Journal of the Marine Biological Association of the United Kingdom

Research Article

Applying stock indicators for assessment of a recreational surf clam (Donax deltoides) fishery in Victoria, Australia

Zac Lewisa1a2 c1, Khageswor Giria2a3, Vincent L. Versacea4 and Carol Scarpacia1

a1 Unit of Ecology and Sustainability, School of Engineering and Science, Victoria University, PO BOX 14428, Melbourne Victoria 8001, Australia

a2 Fisheries Research Branch, Department of Primary Industries, 2A Bellarine Hwy, Queenscliff, Victoria 3226, Australia

a3 Biometrics Unit, Future Farming Systems Research Division, Department of Primary Industries, Werribee, Victoria 3030, Australia

a4 School of Information Systems, Deakin University, PO BOX 423 Warrnambool, Victoria 3280, Australia

Abstract

The aim of this study was to apply indicators for monitoring the impacts of harvest in a recreational surf clam fishery. We investigated trends in abundance, biomass and size structure and proportion of sexual maturity for the pipi (Donax deltoides) in Venus Bay, Australia. The surf clam stock was sampled during the peak harvesting season in the Australian summer (November to February) at four sites exposed to varying degrees of recreational harvest. Sampling was based on three transects at each site; with 0.027 m3 (0.3 m × 0.3 m × 0.3 m) quadrats stratified within transects by tidal position. Restricted maximum likelihood mixed model analyses were used to examine fixed effect combinations after including a priori random effect for transect within site. Results demonstrated that relative abundance varied significantly (P = 0.0090) among sampling months but not among sites. Relative abundance declined across the peak summer harvest season. The proportion of maturity varied significantly (P = 0.00026) among sites whereas relative biomass varied significantly (P = 0.0043) among months by sites. Relative biomass and the proportion of maturity were considerably higher at the site exposed to minimal harvest compared to other sites. This study demonstrates that a suite of indictors including biomass, size–frequency and proportion of maturity are likely to provide a more accurate assessment of stock status in recreationally fished surf clam populations, than relative abundance. This highlights the need to develop methods to estimate relative biomass in surf clam populations that are not exploited commercially.

(Received April 17 2012)

(Accepted October 04 2012)

(Online publication December 18 2012)

Keywords

  • fisheries management;
  • recreational harvest;
  • bivalve;
  • pipi;
  • cockle

Correspondence

c1 Correspondence should be addressed to: Zac Lewis, Unit of Ecology and Sustainability, School of Engineering and Science, Victoria University, PO BOX 14428, Melbourne Victoria 8001, Australia email: zac.lewis@dpi.vic.gov.au