Marine and Freshwater Research
Number 5 2017
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.
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.
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.
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.
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.
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.
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 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.
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 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.
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.
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 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.
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.
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.
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.
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.
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.