Bioenergetics of blue swimmer crab (Portunus armatus) to inform estimation of release density for stock enhancement

Stock enhancement is a contemporary management method employed to support fisheries productivity. Blue swimmer crab (Portunus armatus) is a widely distributed species that has been identified as a candidate for stock enhancement; however, the release strategy and ecological impact of releases have not yet been assessed. Here, we (1) quantify the bioenergetics of blue swimmer crab, (2) estimate consumption rates, and (3) develop these relationships in a stocking model to assess appropriate release densities and associated trophic impacts. Static respirometry was used to measure the resting metabolic rate (RMR) of blue swimmer crab at three temperatures (19, 24, and 29°C). RMR was found to increase with temperature (Q10=2.32), and was 73% higher when crabs were at a premoult or moulting stage. Parameters derived from respirometry experiments were applied to estimate blue swimmer crab stocking density in a south-eastern Australian estuary, by adapting an existing production-based simulation model. The model estimated a median stocking density of ~1.2 crabs per 100m2. A sensitivity analysis showed that the growth rate was the most influential parameter in this model, showing the importance of this parameter when assessing stocking scenarios.