No abstract

A telemetry system designed to automatically record the presence and swimming direction of fish tagged with coded acoustic transmitters is described. The present paper presents results from an extensive mapping of signal strengths and the proportion of correctly identified codes from a transmitter at various positions outside automatic listening stations (ALS). The system is evaluated on the basis of two field seasons, during which 107 Atlantic salmon, Salmo salar L., were tagged with acoustic transmitters in a fjord system in south‐western Norway. By installing one ALS (two at high water discharges) in the mouth of the River Suldalslågen and two ALSs in the Hylsfjord, the presence and swimming direction of all tagged salmon entering the river and the inner part of the 750‐m‐wide Hylsfjord were recorded.

No abstract

In ice frequented regions, the potential for large ice floes and extreme ice features encroaching on offshore structures can be significant. An early warning system is desired to discriminate between thin ice of no risk and thick ice with significant challenge. The severity and variability of ice conditions will affect the feasibility of operating in such a region, with significant impact on the design and selection of resources to be used and the ice management requirements to support exploration and development. By measuring the ice thickness, operators can determine the operational risk for ice management operations. In addition, it can help map the areas of thin ice to aid shipping route selection. Despite its fundamental importance, sea ice thickness is one of the most difficult measurements to obtain via remote sensing. Passive remote sensing methods at the near infrared, thermal infrared and visible electromagnetic wavelengths, are restricted due to fog, precipitation, clouds, and Polar darkness. Thus active sensing techniques are deemed to be the only feasible method of measuring ice thickness, especially if they can be mounted in aircraft or satellites. Technical solutions are available to measure the thickness of sea ice, but they do not provide a physical measurement over a wide swath of ice. Thus, the authors are developing a wide swath ice thickness measurement system to fill this gap. The most practical solution for ice thickness measurement is an airborne radar. The authors have completed the preliminary design of a system that will combine an ice penetrating radar with a microwave synthetic aperture radar (SAR). The penetrating radar will be used to glean physical measurements of ice thickness, to be fused with the wide swath SAR to produce an ice thickness map.