Fishing Hooks

Accidental hooking of turtles on fishing lines is a widespread threat to Canada’s turtles. Many freshwater turtles are opportunistic scavengers that also take live prey, making them vulnerable to getting caught on baited fishing hooks. Often anglers will simply cut the fishing line when a turtle is hooked, so the hook remains caught in the turtle. Some hooks get caught in the mouth of the turtle, which can making feeding difficult. Other hooks are swallowed and lodge in the throat or even the stomach, which can be fatal. It is unclear how often swallowing a fishing hook kills freshwater turtles, however, roughly 55% of Loggerhead Sea Turtles that were deeply hooked were presumed to have died as a result (Swimmer et al. 2014). Even if the fishing hook does not kill the turtle, there is also the risk of lead poisoning if lead sinkers are also swallowed (Borkowski 1997). Studies indicate that ingesting fishing hooks has led to increased mortality rates in birds, fish, mammals, and sea turtles (Nuhfer and Alexander 1992, Chaloupka et al. 2004, Casale et al. 2008, and Dau et al. 2009).

How many turtles are affected by fishing hooks?

Many turtles are accidentally hooked every year. One study in Europe found that 3 of 17 (18%) European Pond Turtles that were X-rayed contained fishing hooks (Nemoz et al. 2004). A study from Tennessee and Virginia found 27 turtles with ingested fishing hooks in the esophagus or abdomen and at one study site over 30% of the adult female Snapping Turtles had swallowed fishing hooks (Steen et al. 2014). And in Florida, up to 36% of Alligator Snapping Turtles had ingested fishing hooks (Enge et al. 2014). Interviews with anglers at a park in New Brunswick revealed that approximately 5% of anglers had accidentally hooked a turtle in the past (Browne and Sullivan 2018).

What species of turtles are affected?

Any turtle that occurs in waters that are commonly fished by people could potentially get hooked, but Snapping Turtles are often hooked the most, likely because of their size, their widespread nature, and their feeding behaviour. Other Canadian species known to get caught on fishing hooks include the Northern Map Turtle, Painted Turtle, Spiny Softshell, and Wood Turtle (Steen et al. 2014, Browne and Sullivan 2018, Gillingwater personal communication).

Why is this an issue for turtles?

The life history strategy of turtles differs from those of most mammals. Turtles have very high rates of egg and hatchling mortality, but that is balanced out with very low rates of adult mortality. Adult females keep laying eggs, year after year, for decades. This strategy has worked well for turtles for over 200 million years. If the adult mortality rate of turtles increases by only a few per cent per year, however, it can lead to populations declining over time. In a population of 100 turtles, the annual loss of even two or three adults will cause the population to slowly decline and possibly be wiped out completely. Modelling studies suggest that ingesting fishing hooks alone can cause enough mortality to result in population declines for some freshwater turtles (Steen and Robinson 2017).

What to do if you hook a turtle

Consider using barbless hooks when fishing in areas with large turtle populations to make hooks easier to remove. If you do hook a turtle while fishing there are a few things that can be done to help the turtle.

  1. Reel the turtle in slowly and as gently as possible to prevent the hook digging in deeper.
  2. Never cut your line and release the hooked turtle. A hook left embedded in a turtle can lead to its death.
  3. Use a net or grab the back end of the turtle’s shell to lift it out of the water; to prevent further injury, don’t lift by the fishing line or tail.
  4. Be cautious. Turtles may bite or scratch to protect themselves. Be extra careful with Snapping and Spiny Softshell Turtles as they have long, flexible necks and a powerful bite.
  5. If the hook is difficult to remove, caught in the mouth, or swallowed, medical care is required.

If you are in Ontario, call the Ontario Turtle Conservation Centre at (705) 741-5000. They will provide medical care at no charge and have volunteers to assist with transportation from anywhere in Ontario.

Download the Canadian Wildlife Federation flyer on turtles and fishing hooks

Literature cited

Borkowski, R. 1997. Lead poisoning and intestinal perforations in a snapping turtle (Chelydra serpentina) due to fishing gear ingestion. Journal of Zoo and Wildlife Medicine 28:109–113. https://www.jstor.org/stable/20079497

Browne, C. L. and A. Sullivan. 2018. Investigating the threat of angling on turtle populations in an urban park in New Brunswick. Conference abstract, Canadian Herpetological Society conference, Kamloops, BC, September 2018. http://www.canadianherpetology.ca/conf/docs/2018/CHS%202018%20Kamloops%20Program.pdf

Casale P., D. Freggi, and M. Rocco. 2008. Mortality induced by drifting longline hooks and branchlines in loggerhead sea turtles, estimated through observation in captivity. Aquatic Conservation: Marine and Freshwater Ecosystems 18: 945–954. https://doi.org/10.1002/aqc.894

Chaloupka M., D. Parker, and G. Balazs. 2004. Modelling post-release mortality of loggerhead sea turtles exposed to the Hawaii-based pelagic longline fishery. Marine Ecology Progress Series 280: 285–293. https://doi.org/10.3354/meps280285

Dau B. K., K. V. K. Gilardi, F. M. Gulland, A. Higgins, J. B. Holcomb, J. St. Leger, and M. H. Ziccardi. 2009. Fishing gear-related injury in California marine wildlife. Journal of Wildlife Diseases 45: 355–362. https://doi.org/10.7589/0090-3558-45.2.355

Enge K. M., T. M. Thomas, E. Suarez. 2014. Population status, distribution, and movements of the alligator snapping turtle in the Suwannee River, Florida. Report, Florida Fish and Wildlife Conservation Commission, Tallahassee.

Gillingwater, S. 2018. Species at risk biologist, Upper Thames River Conservation Authority. Personal communication.

Nemoz, M., A. Cadi, and S. Thienpont. 2004. Effects of recreational fishing on survival in an Emys orbicularis population. Biologia 59:185–189.

Nuhfer A. J., and G. A. Alexander. 1992. Hooking mortality of trophy-sized wild brook trout caught on artificial lures. North American Journal of Fisheries Management 12: 634–644. https://doi.org/10.1577/1548-8675(1992)012<0634:HMOTSW>2.3.CO;2

Steen, D. A., B. C. Hopkins, J. U. Van Dyke, and W. A. Hopkins. 2014. Prevalence of ingested fish hooks in freshwater turtles from five rivers in the southeastern United States. PloS One, 9:e91368. http://dx.doi.org/10.1371/journal.pone.0091368

Steen, D. A., and O. J. Robinson Jr. 2017. Estimating freshwater turtle mortality rates and population declines following hook ingestion. Conservation Biology 31:1333–1339. https://doi.org/10.1111/cobi.12926

Swimmer Y, C. E. Campora, L. McNaughton, M. Musyl, and M. Parga. 2014. Post-release mortality estimates of loggerhead sea turtles (Caretta caretta) caught in pelagic longline fisheries based on satellite data and hooking location. Aquatic Conservation 24:498–510. https://doi.org/10.1002/aqc.2396