Life history traits and conservation actions for the Maugean skate (Zearaja maugeana), an endangered species occupying an anthropogenically impacted estuary

The Maugean skate, Zearaja maugeana, is endemic to two isolated western Tasmanian (Australia) estuaries. The species' persistence in one of these estuaries (Bathurst Harbour) is uncertain, while the other estuary (Macquarie Harbour), potentially the remaining stronghold for the species, is an anthropogenically impacted system. Key life-history parameters were studied to inform conservation actions for this species. Reproductive information was obtained using non-lethal methodologies, circulating concentrations of sex steroids and ultrasonography. Growth and age parameters were estimated based on vertebral sections from a small sample of individuals. Females and males reached 870 and 760 mm total length, respectively. The species reached a maximum age of at least 10 years. Females and males attained 50% sexual maturity at 665 and 633 mm total length, respectively, probably maturing somewhere between four and six years of age. Females displayed an asynchronous, discontinuous reproductive cycle, being able to reproduce throughout the year, with a probable decline in reproductive activity during summer. No egg cases were observed in-utero. Males produce sperm all year round, with a peak in testosterone production during spring-autumn. Conservation strategies for Z. maugeana will need to focus on reducing anthropogenic impacts on the environmental health, the primary impacts being altered river flows associated with the production of hydroelectricity and increased nutrient load associated with salmonid aquaculture. There is a need to better understand how reproductive success, egg survival and recruitment are affected by these environmental challenges if the future well-being of this species is to be secured.

Automated summary

The endemic Maugean skate in western Tasmania, Australia, faces uncertainties in its main habitats due to anthropogenic impacts. Key life-history parameters such as reproductive information and growth were studied to inform conservation actions. Conservation strategies should focus on reducing human impacts on the environment, particularly river flows and nutrient load associated with hydroelectricity production and salmonid aquaculture to secure the future well-being of this species.