Marine and Freshwater Research

There has been minimal synthesis of the impacts of water-quality degradation from agriculture on freshwater ecosystems in northern Australia. The present study conceptualises the spatial and temporal processes driving water-quality pressures in Australia’s Great Barrier Reef catchment area, with associated ecological impacts. Hydrology mediates the timing and scale of pollutant delivery to freshwater ecosystems, and the risk periods and specific nature of water-quality impacts can differ markedly from those most affecting downstream marine environments.

Environmental (e)DNA sequencing can be used to identify entire biological communities in a rapid and inexpensive way, and has the potential to benefit aquatic biodiversity surveys. The aim of this review is to provide guidance to non-geneticists regarding eDNA sequencing for biological surveys and to outline the requirements that need to be considered before the technique can be incorporated into aquatic biomonitoring programs.

We compared the effects of water allocations, conservation and climate change scenarios on economic returns from irrigation. Land use had the greatest economic returns, but land area suitable for irrigation rather than irrigation water itself was the major limitation. Annexing land for freshwater conservation values had only small effects on economic returns, suggesting that conservation and agricultural development are not necessarily antagonistic goals.

Freshwater sediments harbour minute but diverse microscopic fauna, dominated by rotifers and nematodes. In our research we try to define occurrence and vertical distribution of these organisms in a specific karst sediment – tufa. Deeper parts of sediments are mostly inhabited by surface fauna that is morphologically pre-adapted to life within sediment interstices and this seems to be general rule in freshwater ecosystems.

We surveyed Tibetan streams between 4459 and 5062 m above sea level to obtain data on densities, habitat preferences, feeding selectivity and food web position of the stone loach Triplophysa; some of the world’s highest living and ecologically least studied fish. Densities were highest near lakes (1.6 individuals m^–2) and decreased with altitude and glacial influence. Triplophysa was omnivorous, but was always at the top of the food web.

Using towed imagery in turbid waters enabled a rapid, large-scale survey that observed severe thermal coral bleaching in March 2013 off Onslow, north-western Australia. Despite predominance of bleaching resistant species we found over 50% of all corals bleached in 10–15-m water depth. Recurrent heat stress is assumed to have structured the local coral community, eliminating thermally vulnerable species.

We investigated the potential for zooplankton to emerge following inundation of dry soils on the lower Waikato River floodplain, New Zealand. Our findings indicate that scrub and forested floodplains can be important areas for large-bodied zooplankton production, and that maintaining vegetative heterogeneity on floodplains may promote trophic subsidies for migrating juvenile fish as floodwaters subside.

Relationships between productivity and population biology (abundance, individual size, growth rates, longevity, secondary production and turnover rates) of two intertidal gastropods of different trophic levels, the herbivorous Cerithium atratum and the scavenger Nassarius vibex, in a sandflat environment were investigated. The life-history traits of the gastropod species responded to different trophic levels. Herbivores had higher abundance, growth and production efficiency than did scavengers.

Summary.  American eels commonly occupy bays and estuaries of the southern Gulf of St Lawrence in both summer and winter. Winter use of this region is perplexing because seawater under winter ice is often cold enough to freeze and kill fish. We demonstrate that American eels lack antifreeze proteins, and instead, find thermal protection in mud burrows that are warmer than the overlying water.

Significant regression relationships existed between carbon biomass and cell abundance for phytoplankton based on net samples from the Yellow Sea and the East China Sea. We established carbon biomass : cell abundance relationships for all phytoplankton cells, diatoms, dinoflagellates and each dominant genus. We suggest using these relationships to improve standing stock research in marine ecology.

Status and trends of larval populations of Petromyzon marinus were studied in north-western Spain by annual electrofishing surveys (2007–2011) and data from other European regions were compiled. The largest populations and the main fisheries of this threatened species are located in south-western Europe. Signs of population increases were registered; however, more data are needed to confirm a possible overall recovery.

Human disturbance of the sea–mangrove connection is currently hampering the natural hydrodynamics of both mangroves evaluated in this study (i.e. Conchas and Malanza). This, and the presence of the Mozambique tilapia, as elements of ecological disruption, may act as limiting factors for the potential biodiversity of the systems.

In many coastal areas around the world freshwater inflows are threatened. The San Antonio Bay System (USA) is of particular interest because it is the winter home of the endangered whooping crane. Organisms of higher trophic levels might be deleteriously affected by reduced inflows because our study suggests that shifts in phytoplankton composition and location of productivity maxima will likely result from lower inflows.

Regulated rivers lack large discharge events or floods, which play a critical role in controlling fine sediment deposition and the maintenance of healthy in-channel condition. Five large environmental floods were released into the regulated Snowy River to mitigate fine sediment accumulation within the river channel. This article identifies the effectiveness of multiple intra-annual floods of various magnitudes at mobilising fine sediment within the regulated river channel.

In this study, we investigated spawning responses of Australian grayling to environmental flows over 2 years in three coastal rivers. Spawning activity was highest during within-channel flow pulses, especially during periods of targeted managed flows. Peak spawning occurred in late autumn and was positively related to flow duration. Our study demonstrates the importance of quantifying flow-ecology relationships by targeted monitoring and research in order to develop appropriate flow regimes.

The present study proposes otolith marking as a method to unequivocally detect selected pre-flexion fish larvae in the digestive tracts of their fish predators, even several hours after their ingestion. Mark detection levels were high (>65%) even after 9 h from prey ingestion. This constitutes a single and inexpensive technique that could be applied in both laboratory and field experimental studies of predator–prey interactions.

Management of invasive species largely focuses on early detection and eradication; however, once established, invaders could also be controlled by exploiting local adaptations in native species. The present research demonstrated that dwarf galaxias (Galaxiella pusilla), a threatened Australian freshwater fish, has adaptations to habitat drying that could underpin efforts to control invasive eastern gambusia (Gambusia holbrooki) within critical habitats.

Analysis of COI sequences of the shrimp Caridina cantonensis from streams in Hong Kong showed that populations from different streams are genetically distinct, whereas the genetic diversity within each stream is very low. The results suggested that a substantial amount of biodiversity might have been lost during the development of the city over the past century.

