Morphological Variation and Proximate Body Composition of the Freshwater Catfish Wallago attu (Bloch & Schneider, 1801): A Meta-Analysis

Abstract

Wallago attu, commonly known as the freshwater shark, mulley, or boal, is a large silurid catfish of considerable commercial and nutritional importance across South and Southeast Asia. This paper brings together published studies on the morphology, growth pattern, and proximate body composition of W. attu, with the aim of comparing length-weight relationships, morphometric and meristic characters, and nutritional composition reported from different river systems, reservoirs, and lakes, mainly in Pakistan and India. The growth coefficient (b) obtained from the length-weight relationship varied from about 2.7 to 3.5 across different water bodies, with most populations showing isometric to slightly positive allometric growth, meaning that body weight increases at close to, or slightly faster than, the cube of body length as the fish grows. Morphometric studies consistently show that total length correlates most strongly with standard length and head length, while meristic counts of fin rays are relatively stable within the species and are useful for taxonomic confirmation. Proximate composition studies show that fresh W. attu muscle typically contains around 15 to 20 percent protein, 1 to 4 percent lipid, 75 to 82 percent moisture, and 1 to 2 percent ash, although these values change with body size, sex, season, and storage condition. Larger fish and fish in better body condition generally show higher percentage protein, fat, and ash content, while moisture content changes comparatively little with body size. Taken together, the evidence indicates that W. attu is a fast-growing, protein-rich food fish whose morphometric and nutritional profile is well documented in parts of its range but would benefit from more standardised, wider-ranging sampling to support fisheries management and aquaculture development.