Auxiliary and focal assessment models: a proof-of-concept involving time-varying catchability and fishery stock-status evaluation

作者：Thorson James T^*

来源：ICES Journal of Marine Science, 2011, 68(10): 2264-2276.

DOI：10.1093/icesjms/fsr160

• catchability functional form
• data-poor
• density-dependent
• integrated assessment
• multispecies
• random effects
• random walk
• statistical catch-at-age

Many assessment models evaluate stock status, and biases can arise when time-varying processes are modelled as being time-invariant. An "auxiliary/focal" assessment process is presented, where an "auxiliary" assessment model estimates functional parameters that are used in a "focal" assessment of stock status. This process is evaluated in two steps. First, estimates of density-dependent catchability from single-or multispecies auxiliary models are compared, confirming that multispecies auxiliary models are more accurate when catch-at-age data are abundant. Possible output from the multispecies auxiliary assessment is then used in a focal model, and the results are compared with four other methods: (i) assuming that catchability is constant, (ii) ignoring fishery-dependent indices, (iii) a random-walk catchability model, and (iv) estimating density-dependent catchability without prior information. Results show that the constant catchability model leads to non-conservative biases in stock-status estimates, and a random-walk model decreases bias and has high precision when age data are available. The auxiliary/focal procedure performs best when fishery indices are used without age data, and the density-dependent model without prior information performs well with fishery and survey indices, but without age data. Different methods are optimal, therefore, depending on data availability, and the auxiliary/focal assessment process performs best of the available methods when using just fishery-dependent indices.

• 出版日期2011-11