, Behavioural Responses of Humpback Whales (Megaptera novaeangliae) to Two Acoustic Deterrent Devices in a Northern Feeding Ground off Iceland, Aquatic Mammals , v. 46(6), 2020 , ps 584-602 Aalbers, S.A., Stutzer, G.M. and Drawbridge, M.A., The effects of catch-and-release angling on the growth and survival of juvenile white seabass captured on offset circle and J-type hooks, North American Journal of Fisheries Management , v. 24, 2004 , ps 793-800 Afonso, A., Hazin, F., Carvalho, F., Pacheco, J., Hazin, H., Kerstetter, D., Murie, D., Burgess, G., Fishing gear modifications to reduce elasmobranch mortality in pelagic and bottom longline fisheries off Northeast Brazil, Fisheries Research , v. 108, 2011 , ps 336-343 Aguilar-Ramirez, D. and Rodriguez-Valencia, J.A., Reducing bycatch with better technology in the Gulf of California shrimp fishery; Final technical and financial report to the Walton Family Foundation, submitted by World Wildlife Fund, World Wildlife Fund , 2010 , ps 31 Akinnigbagbe, R. O., Unique improved selective fishing traps with adjustable escape gaps for effective fisheries management, International Journal of Fisheries and Aquatic Studies , v. 7(6), 2019 , ps 355-358 Al-Baz, A. and Chen, W., An assessment of bycatch reduction devices in Kuwait’s shrimp trawl fishery, Journal of Applied Ichthyology , v. 2014, 2014 , ps 1-11 Alió J., L. Marcano, D. Altuve, G. Andrade, L. Villasmil, R. Alvarez, L. González, J. Sayegh, E. Trujillo, O. Pomares, A. Díaz, C. Torrens, G. Vizcaíno, M. Figueroa, J. Boada and A. Marval, The use of devices to reduce bycatch in Venezuelan shrimp fisheries and the FAO Code of Conduct for Responsible Fishing, II Foro iberoamericano de los recursos marinos y la acuicultura , v. 2, 2009 , ps 501-506 Allerton, A.J.L., Schneider, E.V., Kiszka, J.J. and Talwar, B.S., Trends in Marine Mammal Bycatch in US Fisheries From 1990 to 2017, Aquatic Conservation: Marine and Freshwater Ecosystems , v. 35(2), 2025 , ps 12 Almeida, A., Alonso, H., Oliveira, N., Silva, E. and Andrade, J, Using a visual deterrent to reduce seabird interactions with gillnets, Biological Conservation , v. 285, 2023 , ps 8 Amano, M., Kusumoto, M., Abe, M., and Akamatsu, T. , Long-term effectiveness of pingers on a small population of finless porpoises in Japan, Endangered Species Research , v. 32, 2017 , ps 35-40

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 BRD’s. 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.

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). Bycatch data from the Ionian Sea spanning 25 years shows that the second leading cause of mortality (24% of total deaths) was accidental entanglement (Panou et al 1993). Juvenile seals are particularly at risk, as they are often not strong enough to free themselves from even the weakest of fishing nets. From 1991-2007, an estimated 46% of deaths in sub-adult Mediterranean monk seals in Greece were caused by accidental entanglement (Karamanlidis et al 2008). As net material becomes harder to escape from due to constantly improving fishing technology and more widespread use of nylon line, this aspect of the bycatch problem is amplified (Guclusoy et al 2004). Inherent to the problem is the fact that the seals will actively seek out fishing nets to raid for food. Depletion of fishing stocks in the region coupled with increased fishing effort not only results in less prey available for the seals, but also in increased incidents of entanglement (Johnson & Karamanlidis 2000). The consequences of net raiding are often dire, as fishermen are likely to deliberately kill the animals in order to reduce damage to gear and perceived competition for fish (Karamanlidis et al 2008). In a few places, marine protected areas have been established to safeguard Mediterranean monk seal colonies. For example, in Turkey’s Foca Pilot Monk Seal Conservation Area, purse seining and trawling are prohibited (Guclusoy et al 2004). In Greece’s National Marine Park of Alonnisos, Northern Sporades and in the Desertas Islands Nature Reserve in the Madeira Islands, comparable regulations as well as a ban on all unnecessary human activity near pupping sites exist (Karamanlidis et al 2008). Acoustic pingers have been utilized to try and warn seals away from nets with limited success (Karamanlidis et al 2008). Fishery closures, even on a limited scale, such as during the breeding season, appear to be a much more effective technique, and creation of marine protected areas near pupping sites also seems to decrease bycatch mortality (Mursaloglu 1984; Karamanlidis et al 2008). Despite these and numerous other conservation measures in place on paper, efforts have largely failed at reducing incidents of bycatch and protecting the species in general (Aguilar & Lowry 2008), and the threat of extinction for the species is high (van Blaricom et al 2001).

