Production of wheeled animals for cod farming / Production of quality rotators for breeding cod fry




Jónína Þ Jóhannsdóttir, Agnar Steinarsson, Rannveig Björnsdóttir

Supported by:

Nordic-Atlantic co-operation (NORA)

Production of wheeled animals for cod farming / Production of quality rotators for breeding cod fry

There is great interest in finding ways to control farming conditions at all stages of aquaculture. The control of microbial flora in the environment and the gastrointestinal tract of larvae is, among other things, thought to be able to reduce losses that occur in the early stages of marine fish farming. A large number of bacteria usually accompanies feed animals in cod farming, but the use of recycling systems in the breeding of equidae has, among other things, the advantage that a smaller number of bacteria gain a foothold in the systems compared to batch farming. The use of bacterial flora for bacterial flora control has increased significantly in recent years and has in some cases contributed to increased growth and quality of larvae. In addition to strengthening co-operation between cod juvenile producers in the Nordic countries, the aim of the project is to develop methods that increase stability and efficiency in the production of feed animals. It is based on a recycling system designed by Sintef in Norway and this section investigates the effects and presence of selected beneficial bacteria in the system. The main results of treatment with two selected bacterial strains showed that the wheeled animals tolerated the treatment well and an increased crop of animals was obtained when treated with the bacteria in lyophilized form. There was a significant decrease in the number of bacteria in the purgatory during treatment with liquid bacterial culture and the number of bacteria in the purgatory did not reach the initial number during the experiment, but there was some increase in the number of lactic acid bacteria. Although the amount of lactic acid bacteria in equidae only increased after treatment, the bacterial strains did not gain a foothold in the system or lead to changes in the composition of the bacterial flora when treated at this concentration. The project is funded by Nordisk Atlantsamarbejde (NORA) and worked in collaboration with Matís, the Marine Research Institute, SINTEF, Fiskaaling, IceCod and Stofnfisk as well as Nordland Marin Yngel.

There is an increasing interest in controlling environmental parameters during the first production stages of aquaculture and controlling bacterial numbers is among various environmental parameters that are believed to promote increased survival of larvae. Elevated bacterial numbers are introduced into the system through the live feed, but numbers of bacteria have been found to be greatly reduced by the use of recirculation culturing system as compared with batch culturing systems. Furthermore, the use of potentially probiotic bacteria in aquaculture has increased over the past years and has in some cases contributed to increased growth and quality of marine larvae. In addition to promoting collaboration between cod producers within the Nordic countries, the main goal of the current project is to develop methods for stable and advantageous production of live feed animals (rotifers). The project is based on a recirculation culturing system engineered by SINTEF and the present part of the project deals with the effect of treatment and persistence of selected probiotic bacterial strains in the system. The overall results indicate that the rotifer cultures were not negatively affected by the bacterial treatment and treatment using freeze-dried preparations of the two probiotic strains even resulted in improved harvesting of the live feed. A drop in bacterial numbers within the bio-filter unit was, however, observed following the addition of liquid bacterial cultures, indicating negative effects of the bacteria on the bacterial community of the bio-filter unit. An increase in the numbers of lactic acid bacteria was observed in the rotifer cultures following treatment, but the probiotic bacterial strains were neither found to become established as a part of nor affect the dominating bacterial community of the system using the concentrations applied. The project was supported by the Nordisk Atlantsamarbejde (NORA) and is a collaboration between Matís, Hafrannsóknastofnun, SINTEF, Fiskaaling, IceCod, Stofnfiskur and Nordland Marin Yngel.

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