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Abstract Hilsa shad Tenualosa ilisha, locally known as terebuk fish, is found in Labuhanbatu waters, Northern Sumatra, Indonesia. The population of this species has decreased significantly due to overexploitation. Despite its commercial importance, there is currently no information on the reproductive biology of this species in the region. This information is important for the development of sustainable fishing and conservation strategies. Therefore, this study aimed to examine the reproductive biology of T. ilisha in Labuhanbatu waters, Northern Sumatra, Indonesia. Observations were conducted for a year, from January to December 2019, in the Barumun River, Labuhanbatu Regency. Fish samples were caught using gill nets with three mesh sizes (2, 3, and 4 inches) operated by a boat. The samples were analyzed for sex, gonad development stage (GDS), gonadosomatic index (GSI), and fecundity. A total of 1,914 fish were recorded, including 1,428 (74.5%) males and 486 (25.4%) females. Samples with GDS III and IV were predominant among both males and females throughout the year. The highest GSI was recorded in January and March with values of 1.6% and 11.3%, respectively. The fecundity of female fish ranged from 81,450 to 245,267 eggs/fish, whereas the number of males was predominant in every month of sampling. Tenualosa ilisha spawns throughout the year, with the peak spawning season occurring from January to March. Strengthening the management implications of seasonal fishing bans during the spawning peak (January–March) may protect females. Resumo A sardinha Tenualosa ilisha, conhecida localmente como peixe terebuk, é encontrada nas águas de Labuhanbatu, Norte de Sumatra, Indonésia. A população dessa espécie diminuiu significativamente devido à sobre-exploração. Apesar de sua importância comercial, atualmente não há informações sobre a biologia reprodutiva dessa espécie na região. Essas informações são importantes para o desenvolvimento de estratégias de pesca sustentável e conservação. Portanto, este estudo teve como objetivo examinar a biologia reprodutiva de T. ilisha nas águas de Labuhanbatu, Norte de Sumatra, Indonésia. As observações foram realizadas ao longo de um ano, de janeiro a dezembro de 2019, no rio Barumun, Regência de Labuhanbatu. As amostras de peixes foram capturadas com redes de emalhar com três tamanhos de malha (2, 3 e 4 polegadas) operadas por uma embarcação. As amostras foram analisadas quanto ao sexo, estágio de desenvolvimento gonadal (GDS), índice gonadossomático (GSI) e fecundidade. Um total de 1.914 peixes foi registrado, incluindo 1.428 (74,5%) machos e 486 (25,4%) fêmeas. Amostras com GDS III e IV foram predominantes tanto entre machos quanto entre fêmeas ao longo do ano. Os maiores valores de GSI foram registrados em janeiro e março, com 1,6% e 11,3%, respectivamente. A fecundidade das fêmeas variou de 81.450 a 245.267 ovos/peixe, enquanto o número de machos foi predominante em todos os meses de amostragem. Tenualosa ilisha desova ao longo de todo o ano, com pico de desova entre janeiro e março. O fortalecimento das implicações de manejo, como a proibição sazonal da pesca durante o pico de desova (janeiro–março), pode proteger as fêmeas.

