Distribution and Expansion of Alien Fish Species in the Karun River Basin, Iran

Abstract

We assessed the distribution of alien fishes in the Karun River Basin, Iran. Fish were collected from 39 sites during the November–December 2018 low-flow period. In total, 39 fish species from nine orders and 14 families were documented. Among these, 10 species were alien to the basin (986 individuals; 15.7%). Four species were the most abundant alien species and primarily in impounded, downstream reaches. Redundancy analysis (RDA) was conducted to identify the extent of changes in alien fish assemblages with environmental parameters. RDA1 and RDA2 accounted for 36.24% and 25.33% of the variation of alien species, respectively. Altitude, depth, electrical conductivity, water temperature, turbidity, dissolved oxygen, and river width were the most significant parameters affecting alien species distributions. We present a dual-pathway cause-and-effect hypothesis proposing that alien fish species presence causes declines in the ecological status of native fish communities. We then explore how human-induced aquatic ecosystem degradation creates opportunities for alien species to invade new ecosystems, further impacting native fish communities. Our study contributes insight into the cause and effect of the presence of alien fish species in the Karun River Basin and emphasizes the urgency of conservation measures to protect this critically endangered watershed.

Multi-Interacting Natural and Anthropogenic Stressors on Freshwater Ecosystems: Their Current Status and Future Prospects for 21st Century

“…Fish are aquatic, craniate, and gill-bearing, such as hagfish, lampreys, cartilaginous, and bony fish, and are naturally mostly ectothermic and relatively abundant in most bodies of water in nearly all aquatic environments, exhibiting greater species diversity than any other group of aquatic vertebrates. In spite of the fact that fish are ecological keystones for aquatic environments, ecological indicators, and important resources for humans [312][313][314][315][316][317][318][319][320], some of them can sometimes be undesirable.…”