Effect of temperature on the development of skeletal deformities in Gilthead seabream (Sparus aurata Linnaeus, 1758)

The development of skeletal deformities is an important problem for finfish hatcheries. In the present paper, the effect of water temperature on the development of skeletal deformities in Sparus aurata was examined. Six combinations of three temperatures (16, 19, and 22 °C) were applied during three ontogenetic windows: the autotrophic (embryonic and yolk-sac larval stages), the exotrophic larval (first feeding to metamorphosing larvae of 14–16 mm TL) and the juvenile (metamorphosing larvae of 14–16 mm TL to juveniles of 40–45 mm TL) periods. The results demonstrated a significant effect (p < 0.05) of water temperature on the development of inside folded gill-cover, haemal lordosis, as well as of mild deformities of the caudal and dorsal fin-supporting elements. The prevalence of gill-cover deformities was elevated when 16 °C water temperature was applied during the autotrophic and exotrophic larval periods (50.0 ± 2.8%, mean ± SD), or only during the autotrophic period (14.0 ± 0.0%). Haemal lordosis development, the second most severe skeletal deformity, presented fluctuating response against water temperature up to 14–16 mm TL (3.0 ± 4.2 to 13.0 ± 9.9%). However, the application of 22 °C during the juvenile period resulted in the lowest and less variable incidence of haemal lordosis (1.0 ± 0.0 to 5.0 ± 1.4%). The mild deformities of caudal and dorsal fins presented different responses to water temperature. The prevalence of caudal-fin deformities was elevated when 16 °C temperature was applied during the exotrophic larval period (54.0 ± 8.5%), while dorsal-fin deformities were favoured when 22 °C temperature was applied during the autotrophic and exotrophic phases (35.0 ± 9.9 to 39.0 ± 4.2%). In the examined thermal range, growth rate was significantly elevated with the temperature increase. Fish survival was higher in the treatments where temperature after yolk-consumption increased from 16 or 19 °C to 19 or 22 °C, respectively. The results are discussed in respect to the onset of ontogeny of the different skeletal elements and the need of applying different thermal conditions during the development of S. aurata.