Unanswered Forum Topics

Integrated weight longlines (IW) were tested for their ability to reduce sea bird bycatch in demersal longline fisheries. The target fishery for testing was the Pacific cod fishery operating in the Bering Sea, Alaska, USA. Three experimental mitigation techniques were tested: 1) IW line alone, 2) IW paired with streamer lines (IWPS) and 3) unweighted longlines with paired streamer (UWPS) against a control (UW). Information on catch rates, seabird abundance and attack rate, and gear sink rate and performance were collected.

Interactions between vertical lines under increased tension with a physical model of a North Atlantic right whale flipper was investigated. This was an updated experiment. The original flipper model was based on data (flipper outlines and bone measurements) collected from three different whales. The physical flipper was computer generated from these data and covered with 1/2 in neoprene rubber, which was overlayed with 1/8 in thick vinyl rubber sheeting. The flipper was made from fiberglass, was free flooding and covered with 1/2 in neoprene and then with 1/8 in vinyl-rubber.

This study investigated whether North Atlantic right whale behavior changes, in terms of response distance, to changing visual characteristics of rope mimics in their path. 20 ft rope mimics were made from two 10 ft sections of rigid PVC pipe, with an approximate diameter of 1 inch. The rope mimics were weighted and attached to a lobster buoy to simulate a vertical line in the water column. A 30.5 cm disk was placed around the rope for reference use in video footage. The following color ropes were used: black, green, two types of white (white and glow in the dark), orange and red.

Low-powered sound sources were tested for their ability to deter gray whales from potentially harmful areas. An acoustic device (1-s frequency modulated 1-3 kHz warble deterrent signal) was moored to the seafloor in the gray whales migration path off central Oregon. Observers (land based) tracked whales with a theodolite to locate whales as they passed the headland. Tracklines were compared between times when the acoustic deterrent was on and off.