Introduction
Common carp (Cyprinus carpio L.) is one of the most important fish species in freshwater aquaculture worldwide (FAO, 2022). It is of great importance in several European countries and will continue to be a significant fish species in areas where it is traditionally farmed. In Bavaria, carps are generally farmed using traditional farming methods in extensive or semi-intensive eathern ponds, with a combination of natural feed sources and supplemental feeding. Due to the traditional culinary preparation of marketable carp in the region of Franconia - called "half baked carp", marketable carps weighing between 1000 g and 1500 g are in high demand. To achieve this weight, it has traditionally been common practice in Bavaria, given the prevailing climatic conditions, to produce marketable carp in a three summers cycle.
Climate change might be altering the framework for this traditional pond farming in Bavaria. The average annual temperature in Bavaria rose by + 1.9 °C between 1951 and 2019 (LfU, 2022). Species adapted to higher water temperatures, such as cyprinids, could benefit from higher water temperatures. Due to current climate change (longer growing periods and shorter winter rest periods), the question arises whether the traditional three summers cycle in Bavarian carp pond farming can be adapted to the changing conditions. Therefore, the aim of this study was to clarify, if carp in Bavaria can be raised to market size in just two summers. This study therefore also aimed to compare the quality of carp meat from carp farmed in two summers- and traditional three summers -cycle.
Material and Methods
The trial on the two-summer production cycle was conducted at the Bavarian State Research Center for Agriculture, Institute for Fisheries, Department for Carp Farming (Middle Franconia, Germany) in 2023 and 2024. The experimental ponds were managed according to traditional pond aquaculture practice, and carps (mirror carps) from the own breeding and own fish stocks (K1) were used for the two summers production cycle in eathern ponds. To compare carcass and meat quality of two summers old marketable carps, traditional three summers old marketable carps were also produced from the institute's own K2 stocks in eathern ponds. Carp stocks were supplementaly fed with pressed triticale (x Triticosecale Wittmack) and grounded peas (Pisum sativum L.).
To compare the carcass- and meat -quality between two- and three-summers old marketable carps, fish with a nearly the same body weight and fat content were selected. These two summers old marketable carps had average wieght of 1646 ± 181 g and average fat content of 4.0 ± 1.0 % (n = 20). These three summers old marketable carps had average wieght of 1638 ± 156 g and average fat content of 4.0 ± 1.5 % (n = 20).
Results and Discussion
The K1 - stocks had average weight of 124 ± 20 g (n = 150) within the first production year from K0 to K1 in year 2023. The following second production year (2024) of K1 up to marketable carps in 2024 clearly shows that under current climatic conditions and with traditional pond management in Middle Franconia, it is possible to produce marketable carps in eathern ponds in just two years. These two summers old marketable carps had an average weight of 1700 ± 264 g (n = 108).
The results of the carcass examination of selected two summers old marketable carps show a significantly (p < 0.05, n = 20) higher fillet yield with skin and fillet thickness (excluding skin) compare to selected three summers old marketable carps. Contrarywise the gonadosomatic index (GSI) was significantly (p < 0.001, n = 20) higher in these three summers old carps than in these two summers old carps. The age has a strong effect on gonad development of the European carp (Hulata et al. 1974). However, differences of the meat quality (connective tissue, firmness, colour, sensory evaluation, cooking- and baking -losses) between these three summers old marketable carps and these two summers old marketable carps were none or marginal.
Acknowledgment
This work was funded by the Bavarian State Ministry of Food, Agriculture, Forestry and Tourism.
References
FAO. 2022. The State of World Fisheries and Aquaculture 2022. Towards Blue Transformation. Rome, FAO. https://doi.org/10.4060/cc0461en
Hulata, G., Moav, R. and Wohlfarth, G. 1974. The relationship of gonad and egg size to weight and age in the European and Chinese races of the common carp Cyprinus carpio L.. Journal of Fish Biology, 6: 745-758. https://doi.org/10.1111/j.1095-8649.1974.tb05116.x
LfU. 2022. Bayerns Klima im Wandel - Heute und in der Zukunft. Bayerisches Landesamt f��r Umwelt (LfU). https://www.bestellen.bayern.de/lfu_klima_00173