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- Modelling the recruitment of European eel (Anguilla anguilla) throughout its European rangePublication . Bornarel, Virginie; Lambert, Patrick; Briand, Cédric; Antunes, Carlos; Belpaire, Claude; Ciccotti, Eleonora; Diaz, Estibaliz; Diserud, Ola; Doherty, Denis; Domingos, Isabel; Evans, Derek; de Graaf, Martin; O’Leary, Ciara; Pedersen, Michael; Poole, Russell; Walker, Alan; Wickström, Håkan; Beaulaton, Laurent; Drouineau, HilaireEuropean eel (Anguilla anguilla) recruitment has been declining at least since the early 1980s at the scale of its distribution area. Since the population is panmictic, its stock assessment should be carried out on a range-wide basis. However, assessing the overall stock during the continental phase remains difficult given its widespread distribution among heterogeneous and separate river catchments. Hence, it is currently considered by the International Council for the Exploration of the Sea (ICES) more feasible to use glass eel recruitment data to assess the status of the overall population. In this study, we used Glass Eel Recruitment Estimation Model (GEREM) to estimate annual recruitment (i) at the river catchment level, a scale for which data are available, (ii) at an intermediate scale (6 European regions), and (iii) at a larger scale (Europe). This study provides an estimate of the glass eel recruitment trend through a single index, which gathers all recruitment time-series available at the European scale. Results confirmed an overall recruitment decline to dramatically low levels in 2009 (3.5% of the 1960–1979 recruitment average) and highlighted a more pronounced decline in the North Sea area compared to elsewhere in Europe.
- Long term patterns in the late summer trophic niche of the invasive pumpkinseed sunfish Lepomis gibbosusPublication . Gkenas, Christos; Magalhães, M. F.; Cucherousset, J.; Domingos, Isabel; Ribeiro, FilipeQuantifying the trophic dynamics of invasive species in novel habitats is important for predicting the success of potential invaders and evaluating their ecological effects. The North American pumpkinseed sunfish Lepomis gibbosus is a successful invader in Europe, where it has caused negative ecological effects primarily through trophic interactions. Here, we quantified variations in the late summer trophic niche of pumpkinseed during establishment and integration in the mainstem of the Guadiana river, using stomach content analyses over a period of 40 years. Pumpkinseed showed a shift from trophic specialization during establishment to trophic generalism during integration. These results were concomitant with an increase in diet breadth that was accompanied by higher individual diet specialization particularly in large individuals. Irrespective of their drivers, these changes in trophic niche suggest that the potential ecological effects of pumpkinseed on recipient ecosystems can vary temporally along the invasion process.
- Ecological aspects and potential impacts of the non-native hydromedusa Blackfordia virginica in a temperate estuaryPublication . Marques, Filipa; Angélico, Maria Manuel; Costa, José Lino; Teodósio, Maria Alexandra; Presado, Patrícia; Fernandes, António; Chainho, Paula; Domingos, IsabelThe hydrozoan Blackfordia virginica has been reported over a wide geographical area, although it is mainly restricted to scattered records within estuarine areas of temperate and tropical regions. The aim of this study was to understand the spatial and temporal variability of an established population of this non-indigenous species on a temperate estuarine ecosystem, and its impacts over the plankton community. Sampling was conducted from 2011 to 2013 in the Mira estuary (Portugal) and higher densities were observed during the summer of 2013, with a maximum of 1689.3 medusae.m−3. Spatially, higher abundances of medusae were associated with sites of higher abundance of oyster shells and higher percentage of hard substrate in the river bed. Smaller jellyfish were sampled in the vicinity of these hard substrate locations, suggesting these might be habitats for polyp fixation. A higher potential predation impact on the copepod population along the estuary was estimated for the summer of 2013, with a median half life of 6.1 days.
- The decline in recruitment of the European eel: new insights from a 40-year-long time-series in the Minho estuary (Portugal)Publication . Correia, Maria João; Costa, José Lino; Antunes, Carlos; De Leo, Giulio; Domingos, IsabelIn the past three decades the European eel Anguilla anguilla experienced up to 99% decline in recruitment in some parts of its distribution range. In addition to this long-term trend, glass eel recruitment exhibits significant inter-annual variability partially explained by large-scale oceanographic processes as well as local-scale meteorological and hydrological variables. A 40-year long time series of glass eel fishery catch in the Minho estuary, Portugal, was used to assess (a) whether local recruitment followed the general pattern of decline of A. anguilla observed elsewhere, and (b) whether environmental variables may explain inter-annual fluctuations in glass eel recruitment in the Minho estuary. The analysis shows that, in contrast to the majority of coastal systems in northern Europe and the Mediterranean, CPUE of glass eel in the Minho estuary did not exhibit a marked decline between 1974–2015 and never dropped below 20% of the 10-year mean (1974–1983), taken as baseline. The difference between the recruitment trend observed in the Minho river and that reported by WGEEL for wider European geographical scales highlights the need to calculate recruitment indices with a higher geographic resolution to better support the assessment of the status of the European eel population.
