Exploration of fishing gears and temporal distribution of fish species at Shibsa River, Paikgachha, Bangladesh

Prosun Roy, Suprakash Chakma, Zubyda Mushtari Nadia, Newton Saha, Md. Arifur Rahman Department of Aquaculture, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh Department of Fisheries Technology, Patuakhali Science and Technology University, Patuakhali 8602, Bangladesh Department of Aquatic Animal Health Management, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka 1207 Department of Fisheries Management, Patuakhali Science and Technology University, Patuakhali 8602, Bangladesh Department of Fisheries Biology and Genetics, Patuakhali Science and Technology University, Patuakhali 8602, Bangladesh


Introduction
Bangladesh is blessed with abundant fisheries resources and these have immense potentiality in the sector of national economy. It has about 700 rivers where, each river has its own geographical, hydrological, sedimentary and biological characteristics (Alam et al., 2013). But the number differs widely due to changes in rivers flow and names in different geographical regions. Fisheries sector of Bangladesh is the most dynamic sector which has great contribution to national income, nutritional demand and earning foreign currency. This sector therefore contributes about 3.57% in GDP and 25.30% in agricultural GDP and supplies about 60% animal protein consumption (DoF, 2018). Therefore, more than 11% of the total population of Bangladesh is engaged with this sector in full time and part time basis for their livelihoods (DoF, 2018). In Paikgachha upazila, one of the most prominent fresh water resources is Shibsa River contributing huge aquatic resources for dramatic changes of lifeline of thousands of fisher folk community.
Fisheries of Shibsa River in terms of food supply and source of income has a great support for many riverine fishermen living around the coast of the river. But at the present time, reduction in the abundance and fish species from the river water is a combusting issue which has great detrimental impression on fishermen. A large number of fishing crafts and gears are operated in the Shibsa River for commercial exploitation of the fishery resources. Fishing gears are equipment's or mechanical devices or tools are being used to harvest fishes (Banglapedia, 2014). Intensity of fishing gears in a river is fully depends of the intensity of targeted fish population presumed to be attainable in that river. Fishing gear intensity, sizes and catch composition are good benchmarking of the status of exploitation level of river (Hoque et al., 2019). Over exploitation, indiscriminant killing of fishes, unplanned and destructive gears are being used by fishermen of Sibsa River. The harmful modern gears and technological advancement have negative impact over the situation (Sayeed et al., 2014). For this reason fish biodiversity are being declining day by day. However, there was no conducted on fishing exploitation and fisheries biodiversity based on scientific management and investigation of Sibsa River due to its public awareness. Therefore, it would be worth to conduct scientific investigation on fishing exploitation as well as catch composition and biodiversity of fishes in this river. Considering the present study, the objectives were to identify fishing exploitation, fishing crafts, catch composition, fish diversity and their conservation status of Shibsa River has become pivotal aspect. Finally, this study investigated the fish fauna of the river to present fish species diversity for the improvement, sustainable exploitation and management of the fisheries resources.

Study area and duration
The present investigation was carried out in the Shibsa River located at Paikgachha, Khulna beside fish landing center (Fig. 1). Geographical location of the study area is 22°3518 N latitudes and 89°2012 E longitudes. About 27 km of the Shibsa River crosses Paikgachha upazila and it connects with the Pasur River inside the Sundarbans Reserve Forest. The study was conducted for a period of 12 months from January to December, 2018. Data was collected personally through face to face interviews.

Data collection
A total number of 200 fisher's fishing in the Shibsa River of different locations was selected for questionnaire interview. Data collection section was divided into two terms named as primary and secondary data considering to accomplish the work precisely.

Primary data collection
For collecting primary data, a well-structured questionnaire having two parts (fishing gears and fishing crafts and fish diversity) was designed.

Study of fishing gears and crafts
Fishing gears and fishing crafts operated at Shibsa River by fisher's were studied by direct physical observation. The process of direct observation was attending with the fishermen in their fishing crafts during fishing gears operation to catch fish diversity. A 30 cm long measuring scale was used as a tool to measure mesh size of existing fishing gears. Shape of fishing gears were also observed when the gears left at the ground for drying purpose. Price per square foot of specific and presented gears were studied from the fishermen as well as local fishing gears trader for more specifications of data on pricing. Data were also noted on fish species by direct observation during collecting gears from river water with fish and then measured all species without sorting with a digital balance to know catch composition of specific gear in Kilogram. During collecting info on fishing gears, records were also through on the fishing crafts as a media of operating fishing gears. Direct observation was conducted to record data on fishing crafts like shape (length, weight and height in cm), constructions material, durability and purpose of crafts.

Fish diversity study
Freshly caught unsorted samples of different gears were collected and then sorted species wise with the help of fisher's. Local name of each individual freshly samples were recorded from the fishermen as well as from Aradtar.

