Reports

Possibilities for the production of natural zooplankton for the first feeding of marine larvae

Published:

01/10/2008

Authors:

Jónína Þ. Jóhannsdóttir, Rannveig Björnsdóttir

Supported by:

Verkefnasjóður Sjávarútvegsins / Project fund of the Ministry of Fisheries

Possibilities for the production of natural zooplankton for the first feeding of marine larvae

The overall goal of the project is to make an assessment of the possibilities of producing natural zooplankton for use in the early stages of aquaculture in Iceland. The quality and supply of larvae is one of the main problems in aquaculture today. The larvae of most marine fish need live prey when the pre-nutrition of the peritoneum is exhausted, in which case the supply of live feed animals is necessary until the larvae begin to absorb dry food. Domestic farms have primarily used rotifers and artemia that need to be bought from abroad and bred in the farms. There is a lack of the right composition of nutrients in these feed animals compared to zooplankton, which is the natural food of marine fish larvae, and research shows that the use of zooplankton provides increased yields and improved larval growth. The supply of natural zooplankton is seasonal, but the cultivation of various species has been tried in several parts of the world with good results. The results of research indicate that it is possible to cultivate various types of crayfish in sufficient quantities for production for juvenile farms. Many species of plankton are found in the marine ecosystem by the land that could be suitable for aquaculture, such as redfish, A. longiremis and Oithona spp. It is planned to apply for a research grant to the fund for the installation of facilities and experiments with the cultivation of selected species (s) of zooplankton.

The main goal of this project was to evaluate the potential for production of natural zooplankton for production of marine fish larvae in Iceland. Satisfactory quality and survival of larvae are one of the main problems in marine aquaculture. Marine larvae are fed live zooplankton during the first feeding stages, when the contents of the yolk sac are spent. Icelandic producers of marine fish larvae mainly use imported rotifers and Artemia as live feed. Copepods are the main food source of marine fish larvae in their natural environment and previous research indicate that the nutritional value of rotifers and Artemia is not adequate for successful development of the larvae. Successful growth and survival of larvae have been achieved using natural zooplankton. However, seasonal growth of natural zooplankton species prevents their use in commercial production of fish larvae. Copepods have been successfully cultured and there are indications that copepods can be cultured as feed in the production of marine fish larvae on a commercial scale. Various zooplankton species are found in the Icelandic marine ecosystem and that may be ideal candidates for culturing eg Calanus finmarchicus, A. longiremis and Oithona spp. As a next step, we will apply for funding of a larger project where the aim is to develop experimental facilities and carry out experimental cultures of selected species.

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Reports

Leit að bætibakteríum / Searching for putative probionts in the production system of halibut larvae

Published:

01/09/2008

Authors:

Jónína Þ. Jóhannsdóttir, Eyrún Gígja Káradóttir (MS student), María Pétursdóttir, Jennifer Coe, Heiðdís Smáradóttir, Rannveig Björnsdóttir

Supported by:

Tækniþróunarsjóður Rannís (2006-2008) / Technology Development Fund of Rannís, the Icelandic Center for Research (2006-2008)

Leit að bætibakteríum / Searching for putative probionts in the production system of halibut larvae

The overall goal of the project is to improve the survival and quality of halibut larvae in starter feeding using supplementary bacteria. In the composition of supplementary bacteria for fish, the breeding of warm-water species has often been considered, and the bacterial species that have been used have proved to have a poor foothold in the environmental conditions involved in the breeding of cold-water species, such as halibut. This project seeks out and identifies bacteria that are prevalent in halibut larvae from breeding units that have been successful in terms of larval performance and metamorphosis. Studies were performed on the properties of isolated bacterial strains in terms of growth inhibitory effects on known pathogens for fish as well as predominant bacterial species from halibut larvae in breeding units where the performance and quality of larvae were below average. The predominant bacteria were isolated from larvae in all breeding units of Fiskey hf. in two different periods in addition to which samples were taken from juveniles in export size. The results of studies on the growth inhibitory effect of isolated strains revealed 18 bacterial strains that were found to inhibit the growth of known pathogens and / or bacterial strains that had been isolated from the larval rearing environment. Sequencing results showed a good correlation with 6 different bacterial species. Subsequently, it will be treated with a selected mixture of additive bacteria in the early stages of halibut farming.

The overall aim of this project is to use probiotic bacteria to promote increased survival of halibut larvae during first feeding. Previous studies indicated that the microbial load of larvae and their environment represents a problem and the objective of this project was to search for possible candidates for probiotic bacteria to promote survival and growth of larvae use during the first and most sensitive phase of production. Potential probiotic strains were selected on the basis of dominance in the gut of larvae from production units with successful growth, development and survival. The growth inhibiting activity was tested against known fish pathogens as well as bacteria dominating the intestinal community of larvae from production units with poor overall success. We isolated dominating bacteria in the gut of larvae from all production units of two different spawning groups at Fiskey Ltd. and also from export-size fingerlings. Growth inhibition studies revealed 18 bacterial isolates that inhibited growth of known fish pathogens and / or dominating bacterial isolates from the gut of larvae of an overall poor quality. 16S rRNA sequencing revealed a reasonable correlation to 6 bacterial species and presently. As a next step, halibut eggs and larvae will be treated with selected strains to test their potential as probionts during the first production stages of halibut aquaculture.

