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    Evaluation of isotopic signature of mucilage in the benthic food web in the Çanakkale Strait
    (Universitatea din Oradea, 2022) Gürkan, Selin Ertürk; Acar, Seçil; Gürkan, Mert; Özdilek, Şükran Yalçin
    The mucilage formation, which emerged in the Marmara Sea in November 2020, was soon seen in the Çanakkale Strait and became effective in different locations of the strait in a short time. In this study, the place of mucilage in the food web as a food source and the percentage of mucilage in the food web of warty crab (Eriphia verrucosa), which is a benthic species, was determined by the stable isotope method. For this purpose, E. verrucosa was sampled from a mucilage-affected area of the Çanakkale Strait in July 2021. In addition, sediment samples were collected to sort out macrophyte samples and macroinvertebrate samples, which could be possible food sources of the species. Finally, the pelagic and benthic mucilage samples were also taken and brought to the laboratory in the cold chain. The stable isotope analyses of all samples were made and evaluated. The results showed that mucilage from both layers joined the food web and that benthic mucilage, in particular, contributed to the diet of a benthic species, E. verrucosa. The possible contribution of mucilage, which has been determined to be included in the diet of benthic organisms with its high bacterial density, is also a concern for the diet of fish species that are consumed more frequently by humans. © 2022 Universitatea din Oradea. All rights reserved.
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    Evaluation of oregano (Origanum vulgare) essential oil supplementation on growth performance, digestive enzymes, intestinal histomorphology and gut microbiota of Black Sea salmon, Salmo labrax
    (Sciendo, 2021) Özel, Osman Tolga; Çakmak, Eyüp; Gürkan, Selin Ertürk; Coşkun, İsa; Türe, Mustafa
    This study aimed to determine the effect of dietary oregano (Origanum vulgare) essential oil (EO) on the growth performance, digestive enzyme activity, intestinal histomorphology, and intestinal microbiota of the Black Sea salmon juvenile (Salmo labrax). Fish were fed diets different levels of oregano EO such as 50, 100, 200, and 400 mg kg-1. For this purpose, a total of 675 fish were distributed randomly in triplicate into 5 experiment groups in 15 experiment tanks. Fish with average initial weights of 3.52±0.01 g were fed by hand at 3% of live weight for 90 days. At the end of the study, feeding with oregano EO supplementation did not significantly affect the growth performance of fish. Except for pepsin, there were no significant differences in the activity of digestive enzymes among the control and oregano EO groups. Besides, oregano EO at the doses of 50 or 400 mg kg-1 may have the potential to increase the surface area required for digestion by increasing intestinal villi length. Moreover, all doses of oregano EO showed antimicrobial properties by decreasing the count of lactic acid bacteria in the intestine. Supplementation with 100 and 200 mg kg-1 oregano EO in diets decreased the total coliform, Escherichia coli and lactic acid bacteria counts when compared to the control group. The results showed that oregano EO may positively affect digestion and absorption without adverse effects on the growth performance of Black Sea salmon juvenile.
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    Monitoring of Enzymatic Activity in the Gastrointestinal Tract of Black Sea Salmon (Salmo labrax Pallas, 1814)
    (2022) Özel, Osman; Gürkan, Selin Ertürk
    In this study, it was aimed to determine the activity of digestive enzymes at different time intervals after-feeding throughout the gastrointestinal tract of Black Sea salmon (Salmo labrax). The study was conducted at freshwater recirculating aquaculture systems (RAS). The fish were fed by hand up to satiation for 60 days with diets containing 46.25% protein and 14.90% lipid. The fish gastrointestinal tract including stomach, anterior (with pyloric caeca), middle and posterior sections were taken together at 45th minute, 3rd, 6th, 12th, 24th, 48th, 72nd, and 96th hours post-feeding. The tissues were were stored at -80°C until analyzed. In terms of digestive enzyme activity, at the end of the study, anterior and middle intestine sections had the highest level at 3rd-hour post-feeding. Similarly, pepsin, trypsin, and lipase in the stomach had the highest activity at 3rd-hour post-feeding. However, amylase in the stomach was the highest level at 45th minute and 3rd-hour post-feeding. At 3rd-hours post-feeding, the pepsin in the stomach, the trypsin, and lipase in the anterior section, and the amylase in the middle intestine had the highest levels. Moreover, the correlations between these enzymes were strong in the positive direction. Also, the difference in pepsin, trypsin, amylase, and lipase levels in the samples dissected at different time intervals after feeding was statistically significant. Our results revealed that stomach, anterior, middle, and posterior sections in the gastrointestinal tract of Black Sea salmon had enzyme activity in the different levels, and enzyme activity of these sections changed depending on time post-feeding.
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    Time-dependent change of the digestive enzyme activity of Black Sea salmon (Salmo labrax Pallas, 1814) fed at suboptimal temperature
    (2021) Özel, Osman; Gürkan, Selin Ertürk
    The present study conducted at 10.21±0.27°C water temperature in freshwater recirculating aquaculture systems (RAS) to observe the temporal variations in the digestive enzyme activities including pepsin, trypsin, amylase and lipase of Black Sea salmon (Salmo labrax). Seventh filial generation (F7) of Black Sea salmon (Salmo labrax) with average initial weights of 69.85±10.08 g were by hand fed three times daily until apparent satiation. At the end of the 75-day trial the samples were dissected that reached a weight of 179.17±31.08 g at 45th minute, 3rd, 6th, 12th, 24th, 36th, 48th, 72nd and 96nd hours post feeding. In all enzyme groups, the third hour after feeding was recorded as the time when the highest levels were observed. However, enzyme activities decreased gradually as the time after feeding was prolonged. In the nutrition studies to be conducted at a suboptimal temperature in RAS, gut sampling of Black Sea salmon can be taken at 3rd hour after feeding. For a better understanding of digestive enzyme activity for this species, however, different sections of the digestive system should be comprehensively monitored including different temperature conditions.