David C. Smith

An Integrated System for Production Fish Aging: Image Analysis and Quality Assurance

Abstract There is an increasing demand for aging data to provide inputs to stock assessment models for management of exploited fish populations. Image analysis software and computer hardware allow more rapid processing of samples and data. This paper describes a fully integrated system that has been in operation for 5 years and has been used to provide age estimates for more than 150 species. The system combines the requirements of high-quality “production” aging with the benefits of a customized image analysis system. The system improves the work environment, increases efficiency, aids data collection, and improves quality control. All aging studies require unbiased and precise age estimates; however, the ongoing process of production aging has particular requirements for quality assurance. A classification of aging studies is proposed based on objectives of the study, and the features and key procedural requirements of each study type are described.

Stock assessment of the blue grenadier Macruronus novaezelandiae resource off south-eastern Australia

The fishery can be divided into two subfisheries (‘spawning’ and ‘non-spawning’). Commercial catch rates for the ‘non-spawning’ subfishery declined from the late 1980s to 1997, whereas those for the ‘spawning’ subfishery exhibit no obvious temporal trend. An ‘Integrated Analysis’ assessment, of the feasibility of reconciling these differing trends, uses catch (landed and discarded), catch rate, length-at-age, and catch-at-age data and estimates of absolute abundance based on the egg-production method. It emphasizes uncertainty due to model assumptions and the data included in the assessment. Use of the discard data allows more precise estimation of the magnitude of recent recruitments. Spawning biomass is estimated to have declined from a peak in 1989–91 to 1999 although fishing mortality has consistently been <6%for each subfishery. One main reason for the reduction in population size is the weakness of year-classes spawned from 1988 to 1993. Differences in catch rates between the two subfisheries can therefore be explained by interactions between the components of the population harvested by the two ‘subfisheries’, and the trends in year-class strength. A risk analysis is used to evaluate the consequences of different future levels of harvest for different assessment assumptions. Overall, the spawning biomass is predicted to increase over the next five to ten years as a result of the strong 1994 and 1995 year-classes, although the extent of this increase remains uncertain.

Quantifying age-reading error for use in fisheries stock assessments, with application to species in Australia’s southern and eastern scalefish and shark fishery

Age-reading error occurs when estimates of age based on reading hard structures differ from the true age of the animal concerned. This error needs to be accounted for when conducting stock assessments. Common methods for quantifying age-reading error include the average percent error, the coefficient of variation, age bias plots, and age difference tables, but these techniques cannot be used to construct age-reading error matrices. A method for constructing age-reading error matrices that accounts for both ageing bias and ageing imprecision is outlined. Simulation evaluation of this method suggests that it is able to estimate both ageing bias (assuming that one reader is unbiased) and ageing imprecision for relatively large sample sizes and for the ages that constitute the bulk of the ages in the sample. However, the performance of the method is poor when sample sizes are small, age-reading error is correlated among readers, when both readers are biased, and for ages that are poorly represented in the sam...

Fitness to fly for passengers with cardiovascular disease.

Following this review of evidence and after due consideration, it is clear that there are few cardiovascular conditions that warrant the denial of fitness to fly as a passenger. Given the right aircraft, on-board equipment and appropriately qualified and experienced escort personnel, aircraft can act as flying intensive care units and carry extremely ill passengers.1 For those with cardiovascular disease who are not critically ill but who wish to fly on commercial aircraft, the aircraft environment does not pose a significant threat to their health. It is only when their underlying condition is associated with a significant risk of acute deterioration that reasonable restrictions should apply. For those at the more severe end of the spectrum of their specific cardiovascular condition, services exist to help make the journey more easily and safely. Most carriers and airport authorities provide assistance on the ground and in the air. Oxygen is available on most major carriers, although this is sometimes subject to a charge and at least 7 days notice is normally required.2 Passengers are advised to plan their arrival at the airport in plenty of time to avoid having to rush and to warn the carrier and/or airport authority of any requirements for assistance, including requirement for in-flight oxygen, well in advance of the date of departure. They are strongly advised to ensure they have an appropriate supply of their medication, a clear list of the medications and doses they take and a letter of explanation from their doctor regarding their condition, drugs, allergies and devices (eg, pacemaker). Physicians are advised to consider the stability of a passengers condition and apply the guidance herein. The authors have contributed to this document in good faith and consider it to be an honest conclusion of the review of evidence and assessment of the …

Modelling the effects of Marine Protected Areas (MPAs) on the southern rock lobster (Jasus edwardsii) fishery of Victoria, Australia

