Search The Database

Field experiments were conducted to determine behavioral responses of minke whales (Balaenoptera acutorostrata) to experimental ropes and buoys made up of different colors, simulating those used in crab and whelk fishing gear. Trials were conducted with yellow, orange, green, blue, white and black ropes. Visual and acoustic monitoring was used to assess behavioral responses of whales to the different experimental gears. In addition, remote sensing equipment was used to monitor oceanographic conditions, underwater sounds and to video the whales as they swam near the experimental ropes. The results indicated a positive correlation between whale approach velocity and departure velocity and bearing changes. Minke whales decreased their swimming velocity and altered their bearing when passing by these ropes and increased their velocity once they had passed by the ropes. This was most evident when the ropes were black and white. Low frequency vocalizations and altered swimming trajectories were also noted in some whales as they passed near the ropes. 

Two devices were designed to prevent odontocetes from depredating caught fish and putting themselves at-risk of becoming bycatch. One device used physical deterrence by shrouding the fish with a barrier and the other used psychological deterrence by utilizing prior negative experiences of temporary entanglement in fishing gear. Both devices fit on a branchline at a distance from the hook and descend towards a caught fish using a line tension trigger mechanism. All interactions occurred on control branchlines that were not fitted with a deterrent device, suggesting the potential of this technology to deter depredating odontocetes. The impact on fish catch rates, size, and survival was negligible. 

Odontocete (i.e. toothed whale) interaction with longline fisheries is a global phenomenon that threatens the status of some populations and the economic viability of longline fisheries. This review paper summarizes the trend and geographical extent of interactions, the potential impact on odontocetes and fisheries, and describes potential acoustic and physical mitigation solutions. 

This study characterizes bycatch of marine mammals in fisheries that export fish to the United States of America from Ecuador, and identifies opportunities for collaboration on bycatch mitigation. The marine mammal species reported most frequently as bycatch were the humpback whale (Megaptera novaeangliae), bottlenose dolphin (Tursiops truncatus) and common dolphin (Delphinus delphis). Most interviewees indicated that the mammal bycatch rate has remained unchanged or increased over the last five years.

This study used systemic scar analysis to estimate the frequency of non-lethal entanglements among humpback whales (Megaptera novaeangliae) off the coast of Iceland from 2005-2017. Results demonstrate that at least 24.8% of individuals had prior entanglement(s) when first encountered, and then subsequently acquired new entanglement-related injuries at an average rate of 1.9% per year; however, scar-based estimates usually underestimate the frequency of prior entanglements. At least some entanglements seem to have occurred locally. 

A cumulative impact analysis framework integrating species habitat suitability and fishing effort data, stratified by gear type, was used to assess bycatch risk for threatened and protected species in China's seas and adjacent waters. Across all taxonomic groups examined, including seabirds, sea turtles, marine mammals, elasmobranchs, bony fishes, and benthic invertebrates, the highest bycatch risk was concentrated between 23°N and 25°N. For marine mammals and sea turtles, elevated risk was concentrated along China's southeastern coast, extending through inshore waters from the Yangtze River Estuary south to 20°N, with trawls and gillnets contributing most significantly to risk. Seabird bycatch hotspots were primarily located around islands, bays, and estuaries north of 20°N, where gillnets posed the greatest threat. Elasmobranchs experienced high bycatch risk from the Taiwan Strait to the Yangtze River Estuary and around Jeju Island, and were the most vulnerable taxa group overall. Bycatch risk for benthic invertebrates was largely restricted to narrow nearshore areas and was associated primarily with dredging activities. The study also found that marine protected areas generally exhibited lower bycatch risk than surrounding waters.