Bruce D. Mapstone

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.

Scalable Decision Rules for Environmental Impact Studies: Effect Size, Type I, and Type II Errors

Assessments of environmental impacts are being subject to greater scientific and legal scrutiny than ever before. The application of traditional statistical decision-making criteria to questions of environmental impacts has become increasingly inadequate as society demands greater environmental accountability from economic development. In particular, impact assessment has inherited a preoccupation with Type I error rates that has pervaded ecological research, even though Type II errors are often equally severe in impact assess- ment. Estimation of Type II error rates and specification of critical effect sizes-or the magnitudes of impacts considered important-are mutually dependent. Consideration of Type II errors, therefore, requires the exact specification of an hypothesized impact, which is often difficult. Insistence on low rates of Type I error (e.g., at = 0.05) typically means that equivalent rates of Type II error can be realized only when effect sizes (ES) are very large or when very many samples are taken. Rather than adhering to a fixed, arbitrary, critical, Type I error rate, I propose a procedure by which the critical ES is given primacy. Statistical decision criteria are then selected according to the relative weighting of the perceived consequences of Type I or Type II errors. The critical Type I error rate is set by iteration to some multiple (k) of the estimated

Information flow among fishing vessels modelled using a Bayesian network

Abstract Reaction of fishers is an essential source of uncertainty in implementing fishery management decisions. Provided they realistically capture fisher behaviour, models of fishing vessel dynamics provide the basis for evaluating the impact of proposed management strategies. Information flow among vessels has not been a major focus of such models however, although it might play a critical role in how a fleet responds to changes to management restrictions or levels of a resource. Such a response might then modify subsequent exploitation of the resource. In this paper, a spatially-explicit model of vessel fishing behaviour is developed for a line fishery on the Great Barrier Reef, Australia. Vessel behaviour is conditioned on past catch and effort data at a spatial resolution of 6×6 nautical mile grid cells. For each vessel, the probability of fishing a particular grid cell is determined from past income per unit effort experienced at that location, and the cost of steaming to it. The probability distribution across all possible grid cells represents a particular vessel’s perspective. This perspective is modified by information conveyed by other vessels using Bayesian-network information propagation. The information conveyed is the effort distribution of other vessels and is equivalent to a vessel ‘watching’ where other vessels fish. We compare the behaviours that vessels display when they act independently with those they display when they ‘watch’ each other, and show the effect that such information flow can have on a resource. Information flow among fishing vessels can be shown to have an effect on the dynamics and resource exploitation of a simulated fishery.

Tropical fish otoliths : information for assessment, management and ecology

Techniques and theory for processing otoliths from tropical marine fish have developed only recently due to an historic misconception that these organisms could not be aged. Otoliths are the most commonly used structures from which daily, seasonal or annual records of a fish’s environmental history are inferred, and are also used as indicators of migration patterns, home range, spatial distribution, stock structure and life history events. A large proportion of projects undertaken on tropical marine organisms involve removal and processing of calcified structures such as otoliths, statoliths or vertebrae to retrieve biological, biochemical or genetic information. Current techniques and principles have evolved rapidly and are under constant modification and these differ among laboratories, and more particularly among species and within life history stages. Tropical fish otoliths: Information for assessment, management and ecology is a comprehensive description of the current status of knowledge about otoliths in the tropics. This book has contributions from leading experts in the field, encompasing a tropical perspective on daily and annual ageing in fish and invertebrates, microchemistry, interpreting otolith microstructure and using it to back-calculate life history events, and includes a treatise on the significance of validating periodicity in otoliths.

Regional patterns in reproductive biology of Lethrinus miniatus on the Great Barrier Reef

Uniformity in fish population biology is a common assumption in many fishery assessments and man- agement arrangements. Although spatial patterns in population biology are often unknown, ignorance of significant variation within a fished stock has profound implications for fishery assessments and management. In the current paper, the reproductive biology of an exploited reef fish, Lethrinus miniatus, was examined for populations in the northern and southern regions of the Great Barrier Reef (GBR). Significant regional variation was observed in some reproductive parameters, but not others. In the northern region, the proportion of spawning females observed during the spawning season was significantly greater and the size at sex change significantly smaller than in the southern region. However, the spawning season, age at sex change and sex ratios did not differ significantly between the northern and southern regions. Size and age at maturity could not be estimated from either of these regions, but an estimate was obtained from the Capricorn-Bunker region at the southern tip of the GBR. The observed regional patterns in reproductive biology of L. miniatus populations have important implications for specific management arrangements such as size limits and seasonal closures, and for fisheries management in general.

EVALUATING LARGE-SCALE EXPERIMENTAL DESIGNS FOR MANAGEMENT OF CORAL TROUT ON THE GREAT BARRIER REEF

While biological information about targeted species is considered necessary for managing fisheries, alone it has proved insufficient to successfully manage both fisheries and ecosystems. Controlled experimental manipulations of fishing effort is likely to be the best mechanism for empirically assessing the responses of targeted stocks, other reef organisms, and fishing practices to changes in fishing pressure. Line fishing is a major extractive industry on the Great Barrier Reef of Australia, which is a mosaic of nearly 3000 separate reefs spread over 15° of latitude and has high conservation value. Computer simulations of the population dynamics of the main target species, the common coral trout Plectropomus leopardus (Serranidae), based on recent field research were used to evaluate various designs for a large-scale experiment to examine aspects of the effects of line fishing in this region. The results indicated that large-scale experiments using whole coral reefs as units of experimental manipulation ...

