BISMARCK, N.D. (KXNET) — As temperatures rise around North Dakota, many people look to head out into the great outdoors and hit the water, in one way or another. In an area like ours, where there aren’t any coastal beach parties, visiting smaller bodies of water is the go-to plan for water activities. Among the most popular of these is fishing — and during the summer, armies of anglers head down to local lakes in search of a prize catch.

This sudden surge of summer seafood searchers does, however, come with more side effects than anticipated. While we all know the impact of fishing on aquatic populations and keep it under control with limits provided by the Department of Game and Fish, there is a second, unexpected threat to the population caused by fishermen: barotrauma, a condition that continues to haunt fish who are released back into the water after a successful catch. The situation has become particularly bad in some locations around North Dakota, to the point where the DGF has issued calls for anglers to harvest everything they catch, and to try and avoid catch-and-release in general.

These warnings have once again brought concerns regarding Barotrauma to the surface of the public eye — especially in North Dakota’s most lucrative fishing areas. But what exactly is barotrauma, and why is it important to minimize instances of it as much as possible?

Behind Barotrauma

The most common situation where water-based barotrauma occurs is when any organism changes from two areas with different levels of water pressure too quickly. Simply put, as the pressure in an area rises and falls faster than the body can cope with the changes, the pressure can tear away at the skin, bones, joints, and organs.

If you are familiar with scuba diving, it would be easy to compare it to the idea of getting ‘the bends’: damage to the muscular and skeletal systems, fatigue, rashes, and in some cases pulmonary damage to the lungs caused by gas bubbles forming underneath the skin after rapid pressure changes. This is one form of decompression sickness that has many of the same effects as barotrauma — and if it can be dangerous enough to cause damage in humans, it stands to reason that its effects on less-developed organisms like fish can be devastating.

In the case of fish, the rapid changes that cause barotrauma usually happen when they’re caught by anglers, who quickly reel the fish in and force it to the surface. through different levels of pressure. The sudden transition often causes immediate injuries in the sea life as their bodies are unable to cope with their newfound surroundings.

While there are multiple symptoms of the condition that are easy to identify, like bulging eyes and bleeding gills, there are less obvious (but more deadly) aspects of barotrauma that can tear apart a fish from the inside. Hematomas (bruises made of pooled blood), gas bubbles under the skin, twisting of the stomach and intestines, and even internal hemorrhaging can occur as a result of the pressure changes.

Injuries sustained as a result of barotrauma will almost inevitably result in the death of a fish — if not immediately, then certainly when they attempt to return to the water. The most common threats for a returning fish suffering barotrauma are damaged swim bladders, which will often render them unable to right themselves, return to their habitats, or submerge, making them even more susceptible to being picked off by hungry birds, boiled by surface temperature and sun exposure, or struck by nearby boats.

Barotrauma in North Dakota

When taking the idea of barotrauma into account, it’s important to not only consider the environment that fish find themselves in but also the fish themselves. Some fish, like pike and trout, have specialized ‘ducts’ in their body that connect their swim bladders to their stomachs. This allows them to decompress their bladders as they travel through pressure levels, . Many of the fish affected by barotrauma, including walleye, bass and perch, do not possess this duct, meaning that they’re forced to release extra gas through the bloodstream, which is much slower.

A list of some of the fish most affected by barotrauma in North Dakota (Image Credit: ND Game and Fish Department)

Studies performed across the states have noted that the fish displayed above have exhibited greater death rates when faced with angling barotrauma compared to other species. The depth at which barotrauma kicks in varies greatly depending on the fish and lake, but most studies show that the most dramatic changes occur when traveling in a body of water over 33 feet (10 meters) deep.

As many of the shallow prairie lakes here in North Dakota tend not to be deeper than that in maximum depth, barotrauma isn’t a major concern in these fishing holes — but is extremely frequent in deeper bodies of water like lakes (Lake Sakakawea and Devil’s Lake, in particular, have reported many more instances of barotrauma in recent years) or reservoirs year-round. The main change over the seasons here is which fish tend to be the most affected. According to Game and Fish, in the summer months, walleye tend to spread out across the deeper waters, and yellow perch become the main targets of anglers during the winter.

Subpar Saving Strategies

When the topic of avoiding barotrauma comes up among fishermen, there are a few ideas that have been passed around that are widely seen as methods of reducing the damage it does to a catch ready to be released. Unfortunately, according to the Game and Fish Department, these methods are not only unable to guarantee a fish’s survival, but can end up being harmful in themselves. As a result of this, many anglers may be responsible for more killed fish than their legal limit. Here are a few of the most popular rumors of strategies to help avoid barotrauma that may be doing more harm than good.

  • Slow Reeling: A typical slow reel-in for a fish (3-5 minutes) is still not enough time to allow an affected fish without a specialized duct to release enough gas from their swim bladder (estimated to be 20-30 minutes).
  • Descending Devices: Items such as drop weights (which, when attached to a fish’s lip, sinks them back to their original depth and quickly compresses the swim bladder) are often used to ensure a quicker release. While fish returned to the water this way have been noted to swim away quicker, this method only solves the swim bladder problem — meaning that it doesn’t reverse other effects of the pressure change, like internal bleeding or hematomas. These only add to the fish’s death rates even after their release.
  • Fizzing/Venting: This process involves puncturing a caught fish’s swim bladder with a sharp object to quickly release built-up gas and deflate the bladder. While the idea is promoted as another way to quickly return fish to their proper environments, the idea is not promoted by the Department of Game and Fish, who warn that the full effect of fizzing/venting is not fully studied. Furthermore, much like descending devices, this process does nothing to ease the other effects of barotrauma — and can even spell trouble for the fisherman. As the process needs an angler to be holding the fish while the bladder deflates, it can technically create a situation where the angler is in violation of the Game and Fish law that requires fish to be released immediately after capture.

Beating the Barotrauma

Stopping excess Barotrauma comes combined with a limit on catch-and-release fishing. While there is no guaranteed way to end barotrauma damage, the Department strongly advises that when fishing in deep waters, the angler should either keep all catches or instead practice catch-and-release in shallow depths where the threat of barotrauma is not present. For smaller areas that meet the depth requirement, the Department simply advises avoiding fishing in the deeper portions.

For questions regarding proper fishing procedures and more information about the effects of barotrauma in humans, the National Library of Medicine has an article that explains them. More information about barotrauma in fish, in particular, can be found at the Department of Game and Fish’s website.