References

Aguilar, A & L Lowry (IUCN SSC Pinniped Specialist Group). 2008. Monachus monachus. In: IUCN Red List of Threatened Species. Version 2012.1. Accessed 3 October 2012. www.iucnredlist.org.

Guclusoy, H. 2008. Interactions between monk seals, Monachus monachus (Hermann, 1779), and artisanal fisheries in the Foca Pilot Monk Seal Conservation Area, Turkey. Zoology in the Middle East 43: 13-20.

Guclusoy, H, CO Kirac, NO Veryeri, & Y Savas. 2004. Status of the Mediterranean monk seal Monachus monachus (Hermann, 1779) in the coastal waters of Turkey. E.U. Journal of Fisheries and Aquatic Sciences 21(3-4): 201-210.

Johnson, WM & AA Karamanlidis. 2000. When fishermen save seals. Monachus Guardian 3:18-22.

Karamanlidis, AA, E Androukaki, S Adamantopoulou, A Chatzispyrou, WM Johnson, S Kotomatas, A Papadopoulous, V Paravas, G Paximadis, R Pires, E Tounta & P Dendrinos. 2008. Assessing accidental entanglement as a threat to the Mediterranean monk seal Monachus monachus. Endangered Species Research: Preprint.

Mursaloglu, B. 1984. The survival of the Mediterranean monk seal (Monachus monachus) pup on Turkish coast. In: K Ronald & R Duguy (eds), The Monk Seal. pp. 41-47. Proceedings of the 2nd International Conference, La Rochelle, France 5-6 October 1984. Annales de la Societe des Sciences Naturelles de la Charante-Maritime Supplement.

Panou, A, J Jacobs, & D Panos. 1993. The endangered Mediterranean monk seal Monachus monachus in the Ionian Sea, Greece. Biological Conservation 64: 129-140. Van Blaricom, GR, LR Gerber, & RL Brownell Jr. 2001. Marine mammals, extinctions of. In: SA Levin (ed), Encyclopedia of Biodiversity. pp. 37-69. Academic Press, London, UK.

Gillnets, trammel nets, ghost nets, bottom-set long lines Isolated colonies in the Aegean and Ionian Seas, and in the eastern North Atlantic from Morocco to Cap Blanc

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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.  

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 shouding 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. 

A rare-earth metal alloy (cerium/lanthanide) was tested to determine if it would reduce bycatch of spiny lobster on longlines and rod and reel gear in the Gulf of Maine. Laboratory and field trials showed no significant reduction in dogfish catch.

Over time, noxious bait, consisting of dead steelhead containing lithium chloride, did not prevent California sea lion (Zalophus californianus) predation of Washington steelhead trout (Salmo gairdneri). Acoustic harassment devices worked only for a short time in reducing California sea lion depredation before sea lions began to habituate to sounds.

This study investigated whether North Atlantic right whale behavior changes, in terms of response distance, to changing visual characteristics of rope mimics in their path. 20 ft rope mimics were made from two 10 ft sections of rigid PVC pipe, with an approximate diameter of 1 inch. The rope mimics were weighted and attached to a lobster buoy to simulate a vertical line in the water column. A 30.5 cm disk was placed around the rope for reference use in video footage. The following color ropes were used: black, green, two types of white (white and glow in the dark), orange and red. Experiments were conducted in Cape Cod Bay using surface feeding whales. A significant difference in the distance of first change in behavior occurred between black and green ropes vs red and orange ropes. The response time was earlier with the latter colors. No significant difference was found between frontlit and backlit ropes.

Acoustic pingers reduced the bycatch of the Common Murre (Uria aalge) in the Puget Sound salmon drift gillnet fishery, but they did not reduce bycatch of the rhinoceros auklet (Cerorhinca monocerata). Reduction of target species catch was not significant. White gillnet mesh panels in the upper portion of the net reduce the bycatch of seabirds (Common Murres and Rhinoceros Auklet) in the Puget Sound salmon drift gillnet fishery. Rhinoceros Auklet bycatch was only reduced in 50-mesh visual alert nets. The white mesh panels decreased salmon catch in 50-mesh but not in 20-mesh.

School shark (Galeorhinus galeus) liver oil dripped behind fishing vessels in the northern New Zealand snapper (Pagrus auratus) longline fishery reduced seabird numbers and dives on baits when compared to canola oil and seawater control treatments. The shark liver oil did not affect the number of target snapper, gurnard (Chelidonicthys kumu), kaha-wai (Arripis trutta), or trevally (Pseudocaranx dentex) caught.