The present study reveals the occurrence of multiple paternity in the bull shark (Carcharhinus leucas) showing high paternal skew. These results tend to support the hypothesis of convenience polyandry. This study contributes to a better understanding of this species reproduction and are important for both shark conservation and management plans.

Organisms such as stingrays may vary their habitat selection based on a variety of environmental factors, and their location can indirectly provide insight into the distribution of both their prey and their predators. The purpose of this study was to determine whether tidal stage and diel period affected the movements of Atlantic stingrays (Dasyatis sabina); and we found that they consistently used tidal currents to access their habitat, but only varied habitat selection with diel period in the winter. These movements may affect the probability of a stingray encountering predators, competitors and prey.

The patterns of distribution and abundance of snapper in South Australia changed throughout the 2000s, subsequently affecting the best approach for managing snapper fisheries. The aim of the present study was to investigate snapper movement behaviour, revealing aspects of its spatial scope, seasonal variation and systematic nature. The findings revealed the complexity of snapper movement, which is beneficial for developing appropriate fishery and spatial ecosystem management approaches.

This study provides important limnological data collected in the semi-arid Eastern Cape Karoo region of South Africa before hydraulic fracturing impacts. It was found that depression wetlands and rivers had distinct physicochemical signatures, whereas dams exhibited variable characteristics that were similar to those of either rivers or depression wetlands. These data are important as baseline for long-term monitoring of freshwater ecosystems in the region.

We investigated the effects of oocyte development, flow magnitude and artificial barriers on migration behaviour in Australian bass (Percalates novemaculeata). Bass spawning migrations occurred only when gonads were mature and on large flows. Connectivity to estuarine spawning habitats was reduced by instream weirs. Our findings are relevant to water resource managers formulating environmental flow rules for regulated river systems.

The recent popularisation of water-based activities is expectedly responsible to increase the odds towards the occurrence of shark bites. Our investigation about the factors underlying shark hazard indicated that shark abundance and shark-bite frequency followed compatible trends off Recife. This study has provided an important insight into the possible biological drivers that regulate the distribution of shark hazard.

The Atlantic needlefish (Strongylura marina) is a coastal epipelagic species inhabiting shallow coastal waters along the western Atlantic coast from Maine to Brazil. We studied the anadromy hypothesis for this species by examining the aggregation of Atlantic needlefish entering and living in Lake Mattamuskeet, the largest natural lake in North Carolina. Although we found no direct evidence of spawning, data compilation suggests that Atlantic needlefish could be using this coastal lake for reproduction.

Elasmobranch species (juveniles and adults) are distributed in medium and high trophic levels, preying on numerous fish and invertebrates. These species had roles as both predator and prey in four trophic levels of the web, participating in most of the identified roles, and are highly redundant in their functions as prey and mesopredators, but not in their role as top predators.

Reproduction is a key biological process that underpins the persistence and maintenance of populations. The present study assessed reproduction in two species of Great Barrier Reef (GBR) sponges: one a brooder and the other a spawner. Temperature was significant in affecting reproduction in these two sponge species. These two species were comparatively more fecund than other sponge species in the region, which may explain their apparent abundance on the GBR.

We have compared dissolved inorganic nitrogen (DIN) release from sediments of rivers and estuaries located at two different hydrologic flow regimes. The DIN releases in the sediment slurry were measured for 48 h at variable salinities, and with constant agitation. Hydrologic forcing on organic matter deposition and salinities had an important role in the sediment slurry release of inorganic nitrogen.

Key stream fauna in Kakadu National Park face severe threats in 100+ years associated with climate change, invasive species, and mine-site rehabilitation. Sea level rise will salt the coastal floodplains and the fauna must then rely on reduced upstream refuges vulnerable to strong swings between more intense El Niños and La Niñas. Rates and extremes of future climate change appear unprecedented, making predictions associated with past climate change unreliable.

Migration is a fundamental aspect of the life history of many fish. This study used acoustic telemetry and analysis of strontium isotopes in otoliths (fish ear stones) to study intraspecific variation in the migrations of barramundi in the Northern Territory, Australia. A revised life history model identifying three migratory contingents is presented to support future management of the species.

Carp gudgeons are the focus of a theory to explain their biodiversity and life histories, based on developmental plasticity. However, basic data relating to their species boundaries, phylogenetic relationships, life histories and species distributions are not yet clear, have often been misinterpreted and are still in the process of being assembled, making it premature to apply more advanced evolutionary theories to this group.

High-latitude regions are likely to be sensitive to ocean warming, and anemonefishes and their host sea anemones may be a useful indicator group for identifying associated changes. We found that the southern range limits and overwintering of these iconic inhabitants are changing along the eastern coast of Australia. However, the paucity of islands and rocky islets south of our surveys, and host-usage patterns, could constrain future range extensions.

Lake MacLeod contains permanently inundated ponds, despite its arid location, because of a subterranean marine link. The present study investigated the effect of biogenic and terrigenous inputs on the physical, sediment and chemical characteristics of these ponds, where the smaller ponds were found to have a persistent marine signature because of their size and faster flushing times. These results have shown that, under certain circumstances, a ‘marine-like’ state can override the typical characteristics of inland water bodies.

Summary. Ecosystem modelling has predicted that fishing for western rock lobster in deep water (50–80 m) habitats results in greater production of small-bodied invertivore fish species. To investigate this prediction, a targeted fisheries closure was proposed along the coast of Western Australia. We demonstrate that any changes in fish species are most likely to be detected in the western king wrasse (Coris auricularis), which was found to be abundant across all habitats and sites.

On the Kakadu floodplains, the distribution of different plant communities varies yearly, related to flooding duration and water depth. Because these floodplains are close to the coast, they are vulnerable to saltwater intrusion as the sea levels rise. The most obvious effect of this will be the transformation from freshwater vegetation to salt-tolerant plants in susceptible areas.

This study assessed the efficiency of a national acoustic telemetry network to detect passing animals. The aim was to determine how many receivers could be decommissioned from each of the eight curtains while maintaining its integrity. Applying predefined criteria, we were able to improve the network significantly, reducing the number of stations by 36%, yet still retaining 84% of total detections, 86% of transmitters and 100% of detected species. This study provides a useful framework for refining acoustic telemetry networks.

