World Aquaculture Magazine - March 2024

68 MARCH 2024 • WORLD AQUACULTURE • WWW.WAS.ORG matter of fact, smoked eel is the main local gastronomic product and virtually every Volendammer has or used to have a relative that once was a fisherman, and more specifically an eel fisherman. In fact, elderly people used to say that in the past the harbor of Volendam was so full of eel-fishing boats that you could cross the haven just by jumping from one boat to another. There is only one eel fishing boat left, currently, and the eel fishing activity is strictly regulated by quotas and seasonality. Given these premises, it’s easier to understand the goal of the company: to close the life cycle of eel in captivity to provide eel farms with hatchery produced glass-eels. Furthermore, these brave early investors, together with new ones added along the way, want to restore the ancient splendor of a rich eel fishing city and cast Volendam in the future as “Eel city 2.0” A Special Life Cycle The European eel is a catadromous fish species with a very peculiar life cycle and multiple life stages (Fig. 2). Spawning occurs in the Sargasso Sea, where the larvae hatch from eggs after two days. In about 1.5 months these larvae develop into the leptocephalus stage. The leptocephalus is a typical larval stage of the superorder Elopomorpha, characterised by very small heads and willow leaf-like transparent bodies. At this stage, they migrate to Europe across the Atlantic Ocean, probably drifting with the Gulf Stream. Just before entering European continental waters, they metamorphose into glass eels. Once in freshwater, glass eels transform into elvers (juvenile eels), then into yellow eels, before returning to saltwater as silver eels and then, while maturing, they migrate back to the Sargasso Sea to spawn. The European eel (Anguilla anguilla) has a very complicated and lengthy life cycle, making closed-cycle cultivation impossible so far. Thus, eel aquaculture is still fully dependent on wild-caught juveniles (glass eels). The European eel population has declined by 90 percent in the past 50 years because of a combination of factors such as loss of habitat, pollution, diseases, obstruction of migration routes, and fishing efforts. The International Council for the Exploration of the Sea (ICES) recently reported that the number of glass eels entering fresh water from the North Sea has drastically decreased in the last 40 years (Fig. 1). Therefore, the International Union for the Conservation of Nature (IUCN) has listed the European eel as “critically endangered.” Thanks to continuous effort by the eel industry and NGOs over the last years stocks can be considered stable. Additional effort will be required to allow the stocks to increase again. While farming glass eels to market size is a well-established procedure, the life cycle of the European eel has still not been closed in captivity. This is where the research institute Glasaal Volendam comes on stage (Fig. 2). What is Glasaal Volendam? Glasaal Volendam is a company that was founded in 2012 by some private investors from the Dutch city of Volendam. To understand Glasaal Volendam, you first must know something about what Volendam means and what is the correlation between European eel and this small city. Volendam is a small town in the north of The Netherlands, on the shores of lake Ijssel, an artificially closed off inland bay that is now almost completely freshwater. Volendam is a city with a very strong eel-fishing tradition. As a Recent Steps Toward Closing the Life Cycle of the European Eel (Anguilla anguilla) in RAS Camillo Rosso FIGURE 1. Glass eel recruitment indices FIGURE 2. European eel life cycle, including the continental and oceanic phases. The completed milestones of Glasaal Volendam are shown in yellow. Milestone 6 has been reached this year and now the glass eel stage is only one step away.