Abstract Betta dennisyongi and Betta rubra are ornamental fish native to Aceh waters, facing a decline in population due to overexploitation and environmental changes. Therefore, this research aimed to obtain information regarding the reproduction of B. dennisyongi and B. rubra. The study was conducted from January to December 2020, with B. dennisyongi and B. rubra samples collected from Nagan Raya Regency and Aceh Besar, respectively. Approximately 1,099 Betta fish samples were successfully collected, comprising 600 B. dennisyongi and 499 B. rubra. The results showed that sex ratio (male:female) analysis had 1:5 and 1:6 for B. dennisyongi and B. rubra, respectively, indicating a predominance of female. Further analysis showed that only 15% of female B. dennisyongi samples had mature gonads out of 505 and 3.7% of male among 95 B. dennisyongi. Female of B. dennisyongi showed first mature gonads at a size of 3.86 cm, while male had maturity at 3.99 cm. For B. rubra, only 11.1% of female and 26.9% of male samples showed mature gonads out of 432 and 67, respectively. Female of B. rubra first matured gonads at a size of 3.86 cm, while male had maturity at 3.90 cm. Reproductive analysis showed that both species were continuous spawners in the year, as indicated by mature gonads in each month of observation, with fluctuating percentages. The peak spawning period for B. dennisyongi occurred in October, while B. rubra was observed in January. Consequently, it was recommended not to catch these species during their spawning months to maintain the sustainability of these endangered species. Resumo Betta dennisyongi e Betta rubra são peixes ornamentais nativos das águas de Aceh, que enfrentam um declínio populacional devido à superexploração e mudanças ambientais. Portanto, esta pesquisa teve como objetivo obter informações sobre a reprodução dessas duas espécies. O estudo foi conduzido de janeiro a dezembro de 2020, com amostras de B. dennisyongi e B. rubra coletadas em Nagan Raya Regency e Aceh Besar, respectivamente. Aproximadamente 1.099 amostras de peixes Betta foram coletadas, compreendendo 600 B. dennisyongi e 499 B. rubra. Os resultados mostraram que a análise da proporção sexual (macho:fêmea) foi de 1:5 e 1:6 para B. dennisyongi e B. rubra, respectivamente, indicando uma predominância de fêmeas. Análises posteriores mostraram que apenas 15% das amostras de fêmeas de B. dennisyongi tinham gônadas maduras (de um total de 505), enquanto entre os 95 machos analisados, apenas 3,7% estavam sexualmente maduros. A fêmea de B. dennisyongi apresentou as primeiras gônadas maduras com um tamanho de 3,86 cm, enquanto o macho teve maturidade com 3,99 cm. Para B. rubra, apenas 11,1% das amostras de fêmeas e 26,9% dos machos apresentaram gônadas maduras de 432 e 67, respectivamente. A fêmea de B. rubra apresentou as primeiras gônadas maduras com um tamanho de 3,86 cm, enquanto o macho teve maturidade com 3,90 cm. A análise reprodutiva mostrou que ambas as espécies foram reprodutoras contínuas ao longo do ano, conforme indicado pelas gônadas maduras em cada mês de observação, com percentuais flutuantes. O pico do período de desova para B. dennisyongi ocorreu em outubro, enquanto o de B. rubra se deu em janeiro. Recomenda-se não capturar ambas as espécies durante os meses de desova, para manter a sustentabilidade dessas espécies ameaçadas.

The Betta broodfish supply in Indonesia majorly comes from wild populations and fetches a higher price compared to hatchery cross-breeds, especially Betta rubra. This condition exerts pressure on the wild populations. Therefore, this study aims to examine the diversity, distribution, and conservation status of Betta fish species list in the study area. A total of 422 Betta fishes were collected from January 2019 to January 2021 from 19 of 59 sampling locations surveyed, consisting of four species, namely, Betta imbellis (TL: 14.09-31.98 mm; BW: 0.03-0.39 g), B. splendens (TL: 21.09-40.14 mm; BW: 0.05-0.70 g), B. rubra (TL: 11.35 to 47.80 mm; BW: 0.02-0.90 g), and B. dennisyongi (TL: 20.09-47.81 mm; BW: 0.07-0.91 g). There are four Betta species occurred in Aceh waters, namely B. dennisyongi, B. rubra, B. splendens, and B. imbellis. The results showed that B. dennisyongi was found at 8 sampling locations and had higher local distribution (13.56% LD) followed by B. rubra (8.47% LD), B. splendens (6.78% LD) and B. imbellis which had the lowest distribution and was only found in two locations (3.39% LD). Furthermore, field measurements (in situ) of water quality in the wild habitat showed temperature ranging from 23.7 to 31.9°C while pH ranged from 5.24 to 8.51. Based on the IUCN Redlist data, B. rubra is categorized as being critically endangered.

