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Do young on‐grown eels, Anguilla anguilla (Linnaeus, 1758), outperform glass eels after transition to a natural prey diet?
Author(s) -
Dainys J.,
Gorfine H.,
Šidagytė E.,
Jakubavičiūtė E.,
Kirka M.,
Pūtys Ž.,
Ložys L.
Publication year - 2017
Publication title -
journal of applied ichthyology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.392
H-Index - 62
eISSN - 1439-0426
pISSN - 0175-8659
DOI - 10.1111/jai.13347
Subject(s) - biology , predation , fishery , population , aquaculture , zoology , weaning , fish <actinopterygii> , ecology , demography , sociology
Summary Survival rates among European eels, Anguilla anguilla (Linnaeus, 1758), on‐grown using a formulated diet in a commercial aquaculture facility, were compared with glass eels from the same cohort following their transition to a natural prey diet in the laboratory. Treatments included zero, 42‐day, and 196‐day periods of grow‐out prior to 30‐day experimental periods when eels were fed Chironomus spp. larvae (10 tanks, each containing 240‐L water and 40 glass or 10 on‐growing eels; 12:12 hr photoperiod; water temperature 18°C). All glass eels survived, compared to 87% (42‐day) and 99% (196‐day) for on‐grown eels. Although the eels on‐grown for 196 days had a high survival rate, they did lose weight. Farm‐reared eels may have accumulated sufficient resources over the 196‐days to survive the first 30 days after weaning from a formulated diet, but not for an additional 30 days (84% survival). Lack of superior survival rates among on‐grown eels challenges the presumed benefits of releasing on‐grown eels for population restoration.