- Abundance, seasonal patterns and diet of the non-native jellyfish Blackfordia virginica in a Portuguese estuaryPublication . Marques, Filipa; Chainho, Paula; Costa, José Lino; Domingos, Isabel; Angélico, M.M.Blackfordia virginica, a non-indigenous hydrozoan introduced in many systems around the world, has been observed in the Mira estuary, southwest of Portugal, since 1984. Monthly sampling (January 2013–January 2014) at a fixed location with high abundance of the medusae confirmed the occurrence of a seasonal cycle associated with temperature and photoperiod. The beginning of the medusa cycle occurred in May immediately after the spring zooplankton bloom during April. Examination of the gut contents of B. virginica medusae revealed that copepods, the most abundant group in the zooplankton community, were highly predated. Barnacle nauplii, decapod crustacean larvae and anchovy eggs were also identified in the guts. The medusae showed positive selection for copepods, and negative selection for barnacle nauplii, decapod crustacean larvae and anchovy eggs. The mortality rate of copepods (used as a model prey group) induced by medusae predation was estimated and showed the potential impact of this species in the ecosystem, ranging between 2.34 d−1 and 0.02 d−1, with a minimum copepod half-life of 0.30 days.
- Impact of freshwater inputs on the spatial structure of benthic macroinvertebrate communities in two landlocked coastal lagoonsPublication . Félix, Pedro; Correia, Maria; Chainho, Paula; Costa, José Lino; Chaves, Maria Luisa; Cruz, Teresa; Castro, João J.; Mirra, C.; Domingos, Isabel; Silva, A. C. F.; Cancela Da Fonseca, LuísLandlocked lagoons are naturally stressed environments. They are strongly influenced by freshwater input which not only varies naturally, but which is also impacted by anthropogenic activities. This study investigated the direct influence of freshwater discharges on the distribution patterns and abundance of benthic communities in two neighbouring landlocked coastal lagoons, assessing the whole system and the confluence area of each tributary. Sampling occurred in the wet and dry seasons of 2011 at two distances from freshwater discharge locations. Both lagoons were colonized by species from two different pools, freshwater and marine. Freshwater flow rates had a direct influence on the spatial structure of the benthic communities of brackish-water/freshwater interface areas, where also specific taxa can act as early indicators of freshwater input variations. The intensity of this influence is highly dependent on lagoon size, creating spatial heterogeneity or affecting the entire system. The benthic fauna at the confluence of the tributary that depends almost exclusively on groundwater showed the lowest variability, suggesting that the biogeochemical nature of the groundwater may be a central cause for setting specific ecotones. The results suggest that benthic communities of landlocked coastal lagoons can be highly impacted by flow reduction from freshwater aquifers under drought conditions or water abstraction activities.
- Mangrove fish of São Tomé Island (Gulf of Guinea): new occurrences and habitat usagePublication . Félix, Pedro; Chainho, Paula; Lima, R. F.; Costa, José Lino; Almeida, Armando; Domingos, Isabel; Brito, A. C.Mangroves are recognised as important nursery and feeding areas for resident and inshore fish species. However, the importance of West African mangroves to the life cycle of fish communities remains poorly studied. The present study is the first record of fish species in tropical insular mangroves for this region and its aim was to assess habitat usage by fish species. Two mangroves of São Tomé Island (Praia das Conchas and Malanza) were sampled with a multihabitat approach and using different fishing gear to maximise the diversity of fish species collected. Several environmental parameters were also measured. Both mangroves are nursery and opportunistic feeding grounds for fish species, as well as settlement areas for resident species. The highest number of both juveniles and adults (inshore and residents) was observed at the Malanza mangrove, which is also the largest and has the highest habitat heterogeneity. Four new occurrences were reported for the São Tomé and Principe area, namely Pomadasys jubelini, Bostrychus africanus, Dalophis cephalopeltis and the introduced species Oreochromis mossambicus.