Annotated checklist of ponyfishes (Perciformes: Leiognathidae) from Bangladesh, the northern Bay of Bengal.

Information on the taxonomy of ponyfishes (Leiognathidae Gill 1893) from Bangladesh was hitherto inadequate and details of some species were lacking. Based on specimens, the present study reports 12 species of ponyfishes from the coasts of Bangladesh with short descriptions of their diagnostic characters. Six of these species, Aurigequula longispina (Valenciennes 1835), Deveximentum megalolepis (Mochizuki & Hayashi 1989), Equulites leuciscus (Günther 1860), Eubleekeria rapsoni (Munro 1964), Gazza rhombea Kimura, Yamashita & Iwatsuki 2000 and Karalla daura (Cuvier 1829), constitute the first records in Bangladesh. The present specimens of D. megalolepis represent the westernmost distribution of this species in the Indo-Pacific region.

River pattern influences the composition of small indigenous species (SIS) of fish in deltaic Rajbari district, Bangladesh.

Bangladesh is endowed with diverse rivers providing huge ecosystem services, but the diversity status and the abundance of the small indigenous species (SIS) are not identical in all rivers due to the natural water flow regime and anthropogenic challenges. Therefore, the present study endeavors to elucidate the composition and conservation status of SIS fish from four rivers namely, the Padma, the Gorai, the Chandana and the Horai rivers of Rajbari District, Bangladesh. Data were meticulously collected through fish sampling in each season, field observations, focus group discussions, and individual interviews by using a semi-structured questionnaire spanning from May 2021 and April 2022. The number of SIS in the Padma, the Gorai, the Chandana and the Horai rivers of Rajbari were 60, 36, 33 and 26, respectively, whereas a predominant concentration of fishes was notably observed in the benthopelagic zone of these rivers. Among the 60 riverine SIS, 23 fish were common in the four rivers. Additionally, Cyprinidae (>30%) was observed to be the most abundant SIS in the studied rivers. The fishermen in the research area used seven major fishing equipment of which cast nets are the most common for catching fish species. The abundance of SIS during the rainy season was the highest for all the studied rivers than the other seasons and 12 SIS were available throughout the year. Notably, the least concerned SIS outnumbered the other categories whereas, more than 10% was under the vulnerable category in the four rivers. The leading threats to the fish diversity were pollution followed by illegal and overfishing, siltation, reduced depth, degeneration of rivers and others. Consequently, to safeguard the existing SIS, reducing human pressure, implementing fishing regulations strictly, establishing and administering fish sanctuaries, and raising public awareness can be helpful for the sustainability of aquatic resources in deltaic areas.

DNA barcoding of reef-associated fishes of Saint Martin's Island, Northern Bay of Bengal, Bangladesh.

This study employs the DNA barcoding approach to make a molecular taxonomic catalog of reef fishes of Saint Martin's Island (SMI), an ecologically critical area (ECA), and Marine Protected Area (MPA) in Bangladesh. DNA barcoding, along with morphological analysis, confirmed 84 reef-associated fish species in SMI belonging to 16 orders, 39 families, and 67 genera. A total of 184 sequences were obtained in this study where 151 sequences (534-604 bp) of 81 species were identified from the COI barcode gene and 33 sequences (609 bp) of 19 species from the 16S rRNA gene region which were submitted to the GenBank and Barcode of Life Data System (BOLD). Among these sequences, 70 sequences of the COI gene and 16 sequences of 16S rRNA gene region from 41 species were submitted for the first time into the GenBank from Bangladesh. For molecular characterization analysis, another 37 sequences of 15 reef fish species of SMI were added from previous studies, making a total of 221 DNA sequences which comprised 179 sequences of 96 species for the COI gene and 42 sequences of 26 species for the 16S rRNA gene region. The COI sequences contain 145 haplotypes with 337 polymorphic sites, and the mean genetic distances within species, genera, and families were calculated as 0.34%, 12.26%, and 19.03%, respectively. On the contrary, 16S rRNA sequences comprised 31 haplotypes with 241 polymorphic sites, and the mean genetic divergences within species, genera, and families were 0.94%, 4.72%, and 12.43%, respectively. This study is a significant contribution to the marine biodiversity of Bangladesh which would facilitate the assessment of species diversity for strategizing management action. It is also an important input to the DNA barcode library of reef fishes of the northern Bay of Bengal.

