Department of Fisheries’ scientists have ruled out disease as the cause of large fish kills on the South Coast of Western Australia last month.
Pathology tests on samples, gathered by Albany-based Fisheries and Marine officers in late May, have not detected anything to suggest the stranding of hundreds of slender sunfish along numerous beaches was anything else than a natural phenomenon.
Department of Fisheries Senior Fish Pathologist Dr Brian Jones said research on similar occurrences in past years had shown the stranding often occurred when a strong Leeuwin Current carried the tropical and sub-tropical species into waters off the South Coast.
“As suspected, these events are an unfortunate natural occurrence, but it is important that we investigate all fish kills to rule out any other risks in the marine environment,” Dr Jones said.
“There is some body of opinion that suggests the slender sunfish get trapped close to shore and cannot function well in the colder South Coast waters. We don’t know much about the life cycle or biological characteristics of this species and previous research has not been able to determine whether the stranding events are seasonal or less frequent.
“We do know that slender sunfish occur worldwide in tropical and temperate marine environments. Researchers have found it to be a relatively fast swimming species, despite its lack of a true tail. It can grow to around 90 centimetres in length.”
Dr Jones said it was important for people to report all fish kills, whether natural occurrences or not, because they represented a potential health hazard – especially mass stranding events, where there was a lot of rotting fish on a beach.
“A fish kill should ideally be reported as soon as possible,” he said.
“Members of the public are urged to call our FISHWATCH service on 1800 815 507. From there we can deploy staff to get samples for testing.
“Not only will an early report help in identifying a cause, we can also get a warning out to the community because dead fish decay quickly, water quality changes quickly and contaminated water could potentially flow elsewhere.”
“The Department of Fisheries also responds to fish kills, as part of WA’s border surveillance, checking for the arrival of serious exotic diseases that could threaten our State’s wildlife.”