Croatian Journal of Fisheries, 2020, 78, 21-32
M. Ali et al. (2020): Fish Biodiversity in the Andharmanik River
© 2020 Author(s). This is an open access article licensed under the Creative Commons Attribution-NonCommercial-NoDerivs License 
(http://creativecommons.org/licenses/by-nc-nd/3.0/)
21
DOI: 10.2478/cjf-2020-0003 CODEN RIBAEG ISSN 1330-061X (print)
1848-0586 (online)
FISH DIVERSITY IN THE ANDHARMANIK RIVER SANCTUARY IN BANGLADESH
Mir Mohammad Ali1,2,3, Md. Lokman Ali2, Md. Jalilur Rahman3*, Md. Abdul Wahab3
1 Department of Aquaculture, Sher-e-Bangla Agricultural University, Dhaka-1207, Bangladesh
2 Department of Aquaculture, Patuakhali Science and Technology University, Patuakhali-8602, Bangladesh
3 WorldFish, Bangladesh & South Asia Office, Banani, Dhaka-1213, Bangladesh
*Corresponding Author, Email: jrhmn2@gmail.com
ARTICLE INFO ABSTRACT
Received: 19 June 2017
Accepted: 8 January 2019
Loss of fish biodiversity, especially in the inland and coastal areas, is a 
major concern in sustainable fish production. Indiscriminate fish catch, 
climate change and many other anthropogenic activities synergistically 
affect fish biodiversity. To formulate a sustainable fish biodiversity 
conservation plan, fish biodiversity in the Andharmanik River, a 40-km-long 
Hilsa shad sanctuary in the southern part of Bangladesh, was assessed. 
The study was conducted to understand the status of fish species diversity 
through sampling in three sampling stations between December 2014 
and November 2015. A total of 93 fish species were found belonging to 
66 genera, 45 families and 14 orders. Perciformes (27.65%) was found 
to be the most dominant order, followed by Cypriniformes (20.21%), 
Siluriformes (21.28%) Clupeiformes (7.45%) Mastacembeliformes (4.26%) 
and Channiformes (4.26%). Out of the 93 fish species of the river, the 
percentage compositions of the vulnerable, endangered, critically 
endangered and not threatened were found to be 14%, 11%, 6% and 59%, 
respectively. Four population indices viz. Shannon-Wiener’s diversity index 
(H), Simpson's dominance index (D), Simpson's index of diversity (1-D) 
and Margalef's index (d) were applied to demonstrate species diversity, 
richness and evenness of fish species in sampling areas, and the overall 
values of the indices were 2.70-3.51, 0.10-0.12, 0.88-0.90 and 7.84-8.19, 
respectively. The main threats to fish biodiversity were reviewed and the 
measures for fish biodiversity conservation of the river recommended. 
Indiscriminate fishing using biodiversity destructive gears, as well as losing 
hydrological and ecological connectivity with the surrounding habitats, 
were identified as major threats to biodiversity in the Andharmanik River. 
Effective sanctuary-based co-management, immediate actions for habitat 
enhancement to conserve and improve fish biodiversity in the river were 
recommended. Necessary steps to improve hydrological and ecological 
connectivity for habitat protection and elimination of all destructive 
fishing gears in order to conserve biodiversity in the Andharmanik River 
were also suggested.
Keywords:
Andharmanik River
Sanctuary
Fish diversity
Biodiversity index 
How to Cite Ali, M.M., Ali, M.L., Rahman, M.J., Wahab, M.A. (2020): Fish diversity inthe 
Andharmanik river sanctuary in Bangladesh. Croatian Journal of Fisheries, 
78, 21-32. DOI: 10.2478/cjf-2020-0003.
Croatian Journal of Fisheries, 2020, 78, 21-32
M. Ali et al. (2020): Fish Biodiversity in the Andharmanik River
© 2020 Author(s). This is an open access article licensed under the Creative Commons Attribution-NonCommercial-NoDerivs License 
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22
INTRODUCTION
Loss of biodiversity and food insecurity are two major 
concerns in the 21st century. In many inland and coastal 
areas this concern focuses sharply on the demise of fishery 
resources. Indiscriminate fish catch, climate change 
and many other anthropogenic activities synergistically 
affect fish biodiversity (Nagelkerken et al., 2017). Given 
the ever-growing demand of fish consumption for over 
160 million people in Bangladesh, fish biodiversity and 
fisheries sustainability are identified as key concerns, 
but management solutions to address food security and 
biodiversity are few and far between. 
