Biometric indices provide crucial information on fish population growth and aquatic habitat well-being. This study offers the first comprehensive elucidation on biometric indices of Gagata cenia (Hamilton, 1822) specifically; population structure, growth pattern and parameters, form factor (a _3.0 ), conditions factors, prey-predator status, reproduction, optimum catchable length (L _opt ), mortality and exploitation rate in the Jamuna River, northern Bangladesh. The aim of this study is to estimate stock status of G. cenia in order to protect the declining wild stock. Total of 725 fishes were randomly collected (ranges between 2.7 and 8.5 cm total length (TL), while 0.30-8.24 g body weight (BW)) occasionally using conventional fishing gears during June 2020 to May 2021. The b value of length-weight relationship (TL vs. BW) was 3.33 which indicated positive allometric growth pattern with r ² value 0.942. Growth parameters were supposed as asymptotic length (L _∞ ) = 9.09 cm, (K) = 0.94 year^-1, growth performance index (Ø') = 1.89 and longevity (t _max ) = 3.2 year^-1 for this population. The calculated a _3.0 was 0.0172 and Fulton's condition (K _F ) is the best suited tool for assessing the well-being of this population. Additionally, relative weight (W _R ) specifies an imbalanced territory with regard to the occurrence of predators. The size at sexual maturity (L _m ) and L _opt for combined sexes of G. cenia were 5.4 cm and 6.0 cm, respectively henceforth fish sizes 6.0-6.5 cm TL are recommended for exploitation. The current study verified fishing mortality was significantly lower than natural mortality and the exploitation rate (E) was 0.32 which indicated the stock was under fishing. Our findings would be very beneficial in planning the sustainable and appropriate management of this fish in Bangladesh and nearby ecosystems.

Knowledge about fisheries market margins and fish availability in the market is crucial to establish an effective and well-planned marketing strategy. Hereby, the study was conducted to bring some knowledge on the availability of raw and processed fish and its marketing channel in Rajbari Sadar, Bangladesh from June to December 2020. Here, data were collected from fish traders and consumers of the target markets through questionnaire surveys, focus group discussions and field visits. The study found 107 fish and shellfish species in these markets, of which more than 50% species were commonly available and less than 10% were found very rarely. The study also observed 18 types of processed fish products in these markets including dried (77.77%), salted (16.67%) and fermented (5.56%) products arriving from mostly Dhaka and Chattogram. The markets were dominated by wild freshwater fishes of nearby rivers, ponds and canals etc. The length of processed and marine fish marketing channel was comparatively longer than freshwater one because these items are supplied here from coastal districts via several intermediaries. The study revealed remarkable market margin for hilsa fish even noticed up to 57.14% at consumer level. There was also observed some major constraints to a good marketing system such as unplanned market location, insufficient drainage system, high transportation cost, etc. Based on the constraints, the study would suggest to establish a well-planned and modern equipped fish market with high quality cold storage and ice factories, which could help to ensure smoother transaction route from production to customer minimizing economic loss.

Identifying stock is key to sustainable fisheries management and conservation. Using traditional morphometrics (TMR) and image-based truss network analysis (ITNA), we evaluated the stock structure of the endangered queen loach, Botia dario. The study was carried out in the following five stocks in Bangladesh’s northern rivers: the Atrai, Dhorala, Danu, Jamuna, and Padma. The inventory regarding stock structure was investigated using a total of nine traditional morphometrics, 11 ratios, and 23 truss measurements for each individual. To generate 23 ITNA, 12 landmarks were used. To assess variations among the stocks, a principal component analysis (PCA), factor analysis (FA), canonical variate analysis (CVA), and cluster analysis (CA) were performed. Six principal components explained 91.50% of the variation in TMR, while seven principal components explained 73.425% of the variation in ITNA. CVA, using traditional methods and ratios were correctly classified as 65.0%, 42.0%, 64.2%, 89.3%, and 77.5% for Danu, Padma, Jamuna, Dhorala, and Atrai River stocks, respectively, based on original grouped classes. CVA using ITNA was correctly classified as 90.0%, 80.0%, 77.4%, 94.6%, and 98.6% for Danu, Padma, Jamuna, Dhorala, and Atrai River stocks, respectively, based on original grouped classes. CVA analysis based on TMR and ITNA showed that cannonical variates (CV1 to CV3) are related to the whole-body shape. Both TMR and ITNA formed two clusters. In the first cluster, the Jamuna and Atrai River stocks combinedly formed a separate stock based on (TMR). In ITNA, the Dhorala and Atrai River formed as separate stocks from the other four stocks. According to this study, combining TMR and ITNA analysis aids in the differentiation of various B. dario stocks. The stock separation of this species was supposed to be geographic disconnection, waterway nature, and temperature variations. The B. dario stocks are heavily exploited and the species is an ideal nominee for species variation to boost the aquaculture yield. Within-stock distinctions were revealed in this study, necessitating the identification of gene pools and molecular studies to achieve a deeper understanding of the stocks. Through a more scientific approach, this stock structure study may aid in the development of conservation programs for this endangered species.