The big-fin reef squid, Sepioteuthis cf. lessoniana (Lesson 1930), is an important commodity species within artisanal and near-shore fisheries in the Indian and Indo-Pacific regions. While there has been some genetic and physical evidence that supports the existence of a species complex within S. cf. lessoniana , these studies have been extremely limited in scope geographically. To clarify the extent of cryptic diversity within S. cf. lessoniana , this study examines phylogenetic relationships using mitochondrial genes (cytochrome oxidase c , 16s ribosomal RNA) and nuclear genes (rhodopsin, octopine dehydrogenase) from nearly 400 individuals sampled from throughout the Indian, Indo-Pacific, and Pacific Ocean portions of the range of this species. Phylogenetic analyses using maximum likelihood methods and Bayesian inference identified three distinct lineages with no clear geographic delineations or morphological discriminations. Phylogeographic structure analysis showed high levels of genetic connectivity in the most widespread lineage, lineage C and low levels of connectivity in lineage B. This study provides significant phylogenetic evidence for cryptic lineages within this complex and confirms that cryptic lineages of S. cf. lessoniana occur in sympatry at both small and large spatial scales. Furthermore, it suggests that two closely related co-occurring cryptic lineages have pronounced differences in population structure, implying that underlying differences in ecology and/or life history may facilitate co-occurrence. Further studies are needed to assess the range and extent of cryptic speciation throughout the distribution of this complex. This information is extremely useful as a starting point for future studies exploring the evolution of diversity within Sepioteuthis and can be used to guide fisheries management efforts.

Abstract The exploration of ichthyofauna in the peat swamp waters of East Kalimantan is interesting to discover, not only has it never been reported, the relocation of Indonesia’s capital city to East Kalimantan is predicted to change the diversity of ichthyofauna in peat swamp waters. Therefore, species identification, distribution, conservation status and potency of fish are important to study and provide valuable references in formulating conservation policies for aquatic ecosystems. The observation parameters carried out in this study include the index of Shannon-Wiener diversity, Simpson dominance, and Sorensen similarity. In addition, the identified fish species are grouped based on their conservation status and potency (consumption and ornamental commodities). A total of 33 fish species were identified at four sampling stations belonging to 8 orders and 15 families with a total of 163 samples. Cyprinidae is the dominant family found with 14 species (33%). A total of 73% of fish collected have potential for fish consumption, 15% of species have potential as ornamental and consumption fish, and 12% of species have potential as ornamental fish. The conservation status (IUCN) of fish in the peat swamp waters of East Kalimantan is divided into five categories: Data Deficient (4 species: 13%), Least Concern (25 species: 78%), Near Threatened (1 species: 3%), Endangered (1 species: 3%), and Extinct (1 species: 3%). The species that was declared extinct was Chitala lopis in early 2021, but interestingly the species was rediscovered in this study in its natural habitat.

Background Rasbora tawarensis is an endemic freshwater fish in Lake Laut Tawar, Aceh Province, Indonesia. Unfortunately, its status is regarded as critical endangered with populations decreasing in recent years. To date no information on the spawning activities of the fish are available. Therefore, this study provides a contribution to the knowledge on reproductive biology of R. tawarensis especially on spawning seasons as well as basic information for conservation of the species. Methods Monthly sampling was conducted from April 2008 to March 2009 by using selective gillnets. The gonadosomatic index, size composition and sex ratio were assessed. The gonadal development was evaluated based on macroscopic and microscopic examinations of the gonads. Results The gonadosomatic index (GSI) varied between 6.65 to 18.16 in female and 4.94 to 8.56 for male. GSI of the female R. tawarensis was higher in March, September and December indicating the onset of reproductive seasons, the GSI and oocyte size being directly correlated with gonadal development stages. Although, a greater proportion of mature male than female was detected during the study, the sex ratio showed that the overall number of female was higher than male. The ovaries had multiple oocyte size classes at every stage of gonadal development, thus R. tawarensis can be classified as a group synchronous spawner or a fractional multiple spawner. Conclusion The spawning seasons of R. tawarensis were three times a year and September being the peak of the reproductive season and the female was the predominant sex. This species is classified as a group synchronous spawner.

