The existence of mackerel scad in Ambon waters, Moluccas Indonesia has decreased from year to year mainly due to the over exploitation. This research aimed to study the biological aspects, in particular were sex ratio, age group and length at first maturity of mackerel scad (Decapterus macarellus) from this area. Sampling was done on September 2016 to July 2017 at the southern waters of Ambon Island. Samples collected were dissected to determine their sex and their gonad maturity level then measured. Bhattacharya method was used to determine age group while Spearman- Kaber method was used to identify length at the first maturity of this species. It was found that mackerel scad in the southern waters of Ambon Island had an equal number of male and female that consists of four age groups with length at first maturity for male and female were 24.9 cm and 24.8 cm, respectively.

─Mackerel scad (Decapterusmacarellus) is one of the small pelagic fish that has important economic value and caught throughout the year around the waters of Ambon. Utilization of these fish is not only profitable economically but also can have a negative impact if not pay attention to aspects of sustainability. The purpose of this research is to know the distribution of long frequency and growth pattern. This research was conducted for six months (September 2016-February 2017 around Ambon waters. Samples of fish analyzed amounted to 1548 individuals. The average length of the minimum fish caught is 9.5 cm and the average size of the maximum length of fish caught is 31.8 cm. Fish growth patterns obtained are isometric.

Length-weight relationship (LWR) species Epinephelus fuscoguttatus Forsskål, 1775 by gender (male and female) were collected from September 2016 to June 2017 in Bobong Taliabu waters, North Maluku, Indonesia. Fish captured using bottom trap, size 80 x 60 x 35 cm with mesh size 5 cm. LWRs of significant male and female E. fuscoguttatus (P<0.05) were calculated as W = 0.0098 L 3.1475 (r 2 = 0.9252), W = 0.0752 L 2.5030 (r 2 = 0.9029), and W = 0.9987 L 1.6789 (r 2 = 0.9093) for both. This study recorded the new maximum length by sex of E. fuscoguttatus.

Skipjack tuna is one pelagic fish that always migrates for a condition with relevant oceanographic factors for their survival, particularly for optimum sea surface temperature and chlorophyll-a. This study conducted with the experimental fishing method from June - November 2018 in the waters of Ternate Island in observation of the optimal condition of oceanographic factors, mainly SST and Chlorophyll-a in the distribution of skipjack tuna. Employing a polynomial regression analysis, the research results show that the sea surface temperature and chlorophyll-a parameters are strictly related to the distribution of the amount of skipjack tuna caught with correlation coefficient value (r) respectively of 0.646 for sea surface temperature and 0.565 for chlorophyll-a. The optimum temperature for the skipjack tuna in the waters of Ternate Island according to the research results ranges from 27.0°C - 30.9°C, while the optimum condition of chlorophyll-a is higher than 0.2 mg/m3-0.35mg/m3, and it seems that every increment of chlorophyll-a content in water indicates an increase of the amount of skipjack tuna catch.

Mackerel scad is a one of small pelagic fish that has important economic value in the waters around Ambon Island. This study aims to determine population dynamics including the length distribution, growth, gonad maturity, mortality and the rate of exploitation of mackerel scad in the waters around Ambon Island. This research was conducted during the period of September 2016 to July 2017. Total fish samples analyzed were 2534 individuals. The total length (TL) of fish caught during the eleven months of the research ranged from 9. 0 -31.9 cm with an average length of fish caught of 20.11 cm. Growth curve formed with the equation: L t = 33.35 [1-exp 0.560 (t + 0.2799]. Gonad I maturity level was 8.13-10 16%, TKG II (gonad II maturity level) was 46.49-49.11% , TKG III (gonad III maturity level) was 16.54-18.93%, TKG IV (gonad IV maturity level) 24.34 -26.02%, and TKG V (gonad V maturity level) was 0.07 -0.21%, F value was 1.36/year with the rate of exploitation (E) of 0.53/year, the total mortality rate (Z) = 2.58/year and the natural mor tality rate (M) = 1.23/year.