Secondary data
After regular field study, the primary data were compared with the available secondary data to make a precise and composite picture of the present study area. Books, journals, Upazila Fisheries Officer (UFO) etc. were used to modify and accurate the information. The collected fishing gears were categorized under different major groups following Ahmed (1961). Fish sample of different gears were identified and classified into two major group's finfish and shellfish group and then taxonomically characteristics followed by Talwar and Jhingran (1991) and Rahman (2000). Scientific name, habitat and life pattern were studied with the help of Froese and Pauly (2019).

Data processing and analysis
All collected data were accumulated to analyze. Tabular technique was applied by using simple statistical tools like averages and percentages. For processing and analyzing the data "Microsoft Excel-2013" was used. After processing and calculating carefully, most acceptable data was transferred to a master sheet from which classified tables were prepared revealing the finding of the study. Then it was presented in textual, tabular and graphical form for easy understanding of present findings.

Fishing gears
From the study, total 15 different types of fishing gear were listed under 8 major groups described as gill net (current jal, chandi jal, sutar jal), seine net (ber jal, indian net jal), lift net (dharma jal, khora jal), cast net (jhaki jal), push net (thela jal, moia jal), traps (pangus chai, anta, chhara barshi), hook and line (chingri barshi) and wounding gear (koach) ( Table 1). There was no previous finding on fishing gear in Shibsa River was available and thus comparison of the present findings with the previous ones was not possible. However, the present findings are supported by Flowra et al. (2011) and Rahman et al. (2015) who also identified 16 different gears under 7 major categorizes. Nonetheless Ali et al. (2014) observed 11 fishing gears under 7 major groups from Lohalia River which were of lower numbers than existing results. Although Rahman et al. (2016) found that total seven major types of fishing gears defined in the Payra River, but Hoque et al. (2019) recorded more than the present study where they found a total of 18 types of fishing gear under nine major categorize. Rahman et al. (2017) also conducted on the exploration of fishing gear and fisheries diversity of Agunmukha River at Galachipa and revealed nineteen different types of fishing gear were listed under nine major groups. However, eight major types of fishing gears were detected in the Ramnabad River (Ali et al., 2015).
Furthermore, a total of six types of fishing nets recorded from Shitalakshya River (Miah et al., 2010), Rubel et al. (2014) identified eight types of nets as behundi jal, jhaki jal, ber jal, moia jal, thela jal, current jal, tana jal and sain jal and two types of traps as chai and borshi in the Lohalia River, Khan et al. (2013) recorded total seven gear namely current jal, cast net, jhayet jal, thela jal, dharma jal, borshi and long line in the Tista River. Siddiq et al. (2013) identified five types of nets (current jal, ber jal, thela jal, jakhi jal and dharma jal), 3 traps (unta chai, bitte chai and icha chai), 2 hooks (chip borshi and chara borshi), 2 spears (teta without hooks and teta with hooks) from Dogger beel. But the study of Sayeed et al. (2014) per behind the present study and revealed that 34 different types of fishing gears including nets (11), traps (11), hook and lines (4), wounding gears (4), Fish Aggregating Devices (FADs) (3) and hand-fishing (1).  The fishermen of the Shibsa River used different types of fishing gear (Fig. 2). On the basis of the use, the ber jal was the most dominant gear used by the fishermen constituting 26.67% followed by current jal (13.33%) among total gear type. The result stated that the seine net was the highest constituents used by the fishermen. The fishermen also used jhaki jal (11.33%), chandi jal (10.67%), indian net jal (8%), dharma jal (7.33%), khora jal (5.33%), chingri barshi (4%), thela jal (3.33%) and moia jal (2.67%). Moreover, sutar jal, chhara barshi and koach were used similarly comprising of 2% and pangus chai and anta comprising of 0.67%. Ali et al. (2015) also found the highest use of seine net and gill net comprising of 60% and 20%, respectively and the lower uses were found in case of lift net (0.6%), cast net (1.2%), push net (1.8%) and trap (0.6%) from Ramnabad River which supports similar results obtained from the present study. Maximum 6.35 cm and minimum 0.5 cm mesh size was found in 5 groups comprising 10 different net in the present study (Table 1). This study was close to the  Rahman et al. (2017) who found the highest mesh size (10 cm) for gill net and the lowest size (0.5 cm) in seine net, cast net, push net and fixed purse net in the Agunmukha River. The highest price was observed in case of ber jal (60,000-1, 50,000 Tk) followed by chandi jal (10,000-15,000 Tk) and the lowest price was for koach (150-200 Tk) (Table 1). In the present study, the price of fishing gears were ranged from 150-1,50,000 Tk (DoF, 2018) and the findings were lower than the findings of Rahman et al. (2017) who found the highest and lowest price of fishing gears 86,285 and 162 Tk, respectively.
The highest catch composition was found for ber jal 50 kg/day. The catch composition of chandi jal, current jal, sutar jal, dharma jal, indian net jal, jhaki jal, khora jal was 30, 25, 20, 16, 15, 14, and 10 kg/day, respectively which was lower than that of seine net and higher than any other gear used in the Shibsa River. The lower catch composition was observed for thela jal (8 kg/day), moia jal (7 kg/day) and chhara barshi (6 kg/day), anta (4 kg/day), koach (3 kg/day), pangus chai (2 kg/day), chingri barshi (1 kg/day) (Fig. 3). On the other hand, maximum using of ber jal, current jal, chandi jal and jhaki jal were correlated with the maximum catch composition of the net. Most of the fishermen catches fish by ber jal and current jal as well as with the highest catch composition. The values of the catch composition were higher than the findings of Rahman et al. (2017) who found ranging from 0.5 to 20 kg/day by different gears.  Fishing gears fish species at Shibsa River, Paikgachha, Bangladesh Catadromous LC Anadromous -the fish which migrates from salt water to spawn in freshwater or up rivers; Catadromous -the fish which migrates from freshwater towards the sea to spawn; Amphidromous -the fish which are born in freshwater/estuaries and then migrates into the ocean as larvae but migrating back into freshwater to grow into adults and spawn; Potamodromous -the fish which migrates only within the freshwater; Oceanodromous -the fish which migrates only within the sea water; **MW=Marine Water, FW=Fresh Water, BW=Brackish Water, EN=Endangered, VU=Vulnerable, LC= Least Concern, DD= Data Deficient, NT=Near Threatened, NE=Not Evaluated.

