Identification of Drivers of Change of the Gulf of Nicoya Ecosystem (Costa Rica)

Abstract

The Gulf of Nicoya is a large tropical estuary located on the Pacific coast of Costa Rica and accounts for the country's main fish production. It is increasingly impacted not only by its fisheries, but also by urbanization, tourism developments, the input of pollutants from urban centers and agriculture activities in the catchment areas of large rivers entering the gulf. Similar to other coastal ecosystems, the gulf is particularly sensitive to short-and long-term changes in the climate, such as the precipitation rate, Sea Surface Temperature, wind speed and current regimes. While the gulf has been studied for decades, until now no attempt has been made to combine the analysis of the impacts of fishing and environmental changes on the ecosystem. By following a holistic approach that uses fisheries and environmental time series data from collaborative research and simulation models, this study aims at identifying the main drivers of the observed changes in the Gulf of Nicoya ecosystem. While the model simulations indicate that variations in the catch of some target species (e.g., cephalopods and shrimps) are mainly driven by the fisheries' exploitation rates, several other species (e.g., corvina, snook, small pelagics, and crabs) are also substantially affected by climate variations, particularly during El Niño periods of high Sea Surface Temperature extremes and increased precipitation. During these periods, phytoplankton productivity and zooplankton biomass deceases with bottom-up effects on the entire food chain. Indicators of the environmental state of the system thus have to be considered along with regulations of the fishing pressure to form the basis for the development of appropriate management strategies.

Exploring multiple stressor effects with Ecopath, Ecosim, and Ecospace: Research designs, modeling techniques, and future directions

“…Many historical simulations modeled climate impacts using forcing functions based on time series of sea surface temperature, surface chlorophyll a, net primary production, or climate indices like the Pacific Decadal Oscillation Index and the Atlantic Multidecadal Oscillation Index (e.g., Arreguín-Sánchez et al, 2015;Field et al, 2006;Heymans et al, 2007;Parrish et al, 2012). Such simulations have been used to disentangle the effects of climate variations from fishing impacts, among other applications (e.g., Alms and Wolff, 2020;Shannon et al, 2008;Taylor et al, 2008a). Historical time series of biomasses obtained from field surveys and stock assessments across several ENSO cycles have also been simulated with forcing functions (Taylor et al, 2008b).…”

Identifying drivers of change during the recent two decades in the Visayan Sea using a trophic modeling approach

“…To identify the main drivers of the Visayan Sea ecosystem, the baseline model was "fit" to biomass and catch time-series using the Stepwise Fitting Procedure (Scott et al, 2016), which is an automated fitting routine in Ecosim that allows the testing of multiple models with different settings applied, including vulnerability setting adjustments, primary productivity anomalies, and fishing effort drivers. To find the best fit model, we adopted a similar procedure described by Mackinson et al (2009), which was used subsequently by other model fitting-totime-series work (e.g., Alexander et al, 2014;Alms and Wolff, 2020). Hereby, the following 12 alternative hypotheses and their corresponding scenarios were tested and compared:…”

Exploring multiple stressor effects with Ecopath, Ecosim, and Ecospace: Research designs, modeling techniques, and future directions

“…Many historical simulations modeled climate impacts using forcing functions based on time series of sea surface temperature, surface chlorophyll a, net primary production, or climate indices like the Pacific Decadal Oscillation Index and the Atlantic Multidecadal Oscillation Index (e.g., Arreguín-Sánchez et al, 2015;Field et al, 2006;Heymans et al, 2007;Parrish et al, 2012). Such simulations have been used to disentangle the effects of climate variations from fishing impacts, among other applications (e.g., Alms and Wolff, 2020;Shannon et al, 2008;Taylor et al, 2008a). Historical time series of biomasses obtained from field surveys and stock assessments across several ENSO cycles have also been forced (Taylor et al, 2008b).…”