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Biological feasibility of spiny lobster Jasus edqardsii stock enhancement
thesisposted on 2023-05-27, 17:36 authored by Oliver, MD
The highly valued spiny lobster or southern rock lobster (Jasus edwardsil) found in South Australia, Tasmania and New Zealand presents a challenging candidate for aquaculture and stock enhancement efforts. Despite their gregarious nature and high survival in captivity, the protracted larval phase makes commercial-scale hatchery production of seed unfeasible. Therefore, the recently settled juvenile stage, or puerulus, must be trapped in the wild for on-growing in captivity. This puerulus harvest effectively increases exploitation and the conditions of harvest dictate that a proportion of juveniles must be returned to the wild after one year to maintain biological neutrality. Maintaining animals in captivity for lengthy periods, however, can disrupt behavioural development and contribute to high mortality after release into the wild. Research presented here investigates the influence captivity has on the pre- and post-release behaviour of juvenile spiny lobsters and how this may impact the success of reseeding efforts and the related goal of increasing productivity through stock enhancement. Juvenile lobsters reared in captivity without predators and fed by day displayed significantly higher levels of daytime activity than their wild counterparts. This behaviour could be manipulated with the addition of predators or night time feeding. Neither training method was necessary, however, because released lobsters resumed normal nocturnal activity and displayed appropriate anti-predator behaviour. Tethering experiments found predation was greatest in the first two hours after release and in the crepuscular period of the following morning. High predation was likely caused by the attraction of diverpositive fish species during release and high predator activity during crepuscular periods. Midnight observations of foraging distances and acoustic tracking over successive days, found that released lobsters moved similar distances to like-sized wild lobsters and recorded a strong association between den or area fidelity and the presence of conspecifics. Preliminary tank-based experiments to determine the potential for displacement of wild lobsters by released lobsters found that although released lobsters displayed a significant preference for crowding into the same dens as wild animals, disturbance of wild lobsters was minimal. Behavioural changes induced by on-growing in captivity do not appear to influence post-release behaviour or survival. Refined release protocols are likely to substantially reduce initial predation and increase site fidelity where there is an abundance of suitable habitat on contiguous reef. The overall conclusion is that reseeding to compensate for puerulus harvest should lead to enhancement of wild populations with concurrent investigation and improvement of release protocols.
Rights statementCopyright 2007 the author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. Wewould be pleased to hear from the copyright owner(s). Chapter 2 appears to be the equivalent of an accepted manuscript of an article published by Taylor & Francis in New Zealand journal of marine and freshwater research on 30 March 2010, available at: http://www.tandfonline.com/10.1080/00288330.2006.9517449 The published version, located in appendix 1 has been removed from the downloadable version. Chapter 3 appears to be the equivalent of an accepted manuscript of an article published by Taylor & Francis in Reviews in fisheries science on 10 October 2008, available at: https://doi.org/10.1080/10641260701727301 Chapter 4 appears to be the equivalent of an accepted manuscript of an article published by Taylor & Francis in New Zealand journal of marine and freshwater research on 29 March 2010, available at: http://www.tandfonline.com/10.1080/00288330.2005.9517320 The published version, located in appendix 1 has been removed from the downloadable version. Appendix 1 contains the following published article: Mills, D. J., Gardner, C., Oliver, M., 2005. Survival and movement of na‚àövòve juvenile spiny lobsters returned to the wild, Journal of experimental marine biology and ecology, 324(1), 20-30. Appendix 1 contains the following published article: Gardner, C., Frusher, S., Mills, D., Oliver, M., 2005. Simultaneous enhancement of rock lobster fisheries and provision of puerulus for aquaculture, Fisheries research, 80(1), 122-128.