Colonization and community development of fish assemblages associated with estuarine artificial reefs

A despeito da longa história do desenvolvimento de estruturas artificiais nos estuários de NSW, não existem estudos que apresentem uma avaliação global sobre os efeitos obtidos com o estabelecimento dessas estruturas. No presente trabalho abordamos a efetividade dos recifes artificiais estuarinos como iniciativa para aumento da pesca; descrevemos a diversidade e abundância das espécies a eles associadas; descrevemos os padrões de colonização e o desenvolvimento das comunidades associadas a um recife artificial colocado no Lago Macquaire, extensa lagoa de barreira situada na costa sudeste da Australia. Seis recifes artificiais (formando um único grupo), construídos a partir de unidades artificiais (Reef Balls®), foram lançados em Dezembro de 2005 e amostrados seis vezes a cada estação do ano, durante dois anos, utilizando video subaquático remoto (BRUV). A colonização dentro do grupo de recifes ocorreu de maneira relativamente rápida, sendo que a maioria das espécies identificadas nos dois anos de estudo foi observada durante o primeiro ano de amostragem. Um total de 27 espécies pertencentes a 17 famílias foram identificadas. As espécies chave do processo de colonização foram Pelates sexlineatus (Teraponidae), Acanthopagrus australis (Sparidae), Pagrus auratus (Sparidae) and Rhabdosargus sarba (Sparidea). A riqueza de espécies mostrou evidência de sazonalidade, enquanto a diversidade aumentou significativamente com o aumento da idade do recife. A composição da assembléia de peixes permaneceu relativamente estável após o primeiro ano de amostragem, com poucos padrões identificáveis relativos à estrutura. Durante o segundo ano tornou-se evidente a formação de grupos por idade, padrão primariamente ocasionado pelo decréscimo na abundância de P. sexlineatus; por sua vez este decréscimo mostrou ser resultado da natureza isolada do recife artificial e dos efeitos interdependentes de abundância e predação.Despite the long history of the development of artificial structures in NSW estuaries there are no studies that provide any comprehensive scientific evaluation of post-deployment goals. We assessed the effectiveness of estuarine artificial reefs as a fisheries enhancement initiative; described the diversity and abundance of species associated with them, and detailed the patterns of colonization and community development associated with an artificial reef deployment in Lake Macquarie, a large coastal barrier lagoon on the southeast coast of Australia. Six artificial reefs (one artificial reef group), constructed from artificial reef units (Reef Balls®), were deployed in December 2005 and sampled six times per season over two years using baited remote underwater video (BRUV). Colonization of the artificial reef group was relatively rapid with the majority of species identified over the two-year study period observed within the first year post-deployment. Overall, 27 species from 17 families were identified. Key colonising species included Pelates sexlineatus (Terapontidae), Acanthopagrus australis (Sparidae), Pagrus auratus (Sparidae) and Rhabdosargus sarba (Sparidae). Species richness showed evidence of potential seasonal fluctuations, being higher in warm water months (Summer/Autumn), and lower in the colder water months (Winter/Spring), while species diversity increased significantly with reef age. Fish assemblage composition remained relatively stable after the first year of sampling, with few discernible patterns in assemblage structure evident after the first year. Distinct separation in reef age groupings was evident during the second year of sampling; a pattern primarily driven by a decrease in abundance of P. sexlineatus, a result of the isolated nature of the artificial reefs and the interrelated effects of density dependence and predation

Lifting fish across barriers with the Tube Fishway: lessons from the laboratory

To transfer fish across barriers, fishways are commonly used. A multidisciplinary research team from UNSW Sydney, has made important progress on the operation of a new type of fishway, the Tube Fishway, under controlled conditions in the laboratory. Research has shown that fish can be successfully attracted into the Tube Fishway's transfer chamber, while an innovative lifting mechanism based upon an unsteady surge, has been introduced to avoid the use of a mechanical pump. Using this lifting mechanism, tests with juvenile Australian bass (Percalates novemaculeata) and silver perch (Bidyanus bidyanus) have shown that fish can be safely lifted in Tube Fishways with heights of 4 and 8 m. Replacing live fish with a neutrally buoyant sensor packet, has provided important guidance on the pressures and accelerations that fish would experience during operation of the Tube Fishway. Trials with an automated Tube Fishway have demonstrated the fully automated operation of the Tube Fishway paving the way for upcoming field installations of Tube Fishways. Important lessons from the laboratory experiments are discussed and future research needs addressed

