Creating techniques and technologies to improve aquaculture
In 1972, the famous marine ecologist Jacques Cousteau proclaimed that: “We must plant the sea and herd its animals using the sea as farmers instead of hunters. That is what civilization is all about – farming replacing hunting”. Forty plus years later, Cousteau’s prediction has been realised. Aquaculture has increased tenfold and is a major source of protein for humans.
With the rapid and recent rise of aquaculture, a range of environmental problems have emerged – pollution, disease, escapees and invasive species to name a few. Our lab works with aquaculture production systems at full-scale to create new and innovative ways to farm seafood with minimal impact upon the environment.
The lab works on many topics within sustainable aquaculture and fisheries, and more broadly in aquatic and terrestrial ecology. Within aquaculture, we try to solve the environmental and animal welfare problems aquaculture creates by working both inside and outside aquaculture systems.
- ecological effects of aquaculture on surrounding ecosystems
- fundamental aspect of fish welfare
- techniques and technologies to prevent parasite infection on farmed fish
- short and long term effects of parasite treatments on farmed fish
- preventing and reducing the effects of escaped fish in the wild
- understanding the nature and extent of critically low periods of dissolved oxygen in fish farms
- using macro-algae to mop up nutrients in coastal ecosystems
- sea urchin aquaculture
Marine, freshwater and terrestrial ecology
- preventing cane toad invasions
- effects of cane toads on freshwater crocodiles
- freshwater fishes of northern Australia
- sea turtle ecology
My research career began with larval fish ecology and biological oceanography before shifting towards the ecology of pelagic fish and the effects of fisheries during my PhD at the University of Sydney. During a post-doc at SINTEF Fisheries and Aquaculture, Norway, I began to research the ecological effects of aquaculture. My research interests have now converged to a common theme: basic ecological research, to ensure fishing, aquaculture and other anthropogenic practices are developed and conducted sustainably. While this theme has an applied angle, it draws strongly on fundamental principles of ecological theory.
Creating more disease resistant and productive stock for aquaculture
Fish products not only provide high-value protein but are also important sources of a wide range of essential micronutrients such as iron, zinc, and vitamins such as vitamin A. Many countries are struggling to provide enough food for their growing populations. Aquaculture is an efficient way of producing animal protein, can play an important role in reducing poverty and can alleviate pressures on wild fishery stocks. But expansion of aquaculture is often limited by a lack of knowledge about simple farming practices (including feed and feeding) and the availability of good genetic stocks. Areas available for aquaculture are limited, so we need to make the fish and production more efficient so that more of this healthy food source can be produced per unit area.
My research focuses on making fish and shellfish more productive for aquaculture by developing technologies that can be used to speed genetic improvement with selective breeding. My focus has been on improving the resilience of fish in the aquaculture environment, including:
- genomic selection for improving the disease resistance of rohu carp and tiger shrimp in India
- resilience to summer mortality for abalone in Australia
- design of selective breeding programs for barramundi, abalone and seaweeds
- epigenetic programming to produce robust Atlantic salmon for aquaculture in Norway
- genes associated with cardiovascular fitness (swimming performance) of Atlantic salmon in Norway
- assisting the development of aquaculture to alleviate poverty
- using the latest high throughput sequencing technologies and bioinformatics methodologies to better understand how particular genetic variants or changes in gene expression affect the resilience of fish
Sea urchin roe enhancement and tracing escapees from aquaculture
Aquaculture is the new frontier for the global expansion of fish production for human consumption. However, developing our oceans as a seafood buffet comes with environmental costs, for example the complex interactions between farmed and wild fish. During my PhD, I developed stable isotope marking methods to detect farmed fish in the wild and thus better assess their impacts. In my post-doc, I am researching sustainable roe enhancement of the sea urchin Heliocidaris erythrogramma using capture-based aquaculture
CURRENT PhD STUDENTS
Environmental transmission and connectivity of sea lice in marine ecosystems
Large-scale epidemics are affecting important marine species. For the most widely produced marine fish, salmon, parasitic ‘sea lice’ are the most significant problem. These external parasites cause major environmental and economic impacts. Understanding its epidemiology is crucial for management of infestations. I am investigating the environmental transmission of sea lice Lepeophtheirus salmonis in marine ecosystems with intensive salmon aquaculture. For this, I integrate empirical and modelling methodologies to dissect the processes involved in parasite dispersal and build connectivity models to design strategies to prevent lice outbreaks. My project will build fundamental knowledge on lice epidemiology and will allow informed management actions to minimize lice infestations on both farmed and wild salmonid populations.
