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Field Study 723

Study Type
Field study in the wild
Location
Western North Atlantic
Target catch
Swordfish and tuna
Effect on bycatch species
Circle hooks decreased loggerhead and leatherback catch; even more effective for loggerheads when combined with mackerel bait
Effect on target catch
Circle hooks combined with mackerel bait increased swordfish catch by weight. With squid, decreased swordfish catch, increased bluefin and albacore tuna catch. Mackerel bait decreased bigeye and albacore tuna catch.
Bycatch species
Elasmobranchs
Caretta caretta (Loggerhead turtle)
Demochelys coriacea (Leatherback sea turtle)
Reduction technique
Alternative bait
Circle hooks
Fishing Gear
Hooks-and-Lines

Field Study 723

Study Type
Field study in the wild
Location
Western North Atlantic
Target catch
Swordfish and tuna
Effect on bycatch species
Circle hooks decreased loggerhead and leatherback catch; even more effective for loggerheads when combined with mackerel bait
Effect on target catch
Circle hooks combined with mackerel bait increased swordfish catch by weight. With squid, decreased swordfish catch, increased bluefin and albacore tuna catch. Mackerel bait decreased bigeye and albacore tuna catch.
Bycatch species
Elasmobranchs
Caretta caretta (Loggerhead turtle)
Demochelys coriacea (Leatherback sea turtle)
Reduction technique
Alternative bait
Circle hooks
Fishing Gear
Hooks-and-Lines

The effects of a lanthanide metal alloy on shark catch rates

Submitted by morgaac on

Longlines with baited hooks affixed with a block of metal alloy (Nd/Pr) were tested against hooks with a lead weight attached (control), to determine their ability to repel sharks.  Two experiments were conducted in Hawaiian waters, one in the Southern California Bight (SCB) and and one in the Eastern Tropical Pacific off the coast of Eduador.  Significant differences were only found for juvenile hammerhead sharks targeted in one of the Hawaiian experiments.

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Harbor Porpoise

Species
Phocoena phocoena

Although it is believed that the harbor porpoise population is not seriously in danger at present, incidental catch of the species in gillnets continues to be the primary threat throughout its range (Hammond et al 2008). Off the eastern coast of the US, an estimated 1200 to 2900 harbor porpoises were killed annually in gillnets between 1990 and 1996 (Waring et al 1998). In the North Sea, Danish annual estimates of bycatch ranged from 2867 to 7566 between 1990 and 2002 (Vinther & Larsen 2002).

Distribution
Cold temperate to sub-Arctic coastal waters in the Northern Hemisphere
Population
>700,000
IUCN Status
Least Concern
Type
Mammal
Bycatch Threat
Gillnets and other entangling nets, weirs

Mediterranean Monk Seal

Species
Monachus monachus

The once-abundant Mediterranean monk seal has been adversely impacted by human activities, ranging from exploitation for fur and oil to habitat fragmentation that have occured over many centuries. Today, one of the greatest threats facing the remaining seals is accidental entanglement in fishing nets. Bycatch mortality occurs throughout the species' range, and has been increasingly problematic since the 1980s (Guclusoy et al 2004).

Distribution
Isolated colonies in the Aegean and Ionian Seas, and in the eastern North Atlantic from Morocco to Cap Blanc
Population
350-450
IUCN Status
Critically Endangered
Type
Mammal
Bycatch Threat
Gillnets, trammel nets, ghost nets, bottom-set long lines

Significant conservation benefits obtained from the use of a new fishing gear in the Chilean Patagonian toothfish fishery

Submitted by Kate McClellan on

A modified longline system with a net sleeve and weight on the secondary vertical line was tested in the Chilean Patagonian toothfish fishery. A net sleeve that deploys to cover the fish/hook when hauled and a weight were attached to the vertical hook line. The net sleeve significantly reduced depredation of fish by killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus). The weighted line also was able to reduce seabird bycatch deaths to zero.  

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Experimental fishing with an "umbrella-and-stones" system to reduce interactions of sperm whales (Physeter macrocephalus) and seabirds with bottom-set longlines for Patagonian toothfish (Dissostichus eleginoides) in the Southwest Atlantic

Submitted by Kate McClellan on

The Patagonian toothfish longline fishery in the Southwest Atlantic suffers from depredation of fish by sperm whales and high bycatch rates of seabirds. This study assessed depredation and seabird bycatch using a modified longline with an "umbrella" net sleeve system with stones for faster sinking. The "umbrella-and-stones" system was effective for preventing bycatch and appeared to restrict depredation, but catches were significantly reduced.  

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