Description: Conserving fluxes of terrestrial invertebrates to streams, which supply about half of the diet of stream fish, is an important goal for aquatic conservation. Riparian land uses such as forestry and grazing could have strong indirect effects on fish, by reducing these prey inputs. A large-scale replicated field experiment was conducted in four western US rangeland catchments to test the effects of three levels of cattle grazing in riparian pastures on vegetation, fluxes of invertebrates, trout diets, and trout abundance and biomass. The treatments mimicked common grazing systems. The grazing treatments reduced riparian vegetation biomass to levels as low as or lower than rotational grazing systems. The most intense treatment also removed two-thirds of riparian shrubs, thereby reducing overhead cover. All grazing treatments reduced the inputs of terrestrial and adult aquatic insects to streams, compared with controls, but only reductions caused by the most intense treatment were statistically significant, owing to the high levels of natural variation among control sites. Significant reductions of invertebrate inputs by this treatment during key seasons confirmed that riparian shrubs are an important component in the supply of invertebrates to streams. All treatments reduced the levels of terrestrial invertebrate prey found in trout diets, by half or more at the end of the experiment. Some reductions appeared to be compensated for by greater foraging of trout on larvae and adults of aquatic invertebrates. Trout did not respond to reduced prey by adjusting their density or biomass, probably because they were in good body condition, prey inputs were the highest yet recorded to rangeland streams, and trout foraged selectively to buffer the loss. Conserving fluxes of terrestrial prey to trout in rangeland streams will require the careful management of cattle grazing, especially to sustain riparian shrubs that are likely to serve as sources and vectors for invertebrate inputs to streams.

Description: Freshwater mussels (Unionoida) are globally threatened. The key to the development of effective conservation strategies for this group is to unravel their complicated life cycle, including the obligatory larva, which parasitizes the external tissues of fish. Artificial infestation was conducted for three fish species – Barbus barbus , Chondrostoma nasus , and Squalius cephalus – in order to study the prevalence, site, and intensity of infestation, in relation to the fish species and their individual body size. Fish gut contents were also examined, in order to analyse the possibility of glochidia consumption. Glochidia of Unio crassus are considered parasites of fish gills; however, this study revealed that U. crassus glochidia were attached to the fins of all the host species tested. The number of glochidia attached to C. nasus fins was four times higher than the number of glochidia attached to gills. The prevalence of fin infestation was higher for C. nasus and S. cephalus than for B. barbus . Infestation intensity was highest for C. nasus and lowest for B. barbus , and was also dependent on fin type. The number of glochidia attached to fins demonstrated a nonlinear (log 10 ) relationship with fish body length. Inspection of dissected fish guts showed that all of the fish species tested foraged on glochidia: S. cephalus and B. barbus more frequently than C. nasus . Using predatory fish host species with non-predatory species in mixed assemblages for artificial rearing of mussels led to increased mortality of fish and decreased infestation intensity. The best conservation practices for freshwater mussels should therefore be based on single fish species that are easy to infest and that do not prey on glochidia.

Description: Temperature has a key impact on the physiology, food acquisition, metabolic rate, growth, and reproduction of organisms. Thus, exploring the effects of climate change on species physiology is important for the conservation and management of native and non-native bivalve species. In this work, an integrative laboratory approach was used to compare the physiological, cellular, and molecular responses of the native Unio delphinus and the invasive non-native Corbicula fluminea under a natural heat-wave event. Whereas the filtration rate in C. fluminea was clearly affected throughout the whole heat-wave event (from the heat peak onwards), it was only significantly affected during the heat-wave climax in U. delphinus , and recovered afterwards. At the cellular level, lysosomal membrane stability was affected during the heat-wave climax, but recovered afterwards, in both native and non-native bivalve species. At the molecular level, hsp70 and hsp90 gene expression were increased and decreased (respectively) in C. fluminea after the heat wave. In contrast, only hsp90 gene expression decreased in U. delphinus during the climax and after the heat wave. The present work demonstrates that accurate monitoring of native and non-native species using an integrated biomarker approach provides new insights into how both species might cope with the expected increase in frequency and intensity of heat events in a global warming context. Direct and indirect impacts of heat waves have been associated with massive mortalities of both native and non-native species. Despite present results showing that C. fluminea are more sensitive to heat waves than U. delphinus , massive mortality events might act in favour of C. fluminea as it has a higher reproductive capacity. Although native freshwater mussel species conservation is already threatened by overexploitation, flow regulation and diversions, habitat destruction, and pollution, it is probably also adversely affected by global warming and the presence of invasive non-native species, such as C. fluminea .

