Porobic_Garate_whole_thesis.pdf (7.95 MB)
An ecosystem based management framework for the Juan Fernandez Ridge fisheries
thesisposted on 2023-05-28, 10:14 authored by Javier Porobic GarateJavier Porobic Garate
The Juan Fernandez Ridge Ecosystem (JFRE) is a vulnerable marine ecosystem (VME). Located on the coast of central Chile, the ecosystem covers the Juan Fernndez Archipelago and an adjacent group of seamounts. This ecosystem has unique biological and oceanographic features, characterized by small and discrete geographical units, a high degree of endemism (marine and terrestrial species) and the presence of mesoscale oceanographic structures promoting a high degree of connectivity within the system. Two commercial fishing fleets have historically operated in this ecosystem: i) a long-term traditional coastal artisanal fleet from the local tightly-knit fishing community, and ii) a mainland-based industrial demersal finfish fishery operating on the seamounts, currently closed due to overexploitation. Because of the vulnerability of this ecosystem and the potential for expansion of both the artisanal and industrial fishing activities towards higher levels of finfish exploitation, an assessment of the sustainability of this ecosystem under both current and increased level of fishing exploitation is extremely relevant to those pondering the future of the system, its resources, conservation and sustainable use. In the first place, to lay the foundations of this work, an analysis of the Chilean fishing management system and its move towards Ecosystem-based management was undertaken. Secondly, an Atlantis end to end model was configured and calibrated for the JFRE. Atlantis is a spatially explicit whole of ecosystem model that accounts for the main components of this ecosystem. In addition, a set of tools were created to help in the calibration and configuration of this ecosystem model. Atlantis is a spatially explicit whole of ecosystem model that accounts for the main components of the JFRE. The implemented model has a high degree of skill in representing the observed trends and fluctuations of the JFRE. The model shows that the industrial fishing has a fairly localized impact on both target species and bycatch. In the case of alfonsino, it has a strong direct effect leading to a substantial depletion of the biomass of this species. For its other major target species, orange roughy, the industrial fleet has a much smaller direct effect because the total removed corresponds to a small portion of the total biomass. This indicates that it is likely that the observed decrease in catches may be associated with other biological processes. The model also shows that the artisanal fisheries have a relatively low impact on the ecosystem, mainly via the lobster fishery. The lobster fishery is the source of the greatest artisanal fishing effort in the system and has the greatest impact. The depletion of large sized lobster leads to an increase in the population of sea urchins. Although this increase is not suffcient, as yet, to cause substantial flow-on effects to other groups, caution is advised in case extra pressure leads the ecosystem towards a regime shift. A preliminary exploration of future fisheries options indicates that a moderate increase in the fishing effort focused on other species of finfish and crustaceans is unlikely to have a significant impact on the ecosystem. Therefore, it seems appropriate to maintain, or reduce, fishing effort on the lobster and increase it on other species. This would have two positive outcomes: i) it would ensure the sustainability of the individual resources and ii) it would enhance the productive diversity of this vulnerable ecosystem by spreading the fishing effort onto other species avoiding its concentration on the spiny lobster fishery and the associated management problems. Fisheries management of vulnerable marine ecosystems, such as the JFRE, can greatly benefit from the use of modeling tools such as Atlantis. These type of exploratory tools can provide information on the current and future status of the ecosystem, and allow testing of alternative management strategies to help ensure the sustainability of resources and the ecosystem.
Rights statementCopyright 2019 the author Chapter 2 appears to be the equivalent of a post-print version of an article published as: Porobic, J., Fulton, E. A., Frusher, S., Parada, C., Haward, M., Ernst, B., Stram, D., Implementing ecosystem-based fisheries management: lessons from Chile's experience, Marine policy, 97, 82-90 Chapter 3 appears to be the equivalent of a pre-print version of an article published as: Porobic, J., Fulton, E. A., Parada, C., Frusher, S., Ernst, B., Manr¿í¬±quez, P., 2019. The impact of fishing on a highly vulnerable ecosystem, the case of Juan Fernandez Ridge ecosystem, PLoS one, 14(2): e0212485. Copyright: Copyright 2019 Porobic et al. It is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License, https://creativecommons.org/licenses/by/4.0/ which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.