Bangladesh is known as a riverine country because of the 
large number of rivers distributed across it (Banglapedia, 
2012; Rahman, 2015; USAID, 2016). It has various 
biodiversity-rich inland bodies of water. About 800 rivers, 
including tributaries and distributaries, flow through 
the country, constituting a waterway of a total length 
of approximately 24,140 km, with massive potential for 
fish biodiversity (Banglapedia, 2012; Department of 
Fisheries (DoF), 2013). It has the third highest aquatic fish 
biodiversity in Asia, after China and India, with about 800 
species in fresh, brackish and marine waters (Hussain and 
Mazid, 2001). Among these species, Bangladesh contains 
260 freshwater fish species; minnows, catfish, eels, perch, 
gobies, clupeids, carps, snakeheads and prawns constitute 
the majority (DoF, 2009).
The Andharmanik River is one of five sanctuaries declared 
by the Government of Bangladesh where fishing is 
restricted for a certain period of time, especially to 
protect the juvenile Hilsa shad called 'Jatka'. The entire 
catchment of the 40-km-long Andharmanik River is an 
important Hilsa shad sanctuary in southern Bangladesh 
(Wahab and Golder, 2016).
The role of fisheries in the national economy has always 
been significant and has been the main source of animal 
protein, employment opportunities, food security, foreign 
income and socio-economic improvement (Siddiq et al., 
2013; Ali et al., 2014a, 2014b, 2014c; Ali et al. 2015a, 
2015b). This sector contributes 3.65% of the total GDP 
and 23.81% of agricultural GDP. More than 2% of export 
earnings come from this sector as well. About 60% of a 
person’s daily animal protein intake is supplemented by 
fish. About 11% of the population is dependent directly 
and indirectly on fisheries for their livelihood (DoF, 2016).
Southern Bangladesh is rich in fisheries resources. Among 
the 58 rivers in the Barisal Division in southern Bangladesh, 
the Andharmanik is predicted to be the future economic 
hub of the region (Banglapedia, 2012). The productivity 
and enrichment of a body of water is dependent on its 
biodiversity. The species diversity of a body of water is 
generally influenced by both human activity and natural 
calamity. The most impactful human activities include, 
but are not limited to, the construction of dams, bridges 
and roads, pollution and the use of different type of illegal 
gears. At the same time, natural causes that can affect 
fish biodiversity include flood, indiscriminate fluctuation 
of temperature and salinity, other natural disasters, 
phytoplankton bloom and siltation. It is very important 
to conserve the biodiversity of a body of water, and 
it is not too late to take initiatives for the conservation 
of biodiversity of coastal rivers and maintain optimum 
utilization level (Fu et al., 2003; Eros and Scmera, 2010; 
Rao et al., 2014, Ali et al., 2015a).
Though a number of studies on the biodiversity of fishes 
have been conducted around the world (Goswami et al., 
2012; Rixon et al., 2005; Shinde et al., 2009; William et al., 
2010), such studies have been more limited in Bangladesh 
(Rahman et al., 2012; Hossain et al., 2012; Siddiq et al., 
2013; Ali et al., 2014c; Hossain et al., 2014; Ali et al., 
2015a, 2015b; Hanif et al., 2015). Except for the studies 
by Hossain et al. (2014) and Hanif et al. (2015), most 
research efforts in Bangladesh lack analyses of diversity 
indices, which many studies have used in different parts of 
the world (Penczak et al., 1994; Nyanti et al., 2012). As the 
Andharmanik River is a vital river of the southern region 
of Bangladesh and a sanctuary of the most important 
fishery - the Hilsa, the study of biodiversity assessment 
and conservation is very important for the fisheries sector. 
The present article focuses on the assessment of fish 
biodiversity, reviews the main threats to fish biodiversity 
and provides recommendations for fish biodiversity 
conservation in the Andharmanik River, Bangladesh.
MATERIALS AND METHODS
Study area
The study was conducted in the Andharmanik River, 
located in Kalapara Upazila, Patuakhali district of southern 
Bangladesh (Fig. 1).
This 40-km-long coastal river is a confluence of freshwater, 
brackish water and marine waters. It is connected to 
another large coastal river, the Galachipa, on one end 
and joins the Bay of Bengal at the Kuakata beach point. 
Additionally, there are many freshwater canals that join 
the rivers. The water becomes nearly fresh in the rainy 
season, and in the dry season it transforms to estuarine and 
marine water (up to 16 ppt salinity). Therefore, fish species 
of all three habitats are available in the river depending 
on the seasons. To collect fish species specimens, the 
study area was divided into three sampling stations 
(Figure 1): Kalapara (S1, 21°55'35.65''N 90°08'21.70''E), 
Hajipur (S2, 21°54'06.37''N 90°06'58.88''E) and Alipur (S3, 
21°52'22.68''N 90°05'52.97''E) areas of the river. The fish 
samples were periodically collected from these three sites 
starting from December 2014 to November 2015.
