ABSTRACT
A strong assumption made with surplus production models is that the measure of relative abundance used provides an informative index of the relative stock abundance through time. A different but related assumption is that the quality of the effort and subsequent catch-rates remains the same through time. A possible test of whether the assumed relationship between abundance and any index of relative abundance is real and informative can be derived from the implication that, in a developed fishery, if catches are allowed to increase then it is expected that catch-per-unit-effort will begin to decline some time after. The dynamics of the stock being assessed are described using an index of relative abundance. The real-world interpretation of management targets is not always straightforward.