Occurrence and implications of hypoxia in Atlantic salmon aquaculture
Despite declining capture fisheries, in 2014 world per capita fish supply reached a record high of 20 kg per year as a result of the rapid and steady expansion of aquaculture. The largest single aquaculture commodity by value is salmonids, representing 16.6% of world trade, with demand for Atlantic salmon steadily increasing. The industry, however, is constrained by environmental challenges. Hypoxia, which can occur naturally, is exacerbated in marine cages due to restricted water movement and locally increased biomass. Even apparently minor reductions in dissolved oxygen concentration can result in decreased growth, appetite, immune function and fish welfare. The aim of my project is to improve our understanding of the dynamics of dissolved oxygen fluctuation in salmon cage aquaculture so that managers can focus mitigation efforts and minimize risk as the industry continues to expand.
Tina is enrolled at UTas and co-supervised by Barbara Novak.
Linking habitat selection and fitness consequences in novel marine ecosystems
It is assumed that animals either choose the best available habitat or don’t choose at all. Despite this, there is evidence that almost all animals do make habitat selection decisions, and that they don’t always choose wisely. This is because rapid environmental change can outpace the evolution of decision-making tools, causing animals to prefer attractive but nonetheless unsuitable habitats (‘ecological traps’). I am studying several marine ecosystems altered by invasive species and aquaculture activities, to discover whether (a) native fauna are willing to inhabit these unfamiliar environments, and (b) whether these decisions are likely to lead to good fitness outcomes.
Bioremediation of nitrogen enriched aquatic environments by macroalgae.
Coastal activities that involve the discharge of nutrients can result in deleterious environmental impacts, with harmful effects on marine biodiversity. My thesis will focus on the potential uses of freshwater and marine macroalgae as bioremediation agents. The first part of the thesis will focus on sampling and testing of production and competition of local freshwater species and their ability to remove nutrients from wastewater. The second part will focus on the link between nutrient discharges and drift algal production and the environmental costs and benefits of algal drift harvesting for nutrient management.
CURRENT MSc STUDENTS
Hydrogen peroxide is a widely used agent in salmon aquaculture to remove parasites. However, some of the effects it can have in this host-parasite relationship are unclear. I will determine how varying concentrations of hydrogen peroxide treatment influence salmon mortality, pre-adult lice removal, salmon lice re-infection and the mucous cells of salmon. I will also try to create a new treatment method by reducing water temperatures during hydrogen peroxide treatments to minimise negative effects of the treatment upon fish. My results will be used by farmers to reduce salmon mortality.
PAST PhD AND MSc STUDENTS
Sea lice and amoebae causing amoebic gill disease are top parasites of Atlantic salmon, the most farmed marine fish. Their increasing co-occurrence in major production regions has sparked interest in parasite control techniques targeting both. Though, current reliance on treatments (mostly chemicals) leaves few options and drives treatment resistance evolution in parasite populations. This thesis explores the applicability of a more preventative and chemical-free approach to tackle multiple parasites: fish behaviour and cage environment manipulations.
Danny is now a pst-doc at the Institute of Marine Research, Noway.
The expansion of Atlantic salmon (Salmo salar) aquaculture systems has led to the success and proliferation of the ectoparasitic sea louse, Lepeophtheirus salmonis. Mediating infestation should have a biological basis, and this PhD investigates the fundamental behavioural interaction between host and parasite. It focuses on salmon behavioural defence and susceptibility, and effect of infestation on performance. Behaviour should be in the toolbox against pathogens in aquaculture, and this project has provided baseline knowledge of host-parasite interactions that will also help drive the development of biological tools.
Sam is now a post-doc at the Institue of Marine Research, Norway.
Aquaculture outputs and trophic subsidies: Trade-offs in consuming an anthropogenic resource.