BACKGROUND AND OBJECTIVES: Soil is an essential abiotic component serving as a habitat for numerous organisms, including cellulolytic bacteria commonly found in mangrove ecosystems. This bacteria could produce active enzymes needed to improve environmental quality by accelerating the organic matter decomposition. The unique mangrove environment may contain new types of cellulolytic bacteria with new characteristics. Despite several mangrove areas being explored as sources of cellulolytic bacteria, there is currently unexplored data on its diversity in Aceh Province, Indonesia. Accordingly, it is necessary to analyze the molecular biological approach, namely the 16 svedberg ribosomal ribonucleic acid gene, to identify the diversity of cellulolytic bacteria and analyze the phylogenetic relationships between them. METHODS: Bacteria isolates were collected from mangrove soil at six research locations with three replications. A purposive sampling method was applied to determine the research location. Isolates from soil samples were streaked and purified in carboxymethyl cellulose as selective media for cellulolytic bacteria. Molecular identification adopted 16 svedberg ribosomal ribonucleic acid gene sequencing, and the sequencing data were matched with GenBank data. Phylogenetic analysis and genetic distance between species were evaluated using molecular evolutionary genetics analysis. FINDINGS: Thirteen isolates were sequenced, and nine species of cellulolytic bacteria dominated by the Bacillus genus were identified. These species exhibited an identity value of 97.77-100 percent when compared to data from GenBank, and B. velezensis was found to have a close relationship with B. amyloliquefaciens at a value of 0.002 percent. Interestingly, the non-rehabilitated mangrove areas had more bacterial species than the rehabilitated ones. Two Bacillus genus had different nucleotide bases, proving they were distinct species. CONCLUSION: Nine cellulolytic bacteria species were identified; the two closely interspecies genetic distance related were B. velezensis and B. amyloliquefaciens, whereas the farthest were Bacillus spl. and Bacillus sp2. Small genetic distances of interspecies indicate a close relationship between species. In comparing the two sampling sites, the non-rehabilitated mangrove contains higher bacterial cellulolytic species than the rehabilitated and Bacillus-dominated site. The findings provide valuable insights into the diversity of cellulolytic bacteria in mangrove ecosystems. The abundance of bacterial species could serve as sources of cellulase enzymes with different characteristics, essential in an environmental aquatic management.

Mangrove is a plant type influenced by tides action along the tropical coastlines. The tidal type will affect the soil properties, growth of soil microorganisms, and mangrove distribution. The purposes of the study were to analyzing the characteristics of mangrove soil in different habitat type including physical and chemical properties. The research was conducted in mangrove rehabilitation as site 1 and non-rehabilitation as site 2. This research was conducted from April 2020 to September 2020. Analysis of soil properties were consisted of substrate texture, pH, salinity, Organic Carbon, N-total, and P-available. These analyses carried out in Soil Laboratory, Faculty of Agriculture, Universitas Syiah Kuala. The determining of sampling location was done by using random stratified sampling method. Data were collected at 6 stations divided into 3 stations each site. The criteria for each station was based on tidal inundation. Each station was sampled randomly at three depths, namely 0-15 cm (top layer), 15-30 (sub layer) cm, and 30-45 cm (bottom). Soil textures in study areas were loamy sand, sandy loam, dusty loam, and clay in site 1, while in site 2 the soil textures were sandy loam, sandy clay loam, loamy sand, and dusty loam. The high sand and low clay percentage produce the average of organic carbon in the medium, low and very low categories, the organic carbon ranged from 0.25% to 2.18% in site 1 and 0.62% to 1.73% in site 2. The N and P content in site 1 and site 2 were ranged from 0.02% to 0.13%; 25.30% to 68.15% and from 0.04% to 0.11%; 2.60% to 37.85%, respectively. The pH average of mangrove soils indicated that the pH category was neutral, slightly alkaline, slightly acidic in site 1. In site 2 the pH categories were slighly alkaline, neutral, slightly acidic, and acidic. The soil salinity values at different sites indicated high and very high salinity.

