Carp is the most important fish in the Czech Republic with share of 85– 90% on total fish production. Worldwide carp annual production over 4 million tons ranks this species on the fourth the most cultured fish. Still, carp breeding is far beyond the methods used in other fish species (Atlantic salmon, rainbow trout, gilthead seabream and European seabass). The most used method for increasing fish performance is selective breeding. It is based on selecting fish with the best phenotypic value of a given trait, such as growth, resistance to diseases, yield of edible parts, for subsequent artificial reproduction. If the selected trait is sufficiently heritable, the offspring of such fish will show higher performance of a given trait in comparison with the unselected stock. In this way, the desired traits can be continually improved in the next generations as genetic gain is cumulative. However, if we want to increase the yield of edible parts (processed body, filets), the phenotypic value of such traits cannot be ascertained other than by killing and processing of fish. As an alternative, selection based on the performance of siblings is commonly used. However, it requires the killing and processing of part of the fish from a given stock and, above all, the knowledge of the pedigree of each individual in the stock. Under the pond conditions it can be achieved only by methods of molecular biology, and this is disproportionately expensive. For such traits, it is therefore necessary to look for another reliable selection method of suitable candidates.
Scientists from the Faculty of Fisheries and Protection of Waters at the University of South Bohemia in České Budějovice have been involving together with Klatovy fishery corp. in a European project focused on the boosting of European aquaculture in the six main fish species to advanced level through selective breeding. Czech scientists and their foreign colleagues have focused on edible body parts yield in common carp. Carp headless carcass forms 58 – 62% of live fish weight and we assume that the selection might increase the percentage up to 10%. During the fish slaughtering, edible parts percentages were determined as well as thickness of the abdominal wall and the depth of the abdominal cavity by ultrasound. Besides, the muscle fat content was recorded by fatmeter and various lengths, contents and ratios were detected from pictures of fish. These measurements can be done on live fish. Recorded traits were combined with multiple linear regression and their values compared with the real yield of headless carcass and fillets. It was found that the yield of edible parts can be predicted with high accuracy on live fish. In addition, ratio between the thickness of the abdominal muscle and the depth of the body cavity is in direct proportion to the edible parts yield.
All traits are also highly heritable. Thus, yield of edible body parts can be indirectly increased by selecting for values calculated based on ultrasound measurements. There is a theoretical possibility to increase filets yield up to 0.7% per generation. From a practical point of view, this non-invasive method of improving the performance of slaughtering traits could be effectively utilized under the operational conditions of Czech fishery after training the professional staff. However, it is necessary to say that the use of indirect selection has to be verified on other carp breeds and after the realized selection. Both partners would like to continue in the research even after the end of FISHBOOST project. Detailed information can be found in the original article: Prchal, M., Bugeon, J., Vandeputte, M., Kause, A., Vergnet, A., Zhao, J., Gela, A., Haffray, P., Kocour, M., 2018. Potential for genetic improvement of the main slaughter yields in common carp with in vivo morphological predictors. Frontiers in Genetics 9, 283.
