Alginate is rich in bioactive compounds and has been known to act as a stimulator on the innate immune system. The objective of this study is to determine polysaccharide and oligosaccharide alginate yield, that percentage inhibition with a different type of extraction, to evaluate growth performance as well as immune response by oxygen stress tolerance. Thermal heating with oven laboratory at 140oC for 4.5 hr was done to breakdown the polysaccharide into oligosaccharide. The extraction was conducted by maceration, filtration, precipitation, and centrifugation. Factorial design with two factors was implemented to 260 Zebrafish and reared in thirteen aquariums (20 fish per aquarium) for 12 days. Zebrafish was fed at different dose (4.0g; 6.0g; 8.0g.kg-1) and different type of extraction [noEDTA/noKCl; KCl; EDTA and (EDTAandKCl)]. The evaluation of radical scavenging activity was done spectrophotometrically at 515 nm. Results showed that the highest alginate yield either polysaccharide or oligosaccharide was gained from KCL treatments, percentage inhibition (82.61%), growth performance as well as tolerance of stress (P<0.05). The best growth performance was reached in oligosaccharide supplementation at 6.0g.kg-1 treatment. It can be concluded that alginate oliogosaccharide produced by thermal heating enhanced the antioxidant activity, boost the fish’s immune system, proofed by better growth performance and more tolerant to the low oxygen stress.

Fringescale sardinella is one of the largest fishery resources and has the highest economic value in the Savu Sea. The increasing demand for this fish makes it one of the main fishing targets, which allows overfishing to occur. Therefore, the purpose of this study was to determine the population dynamics of sardinella fringescale through growth and mortality, recruitment and exploitation rate of fringescale sardinella in Rote Island in the Savu Sea. A total of 1095 fish sampled from Rote Island were assessed and showed the total length (TL) range from 90 mm to 157 mm. Further, the data were analyzed using FISAT II software with the following results: the length-weight relationship was W= 0.0004L2.2523, while the negative allometric growth pattern and growth equation was Lt = 165.26 (1 - exp1,500 (t + 0.0585)). The age of S. fimbriata consisted of 1-2 cohorts. Recruitment of S. fimbriata in Rote Island occurred throughout the year with the highest peaks in May and August. The size of the first caught fish (Lc) was 96.98 mm TL. The total mortality rate (Z) was 2.41 yr-1, natural mortality (M) was 1.45 yr-1 and fishing mortality (F) was 0.97 yr-1. The exploitation rate of S. fimbriata is estimated at 0.40 yr-1; this implies that the stock does not exceed the optimum exploitation rate (E = 0.5) or that overfishing has not occurred in the Savu Sea. Nevertheless, this study’s results are sufficiently robust to anticipate that the unprecedented overexploitation of S. fimbriata in Rote Island has nearly occurred. Therefore, regular monitoring and surveillance of surface gillnet fishing gear are urgently needed.