Description: 1. Biogenic reefs formed by bivalves are biodiversity hot spots that provide important ecosystem services, but are globally endangered. In Strangford Lough (Northern Ireland) the use of mobile fishing gear (MFG) has caused extensive damage to reefs formed by the horse mussel ( Modiolus modiolus L.), leading to declines in their extent and condition. 2. Captive breeding and translocation have been proposed as potential restorative strategies for the remaining reefs, and thus the reproductive biology of M. modiolus as the keystone species needs to be described prior to attempting large-scale ecological restoration. 3. Physiological condition and gametogenesis were studied in two sympatric M. modiolus subpopulations using direct gonad assessment methods. The size- and age-frequency structure of the whole metapopulation were described to establish present or past recruitment events. 4. Although gonad condition remained high in each year for the two subpopulations studied, significant losses were recorded in one subpopulation. These observations are consistent with autumn and winter spawning, but were not recorded in reefs thought to be more damaged by MFG. 5. Length- and age-frequency histograms showed a distinct bimodal distribution in all remnant M. modiolus subpopulations, which were dominated by mussels over 50 years old. Little or no successful recruitment has occurred in some subpopulations, where low reproductive output caused by declines in broodstock numbers might be preventing natural recovery. 6. A combined approach of strict protection of the remaining larval sources and active restoration through stock supplementation is recommended to address recruitment limitations and increase connectivity between remnant subpopulations.

Description: Globally, seagrasses and other estuarine habitats are under threat from a range of human disturbances, including boating-related activities. The fixed, block-and-chain swing moorings used to secure boats in many countries can create visible scars in seagrass meadows and remove other benthic organisms. Losses of seagrasses in two estuaries in New South Wales (NSW), Australia, were quantified using aerial imagery and used to estimate estuarine habitat damage across the remainder of the state. The rate of mooring scar development was approximated and factors influencing the size of mooring scars were identified. Individually mapped mooring scars in meadows of the endangered Posidonia australis ranged from 55 to 706 m 2 , and were generally larger than those in the more opportunistic seagrass Zostera muelleri subsp. capricorni (22–342 m 2 ). Scar size in both species of seagrass increased significantly with depth and boat length. The rate of increase in the size of mooring scars amongst P. australis was roughly linear over 4.8 years, averaging 6.3 m 2 /month up to a maximum of 16.7 m 2 /month for one 16-m yacht. Across all of NSW, it was estimated that currently leased moorings were causing losses of 129 884 m 2 of P. australis and 93 940 m 2 of Z. capricorni , and disturbing 2 790 907 m 2 of non-vegetated soft sediments. NSW seagrass loss estimates relate only to damage from current moorings and could be underestimated by ~41% for P. australis if estuaries contain many old scars that remain after the relocation of moorings (as has occurred in Lake Macquarie). Mandating the use of moorings that do not rely on a chain dragging on the sea bed would greatly reduce future physical damage of benthic habitats and enable some recovery from legacy effects.

