Food-web dynamics in the Portuguese continental shelf ecosystem between 1986 and 2017: Unravelling drivers of sardine decline

Szalaj, Dorota; Torres, María Ángeles; Veiga-Malta, Tiago; Angélico, Maria Manuel; Sobrinho-Gonçalves, L.; Chaves, Corina; Alcoforado, B.; Garrido, Susana; Ré, Pedro; Cabral, Henrique N.; Silva, Alexandra

doi:10.1016/j.ecss.2021.107259

Cited by 11 publications

(12 citation statements)

References 81 publications

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“…Fishing mortality and observed biomass data used in this study were also used as inputs of the EwE model, describing the PCSE between 1986 and 2017. The static version of this model was developed by Veiga- Malta et al (2019) and further updated and fitted to 32 years of time-series data by Szalaj et al (2021). Moreover, modelled biomass and ecosystem indicators data used in the study come as an output of this EwE model.…”

Section: Data and Modelmentioning

confidence: 99%

“…The use of these data allows for the assessment of the changes that occurred in the PCSE at the whole ecosystem level. Model description and details regarding model parametrization are available in the study by Szalaj et al (2021). In summary, the model covers the area of the Portuguese Continental Shelf (0-200 m; ICES subdivisions IXa), consists of 33 functional groups (Figure 3) and includes three fishing fleets: bottom trawl (BT), pelagic and multi-gear.…”

Section: Data and Modelmentioning

confidence: 99%

“…Observed biomass data consisted of the biomass data aggregated into 20 functional groups (Table 1). These data were used to calibrate the PCSE EwE model between 1986 and 2017 (Szalaj et al, 2021). When possible we used the outputs of stock assessment models as biomass estimates (i.e., sardine, hake and horse mackerel).…”

Section: Observed Biomass Datamentioning

confidence: 99%

“…Modelled biomass data for 33 functional groups that range from plankton to marine mammals (Figure 3 and Table 1) were obtained from the EwE model fitted to the time series for the PCSE between 1986 and 2017 (Szalaj et al, 2021). A full list of functional groups used in this study is presented in Supplementary Table 1.…”

Section: Modelled Biomass Datamentioning

confidence: 99%

“…Fishing has been documented as a major driver of the marine ecosystems worldwide (e.g., Pauly et al, 1998;Coll et al, 2008;Llope et al, 2011). Moreover, it has been highlighted as an important driver of the PCSE (Szalaj et al, 2021). Variable names marked by * means that for time series representing this variable shift was detected at p ≤ 0.1 significance level.…”

Section: Fishingmentioning

confidence: 99%

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Detecting Regime Shifts in the Portuguese Continental Shelf Ecosystem Within the Last Three Decades

et al. 2021

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Marine ecosystems are affected by diverse pressures and consequently may undergo significant changes that can be interpreted as regime shifts. In this study we used integrated trend analysis (ITA) that combines multivariate statistics and methodologies to identify abrupt changes in time-series, in order to test a hypothesis about the occurrence of regime shifts in the Portuguese continental shelf ecosystem (PCSE). We used two types of data describing ecosystem drivers (fishing mortality and environmental/climatic indices) and ecosystem state (observed and modelled biomass and ecosystem indices). Modelled biomass and ecosystem indices were outputs of Ecopath with Ecosim temporal model parametrised for PSCE between 1986 and 2017. The analyses indicated that the regime shifts in the PCSE have occurred during three periods in the last three decades: “early regime” until the mid-1990s, followed by “transition regime” in-between and “late regime” since the mid-2010s. The detected regime shifts are characterised by changes in the pelagic community that became more dominant when compared to the demersal community and shifted from sardine, the main fishing resource, abundant in the “early regime”, to other less valuable pelagic fishes such as chub mackerel that dominated the “late regime”. The “early regime” was characterised by high catch, a larger proportion of demersal species, and higher diversity while, the “late regime” was represented by lower catch, an increase in higher trophic level (TL) predatory fish and lower diversity. Moreover, the “late regime” showed lower resilience and reduced maturity when compared to the “early regime”. Changes described in the ecosystem were probably related to (1) the shift in the north Atlantic environmental conditions that affected small pelagic fish (SPF) and lower TLs groups, (2) reduction in fishing pressure, and (3) internal triggers, related to the indirect trophic interactions that might have benefited higher TL fish and impacted the pelagic community. In the context of PCSE management, this study highlighted a need to consider the possibility of regime shifts in the management process. For example, regime specific harvest rates and environmental reference points should be considered when an indication of abrupt change in the ecosystem exists.

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Section: Data and Modelmentioning

confidence: 99%

Section: Data and Modelmentioning

confidence: 99%

Section: Observed Biomass Datamentioning

confidence: 99%

Section: Modelled Biomass Datamentioning

confidence: 99%