8 minute read
Breeding Salmon for the Future
–Selectively bred salmon undergoing gill checks –
The history of selectively breeding salmon in Tasmania goes back to 2002 when Huon first mass-selected salmon that showed a natural resistance to amoebic gill disease (AGD).
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These broodstock were carefully selected as clear fish for AGD from a pen that had been left unbathed for a period ensuring that there was a clear difference between infected and more resistant fish. Their progeny was put to sea the following year and required 1–2 fewer baths during their lifecycle.
–“AGD is caused by single-celled amoeba, which are native to Tasmania, settling on salmon’s gills. If left untreated, water and oxygen flow can be restricted and may result in salmon dying from asphyxia. The treatment for amoeba is to bathe them in freshwater aboard our wellboat.” –
David Mitchell, Huon’s Freshwater Manager said that the early results were clear evidence that selective breeding for amoeba resistance had potential.
“To get a second generation of brood stock, we again selected the best performing individuals which hadn’t been bathed ensuring that the AGD resistance trait was strong,” said David.
“We continued with this basic mass selection until 2006 when a familybased breeding program was set up in collaboration with the other major industry players and the Commonwealth Scientific and Industrial Research Organisation (CSIRO). Advice was canvassed from overseas and Dr Dick Alderson (who had set up the Marine Harvest breeding program in Scotland) was employed to produce the original guidelines, which included incorporating safeguards to
prevent any risk of in-breeding occurring in the program. It has directly resulted in a high performing stock that is adapted to local farming conditions in Tasmania.”
Today, the program is run through the SALTAS hatcheries at Wayatinah and Florentine, and has developed broodstock that perform well in key areas going on to produce the next generation of salmon. Primary desirable traits focus on better growth and increased amoeba resistance and also incorporating selection for later sexual maturation and improved flesh quality including flesh colour and lipid levels.
“Since the founder populations were recruited in 2004, 2005 and 2006, there has been a steady increase in genetic gain where growth potential and amoeba resistance have improved by roughly two to three per cent a year as measured in two standard indicator pens, one at Huon and one at Tassal. These gains are as good as any other salmon breeding program worldwide.”
“Initial results from the family-based program replicated those seen from the earlier mass selection in that amoeba resistance is a heritable trait and can be increased through the generations. This means that there are direct operational benefits each year.”
–“Selective breeding is something that all sectors of agriculture undertake whether it is breeding strains of drought-resistant wheat, to cattle that produce less methane—it is a very common practice.” –
Approximately 200 families of salmon are in the program each year and each company has rights to a percentage of these based on their financial shareholding in the program.
“These fish are individually tagged and reared in a cage at Hideaway Bay by Adrian Steenholdt and his team with fish performance measured in a changing “real world” environment including climate change. This means we breed from the fish that are best able to perform in these changing conditions. This family and individual performance information gained at sea then informs us which are the best individuals and families to breed from.
–A selectively bred Huon Salmon –
–“We select the top 10 performing families to produce the production broodstock. These are called the “Elites” and they are selected by ranking the families for a combination of their most desirable traits.” –
The next step in the breeding program is a move towards genotyping each salmon, this technology allows us to select the best performing fish from within the top 10 families.
“CSIRO have been developing SNP chip technology for use in livestock breeding programs and have transferred these principles to salmon. This allows each fish’s genes to be coded and the code compared to sequences that we know indicate the traits that we are selecting for.”
–“SNP chip technology allows genes to be mapped and analysed to determine an individual fish’s genetic strengths.” –
The 2019 program has already used this technology to assess which males were the best to use.
“We have been focusing this selection on the males first as each male can fertilise a lot of eggs (from 200–450,000) and pass on his traits to a lot of offspring. From next year, the program will also start using this technology on our females as well to further increase gains.”
“This gives us the potential to tailor specific traits for different stocks which will further enhance the quality of our stock year-on-year which is a very exciting prospect,” finished David.
