Mike Cappo

Adaptive management of the Great Barrier Reef: A globally significant demonstration of the benefits of networks of marine reserves

The Great Barrier Reef (GBR) provides a globally significant demonstration of the effectiveness of large-scale networks of marine reserves in contributing to integrated, adaptive management. Comprehensive review of available evidence shows major, rapid benefits of no-take areas for targeted fish and sharks, in both reef and nonreef habitats, with potential benefits for fisheries as well as biodiversity conservation. Large, mobile species like sharks benefit less than smaller, site-attached fish. Critically, reserves also appear to benefit overall ecosystem health and resilience: outbreaks of coral-eating, crown-of-thorns starfish appear less frequent on no-take reefs, which consequently have higher abundance of coral, the very foundation of reef ecosystems. Effective marine reserves require regular review of compliance: fish abundances in no-entry zones suggest that even no-take zones may be significantly depleted due to poaching. Spatial analyses comparing zoning with seabed biodiversity or dugong distributions illustrate significant benefits from application of best-practice conservation principles in data-poor situations. Increases in the marine reserve network in 2004 affected fishers, but preliminary economic analysis suggests considerable net benefits, in terms of protecting environmental and tourism values. Relative to the revenue generated by reef tourism, current expenditure on protection is minor. Recent implementation of an Outlook Report provides regular, formal review of environmental condition and management and links to policy responses, key aspects of adaptive management. Given the major threat posed by climate change, the expanded network of marine reserves provides a critical and cost-effective contribution to enhancing the resilience of the Great Barrier Reef.

The accuracy and precision of underwater measurements of length and maximum body depth of southern bluefin tuna (Thunnus maccoyii) with a stereo-video camera system

The accuracy and precision of in situ stereo-video measurements of the snout to fork length (SNFL) (range 830-1412 mm) and maximum body depth (MBD) (range 228-365 mm) of free-swimming southern bluefin tuna (SBT) (Thunnus maccoyii) were tested by filming live fish in sea cages immediately prior to harvest. Stereo-video measurements of the SNFL of 54 fish produced an average error of 1.72 mm (relative error of 0.16%), while an average error of 1.37 mm (relative error of 0.51%) was recorded for measurements of MBD from 47 fish.A procedure was developed to maximise the accuracy and precision of measurements of the SNFL and MBD from a single SBT over sequential images to avoid the underestimation of SNFL and overestimation of MBD due to sinusoidal changes in body form associated with fast swimming.The results demonstrate the potential of stereo-video systems to non-destructively make counts and measurements of tuna and other fish in both wild fisheries and mariculture situations, without the need to capture and handle them

Age, growth, mortality rates and corresponding yield estimates using otoliths of the tropical red snappers, Lutjanus erythropterus, L. malabaricus and L. sebae, from the central Great Barrier Reef☆

Abstract Otoliths of L. erythropterus, L. malabaricus and L. sebae from the central Great Barrier Reef contain a well defined series of opaque and translucent increments known to be deposited annually. These three species are relatively long-lived, and grow slowly after becoming reproductively mature. Age estimates up to 32 years for L. erythropterus, 20 years for L. malabaricus and 22 years for L. sebae were much higher than those previously reported from other northern Australian waters. Age estimates obtained from counts of increments on whole otoliths were consistently much lower and more imprecise, at all ages compared with counts from sectioned otoliths. Precision of counts from whole otoliths declined significantly with increasing fish age. The regression of sectioned age on otolith weight revealed consistent linear relationships among all three species. To explore the fishery research and management implications of these biases, age estimates from the two ageing methods were used to construct comparative growth and mortality parameters and model yield-per-recruit values under contrasting harvest strategies. While the von Bertalanffy growth functions were not significantly different for the two methods, the underestimates of age from whole otoliths caused serious over-estimation of natural mortality. Serious overfishing could occur if these estimates were applied for fishery management purposes.

