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A quantification of interactions between cetaceans and fishers was conducted in the Atlantic and Indian Oceans. A large database of captains logbooks, 1980-2011, was analyzed along with scientific observer observations recorded between 1995 and 2011. The main areas of high co-occurrence between cetaceans and fisheries was shown to exist east of the Seychelles from December to March, the Mozambique Channel between April and May, and in offshore waster of Gabon between April and September. Cetacean associated fishing sets occurred in 3% of sets in both oceans and 0.62% of sets has encircled cetaceans. Survival rates for encircled cetaceans appear to be high. This suggests setting nets close to cetaceans has a low immediate impact to the individual species.

Pingers have been used on shark nets set along Queensland's beaches since 1992. Due to an increase in whale entanglements in 2009, new pingers (Fumunda F3 whale pingers and F10 dolphin pingers) were deployed between July and August 2010. Subsequently updated research on the use of these pingers was needed. For this study, the acoustic characteristics of pingers used on shark nets in Queensland Australia were measured and used to model sound propagation, estimate over what range marine mammals could detect the pingers, monitor ambient noise and to make recommendations on pinger deployment to the Queensland Shark Control Program (QSCP). The results of the sound propagation study indicate that the tones were a few hundred Hz less (2.6-2.8 Hz for F3 and 9.4-9.6 Hz for F10) than indicated. All pingers emitted multiple harmonics and fundamental tones. The power spectrum density levels varied up to 20 dB from angle to angle and pinger to pinger. The 1st harmonic of F3s was audible to all marine mammals over the longest ranges. Only 2 of the 6 tested pingers reached the manufacturer's listed audible range of 1-5 km. During testing, the ranges depended on the individual pinger and angle of the pinger toward the mammal. When animals travel alongside the net, a number of pingers should be set in a series. Based on the current configuration of 3-4 pingers per net of 200 m, humpback whales would hear all of the pingers at any location along the net but dolphins would hear only 1-2 pingers. When animals swim straight at the net, maximum pinger spacing would need to be based on the animals swim speed. The current net/pinger configuration is adequate for humpback whales, dugongs and dolphins swimming at normal travelling speeds. The current pinger spacing is insufficient for dolphins swimming straight at the net at high speeds.

A summary study of methods used to reduce or eliminate marine mammal entanglements was conducted. The authors found little evidence on the effectiveness of the use of sound to reduce or eliminate marine mammal incidental capture. Substantial decreases in cetacean bycatch, due to the use of passive methods such as increasing fishing net reflectivity, were not evident through comparisons of catch rates in commercial fisheries or from observational deterrence studies. Net alarms have been shown to greatly reduce whale entrapment in Canadian fish traps but similar success has not been shown in reducing small cetacean bycatch in many gillnet fisheries. Few controlled studies on the use of sound to reduce or eliminate marine mammal interactions have been conducted. There is a need to additional basic research on echolocation behavior and behavioral interactions between marine mammals and fisheries.

Information on bycatch of Hector's dolphins (Cephalorhynchus hectori) in New Zealand waters was reviewed and new estimates were presented. Prior to 2008, 110-150 Hector's dolphins were estimated to be caught annually. Of these, 35-46 were caught of the east coast South Island. Between May 2009 and April 2010, an estimated 23 Hector's dolphins were caught of the east coast South Island. Previous risk analyses have shown similar results. Combined this information suggests continued overlap between Hector's dolphins and fisheries. The risk analyses indicate that Hector's dolphin populations could recovery to 15,000 individuals (from 7873) over the next 50 years if there was no fishing mortality. Risk analyses all indicate that the population of Hector's dolphins has declined substantially due to fishing mortality. Current management and  recovery actions are unlikely to to result in recovery of this species. 

Six different acoustic pingers and signals were tested at sea to determine their impact on dolphin behavior. Two prototype devices from the Board Iascaigh Mhara (BIM) were tested. One was a continuous pinger (CP) and the second a responsive pinger (RP). These were tested on five occasions. A third modified RP was also tested on five occasions and a fourth RP was modified into a multiple signal output device and tested on 15 occasions. In addition, the CETASAVER and Dolphin Deterrent Device (DDD) were tested on five and ten occasions respectively. The BIM and RP acoustic pingers did not elicit any response from the dolphins. The CETASAVER and DDD elicited a mild response. The authors suggest significant modification to the signal type or source level. At the current state of development acoustic pingers may not provide effective deterrent signals to dolphins.

Field testing was conducted in the lower Bay of Fundy, Canada, during 1996 and 1997 to determine the effectiveness of acoustic alarms (Netmark 1000) in reducing bycatch rates of harbor porpoises (Phocoena phocoena) in gillnets. Alarms were spaced 100 m apart along the gillnet float-line. There was a 77% reduction in bycatch of harbor porpoises in nets equipped with alarms compared to those with no alarms. There were no significant differences in catch rates of target species, Atlantic cod (Gadus morhua), Atlantic herring (Clupea harengus) and pollock (Pollachius virens). 

Four commercially available pingers (AIRMAR, Aquamark 100, Fumunda, Save Wave Saver) were tested on vessels operating in Cornwall targeting hake (Merluccius merluccius) with gillnets. Pingers were tested for their effectiveness at reducing incidental interactions between the gillnets and porpoises (Phocoena phocoena). Only one of the four tested pingers, AIRMAR, performed 'satisfactorily' (i.e. suited for offshore gillnet fishery). 

A study was conducted in Sundarbans mangrove forest of Bangladesh to assess the behavioral response of Ganges River dolphins (Platanista gangetica) to pingers. Just under 62 hours of theodolite tracking data from 75 dolphin sightings and 2,829 theodolite fixes of dolphin surfacing were analyzed. The results suggest pingers had a subtle displacement effect on the dolphins. There was an increase in the mean surfacing distance of dolphins from the pinger buoy within a 100 m radius. Pingers did not result in a decrease in the minimum distance of approach for dolphins. Pingers did not change the frequency of sightings detected within 100 m of the pinger buoys. The results remain unclear whether pingers would be able to prevent entanglement in gillnets by Ganges River dolphins.

The impact of Medina panels attached to tuna purse seine nets operating in the US fishery was investigating for their effect on porpoise mortality. Medina panels are reduced mesh size netting hung from 2-inch mesh webbing on the purse seine. The authors took measurements of penetration of porpoise snouts and flippers through mesh openings of 2, 1 7/8, 1 1/2 and 1 inch to determine the potential reduction in porpoise entanglements. Even the smallest-sized porpoise could not fit its snout through the 1 inch panel, even with its mouth closed. Recent tests of porpoise 'aprons' and 'chutes' could be promising in making these small mesh panels compatible with tuna purse seine performance.

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.