Fish Diversity and Its Threatened Status of the Dharla River in Bangladesh

Fish diversity of a riverine ecosystem became reduced due to different manmade and natural calamities. This study investigated the present fish biodiversity status of the Dharla River located (25.8103° N, 89.6487° E) in the northern part of Bangladesh from January to December 2018. In this study, the existing fish biodiversity status of the Dharla River was estimated in terms of diversity indices and threatened status (both global and local). Data was collected from the three sampling sites of the river using different fishing gears and three selected fish markets located in the Kurigram district of Bangladesh. A total of 76 fish species were identified belonging to 8 orders, 26 families and 57 genera. The Cyprinidae was the most dominant family represented by 14 species followed by the Danionidae (13 species), Bagridae (8 species) and few minor families. Apart from the indigenous species, nine exotic fish species were also recorded. The Shannon-Weaver diversity (H), Pielous evenness (e) and Margalef richness (D) indices ranged from 3.00 to 3.71, 0.62 to 0.94 and 3.94 to 7.95, respectively. Out of 76 indigenous species, 28 species (37%) were identified as threatened in Bangladesh, which included critically endangered (4), vulnerable (9) and endangered (15) species. Indiscriminate fishing through poisoning and destructive fishing gears were identified as the major threats to fish biodiversity of the Dharla River. Thus, the river serves as considerable support for threatened indigenous fishes. Therefore, necessary steps are needed to stop destructive fishing, establish permanent fish sanctuaries and proper monitoring for maintaining sustainable biodiversity in the Dharla River.

Fishermen’s perceptions and experiences toward the impact of climate change and anthropogenic activities on freshwater fish biodiversity in Côte d’Ivoire

Africa’s freshwater ecosystems are impacted by many threats due to climate change and several anthropogenic activities. In Côte d’Ivoire, the economy relies mostly on agriculture, which covers around 64% of the land surface. The study aimed to investigate Côte d’Ivoire fishermen’s perception of climate change, its drivers and other anthropogenic activities impacting freshwater fish biodiversity. The fish species locally threatened in the Ivorian freshwater ecosystems were also investigated. Face to face interviews and a structured questionnaire were used. The data obtained were analysed using descriptive statistics such as frequency, percentage, means, and standard deviation, minimum and maximum. The multinomial logit regression was also applied to test factors that influence fishermen’s awareness and perception of climate change and their perception of change in fish abundance. The results show that around 72.7% of fishermen were aware of climate change. Decreases of precipitation (87.9%) and increases of temperature (76.1%) were observed by fishermen. Also, a significant decrease in fish quantity was observed by respondents. Climate change and anthropogenic activities such as gold mining, water withdrawal, use of small-mesh fishing nets, overfishing, industrial waste pollution, pesticides use for agricultural purposes along watersheds, obnoxious fishing practices and population growth, were highlighted as the main reasons for this decline. Species such as Lates niloticus, Heterotis niloticus, Parachanna obscura, Malapterurus electricus, Sarotherodon galilaeus, Tilapia zillii, Polpyterus endlicheri and Labeo coubie were listed by fishermen as locally threatened within Ivorian freshwater ecosystems. Actions and policies are needed to be taken by local authorities to ensure the sustainability of fisheries resources. The information obtained from this study constitutes a prerequisite for developing and implementing studies or policies aimed at mitigating and combating the negative effect of climate change and anthropogenic activities on the Ivorian freshwater ecosystem.

Impact of Irrigational Runoff on Fish Biodiversity in River Ngadda, Maiduguri – Borno State

Irrigation is a dry season agricultural activity that was known to man for centuries. Agricultural runoff has been identified as the major nonpoint sources of pollution into surface waterbodies which changes the physico – chemical parameters thereby impacting on the biodiversity of such ecosystem. River Ngadda receives pollutants from the irrigational sites along the river bank. The study was aimed at assessing the impact of irrigation on fish biodiversity in river Ngadda, Maiduguri, Borno State, Nigeria. The objectives of the study were to determine the physico – chemical parameters and examine the fish biodiversity of the river. The river was divided into 4 sampling Stations. Water samples was collected biweekly for the period of 6 months from 4 sampling stations. The physico – chemical qualities (total nitrogen (TN), ammonium (NH4+), total phosphorus (TP), total organic carbon (TOC), total dissolved solids (TDS), turbidity (Tur) and total suspended solids (TSS) were determined using standard methods. Capture and recapture method was employed to determine the relative abundance of fish species using Lincoln index. The mean Total Nitrogen (TN) ranges from 5.02 mg/L – 8.31mg/L, mean ammonium (NH4+) ranges from 0.93mg/L – 2.01, mean Total phosphorous (TP) ranges from 0.07mg/L – 1.81mg/L. mean Total Organic Carbon (TOC) ranges 5.87mg/L – 7.45mg/L, mean Turbidity (Tur) ranges from 27mg/L – 31mg/L, mean Total Dissolved Solids (TDS) ranges 198NTU – 298NTU, mean Total Suspended Solids ranges from 34mg/L – 47mg/L and mean surface water Temperature ranges from 26°C – 28°C. A total of 4 families and 10 species of fishes were identified in the sampling stations.

