Abstract
The objective of the current study was to evaluate the effect of stocking density on juvenile Black Rockfish Sebastes schlegelii (average weight = 12 g) in terms of stress, hematological responses, and growth performance during a 4-month growth trial in a flow-through system. The initial stocking densities were 1.3 kg/m3 (low), 1.8 kg/m3 (medium), and 2.3 kg/m3 (high), and the final densities were 4.9 kg/m3 (low), 5.6 kg/m3 (medium), and 6.3 kg/m3 (high). At the end of the trial, the high stocking density significantly affected growth characteristics, levels of growth hormone and insulin-like growth factor 1, and hematological indices (hematocrit, red blood cell count, and hemoglobin level) compared to the medium and low stocking densities. The plasma cortisol and immunoglobulin-M levels were significantly higher at the high density than at the other two densities. Taken together, while the low and medium stocking densities (final densities of up to 5.6 kg/m3 ) did not affect stress and hematological indices or growth, the high stocking density (final density of 6.3 kg/m3 ) significantly impacted those variables, which suggests an allostatic load at that density. Thus, the use of a final stocking density less than 6.3 kg/m3 should be considered to avoid compromising the stress and health condition and growth of Black Rockfish at this size and temperature range.
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