Aquaculture is an increasingly common trophic subsidy in coastal marine ecosystems, with waste feed, faecal material and nitrogenous wastes potential food sources for marine consumers. As modern aquafeeds are increasingly high in terrestrial lipids and oils, the biochemical composition of the aquaculture-derived subsidy is relatively alien in the marine environment. Using terrestrial fatty acids as a tool, I investigated dispersal and uptake of the aquaculture subsidy, in both laboratory and field scenarios. I was able to demonstrate that aquaculture outputs are widely dispersed in marine systems and assimilated by marine consumers. Using marine amphipods and sea urchins as model species, I examined maternal and multi-generational effects of increased terrestrial lipids in the diet of marine consumers. I found that consuming waste could alter both biochemical composition and reproductive outputs in invertebrate fauna. When applied to a field scenario, where aquaculture outputs have been linked to increases in sea urchins, I found that broader-scale effects will be a trade-off between energetic benefits of consuming a lipid-rich subsidy, versus any negative effects that a high terrestrial diet may have on reproductive outcomes.
Camille is now a post-doc at the University of Tasmania.
The Kimberley freshwater fish fauna is the least studied in Australia; its true biodiversity and evolutionary history are unknown. The aim of my project is to assess the true freshwater fish biodiversity in the Kimberley using a combination of genetic and morphological approaches, and to investigate the influence of past and present geological and climatic processes on the evolution of these communities and their distributions.
James was a post-doc at the University of Melbourne writing a field guide to the freshwater fishes of the Kimberley, now he is a freshwater ecologist at NIWA, New Zealand.
Triple jeopardy in the tropics: assessing extinction risk in Australia’s freshwater biodiversity hotspot
Northern Australian is home to many poorly known, range-restricted and potentially vulnerable freshwater fishes. Species with small ranges, low abundances and narrow ecological niches have a ‘triple jeopardy’ extinction risk. I identify fishes with smaller ranges and lower abundances than expected across Australia. In the diverse, highly endemic Kimberley region, I investigate the dietary, habitat and physiological specialization of range-restricted fish. I show that northern Australia contains many potentially vulnerable species, with the Kimberley a hotspot of freshwater conservation concern.
Cassie completed her Master of Science in 2017 and is now a research assistant in the SALTT laboratory.
Tormey completed her Master of Science in 2015 and is now a fisheries technician at The Pacific States Marine Fisheries Commission.
Ella is now a PhD student at the University of Melbourne.
Cathy is now a PhD student at Monash University.
Kristal is now a PhD student at Deakin University.
Michael is now a PhD student at the University of Melbourne.
- Overton, K., Samsing, F., Oppedal, F., Stien, L. H., & Dempster, T. (2017). Lowering treatment temperature reduces salmon mortality: a new way to treat with hydrogen peroxide in aquaculture. Pest Management Science.
- Warren-Myers, F., Ingram, B. A., Dempster, T., & Swearer, S. E. (2017). Enriched stable isotope marking of hatchery trout via immersion: A method to monitor restocking success. Fisheries Research.
Bui, S., Oppedal, F., Samsing, F., & Dempster, T. (2017). Behaviour in Atlantic salmon confers protection against an ectoparasite. Journal of Zoology.
Bui, S., Dalvin, S., Dempster, T., Skulstad, O. F., Edvardsen, R. B., Wargelius, A., & Oppedal, F. (2017). Susceptibility, behaviour, and retention of the parasitic salmon louse (Lepeophtheirus salmonis) differ with Atlantic salmon population origin. Journal of Fish Diseases.
Oppedal, F., Samsing, F., Dempster, T., Wright, D. W., Bui, S., & Stien, L. H. (2017). Sea lice infestation levels decrease with deeper ‘snorkel’barriers in Atlantic salmon sea‐cages. Pest Management Science.
Sievers, M., Fitridge, I., Bui, S., & Dempster, T. (2017). To treat or not to treat: a quantitative review of the effect of biofouling and control methods in shellfish aquaculture to evaluate the necessity of removal. Biofouling, 1-13.
Wright, D. W., Nowak, B., Oppedal, F., Bridle, A., & Dempster, T. (2017). Free-living Neoparamoeba perurans depth distribution is mostly uniform in salmon cages, but reshaped by stratification and potentially extreme fish crowding. Aquaculture Environment Interactions, 9, 269-279.
Samsing, F., Johnsen, I., Dempster, T., Oppedal, F., & Treml, E. A. Network analysis reveals strong seasonality in the dispersal of a marine parasite and identifies areas for coordinated management. Landscape Ecology, 1-15.