Fisheries diversity
The following study depicts presence of total 60 species (55 from finfish and 5 from shellfish) in 28 families under 9 orders (Table 3 and 4). Perciformes (30%) found to be the dominant order followed by Cypriniformes (21.67%), Siluriformes (20%), Clupeiformes (8.33%), Decapoda (8.33%), Synbranchiformes (5%), Osteoglossiformes (3.33%), Cyprinodontiformes (1.67%) and Mugiliformes (1.67%). Fishes of Cyprinodontiformes and Mugiliformes orders were found rarely in study area (Fig.  4). Total 60 species in 28 families (Table 3 and 4) were recorded during the present study and almost similar outcomes were detected by Chakraboty and Mirza (2007) at about 70 species of fishes from the Gharia beel but by Rahman (2000), who found total 47 species of fish from Bskbbeel (floodplain) and Galib et al. (2014) reported 53 fish species belonging to 10 orders, 28 families and 47 genera were collected and identified in Andharmanik River in Patuakhali where the dominant order of fishes was Perciformes (18 species) followed by Siluriformes (12 species) and Clupeiformes (9 species). Ehshan et al. (2007) reported a total of 40 species of fish including three exotic species in Chanda beel which was lower than the present findings. The findings of Hossain et al. (2012) showed that Meghna river estuary is habitat with 53 fish species and Oxyurichthys microlepis, Hemiarius sona Arius thalassinus, Batrachocephalus mino and Arius caelatus are the major contributory species (>6%) for both spatio-temporal scales.
In the Shibsa River, about 8 endangered (14%), 5 vulnerable (8%), 33 least concern (55%), 8 near threatened (13%) and 6 not evaluated (10%) species were observed during the study (Fig. 5, Table 3 and 4). Eight species which were marked as endangered species by the IUCN red list status of Bangladesh (2015) were found in good quantities in the Shibsa River. These species are also decreasing in number day by day from the river due to over exploitation. Galib et al. (2014) observed two critically endangered 3 endangered and 5 vulnerable fish species of Bangladesh were also recorded along with one alien carp species. But Rahman et al. (2015) identified 7 vulnerable, 7 endangered and 2 critically endangered species from Rabnabad channel which was lower than that of the current study. Galib et al. (2013) also recorded 10 vulnerable, 10 endangered and 6 critically endangered species from river the Choto Jamuna which was higher than that of the current study.

Conclusion
The Shibsa River is very important for fisheries resources in the South -Western part of Bangladesh. The river plays a vital role for maintaining the fisheries diversity. Under the group of gill net, seine net, push net, cast net, ber jal, current jal, chandi jal, sutar jal, jhaki jal were the most available and prominent fishing gear used by the fishermen. Among the different fishing gear, ber jal, current jal, chandi jal, could be considered as commercial fishing gear due to their maximum catch composition and being higher in size and price. Incisively, 60 fish species including 55 finfish and 5 shellfish were recorded covering 28 families. However, different smaller mesh size and non-selected fishing gears especially current jal and jagat ber jal were responsible for destroying fishing habitats in this river. As a consequence, biodiversity is decreasing gradually in the Shibsa River. Proper initiatives should be taken into consideration by Government, stakeholder, NGOs and local policy makers for effective fisheries diversity management of the Shibsa River.