Croatian Journal of Fisheries, 2020, 78, 21-32
M. Ali et al. (2020): Fish Biodiversity in the Andharmanik River
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23
Fig 1. Map showing the Andharmanik River, indicating three sampling sites (S1- Kalapara, 21°55'34.65''N 90°08'21.70''E; 
S2- Hajipur, 21°54'06.37''N 90°06'58.88''E and S3- Alipur, 21°52'22.68''N 90°05'52.97''E of Kalapara Upazila, Patuakhali, 
Bangladesh)
Sampling
Fish samples were collected from the catch of fishermen in 
the Andharmanik River. A total of 15 seine net fishermen 
were chosen for data collection from the spots. Fish were 
usually caught by means of the traditional fishing gears 
such as seine net (Sutar jal), cast net (Jhaki jal), square 
lift net (Tar jal), conical trap (Dughair), fish angles (Borsi), 
monofilament fixed gill net (Current jal) and fish barrier 
(Thaga). Samples were also collected from fish-landing 
centres and fish markets. The specimens thus collected 
during the field visit were identified primarily in the field. 
Those which appeared difficult to identify were marked 
properly. All the identified and unidentified fish samples 
were preserved with a 10% formalin solution in plastic 
jars.
Primary data on the concerned species were collected 
from the fishermen, fish traders, local people and also 
from on the spot locations. Relevant data such as the local 
name of the collected fish samples, source, distribution 
and availability of the species were collected from the 
study sites. Secondary data was also collected from the 
District Fisheries Offices, Department of Fisheries (DoF), 
Statistical Yearbook of Bangladesh, etc. Along with these 
data, relevant published documents were also collected 
from various government agencies, autonomous bodies 
and NGOs. Research papers on the freshwater fish fauna 
of Bangladesh were also consulted in order to compile 
past data of abundance and availability for assessing 
biodiversity status.
Identification of the collected samples
The collected fish samples were identified by evaluating 
their morphometric and meristic characteristics, as well 
as the colour of the specimens, by referring to books 
such as Fish Base. The taxonomic guides were followed 
as described by Eschmeyer (2014) and Rahman (2005). 
Additionally, fish species were systematically classified 
based on Nelson’s (2006) classification.
Data analysis
Species diversity was assessed using different indices 
viz. Shannon-Wiener diversity index (H), Simpson’s 
dominance index (D), Simpson’s index of diversity (1-D), 
Margalef’s index (d) and the Evenness index (E) (Shannon, 
1949; Shannon and Weaver, 1963; Margalef 1968; Ramos 
et al., 2006).
RESULTS
Fish species abundance
The river acts as an asylum for an immense number of 
aquatic organisms, fish in particular. The present study 
represented a total of 93 species of fishes belonging to 
66 genera, 45 families and 14 orders. Scientific names, 
number of specimen under each of the species and 
International Union for Conservation of Nature (IUCN), as 
well as the Bangladeshi red list status, are presented in 
Table 1. 
Croatian Journal of Fisheries, 2020, 78, 21-32
M. Ali et al. (2020): Fish Biodiversity in the Andharmanik River
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24
Scientific Name
Number of Species Conservation Status
S1 S2 S3 Total Bangladesh Global
Congresox talabon (Cuvi-er, 1829) 120 80 58 258 NO NA
Harpadon nehereus (Hamilton, 1822) 2531 1945 2456 6932 NO NA
Anodontostoma chacunda (Hamilton, 1822) 385 391 389 1165 NO NA
Tenualosa ilisha (Hamil-ton, 1822) 15078 11908 13876 40862 NA NA
Tenualosa toli (Valenci-ennes, 1847) 1291 1626 1432 4349 NA NA
Ilisha megaloptera (Swainson, 1839) 5311 4308 5325 14944 NO NA
Setipinna phasa (Hamil-ton, 1822) 2185 2134 2356 6675 NO LC
Coilia neglecta (White-head, 1967) 3434 3856 4534 11824 NO NA
