Salmon are amazing fish that fascinate both scientists and outdoor enthusiasts alike. One of the most common questions people have about salmon biology is “do salmon have lungs?” At first glance it may seem like these athletic fish should breathe air using lungs. But the reality is that salmon have a completely different respiratory system adapted for underwater breathing.
In this article we’ll take a deep dive into how salmon really breathe and extract oxygen from the water. Read on to learn all about the unique anatomy salmon use to breathe through their gills instead of nonexistent lungs.
Why Salmon Don’t Have Lungs
Let’s start with the clear answer to our original question – no, salmon definitely do not have lungs Lungs are respiratory organs used to breathe air, which are found in terrestrial animals like humans, reptiles, birds and some amphibians
Fish like salmon live entirely underwater, so lungs would not provide any respiratory advantage. Lungs are designed to extract oxygen from the air we breathe. Salmon have to obtain oxygen dissolved in the water around them instead. That’s where their specialized gills come in.
When people ask “do salmon have lungs?”, they are likely imagining the fish coming to the surface and taking breaths of air. But gills allow salmon to breathe using the dissolved oxygen in water, not the oxygen gas in air. So lungs would be completely useless to a salmon!
All About Salmon Gills
Since they don’t have lungs, salmon rely on their gills to obtain the oxygen they need. Salmon have gill structures located on each side of their heads. The gills themselves are covered and protected by a bony gill covering called the operculum.
Underneath the operculum, the gills are composed of filaments containing many tiny blood vessels. As water passes over the gills, dissolved oxygen in the water moves across the extremely thin membranes of these blood vessels. The oxygen then enters the fish’s bloodstream, while carbon dioxide waste exits the blood and is released into the passing water.
To maximize gas exchange, the gills contain a huge surface area of tiny blood vessels. This makes the salmon’s gills extremely efficient at extracting oxygen from the surrounding water.
Why Gills Beat Lungs for Salmon Respiration
There are several key reasons why gills are far better suited to salmon than lungs would be:
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More Efficient Gas Exchange – Gills can absorb 80-90% of the available oxygen from water, while human lungs only utilize about 5-25% of the oxygen in air.
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Constant Water Flow – As salmon swim, new oxygenated water constantly flows over their gills. Lungs rely on tidal breathing movements.
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Rapid Diffusion – Oxygen diffuses from water into blood across gills extremely rapidly. The diffusion from air into blood across lung membranes is much slower.
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Huge Surface Area – The extensive surface area of dense gill filaments creates a massive interface for gas exchange. Lungs have a smaller absorptive surface.
So while salmon definitely don’t have lungs, their perfectly adapted gills allow them to extract ample oxygen from the water efficiently. Lungs would be largely useless to salmon living underwater!
How Do Salmon Use Their Gills To Breathe?
Actively moving water over their gills is key for salmon to breathe with their unique anatomy. Salmon accomplish water flow across their gills in two main ways:
1. Ram Ventilation
As salmon swim forward through the water with their mouths open, water flows directly into the mouth, over the gill structures, and then exits the gills through the openings behind the operculum. This ram ventilation constantly provides the gills with fresh oxygenated water.
2. Buccal Pumping
Salmon can also actively pump water over their gills by contracting their mouth and throat muscles in a process called buccal pumping. This buccal pumping allows salmon to irrigate their gills even when stopped or swimming slowly.
So salmon breathe either by swimming forward with an open mouth to ram ventilate, or by actively pumping water when stationary. Both methods achieve the crucial water flow over the gills.
Special Respiratory Adaptations in Salmon
Along with their specialized gills, salmon have other unique evolutionary adaptations to enhance their underwater breathing:
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Salmon can alter their gill surface area by growing more or larger filaments to meet oxygen needs.
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As smolts preparing to migrate to the ocean, salmon gills undergo changes allowing them to extract oxygen from saltwater.
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Aerobic muscle tissue near the gills and heart stores oxygen to support swimming and migration.
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Hemoglobin in salmon blood has modifications to efficiently transport and release oxygen.
Thanks to their highly adapted gills and other specializations, salmon can meet their high oxygen demands in both freshwater and marine habitats.
Frequently Asked Questions About Salmon Respiration
Can salmon breathe air?
No, salmon rely entirely on their gills to obtain oxygen and cannot breathe air. They may gulp air at the surface but only to fill their swim bladder, not for breathing with nonexistent lungs.
Do salmon cough, sneeze or hiccup?
No, salmon do not cough, sneeze or hiccup since these actions are associated with expelling air from lungs. However, salmon do exhibit other reflex reactions like vomiting, gagging or thrashing when distressed.
Why do salmon jump out of the water?
Salmon often leap entirely out of the water to cross obstacles during migration or while evading predators. Jumping provides momentum to pass rapids and waterfalls. It may also serve to dislodge parasites.
Can salmon drown?
Yes, salmon can essentially drown if oxygen levels in the water become too depleted. Without sufficient oxygen flowing over their gills, salmon will asphyxiate just like humans would without air.
Do salmon have a sense of smell?
Yes, salmon have an excellent sense of smell thanks to olfactory glands by their nostrils. They use smell to identify home streams, avoid predators, and locate prey. Salmon can detect just a few parts per billion of specific scents in the water.
So while salmon may look like they are stopping to take breaths at the surface, they do not actually have lungs or breathe air. Their specialized gills allow them to obtain all the oxygen they need directly from the water around them. This amazing respiratory adaptation is what allows salmon to thrive in their incredible aquatic environments!
