Grey Nurse Shark Research
To establish assisted reproductive technology in grey nurse sharks in Australia
The grey nurse shark (also called sand tiger shark, Carcharias taurus) is currently listed under Australian Federal Government legislation as Critically Endangered on the east coast of Australia, with as few as 300–500 individuals remaining. In June 2002, Environment Australia adopted the Australian Species Recovery Plan for the Grey Nurse Shark. Under the Recovery Plan, Australian aquariums keeping grey nurse shark populations are prevented from collecting these sharks from the wild and instead must adopt breeding programmes aimed at maintaining ex situ populations.
Despite some successes in the past, breeding of grey nurse sharks in aquariums is sporadic, and conditions that work for one aquarium may not be transferable to another. Female grey nurse sharks have long reproductive cycles, including a 12-month gestation followed by a 12-month break before the next mating. The unique form of embryo/foetal nutrition in this species (oophagy with uterine cannibalism) results in only two pups produced for each pregnancy, a factor that contributes to their low replenishing rate in both the wild and captivity.
In January 2004, a collaborative research project was launched by UnderWater World and Melbourne Aquarium in partnership with the Monash Institute of Medical Research, and BHP Billiton. The project aimed to investigate reproduction in the grey nurse shark in aquariums, and to find ways to complement the existing breeding programmes for this species. Due to the endangered status of the grey nurse shark, two surrogate species, the broadnose sevengill shark (Notorynchus cepedianus) and the sparsely spotted stingaree (Urolophus paucimaculatus), have been used for the initial research and development of techniques. Research during 2004–2005 established the use of ultrasound to monitor reproductive cycles in the broadnose sevengill shark and began development of methods for sperm cryopreservation. At the end of 2005, the project was extended for a further three years to continue and expand the work developed during 2004–2005.
The project is now focusing on four main areas of research:
- Ultrasound of female grey nurse shark and broadnose sevengill sharks to follow the growth and regression of follicles in the ovary and detect pregnancy.
- Development of techniques for semen collection and artificial insemination in the broadnose sevengill shark and the grey nurse shark. This will potentially enhance breeding in aquariums by reducing the reliance on natural mating.
- Development of methods for cryopreservation of semen using samples collected from the grey nurse shark and the sparsely spotted stingaree. This will potentially enable long-term storage of semen from the grey nurse shark to help maintain genetic diversity in aquariums.
- Proteomics of seminal plasma from the sparsely spotted stingaree. Proteins have an important role in semen storage and fertilisation, but virtually nothing is known about seminal plasma proteins in elasmobranches.
The project, which is planned to continue until the end of 2008, should result in the development of assisted reproductive techniques that can be used to complement existing breeding and management programmes to ensure the maintenance of a viable ex situ reserve population for the grey nurse shark.
WAZA Conservation Project 06028 is implemented by UnderWater World and Melbourne Aquarium, and supported by the Zoo and Aquarium Association Australasia.
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