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Short-term behavioral responses of Chilean dolphins (Cephalorhynchus eutropia) to acoustic alarms, or pingers, were tested using exposure-control experiments (pinger on/off treatments). Field trials were conducted in the south-eastern Chiloe Archipelago between February and April of 2013. BananaBP154 pingers (FishTek Marine) were used for the tests. Static passive acoustic monitoring (PAM) techniques were used at two sites (Bahia Yaldad and Canal San Pedro) and land-based observations, which included theodolite tracking, were also conducted at Bahia Yaldad. Static PAM techniques and C-PODs were used to determine the effects of a single pinger on echolocation rates and movement patterns. Fifty seven groups of Chilean dolphins were tracked with the theolodite, with 45 groups providing good resolution movement data within the vicinity of the pinger. Visual data are currently being analyzed to determine effects of a single acoustic alarm on movement patterns, grouping behavior and spatial area use of the dolphins. Acoustic encounter rates of Chilean dolphins at the six C-PODs are currently being analyzed. Preliminary analysis suggest pingers are unlikely to have caused substantial behavioral changes in Chilean dolphins.

Fishery data collected from the Reunion Island and Seychelles pelagic longline fisheries (targeting swordfish and tuna) between 2004 and 2015 was used to propose depredation indicators and to assess depredation levels in these fisheries. The interaction rate (depredation) was significantly higher for sharks compared to toothed whales in both fisheries. However, there was a higher depredation per unit effort from toothed whales compared to sharks indicating the impact was more significant. The gross depredation rate in the Seychelles fishery was 18.3%. A slight increase in the gross depredation rate was seen over time in the Reunion Islands fishery (4.1% 2007-2010 and 4.4% in 2011-2015). These indicators were used to estimate the economic loss to these fisheries from depredation events. For the Reunion Island fishery the economic loss was 0.09 EUR/hook and 0.86 EUR/hook for the Seychelles. The results suggest a southward decreasing tooth whale and shark depredation gradient. The depredation levels in the Seychelles are some of the highest in the world and may suggest a 'hot spot' of interactions between toothed whales and pelagic longlines.

This research examined the spatial and temporal characteristics of pilot whale (Globicephala macrorhynchus) habitat use and longline fishing effort in the Mid-Atlantic Bight (United States). The information was used to assess the potential for a spatial management approach to mitigate pilot whale bycatch. The Area Under the Curve and Williamson's Spatial Overlap Index were both used to assess patterns of overlap and bycatch by applying them to telemetry data from short-finned pilot whales, longline fishery effort and Pelagic Observer Program (POP) data (2014-2015). Based on this analysis, important variables influencing pilot whale-longline overlap and POP bycatch rates include: proximity to the 1000 m isobath, season, and sea surface temperature. Pilot whales had the highest density inshore of the 1000 m isobath. Longline effort along this isobath varies seasonally. Seasonal patterns in pilot whale-longline overlap relative to the 1000 m isobath were significantly correlated with POP bycatch rates, with the highest bycatch rates occurring in the fall and winter months. Based on these results, the authors suggest that a spatial management approach warrants further investigation, and provide suggestions for changing how fisheries observers might be deployed to provide data helpful for evaluating a spatio-temporal management strategy for reducing pilot whale bycatch in eastern US pelagic longline fisheries. 

Researchers deployed LED lights on the floatlines of paired gillnets (control vs illuminated net) during 864 fishing sets using small-scale vessels departing from three Peruvian ports between 2015 and 2018. Bycatch probability per set for sea turtles, cetaceans and seabirds as well as catch per unit effort (CPUE) of target species were analyzed for illuminated and control nets using a generalized linear mixed-effects model (GLMM). For illuminated nets, bycatch probability per set was reduced by up to 74.4 % for sea turtles and 70.8 % for small cetaceans in comparison to non-illuminated, control nets. For seabirds, nominal bycatch per unit effort (BPUE) decreased by 84.0 % in the presence of LEDs. Target species CPUE was not negatively affected by the presence of LEDs. This study highlights the efficacy of net illumination as a multi-taxa BRT for small-scale gillnet fisheries in Peru. 

A long-term study assessed the efficiency of acoustic pingers (AQUAmark 100, 20-160kHz) in reducing the encounter rates of finless porpoises (Neophocaena spp.) with fishing nets. The study used a passive recorder to obtain acoustic encounter rates of echolocating finless porpoises over two eight-month periods. Encounter rates were significantly lower in periods when pingers were in use, but this effect decreased over time. By the end of each study period, the number of encounters was greater than those during periods without pingers, suggesting that habituation had occurred. However, when pingers were reactivated after four months of no use, encounters returned to lower levels, such as those observed during the beginning of the experiment. The results suggest that habituation to pingers may be mitigated by alternating periods of silence with periods of active pinger use. 

The study combined fisher questionnaires, acoustic monitoring, and participatory experiments to investigate the occurrence of bottlenose dolphins (Tursiops truncates) in the gillnet fisheries of Northern Cyprus. Dolphins were present in fishing grounds throughout the year, and were detected at 28% of net sets. Net damage was six times greater when dolphins were present during sets. Use of an acoustic pinger (AQUAmark 200, 5-160kHz) was tested, but had no significant effect on dolphin presence. 

The experiment evaluated the effectiveness of two types of pingers (Aquamark 100 and Aquamark 200) to reduce the bycatch rate of harbor porpoise (Phocoena phocoena) in a set gillnet fishery in the Black Sea. The study also evaluated the effects of the pingers on catch of target and non-target fish species. There was no significant difference in catch of target and non-target fish species in trials with pingers versus control sets. There was also no significant difference between number of harbor porpoises caught in nets using pingers and when no pingers were used, although a low overall number of porpoises were caught (eight harbor porpoises were caught during the experiment – three in control nets, three in nets using the Aquamark 100, and one in nets using the Aquamark 200). 

This study examined spatial interactions between false killer whales (Pseudorca crassidens) and the Hawaii (U.S.)-based deep-set longline fishery. False killer whales occur as bycatch in this fishery at rates that exceed allowable levels. Five satellite tagged whales (occurring within three groups) in combination with logbook entries showed that only two groups of whales approached gear at a distance closer than 50km. On two occasions, whales from one group came close enough to interact with gear, and one of six sets involved had no catch which may be explained by depredation. The haul phase showed the highest “attraction effect,” and the results suggest this portion of fishing activity may be an important factor in bycatch.

Two dolphin click detectors (F-PODs) were placed in two artisanal gillnets in Claromecó (Buenos Aires province, Argentina). Narrowband high-frequency (NBHF) clicks were found near both gillnets, compatible with the description of the franciscana (Pontoporia blainvillei) sound production. These preliminary results confirm that passive acoustic monitoring is a good tool to assess franciscana presence.

 This study aims to provide a comprehensive assessment of the acoustic capabilities of the franciscana (Pontoporia blainvillei). The authors examined the detailed acoustic signals of franciscana dolphins, and compared the sounds from rehabilitated dolphins in captivity with those of wild dolphins near fishing nets. Significant differences in acoustic characteristics were found between neonates and older dolphins, with juvenile and wild dolphins showing similar features. For the first time, repetition patterns in click production were identified, highlighting the importance of understanding the context of these sounds in regards to feeding and communication. This study emphasizes the need for detecting neonates for species protection and suggests the potential for developing acoustic classifiers specific to different age groups.