Most stocking of native fish is conducted without information on its effectiveness or impacts. We stocked chemically tagged golden perch (Macquaria ambigua) fingerlings in three rivers of the Murray–Darling Basin (MDB), Australia. Subsequent sampling found that stocked fish contributed 18–100% of year classes within each river, demonstrating the potential for artificial stocking to strongly influence the abundance and structure of golden perch populations in the MDB.

Murray cod and golden perch have been released from government and private hatcheries since the late 1970s in response to large scale wild fishery declines. Assessing success of these long-term stocking programs has been limited. Hatchery-reared fish were marked with calcein prior to release. The contribution of marked Murray cod varied by 7–94% and 9–98% for marked golden perch with higher proportions of marked fish found in impoundments than rivers. The comparatively low proportion of marked fish in rivers suggests that these populations are primarily self-supporting through natural recruitment rather than artificial enhancement. Identifying self-sustaining fish populations, and conversely, those that are heavily reliant on stocking, will allow delivery of hatchery-reared fish to areas where they are most needed.

Krill-like shrimps A. erythraeus and A. intermedius live together in Panguil Bay, Philippines and have an overlapping diet of primarily zooplankton and detritus. However, they partition the feeding niche with differences in prey types, gut fullness over 24 h and among months, sources of plant detritus, and with A. erythraeus confined to more brackish waters and A. intermedius dwelling in more saline marine waters of the bay.

Defining population units that balance productivity and yield is a fundamental aspect of resource management. We investigated the presence of groups of snapper with different life-history strategies within the Hauraki Gulf, New Zealand, using a range of techniques. Snapper collected from a known spawning area possessed distinct morphology and stable isotope ratios, suggesting the existence of a semi-pelagic group of snapper within the Hauraki Gulf stock.

The environmental parameters, microphytoplankton and ciliate communities in the area were studied in two seasons at 20 stations along the coast south of Sfax. The results showed that the environmental parameters indicated high nutrient levels. Seventy-eight microphytoplankton species and 58 ciliates species were identified in all stations. Some species reported in this study are commonly found in the stressed coastal waters.

Freshwater elasmobranchs are threatened but little known. This paper shows that Potamotrygon brachyura is associated to large lowland rivers, and that most of its range in the Río de la Plata is subject to high levels of habitat modification, whereas in the Uruguay and Paraná basins fishing pressure is its main stressor. P. brachyura may function as an umbrella species.

Poorly understood larval recruitment and dispersal can drive fish population dynamics; we studied how interspecific life-history differences affected these processes in a group of closely related galaxiids. Consistent with a priori predictions, the larvae of ‘fast’ life-history species were abundant and dispersed widely, whereas 'slow' life-history species produced low numbers of larvae which were relatively sedentary. We discuss the implications of these findings for metapopulation structure and how these species interact with invasive salmonids.

A novel integrated sampling method was used to score the structure of seagrass meadows in the New Caledonian lagoon. On average, meadows scored at 69/100, indicating ‘fair-to-good’ structure, although significant variation was evident among sites and appeared to reflect differences in wave exposure. The study shows the value of integrated sampling methods for rapid spatio-temporal comparisons that can provide early warning signs of habitat decline.

Replanting native vegetation adjacent to agricultural streams aims to improve in-stream biodiversity but the capacity of such replanting to combat the effects of large-scale land-use change is unknown. We tested whether aquatic macroinvertebrates responded to streamside replanting, but found that whole-catchment factors were more important. Replanting in degraded areas may not restore aquatic biodiversity within decades, necessitating careful consideration of restoration aims and monitoring methods.

This study examines the potential impacts of anthropogenic climate change on evaporation from small reservoirs in the Lockyer catchment in south-east Queensland, Australia. Future projections indicated that evaporation is expected to increase by ~6% by 2050. This predicted increase in evaporation, combined with expected reductions in rainfall and runoff, means that water resources may be significantly affected in the future.

Shallow coastal lakes are sensitive to human-induced environmental changes. Post-colonial land-use change and water level control in and around Wainono Lagoon, South Canterbury, New Zealand, transformed it from a clear, macrophyte-dominated freshwater state to a turbid, hypereutrophic brackish system with little or no macrophytes. This study illustrates how the palaeolimnological approach can provide useful knowledge to assist the management and safeguard of these vulnerable ecosystems.

Shallow-coastal habitat research has previously focussed on larvae and juvenile fish communities and their use of these habitats as nurseries. The current study focuses on sampling a mosaic of shallow-coastal habitats and identifying the large-bodied fish communities utilising these habitats. We suggest these habitats may provide multiple functions for large-bodied fish communities and new insight into the additional functions of shallow-coastal habitats.

A tropical population of the piked spurdog was found to be smaller and older at maturity than temperate populations. The Philippine spurdog was late maturing and long lived at 27 years. Both species were slow growing with conservative life history traits that make them vulnerable to exploitation but, in the event of overfishing, the deeper-dwelling Philippine spurdog is likely to take longer to recover.

We analysed isotopic composition of small omnivorous fishes (smaller than ~100 mm long) to examine whether they integrate littoral, pelagic and benthic pathways in a shallow, eutrophic lake (Lake Izunuma, Japan). Five omnivorous fish relied mostly on epiphytic algae and zooplankton, whereas zoobenthos (larval chironomids) contributed little to their diets. Thus, in Lake Izunuma, omnivorous fishes incorporated both littoral and pelagic production into the food web, but rarely benthic production.

Mature anguillid eels in Lake Poso, Indonesia, are found to repeat up-and-down movements in the water column (maximum depth, 77 m), with slower, less active descents with shallower postures, followed by faster, more active ascents with steeper postures. These characteristic movements might be owing to the eels’ internal motivation for continuous swimming in preparation for oceanic migration.

Hypoxia is increasing in freshwater and estuarine systems globally, yet we know little about the ability for tropical fish to acclimate to this changing environment. This study investigated the acclimation potential of two geographically separated populations of barramundi (L. calcarifer) to fluctuating oxygen availability. Hypoxia tolerance improved similarly in both populations and was driven primarily by physiological plasticity, rather than inherent variability between populations.

Studies of the parasitic helminths in Sardina pilchardus and Engraulis encrasicolus from the Bay of Biscay revealed the occurrence of only three species of nematodes in both fish species. This low diversity of helminth parasites, compared with the 39 and 15 taxa for S. pilchardus and E. encrasicolus respectively described throughout their distribution range, suggests a low free-living biodiversity in the Bay of Biscay, potentially indicative of stressed ecosystems.

The size of an organism's home range dictates the spatial scale on which ecological processes occur. Many reef fish have limited home-ranges and here, we quantify variability in the home-ranges of juveniles of an abundant reef fish in New Zealand, the common triplefin. Results suggest that individual space use becomes restricted when densities of neighbouring conspecifics surpass a critical threshold, which could reduce individual fitness in high density areas as well as shape the spatial distribution of juveniles across a population.