Variation in the periodicity and timing of increment formation in red throat emperor (Lethrinus miniatus) otoliths

Marginal increment analysis was used to validate the periodicity of opaque increment formation in red throat emperor (Lethrinus miniatus) otoliths and to test for variation in the periodicity and timing of increment formation across age classes, years and regions of the Great Barrier Reef (GBR). Marginal increment analysis demonstrated that opaque increments were deposited on an annual basis, a result supported by a preliminary experiment on a chemically tagged captive fish, although significant regional and temporal variation in the timing of increment formation was observed. Marginal increment analysis revealed a clear annual periodicity in increment formation for all age classes in the southern region but a more ambiguous pattern for most age classes in the northern region of the species distribution on the GBR. Opaque increments appeared to form 1 month earlier in the southern region than in the northern region and, in the southern region, formed 2 months earlier in 1999 than in 2000. No significant variation was observed in the timing of increment formation between age classes. Based on knowledge of the timing of otolith increment formation and spawning season of L. miniatus, an algorithm was developed for the estimation of age in months, irrespective of the time or location of capture.

Complementarity of No-Take Marine Reserves and Individual Transferable Catch Quotas for Managing the Line Fishery of the Great Barrier Reef

Changes in the management of the fin fish fishery of the Great Barrier Reef motivated us to investigate the combined effects on economic returns and fish biomass of no-take areas and regulated total allowable catch allocated in the form of individual transferable quotas (such quotas apportion the total allowable catch as fishing rights and permits the buying and selling of these rights among fishers). We built a spatially explicit biological and economic model of the fishery to analyze the trade-offs between maintaining given levels of fish biomass and the net financial returns from fishing under different management regimes. Results of the scenarios we modeled suggested that a decrease in total allowable catch at high levels of harvest either increased net returns or lowered them only slightly, but increased biomass by up to 10% for a wide range of reserve sizes and an increase in the reserve area from none to 16% did not greatly change net returns at any catch level. Thus, catch shares and no-take reserves can be complementary and when these methods are used jointly they promote lower total allowable catches when harvest is relatively high and encourage larger no-take areas when they are small.

Scalable Decision Criteria for Environmental Impact Assessment: Effect Size, Type I, and Type II Errors

Publisher Summary This chapter focuses on specific steps for evaluating critical levels of α and procedures for making decisions based on variable α c , and consideration of the probability of Type II error (β). It shows that variability also limits the power of statistical tests of impacts and Mapstone suggests a novel way to incorporate a constraint directly into the permitting process by simultaneously weighting Type I and Type II errors in assessment studies. The conventional decision making practices concerned with environmental impacts perpetuate an inherently one-sided perspective of “significance.” A well established convention of statistical decision making is a set of difficult inferential and epistemological problems with real, tangible implications. The chapter discusses the procedures providing a mechanism through which the burden of limitations is shared between potential environmental assailant and environmental defender instead of being borne only by the latter.

Spatial variation in the effects of size and age on reproductive dynamics of common coral trout Plectropomus leopardus.

The effects of size and age on reproductive dynamics of common coral trout Plectropomus leopardus populations were compared between coral reefs open or closed (no-take marine reserves) to fishing and among four geographic regions of the Great Barrier Reef (GBR), Australia. The specific reproductive metrics investigated were the sex ratio, the proportion of vitellogenic females and the spawning fraction of local populations. Sex ratios became increasingly male biased with length and age, as expected for a protogyne, but were more male biased in southern regions of the GBR (Mackay and Storm Cay) than in northern regions (Lizard Island and Townsville) across all lengths and ages. The proportion of vitellogenic females also increased with length and age. Female P. leopardus were capable of daily spawning during the spawning season, but on average spawned every 4·3 days. Mature females spawned most frequently on Townsville reserve reefs (every 2·3 days) and Lizard Island fished reefs (every 3·2 days). Females on Mackay reefs open to fishing showed no evidence of spawning over 4 years of sampling, while females on reserve reefs spawned only once every 2-3 months. No effect of length on spawning frequency was detected. Spawning frequency increased with age on Lizard Island fished reefs, declined with age on Storm Cay fished reefs, and declined with age on reserve reefs in all regions. It is hypothesized that the variation in P. leopardus sex ratios and spawning frequency among GBR regions is primarily driven by water temperature, while no-take management zones influence spawning frequency depending on the region in which the reserve is located. Male bias and lack of spawning activity on southern GBR, where densities of adult P. leopardus are highest, suggest that recruits may be supplied from central or northern GBR. Significant regional variation in reproductive traits suggests that a regional approach to management of P. leopardus is appropriate and highlights the need for considering spatial variation in reproduction where reserves are used as fishery or conservation management tools.