Risk analyses and management techniques are presented for the establishment and effects of two invasive species, smallmouth bass and chain pickerel. With their encroachment on the boundary of Kejimkujik National Park and National Historic Site, there is concern about potential ecological effects. Similar challenges for assessment and mitigation exist elsewhere, and our methods may prove illustrative for researchers and managers working under similar conditions.

Movement and dietary patterns of two co-occurring predatory reef fish were examined at Orpheus Island, Australia, respectively using acoustic telemetry and stable isotopes. The findings show low spatial overlap, but high dietary overlap between Plectropomus leopardus and P. maculatus, which may be a product of competition for resources. This research provides new species-specific information about resource use within a genus commonly reported as a single entity.

Stereo baited remote underwater video systems (stereo-BRUVs) were used in this study to investigate the occurrence and size of white sharks (Carcharodon carcharias) in the near-shore environment off Bennett’s Beach, in central New South Wales, Australia. Stereo-BRUVs successfully recorded 34 separate sightings of 22 individual white sharks. This study demonstrates that stereo-BRUVs are a viable, non-destructive method to obtain estimates of the size and presence of white sharks.

In this study we investigated how diet composition and intestinal length of the generalist and omnivorous characid fish Bryconamericus iheringii respond to riparian degradation in Brazilian subtropical streams. Open canopies were related to longer intestines and to decreased ingestion of terrestrial plants and invertebrates, concomitant with increased ingestion of filamentous algae, macrophytes and detritus. Riparian degradation may trigger increased intestinal length of generalist fish populations by driving higher relative consumption of indigestible and low-protein food resources.

Range-wide marked declines in population over the past two decades has necessitated a clear strategy for conserving Indus dolphins. Thus, the present study reports a species tolerance threshold towards anthropogenic disturbances and suggests management interventions to conserve the identified havens of dolphins. Ecological constraint of Indus dolphins is considered to be linked to rich biodiversity, therefore assessing the anthropogenic pressure on dolphins may be a surrogate for other threatened components of sympatric freshwater biodiversity.

Shallow reef-area fish communities of Fernando de Noronha archipelago (north-eastern Brazil) with different levels of environmental protection (no-take MPA and MPA) were compared. Differences in benthic composition, abiotic data and fish-community structure were observed in the comparison between no-take MPA and MPA. A higher diversity, richness, biomass and density of larger fishes were observed for the no-take MPA.

To help juvenile shortfin eels negotiate instream obstacles (e.g. dams), more information is required on ramp angle and what material to line fish ramps with. We found that climbing success decreased with steeper ramps and that climbing success differed between material types. Optimal juvenile shortfin eel ramps would be lined with Miradrain (plastic drainage product) and be set at an angle close to 30°.

The aim of the present study was to test the hypothesis that food chain length (FCL) in floodplain systems depends on the planktonic or benthic reliance of predators. Stable isotope analysis was used in eight waterbodies of the Middle Paraná River. The results supported the hypothesis because the planktonic reliance of predators and the relative availability of planktonic resources were correlated with FCL.

This laboratory study identified body size at sexual maturity, across the Hawaiian Archipelago, for two species of deep-reef snappers, fish of great economic importance across the Indo-Pacific region. Females of both species matured at similar body length, but were ~5 cm smaller in the waters of the fished main v. unfished north-western Hawaiian Islands. Such information helps fisheries managers better specify minimum size regulations.

Litterfall and leaf decomposition represent important functional processes in small streams. We investigated how monthly variation in litterfall influences the aquatic community associated with the decomposition of leaf mixtures during 1 year in a tropical stream. We found that litterfall decreased in the period of higher rainfall intensity, and that the litter-breakdown rate was considerably higher in the warmest months.

This review of the status of the little curlew draws attention to the challenges faced by migratory shorebirds using grasslands and inland freshwater wetlands along the East Asian–Australasian Flyway (EAAF). Knowledge gaps about the physiology and functional ecology of different species and a lack of survey data from inland wetlands along the EAAF limit our ability to assess the status and population trends of most species.

Coconut crabs Birgus latro on Christmas Island in the Indian Ocean may be the only population of this declining species not threatened by overharvesting. To assess the population’s diversity and identify the number of conservation units, we conducted a combined morphometric and population genetic analysis. The findings suggest that the population is genetically diverse and panmictic, and may therefore be considered as a single conservation management unit.

In the Australian subtropics, seasonal changes to flow regimens can affect the conditions of freshwaters and their biological communities. In the ephemeral streams of central Queensland, the macroinvertebrate communities did not change in response to changing flow. Mostly tolerant taxa were found, with sensitive taxa most abundant during high-flow periods. This study provides novel information on the flow-linked succession of macroinvertebrate communities and is important for developing environmental management tools.

The coffin ray is an electric ray endemic to Australia. The combination of the species’ teleost fish diet coupled with its poor swimming ability, very small teeth supported on slender jaws and its large electric organs strongly suggests that this ray uses powerful electric discharges to stun or kill prey before engulfing them whole.

The movements of Port Jackson sharks captured in Jervis Bay on the NSW south coast were tracked, finding that sharks migrate thousands of kilometres each year to their feeding sites in Bass Strait. Males and females return to the same breeding reef each year. Males migrate more quickly than females and the trip south is faster than the trip north.

The purpose of the present study was to validate vertebral band-deposition rates of blue sharks tagged and recaptured in the eastern Pacific Ocean by using oxytetracycline (OTC). Results from band counts distal to the OTC mark on each vertebra indicated that a single band pair (one translucent and one opaque) is formed per year for blue sharks ranging from 1 to 8 years of age.

This research covers aspects of rockpool fish in the Amazonian estuary, assessing how the distribution and occupation patterns are affected by abiotic characteristics. The results show that species occurrence and abundance respond to local environmental and spatial variations, highlighting the role of extreme dynamics conditions in governing this ecosystem.

