On Assessment of the Atlantic Menhaden Population

The Atlantic menhaden population is assessed using Statistical Catch-at-Age/Length (SCAA/L) methodology. Two dominant issues have important impacts on the assessment results. The first is selectivity doming, which is clearly preferred by the data, and leads to higher estimates of spawning biomass in absolute terms. However, considerably greater differences in results follow depending on which of the incompatible JAI (recruitment) and SAD/NAD (ages 1 to 6+) survey indices are preferred for inclusion in the assessment. Current resource trends are indicated to be negative for the former, and positive for the latter, for which the relative weighting accorded to size composition data in the likelihood also plays a role. Suggestions are made for areas of further investigation to attempt to reduce the wide range of plausible results forthcoming from these assessments.