Description: The Danube streber, Zingel streber , is a threatened and data-deficient percid fish endemic to the Danube catchment. The study provides the first data on distribution, life history, and genetic structure of the species at the upstream limit of its historic distribution (south-western Germany). A 3-year survey effort with 143 fishing events identified several small, fragmentary populations covering only 7% of the historical range of the species. Census population sizes ( N c ) of these subpopulations were estimated from mark–recapture data at 〈200 individuals. Effective population sizes ( N e ), calculated from genetic data (microsatellite genotyping), were much smaller still, at 〈15 individuals, resulting in an N c / N e ratio of 〈0.25, strongly indicating that populations are seriously affected by genetic drift and inbreeding, and are thus facing a severe extinction risk. Life-history parameters recorded during the study indicate a rapid life cycle, with both sexes probably attaining sexual maturity at the age of 1 year or older. Spawning commenced at the beginning of April and fecundity was low (~300–400 eggs per female). Genetic analysis and mark–recapture data indicate that subpopulations of the streber live in effective isolation, separated by impassable weirs that significantly reduce genetic connectivity between subpopulations. The species is rheophilic, and limited to sites with flow velocities of ~0.7 m s –1 . Hydropower infrastructure may thus also have diminished the availability of suitable habitat by reducing flow rates. Only 32% of the historical range of the Danube streber is now estimated to be morphologically suitable for the species. Furthermore, relevant parts of this range are located upstream of dams and are therefore not accessible for natural recolonization. The availability and accessibility of suitable habitats seem to be factors limiting the size of the remaining subpopulations. Conservation actions should address the restoration of degraded river habitats and increase the connectivity between isolated subpopulations of the Danube streber.

Description: Under a warming scenario many permanent inland water bodies in the Mediterranean region have become temporary ones, so the persistence of submerged macrophytes depends on the timely production of drought-resistant propagules. Phenological research measures the timing of ecological processes and allows the consequences of disturbances such as climate change to be evaluated. Among macrophytes, the charophytes are widely distributed benthic macroalgae and are particularly sensitive to environmental variations. The systems in which they live constitute valuable, threatened, and protected habitats (European Habitats Directive code 3140). This study established a methodological basis for determining which environmental drivers trigger the sexual reproductive phenology of charophytes. For the first time, circular statistics were applied to describe and compare seasonal patterns for submerged macrophytes. Over a period of 2 years, three charophyte species growing in two Mediterranean brackish ponds were monitored. Most of the sexual reproduction occurred during spring and summer, including the production of drought-resistant propagules, before the harshest conditions arrived. Each species showed a distinctive phenological pattern, according to specific breeding systems, life cycles, and environmental tolerances and requirements. Deeper conditions and higher salinities delayed reproduction. Different rainfall intensities in autumn produced distinctions between years, as stronger rainfall reduced the salinity stress and stimulated the reproduction of plants. Interacting factors act as cues for charophyte reproduction and cause antagonistic effects on propagule production. Among them, the heat required for each phenophase peak is essential for understanding the phenology of a population and for predicting its long-term persistence. Charophytes appear to be good candidates for tracking climate change in shallow ecosystems. Further phenological studies should consider more species, populations, and long-term observations in order to predict climate-change effects on water bodies, and to develop effective plans for management and conservation. Circular statistics is a potential tool for analysing phenology in the context of global warming, as well as for many other conservation issues.

Description: In South Africa, the humpback dolphin ( Sousa plumbea ) has been recognized as the most endangered marine mammal, with a low abundance, a discontinuous distribution, and numerous threats. This research was initiated in 2008 to estimate the number of individual humpback dolphins in Algoa Bay, as well as studying their residency patterns and distribution. The last boat-based study on humpback dolphins, conducted 24 years ago, formed an important reference against which to compare current findings. This study reveals that since the 1990s the number of identified animals decreased from 70 to 50 individuals, and the mean group size of humpback dolphins has also decreased, from seven to three animals. Humpback dolphin behaviour was predominantly that of foraging and travelling, although the overall frequency of foraging still seems to have decreased since early 1990s. Although the species was seen almost all year round, the number of sightings per survey was lowest in January, March, and April. The number of sightings per kilometre surveyed substantially decreased from 0.018 sightings per kilometre in 2008 to 0.004 in 2011, and the number of animals per kilometre also decreased from 0.042 to 0.009. The re-sighting rates were low, ranging from one to eight times, with 52% of identified dolphins seen only once throughout the study period. Only 6% of the individuals were seen more than three times. Reduced humpback dolphin numbers and sighting rates could be indicative of the rise in anthropogenic activities, such as shipping and recreational boating, as well as a rise in pollution from vessels and urban development. Conservation strategies, such as a Biodiversity Management Plan for the species, are urgently needed in Algoa Bay, especially in the south-west part of the bay, between Cape Recife and the Port Elizabeth Harbour, where the species occurs most frequently.

