Abstract: Background and Objectives: Tulshiganga river is rich in aquatic biodiversity in Joypurhat, Bangladesh. Present survey narrated the venerability and diversity indexes of ichthyofaunal distribution here. Materials and Methods: On-pot data collection and questioner survey was conducted thoroughly among fishermen and tabulated data were analyzed by different population diversity index. Results: About 36 species from 13 different family were reported in this study. The most dominant fishes are included this family Cyprinidae. Based on view of the local fisherman, the three fish species from Siluriformes i.e., Colisa laila, Clarias batrachus and Hara hara under threat. Fourteen species was reports as less common in that area such as Rohtee cotio, Labeobata, Acanthocobitis botia, Anabas testudineus etc. With 1 vulnerable species, 22 were less concern, 2 near threaten, 1 data deficient and 9 fish species not evaluated in International Union for Conservation of Nature (IUCN) red list. Order Siluriformes (19.44%) was higher in amount after order Cypriniformes (44.44%), followed by Perciformes (16.67%). Fish group of Carps shows a higher index of H (Shannon-Weiner) and Glassfish were less. Conclusion: The species composition of family Gobiidae, Clariidae, Sisoridae, Siluridae, Heteropneustidae and Belonidae were similar. Channiformes and mastacem beliformes are newly reported species.
INTRODUCTION
Bangladesh prides itself on being very rich in fish diversity, a list of 253 freshwater fish species was identified and recorded by International Union for Conservation of Nature1. The fish contain most important elements like protein, lipid etc., which are essential for the nutritional health and remedy for various diseases2. The fish alone provide about 60% of animal protein3. In addition, the fish create the employment opportunity and foreign exchange earnings4 as well as economic development to the people5-8. It is truly said that it reflects the lifestyle, customs and the history of the people of Bangladesh8.
Rivers are the main sources of freshwater fishes in Bangladesh. Bangladesh is a sub-tropical agro-based riverine country having 700 rivers according to Department of Fisheries, Bangladesh9. It consists of 7,82,559 ha of inland closed waters and 39,16,828 ha of inland open waters along with huge areas of the Bay of Bengal10 which continuously contributing in the fisheries sector of Bangladesh11. But now a days, a multitude of factors including rapid population growth, water pollution by industry, natural disasters, sea intrusion, salinity and the over-exploitation of fisheries, that diversity has started to diminish. So determining the biodiversity status of all rivers is to days burning concern.
Out of those 700 rivers9 Tulsiganga is the main river12 which sited at Khetlalupazila, Joypurhat which is selected for current study. Some studies on ichthyo-diversity were done by the researchers. Rahman et al.3 reported that 8 fish species positioned under vulnerable stage from Hakaluki haor, Bangladesh. The scientists, Mohsin et al.13 stated that 2 species are critically endangered, 3 endangered and 5 vulnerable fish species from Andharmanik river.
However, in this study area, less information about ichthyofaunal biodiversity has been found. So the objective of present study was to show the different levels of threat and current status of ichthyofaunal biodiversity along the study area. Therefore, the findings of this study would add the information in the database for long term research and it would contribute to form management action plan for the threatened freshwater fish species.
MATERIALS AND METHODS
Study area: This study was conducted for a period of 8 months from May, 2014 to December, 2014 in Tulsiganga river14 under Khetlalupazila at Joypurhat district (Fig. 1).
| Fig. 1: | Study area14 |
The bazar (Market) areas were selected for mass evaluation and questioner reviews. The fish species were collected form river and also cross checked with the selling fish list in local market area by visiting. The single strait of Tulsiganga river bordered by only Khetlalupazila were covered by researchers which is marked as red box in Fig. 1.
Data collection: The present study was completed in this river for 8 months; the setting aim of the study was to find out the diversity of available fish species in that river. To address this desired aim, the fish samples were collected from fishing spots of study area and identified on the spot based on their morphometric and meristic characters following the procedures of Bhuiyan15 and Talwar and Jhingran16. Specimen which was difficult to identify in field was brought to the laboratory for proper identification followed by Rahman17,18.
Data analysis: Data were analyzed with simple statistical equation by using MS Excel, 2016. Different diversity index were used to have a clear view of fish community and their dominance. Diversity Indexes were calculated using following equation from Rahman et al.19
| • | Shannon-wiener Index (H) for better understanding of fish biodiversity: |
| • | Simpson’s dominance index: |
| • | Margalef’s diversity index: |
where, ni is number of individuals and N is total number of individuals for the area, S is total number of species and ln is the natural log of the number.
Monthly data were noted on time in standby tables. After finishing study period, collected data were tabulate carefully with standard unit and subjected to simple descriptive analysis using latest computer software Microsoft Excel, 2016.
