Impact of Anabaena spp. blooms on sensory quality of rainbow trout (Onchorynchus mykiss)
A study was conducted on ten small, eutrophic water bodies affected by cyanobacteria blooms. The genus Anabaena (A. spiroides and A. flos-aquae) is often implicated in the appearance of these blooms. The consequences of these blooms on the sensory quality of fish have been studied. Anabaena spp. produce geosmin, and this earthy-musty volatile compound is found in trout flesh with significant concentrations, up to 850 ng•kg‐1. Trout are also tainted with the presence of a repulsive flavour (intensity of bad taste up to 8.3/10). A microcosm study of the kinetics of uptake and depuration of geosmin was conducted on rainbow trout (Onchorynchus mykiss). After an exposure of 6 h to geosmin, trout are significantly tainted with the appearance of significant concentrations of geosmin in the flesh and detection of repulsive flavour by taste. After an exposure of 30 h to geosmin, an open clear-water circulation system induces an elimination of the earthy-musty compound and a progressive reduction of off‐flavor intensity. The recovery of a good sensory evaluation for trout is obtained after more than four days. A significant correlation was found between Anabaena spp. density and geosmin concentrations in trout flesh (r2 = 0.74, p < 0.01). The sensory threshold of geosmin in trout by the panel of assessors is relatively low (500 ng•kg‐1) for samples collected in situ and for trout exposed artificially to geosmin. The management of off-flavour problems in these fishing water bodies requires the use of preventive methods before the appearance of cyanobacteria.