Stock assessment of the shorthead anchovy Encrasicholina heteroloba in Tanzania's coastal waters

Abstract

The shorthead anchovy Encrasicholina heteroloba is a small pelagic species of significant economic and nutritional importance in Tanzania. However, reliable stock assessment remains challenging because of limited data. This study evaluates the status of E. heteroloba in Tanzanias coastal waters and provides management insights for sustainable exploitation. A total of 32,324 specimens were sampled between July 2023 and December 2024. Length-frequency data were cleaned, bootstrapped, and analyzed using the ELEFAN routine to estimate von Bertalanffy growth parameters and mortality rates. Stock biomass and abundance were estimated through virtual population analysis. Estimated parameters were asymptotic length (L{infty}) = 8.42 cm total length, growth coefficient (K) = 2.08, growth performance index ({emptyset}') = 2.19, current fishing mortality (Fcurr) = 0.85, exploitation rate (Ecurr) = 0.40, and length at first capture (Lcurr) = 6.10 cm total length. Natural mortality (M) was 1.25 and total mortality (Z) was 2.10. Overall biomass and stock abundance were 72,725 metric tons and 4.37 x 1010 individuals, respectively. Estimates of biological reference points were F0.1= 1.57, F0.5 = 1.06, and Fmax= 3.34. The results indicate that the stock of E. heteroloba in this region is currently underexploited. Fishing mortality could be moderately increased to enhance yield-per-recruit sustainably.