Appearance and technological characteristics in wild and reared Eurasian perch, Perca fluviatilis (L.)

The purpose of this study was to characterize some quality descriptors of wild Eurasian perch, Perca fluviatilis, taking into account spatial and temporal variability and to situate quality in reared perch in comparison with wild perch variability. Two different natural systems (Leman Lake and the Rhine River) were selected to characterize perch quality variability during an entire biological cycle. Farmed perch quality was studied in relation to the rearing system (extensive, semi-extensive and intensive systems). Using the morphometric, technological and color descriptors, it was shown by Principal Components Analyses (PCA) that in the Rhine River, fish had compact body and caudal fin, large mouth and head and possessed a more reddish caudal fin, in comparison to fish from Leman Lake that are brighter. Seasonal variations were different according to the natural system. In the lacustrian system, fish presented low seasonal variations contrary to the Rhine River system for morphometric and color variables. The technological attributes showed the highest degree of seasonal variation, e.g. fillet yield was high in July. These technological variables were found as being the main discrimination way between fish from the different rearing systems. The intensive rearing system produced perch with higher hepatosomatic index (IH) and perivisceral fat index (IPF) compared with the extensive and semi-extensive rearing systems. Moreover, the more intensive rearing conditions were, the more fat deposits increased. It was also found that reared perch possessed wild-like quality characteristics, except for some technological variables (viscerosomatic index: IV and fillet yield: YF). Furthermore, perch from the semi-extensive system had the most similar quality attributes with fish from the Rhine River. Thus, morphology and color (i.e. color of caudal fin) appeared to be pertinent quality descriptors for wild fish, whereas technological attributes were more adequate for the characterization of reared fish quality. This study also suggested some hypothesis about the direct or indirect relationships between abiotic factors, such as chemical water characteristics, transparency, temperature and quality attributes.