Two captive harbor porpoises were exposed to three sound types (frequency from 100 kHz to 140 kHz, 200 ms long, and presented once per 4 s). Each session consisted of a 10 min period persound, a 5 min period of sound, and a 10 min period after the sound. Behavior was recorded on video and with dataloggers. Animals reacted most to the intial presentations of sound, but the reactinos diminished rapidly in repeated sessions.
A field test was conducted to test whether harbor porpoises habitutate to pingers over time. Echolocation and movements were monitored around a mooring equipped with a pinger (Dukane Netmark 1000) for 3 months. Initial displacement was 208 m from the pinger, but it diminished by 50% within 4 days. Echolocation rate and occurrence were significantly reduced near the pinger.
The Hawaii longline swordfish fishery reduced seabird captures through mitigating bycatch during setting. Now, 75% of bycatch occurs during hauling. Observer data was fit to a generalized additive regression model and found that density of albatrosses during hauling, leader length, and year had the largest model effects. Heavier swivels, greater than 65g, had significantly fewer catch rates for seabirds. However, heavier weights with longer leaders had reduced effects.