Effect of Photoperiod Manipulation on Spawning Time and Performance of Turbot (Scophthalmus maximus)

Temperature and photoperiod are known as the main stimuli of seasonal reproduction in fish. Turbot (Scophthalmus maximus) is a spring spawning teleost fish species with a promising aquaculture potential and high market value. This study was conducted to assess the effect of photoperiod manipulation on spawning time and spawning performance of turbot. A total of 28 mature turbots from the Black Sea population were subjected to manipulated photoperiod (a photoperiod regime that fish would naturally receive three months later) and natural photoperiod for almost a year. While the fish exposed to natural photoperiod spawned in May, the fish exposed to manipulated photoperiod spawned almost three months earlier compared to the natural photoperiod group. Reproductive and hatchery performance of the manipulated photoperiod and natural photoperiod groups were similar. It can be emphasized that photoperiod play an important role in accelerating maturation and spawning. The findings of this study could be implemented in the turbot aquaculture industry to advance production.

THE EFFECTS OF PHOTOPERIOD MANIPULATION ON MORPHO-ANATOMY AND GROWTH OF Clarias gariepinus

Changing in photoperiod duration will affects the physiology of fish in general. A study aims to understand the effects of photoperiod manipulation towards C. gariepinus morpho-anatomy and growth was conducted on March–May 2018. The fishes were reared in fiber tanks (140 x 60 x 40 cm) that was filled with water and completed with a circulatory system. Treatments applied were Control (natural photoperiod), 24G (24 hours dark), 18G6T (18 hours dark and 6 hours light), and 6G18T (6 hours dark and 18 hours light). The fishes were sampled once/14 days, 4 fishes/ aquarium/sampling. Parameters measured were length-weight relationship, condition factor, hepatosomatic index (HSI), viscerasomatic index (VSI), absolute length and weight, food conversion ratio (FCR), gonad development and body protein/fat. Results shown that photoperiod manipulation affects C. gariepinus morpho-anatomy and growth. The highest growth parameters and morpho-anotomy index were found in fish reared in 18G6T. By the end of the experiment, the b value of length-weight relationship was 3.3205, absolute weight and length were 86.70 g and 17.23 cm, condition factor was 0.84, VSI was 25.31%, HSI was 11.42%, FCR was 1.43, and body protein and fat was 48.40% and 50.38%. In the fish reared in 24G treatment, b was 1.9262, 52.13 g BW and 14.19 cm SL, condition factor was 0.80, VSI was 23.30%, HSI was 9.38%, FCR was 2.47, and body protein and fat was 48.08% and 49.53%. In the fish reared in 6G18T, b was 2.6903,49.45 g BW and 13.79 cm SL, condition factor was 0.79, VSI was 23.30%, HSI was 6.80%, FCR was 1.91, and body protein and fat was 46.64% and 49.00%. Fish reared in natural photoperiod (control) shown the lowest results b was 2.0418, 51.68 g BW and 14.21 cm SL, condition factor was 0.79, VSI was 19.58%, HSI was 6.96%, FCR was 2.20, and body protein and fat was 43.95% and 47.77%.Early developing gonad (1st maturity stage) was only found in fish reared in 18G6T. Based on data obtained it can be concluded that the photoperiod manipulation affect the morpho-anatomy and growth of C. gariepinus.