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This article reviewed bycatch mitigation methods that rely on sensory ecology to reduce interactions with seabirds, sea turtles, pinnipeds and blue-water fish. Panels containing patterns of low spatial frequency and high internal contrast can be used for all of these species. These panels are not likely to reduce catches of target species and are easy and inexpensive to apply. The authors suggest that sound signals on gillnets are not recommended for most bycatch species, except for cetaceans. Cetaceans require both visual cues and warning through echolocation.

Three types of bycatch reduction devices (BRD) [turtle excluder device (TED), square mesh codend (SMC) and fisheye (FE)] were tested aboard shrimp trawl vessels. Differences in catch from nets equipped with a BRD on one side and a standard net on the other were compared for each of the three BRDs. Use of the TED resulted in no captures of sea turtles or large animals, and did not significantly reduce shrimp catches or fish bycatch. The SMC reduced both shrimp and bycatch catches, although only a reduction in bycatch was significant. The SMC did result in catches of larger shrimp compared to the other nets. The FE significantly reduced shrimp and bycatch catches.

Three types of bycatch reduction devices (BRD) [turtle excluder device (TED), square mesh codend (SMC) and fisheye (FE)] were tested aboard shrimp trawl vessels. Differences in catch from nets equipped with a BRD on one side and a standard net on the other were compared for each of the three BRDs. Use of the TED resulted in no captures of sea turtles or large animals, and did not significantly reduce shrimp catches or fish bycatch. The SMC reduced both shrimp and bycatch catches, although only a reduction in bycatch was significant. The SMC did result in catches of larger shrimp compared to the other nets. The FE significantly reduced shrimp and bycatch catches.

Three types of bycatch reduction devices (BRD) [turtle excluder device (TED), square mesh codend (SMC) and fisheye (FE)] were tested aboard shrimp trawl vessels. Differences in catch from nets equipped with a BRD on one side and a standard net on the other were compared for each of the three BRDs. Use of the TED resulted in no captures of sea turtles or large animals, and did not significantly reduce shrimp catches or fish bycatch. The SMC reduced both shrimp and bycatch catches, although only a reduction in bycatch was significant. The SMC did result in catches of larger shrimp compared to the other nets. The FE significantly reduced shrimp and bycatch catches.

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.

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.

Loggerhead sea turtles (Caretta caretta) have a high-density foraging hot spot in Baja California Sur, Mexico. This spot coincides with intense bottom-set net fisheries. Controlled studies were conducted in Baja California Sur, Mexico between 2007 and 2009 to compare turtle bycatch rates with target catch rates, composition, and market value between control and buoyless nets. A total of 136 controlled sets were made. The results suggest that mean turtle bycatch was reduced by 68% with the use of buoyless nets but target catch rates were not impacted. 

Observer data from European purse seine vessels operating in the Atlantic and Indian Ocean (1995-2011) were used to assess spatial and temporal variation in sea turtle bycatch rates. Information from both free swimming school sets and sets made on drifting fish aggregating devices (DFADs) was included in the analysis. Overall the results indicate purse seine fisheries have a very low impact on sea turtles. Annually, 218 and 250 individual sea turtles were estimated to be captured by purse seines operating in the Atlantic and Indian Ocean respectively. The majority, 75%, of these turtles were released alive. The study also suggests that drifting fish aggregating devices (DFADs) may play a role in aggregating juvenile sea turtles.

Incidental catch of the loggerhead sea turtle (Caretta caretta) in the Mediterranean basin is the main threat to its conservation. In this basin, fisheries are multi-species, multi-gears and multi-national, making demersal fishing activities profitable, while preserving sea turtles is a challenge. In this study, scientists developed bycatch reducer devices and alternative fishing gears to mitigate the impact of demersal fishing gears on sea turtles. This included (i) testing hard and flexible Turtle Excluder Devices in bottom trawling nets and (ii) using ultraviolet LEDs as visual deterrents to illuminate set nets to avoid entanglement. The results of this study suggest the different devices did not affect the commercial catch, while bycatch reduction was instead evident. These results advocate for a global effort to introduce bycatch reduction devices in different areas and fisheries of the Mediterranean. 

In the Mediterranean Sea, trawl nets have high levels of bycatch of protected species, including the loggerhead turtle (Caretta caretta), with high rates of mortality. A new flexible Turtle Excluder Device (TED) was tested for the first time on a commercial scale in the Mediterranean Sea to assess its effectiveness in reducing bycatch. The results did not show any significant (α = 0.05) loss in terms of commercial catch weight, but resulted in a significant reduction of debris in the codend of the nets in comparison to traditional nets. During the study, no turtles were captured in either the traditional or TED net. While modification of fishing gear requires significant investment, the flexible TED is technically feasible in the Mediterranean and may assist in the conservation of loggerhead sea turtles.