ALONG the mountain fed Jamieson River, and in spots along the Queens Creek (part of the water shed from the King River, just near Cheshunt) a group of dedicated trout enthusiasts are quietly going about the rejuvenation of wild trout stocks in the state’s waterways.
Matt Byrne, president of the Mansfield and District Fly Fishing Club, was inspired after a trip to America and witnessing the revolutionary effects the Jordan/Scotty Fish Egg Incubator was having on wild trout breeding programs in the country.
Up until the invention of the Jordan/Scotty Incubator, disease was the primary cause of mortality in hatchery-harvested eggs.
“In-stream incubators are not a new thing,” Graham Godber, secretary of the Mansfield and District Fly Fishing Club, said.
“The problem though is that once you get a disease like White Spot for instance in the ova it spreads.
“Any egg that is in contact with it gets it straight away, and before you know it the whole incubator and all the eggs are infected.
“The transmission rate is so high, that in no time the disease can go right through a whole hatchery.
“For decades it’s been a problem in raising trout and other fish as well in hatcheries.”
To combat this problem, commercial hatcheries are constantly monitoring for disease and batches of eggs are segregated in numerous containers in order to isolate outbreaks.
The revolutionary design of the Jordan/Scotty Incubator takes this segregation one step further, by separating each and every egg in a plastic honeycomb configuration.
Within the incubator there are five cells with 200 eggs to each cell.
The individual cells are then fixed together accounting for 1000 eggs and then the incubator is placed in-stream.
“The beauty of the device is that any disease is only confined to the infected egg and it is not transmissible due to its isolation,” Mr Godber said.
“Though a game changer it is quite labour intensive to load up the incubator, and at this stage commercial hatcheries couldn’t really do it as a viable alternative.
“It does require the assistance of a number of volunteers, and that’s where we come in.
“It was the Australian Trout Foundation (ATF) that approached the Victorian Fisheries Authority (VFA) through their principal hatchery at Snobs Creek, and suggested experimental trials of the Jordan/Scotty incubators in nominated streams, offering their assistance for the project.”
A member of the Australian Trout Foundation, the Mansfield and District Fly Fishing Club (MADFFC) is proactive in implementing the foundation’s goals.
A spokesbody for enthusiasts, clubs and fishermen in Victoria, the Australian Trout Foundation is a non-profit organisation which is dedicated to the recovery, development and ongoing management of wild trout in Victoria, and all over Australia.
Working alongside the VFA and the ATF the MADFFC has assisted in these trials placing the incubators in local streams.
The results have been so promising that the initial three year trial – now completed – has been extended for another three years until 2022, with locations along the Upper Goulburn River and further tributaries along the King River also under consideration, with further trials to take place in the Dargo River in central Gippsland.
With attrition rates incredibly high among wild-spawned fish, with predation and extremes in water flow, temperature and climatic conditions all contributing to their demise, only between five and 20 per cent of wild ovum hatch in the first place.
With a low survival rate from such a small percentage of viable hatchlings, the recovery of wild trout in the streams and waterways of the region does require significant assistance.
Incubators guarantee a 90 to 95 per cent hatch rate, and the unique design of the Scotty/Jordan Incubator virtually eliminates most of the problems experienced by natural spawning.
Fungus infection is non-existent and the eggs are protected from predators and silt suffocation, and buried in the right gravel and area eggs can be raised from alevins, which are newly spawned trout still carrying the yolk, to fry while safely contained in the incubator cells.
With such positive results, the ultimate goal is to use wild trout ova in the incubators as opposed to ova from the Snobs Creek Hatchery to ensure the resilience of the supplemented trout in the waterways.
With hatchery progeny subject to loss of natural instinct and ability to breed in the wild, using predominantly hatchery-raised ova could result in breeding sterile fish.
“We need wild fish to survive in the wild,” Mr Godber said.
“But from our original position of starting with only 20 incubators to increasing the number to 50, and now extending the trial and incorporating new waterways into the experiment, I am sure we are well on our way to achieving our goal.”