Journal article
Time-variant productivity in biomass dynamic models on seasonal and long-term scales
Section for Ecosystem based Marine Management, National Institute of Aquatic Resources, Technical University of Denmark1
National Institute of Aquatic Resources, Technical University of Denmark2
Section for Marine Living Resources, National Institute of Aquatic Resources, Technical University of Denmark3
The productivity of fish populations varies naturally over time, dependent on integrated effects of abundance, ecological factors, and environmental conditions. These changes can be expressed as gradual or abrupt shifts in productivity as well as fluctuations on any time scale from seasonal oscillations to long-term changes.
This study considers three extensions to biomass dynamic models that accommodate time-variant productivity in fish populations. Simulation results reveal that neglecting seasonal changes in productivity can bias derived stock sustainability reference levels and, thus, fisheries management advice. Results highlight the importance of biannual biomass indices and their timing relative to the peaks of the seasonal processes (i.e. recruitment, growth, mortality) for the estimation of seasonally time-variant productivity.
The application to real-world data of the eastern Baltic cod (Gadus morhua) stock shows that the model is able to disentangle differences in seasonal fishing mortality as well as seasonal and long-term changes in productivity. The combined model with long-term and seasonally varying productivity performs significantly better than models that neglect time-variant productivity.
The model extensions proposed here allow to account for time-variant productivity of fish populations leading to increased reliability of derived reference levels.
Language: | English |
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Publisher: | Oxford University Press |
Year: | 2020 |
Pages: | 174-187 |
ISSN: | 10959289 and 10543139 |
Types: | Journal article |
DOI: | 10.1093/icesjms/fsz154 |
ORCIDs: | Mildenberger, Tobias , Berg, Casper Willestofte , Pedersen, Martin Wæver , Kokkalis, Alexandros and Nielsen, J. Rasmus |