The imminent closure of the commercial gillnet fishery within the Great Barrier Reef World Heritage Area has led to trials of alternative, low-impact fishing gear, such as trap-nets. Initial testing of trap-nets has been promising, with low TEPS interaction rates and apparent healthy releases. However, a critical question remains unanswered: do fish released from trap-nets actually survive? Answering this question non-lethally, rapidly and in the field is a defining challenge of applied conservation physiology, and one this project directly addresses.
In this study we characterised the physiological stress response of three commercially and recreationally important teleosts – barramundi (Lates calcarifer), barred javelin (Pomadasys kaakan) and silver javelin (Pomadasys argenteus) – captured using trap-nets, gillnets, and line. Following capture, blood was drawn as soon as possible and analysed using point-of-care devices for key stress indicators including whole-blood glucose, lactate, ketones, haematocrit and haemoglobin. Capture and handling variables were recorded for each individual to disentangle gear effects from handling stress.
Comparisons between these biomarker profiles have then been used to characterise the stress response associated with each capture method, providing a proxy for expected post-release survival outcomes of undersized discards. This research will help provide an evidence-based evaluation on the physiological effects of trap-nets, further investigating their potential as a low-impact alternative to gillnets within Queensland’s inshore fishery. More broadly, it offers a practical model for how non-lethal physiological monitoring can help inform evidence-based fisheries management decisions.