August 2008 School of Environmental and Life Sciences University of Newcastle Status of populations of threatened stream frog species in the upper catchment of the Styx River on the New England Tablelands, near sites where trout releases occur. Year 2: establishing sites for the study of trout impacts on population demographics. Simon Clulow, John Clulow & Michael Mahony School of Environmental and Life Sciences, University of Newcastle Prepared For Recreational Freshwater Fishing Trust New South Wales Department of Primary Industries August 2008 Status of Populations of Threatened Stream Frogs in the New England Tablelands. August 2008 School of Environmental and Life Sciences University of Newcastle EXECUTIVE SUMMARY ................................................................................................ 1 1.0 INTRODUCTION ........................................................................................................ 1 1.1 Scope ......................................................................................................................... 1 1.2 Local Context ............................................................................................................ 3 1.3 Legislation and Licensing Requirements .................................................................. 3 1.4 Background to the Problem and Proposed Study ...................................................... 4 1.4.1 The Recent Decline of Amphibians in Australia ................................................ 4 1.4.2 The Implication of Introduced Trout in the Decline of Stream Frogs ................ 5 1.4.3 Addressing the Fisheries Management Strategy ................................................. 6 1.5 Project Objectives..................................................................................................... 6 1.6 Target Species Profiles ............................................................................................. 7 1.6.1 Glandular frog (Litoria subglandulosa) .............................................................. 7 1.6.2 Stuttering frog (Mixophyes balbus)..................................................................... 8 2.0 METHODS ................................................................................................................... 9 3.0 RESULTS ................................................................................................................... 15 3.1 Frog distributions along transects and a comparison of frog population densities between trout and control transects. .............................................................................. 15 3.2 Effects of trout on various measures of body condition and environmental stress . 19 3.3 The relationship between stream and riparian variables and frog distributions along stream transects.............................................................................................................. 21 4.0 DISCUSSION............................................................................................................. 26 5.0 CONCLUSIONS......................................................................................................... 27 6.0 RECOMMENDATIONS............................................................................................ 27 7.0 REFERENCES ........................................................................................................... 28 Status of Populations of Threatened Stream Frogs in the New England Tablelands. August 2008 School of Environmental and Life Sciences University of Newcastle EXECUTIVE SUMMARY The authors of this report were engaged to assess the status of populations of threatened stream frogs in and around the upper catchment of the Styx River on the New England Tablelands in areas where trout releases occur over the spring/summer periods of 2005/2006 and 2006/2007. The brief for this study required an assessment of the impact of introduced trout on these threatened frog populations in streams where trout have been released. The rationale for this study was the implication of trout in the decline of several Australian specialist stream breeding amphibian species in 1999 (Gillespie & Hero, 1999). The initial surveys of 2006 involved broad landscape scale surveys of the presence/absence of a number of threatened species that were known to be present in the New England Tablelands historically. In 2007, the studies were focussed on a smaller number of permanent transects that were established at 11 sites in the Styx River area to investigate more intensely potential impacts of trout on two endangered frogs: the Glandular Frog, Litoria subglandulosa and the Stuttering Frog, Mixophyes balbus. One year of demographic data from surveys in October and December 2007 was used to assess effects of trout on population densities and demographics, and the condition of adult frogs of these species as a measure of environmental stress. No effects of the presence of trout were demonstrated on any of the parameters used as potential measures of impact. Nevertheless, it is recognised that the power of the analysis was limited, since it was based on surveys during just one season. Consequently it is recommended that study sites continue to be surveyed during further years. The study also identified various habitat characteristics of the streams and riparian zones that may help identify stream systems where these species are present, and stream systems that may offer favourable habitat to be managed in the long term for the conservation of these species. 1.0 INTRODUCTION 1.1 Scope The authors of this report were engaged by the New South Wales Department of Primary Industries (Recreational Freshwater Fishing Trust) to undertake an assessment of the status of populations of threatened stream frogs in and around the upper catchment of the Styx River on the New England Tablelands in areas where trout releases occur. The purpose of this assessment was to provide an insight into the impact of the release of introduced trout species on the distribution and abundance of threatened stream dependent frogs. Status of Populations of Threatened Stream Frogs in the New England Tablelands. 1 August 2008 School of Environmental and Life Sciences University of Newcastle The first year of the study of the involved a wide ranging survey of streams in the Styx River Catchment area that were either trout release streams or streams in which trout were not released. Those surveys showed that two endangered species, the Glandular Frog (Litoria subglandulosa) and the Stuttering Frog (Mixophyes balbus) were distributed along streams where trout release occurs, as well as along streams where trout were not known to be released. Analysis of the data did not show a significant difference in the proportions of streams with populations of these frogs between trout release and non-trout release streams. Nevertheless, it was concluded in the report on that initial surveys (Clulow et al, August, 2006) that the presence of populations of these frog species in streams co-habited by trout did not necessarily indicate that trout had no negative impact on those threatened frog species. Rather, the study only indicated that trout were not associated with the elimination (local extinction) of the frogs from those streams. This was because the study was only able to determine the presence or absence of frog populations (due to the objective of surveying a large number of stream sites), but did not determine whether frog population size and density was reduced in the presence of trout. The report recommended that some longer term study sites be established to determine whether trout are associated with a decline in the population status of these frog species by comparing the population demographics of frog populations over time in streams with and without trout. Support from the Freshwater Fishing Trust was provided to continue that work into a second year, with the focus on assessing the demographics and status of these species in a smaller number of more intensively studied streams. The design of the field project is described in more detail in the Methods section. The benefit of continuing this study is the capacity to determine whether trout have a negative effect on populations of frogs they share stream habitats with. Knowing this will indicate whether there might be long term, incremental effects leading possibly to loss of threatened stream frogs in the long term, or whether alternatively trout and threatened stream frogs may persist indefinitely together in the same stream systems. The outcome should be improved management of both the endangered frog species on the New England Tablelands and the trout fisheries of the region. Status of Populations of Threatened Stream Frogs in the New England Tablelands. 2 August 2008 School of Environmental and Life Sciences University of Newcastle 1.2 Local Context The study area is located in north-eastern NSW on the New England Tablelands and is situated between Coffs Harbour to the east, Armidale to the west, Grafton to the north and Kempsey to the south (see Figure 1). The region is associated with large areas of National Park, State Forest and freehold rural lands. The landscape is characterised by numerous creeks, streams and rivers, numbers of which are utilised for stocking with introduced trout. The vegetation and landscape throughout the study area varies greatly with rural townships, cleared land (generally utilised for farming), and natural