Bigeye tuna is an important fish resource in the Indian Ocean. This species like other tuna species needs to be managed properly in both national and international levels. Therefore some data and information on population structure and bioreproduction are required for management purpose. The current research was conducted to identify the population structure and bioreproduction of bigeye tuna (<em>Thunnus obesus</em>) in west off Sumatera and south off Java and Nusa Tenggara of Indian Ocean where tuna fishing spots are important. This research was based on catch landed by fishermen from the Indian Ocean during 2010. Analysis of population structure was done using DNA genetic analyses and bioreproduction by using histology technique. Results show that the population structure of the bigeye tuna in the Indian Ocean consisted of two different sub populations namely sub population of west off Sumatra and sub population of south of Java and Nusa Tenggara waters. Most of catch (about 39%) was categorized as immature fish (GI I). The immature fish was mostly found in west off Sumatera waters, meanwhile the catch in south off Java and Nusa Tenggara waters was mostly categorized as mature fish. This result may indicate that south off Java and Nusa Tenggara waters is a spawning ground of the bigeye tuna.

This study aims to find scientific data concerning distribution pattern of R. argyrotaenia, catch composition of R. argyrotaenia including length frequency data, fishing peak season, spawning season, and abiotic characteristics of aquatic environment, such as life of R. argyrotaenia. The findings indicate that distribution pattern of R. argyrotaenia during rainy season (January-April) is scattered in main river, tributary, and marsh (flood plain), during dry season (May-August), position of fish is in main river and tributary, while in transitional months (September-December), fish is concentrated in main river. Fishing peak season occurs in April, May, June, and July reaching average haul range of 9.98 kg/month + 0.62-12.63 kg/month + 1.08. Based on Analysis of Progression Model by utilizing FISAT II on length-based data of R. argyrotaenia, there found three cohorts by average length of 65.76 ISSN 2157-6092 2014 www.macrothink.org/jee 118 mm + 9.0, 116.13 mm + 15.0, and 156.63 mm + 4.7. Referred to analysis of the Von Bartalanffy growth curve, it is known that inital spawning season of R. argyrotaenia alleged that the peak spawning season occurs in September, October, November and December reaching value of Linf=173.25, K=0.510/year, and t0=0.02. R. argyrotaenia lives in habitat where average temperature is 25.5 oC + 0.12 -31.6 oC + 0.12, current speed of 0.06 ms-1+ 0.02 -0.27ms-1 + 0.02, pH of 4.23 + 0.03 -6.74 + 0.05, and DO of 4.2 mg l-1 + 0.06 -7.5 mg l-1 + 0.10. Journal of Environment and Ecology

Fringescale sardine (Sardinella fimbriata) is small pelagic fish that has an increasing production every year. This can trigger the occurrence of overfishing, so it is necessary to study the biology and dynamic population of fish. This research was conducted in December 2016 -May 2017. The purpose of this research was to determine the biological aspects and population dynamic of fringescale sardine (S. fimbriata) in Bali Strait. Samples were obtained from surface gillnet landed in Muncar fishing port, with 1471 of fish. Results showed that sex ratio was about balanced with the proportion of 55% male and 45% female. Length and weight relationship was negative allometric patterns. Length of first mature (Lm) male and female was 11.95 cm and 10.79 cm respectively. Based on dynamics population analysis it was found that length at first capture (Lc) was 10.44 cm. While K, L∞ and t0 were 0.54/year, 19.6 cm and -0.149 year respectively. In addition there was only one peak recruitment occured in 7th month of recruitment pattern. Another analysis indicated that a value of natural mortality (M) was 1.38 with sea surface temperature (SST) of 29.45°C. According to length frequency data total mortality (Z) was 6.41 so that fishing mortality (F) was calculated to be 5.03. Hence value of exploitation rate (E) was 0.79. It can be concluded that the fisheries resources status is categorized as overfishing.

Little tuna landed there are three types: Euthynnus affinis, Auxis thazard, Auxis rochei. The analysis shows the condition of the resource indicates the condition Over Exploited. Length and weight relationship tuna (Auxis thazard) total positive allometric Length of first caught fish (Lc) of 27.08 cm, The length at first maturity (Lm) 28.39 cm Lt = 35.40 {1 − e −0.58(t + 0.26)}, total mortality (Z) = 4.08 per year, Fishing mortality (F) = 2.91 per year, natural mortality (M) = 1.17 per year, with the Exploitation rate (E) = 0.71 per year which, if E> 0.5 is overfishing. The relationship between length and weight of Tuna (Euthynnus affinis) was unsexed W = 0.1078 L 3.48. The value of Lc and Lm were 37.51 cm, 38.43 cm, and 40.17 cm respectively. Von Bertalanffy growth Lt = 72.50 {1 − e −0.11(t +0.27)} equation of this study was. The rate of total mortality (Z), natural (M), and catch (F) were respectively 0.56, 1.74 and 0.01. The peak season tuna catch in PPN Prigi was occurred in September (515.865%) with the low season occurred in January (1.244%). As for UPT PP Muncar, the peak season cob arrest took place in March (316.315%) with famine in February (6,651%). Little Tuna food was consist of 7 groups, namely: small fish, shrimp, Ascomycota, Chloromonadophyta, Chyanophyta, Chrysophyta, and Chlorophyta.

Study on the population dynamic of endeavour shrimp (M. etegans) was conducted in the south coast of Java baied on data collected during a period of November 2002to october 2003. The purpose of the study is to identify biological and population parameters of the endeavour shrimp. Results shows that the size at firts maturity of endeavor shrimp was 32.6 mm in carapace length. Sex ratio of males and females was 1.0;1'7' The chi square test indicated that comparison of male and female of the endeavour shrimp was significantly different' It means that there was imbalance in number between males and females. A number of 554 females were examined, resulting 60% were immature ,and 40o/o were mature. The spawning season of endeavour shrimp in south coast of Java occurs throughout the year with two peaks, January (north west monsoon) and August (south east monsoon). The growth parameter of endeavour shrimp was 1'5 per year with maximum carapace Lngth (L"")of 51.8 mm. Instantenous total mortality (Z) and natural mortality (M) rates were 4.53 and 1.15 per yeai, resiiectively. While the respective fishing mortality (F) and exploitation rate (E) were 3.38 and 0'75 per y""itir" respeitivelyto mointain the sustainability of t-his shrimp fisheries resources. The exploitation rate of endeavour shrimp in south coast of Java was high. This suggests that fishing effort of the endeavour shrimp in that waters should be reduced'