Assessing the Rigidity of the River Continuum Concept to Fish Species in a Fluvially Dominated Southern African Coastal System

A continuous gradient of physical and biological processes exists within a river system from headwaters to mouth, according to the River Continuum Concept. In this study, the River Continuum Concept was used to compare patterns in fish assemblages and diversity trends to Remane predictions. The findings show that species diversity is low near the estuary's mouth and increases upstream. While the presence of several marine and estuarine species increased species diversity upstream in the river due to the dominance of freshwater fishes, it decreased downstream due to the presence of several marine and estuarine species. These patterns are consistent with the biogeographical trend of decreasing species richness along the South African coast from east to west. Based on the findings of this study, the River Continuum Concept ignores plasticity, which is evident in species that use transitional waters. As a result, the concept is insufficiently valid for the Orange River Estuarine Continuum, and a new concept known as the “River-Estuarine Continuum” has been proposed.

The River Continuum Concept: lessons from the past and perspectives for the future

The River Continuum Concept (RCC) is a milestone in stream ecology because of its comprehensive evaluation of the structure and function of lotic ecosystems. Linking stream physical and geomorphological attributes with patterns in biodiversity, functional traits, and metabolism dynamics, this theory describes downstream gradients in community composition and ecosystem processes. The aim of this review is to evaluate how the RCC, 40 years from its publication in the Canadian Journal of Fisheries and Aquatic Sciences, has influenced basic and applied research in stream ecology, focusing on the most important contributions and recent developments. This work puts into perspective the historical importance of the RCC in the scientific process and integrates past and recent theories, including metacommunity and metaecosystem theories and the river network perspective, to predict taxonomic and functional diversity of benthic communities. Thus, this review provides a unifying overview of the historical context of the field for exploring basic and applied ecological questions to the next generation of stream ecologists.

Fish checklist of Perak River, Malaysia

Out of the 1000 species of freshwater fish documented in the South-East Asian Tropics, 420 species can be found in Malaysia. Based on experimental gill net studies, Perak River recorded a total of 107 fish species, which comprises of 33 families with Cyprinidae as the dominant family, with 43 species. The fluctuating number of species and species replacement in the upstream direction in this river reflects the orientation of the River Continuum Concept. Gradient changes of salinity, habitat heterogeneity, water velocity and riverbed materials are some of the factors that may contribute to the fluctuation and species replacement.