Tracing the life history of individual barramundi using laser ablation MC-ICP-MS Sr-isotopic and Sr/Ba ratios in otoliths

Otoliths preserve a continuous geochemical record of its life history, from the earliest natal stage through to adulthood. Using in situ laser ablation (UV) multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) measurements of Sr isotopic compositions together with elemental abundances (Ca, Sr, Ba and Mg), we show how it is possible to characterise the various types of habitats encountered throughout the lifecycle history of individual barramundi. Unlike trace element concentrations, which can be modulated by physiological processes, Sr isotopic compositions of otoliths provide a direct fingerprint of the water mass in which the fish lived. Elemental abundances, in particular Sr/Ba ratios are, however, shown to be especially sensitive to transitional environments, such as estuaries. The flexibility of the barramundi’s life history is confirmed by the present study, with the existence of both marine and freshwater nurseries, with some individuals spending their entire life cycle in fresh water, some entirely in marine and others moving between freshwater estuarine and marine habitats.

A comparison of the accuracy and precision of measurements from single and stereo-video systems

Underwater tests using plastic silhouettes of fish were used to compare the accuracy and precision of measurements made with a single video camera system to those made from two stereo-video systems (one using digital camcorders, the other using Hi8 camcorders). Test measurements made across a variety of ranges and angles of silhouette orientation in the fields of view showed the length estimates from both the digital and Hi8 stereo-video systems were substantially more accurate and precise than those obtained by the single video camera system, and had the great advantage that the position (range and bearing) and orientation of a fish target could be measured directly. Measurements made with stereo-video were much less restricted by range and subject orientation than those made with single video. The data resulting from these trials are used to propose a set of guidelines to optimize the accuracy and precision of underwater measurements of fish length using single and stereo-video systems.

Quantifying shark distribution patterns and species-habitat associations: implications of marine park zoning.

Quantifying shark distribution patterns and species-specific habitat associations in response to geographic and environmental drivers is critical to assessing risk of exposure to fishing, habitat degradation, and the effects of climate change. The present study examined shark distribution patterns, species-habitat associations, and marine reserve use with baited remote underwater video stations (BRUVS) along the entire Great Barrier Reef Marine Park (GBRMP) over a ten year period. Overall, 21 species of sharks from five families and two orders were recorded. Grey reef Carcharhinus amblyrhynchos, silvertip C. albimarginatus, tiger Galeocerdo cuvier, and sliteye Loxodon macrorhinus sharks were the most abundant species (>64% of shark abundances). Multivariate regression trees showed that hard coral cover produced the primary split separating shark assemblages. Four indicator species had consistently higher abundances and contributed to explaining most of the differences in shark assemblages: C. amblyrhynchos, C. albimarginatus, G. cuvier, and whitetip reef Triaenodon obesus sharks. Relative distance along the GBRMP had the greatest influence on shark occurrence and species richness, which increased at both ends of the sampling range (southern and northern sites) relative to intermediate latitudes. Hard coral cover and distance across the shelf were also important predictors of shark distribution. The relative abundance of sharks was significantly higher in non-fished sites, highlighting the conservation value and benefits of the GBRMP zoning. However, our results also showed that hard coral cover had a large effect on the abundance of reef-associated shark species, indicating that coral reef health may be important for the success of marine protected areas. Therefore, understanding shark distribution patterns, species-habitat associations, and the drivers responsible for those patterns is essential for developing sound management and conservation approaches.

Development of a robust classifier of freshwater residence in barramundi (Lates calcarifer) life histories using elemental ratios in scales and boosted regression trees

Field and experimental studies showed that solution-based analysis of scales could be used to discriminate the long-term freshwater residents in the coastal fishery for catadromous barramundi. A new, robust classification technique was developed using boosted regression trees (MART) and its performance was compared with traditional linear discriminant analysis (LDA). The non-parametric MART had errors 33–81% less than LDA, and could account for non-linear relationships and interactions among elemental ratios. The best model used Sr : Ca, Ba : Ca, Fe : Ca and Mn : Ca in scales as predictors of salinity regime. Analysis of scales collected repeatedly from sub-adult fish of known environmental history showed the MART classifier could identify fish of freshwater origin until at least 10 months residence in seawater, and possibly several years, but scale growth rate could affect the temporal stability of the classifier after that time. The experiment indicated an approximate fourfold rise in Sr : Ba ratios in new scale margins, which were strongly classified by the MART as coming from saltwater fish, but inner scale sections of the same scales were still correctly classified as coming from freshwater fish. We conclude that solution-based elemental analyses of whole scales, and also annuli within scales, could offer a cost-effective, non-destructive technique to help understand the mechanisms causing enhanced year-class strength following high freshwater outflows.