RESULTS AND DISCUSSION
Fish diversity of Tulsiganga river: The river system of Bangladesh and their tributary travels through varied geo-climatic zone, displaying high diversity in their biotic and abiotic characteristics. Fisheries resources in the study areas of Tulsiganga river are mostly capture fisheries. In the present study, economically important fishes are recorded with their relative abundance. A total of 36 open water fish species belonging to 28 genera, 13 families and 6 orders were identified (Table 1) during the study period. Highest abundant (44.44%) order was Cypriniformes in this study, which is also higher in Hakaluki (Table 2), reported by Rahman et al.3. However, Perciformes was reported higher (Table 2) by Ali et al.20 and Rahman et al.19. Cyprinidae was most dominant family among others reported families (Fig. 2). Order Channiformes and Mastacembeliformes are newly reported abundant species in study area (Table 2).
Bhuiyan et al.21 published a checklist of the fishes of Rajshahi Qureshi22 in his monograph of freshwater fishes of Pakistan included 133 species, most of which occur in Bangladesh. Various studies from 1973-2017 showed that rivers have higher species diversity (Table 3) than beels (wetlands). Paira river shows the highest (114) and Karnafully showed the lowest (27) species diversity. According to Table 3, Tulshiganga river occurred the lower average species biodiversity during study period. Considering Table 2 and 3, the recent study showed that the fish species is gradually declining from the river Tulsiganga due to various manmade and natural causes.
| Fig. 2: | Percentage contribution of different families in species composition in the river |
| Table 1: | List of fish species recorded in Tulsiganga river during study period |
| LC: Least Concern, NT: Near threaten, VU: Vulnerable, DD: Data deficient, NE: Not evaluated | |
| Table 2: | Percentage of Icthyofaunal diversity |
| Table 3: | Species abundance reported by various researchers from Bangladesh |
| Fig. 3: | Shannon-wiener index for different fish groups in the Tulsiganga river |
During questioner review among local fishermen, this study found that 18 species were common, 14 species were less common and 3 species were vulnerable. About 1 vulnerable species, 22 were less concern, 2 near threaten, 1 data deficient and 9 fish species not evaluated in International Union for Conservation of Nature (IUCN) red list (Fig. 5). According IUCN23 only 1 species from study is vulnerable. Rahman et al.3 reported 8 vulnerable species from Hakaluki hoar, Bangladesh. Mohsin et al.13 reported 2 critically endangered, 3 endangered and 5 vulnerable fish species from Andharmanik river. Galib et al.24 found 10 vulnerable, 10 endangered and 6 critically endangered species from river Choto Jamuna. The present study found, 22 less concern, 2 near threaten, 1 data deficient and 9 not evaluated fish species (Table 1).
Diversity Index: Rahman et al.19 reported a lower H (Shannon-wiener index) value of Eels which is opposite of present study. Carp and Catfish were higher H in present study which is also supported by Rahman et al19. Lower H value observed (Fig. 3) for Glassfish and other species during present study. Rahman et al.19 also showed a lower value of D (Simpson’s dominance index) for Carps which is reveled opposite (Fig. 4) in present study.
| Fig. 4: | Simpson’s dominance index for different fish groups in the Tulsiganga river |
| Fig. 5: | Red list status (IUCN) and local status of available fishes |
The lower D value was for Perch in this study and higher of Eels which is supported by Rahman et al.19. Shukla and Shing25 studied three stations in Aami river and showed Shannon-wiener index (H) in site-1 as 0.0213 followed by site-2 (0.0088) and the lowest in site-3 (0.00422). The Simpson’s dominance index (D) value as high at site-1 (0.064) and site-2 (0.0280) and low at site-1 (0.0133). May be the fish availability and environmental factors are liable behind it. Margalef’s index (d) of Fish family richness was 3.35 where in Rahman et al.19 the species richness was 5.13 for all reported fish population. From here the future endangered group of fish (Perch) were easily detected.
This study found some of less concern and vulnerable ichthyofaunal species that can be beneficial for the livelihood of fishermen12 as well as governmental development. This study will help the researcher to uncover the critical areas to innovate the suitable way of applying correct conservation program to increase the biodiversity around the Tulsiganga river. Thus, a new way of ichthyofaunal conservation may introduce in future by applying natural or induced breeding to increase the least concern and vulnerable species as well.
CONCLUSION AND FUTURE RECOMMENDATIONS
In this study, 36 open water species with 6 orders were identified in which, Channiformes and mastacem beliformes were newly reported species and cypriniform was highly abundant (44.44%) specie. Crap and Catfish were higher Shannon-wiener index in present study. Tulshiganga river is a vast livelihood for many fisherman. Due to lower diversity of fishes, it became not only venerable for fish but also risky for fishermen. Necessary steps are recommended to protect the biodiversity by conducting further conservative research in this area.
SIGNIFICANCE STATEMENT
This study found some of less concern and vulnerable ichthyofaunal species that can be beneficial for the livelihood of fishermen 42 as well as governmental development. This study will help the researcher to uncover the critical areas to innovate the suitable way of applying correct conservation program to increase the biodiversity around the Tulsiganga River. Thus, a new way of ichthyofaunal conservation may introduce in future by applying natural or induced breeding to increase the least concern and vulnerable species as well.