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The mackerel scad, Decapterus macarellus, is a one of pelagic fish that holds significant market price for the citizens of West Java. Despite this, there has been a puzzling decrease in catches recently. This study describes the reproductive biology of mackerel scad, D. macarellus, in the southern waters of western Java. Mackerel scad samples were collected once a month from July to December 2022 at three locations: Ciwaru Fish Landing Base, Palabuhanratu Nusantara Fisheries Port, and Binuangeun Fish Landing Base. A total of 1,000 fish specimens were obtained, consisting of 544 males (125–331 mm Fork Length, FL) and 456 females (124–322 mm FL). The number of males and females was imbalanced, indicating a discrepancy in the expected 1:1 ratio. The mackerel scad has a varying reproductive potential, with the number of eggs ranging from 35,391 to 167,915. Mature males and females were found from July to December, with the highest GSI occurring between August and November, indicating reproductive season from July to December and spawning peaks from August to November. The estimated sizes at which males and females reach first maturity were 238 mm and 240 mm, respectively. We recommend increasing gear mesh size to reduce catches of immature individuals, as the first catch was smaller than the size of the first matured gonads.

There had been reports of a significant increase in female fish populations in the Surabaya River, induced by water pollution. This research aims to study the current sex condition and the level of Endocrine Disrupter Chemicals (EDC) in the river fishes after the river cleaning program promoted by the municipality. 420 fish samples from various species were taken from the river during 2017-2018. The fishes were sexed and analyzed their contents of estradiol, phthalate, and chlorpyrifos. The average sex ratio found was nearly normal (Male: Female=52:48), recovered significantly from the previous record in 2013 (16:84). Meanwhile the concentrations of EDC estradiol, phthalate, and chlorpyrifos found were 0.000; 0.033; and 0.037 mg/kg subsequently; except for chlorpyrifos, most of the chemicals were below the residue maximum limit by Indonesia National Standard (SNI).

The coastal ecosystem plays a vital role as essential habitat for juvenile and small marine fishes. This study aimed to analyze juvenile and small-sized fish assemblage in the nearshore habitats of Sumbawa Island. Sampling was carried out in the morning at low tide when new and full moon from November 2020 to January 2021. Five sampling sites were selected based on habitats their adjacency to the river mouth. During the study period, 6349 individuals belonging to 74 species and 37 families were recorded. The number of Ambassis vachellii was the most significant, followed by Hypoatherina temminckii, and Eubleekeria splendens. The highest fish biomass was occupied by E. splendens, followed by Plotosus lineatus, and Planiliza macrolepis. Physico-chemical parameters were not varied between sampling sites, except salinity. Estuaries with vegetated areas have a higher species richness, diversity, and evenness index than the unvegetated area. Juvenile and small-sized fishes varied between sites but not varied between moon phases. Research findings confirm that the nearshore habitat of Sumbawa Island has a significant capacity to support the early life stage of many marine fish species.

Batetangnga River is one of the rivers in West Sulawesi and is well known as an ecotourism area. This preliminary study was performed to reveal fish fauna in the Batetangnga River, West Sulawesi. Ichthyofauna research was conducted in April and May 2021 at two stations in Batetangnga River, namely Rawa Bangun and Butute’neng. During the study period, a total of 14 species belonging to 9 families were identified. No endemic species were found in the study area. Native fish species such as Stiphodon semoni, Butis butis, Glossogobius sp., Glossogobius aereus, Stiphodon sp., Giuris sp, Atule sp. Ambassis miops, Ambassis interrupta, Microphis sp. were recorded. Four alien fishes species were documented i.e. Aplocheilus panchax, Poecilia reticulata, Anabas testudineus, and Oreochromis niloticus. Freshwater fish exploration and efforts to control alien fishes species in west Sulawesi are essential things to be done shortly.

Cikaso and Cimandiri estuaries are well known as the central area of glass eel fisheries in Sukabumi Regency. Local fishermen catch glass eels using two main fishing gears, namely traps and lift nets. Although both fishing gears' target operation is glass eels, many other fish species are also caught as bycatch. The present study aimed to identify glass eels and bycatch ichthyofauna in glass eel fisheries of the Cikaso and Cimandiri estuaries, Sukabumi. The research was carried out monthly from November 2020 to January 2021. Glass eels fishing gears collected a total of 21 fish species belonging to 15 families in both estuaries. According to the percentage ano-dorsal length measurement to total length (AD/TL), 3 species of glass eel were identified, i.e. Anguilla bicolor bicolor, A. nebulosa, and A. marmorata. These three species were the most abundant fish catches in both estuaries. More than 18 bycatch ichthyofauna were recorded and most of them are economically important fish, such as Ambassidae, Eleotridae, Engraulidae, Gobiidae, and Polinemidae. To sustain fishery management, the recording bycatch from glass eel fishery in the Cikaso and Cimandiri estuaries is necessary to be done regularly because they contribute to fishing mortality.