The receivers catch signals from a circular baseline set between the pinger and the underwater hydrophone. The baseline must be longer than twice the receiver’s depth of response, anything shorter than that will not work. The baseline should be linear to provide the greatest signal-to-noise ratio. The larger the baseline, the higher the range of the pinger signals. There is a trade-off between resolution (bearing ability) and range. The greater the bearing ability, the higher the range.
Modifications and the addition of swivels and stern-mounted systems have allowed pinger equipment to continue to operate effectively for several decades, commonly through ice, seasons, storms and other conditions (Fishtek 2014). High tide should not interfere.
The author has no explanation for why the salmon, the second largest species in the world, can be so much more adept at reproducing than other fisheries which participate in the herring fishery. But it makes sense that a fishery like the herring, which is highly vulnerable to increasing net widths, would become fully mechanised, and large scale open-net reductions in standing stocks are likely to have been the driving force. In any event, the salmon fishery is less of a regional or global problem than the herring fishery. d2c66b5586