Aquaponics is one of the most effective, water-efficient, self-fertilizing, and eco-friendly technologies for organic food production. In this system, plant nutrients instigate from the fish feed and fish waste. The objective of the current study was to assess and compare the plant growth and fish production in different fish stocking densities in aquaponics. Four different densities were tested for the study, such as 2.94 (T1), 3.92 (T2), 4.90 (T3), and 5.88 (T4) kg m-3 tilapia with an initial length of 16.8±0.17 cm and a weight of 72.6±5.14 g, respectively. The tilapia were fed with commercial floating feed twice daily at 3% body weight. Sampling of fish and plant growth parameters were carried out fortnightly, whereas, water quality parameters such as temperature, dissolved oxygen, and pH were measured weekly, and electrical conductivity (EC), total dissolved solids (TDS), ammonia, nitrite, and nitrate were measured fortnightly. The data interpretation showed that pH, ammonia, nitrite, EC, and TDS were significantly increased with the increasing fish densities. On the other hand, except Zn, Fe and Mn, all other nutrients of the fish tanks were significantly increased with the fish densities in the treatments. The first flower and pod appearance were observed in T3 at 39.33±4.03 and 44.06±4.09 days, respectively those were significantly the lowest with the fish density of 4.90 kg m-3. The highest and the lowest cowpea production were 4.61±0.88 and 2.50±0.71 kg m-2 in T3 and T4, respectively. However, the highest fish production was 14.76±0.71 kg m-3 in T4, although T3 performed better in the case of other components, where most of the fish growth parameters were statistically similar among the treatments. Moreover, almost all the proximate compositions of cowpea and fish were statistically similar except that the moisture content in the tilapia and ash content in cowpea were significantly different. The study showed that the stocking density of the tilapia of 4.90 kg m-3 resulted in higher production of cowpea by maintaining good water quality for the plant compared to the other stocking densities.

The present study was undertaken to ascertain fishing gear and craft uses, fish catch composition of the particular gear along with the identification of available fish species of Shibsa River, South-Western Bangladesh for a period of 12months from January to December, 2018.From the present study, 15 distinct fishing gears under 8 major groups including berj al, chandi jal and current jal were dominantly encountered. Precisely 60 fish species (55 finfish and 5 shellfish) were listed covering 28 families of which Cyprinidae was found as most dominant having 13 species followed by Bagridae, Channidae, Clupeidae, Siluridae, Gobiidae, Palaemonidae, Ambassidae, Cichlidae and the rest of the families having only one single species under a single genera for each. This study also depicted 8 endangered (14%), 5 vulnerable (8%), 33 least concern (55%), 8 near threatened (13%) and 6 not evaluated (10%) species out of 55 finfish and 5 shellfish species. Due to incognizance and over exploitation on fish with small mesh size net, species diversity of this river is under threat. So, public awareness and compatible knowledge on use of suitable fishing gears with suitable mesh size could contribute to sustainable fisheries in this river and betterment in livelihood of the fishermen in the surrounding area.

The dwarf gourami, Trichogaster lalius, is a low-cost freshwater edible fish for the people of South Asian countries containing a variety of essential nutrients. The first wide-ranging explanation on the population parameters specifically; length-frequency distribution (LFD), length-weight relationships (LWRs), length-length relationship (LLR), form factor (a3.0), condition factors (allometric, KA; Fulton’s, KF; relative, KR; relative weight, WR), size at first sexual maturity (Lm) and natural mortality (Mw) of T. lalius were estimated. 768 specimens were collected over one calendar year (March 2019 to February 2020) from a wetland ecosystem named Beel Dakatia, Khulna, southwestern Bangladesh through various traditional fishing gears. Lengths (in cm) and weight (in g) were assessed through a wooden fitted measuring scale and digital balance with accuracy 0.1 cm and 0.01g, respectively. In the current study, the total length ranged from 2.6-9.9 cm while the bodyweight ranged from 0.63-23.80 g for T. lalius. The TL size for classes of 7.00 to 7.99 and 8.00 to 8.99 cm indicated numerically prominent groups. Moreover, the calculated allometric coefficient (b) of LWRs represented a negative allometric growth pattern (b<3.00) for T. lalius in the Beel Dakatia. Noticeably, the a3.0 was 0.015 signifying that the fish is fusiform in shape. KF is the best-suited tool to assess the well-being of T. lalius among the four types of condition factors. According to Wilcoxson signed-rank test, the WR revealed significantly dissimilarities from 100 (P<0.0001), signifying the unbalanced territory for T. lalius. Moreover, the estimated Lm was 5.91 (~6.0) cm TL and Mw was 1.28 year-1 in the Beel Dakatia, southwestern Bangladesh. Finally, the knowledge about the biological aspects of T. lalius may be used for improved management tools in the future.