Squalene Supplementation as a Novel to Increase PUFA Content in Fish Tissues.

Squalene is an antioxidant that plays an essential role in fat metabolism. The study aimed to assess the effect of squalene supplied in feed on the growth performance, health status, and fatty acid profiles of muscle and liver of Siberian sturgeon, rainbow trout, and Eurasian perch. The experimental feeds containing 0%, 0.5%, and 1.0% squalene were prepared for each fish species. Hematological and biochemical indices, liver histology, and fatty acid profiling of muscle and liver were analyzed. Squalene supplementation was safe for fish, and no negative influence on growth status was observed. However, changes in the values of hematological and biochemical indicators were found, including the level of triglycerides in the blood of rainbow trout, and cholesterol in the blood of Eurasian perch. The addition of squalene influences the nucleocytoplasmic index values in all fish offered feed containing 1% squalene. The retention of squalene in the liver and muscle of experimental Siberian sturgeon was observed in both 0.5% and 1.0% squalene levels of feed. The PUFA and docosahexaenoic acid increase was observed in all fish in groups with squalene addition. Dietary squalene increases the content of PUFAs in tissues of the examined species.

Hepatotoxic effect of dietary phytoestrogens on juvenile cultured Russian sturgeon (Acipenser gueldenstaedtii).

In the last two decades, much controversy has grown over the use of soybean products in aquafeeds, especially for carnivorous fish like sturgeons. One point of discussion is the effect of soybean phytoestrogens on fish health. There are many aspects of phytoestrogen utilization in aquafeeds, therefore, the aim of this study is to verify if common legume phytoestrogens can affect juvenile cultured sturgeon erythrocyte and hepatocyte genotoxicity and cause liver pathology. Russian sturgeons were fed from 100 till 365 dph1 with daidzein, genistein, and coumestrol supplemented diets in concentrations: 10, 0.05 and 0.001 g kg-1 of feed, respectively. The SCGE2 method combined with qPCR of three genes involved in DNA repair and genome maintenance, namely cyp1a1, gaad45a and p53 were analyzed. The results were compared with histopathological evaluation of liver tissue. In fish fed with coumestrol supplemented diet, DNA strand damage was the highest in both erythrocytes and hepatocytes, however, simultaneously the lowest level of oxidative DNA damage was found. Additionally, slightly elevated expression of the p53 gene was observed along with a decreased number of apoptotic hepatocytes, which suggests that low concentration of coumestrol may support DNA repair mechanisms in the liver. Although, daidzein showed a preventive effect only against fibrosis. Isoflavones did not show a significant effect on DNA damage in studied cells. Genistein was found to increase macro- and microvesicular steatosis, portal hepatitis and fibrosis, indicating its negative role in the development of liver injuries. Daidzein alleviated some sturgeon liver damage, especially macrovesicular steatosis and interface hepatitis. However, it increased hepatocyte apoptosis, which may suggest daidzein potentially inducing liver injury, though not manifested by other histopathological lesions. Therefore, it can be concluded that at given concentrations, the tested phytoestrogens did not show clearly hepatoprotective effect in sturgeons.

Muscle Tissue Quality of Raw and Sous-Vide Cooked Wild and Farmed Pikeperch.

The aim of the study was to compare the chemical and fatty acid composition, colour, and sensory quality of wild and farmed pikeperch. Raw wild pikeperch had a higher moisture and ash contents, as well as pH value, but lower fat and protein contents than farmed pikeperch. In sous-vide fillets, a higher fat and a lower protein content were noted in farmed fish. Slight differences in colour attributes between farmed and wild fish affected neither chroma nor hue in raw and sous-vide fillets. Wild and farmed fish fillets prepared using sous-vide were scored similarly in the sensory assessment. Although wild fish had a more beneficial fatty acid composition demonstrated by a higher proportion of polyunsaturated fatty acids, including eicosapentaenoic and docosahexaenoic, a higher fat concentration in farmed pikeperch resulted in obtaining similar or even higher concentration of these fatty acids in sous-vide fillets. Regardless of the origin of pikeperch it might be recommended as a valuable part of a daily diet.

A Comparison of Pneumatic and Hand Stripping of Whitefish (Coregonus lavaretus) Eggs for Artificial Reproduction.

We describe the technique of pneumatic stripping of whitefish (Coregonus lavaretus) eggs with the use of oxygen, nitrogen, and air. Eggs obtained via the traditional method (by pressing the abdominal surfaces) served as a control group. It was established that the gas flow rate during pneumatic stripping should not exceed 0.5 L∙min-1, since higher air flow resulted in increased post-spawning mortality. The pneumatic stripping method of egg collection was no faster than hand stripping; however, the time required per female was more consistent. It was found that the pH of the ovarian fluid obtained during hand and pneumatic stripping was not related to the success rate of fertilization. Pneumatic stripping resulted in a higher quality of collected eggs and a higher and more consistent hatching rate as compared with the hand-stripped samples, regardless of the gas used. The results presented here lead us to recommend the pneumatic method for obtaining eggs from whitefish, since it is a simple, reproducible method and improves the reproductive performance and developmental success of the fish eggs.

Influence of heavy metals and 4-nonylphenol on reproductive function in fish.

Many industrial and agricultural chemicals (including heavy metals and alkylphenols) present in the environment have adverse effects on the reproductive function in fish. Three studies were conducted to assess toxicity of these chemicals towards reproduction of freshwater fish. It was shown that heavy metals added to the diets accumulate in brain tissue of carp, and this accumulation results in inhibition of the secretion of noradrenaline and stimulation of the secretion of dopamine in the hypothalamus. These processes results in a disturbance of hormonal equilibrium of the hypothalamo-pituitary system, which can unfavorably influence the efficiency of artificial spawning in fish. Quality of salmonid and sturgeon sperm was impaired after in vitro exposure to heavy metals. The degree of this toxic effect was species-specific. It was demonstrated that sperm motility parameters appeared to be good indicators of adverse effects of heavy metals fish sperm. The protection role of seminal plasma against toxic effects of heavy metals was suggested for salmonid fish. Oral application of 4-nonylphenol (NP) disrupted reproduction in pikeperch. In juvenile fish a decrease in the percentage of males and an increase of intersex fish was observed in relation to dose of NP and time of exposure to this alkylphenol. Exposure of adult males to the NP led to the reduction in fecundity, milt quality and fertility.