Setipinna taty (Valenci-ennes, 1848) 1138 1324 1435 3897 NO NA
Amblypharyngodon mola (Hamilton, 1822) 1124 908 1376 3408 NO LC
Amblypharyngodon mi-crolepis (Bleeker, 1853) 246 223 236 705 NO LC
Chela cachius (Hamilton, 1822) 289 189 198 676 NO LC
Esomous danricus (Hamil-ton, 1822) 405 384 678 1467 NO LC
Labeo bata (Hamilton, 1822) 46 23 35 104 EN LC
Labeo boga (Hamilton, 1822) 0 0 6 6 CR LC
Puntius gonionotus (Bleeker, 1849) 0 0 2 2 EX LC
Puntius ticto (Hamilton, 1822) 69 78 81 228 VU LC
Pethia guganio (Hamilton, 1822) 53 64 84 201 NO LC
Puntius sophore (Hamil-ton, 1822) 67 34 85 186 NO LC
Puntius sarana (Hamilton, 1822) 9 2 4 15 CR LC
Osteobrama cotio (Hamil-ton, 1822) 67 85 66 218 NO LC
Pethia conchonius (Hamil-ton, 1822) 34 39 48 121 NO LC
Salmophasia bacaila (Hamilton, 1822) 76 65 86 227 NO LC
Acanthocobitis zonalter-nans (Blyth, 1860) 0 41 28 69 NA LC
Botia dario (Hamilton, 1822) 0 1 4 5 EN LC
Lepidocephalichthys gun-tea (Hamilton, 1822) 64 41 65 170 NO LC
Lepidocephalichthys ir-rorata (Hora, 1921) 16 0 27 43 DD LC
Channa marulius (Hamil-ton, 1822) 11 13 17 41 EN LC
Channa orientalis (Bloch & Schneider, 1801) 14 13 18 45 VU NA
Channa punctatus (Bloch, 1794) 19 23 29 71 NO LC
Channa striatus (Bloch, 1794) 13 4 12 29 NO LC
Chanda nama (Hamilton, 1822) 78 23 59 160 VU LC
Chanda ranga (Hamilton, 1822) 19 22 36 77 VU LC
Pseudoambassis lala (Hamilton, 1822) 31 43 48 122 NO NT
Anabas testudineus (Bloch, 1792) 26 27 34 87 NO DD
Trichogaster fasciata (Bloch & Schneider, 1801) 207 203 190 600 NO LC
Nandus nandus (Hamil-ton, 1822) 56 43 49 148 VU LC
Table 1. Fish species abundance, distribution and conservation status in the Andharmanik River, southern Bangladesh
Croatian Journal of Fisheries, 2020, 78, 21-32
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25
Scientific Name
Number of Species Conservation Status
S1 S2 S3 Total Bangladesh Global
Badis badis (Hamilton, 1822) 4 0 3 7 EN LC
Drepane punctata (Lin-naeus, 1758) 204 192 182 578 NO NA
Eleotris fusca (Forster, 1801) 57 52 43 152 NA LC
Apocryptes bato (Hamil-ton, 1822) 504 459 608 1571 NO NA
Glossogobius giuris (Ham-ilton, 1822) 407 430 389 1226 NO LC
Taenoides anguillaris  (Linnaeus, 1758) 309 334 323 966 NO LC
Lates calcarifer (Bloch, 1790) 78 67 89 234 NA NA
Lutjanus madras (Valen-ciennes, 1831) 19 16 14 49 NO NA
Nemipterus japonicas (Bloch, 1791) 67 45 76 188 NO NA
Polynemus paradiseus (Linnaeus, 1758) 34 0 33 67 NO NA
Scatophagus argus (Lin-naeus, 1766) 2309 2298 2531 7138 NO NA
Euthynnus affinis (Cantor, 1849) 29 0 18 47 NO NA
Katsuwonus pelamis 37 28 31 96 NO LC
Pampus chinensis (Lin-naeus, 1758) 67 58 66 191 NO LC
Sillaginopsis panijus (Hamilton, 1822) 145 134 241 520 NO NA
Acanthopagrus chinshira (Kume & Yoshino, 2008) 708 653 751 2112 NA NA
Trichiurus mutica (Gray, 1831) 3497 4133 3765 11395 NO NT
Panna microdon (Bleeker, 1849) 407 379 490 1276 NO NA
Otolithoides pama (Hamil-ton, 1822) 7980 6754 8905 23639 NO NA
Johnius coitor (Hamilton, 1822) 2398 2690 2467 7555 NO NA
Arius gagora (Hamilton, 1822) 178 167 184 529 DD NT
Sperata aor (Hamilton, 1822) 34 29 23 86 VU LC
Mystus tengara (Hamilton, 1822) 30 58 57 145 VU LC
Mystus gulia (Hamilton, 1822) 341 378 398 1117 NO LC
Mystus vittatus (Bloch, 1794) 1423 1156 1287 3866 NO LC
Rita rita (Hamilton, 1822) 0 1 5 6 CR LC
Batasio batasio (Hamilton, 1822) 3 0 2 5 CR LC
Hemibagrus menoda (Hamilton, 1822) 62 56 34 152 NO LC
Clarias batrachus (Linne-aeus, 1758) 37 21 54 112 NO LC
Plotosus canius (Hamil-ton, 1822) 14 7 9 30 VU NA
Heteropneustes fossilis (Bloch, 1794) 32 24 13 69 NO LC
Ailia coila (Hamilton, 1822) 27 14 11 52 VU NT
Ailia punctata (Day, 1872) 127 76 113 316 VU DD
Clupisoma garua (Hamil-ton, 1822) 3 0 4 7 CR LC
Silonia silondia (Hamilton, 1822) 7 4 0 11 EN LC
Wallago attu (Bloch & Schneider, 1801) 23 18 25 66 NO NT
Ompok pabda (Hamilton, 1822) 5 3 3 11 EN NT
