2020 journal article
An integrated tagging and catch-curve model reveals high and seasonally-varying natural mortality for a fish population at low stock biomass
FISHERIES RESEARCH, 232.
author keywords: Weakfish; Tagging; Fishing mortality; Natural mortality; Catch-curve; Integrated tag-return and catch-curve model
UN Sustainable Development Goal Categories
14. Life Below Water
(Web of Science; OpenAlex)
15. Life on Land
(Web of Science)
Source: Web Of Science
Added: November 24, 2020
Rebuilding of exploited fish stocks at low biomass requires accurate mortality estimates. Weakfish (Cynoscion regalis) abundance is at historical lows caused by an increasing instantaneous total mortality (Z) in recent years, but uncertainty exists regarding the relative importance of instantaneous fishing mortality (F) and natural mortality (M) to Z. Data from a tag-return study and catch-curve of weakfish in North Carolina were analyzed jointly using a Bayesian statistical framework to estimate seasonal and annual mortality (i.e., F, M, and Z). We accounted for key auxiliary parameters in the tag-return portion of the model (i.e., tag-reporting rate and tag loss) through field studies and an experimental design, including use of high-reward tags and double tagging. Estimates of Z from the joint model were similar in magnitude to the weakfish stock assessment. From mid-2014 to 2017, we estimated a constant annual instantaneous mortality rate of 0.05 yr−1 (95 % credible interval [CrI]: 0.04, 0.07) for F and 2.33 yr−1 (CrI: 2.10, 2.6) for M. In the most recent stock assessment, estimates of M had an upper bound of 1.0; thus, our findings suggest that these estimates of M are biased low and F biased high. Our seasonal analyses showed that a large portion of mortality occurred from fall to spring, coinciding with weakfish migration and overwintering periods on the continental shelf. Through an integrated modeling approach, our study provides insights into the magnitude, timing, and sources of weakfish mortality, and enhances understanding of weakfish population dynamics to guide management strategies.