RESUMO
Kaptai Lake, the largest artificial reservoir in Southeast Asia, is home to a diverse fish fauna that supports thousands of livelihoods and is distinguished by multi-species and multi-gear fisheries. In Kaptai Lake, the gear-based catch composition, catch rate and distribution pattern are little known. From August 2020 to April 2021, a nine-month study was conducted in five upazilas using direct catch assessment surveys and fishing effort surveys from four fishing gears, namely seine nets, gill nets, lift nets, and push nets. A total of 49 morpho-species from 22 families were found, with three species from the Clupeidae accounting for 93.63 % of the catch in all gear combined. The total catch composition and CPUE were higher in seine nets (75.07 %, 13.86 ± 1.8 kg/gear/trip respectively) and lower in lift nets (4.97 %, 1.01 ± 0.21 kg/gear/trip) and showed significant differences among gears, except sampling sites whereas CPUE was higher in Naniarchar for seine nets (17.29 ± 8.89 kg/gear/trip) and lower in Langadu for lift nets (0.62 ± 0.25 kg/gear/trip). Seine nets captured more species, and the number of species increased significantly as CPUE increased. Our study assessed four gears that targeted different fish species with little overlap in leading species; seine nets and gill nets primarily targeted Clupeidae (96.53 % and 41.69 %, respectively), whereas lift nets and push nets primarily targeted Cyprinidae and Palaemonidae (38.93 % and 99.37 % respectively). The observed abundance and variety of fish species captured in gill nets suggest a significant overlap in the selectivity of this fishing method with that of lift nets. Due to the varying contributions of sites and gears, the nMDS ordination pattern reveals a weak spatial variation in catch composition. According to the SIMPER results, Bagridae, Gobiidae, and Ambassidae were the most significant contributors to site grouping patterns across all gears. Furthermore, the findings indicate that the catch composition does not follow the typical pattern of spatial variation. By implementing measures to eliminate or decrease the usage of small mesh nets, there is expected to be a corresponding decrease in the capture of small fish. Additionally, this action will help mitigate the issue of overlapping selectivity among the current fishing gears. Our findings provide baseline data on the potential efficacy of gear limitation and suggest a gear-based management strategy.
RESUMO
Mahseer are large-scale fish of the Cyprinidae family that inhabit South and Southeast Asian mountainous streams, rivers, and reservoirs. Tor tor and Tor putitora, two species of the Tor genus, were reportedly found in Bangladesh. This study aimed to confirm the species level of specimens collected from the Sangu River. The collected samples were identified using the DNA barcoding technique, followed by amplifying 645 bp of the cytochrome oxidase c subunit 1 gene (COI) using the FishF1/FishR1 universal primer. The sequence similarity was conducted using BOLD and NCBI databases which showed 99.85-100 % similarity to the reference genome. The genetic divergence between T. putitora vs. SRI, BT, and ST was found to be 0.0239, 0.0239, and 0.0238, respectively. The genetic divergence between T. tor vs. SRI, BT, and ST was 0.0272, 0.0272, and 0.0270, respectively. In the phylogenetic tree, two clusters were formed where collected specimens (SRI, BT, and ST) formed a subcluster with the reference genome (NC_056296.1 T. barakae) with 100 % bootstrap support. This study's findings revealed the presence of a new Tor species named Tor barakae in the Sangu River basin in Bangladesh.