Species identification, reproductive biology, and nutritional value of marine shellfish (Meretrix lyrata) in the Bay of Bengal.

Meretrix lyrata which is under the family of Veneridae and under the order of Venerida, is a nutritionally and economically important edible mussel in Bangladesh. However, studies on species identification and nutritional value in M. lyrata are scarce. Therefore, a detailed investigation was conducted on (i) species identification of the common edible mussel through DNA-barcoding and morphometrics, (ii) reproductive features, such as size at sexual maturity, spawning, and peak-spawning seasons under different environmental factors, and (iii) nutritional status through proximate analysis of M. lyrata mussel collected from the Bay of Bengal, Bangladesh. The results indicated that the size at sexual maturity for M. lyrata was 4.2 cm and the spawning seasons were significantly affected by the dissolve oxygen and salinity. The study also demonstrated that the spawning of M. lyrata occurred from January to June and December while peak spawning season was May in the Bay of Bengal. The higher protein and moisture contents with lower fat in M. lyrata indicated that are value-added seafood with higher nutritional values for consumers.

Description of a new species of giant guitarfish, Glaucostegus younholeei sp. nov. (Rhinopristiformes: Glaucostegidae) from the northern Bay of Bengal, Bangladesh.

A new species of giant guitarfish, Glaucostegus younholeei sp. nov., is described from 13 specimens, 730933 mm total length, collected from fish landing center of Bangladesh Fisheries Development Corporation in Cox's Bazar district of Bangladesh. The new species is distinguished from congeners in having the following combination of characters: Body brownish or greyish in color with a narrowly wedge-shaped disc, and long narrow bluntly pointed snout (angle 3140°), and broad oblique nostrils with the narrow anterior opening. Nostrils about half of the mouth width, subequal (0.981.33) to internasal width; ~5557 nasal lamellae; anterior nasal flaps slightly penetrating into internasal space, their interspace 2.20 2.61 in length of the posterior nasal aperture. Orbit very small in adults, diameter 8.1911.62 in preorbital length, 2.252.69 in interorbital space. Rostral ridges almost joined along their entire length; margin of cranium sharply demarcated before eyes. Spiracular folds very short and widely separated. Skin rough, densely covered with small denticles, more coarsely granular on the dorsal surface than ventrally, enlarged between orbits and in a distinct band between nape and first dorsal fin. Tail relatively longer, length 1.151.48 in disc length; dorsal fins narrowly spaced, interspace 1.322.11 in base length of the first dorsal fin. Clasper length in adult male 4.375.70 in total length. Phylogenetic analysis of DNA barcode sequences also shows the clear divergence of Glaucostegus younholeei from other congeneric species obtained from GenBank. A key is provided to the 8 known members including new species of the genus Glaucostegus.

DNA barcoding of brackish and marine water fishes and shellfishes of Sundarbans, the world's largest mangrove ecosystem.

