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- Conservation activities in the Olo riverPublication . Martinho, António; Teixeira, Amílcar; Varandas, SimoneThe management model of sport fishing in the Olo River ZPR makes eleven years of its existence in the present year. This watercourse extends over a significant area of the Alvão Natural Park, flowing through valleys embedded in different municipalities. These studies carried out in 2007 and 2013 allowed the design of a Sport Fishing Management Plan at the catchment scale. This watercourse has been subject to a special regulation (Olo River Reserved Fishing Area), since 2008. Results showed that is now possible to better know the age, growth, physical condition of the fish communities, as well as their relation with the different habitats types. The information collected over this time period permitted the adoption of measures to improve the conservation status of aquatic ecosystems such as management of the main fish species (Salmo trutta), and recovery of riparian vegetation. The production of river trout in the Marão Hatchery from parents caught in the Olo river upper reaches and the lodgment of this progeny in the same areas (ex-situ conservation action) together with the banks plantation with Salix spp., Fraxinus spp. and Alnus glutinosa, were practices used. The success of the introduction of embryonated eggs and newborn brown trout fry should be confirmed by new monitoring. As regards the afforestation actions, these proved fruitless. Habitat conservation and recovery actions (removal of litter, consolidation of banks with riparian planting, repopulation with fry and embryonated eggs with genetic material from the river itself, exclusive use of fishing gear in accordance with catch and release practice, ...) were designed to increase and improve the distribution of native fish populations. Also, awareness-raising actions developed with fishermen and other development agents promoting sustainable fishing practices of exploited resources should be continued, contributing to the improvement of the conservation status of these natural resources.
- Fishing for hosts: larval spurting by the endangered thick-shelled river mussel, Unio crassusPublication . Aldridge, David C.; Brian, Joshua I.; Cmiel, Adam; Lipinska, Anna; Lopes-Lima, Manuel; Sousa, Ronaldo; Teixeira, Amílcar; Zajac, Katarzyna; Zając, TadeuszUnderstanding the life-history characteristics of endangered species is crucial to their conservation, management, and predicting their responses to environmental change (Stark et al., 2004). Host specificity is central to the evolutionary diversification and conservation of the Unionida (Barnhart et al., 2008; Modesto et al., 2018). In the North American mussels of the Ambleminae subfamily, specificity toward a restricted host fish range that shares the same microhabitat as the mussel has resulted in remarkable morphologies and behaviors that dramatically increase the likelihood of attachment and successful transmission of larvae (glochidia).
- Phylogeny of European Anodontini (Bivalvia: Unionidae) with a redescription of Anodonta exulcerataPublication . Riccardi, Nicoletta; Froufe, Elsa; Bogan, Arthur E.; Zieritz, Alexandra; Teixeira, Amílcar; Vanetti, Isabella; Varandas, Simone; Zaccara, Serena; Nagel, Karl Otto; Lopes-Lima, ManuelFreshwater bivalves are highly threatened and globally declining due to multiple anthropogenic impacts, making them important conservation targets. Because conservation policies and actions generally occur at the species level, accurate species identification and delimitation is critical. A recent phylogenetic study of Italian mussel populations revalidated an Anodonta species bringing the number of known European Anodontini from three to four species. The current study contributes to the clarification of the taxonomy and systematics of European Anodontini, using a combination of molecular, morphological and anatomical data, and constructs phylogenies based on complete mitogenomes. A redescription of A. exulcerata and a comparative analysis of morphological and anatomical characters with respect to the other two species of Anodonta present in the area are provided. No reliable diagnostic character has emerged from comparative analysis of the morphometric characters of 109 specimens from 16 sites across the Italian peninsula. In fact, the discriminant analysis resulted in a greater probability of correct assignment to the site of origin than to the species. This confirms the difficulties of an uncritical application of visual characters for the delimitation of species, especially for Anodontinae.
- Invasive crayfishes as a threat to freshwater bivalves: Interspecific differences and conservation implicationsPublication . Meira, Alexandra; Lopes-Lima, Manuel; Varandas, Simone; Teixeira, Amílcar; Arenas-Arenas, Francisco José; Sousa, RonaldoFreshwater bivalves have suffered major global declines, being the introduction of invasive alien species (IAS) an important, but not well studied, mechanism of threat. This study assessed the predator-prey relationship between two non-native crayfish species (Procambarus clarkii and Pacifastacus leniusculus) and three native (Anodonta anatina, Potomida littoralis and Unio delphinus) and one non-native (Corbicula fluminea) freshwater bivalve species through experiments in laboratory and validation under natural conditions (Sabor River basin, Portugal). All native bivalve species were preyed both in laboratory and in the field; however, both crayfish species were unable to prey C. fluminea. Predation was dependent on crayfish and bivalve species but was not affected neither by crayfish nor bivalve sizes. In the laboratory, the most preyed species by both crayfishes was A. anatina. On average, this species was preyed at least 12% more than other species, when crayfishes had a choice. Similar results were found in the field. We also found signs of competition between both crayfishes, being P. clarkii more dominant and aggressive as this species, on average, manipulated the bivalves 63.6% more times and 24:33 min longer than P. leniusculus, and initiated 55.8% more agnostic bouts. Our results support the idea that P. clarkii and P. leniusculus can affect native freshwater bivalves, but clear interspecific differences were detected. Both crayfishes may have direct and indirect impacts on bivalve populations by increasing mortality or by reducing their fitness. In addition, since both crayfishes do not prey C. fluminea, they offer this IAS another advantage over native bivalves. Given the widespread distribution of both P. clarkii and P. leniusculus and the threatened status of many freshwater bivalves, the dynamics and impacts of this relationship should be taken in account in the implementation of management measures devoted to the conservation of native freshwater bivalves.
