Need
As demonstrated above, altered hatching time combined with larger onshore facilities has the potential to improve the profitability and sustainability of Huon’s operations, and may form the model for production in the Tasmanian industry. Previous Huon in-house production scale trials have advanced spawning by up to 10 weeks, but the fertilisation rate for advanced fish is 60-65% compared to normal ambient fertilisation rates in the 80-90% range. Huon has successfully delayed broodstock by six weeks previously to produce two pens of spring smolt, but has not combined this with reduced incubation temperature, which is a known risk factor for lifecycle fish performance and deformity. Continued work is required to optimise the environmental conditions and understand the factors involved in spawning success. The inability to produce a predictable outcome in terms of advancement and viability is costly and creates difficulties with production planning.
In order to understand what variables impact fecundity and whether modification of spawning and hatching times has long-term impacts on fish health and performance, commercial scale trials over the lifecycle of the fish are required. In order to do this, a minimum of two (replicate) production pens of fish must be produced for each treatment. Huon has a limited ability to maintain multiple controlled spawning regimes concurrently. A RAS is required as fluctuations in environmental conditions in flow through systems (such as Lonnavale) are extraneous variables that make comparison difficult. Huon owns one facility that is suitable for control of spawning time, the Springfield broodstock facility. This unit provides environmental stability and predictability as the water from all tanks is treated and temperature controlled in the one plant, but only one water temperature can be maintained. Delivering different photoperiod regimes to different tanks within the system is difficult, requiring curtains or screens to be erected along with controllers for the lights in and above each individual tank/section.
Huon has investigated building a twenty tank broodstock facility and priced the construction project at $6,300,000 for labour, materials, plant and equipment, IT and consultants. Such a facility would have the same limitations as the Springfield unit in terms of its inability to test more than one variable in advancement method. Huon would be committed to producing two levels of advancement for the foreseeable future, and it is not yet known what the production mix will be going forward (based on sales channels, managing smolt windows and maturity, and best managing biosecurity). In the long term Huon will invest in such a facility, however, it is crucial that the controlled spawning process and the production plan is fully understood before this investment is made.
In order to provide the ability for three treatments to be compared, Huon Aquaculture is looking to lease two RAS units in addition to the Springfield Broodstock RAS;
• The Tasmanian Eel Exporters, RAS Facility, Bagdad
• The Inland Fisheries Service, RAS Trial Facilities, New Norfolk
Outcomes from these two facilities will be compared with the Springfield advanced RAS facility, Springfield ambient flow through, Lonnavale flow through and a Lonnavale combination where brood are held in flow through and moved into controlled conditions in the November before spawning. The comparison will look at immediate spawning success, as well as lifecycle economic and environmental outcomes. Increased propensity for maturation is the most likely negative outcome with both methods of increasing smolt size.
Final report
with collaborative research recommending greater utilisation of onshore recirculating aquaculture
systems (RAS) combined with expansion into offshore areas to produce more biomass. This has led to
Huon Aquaculture to expand into the more dynamic offshore environment of Storm Bay and developing
the Whale Point nursery. A $45-million-dollar state of the art Atlantic salmon (Salmo salar) recirculating
aquaculture system (RAS). This expansion has resulted in the need to stock larger more robust post smolt
which are capable of better tolerating the harsh offshore marine environment with the aim of stocking at
sea for less than twelve-months. Therefore, Huon Aquaculture conducted experimentation on
manipulating the timing of brood stock spawning by placing them under an artificial temperature and
photoperiod regime that mirrors an ambient regime but is offset by a number of weeks (offset is measured
in relation to summer solstice) in Huon’s New Norfolk and Bagdad freshwater RAS hatcheries. The intended
outcome was to advance the timing of spawning by six, ten and fourteen-weeks and delay spawning by six
and fourteen weeks. In combination with changing day length, egg incubation time was also manipulated
by chilling the eggs to slow development. The ability to advance or delay hatching and first feeding time
gives Huon the potential to produce larger, early smolt and use the new Whale Point nursery facility to
house these larger smolt. The final outcome was to provide Huon with a longer and more flexible stocking
period, the ability to fill market gaps throughout the production year, produce large robust smolt that
spend less time at sea and an increase in end biomass. The trial was deemed a success, with smolt being
produced with a six, ten and fourteen-week advance and a ten and fourteen-week delay with some cohorts
spending less than twelve-months at sea. However, both the advanced and delayed stock had a lower
maturity rate, lower fertilisation rate and higher mortality in incubation that will require further
investigation and fine tuning to optimise the process.
