management (Newman et al 2000(Newman et al , 2009.…”

Improving the utility of genetic markers in fish populations

“…The hypothesis that a small (rather than large) number of immigrant genotypes were present in the empirical genotypes is supported by the observations that (a) most adults in a mark-recapture study were found to move less than 100km per year parallel to the shore and (b) isotope signatures in the sagittal otolith carbonate of S. commerson indicated spatial separation across northern Australia (Newman et al, 2009). …”