Growth, population dynamics and morphometrics of Pinna bicolor (Gmelin, 1971) in Lake Macquarie, New South Wales, Australia

Anecdotal reports suggest that populations of razor clams, Pinna bicolor, have increased substantially in Lake Macquarie, New South Wales over the last 5-10 years. This has raised concerns about the ecology of the Lake and human safety. As a first step to providing information to inform management, between August 2009 and August 2010, we examined growth, population density, recruitment and the morphometrics of marked razor clams in a permanently marked grid in the southern reaches of the Lake. Growth increments of 61 P. bicolor were used to construct a Ford-Walford plot, from which von Bertalanffy growth parameters were calculated (K = 0.409 and L_∞ (dorso-ventral measurement) = 235.192 mm). During the study period 24 P. bicolor recruited to the grid, increasing the population density from 0.15 m^-2 to 0.20 m^-2. Recruits ranged in size (antero-posterior measurement) from 177–241 mm, with a mean (± SE) of 215.4 ± 4.1 mm. Morphological variation was observed and was evident within the linear regression of shell length on shell height (r² = 0.631). These observations confirmed that growth, density and recruitment, as well as the degree of morphological variation within a population of P. bicolor in the warm temperate waters of New South Wales, is similar to that recorded for populations in South Australia and Western Australia.