Growth patterns of three bivalve species targeted by the Ocean Cockle Fishery, southern New South Wales: Eucrassatella kingicola (Lamarck, 1805); Glycymeris grayana (Dunker, 1857); and Callista (Notocallista) kingii (Gray, 1827)

ABSTRACT

The Ocean Cockle Fishery is a small fishery in southern New South Wales targeting three bivalve species: Eucrassatella kingicola; Glycymeris grayana; and Callista (Notocallista) kingii. The fishery currently consists of a single licensed fisher harvesting a defined patch of seabed but has been identified as potentially able to support expansion. All target species have unknown population dynamics and life histories, and the degree to which expansion can be supported is therefore also unknown. We used internal growth marks in cross sections of shell to determine ages from the commercial catch. The assumption that the alternating bands represent seasonal variations in growth rate was validated by laser ablation induction-coupled plasma mass spectrometry (LA-ICPMS), a small tag-recapture program and preliminary marginal increment analysis. Mean length-at-age was modelled using the von Bertalanffy growth equation. Callista kingii (L_∞ = 43.8, K = 0.43) grew substantially faster to a smaller maximum size than E. kingicola (L_∞ = 70.0, K = 0.18) and G. grayana (L_∞ = 54.3, K = 0.20). These growth characteristics may explain anecdotal observations that C. kingii has increased in relative abundance in recent catches and is relatively rare in unfished areas while E. kingicola in particular has declined in mean size and abundance.

KEYWORDS:

• Crassatellidae
• elemental ratios
• Glycymeridae
• LA-ICPMS
• marginal increment analysis
• shell growth marks
• tag-recapture
• Veneridae
• von Bertalanffy growth model

Acknowledgements

We thank Dr Kevin Rowling, formerly of NSW Fisheries, for assistance in this project, and particular thanks to commercial fisher Allan Broadhurst for supplying the specimens and for his insights into the fishery. Craig Taylor, fisheries technician at Southern Cross University, is thanked for assistance with the sectioning process, and Matthew Tonge (SCU Geoscience and SOLARIS) for his work on the LA-ICPMS. The authors also thank two anonymous reviewers and editors for suggested improvements to the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Renaud Joannes-Boyau http://orcid.org/0000-0002-0452-486X

Additional information

Funding

This work was supported by post-graduate funding from Southern Cross University to P. Beaver.