An understanding of processes such as diel vertical migration of fish at reservoirs, and the major factors driving it, is needed to provide information for the implementation of management and mitigation measures for the effects of hydroelectric plants. Using hydroacoustics, this study evaluated the occurrence and some characteristics of this process in a Neotropical reservoir.

This study revealed that deadly ‘stinger’ jellyfish (Chironex fleckeri) have localised populations separated by tens to hundreds of kilometres. This was demonstrated by examining the chemistry of their tiny bony structures, called statoliths. Unique location-dependent chemical ‘fingerprints’ represent the whole life of the jellyfish from the time they metamorphose from benthic polyps.

The Indonesian archipelago hosts a significant proportion of the biodiversity on Earth, but several species groups, such as freshwater fish, remain poorly described. In this study we characterised larval and juvenile fish biodiversity, as well as spatial and temporal variability, in a pristine peat swamp environment of the River Kumbe in West New Guinea, Indonesia, based on mitochondrial DNA sequence analysis.

Freshwater prawns and fishes coexist in environments of Paraná. The interaction between species of prawns and fishes during ‘La Niña’ phenomenon was studied. Population densities varied in both prawns and fishes. These changes have not been simultaneous. These variations might be associated with predation, aggressive behaviour and micro-migrations. La Niña effect creates additional stress when water inflow is delayed.

Monitoring size can provide an alternative to monitoring population abundance when assessing fishing impacts. In the present study, temporal patterns in the mean size of the four main commercial shark species of Western Australia were evaluated. Unlike commonly reported for other shark populations, the mean size of these species showed fairly stable patterns or slight increases.

Rabbitfish are an esteemed food resource in the Mariana Islands and their seasonal recruitment events represent culturally important harvest periods. In the present study we used a 2-year market sampling strategy to determine life-history traits of the forktail rabbitfish in Saipan, including lifespan, growth and reproduction. Results suggest the species has a rapid life history and considerable variability in reproductive output from year to year, which may help explain yearly variability in recruitment.

Sea-level rise associated with global warming will increase across Kakadu causing widespread saltwater intrusion. We aimed to understand how soil bacteria might respond to these impacts, by sampling transects in different river zones. We found diverse bacterial communities that were sensitive to soil variables, suggesting that saltwater intrusion may affect bacterial contributions to the dynamic floodplain ecosystems of Kakadu.

Experiments were conducted to evaluate the effects of the N : P ratio, as well as the effects of the interaction between the N : P ratio and zooplankton, on phytoplankton. We found that the typical zooplankton of tropical reservoirs may interfere with phytoplankton responses to the effects of nutrients. The zooplankton can also stimulate the growth of ‘less palatable’ algae.

In tropical and subtropical ecosystems with high diversity and low amounts of nutrients, benthic-feeding stingrays and eagle rays partition their trophic resources, resulting in high ecological singularity. However, it is unknown whether this is true for temperate low-diversity nutrient-rich ecosystems. In the present study we compared the diet of three temperate co-occurring species. The three species had a markedly different diet composition, indicative of high ecological singularity.

A research study by Sunfish Queensland, a peak body for recreational fishing in Queensland, shows a major decline in the population and fishery for luderick (blackfish), an important species in coastal fisheries in eastern Australia. Southern Queensland is the northern range limit of this species, and the population decline in this region is significantly correlated with increasing coastal water temperature over the period 1976–2015. The increasing water temperature over the past two decades has caused a southward shift in the luderick population.

The temporal patterns of six biotic groups (from phytoplankton to amphibians) and their responses to environmental variation were studied in a set of Mediterranean temporary ponds. Different temporal patterns were observed among the biotic groups studied, and in some (but not all) cases these differences were explained by their dispersal ability. Similarly, we observed that environmental control was group specific.

Floodgates that restrict tidal flow can reduce the diversity and abundance of fish and crustaceans (e.g. prawns) in coastal wetlands. This study illustrates that these impacts can be overcome by opening floodgates to restore tidal flushing and reinstating biotic passage and the habitat conditions (e.g. pH, salinity) most suitable for the juveniles of estuarine and marine dwelling species. This has implications for improving the nursery value of estuaries to support fisheries productivity.

Trophic interactions between two different filter-feeding communities in subtropical shallow lakes were investigated experimentally. Bivalves consumed small-sized zooplankton, but no consumption of medium-sized individuals was registered, favouring an average larger-sized community. Bivalves consumption of phytoplankton was higher than that of zooplankton and bivalves were also able to reduce cyanobacteria. Together, the results suggest that the introduction of bivalves can have positive effects in eutrophic systems mitigating the excessive growth of phytoplankton.

We studied the distribution and abundance of the invasive signal crayfish in northern Spain and analysed the relationships with several abiotic and biotic parameters of the aquatic ecosystems. Our analysis indicated that the habitat of signal crayfish is among salmonid (headwaters) and cyprinid (low waters) stretches. The existence of a natural environmental limiting factor in upstream reaches facilitates the conservation of aquatic ecosystems and native fauna.

The approach used in this study indicated a match between fishers’ and scientific histories with regard to the richness and composition of catches, as well as relative trends in abundance. Histories diverge when fishers were asked to recall their largest catch and the largest fish caught. This study provides a roadmap of what information can and cannot be considered reliable when recalled by fishers.

We examined fish recruitment patterns in 10 permanent lagoons on the Tully–Murray floodplain in the Queensland Wet Tropics bioregion, Australia. Lagoon connectivity to the rivers, distance from the coast and flood dynamics influenced temporal variation in fish abundance, population size structures and recruitment patterns. Maintenance of natural seasonal patterns of flow and connectivity, and active protection of permanent floodplain lagoons from riparian and land-use disturbance, will be essential if their roles in fish recruitment are to be sustained.

Dormant stages of aquatic invertebrates are vital to identify the resilience of communities in ponds invaded by exotic pine species. Pine invasion decreased the richness and affected the composition and β diversity of drought-resistant aquatic invertebrates in ponds in southern Brazil. Effectively dealing with invasive pine should become a priority for wetland conservation.

This research has used a mechanistic approach combining field, laboratory and modelling components to determine the importance of hydrological connectivity in the early life history of the freshwater shrimp (Macrobrachium spinipes) in northern Australia. It has confirmed that larvae are produced over 400 km from the estuary and despite this, the species is obligate amphidromous and larvae must travel this distance within 7 days of hatching. Large flood events were critical in connecting these upstream habitats to the estuary.