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Reports

Use of bioactive substances in halibut farming

Published:

01/12/2007

Authors:

Jónína Þ. Jóhannsdóttir, Heiðdís Smáradóttir, Jennifer Coe, Rut Hermannsdóttir (MS student), María Pétursdóttir, Rannveig Björnsdóttir

Supported by:

Líftækninet HA (2005-2007), KEA University Fund (2006)

Use of bioactive substances in halibut farming

The main goal of the project was to promote the increased performance of halibut in fire and use environmentally friendly methods. Bioactive substances were used that were easy to obtain, contributed to the increased value of seafood and also had some of the desired activity, ie. bactericidal / inhibitory, prebiotic or immunostimulatory activity. Experiments were made with various materials in the project, ie. chitosan derivatives as well as peptides derived from blue whiting, cod and saithe. The effect of treatment with the substances was assessed in terms of the growth and performance of larvae and forage animals as well as in terms of the composition of the bacterial flora and the stimulation of a non-specific immune response in larvae. The main results indicate that the most suitable method for introducing substances into larvae is to use feed animals (Artemia) and a method was developed in the project to treat them. The bioactive substances did not appear to have a bactericidal effect in the rearing environment of the feed animals, but did contribute to a change in the composition of the bacterial flora. Bioactive substances seemed to be used primarily as supplements as feed animals were plump and playful. The performance and quality of larvae in the breeding units of Fiskey hf. is very different and there is no obvious relationship between the performance of the peritoneal stage and the performance and quality of the larvae at the end of the initial feeding. The composition of bacterial flora was also found to be very different in peritoneal larvae and larval feeding larvae. Three separate experiments were carried out in the Fiskey juvenile farm where the larvae in the initial feeding were treated with bioactive substances. The main results showed that it is important to treat with the right concentration of substances and for a reasonably long time as too much concentration can have a negative effect on the growth and metamorphosis of larvae. Treatment with blue whiting peptides was thought to give promising results and have a beneficial effect on larval metastasis. Bioactive substances did not appear to have a decisive effect on the number of bacterial bacteria in the gastrointestinal tract of larvae, but treatment with blue whiting and cod peptides could potentially alter the composition of the flora. Studies on the non-specific immune response of halibut larvae revealed the presence of C3 and Lysozyme from the end of the peritoneal stage, but IgM production does not begin until about 28 days after the start of feeding. Higher levels of IgM were detected during the first weeks in larvae treated with saithe peptides and this may indicate an immunostimulatory effect. The results of the project as a whole indicate that the bioactive substances studied did not have a decisive effect on the bacterial flora of the farm, but the treatment of larvae in starter feeding with the right concentration of bioactive substances could have a good effect on larval performance and stimulate larval immune response. of the farm when they have not yet developed a specialized immune response.

The aim of this project was to promote increased survival of halibut larvae during first feeding by using bioactive products. The bioactive products were selected by the criterion that they were easily accessible and induced any of the desired effects ie inhibiting bacterial growth, prebiotic effects or immunostimulants. The products studied are chitosan and peptide hydrolysates from blue whiting, cod and saithe. The effects of treatment were evaluated with respect to growth and survival of larvae and the live feed (Artemia) as well as effects on bacterial numbers or the community structure of the intestinal microbiota of larvae and stimulation of the innate immune system of the larvae. The results indicate that treating live feed (Artemia) is a suitable method to carry the bioactive products to the larval intestines during first feeding and a new technique has been standardized for treatment of the live feed with the products. The bioactive products did not affect the total bacterial count in the Artemia but the composition of the bacterial community may be changed as a result of the treatment. The Artemia seems to use the bioactive products as a food supplement and was well suited to be used as live feed. A significant variation in overall success of larvae was observed without any obvious correlation between survival of larvae at the end of the yolk sac stage and at the end of first feeding. A different bacterial pattern was observed in the intestine at the yolk sac stage compared to first feeding larvae. Three separate experiments were carried out in the halibut production units at Fiskey Ltd. where larvae were treated with various bioactive products. The results emphasize the importance of treating larvae with the appropriate concentrations of the products, as elevated concentrations can negatively affect growth and metamorphosis of the larvae. Treatment with peptides from blue whiting resulted in relatively good survival of larvae with similar success of metamorphosis compared to control units. The bioactive products did not affect bacterial growth but there were indications that peptides from blue whiting and cod may affect the composition of the intestinal community of bacteria in the larvae. Results from studies of the immunological parameters indicate the presence of C3 and Lysozyme already from the end of the yolk sac stage and the initialization of IgM production after approximately 28 days in feeding. Production of IgM was stimulated in larvae treated with peptides from saithe, indicating immunostimulating effects of this product. The overall results indicate that the bioactive products studied did not affect the bacterial flora during the first production stages of halibut larvae. However, if used in the appropriate quantities and at the right time, the products may promote survival and growth and stimulate the innate immunity of larvae.

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