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Authors investigated the spatial and temporal responses of harbor porpoises (Phocoena phocoena) to simulated bottom-set nets equipped with periodically operating Dukane NetMark 1000 pingers. Pinger sound significantly reduced the median echolocation encounter rate by 50-100% at detectors placed up to 500m and reduced the sighting rate up to 375m from the simulated net. The average distance of approach also increased. When pingers were silent after being active for about two days, the return time of porpoises increased by several hours in comparison to a control. After about 50 days, habituation to the pingers was detected at two of nine stations. Pingers may affect harbor porpoises at greater distances than previously observed, but alternative solutions should be applied in ecologically important habitats and migration routes. 

Fisheries observers and skippers tested the effectiveness of the Dolphin Dissuasive Device (DDD) as a bycatch mitigation tool for porpoises and dolphins. This study was conducted aboard fishing vessels in the Cornish over-12m static net sector fishery in the waters of Southwest England. DDD's were placed at the end nets. The DDD's caught significantly fewer porpoises but no significant difference in dolphin bycatch was observed. When bycatch rates were separated between short (up to 4 km) fleets and long (larger than 4 km) fleets, there was no significant difference in porpoise bycatch in the long fleet but there was in the short fleet. 

Tests were conducted aboard small (<10 m long) static net fishing vessels targeting monkfish off the coast of Britain to determine the response of cetaceans to pingers.  AQUAmark 100 pingers were positioned at 200 m intervals on the net and acoustic click detectors (C-PODs) were placed at the end of 1 km tiers of the net to determine the response of cetaceans to the pingers.  Only one harbour porpoise was incidentally caught during these trials and there was a significant reduction in the number of porpoise clicks recorded at nets with pingers compared to those without.  Additional tests were conducted to determine habituation.  For these tests, modified pingers, active for alternate seven hour periods, were attached below click detectors at one site with strong tides and loud ambient noise and one at a quite site.  The results of this part of the study showed the pinger effect was stronger at the quiet site and that were was no habituation.  In addition, there was evidence of exclusion of porpoises following pinger use for as much as seven hours.

A study was conducted aboard the Cornish inshore gillnet fishery to determine if pingers could reduce porpoise and bottlenose dolphin bycatch, whether habituation to the pingers would reduce their effectiveness and how quickly porpoises and dolphins recolonise a pingered site after their removal. Vessels were equipped with passive acoustic monitoring systems that can recognize and log each animals click and AQUAmark 100 pingers were spaced 200 m apart on the nets.  Control nets with no pingers were also used.  There was a significant difference in the number of porpoise clicks between nets with and without pingers.  There was no significant difference in the proportion of loud clicks logged when pingers were active and so the extent of displacement by pingers cannot be determined. In addition, there was no evidence of habituation to the pingers.  It appears that porpoises take at least 7 hours to recolonise a pingered site. There were too few encounters with dolphins to determine the ability of pingers to reduce their bycatch or to determine how long recolonization will take.

Experiments were carried out aboard vessels in the Danish North Sea hake gillnet fishery to determine if increasing the spacing of Aqutec AQUAmark100 pingers could be done without negatively impacting the effectiveness of the pinger. Control nets without pingers were tested alongside nets with pingers spaced at 455 m and 585 m. The control nets had a bycatch frequency of 0.54 incidents/haul for harbour porpoises. Nets with pingers spaced at 455 m had an incidence rate of 0 and nets with pingers spaced at 585 m had a bycatch frequency rate of 0.12. Bycatch indences were significantly different between the control and two experimental groups. This suggests that the spacing of pingers may be increased without significantly impacting their ability to reduce bycatch of harbour porpoises. 

Two porpoises were subjected to 3 different underwater sounds (standard Dukane alarm, random Dukane alarm, and a "bird alarm") in a enclosed floating pen. Their behavior during a 15 min test period was compared to behavior during a baseline 15 min period before the test and a recovery period after the test. All alarms resulted in increases in both the distance of the animals' surfacings from the alarms and their respiration rates. The standard Dukane alarm and the bird alarm were more effective than the random alarm in inducing animals to swim away from the source. 

Two captive harbor porpoises (Phocoena phocoena) 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 per sound, 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 initial presentations of sound, but the reactions 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. 

A study was conducted on observed interactions between a Portuguese purse-seine fishery and cetaceans. Cetaceans, primarily common dolphins (Delphinus delphis), were present during 16.9% of fishing events. The majority of these occurrences happened during the summer and early fall, and during the night. The presence of cetaceans was significantly linked to sardine catches, effort and latitude/longitude. Encirclement of cetaceans occurred in 2.3% of fishing events, with moralities occurring in 1%. Common dolphin, bottlenose dolphin (Tursiops truncatus) and harbor porpoise (Phocoena phocoena) were all encircled, with moralities only recorded for common dolphins. Estimated annual mortality rates for the common dolphin are 113 individuals.

A spatially and temporally explicit Productivity and Susceptibility Analysis (PSA) was developed to screen cetacean species for bycatch risk. This PSA can be included under Ecosystem Based Fisheries Management (EBFM). The potential risk to harbor porpoises (Phocoena phocoena) and minke whales (Balaenoptera acutorostrata) from static fishing gear was investigated. Harbor porpoises had a low- to moderate- biological risk from bycatch compared to other cetacean species. Minke whales are less productive than harbor porpoises but also have a low to moderate biological risk to bycatch. The results suggested that high, low and moderate risk areas can all exist within the range of individual fisheries (gillnet, longline, pots). Therefore, management measures can focus on areas of the greatest risk to these species. EBFM can complement and support current management measures.