Ompok bimaculatus (Bloch, 1794) 0 2 6 8 EN NT
Croatian Journal of Fisheries, 2020, 78, 21-32
M. Ali et al. (2020): Fish Biodiversity in the Andharmanik River
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26
Scientific Name
Number of Species Conservation Status
S1 S2 S3 Total Bangladesh Global
Bagarius bagarius (Hamil-ton, 1822) 0 0 3 3 CR NT
Glyptothorax cavia (Ham-ilton, 1822) 11 9 0 20 NO LC
Macrognathus aral (Bloch & Schneider, 1801) 28 19 9 56 VU LC
Macrognathus pancalus (Hamilton, 1822) 49 64 58 171 NO LC
Mastacembelus aculeatus (Cuvier, 1832) 67 87 76 230 NO NA
Mastacembelus armatus (Lacepède, 1800) 3 2 5 10 EN LC
Monopterus cuchia (Ham-ilton, 1822) 44 39 51 134 VU LC
Tetraodon cutcutia (Ham-ilton, 1822) 56 47 38 141 NO LC
Liza parsia (Hamilton, 1822) 13 15 14 42 NO LC
Rhinomugil corsula 12 4 17 33 NO LC
Notopterus chitala (Hamil-ton, 1822) 0 8 3 11 EN NT
Notopterus notopterus (Pallas, 1769) 14 3 11 28 VU LC
Xenentodon cancila (Ham-ilton, 1822) 24 21 19 64 NA LC
Hyporhamphus limbatus (Valenciennes, 1847) 11 17 6 34 NO LC
Brachirus pan (Hamilton, 1822) 23 21 25 69 NO LC
Brachirus orientalis (Bloch & Schneider, 1801) 13 11 9 33 NO NA
Cynoglossus arel (Bloch & Schneider, 1801) 71 49 67 187 NO NA
Cynoglossus cynoglossus (Hamilton, 1822) 76 46 56 178 NO NA
LC = Least Concern, NT = near Threatened, DD = Data Deficient, NO = Not Threatened, CR = Critically Endangered, EN = Endangered, 
EX= Extinct, VU= Vulnerable, NA = Not Assessed
Out of 14 orders, Perciformes was the most dominant 
order and contributed 27.65%, followed by Cypriniformes 
(20.21%), Siluriformes (21.28%), Clupeiformes (7.45%), 
Mastacembeliformes, (4.26%) and Channiformes (4.26%), 
whereas Anguilliformes, Aulopiformes, Tetradontiformes, 
Synbranchiformes were least dominant and constituted 
1.06% each (Fig. 2).
Out of the 93 fish species, a maximum of 90 fish species 
were recorded at sampling station S3, followed by S1 
and S2 areas where 87 and 86 fish species were found, 
respectively. The highest number of individuals (59,271) 
was recorded at S3 area, followed by S1 and S2 areas 
where 56,716 and 51,417 individuals were recorded, 
respectively. Compared to the other two stations, S3 
station showed the highest species richness.
Among 93 fish species, 30 IUCN red-listed species were 
Fig 2. Percentage composition of families, genera and species under various orders of the fish species found in the 
Andharmanik River between December 2014 and November 2015
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27
recorded from the studied areas, of which 6 species were 
found to be Critically Endangered, 10 species reported 
as Endangered, 13 species were found Vulnerable (IUCN, 
2015). The percentage composition of the vulnerable, 
endangered, critically endangered and not threatened 
categories were found to be 14%, 11%, 6% and 59%, 
respectively (Fig. 3). Most of the threatened species were 
recorded at sampling site S3, followed by S1 and S2 (Fig. 
4).
Biodiversity status
The values of Shannon-Wiener index (H), Simpson’s 
dominance index (D), Simpson’s index of diversity (1-D) 
and Margalef’s index (d) of selected areas are shown 
in Fig. 5. From the studied area, the highest Shannon-
Wiener index value (3.51) was observed in S2 area and the 
lowest value (2.70) was observed in S3 area. The highest 
value of Simpson’s dominance index (0.12) was estimated 
from S1 area, followed by 0.11 in S3 and 0.10 in S2 areas, 
respectively. The highest Simpson’s index of diversity 
(0.90) was recorded from S2 area and the lowest value 
(0.88) was recorded from S1 area. The highest Margalef’s 
index value was 8.19 at S3 site, whereas the lowest value 
was 7.84 at S2 site. The highest Gibson’s Evenness value 
(0.07) was found at the S3 location, and the lowest value 
(0.03) was recorded from the S2 station (Fig. 6).