- From the lab to the river: determination of ecological hosts of Anodonta anatinaPublication . Dias, Ana Rita; Teixeira, Amílcar; Lopes-Lima, Manuel; Varandas, Simone; Sousa, Ronaldo1. Coextinction is the simplest form of secondary extinction and freshwater mussels (Bivalvia, Unionida) may be particularly prone to this phenomenon as their life cycle includes an obligatory parasitic larval stage on fish hosts. 2. The main aims of this study were to determine the possible ecological fish hosts of Anodonta anatina (Linnaeus, 1758) in several rivers of the Douro basin in northern Portugal and to assess possible spatial and temporal differences in glochidial (larval) loads. In order to achieve this, electrofishing was conducted from December to April, the fish fauna was characterized, and levels of infestation with A. anatina glochidia were determined. 3. Native cyprinid species, mainly Luciobarbus bocagei (Iberian barbel) and Squalius carolitertii (northern Iberian chub), together with the non-native Lepomis gibbosus (pumpkinseed sunfish) and Alburnus alburnus (common bleak), were found to have the highest glochidial loads. Clear differences in infestation between rivers and throughout time were detected, with an infestation period from January to March, and with the Tâmega River having the highest prevalence. 4. Anodonta anatina is able to infest a variety of fish species, and this together with earlier studies showed that the metamorphosis into juveniles occurs mainly in native cyprinid species, although non-native species like common bleak can also be considered suitable hosts. However, the larvae infesting other non-native species, such as the pumpkinseed sunfish, do not metamorphose and can be considered ‘dead ends’. 5. Overall, the results reported here are important for the conservation of A. anatina (and other unionoid species) because several Iberian rivers (and worldwide) have been subjected to the extirpation of native fish species and the introduction of non-native fish species. Therefore, careful assessments of fish communities should be conducted to assess possible negative interactions with freshwater mussels.
- Conservation activities in the Olo riverPublication . Martinho, António; Teixeira, Amílcar; Varandas, SimoneThe management model of sport fishing in the Olo River ZPR makes eleven years of its existence in the present year. This watercourse extends over a significant area of the Alvão Natural Park, flowing through valleys embedded in different municipalities. These studies carried out in 2007 and 2013 allowed the design of a Sport Fishing Management Plan at the catchment scale. This watercourse has been subject to a special regulation (Olo River Reserved Fishing Area), since 2008. Results showed that is now possible to better know the age, growth, physical condition of the fish communities, as well as their relation with the different habitats types. The information collected over this time period permitted the adoption of measures to improve the conservation status of aquatic ecosystems such as management of the main fish species (Salmo trutta), and recovery of riparian vegetation. The production of river trout in the Marão Hatchery from parents caught in the Olo river upper reaches and the lodgment of this progeny in the same areas (ex-situ conservation action) together with the banks plantation with Salix spp., Fraxinus spp. and Alnus glutinosa, were practices used. The success of the introduction of embryonated eggs and newborn brown trout fry should be confirmed by new monitoring. As regards the afforestation actions, these proved fruitless. Habitat conservation and recovery actions (removal of litter, consolidation of banks with riparian planting, repopulation with fry and embryonated eggs with genetic material from the river itself, exclusive use of fishing gear in accordance with catch and release practice, ...) were designed to increase and improve the distribution of native fish populations. Also, awareness-raising actions developed with fishermen and other development agents promoting sustainable fishing practices of exploited resources should be continued, contributing to the improvement of the conservation status of these natural resources.
- Effects of an extreme drought on the endangered pearl mussel Margaritifera margaritifera: a before/after assessmentPublication . Nogueira, Joana Garrido; Lopes-Lima, Manuel; Varandas, Simone; Teixeira, Amílcar; Sousa, RonaldoDroughts can change the distribution and alter the behaviour, phenology and physiology of many species, leading in extreme cases to high mortalities or even extirpation. In this study, a before/after comparison was performed in two Portuguese river basins (Rabac¸al and Tuela) to assess the possible effects of an extreme drought on the abundance and size structure of two pearl mussel Margaritifera margaritifera populations, a Critically Endangered species in Europe. The hydrological year of 2017 was extremely dry in Portugal and this situation was responsible for a major reduction of the river flow and rapid decrease in the water levels during summer. One year after the drought, a significant reduction in abundance was observed (i.e. 27.6% for the Rabac¸al and 38.7% for the Tuela basin populations). However, no differences were detected in the size structure of the two pearl mussel populations. Droughts are predicted to increase in number and intensity and it is crucial to monitor M. margaritifera populations, given the low resistance (and possibly low resilience) of this species to these extreme conditions. Management measures that could help the conservation of pearl mussels are discussed.