Reimer, T., Dempster, T., Wargelius, A., Fjelldal, P. G., Hansen, T., Glover, K. A., … & Swearer, S. E. (2017). Rapid growth causes abnormal vaterite formation in farmed fish otoliths. Journal of Experimental Biology, 220(16), 2965-2969.
White, C. A., Nichols, P. D., Ross, D. J., & Dempster, T. (2017). Dispersal and assimilation of an aquaculture waste subsidy in a low productivity coastal environment. Marine Pollution Bulletin.
White, C. A., Bannister, R. J., Dworjanyn, S. A., Husa, V., Nichols, P. D., Kutti, T., & Dempster, T. (2017). Consumption of aquaculture waste affects the fatty acid metabolism of a benthic invertebrate. Science of The Total Environment, 586, 1170-1181.
Wright, D. W., Stien, L. H., Dempster, T., Vågseth, T., Nola, V., Fosseidengen, J. E., & Oppedal, F. (2017). ‘Snorkel’lice barrier technology reduced two co-occurring parasites, the salmon louse (Lepeophtheirus salmonis) and the amoebic gill disease causing agent (Neoparamoeba perurans), in commercial salmon sea-cages. Preventive Veterinary Medicine, 140, 97-105.
Oldham, T., Dempster, T., Fosse, J. O., & Oppedal, F. (2017). Oxygen gradients affect behaviour of caged Atlantic salmon Salmo salar. Aquaculture Environment Interactions, 9, 145-153.
Føre, M., Frank, K., Dempster, T., Alfredsen, J. A., & Høy, E. (2017). Biomonitoring using tagged sentinel fish and acoustic telemetry in commercial salmon aquaculture: A feasibility study. Aquacultural Engineering, 78, 163-172.
White, C. A., Dworjanyn, S. A., Nichols, P. D., Mos, B., & Dempster, T. (2016). Future aquafeeds may compromise reproductive fitness in a marine invertebrate. Marine environmental research, 122, 67-75.
- Bui, S., Oppedal, F., Stien, L., & Dempster, T. (2016). Sea lice infestation level alters salmon swimming depth in sea-cages. Aquaculture Environ
Bui, S., Dempster, T. D., Remen, M., & Oppedal, F. (2016). Effect of ectoparasite infestation density and life-history stages on the swimming performance of Atlantic salmon Salmo salar.
Dempster, T., Arechavala‐Lopez, P., Barrett, L. T., Fleming, I. A., Sanchez‐Jerez, P., & Uglem, I. (2016). Recapturing escaped fish from marine aquaculture is largely unsuccessful: alternatives to reduce the number of escapees in the wild. Reviews in Aquaculture.
Dempster, T., Wright, D., & Oppedal, F. (2016). Identifying the nature, extent and duration of critical production periods for Atlantic salmon in Macquarie Harbour, Tasmania, during summer. FRDC Project N, 2016-229.
Samsing, F., Johnsen, I., Stien, L. H., Oppedal, F., Albretsen, J., Asplin, L., & Dempster, T. (2016). Predicting the effectiveness of depth-based technologies to prevent salmon lice infection using a dispersal model. Preventive veterinary medicine, 129, 48-57.
Samsing, F., Oppedal, F., Dalvin, S., Johnsen, I., Vågseth, T., & Dempster, T. (2016). Salmon lice (Lepeophtheirus salmonis) development times, body size, and reproductive outputs follow universal models of temperature dependence. Canadian Journal of Fisheries and Aquatic Sciences, 73(12), 1841-1851.
Stien, L. H., Dempster, T., Bui, S., Glaropoulos, A., Fosseidengen, J. E., Wright, D. W., & Oppedal, F. (2016). ‘Snorkel’sea lice barrier technology reduces sea lice loads on harvest-sized Atlantic salmon with minimal welfare impacts. Aquaculture, 458, 29-37.
Reimer, T., Dempster, T., Warren-Myers, F., Jensen, A. J., & Swearer, S. E. (2016). High prevalence of vaterite in sagittal otoliths causes hearing impairment in farmed fish. Scientific reports, 6, 25249.
Wright, D. W., Oppedal, F., & Dempster, T. (2016). Early‐stage sea lice recruits on Atlantic salmon are freshwater sensitive. Journal of fish diseases, 39(10), 1179-1186.