Fig 3. Conservation status of available fish species found in the Andharmanik River between December 2014 and 
November 2015 (VU= Vulnerable, EN= Endangered, CR= Critically Endangered, EX= Extinct, DD= Data Deficient, NA= 
Not Assessed)
Fig 4. Number of species under different categories of threat as per IUCN 2013 found in the Andharmanik River between 
December 2014 and November 2015
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M. Ali et al. (2020): Fish Biodiversity in the Andharmanik River
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28
Fig 5. Different fisheries diversity indexes at sampling sites of the Andharmanik River
Fig 6. Evenness of fish diversity in different areas of the Andharmanik River
DISCUSSION
This study recorded 93 fish species from the Andharmanik 
River, representing 35.47% of the country’s total fish 
species (Table 2). The species composition indicated a 
combination of marine, estuarine and freshwater species 
as the river is a confluence of freshwater, brackish-water 
and marine waters. In the rainy season, it becomes almost 
fresh and in the dry season it becomes estuarine to marine 
waters. Mohsin et al. (2014) studied the fish fauna of the 
Andharmanik River for a period of one year between 
March 2011 and February 2012 and found a total of 53 
fish species under 28 families, indicating improvement 
in biodiversity in the last few years. In fact, due to some 
recent incentive-based management measures, the 
abundance of fish species has remarkably increased and 
fishers get more species in their catches (Islam et al., 
2016; Islam et al., 2017).
However, the recorded fish species was much lower than 
some other rivers of Bangladesh (Bhuiyan et al., 2008; 
Rahman et al., 2012; Hossian et al., 2014). Hossian et 
al., 2014 found 128 species belonging to 12 orders and 
35 families from the flood plain area of greater Noakhali 
areas, so the species richness was much higher than that 
of the present findings. Higher species richness was also 
reported by some other researchers. Hossain et al. (2007) 
reported 161 species collected by different types of nets 
from the Naaf River estuary. Nabi et al. (2011) identified 
finfish species from the following areas: Chittagong 
coast (48), Moheskhali Channel (76), Karnaphuli River 
Croatian Journal of Fisheries, 2020, 78, 21-32
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29
Number of 
Species
Number of 
Family Study Area References
94 45 Patuakhali Present study (2016)
57 28
Paira River; 
Patuakhali
Rahman et al. (2016)
53 26
Lohalia River, 
Patuakhali
Ali et al. (2015a)
98 48
Pirojpur, Bhola, 
Patuakhali and 
Barguna
Hanif et al. (2015)
53 28 Andharmanik River Mohsin et al. (2014)
128 34 Noakhali Hossain et al. (2014)
251 61 Bangladesh Siddiqui et al. (2007)
265 55 Bangladesh Rahman (2005)
133 32 Rajshahi Bhuiyan et al. (1992)
106 34
Mymensingh and 
Tangail
Doha (1973)
71 25 Dhaka Bhuiyan (1964)
63 23
The Choto Jamuna 
River
Galib, et al. (2013)
Table 2. Studies on the diversity of fish species in Bangladesh 
waters
(46) estuary and Bakkhali estuary (45). Rahman (2005) 
assembled a list of 265 species of freshwater fishes 
belonging to 154 genera and 55 families from Bangladesh.
Bhuiyan (1964) gave an account of 71 species of freshwater 
fishes belonging to 45 genera and 25 families which were 
collected from the Buriganga River, Dhaka. Considering the 
variable species richness in different rivers in Bangladesh, 
the Andharmanik River may be considered as moderately 
enriched with fish species diversity. The high percentage 
of fish species revealed by the order Perciformes may 
be due to the presence of a suitable environment and 
river bottom that the members of this family prefer. 
Among those fish species, Hilsa was recorded as the most 
dominant fish species from the study areas.
Variation in species composition was observed at 
different locations in the study area due to the different 
environmental characteristics of the aquatic ecosystem. 
Loss of fish biodiversity is considered as an alarming threat 
and its conservation is the only solution to this problem. 
Hossain (2010), Ali et al. (2014c), Ali et al. (2015a) and 
Hossain et al. (2015) reported the same causes of 
decreasing biodiversity from the Padma, Chitra, Lohalia 
and Tetulia Rivers, respectively. Although the rivers are 
gradually losing their biodiversity, they still support a large 
number (30) of threatened fish species of Bangladesh. 
Rahman et al. (2012) also reported similar results on the 
case of threatened fish from the Padma River.
Different anthropogenic activities are synergistically 
affecting and reducing the water flow and water depth 
of the study area. Human activities along with increased 
fishing pressure are gradually reducing fisheries diversity 
in the Andharmanik River. The S3 area represented 
the highest number of individuals that are subject to 
relatively low human interference and thus is under-
fished and retains an optimum environmental condition. 
