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Do Fish Hooks Dissolve? Here’s How Long It Takes (Backed By Research)

While some fish do die from swallowing the hooks, it appears most hooks either dissolve within a couple of months or are wrestled free by the fish in a matter of hours or days. Keep reading to learn more.

Do Fish Hooks Dissolve In A Fish’s Mouth?

How old do you think fish hooks are? If you guessed 23,000 years old, you would not only be correct but should probably buy a lottery ticket. Fish hooks have been around tens of thousands of years and are even referenced in the Bible in the book of Job.

 While there is no way to know what sort of tales fisherman told back then you can bet they all had a fish or two get away and it left them wondering, “what happened to that fish?”

 Did the fish ever wrestle that hook free? Did it dissolve in the fish’s mouth? Or did the fish eventually die from its punctured flesh? The thing is, we’ve all been there.  We’ve let fish go, or lost fish with a hook still in its mouth or throat.  

 This article aims to answer that age-old question once and for all. But first, a little history …

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History of the Fishing Hook

To first begin to tackle the question of whether hooks dissolve in a fish’s mouth we will take a closer look at fish hooks. Early fish hooks were crafted from a wide variety of materials including wood, horn, stone, shells, animal bones, and even human bones. While you still can find most of those types of hooks the more modern hooks are made of some form of alloy including bronze, iron, high-carbon steel, steel alloyed with Vanadium, or stainless steel.

 From the seventeenth century up until about the middle of the twentieth century the majority of hooks were made of plain steel. These plain steel hooks weren’t of the best quality and easily degraded and rusted away when left in the water. This hook construction made it easier for hooks to dissolve in a fish’s mouth and probably helped spawn the advice that is passed down between generations of fisherman that hooks do dissolve in a fish’s mouth.

 Modern-day fish hooks are not only composed of higher grade alloys, but they are also coated with a thick plating of Teflon and nickel which adds a layer of protection and prevents degradation. As such, modern day hooks don’t dissolve as easily in water or in fish’s mouth.

Biological Research and Results

In the last couple decades, there have been two notable studies on the fate of fish hooks and the fate of the fish they are left in.

Experiment #1: Do fish shed any hooks left in their gullet?

First, a study performed by John Foster, Recreational Fisheries Coordinator for the Fisheries Division of the Tidewater Administration of the Maryland Department of Natural Resources (what a title), on whether fish shed any hooks left in their gullet. His biology team throat hooked medium and large stripers and held them in tanks of ½ seawater and ½ freshwater to mimic their natural habitat and because hooks would dissolve more quickly in full seawater due to the salt content.

Over the course of two experiments, they tested the effects of long-term hook retention using hooks comprised of bronze, nickel, tin-cadmium, and stainless steel by placing them in in the fish’s esophagus. Thirty fish were tested with each type of hook over four months for bronze and tin-cadmium and 60 days for stainless steel and tin.

Results of the first experiment:

  • 78% of hooks remained in the stripers (including fish that died)
  • 80% of the tin-cadmium hooks remained (mortality here was 20% due to cadmium poisoning, and since publication, the hook companies have stopped using cadmium in hooks.
  • 70% of bronzed hooks remained

 

Results of the second experiment:

  • 81% of the hooks remained with a retention rate within a range of 100% for stainless steel down to 56% for tin.  Mortality was even higher on the second test.

 The biology team who ran this experiment carefully examined its findings and recommended the following conclusion: Anglers should carefully remove hooks from deeply hooked fish when possible.

Experiment #2: How long do hooks stay in a fish’s mouth in the wild?

The second study was performed by a Canadian graduate student Chris Pullen under the supervision of Dr. Steven Cooke and the Fish Ecology and Conservation Physiology Lab at Carleton University. Mr. Pullen and Dr. Cooke set out to answer the question of ”how long hooks stay in a fish’s mouth in the wild?”

This study was done entirely on Northern Pike of average size and age which Chris hooked and proceeded to attach four hooks in different parts of the mouth. Then he attached a radio transmitter to the fish and set them free.

The results of the experiment:

  • Deeply hooked crankbaits with barbs were typically free from the fish’s mouth in a couple of days
  • Barbless hooks usually came out of the fish’s mouth in 24 hours or less

Chris’s conclusion was that these fish were great at finding ways to remove the hooks themselves underwater. He recommends any angler wanting to release fish safely are better off cutting the line on a pike deeply hooked then trying to yank the hook out.

Final Thoughts

So, can fish dissolve hooks? Sometimes. From the studies cited in this article and reading the history of fish hooks, it appears it greatly depends on the composition of the hook, the type of hook, freshwater vs. saltwater conditions, and the type of fish. While some fish do die from swallowing the hooks, it appears most hooks either dissolve within a couple of months or are wrestled free by the fish in a matter of hours or days.

Do you leave hooks in the fish? Why or why not? We’d love to hear your opinion in the comments below.  And share this with your fishing buddies if you were surprised as I was!

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Written by Don

When I'm not bass fishing or looking for steelhead in my home state of Oregon I can be found working on house projects dreaming of my next fishing adventure.

I started this website to share just some of the things I've learned along my fishing journey, and the many things I'm still learning. Enjoy!

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