Artificial reproduction of wild and pond-cultured common tench (Tinca tinca) under controlled conditions

The common tench is an important thermophilic freshwater fish used for aquaculture diversification. This species is farmed in ponds as well as caught in the wild in many European and China. Artificial reproduction under controlled conditions is one of the most important part of modern aquaculture. In this study, two experiments were conducted in which the influence of hormonal agents (Ovopel and Ovaprim - experiment I) and the origin of the spawning stock (wild and pond-cultured - experiment II) on the success of reproduction in terms of ovulation rate (%), latency time (h), pseudo-gonadosomatic index (PGSI, %), hatching rate (%), abnormal larvae rate (%), and spawning efficiency coefficient (Se) were examined. While the wild fish could not reproduce in the absence of hormonal treatment with 0 % ovulation rate. In all tested hormonal treatment allowed to obtain high-quality eggs with hatching rates of over 83 %. Significant differences in latency time were observed among groups from different origins, such as differences in ovulation rate (79 % vs. 90 %, for pond-cultured and wild fish, respectively), PGSI (8.2 vs. 8.9), and hatching rate (63.8 % vs. 84.3 %), which showed significantly better quality in fish from the wild than those from pond culture. This means that when spawners of common tench of various origins are available, it is better to choose spawners from natural waters for artificial reproduction.

Artificial reproduction of the indoor-cultured brackish form of maraena whitefish (Coregonus maraena) under recirculated aquaculture system (RAS) conditions

Maraena whitefish (Coregonus maraena) is a promising coldwater aquaculture species, especially in terms of meat quality. This versatile whitefish species, which inhabits both fresh and brackish waters, including the Baltic Sea, offers promising prospects for aquaculture breeding and cultivation. However, the main problem is the lack of availability of spawners of this species. Therefore, in this study, an attempt was made to raise the spawning stock under controlled conditions and then artificially reproduce the fish to obtain high-quality gametes and then larvae. The conducted research showed that successful culture of maraena whitefish spawners is possible under recirculating aquaculture system (RAS) conditions. The application of proper nutrition and manipulation of environmental conditions allowed the breeding of sexually mature whitefish spawners in less than two years in captivity (meat weight 476 g). Through stimulation of environmental conditions (temperature and photoperiod), it was possible to stimulate the final maturation of gametes of the F1 generation of cultured fish. The use of Ovaprim hormonal stimulation induced 100% of females to ovulate within 10 days of injection, compared to 60% of females in the control group. Additionally, the other examined parameters, such as the pseudogonado-somatic index (PGSI: 11.46% vs. 6.80%), fertilization rate (94.2% vs. 60.1%), embryo survival rate (92.6% vs. 41.1%) and embryo survival rate to the eyed-egg-stage (90.0% vs. 28.0), were significantly higher in the hormonally induced group, finally two times and three times, respectively. The mortality rate of spawners, after spawning and within three months of artificial spawning, was extremely low. The results obtained from the study demonstrate the feasibility of culturing the spawning stock of maraena whitefish in captivity and successfully inducing artificial spawning.