Spatial shifts and habitat partitioning of ichthyofauna within the middle–lower region of the Pungwe Basin, Mozambique

Abstract

Freshwater resources are under stress because of anthropogenic activities and the demand for water increasing on a global scale, including hydropower. There are presently plans to expand the use of hydropower within eastern and southern Africa. A key river system identified as a potential source of energy is the Pungwe River, with the proposed Pavua Dam located within the middle reaches of the system in Mozambique. However, impoundments have been recorded to negatively influence ichthyofauna communities via alterations to water quality and discharge. Furthermore, information on the structure of the ichthyofauna community, community spatial shifts and fine-scale habitat preferences for the region are lacking. Accordingly, the research sought to address this issue, to provide baseline data as well as inform on management of the system. Ichthyofauna were collected utilising an array of passive and active techniques and species data modelled to fit spatial factors to ascertain spatial shifts. To ascertain fine-scale habitat preferences, fourth-corner modelling was undertaken to link mouth position and body shape traits to substrate composition and cover features. Spatial heterogeneity in environmental characteristics caused by the intrusion of the African Rift Valley had driven significant spatial shifts in the ichthyofauna community, with distinct groups of species occurring within the sample sites. The findings of the study indicated that the ichthyofauna community within the Muazi River were significantly different to the Pungwe River and the community will be lost from the region because of the dam footprint. Furthermore, habitat preferences were influenced by mouth position and body shape. Consequently, alteration to environmental characteristics and habitat features is likely to negatively influence the ichthyofauna community.

Increasing objectivity associated with anadromous fish redd identification using a discriminant function analysis

“…This habitat segregation maintains diversity by allowing for niche partitioning across populations or species, related to timing and physical capabilities of individuals within a particular population or species. Today, construction of large rim dams within the transition reaches of alluvial streams has been identified as a major contributor to population declines for many fish species, including salmonids, and many are now listed as endangered or threatened (Liermann et al, 2012;Desai et al, 2019). These structures are often complete barriers to migratory species, reducing available spawning habitat for many anadromous fishes and today many populations are relegated to marginal habitats further degraded by a myriad of cascading post dam processes (Barbarossa et al, 2020).…”