Evaluating Whether Carbonated Beverages Reduce Bleeding and Improve Survival of Esocids with Gill Injuries

By Alexandria Trahan1, John Anderson1, Andy J. Danylchuk3 and Steven J. Cooke1

1 Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental and Interdisciplinary Science, Carleton University, Ottawa, ON, K1S 5B6, Canada

2 The Ottawa River Musky Factory, John Anderson, The Ottawa River Musky Factory 106 County Road 9, Plantagenet, Ontario, Canada, K0B 1L0, Canada.

3 Department of Environmental Conservation, University of Massachusetts Amherst, 160 Holdsworth Way, Amherst, MA, 01003, USA

Autumn skies are upon us and musky are in a flurry to fatten up before winter hits. As you enjoy the time on the water with a stick bait trailing behind the boat, SLAM….your heart is now pounding as you fight that prized Muskie and successfully get it to the boat. Upon landing you notice that one of the gills was nicked by a hook, and the water around the fish is stained with blood. All you can think is, now what? Will the fish survive or is there a way to stop the bleeding? You then recall seeing a video online that went viral not long, showing Mountain Dew being poured over the gills of a bass to stop bleeding. As you look to your cooler for something even close to Mountain Dew, you then also remember the discussion and debate online by anglers, writers and scientists, with some arguing that this is indeed an approach that should be embraced, while others urging caution since no scientific study has been done yet evaluating whether carbonated beverages control bleeding and improve the survival of injured fish. With no resolve, you do the best you can with this particular musky, and end your day hoping that this debate would soon be effectively put to rest.

This is where we come in. For the past few months we have been systematically testing whether a bleeding fish should have a carbonated beverage poured over bleeding gills following capture on hook and line. Although we had hoped to work on Muskies, given their rarity and size, we selected its sister species – northern pike – for the research. Given that we test this on live fish, we first needed to demonstrate that our science had valid purpose, and that our proposed procedures were in line with criteria laid out by the Canadian Council on Animal Care. Specific to our study design was experimentally injuring gills of fish by cutting out a standardized portion of gill filaments from a gill arch (see Image 1), and then pouring a selection of carbonated liquids over the gills to see if the bleeding stopped and for how long (details below).

Image 1: Piece of a gill removed from a northern pike.
Image 1: Piece of a gill removed from a northern pike.

What helped us get approval was that our research would resolve the frantic online debate, as well as provide evidence as to whether pouring carbonated beverages over bleeding gills would improve the outcome for an injured fish if it had to be released.

With a scientific collection permit in hand from the Ontario Ministry of Natural Resources and Forestry, it was time to start with the systematic and controlled evaluation of this longstanding questions. As with any systematic, scientific study, we had to consider and control for as many factors as possible, including water temperature, the size of the fish, and the type, amount, and temperature of carbonated beverage to be poured on the fish’s gills. Given that water temperature has a dramatic effect on the biology of fish, we opted to focus on late spring conditions when water temperature was between 11­-18 C, and late summer when the temperature was 24­-27 C. To then determine what type of carbonated beverage to use, we explored the different social media platforms that revealed the most common beverage being used by anglers on fish – that being Mountain Dew and Coca Cola. We also used plain carbonated lake water as a third liquid to be poured over bleeding gills, allowing us to test whether the additives in the soft drinks made a difference or it was just carbonation. For additional scientific rigor, we included two additional groups ­ one ‘reference’ group where the fish’s gills were cut but nothing was poured on the wound, and the other being a ‘baseline’ group where nothing was done to the fish (it was simply held in a cooler for the same sampling period as the other fish).

For the experiment, fish were angled, landed, and placed into a trough filled with lake water. Fish were then measured and had their gill colour compared to a standardized scale (see Image 2), prior to being selected for one of the five groups mentioned above. Gill colour was recorded because it is relative to the amount of blood loss, with gills full of blood (most common) being bright red, and gills with lower and lower blood flow progressively lighter and lighter, to almost becoming white if fish bleed out.

Image 2. Comparing gill colour of a northern pike against a standardized scale.
Image 2. Comparing gill colour of a northern pike against a standardized scale.

For groups where gill tissue was removed, fish were individually placed in a cooler, and evaluated for relative bleeding intensity and the time it took for bleeding to stop. Relative bleeding intensity was based on the following scale: 0, no bleeding; 1, little bleeding, hard to see; 2, obviously bleeding, easy to see; and 3, intense bleeding, pulsatile blood flow. For the ‘popped’ or carbonated lake water groups, we recorded bleeding intensity immediately before and after a set volume of liquid poured directly onto the wounded gills. This would help us evaluate claims online suggesting that carbonated beverages reduced the amount of the blood loss. For all fish, additional bleeding values were recorded at range of intervals during a 20­-minute holding period. After 20 minutes of holding the vigour and condition of the fish was recorded, and fish that were not moribund were released. To test whether the temperature of the pop makes a difference, we repeated the above series of experiments comparing how bleeding is affected by Mountain Dew at both 4 C (as if the pop just came out of an ice­filled cooler) to 2 C (as if the pop had been sitting in a can in a koozie on the console of the boat for a few hours). We stuck to Mountain Dew for this experiment since it was the most common beverage being used in the videos online.

For both experiments combined we caught and evaluated over 200 northern pike. We are still analyzing the data to determine whether the different carbonated beverage treatments had an effect on bleeding. Stay tuned for more details and whether you are best to keep the carbonated beverages for yourself or to share them with your fish.