UW Aquatic & Fishery Sciences Quantitative Seminar

Allan Hicks

UW Aquatic & Fishery Sciences

Delay-difference, age-structured, and state-space models: are hyphenated models useful for assessing orange roughy stocks?

Abstract

Age-structured models are commonly used to assess orange roughy stocks. However, many of the life-history parameters are assumed known and a deterministic biomass trajectory is often estimated. A more simple model is the delay-difference model, which can capture most of the same dynamics as an age-structured model. Through simulation, this study compares the ability and usefulness of three models to estimate a true biomass trajectory and catchability parameters using CPUE and survey data. The models are a delay-difference model with observation error, an age-structured model with observation error, and a state-space delay-difference model with both process and observation error. Each model is then fit to real data from the largest orange roughy stock in New Zealand.