Le Feuvre, M. C., Dempster, T., Shelley, J. J., & Swearer, S. E. (2016). Macroecological relationships reveal conservation hotspots and extinction‐prone species in Australia’s freshwater fishes. Global ecology and biogeography, 25(2), 176-186.
Sanchez-Jerez, P., Karakassis, I., Massa, F., Fezzardi, D., Aguilar-Manjarrez, J., Soto, D., … & Marino, G. (2016). Aquaculture’s struggle for space: the need for coastal spatial planning and the potential benefits of Allocated Zones for Aquaculture (AZAs) to avoid conflict and promote sustainability. Aquaculture Environment Interactions, 8, 41-54.
Making a delousing treatment more fish-friendly
A cure should never be worse than the disease. In modern aquaculture, unfortunately that’s not always the case. When chemical treatments for parasites go wrong, they go very wrong, and cause mass mortalities of hundreds of thousands of fish.
One very common treatment to control external parasites is hydrogen peroxide baths. For salmon, the treatment is extremely toxic at warmer temperatures and can lead to fish deaths.
Kathy Overton, a Melbourne University Masters student invented a new method to make hydrogen peroxide treatment more fish friendly. By switching fish from warm ocean temperatures to cold treatment baths, Kathy showed the treatment was just as effective against the parasites and no deaths occurred. Once the industry takes up the new method, millions fewer fish will suffer each year.
https://www.fishfarmingexpert.com/news/colder-water-eliminates-delousing-fish-deaths-in-lab/December 14, 2017 News
Urchin Aquaculture Australia
Introducing Urchin Aquaculture Australia – a collaboration between The University of Melbourne, Deakin University, Southern Cross University and industry partner, AquaTrophic.
Sea urchin roe (‘uni’) is a prized delicacy in countries such as China and Japan. Uni is a particularly high value product, with a large export market in Japan worth around US $200 million annually. Increasing demand and reduced supply from collapsing wild fisheries are creating opportunities for commercial sea urchin culture in Australia to supply the Japanese market.
The aim of our AgriFutures Australia-funded research is to target major bottlenecks in sea urchin aquaculture industry development. Our current research focuses on two commercially-valuable sea urchin species: the collector urchin (Tripneustes gratilla) and the purple urchin (Heliocidaris erythrogramma).
To learn more, head to www.urchin.org.au.October 19, 2017 News
Helping fish fight their own battles
A terrific article on the groundbreaking research of past PhD student Samantha Bui, which was recently published in the Journal of Zoology. Through a creative experiment, Sam and her colleagues worked out that fish have an inherent ability to use behaviour to deter parasites at the point of contact. Behaviour really is the first line of defence.
Her results are important for aquaculture - if the artificial environments fish farms create restrict the way fish display these natural defence behaviours, then they will be more susceptible to infection.October 19, 2017 News
Know your enemy – understanding the movements of a devastating parasite to outsmart it
Sun Tzu's 'The Art of War' tells us we must know our enemy if we hope to defeat it. In modern aquaculture, the greatest enemies are parasites that plague production and are a key part of many environmental effects. One of the worst parasites in salmon farming is a pesky amoeba that causes severe gill damage. As parasite outbreaks are extremely costly, the search is on for methods to reduce infection rates. One strategy is to reduce contact between salmon and the parasites in fish farms. But to do this, we must first know where these tiny parasites are and what drive their movements.
In a new study published in Aquaculture Environment Interactions this month, Dr Daniel Wright and colleagues from the University of Melbourne hunted for this marine parasite in Tasmanian salmon farms over 2 years. After taking over 300 separate water samples at farms and in their surrounds, there was no clear pattern between where the parasite was, depth in the ocean or the swimming depth of the fish.
Now we know our enemy, we have a better idea of which control methods will work and which won't. For other parasites, control methods we developed that permanently change the swimming depth of fish swim are very successful. But they won't work for this amoeba. We must now look for other possibilities to disconnect amoeba from salmon. These could include spreading fish densities more evenly at night with underwater lights and moving fish into brackish water that makes the amoeba leave the gills.October 19, 2017 News
Rapid growth leads to hearing loss in farmed salmon
A new article led by Tormey Reimer, a Melbourne University Masters graduate, reveals that about half of farmed salmon are deaf due to accelerated growth in the aquaculture industry. Tormey and colleagues discovered that fast-growing fish were three times more likely to have ear bone deformities, leading to substantial hearing loss.
