Low flow – any fish?

Given the extremely low flows in the King Parrot Creek this summer/autumn, the question on many minds was: how would the native fish be coping – especially the endangered Macquarie Perch? Scientists from the Arthur Rylah Institute, supported by the Goulburn Broken Catchment Management Authority, recently completed their annual fish survey – and the results are actually quite a relief. Although total numbers of Macquarie Perch were down about 30% on last year’s high of 386, they were found in good numbers at all five sites and in a range of sizes from 50 to 337mm long. Macquarie Perch were the most abundant species representing 60% of all fish caught. The size range of juvenile Macquarie Perch captured showed there was strong recruitment in the 2013, 2014 and 2015 spring spawning periods. This recruitment pattern follows the results of other populations in the Goulburn Broken catchment and throughout Victoria.

There were also good numbers of other native fish including River Blackfish, Mountain Galaxias, Southern Pygmy Perch and Flat-headed Gudgeon. Brown Trout made up most of the introduced fish catch – one carp was caught at Richards Bridge and two Eastern Gambusia were also found there – the first time in the 10 years of surveying the King Parrot Creek. The by-catch also included 1 Platypus and 13 Snake-necked Turtles, all of which were released uninjured.

The surveys this year involved both fyke netting and electro-fishing. Caught fish were measured, weighed and inspected for external parasites and lesions before being released back into the creek. Macquarie Perch also had fin samples taken for genetic analysis and were checked for presence of previously installed tags – this year there were only 6 recaptured fish.

One parasite found on a few fish is Lernaea cyprinacea, commonly called Anchor Worm, although it is actually a copepod crustacean rather than a worm. It burrows into the fish’s flesh using horns on its head to anchor itself. It causes lethargy and may lead to death if embedded in a vital organ. The survey team carefully removed these 1cm long parasites with tweezers.

A worrying aspect highlighted in the report was the lack of connectivity in the stream caused by the construction of illegal rock weirs which represent a barrier to fish passage.