The reef manta ray, one of the largest fishes in the world, is known as a filter-feeding planktivore, although its diet is basically unknown. By looking at stomach contents, we show that large copepods dominate the diet. The results may indicate limitations of the filter mechanism or may mean that the manta ray preferentially targeted large copepod prey.

Intermittently open estuaries are important fish nursery habitats and are common along microtidal coasts. The present study demonstrated that fish assemblages in these estuaries can be used as indicators of estuary condition, and that estuarine resident species are particularly tolerant to contamination and poor water quality. These findings suggest that anthropogenic activity has a negative effect on estuarine biodiversity and highlights the importance of improving management strategies and environmental monitoring of these key habitats.

The aim was to clarify different aspects of the population structure of Genidens barbus, such as connectivity among nursery areas and homing behaviour. For this purpose, otolith-core chemical signatures were compared among different estuaries from south-western Atlantic Ocean. These results suggested that a high level of spatial segregation exists in adult catfish life, and that catfish tend not to mix among estuaries, supporting the homing hypothesis.

In this study we used two dimensional acoustic telemetry to evaluate a floating fish guidance structure designed to deter imperilled juvenile salmonids from a high mortality emigration route in the Sacramento–San Joaquin River Delta. Results suggested that the structure was successful at guiding fish away from the high mortality route under certain conditions.

The coastal floodplains of the Kakadu Region of northern Australia are highly vulnerable to future sea level rise (SLR) and extreme weather events. A hydrodynamic model was developed to simulate the frequency and extent of saltwater inundation of future SLR scenarios from 2013 to 2100 (1.1 m above mean sea level), and was used to assess potential risk to freshwater floodplains.

Saltwater crocodiles (Crocodylus porosus) have strong cultural value in Timor-Leste, yet attacks on people show the highest fatality rate of any country within the crocodile’s range (82.2%). Attack statistics are made worse by poor food security, and the demographic at highest risk is male teenagers involved in subsistence fishing. Developing a management plan is strongly recommended to reduce attacks without affecting wild crocodile populations.

In situ organisms as bioindicators are essential in assessing the effects of contamination on the environment. The present study, on the intertidal gastropod Bembicium nanum, demonstrated a link between the accumulation of metals at a contaminated site and reduced health of the organisms, measured by increased lysosomal destabilisation. These results show that B. nanum has potential for use as a bioindicator of metal contamination.

The dietary composition (including temporal and spatial variations) of the seahorse Hippocampus guttulatus from the north-western Iberian Peninsula was assessed using Bayesian stable isotope mixing models and revealed that Caprellidea were the primary source, followed by Gammaridea and Caridea. Mysidae and Annelida represented the less dominant prey. These findings improve knowledge of feeding patterns of this endangered species, providing relevant data for its conservation management.

The Maugean skate is a listed threatened species restricted to two estuaries in Tasmania, Australia. The present study provides preliminary knowledge of life history traits essential for conservation management of this species, including movement patterns, population status, habitat use, diet, size structure and reproduction. Survival of this unique species depends on appropriate management of human impacts and environmental pressures within Macquarie Harbour, the sole stronghold of this species.

Few studies have been performed in fragment (continental) islands compared with Darwinian (oceanic) islands, probably due to the expected similarity between the fragment island and landmass. However, fragment islands can develop their own assemblages through biological and biogeographical processes, and thus differentiate themselves from their continental sources, becoming important contributors to global biodiversity.

We investigated spatial variation of benthic diatom assemblages in reasonably undisturbed subtropical streams. The results demonstrated that diatom growth form, cell size and attachment mode can be used to create a more quantitative and predictive approach to establishing relationships between diatoms and environmental gradients. This study is a stepping stone towards further understanding of diatom ecology and the development of a diatom biological monitoring protocol that is suitable for subtropical regions.

In this paper, we tested the influence of species–area relationship and species–energy association on taxonomic richness and functional richness of fish assemblages of tropical streams. Using data of two distinct basins, we demonstrated that the influence of area and energy varies for each basin, a possible response to local conditions of the environment.

The present study describes the river microbial communities upstream and 3.3 km downstream of a small rural town. We report three patterns in microbial community composition, namely, persistence, loss and appearance. Sample dissimilarity, present as microscale hotspots of discrete species, indicated higher heterogeneity downstream, and therefore increased patchiness from downstream transport and inputs of bacterial species. These findings suggest three fates for bacterial species of fluvial systems, namely, persistence, loss and appearance, with each having different effects on system dynamics.

The mitochondrial DNA marker was employed to analyse phylogeographical patterns of 10 populations of K. punctatus. The results showed that the climate of Pleistocene periods had played an important role in phylogeographical patterns of K. punctatus and the dispersal strategy of coastal species may be the major current physical barrier for the gene flow among populations from Chinese and Japanese coastal waters.

Estuarine invertebrates may consume carbon originating from a variety of sources, including mangroves, seagrass, microphytobenthos and phytoplankton. Using stable isotope analyses, we found that the relative importance of carbon sources to a polychaete varied with latitude along the east Australian coast, following spatial variation in the nitrogen content of seagrass. Latitude may influence carbon sources of consumers by modifying producer traits.

We examine the impacts of consecutive bleaching events in 2002 and 2003 on coral susceptibility across various habitats and depths at Moorea, French Polynesia. Bleaching effects were genus specific and highly variable at small spatial scales. This variability has important implications for assessing changes to coral community structure over time and for estimating coral-reef resistance and resilience to future bleaching disturbance.

The invasive apple snail Pomacea canaliculata feeds primarily on aquatic plants, but some anecdotal reports indicate that it also consumes carrion. Herein, we studied carrion ingestion and its effects on growth, concluding that carrion may be important as an alternative resource when aquatic plants are absent. This feeding flexibility helps explain the potential of P. canaliculata to establish in new wetlands and, paradoxically, its persistent effects on aquatic vegetation.

