Navegando por Autor "Coll, Marta"

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Assessing fishing impacts in a tropical reservoir through an ecosystem modeling approach
(Springer, 2018-10-31) Philip, Juliana Strieder; Minte-Vera, Carolina V.; Coll, Marta; Angelini, Ronaldo
Ecological models are useful for evaluating fishery management scenarios, as they allow researchers to investigate alternative fishing effort, as well as varying environmental and trophic interaction scenarios. Through an ecosystem modeling approach (Ecopath with Ecosim), we addressed the possible impacts of small-scale fisheries on the structure and functioning of a tropical ecosystem (Itaipu Reservoir, Brazil). We found that fishing effects and predator–prey interactions were the main drivers explaining catch trends in the Itaipu Reservoir fisheries. The mean trophic level of catch did not change throughout the analyzed time period and no losses in secondary production from exploitation (L index) were observed, indicating that Itaipu fisheries are sustainable regarding ecosystem effects. The negative impacts of introduced species on native species seem to be greater than the fishing impacts. Fishing simulations from the ecosystem Maximum Sustainable Yield (MSY) reduced the biomass of some important species in the local fishery. Regarding management advice, our results indicate that fishing efforts should not be increased for curimba (Prochilodus lineatus), pintado (Pseudoplatystoma corruscans), and jaú (Zungaro jahu). Additionally, participative management methods are important measures for local fisheries. Finally, additional research is needed to investigate how fishery management can promote the use of multispecific methods (e.g., gillnets) to control introduced species
Ecological role and historical trends of large pelagic predators in a subtropical marine ecosystem of the South Atlantic
(Springer, 2017-08-09) Bornatowski, Hugo; Angelini, Ronaldo; Coll, Marta; Barreto, Rodrigo R. P.; Amorim, Alberto F.
Large pelagic predators occupy high positions in food webs and could control lower trophic level species by direct and indirect ecological interactions. In this study we aimed to test the hypotheses: (1) pelagic predators are keystone species, and their removals could trigger impacts on the food chain; (2) higher landings of pelagic predators could trigger fishing impacts with time leading to a drop in the mean trophic level of catches; and (3) recovery in the pelagic predators populations, especially for sharks, could be achieved with fishing effort reduction. We performed a food web approach using an Ecopath with Ecosim model to represent the Southeastern and Southern Brazil, a subtropical marine ecosystem, in 2001. We then calibrated the baseline model using catch and fishing effort time series from 2001 to 2012. Afterwards, we simulated the impact of fishing effort changes on species and assessed the ecological impacts on the pelagic community from 2012 to 2025. Results showed that the model was well fitted to landing data for the majority of groups. The pelagic predators species were classified as keystone species impacting mainly on pelagic community. The ecosystem was resilient and fisheries seem sustainable at that time. However, the temporal simulation, from 2001 to 2012, revealed declines in the biomass of three sharks, tuna and billfish groups. It was possible observe declines in the mean trophic level of the catch and in the mean total length of landings. Longline fisheries particularly affected the sharks, billfish and swordfish, while hammerhead sharks were mostly impacted by gillnet fishery. Model simulations showed that large sharks’ biomasses could be recovered or maintained only after strong fishing effort reduction
Food web changes associated with drought and invasive species in a tropical semiarid reservoir
(Springer, 2017) Bezerra, Luis Artur Valões; Angelini, Ronaldo; Vitule, Jean Ricardo Simões; Coll, Marta; Sánchez-Botero, Jorge Iván
Fish and invertebrates are introduced in freshwaters around the world for commercial purposes, despite widely known impacts on food webs and biological invasions. As a proxy for artificial environments, we modeled a typical reservoir in a Brazilian semiarid region using an ecosystem approach. We compared the role of native and non-native invasive species (NIS) in the food web, between dry and wet periods, and under the influence of an extreme drought period (from 2011 to 2015), simulating the variation in fish biomasses due to decreasing consumption. Key ecosystem groups were fishes (mainly NIS), birds, and insects. Nutrient cycling was dependent on invaders, while the trophic structure was detritus based during the drought. Biomass of detritivores was almost two times higher than herbivores, and native fish species decreased abruptly in response to invaders and volume variation. The dominance of low-trophic levels (TLII) and tilapia—Oreochromis niloticus (Linnaeus, 1758) and other tilapiines—resulted from interactions among invaders, feeding behavior on benthos, and environmental seasonality, tending toward biotic homogenization (“benthification”) at the ecosystem level. An increasing relevance of detritivores with cascading effects in ecosystems subject to drought, multiple introductions, and ubiquitous food sources has clear implications for the fisheries and the water quality

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Navegando por Autor "Coll, Marta"