Status

Venus Clam
Venerupis largillierti

2022/23 Venus Clam Status

In the Northern Zone, only 24.3 t of the 46.3 t TACC was landed in 2015 and CPUE fell to 27 kg per hour – the lowest rate since records began. This was a fall from 39.9 t catch and 64 kg/hour CPUE in 2014. The two Georges Bay northern zone licensees took a voluntary reduction in TACC to 3 t in response to the declining biomass. Surveys in 2017 and 2018 identified large numbers of pre-recruits (24 – 40 mm). However, a survey in 2022 estimated a total biomass of 10 t of which an estimated 83% (8.4 t) of the biomass was above the legal-size limit of 40 mm. This is a further decline of biomass and little evidence of recruitment into the fishery.

The decline in biomass can be attributed to ecological change in the estuary; recent harvest volumes in this fishery have been low. Observed changes include a doubling of native oyster (O. angasi) biomass between 2016 (4.7kg/m²; Jones and Gardner, 2016) and 2021 (10.0 m²; Keane, 2021), as well as increase in seagrass densities, over key Venus Clam beds. If high abundances of native oyster and seagrass persist in the estuary, there will be continued negative pressure on Venus Clam stocks.

The stock extends beyond the boundaries of the beds so the fishery biomass is less than the total biomass of clams in Georges Bay. The current low biomass combined with declines in CPUE since 2015 provides evidence that the stock is at an historical low level. Fishing has been low with less than 5% of the estimated biomass taken as catch since 2017. Less than 14% of the TACC has been harvested since 2020. This is evidence that the stock has not been reduced by excess fishing mortality. Rather, increases in Native Oyster biomass and Seagrass appear to be putting significant negative pressure on Clam stocks. Adequate management measures are in place for the fishery but are not resulting in measurable improvements due to environmental influences. Based on this the Stock Status is classed as Depleted.