Ephemeral rivers in northern Australia break up into a series of waterholes during the dry season, within which fish have to survive. This depends on the waterholes lasting throughout the dry season and with temperatures that are not lethal. Using comprehensive waterhole temperature data, we found that fish could survive in waterholes that remained deeper than 0.5 m, especially if they were turbid.

The cyanobacterium Aphanizomenon favaloroi was identified for the first time in Europe in the Mediterranean brackish Lake Vistonis during July–August 2014. During its occurrence, the cyanotoxins saxitoxin and neo-saxitoxin were detected in the lake, coinciding with a massive fish kill. This saxitoxin-producing species may pose a health risk to animals and humans and have adverse effects on water quality.

Dams, weirs and other barriers disrupt river connectivity and degrade fish communities worldwide. Fishways are in place at few sites relative to the numbers of barriers, and very few effectively mitigate barrier effects. Herein we review migratory behaviour among Australian fish and the effects of fish passage barriers. Australia’s highly variable hydrology challenges mitigation programs; options include basin-scale approaches; improved management of barriers, environmental flows and water quality; barrier removal; and development of improved fishway designs.

In aquatic systems, odour cues can be used to quickly identify predation risk. Here, we show temperate marine and tropical freshwater shrimp avoid predator odours but not those of non-predators or conspecifics. Cues also alter habitat selection, with structurally complex habitats favoured when predator odour is present. Rapidly altering behaviour in response to perceived risk could reduce predation while increasing time available for tasks such as foraging.

Juvenile penaeid prawns were sampled from temperate intertidal marsh and subtidal creeks. Very few prawns were sampled within the intertidal marsh, suggesting these habitats may generally not be directly utilised by juvenile penaeids in temperate Australia. Larger school prawns (M. macleayi) sampled from the middle of subtidal creeks compared to edge habitat. Although juvenile penaeids may not directly utilise intertidal marshes, they may still export important resources for prawns in subtidal creeks.

Incorporating species trait information may provide insight into complex trophic interactions. In this study, we evaluated the effect of the common carp, Cyprinus carpio, on aquatic ecosystems, focusing particularly on middle-out-mediated effects. Common carp foraging activities and abiotic effects caused a shift in ecosystem structure and function. Specific autecology information will be critical for understanding the effects of ecosystem engineers and invasive species.

Multi-generational exposure of oysters Saccostrea glomerata to acid sulfate soil runoff altered predator–prey interactions between the oysters and mud crabs Scylla serrata. Mud crab predation was greater on oysters from reference sites than affected sites, and the time mud crabs spent foraging was positively correlated with oyster mortality, providing a potential mechanism for observed trends in oyster mortality.

The present study provided evidence of interannual changes in the M. schmitti reproductive aggregation patterns in coastal waters of the south-western Atlantic Ocean, associated with different bottom-temperature regimens, depending on depth. The M. schmitti reproductive aggregations, observed during spring, were associated with temperatures above 16–17°C, which occurred mainly in shallow waters. The results suggested that changes in depth-dependent bottom-temperature patterns may be important drivers of the reproductive dynamics of this species.

Rivers often span administrative boundaries, and their condition may be best protected and managed under national policies, supported by coordinated national bioassessment. To improve bioassessment practice in Australia we recommend: (1) convene a summit of policy makers and key scientists; (2) develop strategies and priorities to protect rivers and meet emerging challenges; (3) identify key biological indicators; (4) establish measures of success; and (5) develop plans for both ‘bottom-up’ community-driven bioassessment and ‘top-down’ government-led programs.

Teleost spatiotemporal distributions and key abiotic associations were quantified throughout an important estuary within Brazil’s Atlantic Forest biosphere. As in other subtropical estuaries around the world, assemblages mostly comprised juveniles. Five species dominated samples, and their distributions were either negatively affected by salinity or positively affected by temperature or depth. These patterns were attributed to species-specific life stage requirements, and ultimately support clear conservation strategies.

The importance of submerged aquatic vegetation (SAV) beds, dominated by seagrass, as a habitat for shrimp in relation to their distance to a tidal inlet was evaluated in a subtropical coastal lagoon (Laguna Madre of Tamaulipas, Mexico). The SAV bed located 1 km from the inlet had consistently higher shrimp abundance during the day and night, whereas the distant SAV bed (25 km from the inlet) was apparently limited by recruitment, resulting in low shrimp densities.

The choice of survey method can influence both the effectiveness and efficiency of monitoring programs. The present paper compares six commonly employed survey methods for six species of frogs and their tadpoles. Each survey method differed with respect to the probability of detection and the number of surveys required to determine the species.

The dusky spinefoot (Siganus luridus) entered the Mediterranean through the Suez Canal, conquering the eastern sectors of the basin, with marked effects on both natural habitats and native communities. In this study we monitored a recent population of this tropical invader, which settled around the island of Linosa in 2003. The results show how the invasion had expanded to the west, with increasing abundance at the invasion front.

The study used cameras dropped from boats to examine fish populations in and around a small marine reserve in Tasmania, to assess their potential as a monitoring tool. The study found that fish populations differed depending on location, depth and bait, with fish abundance increasing significantly with depth. The research validated the use of underwater cameras for monitoring deep reefs.

Deep pools of intermittent rivers in semi-arid regions provide refuge for aquatic biota during no flow periods. Pool depth is critical because it controls how long pools persist between flows. This study examines sedimentation rates in deep pools of intermittent rivers in eastern Australia to determine if rates have increased since European settlement and if depth reductions arising from higher rates reduce pool persistence times. Results show sedimentation has increased substantially and reduced persistence times by several months.

Data from the Murray–Darling Basin Authority’s Sustainable Rivers Audit were used to classify the Murray–Darling Basin into nine regions with similar historical fish assemblages. We demonstrate how a regionalisation framework can be useful for characterising fish communities and providing a baseline for assessing change in species assemblages.

Stable isotopes were used to investigate the role of submerged aquatic plants (macrophytes) in agricultural stream food webs. Macrophytes made moderate contribution to food webs, but the contribution of macrophytes and their epiphytes was higher where riparian zones were degraded. Many macroinvertebrates were generalist feeders, so these resources may compensate for lost riparian vegetation food inputs in degraded streams.

