Rapid measurements of fat content in live and slaughtered common carp (Cyprinus carpio L.)

The objective of this study on common carp (Cyprinus carpio) was to obtain and predict the first cross-validated data of the fat content on market size carps using a non-invasive or non-destructive method in situ. The carps (1680 ± 388 g; n = 136) used were from a semi-intensive system and were on a different diet (cereal, pelleted and extruded diet). For the evaluation of the fat content, a Fish Fatmeter FM 692 from Distell.com. (FFM) and a manual measurement of back fat height using a digital calliper were used. For the prediction model, the following basic body measurements (variables) were used: total body length, body length, body height, the width of the body, and the circuit of the body. The body weight, weight of intestines, weight of gonads, weight of hepatopancreas, and fillet yield (%) were measured, and the Fulton coefficient was calculated. The study was focussed on evaluating the applicability of these methods and the accuracy of the obtained result, respectively. Results showed that all the rapid methods had a strong correlation. Multiple regression models with forward selection of variables were used throughout. The final prediction model between predicted and observed values for the fat content for FFM and calliper being adjusted index of determination is shown here (R _adj ²  = 0.88; 5 variables and R _adj ²  = 0.91; 7 variables), respectively.