- A tale of shells and claws: The signal crayfish as a threat to the pearl mussel Margaritifera margaritifera in EuropePublication . Sousa, Ronaldo; Nogueira, Joana Garrido; Ferreira, André; Carvalho, Francisco; Lopes-Lima, Manuel; Varandas, Simone; Teixeira, AmílcarThe freshwater pearl mussel Margaritifera margaritifera is a highly threatened species in Europe. Several mechanisms may be responsible for the decline in distribution and abundance of European pearl mussel populations, but almost no quantitative data exists about the possible negative impacts of invasive alien species (IAS). In this study, we clearly demonstrate that the invasive signal crayfish Pacifastacus leniusculus predates pearl mussels, using a laboratorial experiment followed by in situ validation in four rivers in the North of Portugal (Mente, Rabaçal, Tuela and Baceiro Rivers; Douro Basin). In the laboratory, the crayfish had a clear preference for small-sized pearl mussels but no differences in predation were found in mesocosms with and without sediment. In addition, we clearly demonstrated that the signal crayfish predates pearl mussels in natural conditions and detected a significant density dependent effect (i.e., sites with more crayfish presented higher number of pearl mussel shells with marks of predation). Given the recent introduction of the signal crayfish and the potential negative impacts on pearl mussel populations we also investigated its autoecology (distribution, abundance, size structure and sex-ratio) in the four studied rivers. Significant differences in average abundance and size of the crayfish were detected between sites and the sex-ratio was highly skewed to females. In view of the widespread distribution of signal crayfish (and other invasive crayfish species) in Europe, future management actions devoted to the conservation of pearl mussels should take in consideration the possible negative effects of these predators, especially on juveniles.
- Water mill canals as habitat for Margaritifera margaritifera: Stable refuge or an ecological trap?Publication . Sousa, Ronaldo; Nogueira, Joana Garrido; Lopes-Lima, Manuel; Varandas, Simone; Teixeira, AmílcarAnthropogenic habitats may serve as a refuge for aquatic species, including freshwater mussels (Bivalvia, Unionida). Evaluating the role of anthropogenic habitats is a fundamental, but still ignored, conservation issue given the pace that humans have been converting natural ecosystems. In this study, possible differences in abundance, size and condition index of the freshwater pearl mussel Margaritifera margaritifera colonizing anthropogenic (water mill canals) and natural (Tuela River) habitats were assessed. No differences were found in the abundance of freshwater pearl mussels colonizing both habitats, but individuals present in the water mill canals have a significantly higher condition index and size. Water mill canals seem to provide stable conditions for the settlement, growth and survival of freshwater pearl mussels. However, the occurrence of an exceptional drought during the late summer of 2017 was responsible for an almost 100% mortality in one of the two water mill canals surveyed in this study. Therefore, and during extreme climatic events, these anthropogenic structures may function as an ecological trap for freshwater pearl mussels. This study can be used by managers to promote future actions that enhance freshwater pearl mussel protection and guarantee their survival, including on anthropogenic habitats.
- Ecological status of a Margaritifera margaritifera (Linnaeus, 1758) population at the southern edge of its distribution (River Paiva, Portugal)Publication . Amorim, Ângela; Sobral, Carina; Froufe, Elsa; Varandas, Simone; Teixeira, Amílcar; Lopes-Lima, ManuelAn important population of the critically endangered pearl mussel Margaritifera margaritifera (Linnaeus, 1758) was surveyed at the edge of its southern distribution (River Paiva, Portugal). Although an earlier study suggested that this population had a very low number of individuals (<500), a narrow distribution, and was mainly comprised by old specimens our data contradict these findings. Our assessment estimated a population with probably more than 5,000 individuals distributed across 80 km of the river length. From the 32 sites surveyed, 19 contained M. Margaritifera with higher abundances verified in the middle and upper parts of the river (a maximum of 78 ind. per 100 m of river stretch was recorded). The pearl mussels showed a clear preference for areas near the banks, in shallow water, sandier and gravel sediments, and a high degree of riparian vegetation cover. The population structure was skewed with a very high percentage of large (and old) animals but 3.7 % of the individuals collected were juveniles (\60 mm in length); therefore, this population can be considered functional. Environmental characterization indicated that this river is still in excellent or good condition although some areas showed deterioration due to discharge of domestic effluents. The main conservation requirements of M. margaritifera in the River Paiva include maintaining the water quality (and if possible stopping the discharge of domestic effluents), increasing riparian vegetation cover, removing several weirs to increase connectivity, and increasing trout density.
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