Pre‑spawning fat and trace metals in Diplodus sargus (Pisces, Sparidae) and possible relationship with the abnormally tough syndrome (ATS)

Abstract

This research aimed to explore the variability in the distribution of muscle, perivisceral, and retroperitoneal fat in Diplodus sargus during the pre-spawning period (the period of maximum accumulation of fat reserves) and its possible relationship with the abnormally tough specimen syndrome (ATS) affecting this species. Since pollutants accumulate in adipose tissue, trace metal load in the fattest specimens were also analyzed. Muscle fat content and abdominal fat were highly correlated, and larger individuals had more abundant abdominal fat. However, given its great variability (26% of the specimens had no abdominal fat at all), abdominal fat is likely a transitional fat to be quickly transferred to other tissues. The liver appeared to have a minor role as a fat deposit in D. sargus since HSI varied relatively little. None of the fishes without lipidic reserves were ATS individuals; by contrast, the only ATS individual found, a 28 cm male, showed a muscle fat content above the observed average and one of the highest amounts of perivisceral and retroperitoneal fat. Therefore, we conclude that flesh hardness is not directly related to the low lipid reserves. However, this ATS individual showed a very high liver copper concentration, suggesting a potential link between fat content, copper concentration, and ATS syndrome that should be explored in the future