A biodiversity index refers to the characterisation of the 
species diversity of a sample or community by a single 
number (Magurran, 1988). Diversity is high when all 
species that make up a population community are equally 
abundant. Biodiversity index assessment was conducted 
for the analysis of fish diversity by comparing the 
estimated values within three areas of the Andharmanik 
River.
The concept of “species diversity” consists of two 
components: the number of species (or richness) and 
the distribution. The Shannon-Wiener diversity index 
represented the richness and proportion of each species, 
whereas the evenness and dominance indices showed 
the relative number of individuals in the sample and the 
fraction of common species, respectively (Hossain et al., 
2014). The highest Shannon-Wiener index was observed 
from the S2 site and the lowest value was observed in 
the S3 area. Chowdhury et al. (2011) found the Shannon-
Wiener values (H) ranging from 1.63 to 3.41 in the Naaf 
River estuary. The present study shows significantly lower 
H values due to less number of species. The H value 
usually ranges from 1.5 to 3.5 for ecological data and 
hardly exceeds 4.0, which is related with our calculated 
data. When the body of water maintains sustainable 
condition, then H values could be higher than 3.5. Alam 
et al. (2013) found H values to be from 3.29 to 3.49 in the 
Halda River; which was higher than that of the present 
study because the influence of the environmental factors 
on the Andharmanik River is higher than that of the Halda 
River. Simpson’s dominance index (D) value usually ranges 
from 0 to 1, and the higher the range of values, the smaller 
the biodiversity represented.
Simpson’s dominance index was higher in the S1 area 
and lower values were observed in stations S2 and S3. 
Considering the D value, the S2 area was found to be the 
most enriched with species diversity and the S1 site was 
found to be the least enriched with species diversity. The 
Simpson index of diversity (1-D) value also ranges between 
0 and 1; the greater value indicates the greater sample 
diversity. The dominant Simpson’s index of diversity value 
was observed in the S2 area and represented the highest 
species diversity. Evenness value ranges from 1 and 0; 
lowest Evenness value indicates a higher species diversity. 
Peak Evenness value was observed in the S3 area, whereas 
the least value was observed in the S2 area. Based on the 
Evenness value, S2 was considered a rich diversity zone. 
For breeding purposes, a number of fish species migrate 
to this river, and sampling station S2 was considered as 
the breeding zone of these species, which may be the 
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M. Ali et al. (2020): Fish Biodiversity in the Andharmanik River
© 2020 Author(s). This is an open access article licensed under the Creative Commons Attribution-NonCommercial-NoDerivs License 
(http://creativecommons.org/licenses/by-nc-nd/3.0/)
30
reason behind the highest and lowest Evenness value in 
S3 and S2 areas, respectively.
The Margalef index value is used as an indicator to compare 
the sites; generally, and depending on the species number, 
it shows deviation (Vyas et al., 2012). The Margalef index 
(d) value ranged from 7.84-8.19, which is similar to Hanif 
et al. (2015) who recorded a high Margalef’s index (d) 
of 8.67 and a low of 7.48. The maximum Margalef index 
value represents the maximum number of individuals 
in the studied area. Site S3 represented the highest 
Margalef’s index value, which indicated the presence of 
significantly higher individuals than that of the S1 and S2 
areas. Positive correlation between the Evenness index 
and Simpson’s dominance index, and a negative relation 
between the Shannon–Weiner and Evenness indices were 
observed in this study, which was similar to the values 
reported by Vyas et al. (2012) and Alam et al. (2013).
The present study showed the species abundance in 
different parts of the studied area. From the analysis 
of the different biodiversity index, it can be concluded 
that sampling station S2 is comparatively rich in fish 
biodiversity. This might be due to the fishing prohibition 
in this zone. This river acts as a home to a large number of 
globally threatened species. Compared with other rivers 
on the basis of species abundance, the Andharmanik 
River can be considered an ecological hub of southern 
Bangladesh, and therefore its biodiversity needs to be 
conserved with due diligence.
Considering the rich fish biodiversity and threats to the 
biodiversity of the Andharmanik River, a sustainable 
biodiversity conservation action plan needs to be 
formulated and implemented. Improved hydrological and 
ecological connectivity and habitat protection, as well as 
elimination of all destructive fishing gears, are urgently 
needed to conserve biodiversity (Hossain, 2014; Rahman, 
2015; Galib et al., 2018). Some destructive gears have 
been extremely harmful for juvenile fish, which include 
set-bag-nets (Behundi jal, Pona jal and Badha jal), beach 
seine nets (Ber jal, Moshari jal and Char Ghera jal) and 
small-meshed monofilament net (Current jal). Proper 
administrative initiatives would be essential to implement 
measures to control harmful gears, especially gears that 
target threatened species.
