The population size structure and length–weight relationships (LWRs) are fundamental tools in fishery science, providing valuable insights into the health, dynamics, and management of fish populations and contributing to the sustainable use of aquatic resources. The data used in this study were estimates from the main small pelagic fishes exploited in the Gambia. They were collected using surface and bottom gillnets between November 2020 and October 2021 during scientific fishing operations. The main small pelagic fish size composition showed a modal class of 20 cm for Ethmalosa fimbriata , 21 cm for Sardinella aurita , 22 cm for Sardinella maderensis , and 30 cm for Trachurus trecae. The parameter b value of these fish species ranged from 1.6831 to 2.9461, and the correlation coefficient ranged from 0.81 to 0.95. Statistical LWRs for all species were very significant. Information obtained is essential in reviewing and establishing basic management measures for depleted shared pelagic stocks in the Gambian fisheries and the sub‐region. In the context of poor data fisheries, such results also encourage the Gambian government and intergovernmental subregional organizations to support data collection in the long term.