Using integrative taxonomy to distinguish cryptic halfbeak species and interpret distribution patterns, fisheries landings, and speciation

Context. Species classification disputes can be resolved using integrative taxonomy, which involves the use of both phenotypic and genetic information to determine species boundaries. Aims. Our aim was to clarify species boundaries of two commercially important cryptic species of halfbeak (Hemiramphidae), whose distributions overlap in south-eastern Australia, and assist fisheries management. Methods. We applied an integrative taxonomic approach to clarify species boundaries and assist fisheries management. Key results. Mitochondrial DNA and morphological data exhibited significant differences between the two species. The low level of mitochondrial DNA divergence, coupled with the lack of difference in the nuclear DNA, suggests that these species diverged relatively recently (c. 500 000 years ago) when compared with other species within the Hyporhamphus genus (>2.4 million years ago). Genetic differences between the species were accompanied by differences in modal gill raker counts, mean upper- jaw and preorbital length, and otolith shape. Conclusions. On the basis of these genetic and morphological differences, as well as the lack of morphological intergradation between species along the overlapping boundaries of their geographical distributions, we propose that Hyporhamphus australis and Hyporhamphus melanochir remain valid species. Implications. This study has illustrated the need for an integrative taxonomic approach when assessing species boundaries and has provided a methodological framework for studying other cryptic fish species in a management context

Modelling the possible effects of climate change on an Australian multi-fleet prawn fishery

The relationship between fisheries and climate has been given renewed emphasis owing to increasing concern regarding anthropogenically induced climate change. This relationship is particularly important for estuarine fisheries, where there are documented correlations between river discharge and productivity. The commercial catch of school prawns (Metapenaeus macleayi) has been shown to be positively correlated with the rates of river discharge in northern New South Wales, Australia. In the present study, a simulation model was developed to analyse the dynamics of the stock for 10 years under alternative river discharge scenarios, and the effectiveness of a series of management strategies under these scenarios was examined. A size-based metapopulation model was developed that incorporated the dynamics of school prawn populations in three habitats being harvested by three different fishing methods. The model indicated that both the growth and movement of prawns were affected by the rates of river discharge, and that higher rates of river discharge usually generated increased commercial catches, but this outcome was not certain. It was concluded that the population does not appear to be over exploited and that none of the three alternative management strategies performed better within the model than the current spatio-temporal closures, even under a wide range of river discharge scenarios

Distribution of Palinuridae and Scyllaridae phyllosoma larvae within the East Australian Current: a climate change hot spot

Many marine species are predicted to shift their ranges poleward due to rising ocean temperatures driven by climate change. For benthic marine species with pelagic larval stages, poleward range shifts are often facilitated through pelagic larval transport via western boundary currents (WBC). By surveying pelagic larval distributions within WBCs, species advected poleward of their known distributions can be identified and monitored. Palinurid and scyllarid lobster larvae (phyllosoma) have long pelagic larval durations, providing high potential for poleward advection. We surveyed spatial distribution of phyllosoma within the western-boundary East Australian Current. Due to difficulties morphologically identifying phyllosoma, we tested the utility of molecular identification using cytochrome c oxidase I (COI). From COI sequences of 56 phyllosoma and one postlarva, 65% of sequences consisted of good-quality mitochondrial DNA. Across water types sampled, scyllarid phyllosoma exhibited relatively homogeneous distribution, whereas palinurid phyllosoma exhibited heterogeneous distribution with greatest abundance inside a warm core eddy on the south coast of eastern Australia. Two tropical and one subtropical palinurid species were detected ~75–1800 km to the south or south-west of their known species distribution. Our results indicate tropical lobster species are reaching temperate regions, providing these species the opportunity to establish in temperate regions if or when environmental conditions become amenable to settlement

A deep dive into the ecology of Gamay (Botany Bay, Australia): current knowledge and future priorities for this highly modified coastal waterway