Recent Government initiatives target the incentive-based 
Hilsa fishery management, and some of these measures 
have already been effectively put into practice in Bangladesh 
(Islam et al., 2016; Islam et al., 2017). Some recent studies 
assessing the effectiveness of this incentive-based fishery 
management suggest improvements for reducing the 
capture of small-sized fish, as well as protecting the brood 
Hilsa during the peak spawning season (Mohammed and 
Wahab, 2013; Haldar and Ali, 2014; Dewhurst-Richman et 
al., 2016). An effective sanctuary-based co-management 
body should be introduced in the sanctuary to conserve 
resources in a sustainable manner. It is also essential 
to take immediate action for habitat enhancement of 
the Andharmanik River to conserve and improve fish 
biodiversity. Proper management strategies must be 
applied with an integrated approach among government, 
researchers, NGOs and donors that can conserve and 
improve the fisheries diversity of the Andharmanik River.
ACKNOWLEDGEMENTS
This work contributes to the CGIAR Research Program 
on Fish Agrifood Systems (FISH). The research was 
a collaborative work between the USAID/ECOFISH-
Bangladesh project, WorldFish and PSTU (Patuakhali 
Science and Technology University, Patuakhali). Financial 
support for the research was provided by the WorldFish 
and PSTU implemented the activities. We express our 
gratitude to the local fishers of the Andharmanik River, 
Bangladesh for helping us collect samples. Special thanks 
are extended to those unnamed fishers who helped 
in different capacities for successful implementation 
of this study. We are grateful to Dr. Adam Frick and Dr. 
Philippa Cohen for their valuable comments and inputs in 
improving the manuscript.
RAZNOLIKOST RIBA U RIJECI ANDHARMANIK, 
BANGLADESH
SAŽETAK
Gubitak biološke raznolikosti riba, posebno u kopnenim 
i obalnim područjima, jedan je od glavnih interesa 
održive proizvodnje riba. Neselektivni ulov ribe, klimatske 
promjene i mnoge druge antropogene aktivnosti sinergijski 
utječu na biološku raznolikost riba. U svrhu formuliranja 
održivog plan očuvanja biološke raznolikosti riba u 
rijeci Andharmanik, procijenjena je biološka raznolikost 
riba u 40 km dugačkom svetištu Hilsa, u južnom dijelu 
Bangladeša. Studija je provedena kako bi se utvrdio status 
raznolikosti ribljih vrsta i to uzorkovanjem na tri lokacije od 
prosinca 2014. do studenog 2015. Ukupno je pronađeno 
93 vrste riba koje pripadaju 66 rodova, 45 porodica i 14 
redova. Grgečke (27,65%) su utvrđene kao dominantni 
red, a slijede ih šaranke (20,21%), somovi (21,28%), 
sleđevke (7,45%), bodljikave jegulje (4,26%) i zmijoglave 
ribe (4,26%). Od 93 vrste ribe u rijeci, utvrđeno je udio 
osjetljivih riba 14%,, ugroženih 11%, kritično ugroženih 
6% te neugroženih riba 59%. Četiri indeksa populacije, 
Shannon-Wiener-ov indeks raznolikosti (H), Simpsonov 
indeks dominacije (D), Simpsonov indeks raznolikosti 
(1-D) i Margalef-ov indeks (d), primijenjeni su kako bi 
se prikazala raznolikost, bogatstvo i ujednačenost ribljih 
vrsta na uzorkovanim područjima. Ukupne vrijednosti 
navedenih indeksa bile su 2,70-3,51, 0,10-0,12, 0,88-0,90 
tj. 7,84-8,19. Procijenjene su glavne prijetnje biološkoj 
raznolikosti riba i preporučene mjere za očuvanje biološke 
raznolikosti ribe. Kao glavne prijetnje biološkoj raznolikosti 
u rijeci Andharmanik identificiran je neselektivni ribolov, 
Croatian Journal of Fisheries, 2020, 78, 21-32
M. Ali et al. (2020): Fish Biodiversity in the Andharmanik River
© 2020 Author(s). This is an open access article licensed under the Creative Commons Attribution-NonCommercial-NoDerivs License 
(http://creativecommons.org/licenses/by-nc-nd/3.0/)
31
koji koristi štetne mehanizme po biološku raznolikost, 
kao i gubitak hidrološke i ekološke povezanosti s okolnim 
staništima. Preporučuju se efikasno zajedničko upravljanje 
te neposredne akcije za jačanje staništa radi očuvanja 
i poboljšanja biološke raznolikosti ribe na istraživanoj 
lokaciji. Predloženi su i potrebni koraci za poboljšanje 
hidrološke i ekološke povezanosti radi zaštite staništa 
i uklanjanja svih štetnih ribolovnih alata radi očuvanja 
biološke raznolikosti u rijeci Andharmanik.
Ključne riječi: Rijeka Andharmanik, utočište, raznolikost 
riba, indeks biološke raznolikosti.
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