In this pursuit article, co-author Associate Professor Tim Dempster explains that these results “raise serious questions about the welfare of farmed fish” as the deformity is irreversible and becomes worse over time.October 19, 2017 News
Escapes from aquaculture – what a technical standard can do
The recent dramatic images of the breakdown of an Atlantic salmon farm on the Pacific coast of the U.S. are startling. Square steel cages in a tangled mess with the fate of the 305000 fish they contained as yet uncertain. Some have been recovered from the cages, some will have escaped. Norway suffered a similar spate of escapes due to whole cage or farm breakdown over a decade ago. Norway still suffers escapes from salmon farms, but farm or whole cage breakdown has disappeared from the causes of escape. How did they fix it?
From 2009-2012, the European Union’s Prevent Escape project led by Tim Dempster (now with the Sustainable Aquaculture Laboratory at the University of Melbourne) delved deep into the causes and consequences of escapes from aquaculture, with the purpose of identifying how we could better stop escapes.
As part of the project’s work, a detailed analysis of escapes in Norway's Atlantic salmon production revealed that after the Norwegian technical standard (NS 9415) for the proper design, dimensioning and operation of sea-cage farms was implemented in 2006, the total number of reported escaped Atlantic salmon declined dramatically, despite the total number of salmon held in sea-cages increasing by greater than 50% during this period (Jensen, Dempster et al. 2010; Aquaculture Environment Interactions).
What did the introduction of the technical standard do? Well, it encodes the type of technology (cages, mooring systems etc.) that can be used at farming sites depending upon the maximum forces those sites experience in a once-in-50-year storm or severe weather event. Prior to the technical standards introduction in Norway, big escapes happened due to the breakdown of cage structures and mooring systems. The technical standard basically eliminated complete farm failure as a cause of escape.
Based on the success of this measure, the Prevent Escape project recommended that policy-makers worldwide introduce a technical standard for sea-cage aquaculture equipment coupled with an independent mechanism to enforce the standard. We were pleased to see that Scotland followed with a new technical standard in 2015, yet other producing nations are still lagging behind on this key mechanism to prevent escapes.
It leads us to ask the question, if the U.S. had introduced a legislated technical standard that reflected best practice and drew upon the long success of the Norwegian technical standard, would this massive escape ever have occurred?August 30, 2017 News
PhD project with $10000 per year top-up scholarship available
The future of aquaculture: how will fish cope with an offshore life?
A PhD project is available to investigate the behaviour and welfare of farmed salmon in new and emerging fish farm designs, principally for offshore and exposed locations. The project is a collaboration between the Sustainable Aquaculture Lab at the University of Melbourne (http://blogs.unimelb.edu.au/saltt/) and the Institute of Marine Research, Norway (www.imr.no/en). The student will be based in the School of BioSciences at the University of Melbourne, while experimental work will occur at the Institute of Marine Research’s state-of-the-art aquaculture research facility near Bergen, Norway, and in the field at commercial farms around the scenic fjords of western Norway.
There has been much debate regarding the salmon industry’s footprint in coastal waters. Part of the debate has revolved around whether farms should move to more exposed or offshore locations, where many of the problematic interactions with coastal environments and communities might diminish. A myriad of new fish farming concepts are now being proposed and implemented to tackle this challenge.
Offshore and exposed production system types have design aspects that alter the environmental conditions and behavioural context for fish relative to standard farms. Understanding these new production environments and their challenges for fish is key to success. Existing evidence suggests that several parameters critical for production will differ, including current flows, fish swimming speeds, school structure, dissolved oxygen levels, and fish buoyancy levels.
The PhD project will develop knowledge of the behaviour and welfare of salmon in new production systems. We will use a range of equipment to study fish farming environments and fish behaviours, including individual fish tags, echo sounders, and camera systems. Experiments will be conducted in research facilities and salmon farms that are testing new technologies.
The student will need to obtain an Australian Government Research Training Program Scholarship (https://studenteforms.app.unimelb.edu.au/apex/f…) for a PhD at the University of Melbourne. A first class honours or Masters is essential to qualify. A $10 000 per year top-up scholarship will be available in addition. Experience working with fish or in marine environments is desirable, but not essential. The student must be prepared to spend 2-3 months per year in Norway for experiments. The project starting date is flexible.
