Vol.:(0123456789) Environmental Science and Pollution Research (2024) 31:15571–15579 https://doi.org/10.1007/s11356-024-32117-3 RESEARCH ARTICLE Diversity and genetic structure of freshwater shark Wallago attu: an emerging species of commercial interest Shahid Sherzada 1,2  · Nimra Hussain 2  · Ali Hussain 3  · Mohamed A. M. El‑Tabakh 4  · Saeed Akram Khan 1 Received: 18 April 2023 / Accepted: 17 January 2024 / Published online: 1 February 2024 © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024 Abstract Pakistan has natural freshwater resources acting as a hotspot for diverse fish fauna. However, this aquatic fauna is declining at an alarming rate due to over-exploitation, habitat degradation, water pollution, climate change, and certain anthropogenic activities. The freshwater shark, Wallago attu, is a popular edible catfish inhabiting these freshwater ecosystems. Habitat degradation, overfishing, and human activities are heavily impacting the natural population of this species. So, sound knowl- edge about its population structure is necessary for its proper management in natural waters. The current study involves utilizing two mtDNA markers (COI, Cytb) to assess the genetic structure and differentiation among W. attu populations of Pakistani Rivers. Genetic variability analysis indicated a high haplotype (0.343 ± 0.046–0.870 ± 0.023) and low nucleotide diversity (0.0024 ± 0.012–0.0038 ± 0.018) among single and combined gene sequences, respectively. Overall, River Indus was populated with more diverse fauna of Wallago attu as compared to River Chenab and River Ravi. Population pairwise, F st values (0.40–0.61) were found to be significantly different (p < 0.01) among three Riverine populations based upon com- bined gene sequences. The gene flow for the combined gene (COI + Cytb) dataset among three populations was less than 1.0. The transition/transversion bias value R (0.58) was calculated for testing of neutral evolution, and it declared low genetic polymorphism among natural riverine populations of Wallago attu. The current study’s findings would be meaningful in planning the management and conservation of this economically important catfish in future. Keywords Wallago attu · Genetic diversity · Mitochondrial DNA · COI · Cytb · Mitochondrial DNA; Genetic diversity; Population structure Introduction Freshwater ecosystems are home to diverse aquatic flora and fauna. These ecosystems are now facing threats due to gradual loss of biodiversity. The physical, chemical, and biological components of freshwater ecosystems are heavily impacted by anthropogenic pressure (Navarro-Ortega et al. 2015). World Wide Fund for Nature (WWF) has reported that the current rate of population decline in freshwater fishes is two times more than marine water fish fauna (WWF 2016). For surveillance and conservation, genetic charac- terization of natural fish populations is mandatory. Genetic- based approaches are very valuable to better understand the genomic basis of adaptive divergence in fish populations (Kumari et al. 2017). Wallago attu, commonly known as helicopter fish, fresh- water shark, or Asian sheat catfish, is found in the natural waters of South and Southeast Asia from Pakistan to Indo- nesia. It is placed among the 10 largest catfish species in the world (Hogan 2011). In Pakistan, it is locally named “Mul- lee” or “Jarko” (Mirza 2003). Wallago attu inhabits rivers, lakes, and reservoirs and is usually captured by traditional fishing methods (Montana et al. 2011; Renjithkumar et al. 2016). Responsible Editor: Bruno Nunes * Shahid Sherzada shahid.sherzada@gcu.edu.pk 1 Department of Zoology, Government College University Lahore, Lahore, Pakistan 2 Department of Fisheries and Aquaculture, University of Veterinary and Animal Sciences, Lahore, Pakistan 3 Institute of Zoology, University of the Punjab, Lahore, Pakistan 4 Zoology Department, Faculty of Science, Al-Azhar University, Cairo, Egypt