On the way to successful European eel larval rearing: Impact of biophysical conditions and gamete quality
The European eel is a widely distributed fish species of economic and cultural importance. It inhabits both coastal and freshwater systems, and is targeted by fisheries and treasured as food item. Although eels are reared in aquaculture, this industry relies solely of wild‐caught juvenile glass eels...
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| Format: | Book |
| Language: | English |
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DTU Aqua
2014
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| Online Access: | https://orbit.dtu.dk/en/publications/9ee1976c-7ef5-4802-93be-849ce187fea4 https://backend.orbit.dtu.dk/ws/files/106860450/Publishers_version.pdf |
| Summary: | The European eel is a widely distributed fish species of economic and cultural importance. It inhabits both coastal and freshwater systems, and is targeted by fisheries and treasured as food item. Although eels are reared in aquaculture, this industry relies solely of wild‐caught juvenile glass eels that arrive to the European coasts after a 6000 km journey from the Sargasso Sea, where they were hatched. The adolescent eels start their long migration from the European continent back to their spawning area in the Sargasso Sea in late autumn as sliver eels. As long as the eels are within the European continent, they are in an immature stage, and they do not start migration and maturation until the silvering stage. This stage is however tightly controlled by brain and pituitary hormones, preventing maturation of gonads remote from their natural breeding area. This hormonal inhibition of maturation is the main reason why it is difficult to reproduce European eel in captivity. Although, attempted since 1930ies, utilizing maturational hormones primarily from other fish species, we only recently succeeded in refining reproduction protocols that enable rich quantities of viable gametes from this species. In view of these obstacles, the last decade’s research has shown substantial progress. This PhD has contributed to this progress through new knowledge and development of procedures for successful egg activation and fertilization as well as incubation and larvae culture. My PhD work addressed biophysical determinants fundamental to producing healthy eggs and larvae. One of my aims was to improve methods and results of in vitro fertilization. This research included characterisation of sperm density, “optimal” sperm to egg ratios and gamete mixing. Eel gametes are activated by salt water and incubated in a marine aquatic environment. In this regard, my aim was to identify suited salinities and seawater sources, supporting a good embryonic development. Embryonic development lasts two days from fertilization to hatch. During ... |
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