The present study aims to apply a DNA barcoding tool through amplifying two mitochondrial candidate genes i.e., COI and 16S rRNA for accurate identification of fish, aquatic molluscs and crustaceans of Sundarbans mangrove wetland, to build a reference library of fish and shellfishes of this unique ecosystems. A total of 185 mitochondrial COI barcode sequences and 59 partial sequences of the 16S rRNA gene were obtained from 120 genera, 65 families and 21 orders of fish, crustaceans and molluscs. The collected samples were first identified by examining morphometric characteristics and then assessed by DNA barcoding. The COI and 16S rRNA sequences of fishes and crustaceans were clearly discriminated among genera in their phylogenies. The average Kimura two-parameter (K2P) distances of COI barcode sequences within species, genera, and families of fishes are 1.57±0.06%, 15.16±0.23%, and 17.79±0.02%, respectively, and for 16S rRNA sequences, these values are 1.74±.8%, 0.97±.8%, and 4.29±1.3%, respectively. The minimum and maximum K2P distance based divergences in COI sequences of fishes are 0.19% and 36.27%, respectively. In crustaceans, the K2P distances within genera, families, and orders are 1.4±0.03%, 17.73±0.15%, and 22.81±0.02%, respectively and the minimum and maximum divergences are 0.2% and 33.93%, respectively. Additionally, the present study resolves the misidentification of the mud crab species of the Sundarbans as Scylla olivacea which was previously stated as Scylla serrata. In case of molluscs, values of interspecific divergence ranges from 17.43% to 66.3% in the barcoded species. The present study describes the development of a molecular and morphometric cross-referenced inventory of fish and shellfish of the Sundarbans. This inventory will be useful in future biodiversity studies and in forming future conservation plan.

First record on size at sexual maturity and optimum catchable length of 10 marine fishes from the Bay of Bengal (Bangladesh) through multi-models approach: a key for sound fisheries management.

Appropriate management systems for the protection of fishes are mostly relying on the information of size at sexual maturity and optimum catchable length. The purpose of this research was to estimate the size at sexual maturity (Lm) and optimum catchable length (Lopt) of 10 marine fish species from the Bay of Bengal (Bangladesh) through multi-models using commercial catches from October 2019 to September 2020. Also, we calculated the Lm and Lopt of these species from worldwide water bodies based on maximum length (Lmax). A total of 2967 specimens of 10 fish species were evaluated in the current study and total length (TL) was noted up to 0.1 cm using a measuring board, while body weight (BW) and gonad weight (GW) are weighed by digital electronic balance with 0.01 g accuracy. To assess the Lm, three different models such as (i) empirical model based on Lmax, (ii) the relationship between TL (total length in cm) vs. GSI (gonadosomatic index in %), and (iii) logistic model were considered and Lopt was assessed based on L∞. The estimated lowest Lm was 11.8 cm (Lmax-based), 12.8 cm (TL vs. GSI), and 13.7 cm (logistic model) for Thryssa setirostris and highest Lm was 23.3, 20.5, and 22.0 cm for Priacanthus macracanthus through Lmax, TL vs. GSI, and logistic-based models, respectively. From these three models, the lowest mean value of Lm was obtained for T. setirostris (12.7 cm) and highest was recorded for P. macracanthus (21.9 cm). Fifty percent of mature marine species was in 14.9 cm TL and 90% species was in 19.5 cm TL. The smallest Lopt was obtained as 13.4 cm TL for T. setirostris and largest was 28.2 cm TL for P. macracanthus. This study was generated data on Lm and Lopt for 10 newly marine species, which are globally absent. Therefore, this study will be helpful for developing sustainable management strategies and conservation of marine fishes through the implementation of mesh size based on the size at sexual maturity (Lm) and optimum catchable length (Lopt).

Pomacentrus bangladeshius, a new species of damselfish (Perciformes, Pomacentridae) from Saint Martin's Island, Bangladesh.

A new species of damselfish, Pomacentrus bangladeshius, is described from 3 specimens, 67-77 mm standard length (SL), collected from Saint Martin's Island, Bangladesh. The new species is distinguished from congeners in having the following combination of characters: XIV, 13 dorsal-fin elements; II, 14 anal-fin elements; 19 pectoral-fin rays; 18-19 lateral-line scales; 17-19 gill rakers on first arch; body depth 1.68-1.88 (1.88) in SL; snout 4.17-4.60 (4.17) in head length; head 2.91-3.09 (3.08) in SL; a prominent notch present between preorbital and suborbital; olive to dark brown body color, dark brown premaxilla, and yellow iris with a narrow bronze eye ring. The new species inhabits shallow reef flats around rock and coral outcrops. Phylogenetic analysis also shows the clear divergence of P. bangladeshius from other genetically closely related congeneric species retrieved from GenBank and that it represents a separate lineage.