Coastal fish assemblages reflect geological and oceanographic gradients within an Australian zootone

Distributions of mobile animals have been shown to be heavily influenced by habitat and climate. We address the historical and contemporary context of fish habitats within a major zootone: the Recherche Archipelago, southern western Australia. Baited remote underwater video systems were set in nine habitat types within three regions to determine the species diversity and relative abundance of bony fishes, sharks and rays. Constrained ordinations and multivariate prediction and regression trees were used to examine the effects of gradients in longitude, depth, distance from islands and coast, and epibenthic habitat on fish assemblage composition. A total of 90 species from 43 families were recorded from a wide range of functional groups. Ordination accounted for 19% of the variation in the assemblage composition when constrained by spatial and epibenthic covariates, and identified redundancy in the use of distance from the nearest emergent island as a predictor. A spatial hierarchy of fourteen fish assemblages was identified using multivariate prediction and regression trees, with the primary split between assemblages on macroalgal reefs, and those on bare or sandy habitats supporting seagrass beds. The characterisation of indicator species for assemblages within the hierarchy revealed important faunal break in fish assemblages at 122.30 East at Cape Le Grand and subtle niche partitioning amongst species within the labrids and monacanthids. For example, some species of monacanthids were habitat specialists and predominantly found on seagrass (Acanthaluteres vittiger, Scobinichthys granulatus), reef (Meuschenia galii, Meuschenia hippocrepis) or sand habitats (Nelusetta ayraudi). Predatory fish that consume molluscs, crustaceans and cephalopods were dominant with evidence of habitat generalisation in reef species to cope with local disturbances by wave action. Niche separation within major genera, and a sub-regional faunal break, indicate future zootone mapping should recognise both cross-shelf and longshore environmental gradients.

Tropical Marginal Seas: Priority Regions for Managing Marine Biodiversity and Ecosystem Function

Tropical marginal seas (TMSs) are natural subregions of tropical oceans containing biodiverse ecosystems with conspicuous, valued, and vulnerable biodiversity assets. They are focal points for global marine conservation because they occur in regions where human populations are rapidly expanding. Our review of 11 TMSs focuses on three key ecosystems-coral reefs and emergent atolls, deep benthic systems, and pelagic biomes-and synthesizes, illustrates, and contrasts knowledge of biodiversity, ecosystem function, interaction between adjacent habitats, and anthropogenic pressures. TMSs vary in the extent that they have been subject to human influence-from the nearly pristine Coral Sea to the heavily exploited South China and Caribbean Seas-but we predict that they will all be similarly complex to manage because most span multiple national jurisdictions. We conclude that developing a structured process to identify ecologically and biologically significant areas that uses a set of globally agreed criteria is a tractable first step toward effective multinational and transboundary ecosystem management of TMSs.

The Coral Sea: Physical Environment, Ecosystem Status and Biodiversity Assets

The Coral Sea, located at the southwestern rim of the Pacific Ocean, is the only tropical marginal sea where human impacts remain relatively minor. Patterns and processes identified within the region have global relevance as a baseline for understanding impacts in more disturbed tropical locations. Despite 70 years of documented research, the Coral Sea has been relatively neglected, with a slower rate of increase in publications over the past 20 years than total marine research globally. We review current knowledge of the Coral Sea to provide an overview of regional geology, oceanography, ecology and fisheries. Interactions between physical features and biological assemblages influence ecological processes and the direction and strength of connectivity among Coral Sea ecosystems. To inform management effectively, we will need to fill some major knowledge gaps, including geographic gaps in sampling and a lack of integration of research themes, which hinder the understanding of most ecosystem processes.