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Background. Capoeta erhani Turan, Kottelat et Ekmekçi, 2008 has an economic importance in commercial and recreational fisheries in Turkey. Knowledge of the biology of this species is very scarce. Despite the importance of this species, no research on the population dynamics such as age and growth rates has been conducted. The aim of this study was to determine the age, growth rate, and the relations between the fish size and the otolith size for C. erhani from the Menzelet Reservoir, Turkey. Materials and Methods. This study was carried out seasonally in the Menzelet Reservoir, between January and December 2012. Samples were collected using gill nets with mesh sizes ranging from 18 to 30 mm. Results. A total of 134 otoliths obtained from Capoeta erhani that ranged from 15 to 33.8 cm TL were used in the analyses. The overall male : female ratio (M : F = 1.25 : 1.00) was biased in favour of males. The Mann–Whitney test revealed significant differences between sexes, regarding TL (P < 0.05). The calculated length–weight relations were TL = 0.0097W3.0015 (r2 = 0.986) for females, TL = 0.0054W3.2011 (r2 = 0.975) for males, and TL = 0.0075W3.0892 (r2 = 0.979) for all specimens combined. The von Bertalanffy growth models were L∞ = 33.83 cm (TL), K = 0.964, t0 = –0.573 for females; L∞ = 32.02 cm (TL), K = 0.843, t0 = –0.562 for males; L∞ = 33.85 cm (TL), K = 0.821, t0 = –0.482 for all specimens. Conclusion. This study provides the first information on age, growth, and otolith morphometric parameters of Capoeta erhani. Determining the parameters of C. erhani age and growth rates will lead to the estimates of relevant parameters of population dynamics and to better understanding of the long-term changes of the stock sizes.
Background. Reducing feed cost and the pollution originating from feed have been principal matters in fish nutrition. Mixed feeding schedules have been proposed as one of the methods to reduce both of them and successfully tested in many fish species. The aim of the present study was to determine the mixed feeding schedules′ suitability for culture of rainbow trout. Materials and Methods. Five different feeding schedules were tried by alternating the presentation of a low-protein (28.1%) diet (A) and a high-protein (49.9%) diet (B). The feeding schedules employed were 1A/1B, 1A/2B, 1A/3B, 2A/2B, and 2A/3B where the numerical values refer to the number of days each diet (A and B) was offered continuously. Fish given diets A and B continuously served as controls. Totally, seven dietary treatments were tested in triplicate for 10 weeks. Results. The fish maintained on the different mixed feeding schedules exhibited lower weight gain than those fed continuously on the high-protein diet (P < 0.05). The fish reared on schedule 1A/3B (1 day diet A alternated with 3 days diet B) had similar specific growth rate (SGR), feed conversation ratio (FCR), and protein efficiency ratio (PER) to those fed diet B continuously and was best among all mixed feeding schedules. However, the most cost-effective treatment was 2A/2B. In addition, this group compared to B resulted in significant increase and reduction of phosphorus retention and discharge, respectively (P < 0.05). The treatments significantly effected body moisture, fat- and ash levels (P < 0.05), but not protein. Conclusion. The study shows that mixed feeding schedules are promising for use in rainbow trout culture as they result in feed cost saving and reduced phosphorus discharge in the effluents.
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