The Influence of Stock Assessment Frequency on the Achievement of Fishery Management Objectives

Abstract

<p>Because of resource limitations with respect to both funding and staff expertise, there is growing interest among fishery management agencies in moving from annual to less-frequent assessments of fish stocks. We conducted simulations based on Lake Whitefish <i>Coregonus clupeaformis</i> populations in the Laurentian Great Lakes to evaluate (1) how statistical catch-at-age assessment frequency, the time lag between data collection and assessment, and approaches to setting target harvests in the years between assessments affected the achievement of management objectives; and (2) how the outcomes were influenced by the quality of assessment data, features of the populations, and characteristics of the fisheries exploiting the populations. We found that as assessments became less frequent, relative yields were reduced and the risk of stock depletion and interannual variation in yield increased. The effects of less-frequent assessments were ameliorated in populations with greater levels of productivity and when target mortality was lower. Conversely, the effects of assessment frequency were largely insensitive to changes in recruitment variation or the quality of assessment data. A 1-year lag between data collection and assessment when assessments were conducted annually primarily affected the risk of stock depletion and the interannual variation in yield. As recruitment variation increased, relative yield also became sensitive to the 1-year lag. Approaches to setting harvest targets in years between full assessments were less important than assessment frequency, and no single approach consistently outperformed other rules. Although populations with low productivity were the most sensitive to changes in assessment frequency and the lag between data collection and assessment, the management of those populations benefited to a greater extent from implementation of an appropriate target mortality rate than from more-frequent assessments or removal of the 1-year lag.</p> <p>Received November 18, 2015; accepted March 9, 2016 Published online July 7, 2016 </p