Abstract Since 2002, 5.3% of the Victorian coastal waters have been declared as Marine Protected Areas (MPAs). These are aimed at safeguarding important marine habitats and species, significant natural features, and areas of cultural heritage and aesthetic value. However, MPAs impact the fishery for southern rock lobster (Jasus edwardsii), as total allowable catches (TACs) were previously set to allow the biomass to recover to pre‐specified target levels. The model on which assessments and risk analyses are based is extended to include the impact of MPAs. The MPAs and the area open to fishing are modelled as subpopulations with different levels of mortality and consequently different density and population size‐structure. A range for the probability of a lobster moving from a MPA to the fished area from 0 to 15% is considered, based on the results of tagging studies. The reduction of biomass available to the commercial fishery because of the introduction of MPAs is estimated to be 8% and 16% (Western and Eastern Zones) respectively. The results of a risk assessment show that if the current TACs are maintained, the time to increase the biomass available to the commercial fishery by 50% would be delayed 5–9 years in the Western Zone and 1–4 years in the Eastern Zone because of the impact of displaced effort. In contrast, spawning biomass in the Eastern Zone is currently below the agreed limit reference point, and the introduction of MPAs would enhance the rate of recovery, although only marginally initially, faster than the absence of the MPAs.

A complex quota-managed fishery: science and management in Australia's South East Fishery. Introduction and overview

The stock assessment process in the South East Fishery involves scientists, industry, fishery managers, economists and non-government organizations. A comparison with such processes in other countries, where stakeholder involvement ranges from government scientists only to involvement of scientists, industry and conservation non-government organizations, suggests that Australia is the only country in which fishery managers are active and integral stock-assessment participants. In Australia, as in several other countries, the form of advice is comparative (consequences of alternative decisions) rather than prescriptive. Although all approaches have advantages and disadvantages, the South East Fishery process has advantages that appear to clearly outweigh the disadvantages. The advantages include better communication among interest groups, improved ownership of and hence support for outcomes and better interactions among groups. The disadvantages include the cost of the process, lack of consistency among assessments, vulnerability of scientists and the frustrations of industry.

Fishing for More Effective Incentives

In their Report “Can catch shares prevent fisheries collapse?” (19 September 2008, p. [1678][1]), C. Costello et al. present empirical evidence to support the view that providing incentives for fishers by allocating them shares in the catch [individual transferable quotas (ITQs)] can halt, or

Transferring patients for primary angioplasty

The success of fibrinolysis in the treatment of myocardial infarction has been attributed to reperfusion of the occluded vessel, however, it has become clear that it is not just reperfusion but restoration of normal flow—defined angiographically as TIMI-3 flow—in the infarct related artery that dictates mortality. Analysis of the different treatment arms of GUSTO-I,1 the PAMI trials,2 3 and the primary angioplasty registry,4 demonstrates a very clear inverse linear relation between mortality and the rate of TIMI-3 flow achieved in the infarct related artery. The randomised trials of primary angioplasty in acute infarction2 5 6 all point to it being superior to thrombolytic therapy in achieving this goal, although in the GUSTO-IIB substudy7 the benefit was less marked. The trials of thrombolytic therapy versus placebo all demonstrated a time dependent benefit, the shortest “pain to needle” times having the lowest mortality with a cut off at approximately six hours. This has led to Department of Health guidelines, frantic (albeit appropriate) efforts to keep door to needle times as short as possible, and …

Workshop on the ecosystem and fisheries of the Coral Sea: an Australian perspective on research and management

This report summarizes a workshop on the Coral Sea to determine key research findings and identify the research gaps needed to support sustainable management of a proposed Coral Sea Marine Reserve. Key research questions included determining the connectivity of apex predators with the broader southwest Pacific Ocean, and assessing the regions’ biodiversity in relation to seabed topography and oceanographic processes. The workshop concluded noting the importance of engaging surrounding countries in maintaining the sustainability and uniqueness of the Coral Sea.

Assessments of species in the Australian South East Fishery can be sensitive to the method used to convert from size-to age-composition data

Information about the age-structure of the catch is one of the primary inputs to many of the methods of stock assessment currently applied to SEF species. Two methods for calculating the catch-, mean length-, and mean mass-at-age matrices from the data collected from the fishery are outlined. These methods are illustrated by applying them to data for blue grenadier, Macruronus novaezelandiae, and eastern school whiting, Sillago flindersi. The assessment and risk analysis results for blue grenadier are highly sensitive to the choice of method, whereas those for eastern school whiting are not. It is recommended that a method that allows for inter-annual variation in mean length- and hence mass-at-age should be the standard for SEF stock assessments but that sensitivity to alternative methods needs to be examined routinely.