Australian diadromous fishes - challenges and solutions for understanding migrations in the 21st century
Diadromous fishes are a frequent but poorly understood component of coastal riverine fish communities in Australia. There are ∼33 diadromous fishes found in Australian waters, mainly catadromous and amphidromous species. An extensive review of the literature identified major information gaps about the lifecycles and ecology of many of these species, with information on facultative diadromy, navigation, marine and early life stages being particularly limited. In many cases, this lack of information has led to poor management decisions and consequently many of the Australian diadromous species are under increasing threat from a range of environmental impacts. Much of the required information is difficult to obtain with traditional field surveys and, as a result, new and improved research tools and technologies, including telemetry, otolith chemistry, stable-isotope analysis (SIA) and functional magnetic resonance imaging (fMRI) are increasingly being applied. Key areas for research on Australian diadromous fishes should involve: (1) use of telemetry and otolith chemistry to determine the level of facultative diadromy and variation in diadromous movements across a species range; (2) use of otolith chemistry and SIA to gain a greater understanding of larval and juvenile marine life stages of catadromous and amphidromous species; and (3) use of fMRI or traditional techniques such as electroolfactogram (EOG) to determine the role of olfaction in spawning and migration, and the impact of impoundments and agricultural run-off on these critical life history stages.