Effective Detection Distance Research Articles

Evaluating the effectiveness of SCUBA-based visual searches for an invasive tunicate, Ciona intestinalis, in a Prince Edward Island estuary

Visual searches are a common method of detecting invasive species in coastal waters, but the statist ical properties of search methods have rarely been evaluated. Understanding the error rate (especially false negatives) and effective detection distance of searches can improve survey design, and quantify the uncertainty in risk assessments used to inform invasive species management efforts. An experiment using artificial tunicates (“decoys”) was conducted in Hillsborough Bay, Prince Edward Island, to determine the effectiveness of SCUBA divers conducting underwater visual searches for the vase tu nicate, Ciona intestinalis (Linnaeus, 1767). Single decoys and clusters of three decoys, constructed from water -filled, ivory-coloured balloons 5-6 cm in length, were placed at a blue mussel, Mytilus edulis (Linnaeus, 1758), aquaculture site on buoys, lines and mussel socks. The probability of detecting tunicate decoys on a mussel sock in the experiment is 89.8% (±SD 7.1), known in this paper as a true positive. The probability of not detecting tunicate decoys actually placed on a mussel sock in the experiment is 10.2% (±SD 7.1), known in this paper as a false negative. Divers detected 79.2% (±SD 7.1) of single decoys and 94.0% (±11.4) of clusters. Divers were able to detect single decoys from a measured horizontal distance of 2.7 m (±0.8), and clusters from 2.8 m (±0.9). The typical detection distance for real C. intestinalis estimated by divers was, on average, 2.1 m (range 1 - 3 m), and tunicates of lengths ≥ 2.9 cm (range 1-4 cm) could be detected.

A New Leak Detection System for Long‐Distance Pipelines Utilizing Soil‐Gas Techniques

AbstractThis paper presents a new leak detection system for a long‐distance pipeline using soil‐gas techniques. The new leak detection system runs underground along the nearby pipeline and consists of intermittent porous tubes connected in series with impermeable polyethylene tubes. Applying the new detection system to long‐distance pipelines for leak detection minimizes the large number of soil‐gas samples and analyses that are required when conventional soil‐gas probes are employed. A mathematical model was developed for designing the distribution of airflow in the new detection system. Field leak tests were conducted using both conventional soil‐gas probes and the new system. Results indicated that the effective detection distance of the new system was at least 30 m, while the effective detection radius from the conventional soil‐gas probes is only ∼5 m.

A Feasibility Study on the Use of Vocalizations of Wild Macaque Troops to Determine Location

We investigated the possibility of detecting wild Japanese macaque troop locations based on their vocalizations on Yakushima Island, a typical habitat of this species, in order to design adequate census methods and observe wild monkeys more efficiently. For each category of vocalizations we determined the maximum distance between the observers and the vocalizing monkeys. Trackers and fixed-point observers determined the actual real-time location of the vocalizing monkeys. ”Loud calls” and ”loud screams” could travel the farthest distance and were most suitable for obtaining precise directional estimation on the position of the troop. The maximum distance from which ”loud calls” were heard was 580m, and that for the ”loud screams” was 420m. However, it was concluded that when conducting censuses by using vocal cues in steep terrain like on Yakushima Island, the frequencies of these two vocalizations might sometimes be too low to conduct a census efficiently. Thus, we recommend that a more effective detection distance should be less than 200m, which is close enough to hear the next long-distance transmittable vocalizations such as ”loud aggressive vocalization” and ”loud alarm calls.” Although loud alarm calls were less precise when determining the direction from which the voice came, they were more practical for large-scale census methods.

A Variable Circular-Plot Method for Estimating Bird Numbers

A Variable Circular-Plot Method for Estimating Bird Numbers