Description: 1. Despite their importance for aquatic biodiversity, ponds are among the most vulnerable freshwater habitats. Owing to their isolation in terrestrial environments, ponds are expected to be relatively well protected from biological invasions, but this depends on many factors. 2. The purpose of this study was to examine the influence of a range of variables (water quality, habitat, and landscape attributes) on the colonization of discrete ponds by a widespread aquatic invader, the red swamp crayfish Procambarus clarkii , which can disperse overland. 3. Investigations were conducted in two networks of ponds, each located in close proximity to a large invaded marsh. The two marshes under study differed in the length of time since the crayfish were introduced. 4. The proportions of colonized ponds and crayfish abundances were moderate in both networks, but higher in the network that had been invaded first. In both networks the distance to the marsh was the main predictor of pond colonization, considering similar energy costs to cross aquatic and terrestrial habitats for the recently invaded network, but assuming that dispersal was 25 times costlier across the terrestrial matrix than via streams for the earlier invaded network. Pond characteristics had no influence on crayfish occurrence in either network. Furthermore, predictions of pond invasion were lower for the recently invaded network. 5. The importance of the distance to the marsh indicates that natural dispersal was the main process of pond colonization by crayfish. Findings also suggested that overland dispersal was rare and costly. By contrast, streams were probably significant in facilitating crayfish dispersal. Differences between the two networks might arise from an invasion process still in progress in the recently invaded network. 6. From a management viewpoint, local actions are encouraged to prevent the spread of crayfish via streams. In addition, broader-scale actions to mitigate other human disturbances would improve the outlook for pond biodiversity.

Description: Biological invasions are widely regarded as the second major cause of the current global biodiversity crisis. Freshwater environments in particular include many habitats and species of conservation concern. Among those, amphibians are threatened worldwide by habitat loss and by the introduction of alien taxa, including pathogens and fish. The North American mosquitofish Gambusia spp. have been introduced throughout the world for the biological control of mosquitoes, and have established alien populations in over 110 countries. Their impact on native freshwater vertebrates, especially in Europe, is still poorly known. Here, the predatory impact of mosquitofish on the larval stages of four European amphibian species ( Hyla intermedia , Triturus carnifex , Pelophylax kl. hispanicus , and Bufotes balearicus ), locally abundant in Central Italy, has been investigated under laboratory conditions to assess whether any difference occurs in species vulnerability and interactions with the predator, as their breeding sites are often invaded by mosquitofish. Larval mortality and fish attacks, as well as observations on fish predatory behaviour, were recorded at four time intervals (10 min, 1 h, 6 h, and 24 h) and at three different prey abundances (with five, 10, and 20 larvae). A significant difference in predation rate for species, exposure time, and larval abundance occurred, with H. intermedia being the most vulnerable species and B. balearicus being the least vulnerable species. An increase in exposure time increased the rate of predation, whereas small groups of larvae (i.e. 〈10 individuals) appeared to be far more vulnerable to fish attack compared with the larger groups. Mosquitofish show considerable potential to prey upon the larvae of European amphibians, representing a serious threat for their conservation. Appropriate management and legislative strategies are thus necessary to prevent the further introduction and spread of this alien fish in natural environments.