Expressions of interest (with CV attached) are welcome at any time until the position is filled. For further information contact Assoc. Prof. Tim Dempster (firstname.lastname@example.org).July 17, 2017 News
Can we “program” fish by modifying their environment during early development to improve performance?
Salmon farmers want fish to be healthier, faster growing and to produce flesh of the highest quality at harvest. Unlike livestock, fish spawn eggs into the water, so that eggs, alevin and other stages of early development are fully exposed to a range of different factors which occur in the natural or aquaculture environment. A number of important processes and systems develop and become functional during these early stages of development (eg. the immune system, musculature, stress response axis etc).
We know that some external factors, like water temperature, can affect these developmental processes (for instance, higher temperatures resulting in higher incidences of spinal and jaw deformities). Some such factors are known to change the “epigenome”, areas outside of the genome that can have lasting affects throughout development on the rate of gene transcription. But what if we could manipulate the environment in which the animal is immersed to optimise and tailor development to produce a faster growing, healthier fish of exceptional quality?
In a new paper published in Scientific Reports, a team of Scientists from Nofima in Norway, including Associate Professor Nick Robinson from Melbourne University, have investigated how low temperatures and oxygen deprivation can program the Atlantic salmon embryo and post-hatch larvae to affect performance of the fish in later life. Low temperature and oxygen deprivation during these developmental phases were found to modify the epigenome, so that gene expression was regulated in a way that affected the subsequent growth performance of fish for 35 days after they were put out to the sea in cages. Fish that were treated with such mild chronic stresses both during embryonic and post-hatch larvae stages grew faster than unstressed fish, or fish that were treated at just the embryonic or just the post-hatch larvae stage.
The findings support the general notion that tighter regulation of factors in the water surrounding the fish during these early developmental phases could be utilised in a way to program the animal for improved performance in the aquaculture environment.July 11, 2017 News
Supersizing fish farms – the way forwards?
There has been much debate in Tasmania regarding the salmon industry - how much farming there should be and where it should occur. Part of the debate has revolved around whether farms should move to more exposed or offshore locations, where many of the problematic interactions with coastal environments and communities might diminish.
In that context, SALTT has been closely following global innovation trends in aquaculture. There is now a distinct movement towards bigger farming units in more exposed locations to solve similar problems.
Check out this video - construction of the world's largest fish pen, capable of holding 1.5 million salmon at harvest size (that is about 7500 tons!), built in China for a Norwegian salmon farming company.
The world will be watching how successful this new technology is and if it can crack open some of the problems current day farms face.June 7, 2017 News
Swim deep and stay safe from parasites
For Australians, ‘sea lice’ are the bane of beach goers – microscopic marine irritants that get down your 'budgie smugglers' and leave a nasty rash. In the world of salmon aquaculture, ‘sea lice’ are an altogether different foe, tiny parasitic copepods that attach to fish and eat their skin and blood, leaving a horrifying bill of around US$2billion per year.
Earlier this year, we posted on a great new paper by Daniel Wright and colleagues about how an invention, the ‘snorkel cage’, reduced infection of farmed salmon with parasitic sea lice. The new fish farm design prevented fish from accessing parasite-risky surface waters by using a net roof and a lice-proof ‘snorkel’ tube up to the surface.
We have pushed the technology further in a new study published in Pest Management Science, written by a team led by Frode Oppedal from the Institute of Marine Research in Norway and SALTT resident fish vet Francisca Samsing at the University of Melbourne. Here, we showed that the deeper the snorkel, the better the preventative effect against sea lice, without affecting fish welfare. In the deepest snorkels, fish caught 10 times less lice than fish that swam shallow with no protection. It is terrific to see the industry taking up this new invention, with many snorkel cages now in place against these parasites.May 28, 2017 News
Fish farm waste: junk-food of the sea?
When waste from aquaculture flows into the marine environment, it becomes a food source for many marine animals. While rich in energy, this food contains a high proportion of terrestrial fats and oils, which are normally alien in the diets of marine consumers. The impact that this “junk-food resource” has on the ecology of marine ecosystems is poorly understood.
In a new study, University of Melbourne PhD student Camille White and colleagues investigated consumption of aquaculture waste by the white sea urchin in Norway. Camille spent many chilly days immersed in the spectacular western fjords of Norway to pull off this research.