Fighting fish Betta dennisyongi is a popular ornamental freshwater fish in Indonesia. Male fighting fish are preferred because the colour pattern and shape of the fins are more attractive so they are more expensive. This study aims to determine the optimum temperature of rearing media water on the male sex ratio and survival rate of fighting fish larvae. A completely randomized design method with three replications was used in this study. The tested rearing temperature water was: 26°C, 28°C, 30°C, and 32°C. Fish were kept for 40 days. The results of the ANOVA test showed that larval rearing temperature affected significantly the ratio of male and female fish larvae survival (P<0.05). The highest percentage of the male sex was found at a temperature of 32 °C (93.33%), this value was significantly different from other temperature treatments. Meanwhile, the highest larval survival was obtained at a rearing temperature of 28 °C (80.00%), where this value was significantly different from other treatments. Therefore, with economic considerations, it is concluded that the optimal larval rearing media temperature is 28 °C.

BACKGROUND AND OBJECTIVES: Understanding the correlation between tidal rhythms and marine organism behavior is crucial. This extends beyond fluctuations in chlorophyll a concentrations and includes various biological processes in the marine environment. Awareness is key for a comprehensive perspective on the role of tidal forces, affecting ocean's physical aspects and life form diversity. This study aims to explore the complex relationship between tidal movements and chlorophyll a concentrations in the northern Bay of Bengal, focusing on how tidal rhythms affect chlorophyll a concentrations. METHODS: The analyzed variables include tidal parameters, such as lunar semidiurnal tidal characteristics and Simpson-Hunter parameters, as well as sea level, tidal current, and current magnitude, obtained from the Tidal Model Driver. Additionally, hourly chlorophyll a data for January 2022 were acquired from the geostationary meteorological satellite Himawari-8, and the rate of change of chlorophyll a was determined through chlorophyll a calculations. This study employs wavelet analysis, applying continuous wavelet transform and wavelet transform coherence for chlorophyll a, rate of change of chlorophyll a, sea level, tidal current, and current magnitude, to explore oscillation patterns and temporal correlations within the marine ecosystem of the northern Bay of Bengal. FINDINGS: Lunar semidiurnal tidal amplitudes increase toward the north, peaking at the Sagar and Ramree Islands, and tidal phases rise from south to northeast. Most of the bay, categorized by <0.25 Formzahl values, experiences semidiurnal tides. Surface lunar semidiurnal elliptic currents, stronger in the north and east, flow clockwise and turn counterclockwise toward the south. The Simpson-Hunter parameter indicates heightened tidal mixing, particularly along the northern and eastern coasts. Region 2 showed the highest mean chlorophyll a concentration (12.58 milligram per cubic meter), whereas Region 1 showed the lowest mean chlorophyll a concentration (0.79 milligram per cubic meter). Similar trends were observed for tidal current and current magnitude. The continuous wavelet transform analysis provides data on chlorophyll a and the rate of change of chlorophyll a within 6, 12, and 24 hours, sea level changes within 8-16 hours, and consistent tidal effects on tidal current and current magnitude in the range of 5-7 hours. The wavelet transform coherence analysis highlights the relationships between chlorophyll a and sea level over 12 and 24 hours periods and between chlorophyll a and current magnitude. Furthermore, the wavelet transform coherence analysis examines the rate of change in chlorophyll a in relation to tidal currents over 6, 12, and 24 hours. CONCLUSION: Tides remarkably affect chlorophyll a concentrations. There are strong links between chlorophyll a concentrations and key tidal aspects, such as sea level and current magnitude. Higher tidal variables correlate with increased chlorophyll a concentrations and are related to the Simpson-Hunter parameter, indicating that regions with vigorous mixing show higher chlorophyll a concentrations. This finding highlights the major role of tidal forces and variations in the chlorophyll a concentrations in the Bay of Bengal. The wavelet transform coherence analysis of chlorophyll a, sea level, and current magnitude data in Regions 1, 2, and 3 show notable coherence in all areas.