Marine and Freshwater Research
Number 1 2018
This review is the first on Bythograeidae, documenting the state of our knowledge regarding their taxonomy, evolution, ecology, morphology and physiology (i.e. osmoregulation, oxygen consumption, sulfide and metal detoxification, temperature tolerance). We also report on recent progress in maintaining bythograeids in an artificial ex situ environment.
Butterfly kingfish (Gasterochisma melampus) is a large Scombridae species distributed in circumpolar temperate waters of the Southern Hemisphere whose ecological characteristics were unknown. Observation of gonads collected by longline operations revealed that spawning took place in the south-east Pacific Ocean from mid-April to mid-July. The present study promotes an understanding of the life history and stock structure of this species.
The Australian bass is a long-lived native fish. Little is known of the timing of flows important for recruitment of the species in the south of its range. We found recruitment was related to high flows in spring and increasing water temperatures at the time. Lower rainfall and higher temperatures in the region may result in prolonged periods of recruitment failure over the medium to longer term.
This study examined two approaches to ageing Pacific spiny dogfish and inter-laboratory variability. Age estimates from dorsal fin spines (historical method) did not agree with age estimates from vertebrae (new method) for older fish, suggesting the new method is not appropriate for fish aged over 10 years. However, inter-laboratory variability was improved using the new method. Results suggest further investigation of the new method is warranted.
Analysis of the stomach contents of the 630 Squalus megalops examined in the Gulf of Gabès (Tunisia) showed that the species consumed teleosts, cephalopods and crustaceans. Significant differences in the diet related to size, season and sex were noted. Trophic position and quantitative analysis revealed that the species is a secondary consumer and a generalist feeder.
This study has increased our understanding of how isotopes of carbon and nitrogen are incorporated into different tissues of consumers within a freshwater food chain. The study identified that isotopic ratios of these elements vary significantly between tissues, but strong correlations between muscle and shell suggest that the shell can be used as an alternative for muscle in certain circumstances.
The age and growth of the banded guitarfish (Zapteryx exasperata) from Baja California Sur, Mexico, was estimated for the first time based on growth band counts in its vertebrae. Larger sizes than those reported in the literature were observed for both females (103-cm total length, TL) and males (92 cm TL). Similarly, females lived longer than males (22.6 v. 19.6 years respectively).
Because predation risk and food quality are crucial in ecological communities, it is important to understand their combined effects to freshwater invertebrates, namely aquatic insect larvae, which are considered important links in freshwater food webs. Leaf decomposition decreased under predator presence, impairing insect larvae growth, this effect being exacerbated when Eucalyptus globulus, a widespread invasive species, was given as a food source.
Streams under reference conditions are necessary for the evaluation and monitoring of the conservation status of aquatic ecosystems of a region. In this study we demonstrated that a hydrological unit does not constitute a homogeneous entity in terms of environmental variables and biological composition. The results of the study will improve and facilitate the selection of reference sites for biomonitoring programs and for managing Neotropical savanna streams.
The response of different phytoplankton functional approaches to environmental variability over time was evaluated in a large subtropical shallow lake. Dissimilarity in phytoplankton functional composition was related to nutrient and light conditions, even though the sensitivity of the approaches seemed to differ with regard to environmental variability. The functional group composition of phytoplankton sensu Reynolds et al. (https://doi.org/10.1093/plankt/24.5.417) seemed to be the most effective system in describing environmental variability in Lake Mangueira, in southern Brazil, over the long term.
Distance decay was used as a descriptor of the compositional variation in diatom community similarity over six reservoirs (São Paulo, Brazil). Similarity decreased with distance between habitats and seasons, but the results were not statistically significant for surface sediment assemblages. Diatom communities were controlled more by limited dispersal, probably as a result of the water quality and scale of the study area.
Invertebrate diversity in subterranean groundwater calcretes of central Western Australia is influenced by periodic rainfall events. After rainfall, taxonomic richness in boreholes increased, as shown by an 11-year survey. Taxonomic groups such as small crustaceans (copepods, amphipods) and dytiscid beetles were the common groups, increasing in numbers during these rainfall periods. An understanding of invertebrate diversity patterns and how they vary temporally will provide information for the management of these groundwater ecosystems.
The degradation of freshwater ecosystems is a threat to biodiversity. We evaluated the influence of water quality on the occurrence of a threatened mammal, the Neotropical otter in a river basin under different degradation levels. We found the Neotropical otter to be tolerant to human-altered environments; however, beyond a certain threshold of water-quality degradation, its persistence is at risk.
During a routine environmental monitoring in the Bahía Blanca Estuary, a temperate and eutrophic ecosystem on the Argentine coast, a parasitic infection was documented on phytoplankton. The host-specific infection on diatoms co-occurred with an extreme precipitation period in the region. Afterwards, the phytoplankton composition and size structure shifted towards dominance of smaller species.
Mangrove seedlings planted along an artificial tidal creek at Port Hedland, Australia, showed 18% survival after 3 years. Large numbers of seedlings had recruited naturally into the site. Seedling survival was affected by tidal elevation, but not by creek bank design or erosion protection. Given the right environmental conditions, mangroves will re-establish naturally, although recovery may take >10 years in this semi-arid region.
Over 30 years of provisioning has led to a predictable aggregation of southern stingrays in Grand Cayman, which is visited by over one million people annually. Despite the economic importance of this aggregation, there had never been a formal assessment of the aggregation. Using previous tagging data and structured censuses, we describe the dynamics of this popular wildlife tourism destination.
The analyses performed showed the following effects of the P. antipodarum invasion on the macroinvertebrate community of a temperate mesotrophic lake: a definite increase in the total macroinvertebrate biomass, a significant increase in the local macroinvertebrate family richness and diversity, a shift in the community composition from crustacean- to gastropod-dominated.
The influence of environmental variables on shark catch in the bather-protection program along the South African East Coast was investigated for 11 species. Results suggested that measurable, predictable relationships exist between environmental conditions and presence and, consequently, catch of shark species in this program. Understanding these relationships could be useful to mitigate against unwanted catch and to further reduce risk for bathers.
Although mailing of live or dead organisms is forbidden in Brazil, smugglers use the postal service to transport aquarium species throughout the country. To assess this illegal practice, confiscations comprising native (including species threatened with extinction) and non-native organisms were performed. Brazilian authorities must intensify package inspections, especially in the south-eastern region, because seizures seem to mitigate the illicit transportation of aquarium species to some extent.
The present study examined the effects of nudibranch predation on behaviour of the geographically restricted and potentially threatened soft coral species Dendronephthya australis. Observations clearly demonstrated the negative impact of predation on feeding ability of this soft coral and suggested that interactions with additional anthropogenic stressors may increase mortality risk for this important habitat-forming species.
Warm sea temperatures affected the Great Barrier Reef in the summer of 2016, causing severe coral bleaching in northern and central reef regions. Southern reef areas were thought to escape bleaching; however, herein we report minor coral bleaching around the Keppel Islands (14 sites). Approximately 21% of corals were mildly affected, with Pocillopora and some Acropora appearing sensitive. No mortality was observed. This study contributes to the long-term records of disturbance and recovery dynamics in the Keppel Islands.