This month focuses on spangled perch Leiopotherapon unicolor
Spangled perch is a hardy and tolerant species considered to be the most widely distributed freshwater fish in Australia, ocurring across much of northern Australia, including the western and northern Murray-Darling Basin (MDB). It lives for 2-4 years and achieves a maximum size of 33cm, reaching maturity within its first year. The species is considered an extremer disperser (at rates of least 9.4 km/day, and hundreds of kilometres at a time) which occurs across a broad range of habitats, including flowing rivers, lakes, wetlands and temporarily flooded areas.
Given its ‘can do’ attitude, it is perhaps surprising that the species rarely moves downstream into the southern MDB – with only four records below Menindee Lakes prior to 2010 – which is attributed to its inability to tolerate the relatively cool winter water temperatures. However I recently co-authored a paper focusing on the flood dispersal and short-term persistence of the species in the southern MDB following flooding over late 2010 and early 2011. The paper is the first to document (i) rapid (first Murray River record in October 2010, noting first rains in northern MDB only started in late August of that year) and widespread dispersal (1300 records from over 65 locations), (ii) persistence beyond a single winter, and (iii) recruitment by the species in the southern MDB. We pose the question about whether these observations outside the core range of the species are normal, but previously undocumented, or whether they represent the early signs of the southern range expansion of the species (and potentially other tropical species)?
More info, see Ellis I, Whiterod NS, Linklater D, Bogenhuber D, Brown P, Gilligan D (2015). Spangled perch (Leiopotherapon unicolor) in the southern Murray–Darling Basin: flood dispersal and short term persistence outside its core range. Austral Ecology, Early View.
Interesting fact: some people (wrongly) believe the species disperses to newly indundated areas (with seamingly no aquatic connection) as the result of a ‘rain of fish’ – however, this reputation is simply due to its remarkable ability to move overland in very shallow temporary surface water (even flooded wheel ruts on some occasions). If you don’t believe me see the recent NT News article (which features Aquasave’s very own Michael Hammer) highlighting this dispersal ability here.