Predefined Reference Points Research Articles

The Precautionary approach to fisheries management: How this is taken into account by Tuna regional fisheries management organisations (RFMOs)

For several decades it has been acknowledged that there is an urgent need for new approaches to fisheries management, embracing conservation and environmental considerations. The voluntary Code of Conduct on Responsible Fishing and the United Nations Fish Stocks Agreement provide the formal basis for the Precautionary Approach to fisheries management. Some tuna Regional Fisheries Management Organisations such as the WCPFC and IATTC make explicit mention of these codes in their conventions, whilst others, whose conventions do not explicitly address the Precautionary Approach, are searching for ways in which to take these codes into consideration. In practical terms, the scientific obligations to Precautionary Approaches are to determine the status of the stock(s) relative to limit and target reference points, to predict outcomes of management alternatives for reaching the targets and avoiding the limits, and to characterise the uncertainty in both cases. A convenient framework to conduct management evaluations is through the use of harvest control rules, for which managers agree on specific management actions under their control which are evoked according to levels of stock status relative to predefined reference points. These pre-agreed management actions are then simulated for a range of scenarios. This paper presents the ways in which tuna RFMOs are currently incorporating the precautionary approach in their fisheries management as well as suggestions for possible best practice. ► A review of the meaning and implications of the PA to fisheries management is conducted. ► The application of the PA within tRFMOs is comprehensively investigated and described. ► The PA as applied by tRFMOs is compared with its application in non-tuna RFMOs. ► Problems with applying the precautionary approach are highlighted. ► Suggestions and recommendations are made regarding best practice for applying the PA.

On the Practical Consideration of Source Localization Using the Location Template Matching (LTM) with Multiple Sensors

The Location Template Matching (LTM) method is known to be simple and straightforward to use for source localization problem. We have found that the method is not as simple as one might think, but there are many practical aspects that must be carefully considered. The most important parameter is the spatial resolution of the pre-defined reference points. The other parameters are the sampling rate, the time alignment between the signals, the frequency bandwidth of a signal, and the length of data. It is also shown that the accuracy of the LTM method can be improved if a couple of more sensors are used. This paper discusses these practical considerations in detail for the purpose of providing a proper guidance of using the LTM method.

Review of Institutional Arrangements and Evaluation of Factors Associated with Successful Stock Recovery Plans

We review the development and success of fish stock recovery plans in the United States, Australia, New Zealand, and Europe. A range of multi-disciplinary factors that have been associated with successful stock recovery were evaluated for 33 case studies. Each factor was assessed and scored based on the best available information to indicate its relative importance in the overall process leading to stock recovery. The results showed that rapid and often large reductions in catches at the start of the recovery process, and biological characteristics such as the life history strategies of species and the demographic composition of the stock, played a key role in the ability of populations to recover. Although the latter cannot be controlled directly by human intervention, they should be used to inform the management process and set appropriate levels of exploitation through a set of harvest control rules. Recovery is more effective when the recovery plan is part of a legal mandate, which is automatically triggered on reaching pre-defined limit reference points. Of the four regions studied, the United States was the only country to have a legal framework within which clear guidelines are given to establish a recovery process within a pre-defined time period.

Spatial Reproducibility of the Ring and Tandem High-Dose Rate Cervix Applicator

Purpose: High-dose rate (HDR) applicators for uterine cervix brachytherapy are used with increasing frequency. Because multiple HDR fractions are required for treatment, the applicator position reproducibility is of most importance. To study this effect, the clinical data from patients with uterine cervix cancer were examined retrospectively to evaluate the interfraction geometric variation of the HDR applicator and its potential treatment impact. Methods and Materials: Eighteen patients with invasive cervical cancer who were treated with definitive radiotherapy at William Beaumont Hospital were included in the study. Patients were treated with 45–50.4 Gy megavoltage external beam to the pelvis, and 35 Gy to the prescription point A from 7 fractions of HDR brachytherapy. The 3-dimensional (3D) interfraction geometrical variation of the ring and tandem (R & T) applicator was measured using predefined reference points in the 7 sets of orthogonal simulation films obtained prior to each HDR application. Spatial reproducibility of the R & T insertion and time-trend of the R & T position variation related to patient’s anatomy during the treatment course were analyzed with respect to different groups of patients who had either early or advanced disease. Results: The translational variation of the applicator position for all patients was 6.5, 5.9, and 7.7 mm (one standard deviation), respectively, in the patient’s superior-to-inferior (SI), right-to-left lateral (RL), and anterior-to-posterior (AP) direction. The rotational variation was 3.4, 4.6, and 6.0 degrees (one standard deviation) in the patient’s coronal, transverse, and sagital planes. When the patients were grouped based on early disease or advanced disease, the latter demonstrated substantially larger variation (factor of 2) in the applicator position than the former. Furthermore, the time-trend of position variation was observable for both groups of patients. The variations occurred primarily during the first 3 fractions. Conclusions: Based on the good spatial reproducibility observed in our study, the current clinical procedure for the HDR R & T applicator placement is reliable. Positional reproducibility of the R & T applicator is highly dependent upon the size of tumor volume, which, in turn, deviates the applicator during the early course of HDR brachytherapy. Attention to the construction of the midline block is of paramount importance.

Methods of reducing observer variation in age estimation from panoramic radiographs.

To compare inter- and intra-observer variation in age estimation using subjective and objective methods. Fifty-six panoramic radiographs of patients aged 13 to 25 years were assessed subjectively twice by four observers for the stage of root development of the lower third molars on a seven-point scale. Two of the observers were calibrated before the first evaluation, and the other two before the second. The same observers also digitized predefined reference points in a subsample of the third molars ten times by means of a computer-based digitizer system. Observer variation in classifying different root stages and in digitizing coordinates and measuring root lengths were studied. Significant systematic differences existed between two of the observers in the subjective assessment. One non-pre-calibrated observer changed her pattern most. Scattergrams from the digitizer measurements showed a good precision within and between observers with no significant differences in calculating root lengths. When, however, the teeth were analysed separately, some significant differences were found. The overall observer agreement was best using the objective method on several teeth. With only one tooth there were some significant differences. Subjective evaluation was improved by prior calibration.