Research

The new PAL (pat.) developed by F3: Maritime Technology UG (Ltd.) can generate a variety of acoustic signals.

The Whale-PAL (pat.) generates an acoustic signal in the range of 10 – 130 kHz every 4 seconds and also has a variable secondary signal that is emitted randomly to prevent the animals from getting used to it. This successfully distracts killer whales from attacks on sailing yachts or drives them away. Feedback from 150 customers shows that the probability of getting through the "Orca Alley" unscathed increases to 98.2%. The whale PAL reduces the probability of damage from 11% to just 1.8%, a reduction of 85%. (See “Orca Attacks”).

The Porpoise-PAL produces lifelike porpoise communication signals. It alerts the animals to dangers in their environment using their own language by stimulating echolocation. Independently tested by the Thünen-Institute of Baltic Sea Fisheries, Rostock with the co-operation of German and Danish gillnet fishermen. By-catch reduction in the Western Baltic Sea reaches 80% (Chladek et al. 2020; Fish Res).

The Wideband-PAL produces another type of acoustic signal. It was tested in Icelandic and Bulgarian fisheries where it  reduced bycatch significantly by 60-100 % (partners Iceland and Bulgaria).

NEW feature: every PAL can now also support monitoring tasks by recording on board (optional) total time, total deployment time, and in fixed intervals temperature and signal generation.

By-catch

Far too many marine mammals are caught inadvertently in nets because they do not detect these threats in time. The animals drown because they can no longer surface to breathe. Overall, the bycatch rate of porpoises in the Baltic Sea should not exceed 1% of the total population. This is often not the case however, as much larger ranges between 2.6 to 4.8% have been seen.

The reasons for this are manifold: the water is murky and the nets are poorly visible. And although toothed whales produce clicks like bats to orient themselves with their biosonar, the fine nylon twines of the nets reflect only a weak echo at close range. Furthermore the animals are frequently distracted by feeding or interactions with other porpoises, or they remain silent to listen, or to avoid potential enemies like dolphins.

In fisheries, the Porpoise-PAL now allows the use of a species-specific warning signal to avoid bycatch. Its ultrasonic signals don't drive the animals out of their habitat and  cannot be heard by fish and most marine animals.
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Small cetacean drowned as by-catch in a gillnet. Source: Thünen Institute of Baltic Sea Fisheries

PAL fishery trials

The Porpoise-PAL was tested between 2014 and 2016 by the Thünen Institute for Baltic Sea Fisheries, Rostock, by professional Danish and German fishermen. During these tests, the device successfully contributed to bycatch reduction in the western Baltic Sea (Chladek et al. 2020; Fish Res). There was no effect on the catch of target species and no interactions with seals were observed.

In each experiment, two equally long net strings were deployed in parallel. Only one string was equipped with PAL (spacing 180-200m), the other, conventional string served as control. Altogether 4,350 km of nets were deployed by the three participating fishers in over 752 trials. In total, 19 porpoises were bycaught: 16 in nets without the warning devices but only 3 in PAL-nets. The modelled by-catch reduction of 80% is statistically significant and shows that the Porpoise-PAL successfully reduces bycatch.
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By-catches in fishery experiments in the Western Baltic Sea. Red: standard-nets, Green: PAL-nets. Source: Thünen Institute of Baltic Sea Fisheries

Reactions of harbor porpoises to PAL

During field-tests in the Danish Belt Sea, we investigated how porpoises react to the sounds of the Porpoise-PAL compared to a conventional wide-band pinger. We fitted 5 buoys with acoustic recording devices and placed each 100 meters from the next buoy. The sound source was attached to buoy 3. Porpoise behaviour was recorded from a cliff with a theodolite.

During PAL deployment, porpoises increased their click activity near buoy 3 where the PAL was attached (blue line). Their click activity during PAL-exposure was twice as high as compared to a standard wide band pinger (red line).
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Echolocation activity (click counts per 10 min) of wild harbour porpoises. Sound source mounted at buoy 3. PAL (blue). Standard pinger (red).
The porpoise-PAL apparently increases popoise awareness. It does not act as a deterrent: the distance of the animals to buoy 3 was only slightly higher than to the other buoys. Presumably, PAL enhances porpoises to acoustically detect the deadly nets early enough to be able to avoid entanglement. Other changes in behaviour which would reduce the risk of collision near PAL, like the strong avoidance reaction observed with pingers, do not seem to play a role.

PAL deployment

Since spring 2017, the Baltic Sea Infocenter in Eckernförde is deploying over 2,600 Porpoise-PAL in a validation and testing study together with fishers in Schleswig-Holstein. Further east, in Mecklenburg-Vorpommern, as well as in Danish and Swedish areas of the Baltic Sea, the wideband-PAL could contribute to reducing porpoise bycatch.

Based on the PAL hardware, F3: Maritime Technology UG (ltd.) also offers PAL with standard EU and USA-approved pinger (Regulation (EU) 2020/967). All devices are programmable and can be adapted in the factory for their respective application area. PAL is designed, manufactured and tested in Germany.

If you have any questions regarding PAL, its deployment, effect and use, please check the FAQ section here or feel free to contact us if you need any further assistance.

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