Seasonal Variation of Water Quality Parameters and Their Impact on Fish Biodiversity Indices of Hasadanga Beel: A Case Study

Fish diversity indices and their correlation with seasonal fluctuation of physicochemical parameters of Hasadanga beel was aimed to be studied. A three-year study on the relationship between the seasonal fluctuation of water quality parameters and fish biodiversity indices was conducted in Hasadanga Beel, a floodplain lake of Nadia district, West Bengal to measure the ecological health of the lake. Samples of water and fish species were collected at pre-monsoon, monsoon and post-monsoon period from 2015-2017 to estimate physicochemical parameters of water and fish biodiversity indices i.e. Shannon-Weaver species diversity index, Margalef’s Species richness index, Pielou’s Species evenness index and Simpson’s index of dominance. Total of 34 different fish species belonging to 8 Orders were found during the study period which varies seasonally. Water temperature (20.0-31.4 °C), pH (7.70-8.75), dissolved oxygen (3.9-5.0 mg/l), Free CO2 (0.0-15.0 mg/l), total alkalinity (156-193 mg/l), hardness (113-145 mg/l), and BOD (1.03-1.94 mg/l) values varied significantly (p<0.05) between three seasons. Shannon-Weaver species diversity index (Hꞌ) is ranged between 1.2911-1.3502, Margalef’s species richness index (D) is measured between 12.72-14.15, Pielou’s species evenness index (Jꞌ) is recorded between 0.8829-0.9140 and Simpson’s index of dominance (ID) is ranged between 0.05346-0.07139. Hꞌ has positive correlation with pH, alkalinity and hardness whereas negative correlation with temperature, free CO2, DO and BOD. D has positive correlation with pH, free CO2, DO and hardness whereas negative correlation with temperature, alkalinity and BOD. Jꞌ has positive correlation with temperature, pH, alkalinity and hardness and whereas negative correlation with free CO2, DO and BOD. ID has positive correlation with temperature, free CO2, DO and BOD whereas negative correlation with pH, alkalinity and hardness. The obtained result suggests that various water quality parameters specially temperature, dissolved oxygen and pH are the key factors to regulate the fish biodiversity indices and should be taken into consideration for making policies for sustainable use of floodplain lakes.

Mesophotic fish communities of the ancient coastline in Western Australia

Marine diversity across the Australian continental shelf is shaped by characteristic benthic habitats which are determined by geomorphic features such as paleoshorelines. In north-western Australia there has been little attention on the fish communities that inhabit an ancient coastline at ~125 m depth (the designated AC125), which is specified as a key ecological feature (KEF) of the region and is thought to comprise hard substrate and support enhanced diversity. We investigated drivers of fish species richness and assemblage composition spanning six degrees of latitude along sections of the ancient coastline, categorised as ‘on’ and ‘off’ the AC125 based on depth, across a range of habitats and seafloor complexity (~60–180 m depth). While some surveyed sections of the AC125 had hard bottom substrate and supported enhanced fish diversity, including over half of the total species observed, species richness and abundance overall were not greater on the AC125 than immediately adjacent to the AC125. Instead, depth, seafloor complexity and habitat type explained patterns in richness and abundance, and structured fish assemblages at both local and broad spatial scales. Fewer fishes were associated with deep sites characterized by negligible complexity and soft-bottom habitats, in contrast to shallower depths that featured benthic biota and pockets of complex substrate. Drivers of abundance of common species were species-specific and primarily related to sampling Areas, depth and substrate. Fishes of the ancient coastline and adjacent habitats are representative of mesophotic fish communities of the region, included species important to fisheries and conservation, and several species were observed deeper than their currently known distribution. This study provides the first assessment of fish biodiversity associated with an ancient coastline feature, improving our understanding of the function it plays in regional spatial patterns in abundance of mesophotic fishes. Management decisions that incorporate the broader variety of depths and habitats surrounding the designated AC125 could enhance the ecological role of this KEF, contributing to effective conservation of fish biodiversity on Australia’s north west shelf.