4.0 Maintenance and troubleshooting
Acoustic pinger
Gillnets are hauled in a variety of ways. Whatever the setting and haul-back techniques, a lot of pinger breakage or failure seems to occur due to stresses from being wound tightly during hauling -- if they don't break like an egg, the stress distorts the O-ring seal and the pinger subsequently leaks. To prevent this, the ends of the pinger can't be tightly secured to the net-frame -- there has to be some "give" there.
Pingers themselves withstand hard impacts incurred during the "set-out" procedure. Nets with pingers can be set-out at full speed over the stern or side of the fishing vessel. However, the battery cartridges will often break or distort inside the pinger due to the pounding (on the ends), and the batteries jar loose. To avoid these problems, the pingers can be placed on the net as it is set. In this way the pingers are stored off the net in between sets, allowing easy battery changes and maintenance.
Pingers should be checked regularly for sound output. Some will leak -- it causes an ugly black sludge in the pinger cavity. Rinse the pingers in warm soapy water and use a small soft-bristled tooth brush to clean around the contacts. This can rehabilitate about 50% of problematic pingers.
Silicone grease should be applied to the O-rings periodically to maintain their performance.
Expect attrition. Buy more pingers than you need.