AbstractGiven that conservation introductions are essentially biological invasions, researching the main factors which influence them will provide insight for both conservation and management. The factors affecting invasion success in small-bodied Australian freshwater fishes are largely unstudied. From a conservation-oriented perspective this is worrying as small-bodied freshwater species are more likely to become threatened than large-bodied species. It is equally concerning from an invasive species management perspective as many species have the potential to negatively impact native species and ecosystems. This thesis consists of two data chapters preceded by a general introduction and followed by a synthesis.
The first data chapter examines potential pre and post zygotic barriers to hybridisation between the Running River rainbowfish (RRR) and eastern rainbowfish (Melanotaenia splendida). Eastern rainbowfish is a widespread native fish of northern Australia with an alien population in Running River (a tributary of the Burdekin River, Queensland). Hybridisation between RRR and eastern rainbowfish has been detected and in the absence of barriers to further hybridisation and introgression will likely lead to the loss of pure RRR from the wild. Dichotomous mate choice experiments and egg survival experiments were used to determine the presences of pre and post-zygotic barriers to hybridisation between RRR and eastern rainbowfish. The findings of this study do not support the presence of barriers to hybridisation between the two species. Mate choice experiments suggested that males and females of both species examined did not exhibit preferential mate choice, which is most unusual. Similarly, egg survival experiments found no differences in fertility or reproductive success between hybrid and pure crosses. The chapter is presented as a stand-alone article and has been accepted for publication by the journal Ethology.
The second data chapter focuses on conservation introductions conducted for RRR into refuge habitats free of eastern rainbowfish. Releases made into one of these release sites (Deception Creek) were used to examine the impact of predator avoidance training on the survival of captive bred RRR after release. Deception Creek received approximately 2500 fish while Puzzle Creek received approximately 1500 fish. RRR bred for release into Deception Creek exposed to a novel predator found within the release sites (spangled perch, Leipotherapon unicolor) using repeated controlled exposures prior to release. Experiments regarding predator training were ended prematurely due to unexpected weather conditions. This reduced the number of replicates and prevented any reliable statistical analysis of collected data. However, analysis of collected data suggested there was no difference between the survival of trained and untrained fish. Despite this, anecdotal observations suggest that pre-exposure to predators may have some beneficial effects on the survival of captive fish. This chapter also discusses movement data gained from these releases, something which is lacking for most native small-bodied fish species. This chapter is presented as a stand-alone article that will form part of a larger publication covering the discovery, description and conservation of RRR.
|Date of Award
|Peter Unmack (Supervisor) & Mark Lintermans (Supervisor)