Bits & Pieces: Ice-Fishing Injuries and Unexplained Fish Populations

Medical Connections: Bumps, Bruises & the Ice Angler

Data on emergency department visits from the National Electronic Injury Surveillance System (NEISS) on all cases of fishing injury from 2009-2014 were analyzed by Mayo Clinic investigators to identify injury patterns sustained by ice anglers compared to traditional (non-ice) fishing in the United States.*

According to the Mayo Clinic News Network, the analyses revealed that 85 (1 percent) of the 8,220 cases were related to ice fishing. These injuries occurred most commonly in males (88 percent) and in those with an average age of 39.4. The most common ice fishing-related injuries included:

• Orthopedic or musculoskeletal, likely related to slips on the ice (46 percent)
• Minor trauma, such as lacerations, abrasions, contusions, punctures and hook injuries (37 percent)
• Major trauma, such as amputation, organ space injury and closed-head injuries, including concussions (6 percent)
• Hot thermal injuries, likely due to heating systems used in ice houses (5 percent)
• Immersion/drowning (5 percent each)
• Cold thermal injuries (1 percent)

Perhaps counterintuitively, cold thermal injuries ranked low on the list of the most common traumas sustained while ice fishing. Hypothermia did not affect any of the patients studied. “We expected to see more cold thermal injuries such as frostbite,” says Dr. Cornelius Thiels, one of the study’s authors. “This may be due to a reporting bias or sampling issues, but ice fishers are often highly experienced and prepared outdoors people. Typical gear includes ice houses and heaters to stay warm, and this may explain the low rate of cold thermal injuries. Also, I think burn injuries and inhalation injuries are often not on people’s radars as potential hazards if they have not gone ice fishing before.”

Those injured most often from ice fishing are largely young and male. This population likely reflects more of the sport’s demographic than those at risk of injury in ice fishing, according to Thiels, noting that young males are at higher risk of trauma-related injury generally, frequently connected to alcohol consumption.

The researchers found greater injury severity with ice fishing compared with traditional fishing, which they theorize may be due to reporting bias or reflect the more severe ice fishing environment. In addition, ice fishing often involves power tools for drilling in the ice and propane space heaters for heating the ice house, both of which can cause serious injuries.

Transfer, as well as admission, is higher with ice fishing injuries, due to the greater severity of ice fishing injuries compared with traditional fishing injuries. Additionally, ice fishing is typically done in rural settings outside of major metropolitan areas, making Level III and IV trauma centers more likely to see these patients, leading to a greater transfer rate to higher levels of care.

While the NEISS database does not reliably capture intoxication rates, the investigators feel strongly from their research that it plays a role in ice fishing injuries. “Ice fishing is a sport that commonly involves alcohol, and this can be a deadly combination,” Thiels says. “Alcohol results in poor judgment and thus does not mix well with being out on the ice, exposed to cold temperatures, working with sharp objects such as knives and hooks, and using equipment such as augers and space heaters.”

“Ice fishing, when conducted in a safe and responsible manner, can be a safe sport, and we are not trying to discourage it,” Thiels says. “However, we do want to help educate the public so that it is aware of the risks and can take steps to mitigate the risks.”

–In-Fisherman

*Thiels, C .A., M. C. Hernandez, M. D., Zielinski, and J. M Aho. 2016. Injury patterns and outcomes of ice-fishing in the United States. Am. J. Emer. Med. 34(7):1258-1261.

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Ecological Insights: Nature’s Stocking Secret

Fishery scientists have long sought explanation for numerous apparently isolated waters that develop fish populations without any access to neighboring fish populations or known stockings. Biologists have speculated that such events may be the result of fish eggs carried on the feet and bodies of water birds or even bait-bucket stockings by anglers. Experiments by European researchers have now provided a clue.*

Fertilized eggs of two species of European carp were fed to mallard ducks. The feces of the ducks were then monitored over the next 24 hours. Eighteen fertile carp eggs were recovered. With one exception, all fertile eggs were recovered within 1 hour of feeding. Another fertile egg was found about 6 hours after feeding. Eight common carp eggs and Prussian carp eggs had viable embryos. One common carp egg and two Prussian carp eggs hatched.

The experiment provides evidence that soft-walled fish eggs can survive passage through the digestive tract of mallards, presumably also through other water-bird species. The authors conclude that survival is not a freak event, occurring in 75 percent of the experimental duck samples and for both carp species. Although only 0.02 percent of eggs survived gut passage, transport stocking by water birds seems likely in nature, given the frequent feeding of ducks and other water birds on fish roe, and the high abundance and diversity of birds likely to eat fish spawn and then fly elsewhere.

This research may help explain the wide dispersal of common carp throughout North America and even re-appearance of carp in some waters treated by rotenone. Further research is needed to confirm the similar colonization of isolated waters by gamefish species like black bass and sunfish.

–Ralph Manns

*Lovas-Kiss, A. and 7 co-authors. 2020. Experimental evidence of dispersal of invasive cyprinid eggs inside migratory waterfowl, A. Rinaldo (ed.) Ecole Polytechnique Federale de Lausanne, Switzerland. https://doi.org/10.1073/pnas.2004805117.

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