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This article describes the design and fabrication of a prototype rope-less fishing system that might be used in the Gulf of Maine lobster (Homarus americanus) fishery. Rope-less fishing gear, which secures vertical fishing lines to the bottom until they are released for hauling, is a potential mitigation measure to reduce vertical line entanglements of marine mammals including North Atlantic right whales (Eubalaena glacialis), along with leatherback sea turtles (Dermochelys coriacea). The prototypes consists of a flotation line spool capable of holding up to 900 m of 1/2 in line. The spool is secured to a lobster trawl by a mechanical release that can be triggered for hauling either using a digital timer or acoustic transponder. In addition to the rope-less prototype, the study conducted a preliminary investigation on the passive acoustic detectability of rope-less gear.

Acoustic deterrents were tested for their ability to deter humpback whales (Megaptera novaeangliae) from potential sources of entanglement. Low frequency (3 kHz, 135 +/- 5 db, 5 s emission interval and 400 ms emission duration) alarms were tested. Alarms were placed in the center of the northerly migration path (southern hemisphere) of humpback whales. Observers, who were unaware of the alarm status (i.e. on/off) tracked the pods as they passed the alarms. Sixty percent of the pods (N=137) passed within the assumed detectable range (500 m) of the alarm. Sixty five percent passed the alarm while it was on and 52% when it was off. Therefore, there does not appear to be any noticeable response from the whales to the alarms. There were no differences in the directionality, course heading or dive duration within the detectable range of the alarm, whether on or off. It is therefore unlikely that single alarms currently used with trap or pot lines are effective at reducing interactions with humpback whales.

The ability of acoustic alarms to alert migrating humpback whales (Megaptera novaeangliae) to fishing gear was tested. Two alarms were used, each with a distinct tone. One alarm had a 5 kHz tone (5 s emission interval and 400 ms emission duration), and one had a 2-2.1 kHz swept tone (8 s emission interval and 1.5 s emission duration). The response of the whales in terms of changes to surface behavior and travel direction were investigated. A total of 108 migration tracks were collected using a theodolite. The study was conducted at Cape Solander, Sydney, Australia. The whales showed no detectable response to either of the alarms; direction and surfacing behavior did not vary between when the alarms were on or off. These types of tones are unlikely to be effective as whale entanglement deterrents.

Documented entanglements, long-term population studies and mark-recapture studies were evaluated to determine the impact of cryptic mortality on North Atlantic right whales (Eubalaena glacialis). Results suggest entangled adults had low initial survival (0.749). Adults that did survive the first year had survival rates similar (0.952) to those animals never entangled (0.961 female and 0.986 male). Juveniles had post entanglement survival rates similar to initial survival rates of entangled adults, 0.733, but lower than un-impacted juveniles (0.978). Health impacts were the most predictive aspect of subsequent survival. In addition, entanglement configuration and resulting injuries also affected the final outcome. Human interventions appear to improve survival outcomes for entangled whales.

Bryde's whale (Balaenoptera edeni) behavior was studied using suction-cup attached tags. Behavior was studied to identify potential mitigation measures that could reduce lethal vessel strikes in the Hauraki Gulf, New Zealand. Tagged whales spent 91% of their time at depths within the maximum draft of vessels. This behavior could increase the potential for vessel strikes. Analysis of vessel transits and whale sightings suggested that re-routing of vessel traffic in the Gulf would not be beneficial because whales are distributed throughout the Gulf. Passive acoustic devices are not viable due to the low vocal activity of whales and potential masking of noise from vessels. A social forum was developed with stakeholders. The only viable option decided upon by this forum was a Transit Protocol for Shipping which includes voluntary speed restrictions and a monitoring plan.

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.

This study collected information on cetacean incidents (carcasses, injured and debilitated animals found onshore, entrapped in shallow water, entangled or floating offshore) that have occurred in New South Wales, Australia. Information on marine mammal incidents was reported to the New South Wales National Parks and Wildlife Service and recorded into a Marine Fauna Events Database. This information was analyzed for trends in mortality and population dynamics such as age and sex ratios. Records existed for the time period of 1790 to 2013. For the majority of incidents, the cause of mortality/morbidity could not be determined. Anthropogenic causes, such as entanglements, accounted for more incidents compared to natural causes such as disease or predation. Entanglement was the largest cause of cetacean incidents that were made up mostly of humpback whale (Megaptera novaeangliae) entanglements. Reporting of incidents have increased over time, from 1.3 incidents per year prior to 1960 to 43.5 per year during 2010, 2011, 2012 and 2013. A concentration of incidents were found in the Northern Rivers and North Coast regions. This study highlights the importance of these types of databases.

Documented entanglement cases for sea turtles and cetaceans in mussel aquaculture gear worldwide were collected. Online surveys and semi-structured interviews with mussel operators were used in Iceland. A total of seven entanglement reports were collected, four baleen whales, one harbour porpoise (Phocoena phocoena) and two leatherback sea turtles (Dermochelys coriacea). Mussel spat collecting ropes were involved in the majority of cases. Out of the seven reports, two occurred in Iceland. The proximity between cetacean distributions and mussel farming sites is likely a factor in these interactions. In addition, in Icelandic summer spat collection occurs when the largest concentrations of cetaceans are found in its waters. Iceland should consider some sort of mandatory reporting system for these interactions.

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.

A summary study of acoustic 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.