Within each of ~30 isolated aquifers in central Western Australia, 2–3 different-sized stygobitic diving beetle species have evolved, raising questions on whether selection on body size differences and speciation underground resulted from using different food resources. Using a combination of PCR analyses and stable isotope analyses, our study found evidence for partial differences in the diet between different-sized beetles. Behavioural observations provide further information on how species may co-exist within these communities.

Underwater visual censuses performed by divers are widely used for studying fish communities. Recent alternatives are underwater video techniques, like remotely operated vehicles and remote underwater video. We studied a temperate fish community by the three techniques. Divers obtained faster and better inventories, but we would also recommend video techniques in long-term studies, in greater depths and in adverse weather conditions.

Animals with variable diets can have considerable impacts on food webs. We investigated the diets of two closely related tropical estuarine fish and found they were feeding in different food webs at sites only hundreds of metres apart. This means these species had different feeding roles at different locations leading to substantial variations in the operation of food webs.

Pseudoplatystoma fasciatum represents one of the most important continental fisheries of the Orinoco River Basin. Therefore, basic information on population and reproductive parameters is required for its adequate management. The results showed that the reproductive cycle of P. fasciatum, effectively takes place in the delta of the Orinoco River, even though the sizes at maturity were smaller than others reported for the species.

The allocation of water to the environment is increasingly competitive so that an array of environmental flow methods has developed. Our view is that few have been implemented and evaluated in a research and management context and there is poor connection between current trends in E-flow literature with assessment of efficacy and practical application. We suggest steps that will improve the applicability, implementation and ultimate success of E-flows for river management.

Despite their importance in marine ecosystems, groupers are still poorly investigated in some areas. We studied the reproductive parameters of an endangered grouper species (Epinephelus marginatus) and revealed it reproduces at Carpinteiro Bank, a seamount located in the southern limit of its distribution in the south-western Atlantic. Fishing managers should protect this important reproductive site from increasing and unregulated fishing pressure.

The value of point-sampling of estuarine environments is contentious. This paper examined the relationship between water quality of subtropical estuaries in spring and predetermined health classification using chemical and biological indicators. Where continuous water-quality monitoring is unavailable, useful information can be derived from water-quality sampling in the spring months combined with biological indicators.