Context: Gamay is a coastal waterway of immense social, cultural and ecological value. Since European settlement, it has become a hub for industrialisation and human modification. There is growing desire for ecosystem-level management of urban waterways, but such efforts are often challenged by a lack of integrated knowledge. Aim and methods: We systematically reviewed published literature and traditional ecological knowledge (TEK), and consulted scientists to produce a review of Gamay that synthesises published knowledge of Gamay’s aquatic ecosystem to identify knowledge gaps and future research opportunities. Key results: We found 577 published resources on Gamay, of which over 70% focused on ecology. Intertidal rocky shores were the most studied habitat, focusing on invertebrate communities. Few studies considered multiple habitats or taxa. Studies investigating cumulative human impacts, long-term trends and habitat connectivity are lacking, and the broader ecological role of artificial substrate as habitat in Gamay is poorly understood. TEK of Gamay remains a significant knowledge gap. Habitat restoration has shown promising results and could provide opportunities to improve affected habitats in the future. Conclusion and implications: This review highlights the extensive amount of knowledge that exists for Gamay, but also identifies key gaps that need to be filled for effective management

A function-based typology for Earth’s ecosystems

As the United Nations develops a post-2020 global biodiversity framework for the Convention on Biological Diversity, attention is focusing on how new goals and targets for ecosystem conservation might serve its vision of ‘living in harmony with nature’(1,2). Advancing dual imperatives to conserve biodiversity and sustain ecosystem services requires reliable and resilient generalizations and predictions about ecosystem responses to environmental change and management(3). Ecosystems vary in their biota(4), service provision(5) and relative exposure to risks(6), yet there is no globally consistent classification of ecosystems that reflects functional responses to change and management. This hampers progress on developing conservation targets and sustainability goals. Here we present the International Union for Conservation of Nature (IUCN) Global Ecosystem Typology, a conceptually robust, scalable, spatially explicit approach for generalizations and predictions about functions, biota, risks and management remedies across the entire biosphere. The outcome of a major cross-disciplinary collaboration, this novel framework places all of Earth’s ecosystems into a unifying theoretical context to guide the transformation of ecosystem policy and management from global to local scales. This new information infrastructure will support knowledge transfer for ecosystem-specific management and restoration, globally standardized ecosystem risk assessments, natural capital accounting and progress on the post-2020 global biodiversity framework

A guide to the extraction and interpretation of otoliths from larval and pelagic juvenile Arcto-Norwegian cod.

The techniques for extraction of the lapillar otoliths, and interpretation of otolith microstructure in Arcto-Norwegian cod (Gadus morhita L.) is outlined and reviewed. Increment deposition in this species is daily, commencing at hatch, with the possiblity of the first 2-3 daily growth increments being overlooked. Post-larval otoliths of this stock provide some difficulties in interpretation of a daily increment, probably due to rapid growth in the post-larval stage (nearly twice that of western Atlantic cod) and their growth in 24 h daylight. Using the light microscope, increments may be enumerated from 1 to over 120 days post-hatch. Use of the lapillus over the sagitta is recommended. The lapillus radius is linearly related to length, and increment widths seem closely related to feeding rates. NORSK SAMMENDRAG:Teknikken forbundet med å plukke ut og tyde mikrostrukturen i otolitter fra larver og postlarver av Norsk-Arktisk torsk' er beskrevet i dette arbeidet. Soner blir lagt ned daglig og sonenedleggingen starter ved klekking. Det er imidlertid lett å overse de ferste 2-3 sonene da disse er smale og utydelige. Det kan også være noen problemer forbundet med tolkningen av dagsonemensteret i otolittene til postlarver. Årsaken til dette kan være at de vokser svært raskt (dobbelt så raskt som postlarver av torsk fra kysten av Canada), og at de oppholder seg i et milje med kontinuerlig lys. Ved hjelp av lysmikroskop kan en telle opp til 120 dagsoner. Det anbefales å benytte lapillus framfor sagitta. Det er en lineær sammenheng mellom otolittradius og larvelengde, og det synes også å være en klar sammenheng mellom sonebredde og fedeinntak