–Aerial views of the Bridport Hatchery –
Tasmania’s first commercial trout farm, located in Bridport, recently celebrated 55 years of operation. The Bridport farm was established by Alec H Purves in the 1960s. Alec got his start in trout farming overseas where he studied and worked for an American company. He bought this knowledge back to Tasmania and lobbied the government to allow trout farming.
–“In 1963, the Tasmanian Government passed legislation to allow commercial trout farming and Sevrup Fisheries was granted a license in 1964— in no small part due to Alec’s efforts.” – In 1991, the Bridport site was sold to Simon Pitney, Huon’s Project Manager, and two others. Simon worked very closely with Alec as his mentee, and this knowledge was the foundation of Huon’s trout farming operation. Duncan Joyce, Huon Aquaculture’s Bridport Hatchery Manger, undertakes operations at the site with its history in mind. “Sevrup Fisheries were pioneers of trout farming and achieved a great deal with the technologies available to them. We are proud of the site’s long history and my team and I carry this in mind when we go about our operations today.” While the site is in the same place as the original farm, significant upgrades have been made by Simon and Duncan’s teams. “We have essentially overhauled the site to bring it up to something that works in the way that we wanted it to.” These updates include replacing the original steel pipeline that came from a tin mine in Derby.
–“We have black and white photos of the pipe being laid so seeing it upgraded, while a necessity, did bring with it a tinge of sadness.” –
–Guest-of-honour Alison Purves toasting the recent 55th birthday celebration ––The original steel pipeline –
Duncan said while the site is small, it is really efficient and packs a punch.
“We only do small numbers of stock, but because of the volumes and the upgrades, we are producing our biggest and best fish. Last year we smashed our previous trout weight record and had fish going to sea in March that weighed in at over 530grams!”
The hatchery employs five people which includes employees who have been kept on after completing training at the site.
“We had given some University students casual positions so they could get work experience while studying and they have been kept on after graduation which is great for us and the town.”
“It is a really good site for training and I’m very happy to have the opportunity to work with fantastic people on a site that is absolutely brimming with history,” finished Duncan.
Alec received an Order of Australia Medal in 2010 for pioneering fish farming in Tasmania.
–Huon Salmon in a RAS system –
A Pocket Guide to Huon’s Antibiotic Use
At Huon, we believe that disease control in salmon requires a holistic approach. Good site management, fish husbandry and rigorous biosecurity measures are central to reducing the risk of disease outbreaks and controlling the spread of infectious diseases.
While vaccines are important in preventing disease, they cannot control all losses. Medication such as antibiotics are also important but are only used as a last resort to avoid significant animal welfare issues and stock losses. This mind-set means that we are continually working to develop proactive diet regimes and vaccines to allow our salmon to combat known illnesses and lead healthy lives. Vaccination is now routine across all our stock.
Our vets also ensure that any use of antibiotics is undertaken in full accordance with the guidelines and recommendations of Australian Veterinary Association and World Health Organisation.
–“Huon employs two veterinarians whose responsibility it is to ensure that any antibiotic treatment is absolutely necessary. If our vets feel there is a need to treat with antibiotics then it is supervised, reported and strictly regulated by government.” –All antibiotic use is fully disclosed on our Sustainability Dashboard and Huon has not used any antibiotics at sea since 2016 when a single pen was treated. It should also be noted that Huon does not use any antibiotics in any of our recirculation (RAS) hatcheries, which is where most of our fish are now hatched and grown before they transfer to sea as smolt. Huon does however occasionally use small amounts of antibiotics at our flow-through hatchery sites which is voluntarily reported on our website.
–“Although antibiotic use is very low, it is important to note that the antibiotics when used, are allowed to pass through the fish long before it is harvested, in accordance with regulatory requirements.” – Huon also participates in an annual national residue survey to monitor levels of therapeutants, ensuring we comply with a maximum residue limit, which refers to the highest concentrations of a chemical residue that is legally permitted or accepted in a food, based on good agricultural and chemical use practices – www.agriculture. gov.au/ag-farm-food/food/nrs.
