Abstract
The objective of this study was to verify which morphometric measures and ratios are more directly associated with the weight and body yields of rounded fish. A total of 225 specimens of rounded fish (59 pacus, 61 tambaquis, 52 tambacus and 53 paquis) with average weight of 972.43 g (±115.52 g) were sampled, stunned, slaughtered, weighed, measured, and processed for morphometric and processing yield analysis. The morphometric measures taken were: standard length (CP); head length (CC); head height (AC); body height (A1); and body width (L1). For completeness, the following morphometric ratios were calculated: CC/CP, AC/CP, A1/CP, L1/CP, CC/A1, AC/A1, L1/A1, CC/AC and L1/CC. The yields of carcass, filet, rib and filet with rib were estimated after processing. Initially, a "stepwise" procedure was performed in order to eliminate multicollinearity problems among the morphometric variables, and the phenotypic correlations were then calculated for the dependent variables (weight and body yields) and independent variables (morphometric measurements and ratios). These correlations were later deployed in direct and indirect effects through path analysis, and the direct and indirect contributions of each variable were measured in percentage terms. The CC and A1 measures were important for determining the weight of rounded fish. The CC/A1 ratio was the variable most directly associated with carcass yield. For filet, filet with rib and rib yields, the L1/CC ratio was found to be more appropriate and can be used directly.
Highlights
Round fish are easy to cultivate and present good animal performance, meat of excellent quality, low demand for water quality, resistance to disease and are valued in recreational fishing (Carneiro & Abimorad, 2004; Jomori et al, 2008; Signor et al, 2010), representing 82% of the total native fish reared in Brazil (IBAMA, 2005).The fish processing industry places no value on the fish carcass characteristics, and still bases business decisions with its suppliers on the fish weight
The “stepwise” procedure resulted in the inclusion of the following morphometric measures and ratios in the path analysis for each response variable studied: WEIGHT = head length (HL), body height (BH), body width (BW), BH/standard length (SL), BW/SL, BW/HL; carcass yield = HH, BH, BW, HH/SL, HL/BH, BW/BH; RCOST = HH/SL, BH/SL, BW/SL, HH/BH, BW/HL; filet with rib yield = HH, BW/SL, HL/HH, BW/HL; filet yield = HH, HL/HH, BW/HL
Sang et al (2009) report that body measurements were effective in the estimation of weight and body yield in catfish Pangasianodon hypophthalmus
Summary
Round fish (species and hybrids of the Colossoma and Piaractus genera) are easy to cultivate and present good animal performance, meat of excellent quality, low demand for water quality, resistance to disease and are valued in recreational fishing (Carneiro & Abimorad, 2004; Jomori et al, 2008; Signor et al, 2010), representing 82% of the total native fish reared in Brazil (IBAMA, 2005).The fish processing industry places no value on the fish carcass characteristics, and still bases business decisions with its suppliers on the fish weight. Studies of fish body yields have great importance in estimates of productivity, by reducing costs and increasing profits for both farmer and industry (Souza et al, 1999). Correlation of body yields with morphometric measurements has been the subject of several studies for some fish species (Freato et al, 2005; Diodatti et al, 2008). This simple correlation only makes it possible to evaluate the direction and magnitude of the association between two characters, without providing necessary information concerning the direct and indirect effects of a group of characters in relation to a dependent variable of major importance (Cruz, 2001)
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