Isabel Domingos

Epidemiology and pathology of Anguillicoloides crassus in European eel Anguilla anguilla from the Tagus estuary (Portugal).

Infection of the European eel Anguilla anguilla by the swimbladder nematode Anguillicoloides crassus was investigated for the first time at 5 sampling sites in the Tagus estuary (Portugal). A total of 332 yellow eels were examined, revealing a prevalence of 56% and a mean intensity of 3.2 lumen worms per swimbladder. The effect of the hosts sex and size on parasitism descriptors was studied. Only total length (TL) was considered a significant determinant, with larger eels harbouring a higher number of nematodes. Eels were parasitized in 4 of the 5 sampling sites, with prevalence values following the salinity gradient along the Tagus estuary. No signs of the nematode were observed in the most saline site. Variations in the intensity of infection were only apparent when a large geographic scale including a wide temperature range was considered. Although 68% of the analysed eels showed pathological damage to the swimbladder caused by the parasite, injuries were relatively reduced in comparison with other studies. No effect of the infection on the condition of the body and on liver condition was detected. However, considerable spleen enlargement was observed with increasing parasite load, which could be related to the bloodsucking activity of this nematode.

Modelling the recruitment of European eel (Anguilla anguilla) throughout its European range

European 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.

Impact of freshwater inputs on the spatial structure of benthic macroinvertebrate communities in two landlocked coastal lagoons

Landlocked 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 usage

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 Sao Tome 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 Sao Tome and Principe area, namely Pomadasys jubelini, Bostrychus africanus, Dalophis cephalopeltis and the introduced species Oreochromis mossambicus.

Factors affecting the distribution of fish communities in the river Mondego and main tributaries

Fish assemblage structure and factors affecting the distribution of fish communities were examined for 23 sites in the River Mondego basin during the summer of 1998. The cyprinids Rutilus macrolepidotus, Barbus bocagei, Chondrostoma polylepis, Rutilus alburnoides, Leuciscus corolitertii and Gobio gobio were the most abundant species among the 25 taxa forming the freshwater fish community. Species richness was generally higher in impoundments and in the watershed downstream from the AçudePonte dam, at Coimbra The anadromous species were restricted to the area downstream from the Açude-Ponte, except for a landlocked population of Alosa alosa in the Aguieira reservoir. ln the river stretches less affected by the construction of dams, the two main factors responsible for the structure of fish communities were the altitude and the distance from the source. R. rnacro/epidotus and R. albumoides were dominant closer to the source, at lower altitudes, whereas L corolitertii dominated in upper reaches. As the distance from the source increases and the altitude decreases, the fish communities become dominated by B. bocagei and C. polylepis,larger fishes that take advantage of the increase in river depth.

Trophic ecology of a coastal fish assemblage in Portuguese waters

INRB/IPIMAR, Instituto de Investigac¸a˜o das Pescas e do Mar, Avenida de Brasi´lia, 1449-006 Lisboa, PortugalThe diets and trophic ecology of the dominant fish species from the marine coastal region of Aveiro (north-westernPortugal) caught during a summer survey were studied. Mysids were the most important prey group for the fish assemblageanalysed. As a consequence, there was a high dietary overlap between species and a low incidence of piscivory. Nevertheless,a clear segregation of trophic niches was observed, with one group (comprising the species Chelidonichthys cuculus,Callionymus lyra, Dicologlossa cuneata and Pomatoschistus lozanoi) showing a stronger preference for infaunal epibenthicprey, such as polychaetes and amphipods, another group (including Arnoglossus imperialis, Arnoglossus laterna,Chelidonichthys obscurus, Chelidonichthys lucernus, Echiichthys vipera, Pagellus acarne and Trisopterus luscus)preying mostly upon suprabenthic prey, mainly mysids, and a third group (Engraulis encrasicolus and Trachurustrachurus) feeding largely on planktonic prey like copepods. Some species, including A. imperialis, C. lyra, E. vipera,T. trachurus and T. luscus, showed ontogenic diet shifts that may be related to the habitat occupied by different size-classes and/or to their ability to capture prey of different size.Keywords: fish community, trophic structure, ontogenic shifts, niche overlap, mysids, piscivory

The decline in recruitment of the European eel: new insights from a 40-year-long time-series in the Minho estuary (Portugal)

The decline in recruitment of the European eel: new insights from a 40-year-long time-series in the Minho estuary (Portugal) Maria Jo~ao Correia*, José Lino Costa, Carlos Antunes, Giulio De Leo, and Isabel Domingos MARE, Marine and Environmental Sciences Centre, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisbon, Portugal Departamento de Biologia Animal, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisbon, Portugal CIIMAR, Center for Marine and Environmental Research, Universidade do Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal Aquamuseu do Rio Minho, Parque do Castelinho, 4920-290 Vila Nova de Cerveira, Portugal Department of Biology, Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA *Corresponding author: tel.:þ 351 217 500 148; e-mail: mjcorreia@fc.ul.pt.