Effect of seawater reared on the nutritional composition and antioxidant activity of edible muscle in smoltified-landlocked masu salmon ( Oncorhynchus masou masou )

A new system of aquaculture for landlocked masu salmon (Oncorhynchus masou masou) has recently been developed in the southern Kyushu Island, Miyazaki, Japan. In this system, moderately silvering fish (smolt salmon) are artificially transported from the freshwater aquaculture ponds to floating seawater fish preserve, and they are then aquacultured during winter season, starting from December to the following April. As a result, their growth and body mass were greatly increased (total length: 21.25 ± 1.04–37.80 ± 3.71 cm; body weight: 81.75 ± 19.91–632.00 ± 172.42 g; condition factor: 8.45 ± 1.44–11.4 ± 0.74). In addition, There was a marked increase in chemical components such as the lipid contents (35.0 ± 9.4–79.2 ± 6.7 mg/g muscle), α-tocopherol (29.0 ± 17.0–178.6 ± 15.0 μg/g muscle), astaxanthin (0.1 ± 0.1–15.2 ± 8.8 μg/g muscle), and anserine (4.75 ± 0.59–10.32 ± 2.68 mg/g muscle) in the seawater-reared landlocked masu salmon. Furthermore, the antioxidant activity of the water soluble extract from the seawater-reared landlocked masu salmon increased from 480.96 ± 79.295–848.99 ± 182.79 μmol Trolox equivalent/g tissue. This new system that involves a short period of aquaculture in seawater not only promotes the growth of landlocked masu salmon, but may also improve its nutritional components and antioxidant activity.