In Mediterranean shallow lakes, there is a primary effect of external nutrient loads and temperature on eutrophication. However, in these lakes, both senescence and the removal of aquatic plants strongly affects nutrient dynamics, and the amount of the external nutrient load determines the recovery of the lake once nutrient discharges cease.

Spatial and temporal patterns of meiofaunal diversity in a Neotropical lotic ecosystem were investigated. Local and among-areas scales were the highest contributors to overall richness, suggesting local species aggregation and environmental variability as drivers of meiofauna diversity. Temporal diversity was aggregated primarily at the monthly scale. The differences among areas contributed to changes in community composition. Degradation levels and precipitation affected meiofaunal abundance and structure.

Acoustic methods were used to investigate diel and seasonal fish distributions and biomass in a shallow Tunisian reservoir. Gas bubbles confounded spring and summer surveys; bubbles were rare and fish were distributed in open water at night during autumn and winter. Introduced carp, not targeted by fishers, were predominant. Advice on controlling carp to promote a desired fishery is offered.

This study shows that small changes in riparian forest complexity affect the composition of Ephemeroptera, Plecoptera and Trichoptera insects across a small environmental gradient in subtropical streams. The genera Kempnyia (Plecoptera) and Zelusia (Ephemeroptera) were indicative of streams with greater forest complexity, whereas Farrodes (Ephemeroptera) was significant in streams of intermediate riparian forest complexity.

We tested the separate and combined effects of altered flow and fines on macroinvertebrates. Sedimentation and decreased flows individually decreased density and richness of macroinvertebrates and altered assemblage and trait structure. Higher flows did not ameliorate any effects of sedimentation. Further research is required to find the lowest thresholds of sedimentation that have ecological impacts and determine the flows required to ameliorate those impacts.

Food web studies help us understand how ecosystems work. In wetlands of the Kimberley region of north-west Australia we found that microscopic algae is a major source of food for aquatic animals. Groundwater inputs to some waterholes were enough to allow waterholes to persist throughout the dry season. Using groundwater for development may affect the ecological and cultural value of freshwater wetlands through reducing permanence and altering foodwebs.

The present study describes the food web and trophic relationships of a macroinvertebrate assemblage of a permanent Mediterranean river during the four seasons of the year. Moreover, a quantitative approach to estimate the link strength was developed and applied. Finally, relationships between diversity (biological and functional) and food-web complexity are then analysed with the distribution of strong and weak links, and their permanence over time, identified.

We interviewed local fishermen and conducted a fishing survey, so as to assess presence and abundance of bull sharks in the Navua River in Fiji. Both the interviews and the fishing survey confirmed the presence of young sharks. Our findings provide a preliminary characterisation of a potential shark parturition or nursery area from a data-poor region.

Two types of tags were evaluated in the holothuroid Holothuria grisea: an external T-bar and a passive integrated transponder (PIT) tag. Neither the T-bar nor the PIT tags fulfilled the requirements of high retention required for long-term studies. However, we do recommend the use of T-bars for short-term studies for H. grisea under low complexity conditions.

The present study demonstrated that fish abundance was up to threefold higher and species richness twofold higher on artificial structures compared with the natural habitat on a tropical estuary. In addition, fish trophic structure from an adjacent coral reef area showed more than 60% similarity with the fish community on the artificial structures surveyed.

In this paper we propose eight principles that form a heuristic framework to navigate the interface between river science and river policy. These principles were qualitatively evaluated against the objectives of the Australian Water Act 2007 and specifically, the draft Murray–Darling Basin Plan; a component of the Act. We examine whether the eight principles of river science could be recognised in the design of the Water Act 2007 and the draft Basin Plan.

Rhodolith beds are major marine benthic algal communities, comparable in size and significance to kelp beds, seagrass meadows and coralline reefs. Our study indicated that rhodoliths (free-living coralline red algae) are common throughout 70% of Australia’s coastline, forming a vast natural resource in terms of area covered, biodiversity and carbonate production.

The present research has demonstrated how population structure differs in elasmobranchs with different patterns of habitat use. The dwarf and green sawfishes, which spend their entire life in marine waters, were found to have restricted gene flow in Australian waters. In contrast, the largetooth sawfish, which uses freshwater rivers as juveniles and marine waters as adults, was found to have male-biased dispersal in these waters.

The present study provides the first length-at-age, growth and maturity estimates for the bronze whaler (Carcharhinus brachyurus) from Australian waters. Growth-model parameters combined with reproductive information identified C. brachyurus to be long-lived, slow growing and late maturing. These life-history characteristics highlight the potential vulnerability of C. brachyurus to anthropogenic impacts.

The zooplankton of lakes can consume basal carbon sources originated in aquatic and terrestrial habitats and, it plays an important link between these sources and organisms in higher trophic levels such as fish. Using stable isotopes analyses, we showed that in a productive tropical lake, the reliance of mesozooplankton on basal carbon sources seems to follow the seasonal dynamics of in-lake primary production (algae) and terrestrial carbon (plant) inputs.

Extremely low zinc concentrations have been raising the possibility of a potential limitation for growth and distribution of marine phytoplankton. Representatives of two phytoplankton taxa (a pennate diatom and coccolithophorid) were found to adapt and grow at the extremely low zinc concentrations typical of pelagic Tasman Sea. Modification of cell physiology is suggested to be the common adaptive mechanism, although performed differently by each.

We surveyed fish larvae in a semi-isolated mangrove lagoon and tested three different catch methods: minnow traps, light traps, and plankton tow nets. Overall, parrotfish and snapper were the most common larvae from coral-reef fish families, and anchovies were the most common lagoon habitat specialists. Although light traps were the most successful method, they were not as effective in turbid water.

This is the first instance of applying two independent techniques in tandem to validate age-reader interpretations of a New Zealand fish species. From zone counts on otoliths (ear-bones), black cardinalfish had been estimated to live longer than 100 years. The age-validation procedures that confirmed the longevity were lead–radium disequilibria, which uses the natural decay of radium-226 into lead-210 as a natural clock, and bomb radiocarbon (Δ¹⁴C) dating, which relies on the marine signal created by nuclear testing.