The white urchin is a keystone species in Norwegian fjords and has the potential to drive ecosystem level change through over-grazing on kelp and creating bare rock barrens. Camille found that urchins are generalist feeders, that supplemented their normal diet with farm waste, readily exploiting aquaculture waste as an energy-rich food source. Just what this means for the urchins and their ability to reproduce, will be published in a few months time. Stay tuned!May 28, 2017 News
Infection protection with new fish farm design
Before ending up in your chopsticks or sushi roll, few people are aware that farmed salmon are commonly plagued by parasitic lice on their skin and amoebae on their gills. Fish farmers continuously struggle to control them, and the control methods themselves are often rough on the fish. An innovative new fish farm design has taken a different approach to prevent lice from infecting salmon in the first place.
Lice use light cues to aggregate in the surface layer - this behaviour is their Achilles heel which can be used against them. The new farm design has a deep net roof and a lice-proof 'snorkel' tube up to the surface. This surface access tube is needed as salmon use the snorkel to swallop air to re-inflate their buoyancy-controlling swim bladder. If they can't get to the surface to do this, they are too heavy and keep sinking.
In a new paper published in Preventative Veterinary Medicine, Melbourne University PhD student Daniel Wright and colleagues document how these new snorkel farms are working at industry scale. They clearly reduce lice, but gill amoebae infections were elevated from holding fish in less space. To solve this problem, snorkels were filled with freshwater to remove the freshwater-sensitive amoebae. Danny's work shows that farmed salmon of the future could be less burdened by these two important parasites using this new method.
Danny finished his PhD in late 2016 and moved to Norway to do a post-doc to further this exciting work. We wish him well.April 19, 2017 News
Farmed salmon – mostly clueless about dissolved oxygen
Of the many factors which limit the growth and survival of farmed salmon, hypoxia (low dissolved oxygen concentration) is among the most complex to monitor and remedy. In a new study, PhD student Tina Oldham and colleagues manipulated dissolved oxygen levels within sea cages at certain depths by the use of a tarpaulin to block the inflow of water. While caged Atlantic salmon behaviour and distribution after DO levels plummeted in this zone were partially explained by the poor oxygen conditions, other environmental factors such as temperature and salinity were far more powerful predictors of what the salmon did. These findings suggest that, in the highly variable marine cage environment, salmon are likely to expose themselves to sub-optimal oxygen conditions even when ideal conditions are available.April 18, 2017 News
Farmed salmon are hard of hearing
In short, Tormey and colleauges found that half of the world's farmed fish have substantial hearing loss due to conditions in their production environments.
The results have implications for how billions of fish are farmed and how fish are produced to re-stock declining populations of wild fish.November 29, 2016 News
Stopping the great escape
When farmed fish escape into the wild, they do all sorts of damage to native populations, such as narrowing the gene pool through inter-breeding and spreading diseases. A new study led by Melbourne Uni marine biologist Tim Dempster shows that trying to recapture escapees around marine fish farms is a bad solution that can do much damage with little good. Instead, the study suggests a radical change in focus to reduce the impacts of escapees in the wild.November 29, 2016 News
Future aquafeeds may compromise reproductive fitness in a marine invertebrate
There are lots of places in the world where humans put food into the ocean, either accidently or on purpose. It ends up in the mouths of animals, and can have unintended consequences. Aquaculture is a major source of this food, and feeds from aquaculture are a lot different to a natural diet.
Camille White, a UniMelb PhD student has been looking into this issue. In a paper published today, she shows how you can supersize urchins by feeding them the 'junk food' that spills into the environment from aquaculture, but if they get too much of a good thing, they can’t reproduce!November 24, 2016 News
Australia’s Four Corners investigates the Tasmanian salmon industry
Big Fish by the ABC's Four Corners program took a deep dive into the practices and sustainability of the Tasmanian salmon industry. Tim Dempster was interviewed on the conditions in 2016, the hottest summer on record in Australia for over 100 years and a challenging time for growing salmon.November 8, 2016 News
Fish escapes from marine farms raise concerns about wildlife
Our work has recently featured in the September issue of Science News in an article on the problem of escaped fish entering the wild and what to do about them.
SMOOTH CRIMINAL Farmed sea bass and other fish frequently escape from sea cages out into the ocean. Researchers worry that escapees, like this sea bass found off the coast of Tenerife in the Canary Islands, could threaten wild ecosystems.November 8, 2016 News
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