Key words: population models, native fish, Murray-Darling Basin, Native Fish Strategy
Threats and Impacts: Native fish of the Murray-Darling Basin (MDB) have experienced severe contractions since European settlement. Gaining greater insight into the population dynamics of native fishes is critical for long-term conservation. Population models play an important role in identifying underlying factors that may affect population structure and the persistence of species.
Broad aim and specific objectives: This study aimed to assess the potential development of population models for priority species in the MDB and provide an indication of the use of these types of models in natural resource management.
An initial review of the available literature was undertaken to assess the degree to which populations models developed for Australian freshwater fishes have been adopted to inform decision making by managers or guide data collection and research directions.
A survey was undertaken of fish and fishery managers to identify species of interest. A further survey of managers and researchers provided information on data availability for these species. For each species of interest, a life cycle model was developed to help identify the data required to develop a population model. This process, in conjunction with the information gathered from mangers and researchers and information already available in the literature, identified key knowledge gaps to help guide future research and data acquisition for developing a deeper understanding of population dynamics.
Findings: A review of population models in natural resource management raised a number of concerns in relation to the ability to get appropriate information from the primary literature. The review did also find good examples of where population models have integrated into management and policy, mainly in a fishery context. There are some examples where models have influenced management and policy development in freshwater research such as the trout cod model. Although the review found there was strong interest in the development of models, there needs to be a concerted effort from all interested parties to ensure models are used to influence policy and management outcomes and utilised by the intended stakeholders.
This study also surveyed a number of fish and fishery managers in the Murray-Darling Basin to establish a list of fish species of most concern. Twenty five species were recorded as of most concern and these were scored for priority. A further survey of scientists and managers was conducted to assess data availability that could be used in a model similar to that developed for Murray Cod (Maccullochella peelii). Of the twenty five species reviewed, there was sufficient life cycle information to construct an age population model and data that could be used to estimate the parameters required for an age structured model for eight species (in order of concern with rank number): Silver Perch (Bidyanus bidyanus) (1st); Macquarie Perch (Macquaria australasica) (2nd); Trout Cod (Maccullochella macquariensis) (4th); Murray Hardyhead (Craterocephalus fluviatilis) (6th); Golden Perch (Macquaria ambigua) (7th); Two-spined Blackfish (Gadopsis bispinosus) (14th); Carp (Cyprinus carpio) (17th); Brown Trout (Salmo trutta) (23th); and while no data was held in Australia for Rainbow Trout (Oncorynchus mykiss) (12th), sufficient data is available in the international literature to estimate the required parameters for an age based population model. As a priority, it was recommended that models be developed for the five species ranked in the top 10 of species of most concern: Silver Perch, Macquarie Perch, Trout Cod, Murray Hardyhead and Golden Perch.
It was also recommended that research be undertaken on the five other species of concern in the top 10, for which there is insufficient information to construct a model, to improve knowledge and/or data to the model development level and consider model development for these species.
Figure 1 – Silver Perch was identified as a species for which a population model could be developed, and would be valuable. (Photo courtesy of Jamin Forbes)
Figure 2 – This study highlighted value of using data on Trout Cod to inform an age structured population model. (Photo courtesy of Jamin Forbes)
Lessons learned and future directions: The study has highlighted a short list of native species, which as a priority require population modelling to provide better guidance for future management actions (Figs 1 and 2). Better-targeted management actions will provide increased benefits for native fish populations on a benefit per resource basis. The highlighted species where insufficient data is available to construct population models provide researchers with a shortlist of priority research questions and should better focus attempts at filling knowledge gaps for native fish species of the MDB.
Stakeholders and Funding bodies: This project was funded through the Murray-Darling Basin Authority’s Native Fish Strategy.
Contact: Dr. Charles Todd, Arthur Rylah Institute, (02) 60519920, Charles.Todd@depi.vic.gov.au, 23 Brown St, Heidelberg, Victoria, Australia, +61 3 9450 8600.
EMR Project Summaries 