Current inadequacies in quality control throughout environmental DNA (eDNA) surveys create the potential for method error to produce false negative detections. We show how a secondary, generic primer, designed to co-amplify endogenous DNA sampled during species-specific eDNA surveys, can be used to monitor method success throughout all stages of eDNA analysis. This positive control enables the distinction of method error from informative non-amplification results, improving reliability in eDNA surveys.

Following associations are composed of nuclear species that disturb the substratum when foraging, and followers that capitalise on food resources. We compared following associations between a marine reef and a freshwater stream. Associations in the freshwater resembled three iconic reef interactions. These similarities between the systems outnumbered the differences, probably because of the shared water environment and the simple requirements for this association.

Lycengraulis grossidens originated from freshwater lineages and is currently distributed in estuaries and coastal zones. Nevertheless, based on otolith chemistry, there are landlocked individuals in the Uruguay River. The present study investigated the spatiotemporal scenario by which these landlocked individuals reached their current distribution: whether through a north-to-south continental route based on the connection between basins or from the marine environment and showed a phylogenetic history and biogeography consistent with a north-to-south continental colonisation route.

The Pacific oyster is a widely spread invasive species globally, with a great influence on native biodiversity and ecosystem functioning. How future climate will influence further spread and establishment of the species in the outer range of its present distribution is important knowledge to assess future risks and to plan mitigation actions. The present paper explores how future climate will affect the species spreading potential at its northern distribution limit in a temperate ecoregion, by three-dimensional oceanographic simulations using different climate scenarios.

Some fish species that are protected from fishing in no-take marine protected areas (MPAs) are important in improving the health of the coral reef itself. We show that it is important to determine how the abundance of these species changes over time and at different places so that we might be able to better place MPAs and better predict how the MPAs might function.

Fish assemblages of the Middle Paraná River floodplain were studied in the light of water variation. Several increases in water level and three flood pulses occurred during the period of study. Fish assemblage similarity was low between habitats during flood and flow pulses. Apparently, flow pulses would also function like floods, namely as mechanisms of spatio-temporal structuring of fish assemblages.

This study used a creative mesocosm-approach to explore the effects of water reduction on abiotic and biotic components of streams, primarily on the macroinvertebrate community. The study was performed in two lowland streams with contrasting nutrients and used a before–after–control–impact-paired design. The negative observed effects of stagnation and drought on water quality and benthic invertebrate communities reflect the great susceptibility of lowland streams to global changes.

We tested the hypothesis that the hydrological regime of large rivers affects the structure of invertebrate communities and food webs, by investigating two lakes with different connectivity to the fluvial system and over three hydroperiods. The present study exemplifies a quantitative approach to floodplain food-web analysis, which can be a valuable tool for the analysis of spatiotemporal variation in trophic interactions.

The biology of angel sharks (Squatina sp.) and sawharks (Pristiophorus sp.) was assessed using animals captured in south-eastern Australia. Data indicated that there are morphological features that allow the separation of concurrent species, and we provide ratios that allow accurate predictions of total lengths from truncated specimens.

The present study investigated spatiotemporal variation of key prey fishes in the Murray Estuary and Coorong. Small-mouth hardyhead dominates the South Lagoon, and sandy sprat and Tamar goby occur in the North Lagoon at a low abundance, but both are absent from the South Lagoon. The change of prey-fish abundance is mainly driven by salinity. The study has improved our understanding on the dynamics of small-bodied fish species and key environmental factors regulating fish distribution.

In the present study we assessed the origin of introduced populations of Mytilus galloprovincialis in the north-western Pacific, providing new insight into the biogeography of M. galloprovincialis. The results showed that populations of M. galloprovincialis in the north-western Pacific were introduced from the middle Mediterranean Sea and that the Dalian population was the first colonised population in Chinese coastal waters.

Introduced algae have the potential to substantially modify native communities. The present study describes the distribution and density of Sargassum muticum in shallow subtidal areas in Galicia (north-western Spain) and shows what factors might be behind its establishment. The study also demonstrates the usefulness of zero-inflated models to assess early and mid-stages of a seaweed invasion.

The present study used the global and local regression models to explore the relationships between walleye abundance (Stizostedion vitreum) distribution and habitat variables in Lake Erie. The relationship was found to vary spatially and was scale-dependent. Our study highlights the importance of considering local regression. It also provides extra knowledge on zonation of species-habitat relationships and validates walleye management units to a degree.

The size-specific and composition relationships between zooplankton and phytoplankton were evaluated in a large subtropical lake. The zooplankton to phytoplankton biomass ratio was usually very low, indicating a weak top-down control; however, the strength of this interaction varied with zooplankton composition and temporal or spatial variability of the environmental factors. The environmental variability induced by wind action and diversification of niches played a substantial role in the capacity of zooplankton in controlling the phytoplankton biomass.

To disentangle the direct and indirect effects of ocean acidification on zooplankton growth, we undertook a study with two model organisms, Oxyrrhis marina and Acartia tonsa. Direct pH effects on consumers seem to be of lesser importance than the associated decrease in algal quality. The decrease in the quality of primary producers under high pCO₂ conditions negatively affected zooplankton growth.

This paper investigated population genetic structure of Euastacus armatus across its present range to provide insight into recovery potential in the species. We revealed low levels of gene flow sufficient to maintain population sizes and genetic diversity, but also local genetic structuring and limitations on dispersal were evident. These findings forecast limited potential for natural recolonisation and recovery following the decline of local populations.

We provide a comment to highlight and correct some errors contained in a recently published paper on the community composition of fishes in dry-land rivers in north-western Zimbabwe. With its errors, inadequate sampling and data collection, and the superficial and confusing data analysis, this paper cannot be said to have advanced our understanding of the fishes of Zimbabwe.

The effects of ash from controlled fires on macroinvertebrate communities in UK headwater streams were investigated experimentally by depositing ash onto natural stream substrata in trays placed on streambeds. Ash deposition together with stream depth altered macroinvertebrate community composition. However, changes in species composition caused by ash deposition were smaller than differences among streams, suggesting that effects of ash may be small in these streams.