Competition between wild and captive-bred Penaeus plebejus and implications for stock enhancement

Abstract

The mechanisms that drive density dependence are rarely studied in the applied context of population management. We examined the potential for competition for food and shelter and the resulting demographic density dependence to influence how well populations of the eastern king prawn Penaeus plebejus Hess can recover following marine stock enhancement programmes in which captive-bred juveniles are released into the wild. Specifically, manipulative laboratory experiments were used to quantify the differential effects of competition for food and competition for shelter on survival of wild and captive-bred P. plebejus as densities were increased and as each category of P. plebejus (wild or captive-bred) was supplemented with the alternate category. Increasing population densities when food and shelter were limited lowered survival for both categories. When food was limited, survival of both categories was unaffected by addition of the alternative category. Adding wild P. plebejus to their captive-bred counterparts when shelter was limited under laboratory conditions resulted in significantly higher mortality in captive-bred individuals. In contrast, adding captive-bred P. plebejus to wild individuals under these conditions did not affect wild P. plebejus. We conclude that if the current results can be extended to wild conditions, competition for shelter may lead to the loss of captive-bred P. plebejus, thereby reducing the intended outcomes of stock enhancement. This highlights the importance of investigating interactions between wild and captive-bred animals prior to stock enhancement to predict long-term outcomes and identify situations where stock enhancement could be an effective response to the loss of populations or recruitment limitation.

Dispersal of Eastern King Prawn larvae in a western boundary current: New insights from particle tracking

“…Hatchery releases of EKP post-larvae are currently used to enhance recreational harvest in areas where recruitment is limited (Ochwada-Doyle, Gray, Loneragan, Suthers, & Taylor, 2012;Taylor, 2017). The ability to understand expected recruitment to the southern part of the range and connectivity with spawning in the north may improve enhancement strategies of when and where to release larvae (Loneragan, Jenkins, & Taylor, 2013), and also assist the management of effort in the northern part of the range where adults are targeted by offshore trawling.…”

A tool for tracking genetic contributions of wild Penaeus (Melicertus) plebejus broodstock to hatchery populations

“…Ochwada‐Doyle et al . () had shown wild P. plebejus PL outcompete hatchery‐reared individuals, which has the potential to contribute to the loss of the released P. plebejus where there is an existing population. This may negatively impact the outcomes of a stocking programme as a whole.…”

Marine Stock Enhancement, Restocking, and Sea Ranching in Australia: Future Directions and a Synthesis of Two Decades of Research and Development

“…Experimental ecology was used to show that eastern king prawn post-larvae actively selected structured aquatic macrophyte habitat after release (Ochwada et al, 2009), where their survival from certain predators was higher than on bare substratum (Ochwada-Doyle et al, 2010). In addition, wild eastern king prawns out-competed stocked prawns for shelter from predators within structured habitat, such as macrophyte beds, but wild and stocked prawns had equal competitive abilities for food within these habitats (Ochwada-Doyle et al, 2012). Prawns were released at low densities relative to other prawn releases (<5 prawns per square meter; Bell et al, 2005), and the three stocking events resulted in substantial recreational harvest (Taylor, unpublished data).…”