By Diogo Thomaz
By Diogo Thomaz
Early this year I visited Dabie trout hatchery in northern Poland, the key supplier of genetic material for the Polish trout industry and also an exporter of selected eggs to countries in the region.
In scientific lingo parallel evolution refers to cases where similar traits are developed in distinct lines, usually because they are subjected to similar selective pressures. The shape of bodies in sharks and dolphins are a good example; the need for hydrodynamic body shapes for efficient swimming in the seas lead to similar body shapes in species that are over 400 million years apart in evolutionary history.
Visiting Dabie hatchery I was struck by the dynamic changes in the water treatment technologies and the way new, improved variations were replacing older versions. This, in a company whose job it is to fine tune genetic selection of trout strains, made me think that evolution is indeed in the genes of these people. Their optimization of trout strain performance is achieved in parallel with the optimization in the performance of their water treatment systems. Parallel evolution!
Success in a genetics selection program depends on good use of science but also on listening closely to your customers. It is important that you select the traits farmers need in order to produce a better product in a more economical manner.
At Dabie it starts with 12 lines of rainbow trout that are the product of Krzysztof Grecki’s 25 years of selection work. There is a focus on keeping genetic variation high in these lines, a form of genetic health that will allow them to remain productive and selectable for many generations. Also there is a continuous selection for disease resistance across a number of pathogens affecting the industry.
The team at Dabie maintains a close relationship with its customers and collect quantitative as well as qualitative data on the performance of their eggs and fry. This data is processed into breeding values for each of their broodstock and is the information that feeds evolution in the stocks of this hatchery. This means that there is a very close link between the characteristics of the stocks and what farmers require from these. The reason why Dabie uses this strategy instead of a more ‘academic’ measurement of performance and selection is that factors such as growth performance or FCR are highly influenced by each farm’s husbandry, water quality, feeds and feeding techniques used.
Technology & water quality
One aspect that impressed me during my visit to Dabie as well as to a few trout producers in the region was the way the industry is structured and growing to really take a key position in the supply of seafood in the country.
Most farmers have invested heavily in technology to improve water quality and the design of tanks and waterways in the farms have been going through a rapid evolution that aims at using less water and increasing fish densities. The pressures come from nature as well as legislation with increasing costs of water usage and increasing demand for water quality.
In this respect Dabie hatchery has also been leading the way. The facility is made up of three groups of outside raceways (24 in total) where spawners on natural photoperiod are kept. There are also 10 smaller tanks for fingerlings and then a number of indoor tanks for photoperiod control.
Marcin Jesiołowski, the Operational Head of the hatchery, showed me the tanks and explained that they were as alive as the fish inside them! Every year they try a new technology to improve water quality and then they measure the performance of the technology by looking at fish performance and at water quality parameters. When performance improves they expand the technology to other tank groups and start again with new tests for more improvements.
One technology that was recently adopted in the industry is the use of drum filters to remove solids. Drum filters are not new, but they have been improving in the reliability and robustness and the ability to filter large quantities of water even when using very fine meshes. I am not an expert in RAS technology but it appears that how fine this mesh is will influence how the biofilter material will perform: the more particles you remove the more organic matter is taken from the water at the drum filter stage and the finer the mesh in the biofilter material the greater the area and the greater the efficiency in removing ammonia, nitrites and nitrates.
Change is tricky
We see then that the water treatment system has to change as a whole in order to take advantage of each separate change and this makes it complicated to reach the right results when you are undertaking trials…
The stage where Dabie is today allows them to use a new biocarrier called Levapor in the fluidized beds of the reactors. They maintain that Levapor effectiveness is up to three times higher than the bioblocks commonly used in RAS. With a surface-to-volume ratio greater than 2,700m2/m3 Levapor is certainly very competitive with other products.
Another interesting characteristic of Dabie’s raceway systems is that they operate with amazingly low power; there are practically no water pumps in the system with water circulation done through the use of airlifts that also oxygenate the water and complement the injection of pure oxygen. Typically to produce 100 tons of biomass Dabie requires three liters per second of water input and an average 15kW supply of power.
Testing and selecting
The changes tried and tested in the last few years are now being transferred to all systems in the hatchery. I was impressed to hear that as work progressed to change tanks and water treatment systems in one group of tanks there were already results from tests with new developments that would require other changes in that system. Marcin told me that at Dabie nothing ever stops evolving.
Tank design allows for faster water exchanges and better water quality, a factor in the quality of the fish produced. Again here the company keeps improving design and efficiency and after construction of the first unit of seven tanks the new unit under construction already is being designed with new standards.
— Diogo Thomaz
Diogo Thomaz, PhD, MBA, is a Technical and Business Consultant for the Aquaculture Industry, based in Athens, Greece. After 15 years as R&D project manager and other industry positions he now leads Aquanetix (www.aquanetix.co.uk), a data management and reporting service for the global aquaculture industry. He also heads RealSales Ltd (www.realsales.eu) a sales consultancy company that helps businesses expand their opportunities in export markets. He can be contacted by email on email@example.com