Reproduction of European Eel in Aquaculture (REEL)

This report presents results of the project, Reproduction of European Eel in Aquaculture: Consolidation and new production methods that was conducted during the period 1st October 2008 to 31th December 2010. The project received financial support from the Danish Ministry of Food, Agriculture and Fisheries and the European Commission through the European Fisheries Fund (EFF). The REEL project addressed the EFF initiative “to optimise aquaculture production including reduction in resource utilisation and environmental improvements, enhancement of recirculation technology and farming systems as well as development of a cost effective fry production”. The project applied an interdisciplinary approach integrating knowledge institutes and industry including SMEs in method and technology development. REEL was coordinated by the Technical University of Denmark, National Institute for Aquatic Resources (DTU Aqua) and participants included Copenhagen University, Faculty of Life Sciences (KU-Life), Danish Eel Farmers Association, Billund Aquaculture Service APS, BioMar A/S, and Bioneer A/S. The following persons contributed to this collaborative research and development project: Project aim: Enhance methods and technology applied to produce and culture European eel larvae as basis for the development of a future self-sustained eel aquaculture. Background: The severe decline of the European eel stock calls for conservation measures including national eel management plans and establishment of a self-sustained eel aquaculture. In 2005, the National Institute of Aquatic Resources at the Technical University of Denmark (DTU Aqua), the Faculty of Life Sciences at Copenhagen University (KU-Life) and the eel aquaculture industry started to build up a research and technology platform for the development of methods to reproduce European eel in aquaculture. Two major projects: Artificial Reproduction of Eels II and III (ROE II and III) succeeded during 2005-2008 to produce viable eggs and larvae that lived up to 12 days. The larvae thereby accomplished the yolk-sac stage and became ready to start feeding. The results were in particular promising because they evidenced that methods successfully applied to Japanese eel has a potential for application also to the European eel. ROE II and III were supported by the Ministry of Food, Agriculture and Fisheries and the European Commission through the Financial Instrument for Fisheries Guidance (FIFG) and the Danish Food Research Program 2006, respectively. Results: The REEL project accomplished through three series of experiments to consolidate previous results. The longevity of larvae was extended from 12 to 20 days after hatch in first feeding experiments thereby entering the leptocephalus phase. Maturation potential and methods to induce maturation were further tested, and farmed and wild eel broodstocks as well as different treatments were compared. In particular, fertilisation procedures to produce fertilised eggs and embryos and monitoring techniques were enhanced. The technology needed to culture embryos and larvae was substantially improved. The potential for new hormonal treatments was explored and full scale experimental series i.e. REEL A, B and C were conducted during the project period at the DTU experimental facility located on Lyksvad Fishfarm. The experimental protocols were developed by the project group integrating schemes for development and test of broodstock feed, as well as methods and procedures for hormonal treatment, fertilisation, incubation and larval rearing. Similarly plans for sampling and monitoring, and a database to record data were established. Various parameters were tested in the three experiments including parameters such as origin and size of broodstock eels, broodstock feeds, hormonal treatments and fertilisation methods. Methods and technology developed during previous projects: Artificial Reproduction of Eels (ROE lll) and the extension: Artificial Reproduction of Eels - Larval Culture (ROE lll-LC), were used as the starting point in order to consolidate and further improve methods and technology. Standardised methods to evaluate processes and monitor production were Only one of the farmed fish provided viable eggs whereas 4 out of 6 wild fish provided viable eggs that hatched into larvae. The fatty acid results showed significant differences in fatty acid distribution and levels of essential fatty acids between eggs from farmed and wild fish. These results will be used to further develop broodstock feed for farmed eel with the aim to alter content of eggs produced in farmed eel to mimic that in eggs produced from wild females. not contribute significantly to the model, provided ovarian cross sectional are included. The data suggest that ovarian cross sectional diameter can be used as a predictor of a successful outcome at the time of the 6 th scan (after 12 weeks hormonal treatment). These results are encouraging and the use of ultrasound should be investigated further in repeat trials with greater group numbers and possibly, alternative success criteria. ________________________________________________________________________________________________ gene technology was investigated. This task was carried out by Bioneer in collaboration with DTU Aqua and is described in 4.4. 2 Production technology to produce FSH and LF. Another method was presented by the ZF-Screens and Leiden University as the Dutch contribution to the Zanter project. The weekly injection of pituitary extracts implies that every eel must be handled manually each week, thereby increasing the risk of stress. As an alternative to the weekly hormonal stimulation, ZF-Screens and Leiden University work on developing cell implants that can be injected in the abdominal cavity and produce hormones over a prolonged period of time. These cells, ZF-implants (patented by ZF-Screens) uses zebrafish cells that produce eel hormones using recombinant technology. The test is described in 4.4. 2 Evaluation of ZF-implants, alternative maturing hormones (FSH and LF), SPE treatment and different final maturation hormones. The western blotting experiments showed that yields of GPα and FSHβ was strongly increased with stably transfected cells compared to when expressed by transient transfection. No high on eels in The technique further and it concluded that at the present state further futile. A state of development of the hormone producing implants allowing further tests was not reached by Leiden University and ZF-Screens during the project period. The planned collaborative experiments were cancelled and REEL project resources allocated to improvement of existing methods and hormone production using recombinant gene technology. An experiment was conducted to compare the two types of fertilisation procedures using 1) fresh sperm from males stripped directly over the eggs and 2) sperm from the same males, diluted in the medium using standardised procedures and applied in a standardised sperm to egg ratio. The egg monitoring method was used to evaluate fertilisation success. Egg batches from 8 females were fertilised using semen from 3-4 males either directly stripped over the eggs or diluted to a standardised density. Semen from the same males was used in the tests for all egg batches. The fertilisation procedures were conducted in parallel to enable comparison of treatments. Three hours after fertilisation, egg monitoring was conducted to estimate fertilisation success and egg quality.