A review on broodstock nutrition of marine pelagic spawners: the curious case of the freshwater eels (Anguillaspp.)

Abstract

To sustain eel aquaculture, development of reproduction in captivity is vital. The aim of this review is to assess our current knowledge on the nutrition of broodstock eels in order to improve the quality of broodstock under farming conditions, drawing information from wild adult eels and other marine pelagic spawners. Freshwater eels spawn marine pelagic eggs with an oil droplet (type II), and with a large perivitelline space. Compared with other marine fish eggs, eel eggs are at the extreme end of the spectrum in terms of egg composition, even within this type II group. Eel eggs contain a large amount of total lipids, and a shortage of neutral lipids has been implied a cause for reduced survival of larvae. Eel eggs have higher ARA but lower EPA and DHA levels than in other fish. Too high levels of ARA negatively affected reproduction in the Japanese eel, although high levels of 18:2n‐6 in the eggs of farmed eels were not detrimental. The total free amino acid amount and profile of eel eggs appears much different from other marine pelagic spawners. Nutritional intervention to influence egg composition seems feasible, but responsiveness of farmed eels to induced maturation might also require environmental manipulation. The challenge remains to succeed in raising European eel broodstock with formulated feeds and to enable the procurement of viable eggs and larvae, once adequate protocols for induced maturation have been developed.

Impact of dietary fatty acids on muscle composition, liver lipids, milt composition and sperm performance in European eel

“…5000 km spawning migration from Europe to arrive 6 to 7 months later at their spawning site, which is presumed to be in the Sargasso Sea (Schmidt, 1922;Tesch, 2003). In this regard, the development of 'optimal' broodstock diets may improve the species' reproductive success in captivity, through the production of highquality gametes and viable offspring from farmed fish (Heinsbroek et al, 2013;Støttrup et al, 2013). After studying sperm quality parameters and fatty acid composition during hormone-induced sexual maturation, Baeza et al (2014) found significant correlations between several fatty acids and sperm quality parameters in male European eel.…”

Development of a broodstock diet to improve developmental competence of embryos in European eel,Anguilla anguilla

“…, ; Heinsbroek et al . ). The results from the present study show a strong influence of the dietary fatty acid composition on fatty acid composition of European eel eggs, both in neutral lipids and in phospholipids.…”

“…Two experimental diets were developed, based on available knowledge on nutrient requirements (NRC ; Heinsbroek et al . ) and from a comparison of fatty acid content in the muscle and ovaries of wild‐caught and farmed female eel. These diets were tested against a commercial eel feed.…”

Roles of lipids and fatty acids through the spermatogenesis of European eel (Anguilla anguilla)

“…Many studies have proven the importance of broodstock nutrition in the reproductive performance of fish (Asturiano, 1999;Bobe and Labbé, 2010;Glencross, 2009;Heinsbroek et al, 2013;Izquierdo et al, 2001;Watanabe and VasalloAgius, 2003). The development of optimum diets for European eel broodstocks to ensure high quality gametes is key if we want to improve the chances of reproduction in captivity.…”

“…In order for eel aquaculture to be sustainable, the life cycle should be completed in captivity. In this regard, the development of 'optimal' broodstock diets may improve the species' reproductive success in captivity, through the production of high-quality gametes and viable offspring from farmed fish (Heinsbroek et al, 2013;Støttrup et al, 2013). After studying sperm quality parameters and fatty acid composition during hormoneinduced sexual maturation, Baeza et al (2013;Chapter III) found significant correlations between several fatty acids and sperm quality parameters in male European eel.…”