Effects of swimming activity and feed restriction on antioxidant and digestive enzymes in juvenile rainbow trout: Implications for nutritional and exercise strategies in aquaculture.

BACKGROUND: In this study, we investigated the effects of swimming activity and feed restriction on digestion and antioxidant enzyme activities in juvenile rainbow trout (average body weight of 26.54 ± 0.36 g). METHODS: The stomach, liver and kidney tissues were obtained from four distinct groups: the static water group (fish were kept in static water and fed to satiation), the feeding restricted group (fish were kept in static water with a 25% feed restriction), the swimming exercised group (fish were forced to swimming at a flow rate of 1 Body Length per second (BL/s)) and the swimming exercised-feed restricted group (subjected to swimming exercise at a 1 BL/s flow rate along with a 25% feed restriction). We determined the levels of glutathione, lipid peroxidation and the activities of catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and lactate dehydrogenase, as well as the presence of reactive oxygen species in the tissues obtained from the fish. Additionally, the activities of pepsin, protease, lipase and arginase in these tissues were measured. RESULTS: Swimming activity and feed restriction showed different effects on the enzyme activities of the fish in the experimental groups. CONCLUSION: It can be concluded that proper nutrition and exercise positively influence the antioxidant system and enzyme activities in fish, reducing the formation of free radicals. This situation is likely to contribute to the fish's development.

The effect of swimming activity and feed restriction of rainbow trout (Oncorhynchus mykiss) on water quality and fish-plant growth performance in aquaponics.

In this study, we investigated the effects of swimming activity and feed restriction on juvenile rainbow trout (Oncorhynchus mykiss) in decoupled aquaponic systems. Our focus was on assessing their impact on water quality parameters within the aquaponic setup and evaluating the growth performance of the fish, including final weight (FW), condition factor (K), coefficient of variation (c.v.) in weight, specific growth rate (SGR), total feed intake (g/fish), feed conversion rate (FCR), hepatosomatic index (HSI), and viscerosomatic index (VSI), as well as the growth of lettuce (Lactuca sativa L. var. elmaria). The study involved 108 juvenile rainbow trout with an average initial weight of 26.54 ± 0.36 g and 60 ten-day-old lettuce seedlings, over a period of 42 days. We designed four treatment groups, each with three fish tanks: static ad libitum (SA), where fish were in static water conditions and fed to satiation; static restriction (SR), with fish in static water and a 25% feed restriction; current ad libitum (CA), where fish experienced forced swimming at 1 BL s-1; and current restriction (CR), with swimming exercise at 1 BL s-1 and a 25% feed restriction. Using a flow rate of 1 BL s-1 in the tanks for rainbow trout yielded several benefits. Notably, the fish in the CA group exhibited increased feed intake (60 ± 1.78 g fish-1) and enhanced fish growth with an FW of 91.72 ± 0.91 g, compared to the SA group (55.88 ± 0.88 g fish-1 for feed intake and 89.26 ± 0.81 g for FW). In contrast, the CR group showed a reduced feed intake (39.02 ± 2.78 g fish-1) and a lower FW (67.85 ± 1.49 g) compared to the CA group. In addition, the CA group demonstrated positive contributions to fish development with a reduced HSI (1.26 ± 0.02) in comparison to the SA group (1.56 ± 0.14). Inadequate nutrient provisioning in the SR and CR groups negatively impacted fish growth and system efficiency. Our findings suggest that optimizing water flow and feed benefits fish and plants and enhances system sustainability.

Level of in vitro storage of the European catfish (Silurus glanis L.) eggs at different temperatures.

European catfish (Silurus glanis) is a commercially important freshwater fish originating from Eastern Europe. The objective of this study was to examine the short-term storage of its eggs especially in relation to maintaining a low level of malformation in newly hatched fry. The eggs from freshly spawned individuals were stored separately in cell incubators at 17 and 22 °C under aerobic conditions. Changes in fertilization, hatching, and malformation were examined in eggs stored at 1, 3, 5, and 7 h post-stripping. The sperm used for fertilization showed very good motility rates (84-90%) and curvilinear velocity (110-125 µm/s), and straight-line velocity did not drop below 77 µm/s. For all females, a temperature of 17 °C was better than 22 °C for egg storage in vitro. Egg fertilization and total hatching decreased rapidly after 7 h storage at 17 °C. The storage time of eggs in vitro to fertilization should therefore not exceed 5 h at 17 °C. In all females, there was no difference in the total number of eggs hatching between 1 and 3 h of egg storage at 17 °C. The storage time of eggs did not correlate with the level of malformations of the fry. However, the level of hatching and malformations was clearly affected by the storage temperature of eggs when it was > 17 °C. Analysis showed that the storage time of eggs, temperature of storage, and individual females had a significant influence on fertilization and total hatching rates. Regression analysis confirmed a low correlation of fertilization and hatching rates with storage time of eggs.

Sperm quality analysis of normal season (NG) and out-season by photoperiod manipulation (PG) of male rainbow trout broodstock (Oncorhynchus mykiss).

Sperm quality parameters in rainbow trout (Oncorhynchus mykiss) were investigated during normal season spawning (November-January) and out-season spawning (July-August) treated with artificial photoperiod manipulation. Normal spawning males (n = 15) were kept in an open concrete pond under natural condition. Out-season spawning males (n = 15) were treated with artificial LED light (50 lm/m2) in a closed concrete pond. In these two experimental groups, five fish were used in each of three spawning periods. The mean weight and body length of males (2 + years, n = 30) were 1213.43 ± 39.43 g and 45.08 ± 0.62 cm, respectively. Sperms were collected from July to August 2016 in the out-season spawning or photoperiod-manipulated group (PG) (water temperature 14.21 ± 0.31 °C) and from December 2016 to January 2017, in the normal season spawning group (NG) (water temperature 8.81 ± 1.03 °C). Volume of sperm, osmolality of seminal plasma, density of sperm, percentage of motile spermatozoa (MOT), curvilinear velocity (VCL), and duration of motility were measured for each male. Seminal plasma osmolality, density of sperm, and the motility of duration were 358.47 ± 37.24 and 308.87 ± 44.09, 4.37 ± 2.10 and 9.8 ± 1.56, and 8.8 ± 2.42 and 24.6 ± 6.76 in PG and NG, respectively. Fertilization rate was 37.79 ± 9.37% and 94.51 ± 1.33% in PG and NG, respectively. Sperm quality parameters showed significant differences in most of the cases (p < 0.05) and fertilization rate at eyed egg stage (150-160 degree-days) was significantly higher in normal season spawning group than the photoperiod-manipulated group (p < 0.05). Though the rate of fertilization was low in out-season, it was able to get enough gametes in summer using only artificial light having no changes in other parameters.