The theoretical basis of a new approach to data poor fisheries assessment, length-based assessment of spawning potential ratio, has been recently published. This paper describes its first application over two years to assess 12 of the 15 most numerous species of Indo-Pacific coral reef fish in Palau. This study demonstrates the techniques applicability to small-scale data-poor fisheries and illustrates the type of data required, and the assessment’s outputs. A methodology is developed for extending the principles of Beverton–Holt Life History Invariants to use the literature on related species within the Indo-Pacific reef fish assemblage to ‘borrow’ the information needed to parameterize assessments for Palau’s poorly studied stocks. While the assessments will continue to be improved through the collection of more size and maturity data, and through further synthesis of the literature, a consistent and coherent picture emerges of a heavily fished assemblage with most assessed species having SPR < 20% and many <10%. Beyond the technical aspects of this study, the relative simplicity of the data being collected and the underlying concept of spawning potential facilitated the involvement of fishers in collecting their own data and community ownership of the results.