The Anatomy Of A Fish

It’s hard to beat the feeling (and the smiles that follow) when you put a hook N1. After all, who doesn’t love catching fish? But, when it comes to fish anatomy, they are as equally fascinating as they are to catch.

There are thousands of fish species all over the world. Fish are cold-blooded animals, which means that in most cases, their body temperature can change to mirror the temperature of the water they live in.  

A Fish’s anatomy can be divided into external and internal. Let’s start by examining the external anatomy of a fish.

External Fish Anatomy

The external anatomy of a fish includes the fins, scales, gills, eyes, nares, mouth, lateral lines and vents. Let’s take a look at each.

external fish anatomy diagram

External fish anatomy (smallmouth bass)

Fins

The fins of a fish are appendages used to move, steer, stop or position. The fins also give the fish balance in the water. The fins could be single fins (such as the anal fin, the back or dorsal fin, and the caudal or tail fin) or paired fins (they include pelvic or hip fins and pectoral or chest fins) along the centerline of the fish.

Certain fish, such as the catfish, have an adipose fin which is behind the dorsal fin. The purpose of the anal fin and dorsal fin is to help the fish conveniently roll over to their sides.

The caudal fin, on the other hand, allows for propulsion as the fish moves forward. Lastly, the paired fins allow the fish to steer, stop, and hover around.

 

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A lot of freshwater fish have spines that support their fins. These rigid spines can be very sharp, thus playing a defensive role in protecting the fish from danger. The catfish, for example, has sharp fins in the dorsal and pectoral area and anglers should be aware and careful when handling these fish.

In some species, the number of spines in the dorsal fin actually helps differentiate between two species, as is the case with white crappie and black crappie

Dorsal fins and caudal fins, on the other hand, have rays which are frequently branched and are less rigid.

Scales

Most bony fish have scales that are either cycloid or ctenoid, except for a few such as the catfish, which doesn’t have a scale, or the gar which possesses ganoid scales.

Cycloid scales have edges which are smooth and rounded while ctenoid scales have edges which are jagged.

To prevent infection, most of the fish have a mucus layer which covers the body. It is important that anglers who intend to return a fish to the water, be very careful with the way they handle the fish, so they don’t mistakenly rub off this mucus layer from the fish. Wetting your hands before handling the fish can help reduce the likelihood of damage to the mucous layer.

Lateral Line

The lateral line in the fish is a group of organs that helps the fish sense the pressure of currents and movement in the water. It consists of a “line” of sacs filled with fluids. These sacs have sensory apparatus which open to the water by means of pores which creates a line along the side of the fish. The lateral line helps the fish sense other fish as well as prey.

fish lateral line

The lateral line of a fish

Gills

Fish gills are very delicate and sensitive structures that allow fishes to breathe while they are underwater. The fish gills have a bright, red color because they are highly vascularized. The gills are protected by a gill cover (operculum) which is a flexible, bony plate. To breathe, the fish takes in water through the mouth, which passes through the gills and is removed from beneath the operculum. 

Eyes

Fish have well-developed eyes to detect varying colors. While mammals achieve focus by the changing shape of the eye lens, fish achieve focus in the water by the in-and-out movement of the lens.

 

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Nares

The nares are a pair of nostrils which the fish uses to detect odors in the water. These nares are very sensitive. Fish like catfish and eels have a sense of smell that is well developed. Fish that live in water that is dark or murky, tend to rely on smell more heavily than fish in clearer aquatic habitat. Fish can also use their sense of smell to detect chemicals in the water, which may indicate predators or even help a fish to locate a mate.

Mouth

The shape of a fish’s mouth can dictate the kind of food the fish eats. For example a fish with a larger mouth will tend to have larger prey.

Fish have a good sense of taste, and in some cases, they can taste their prey even before they swallow it. Some fish are omnivores, like many freshwater fish in Florida. Other fish are mainly piscivorous, which means they feed mainly on other fish.

There are also some fish, such as grass carp, that are herbivores, eating plant life. Depending on the species of fish, some may have teeth while others don’t. Some fish, such as the gar or chain pickerel, have canine-shaped teeth. Others, however, like the catfish have cardiform teeth, which feel like a rough area in the mouth.

Some have vomerine teeth, which are like tiny patches of teeth in the roof of the fish’s mouth. Others, such as the grass carp have pharyngeal teeth which are located in the throat.

The anatomy of a fish’s mouth can affect what type of hook to tie in fishing for particular species of fish.

Vent

In most fishes, the vent is in front of the anal fin. The vents are external openings which open to the reproductive and digestive tracts of the fish.

Internal Fish Anatomy

Internal fish anatomy consists of the spine, spinal cord, brain, swim bladder, kidney, stomach and intestines, vent, liver, heart, gonads, muscles and pyloric caeca. Let’s take a look at each below.

Spine

fish skeleton

fish skeleton

The spine serves as the primary structural framework of the fish. The fish anatomy as a whole is built upon the spine. The spine also connects to the tail of the fish at the rear and the skull of the fish at the front. Numerous hollow vertebra helps to house and protect the spine of the fish.

The skeleton of the fish can be made of either bones or cartilages.

Spinal Cord

The spinal cord of the fish is connected to the brain of the fish as well as to the rest of the fish’s body. It carries sensory information from the body to the brain and also relays instructions from the brain to the rest of the body.

Brain

It is in the brain that sensory information is processed. This is the center of control in a fish. In the brain, automatic functions such as respiration as well as other behaviors are controlled.

Swim Or Air Bladder

The swim bladder is a hollow organ which the fish uses to conserve energy. The swim bladder functions much like a human lung. The fish draws oxygen into the bladder that has been drawn from the water by way of the fish’s gills. The more oxygen the sac holds, the more buoyant the fish becomes.

Conversely, when the bladder releases oxygen, the fish becomes less buoyant, which allows it to sink to deeper water.

The fish can use the swim bladder to to suspend itself in the water, thus saving energy.

Because of atmospheric pressure difference between the water surface and deep water, fish which were caught from deep waters will need to have some air released from their body before they can return to the deep water.

Some species of fishes, however, do not have swim bladders and because of this, they can sink if they stop swimming.

Kidney

The kidney is a part of the fish anatomy that aids a fish in discharging waste from the body. Waste materials in the blood are filtered by the kidney and then removed from the body. The kidneys also help to regulate the concentration of water and salt in the body of the fish. 

Stomach And Intestines

The stomach and intestines of a fish play an important part in the fish’s survival. They help to break down ingested food and to absorb the nutrients. Some fish have short intestines because the food they take is easy to digest. Other fish, such as the herbivores, have longer intestines that help them break down the food they eat.

Pyloric Caeca

The pylori caecum is situated at the junction of the intestine and stomach. It has finger-like projections. Although the function of this organ is not completely understood, the organ has been known to secrete enzymes that help in digestion.

Vent

The vent is the site where waste is excreted from the body of the fish. During spawning, the vent serves as an outlet for eggs and sperm.

Muscles

fish muscle filet photo

fish muscles (filets)

The muscles of the fish help the fish to move in the water. The fillet of the fish, which is generally the part of the fish that is eaten, is comprised primarily of muscle. Anyone who has ever caught a fish and had it flip out of your hand has experienced how powerful a fish’s muscles can be.

Liver

The liver is another important organ with various functions. The liver supports digestion by means of secreted enzymes which break down fats. It also helps to store carbohydrates and fats in the body of the fish. Old blood cells are destroyed by the liver to maintain the blood chemistry of the fish and the liver also helps in the excretion of nitrogen or waste.

Heart

The heart of the fish helps in blood circulation. Through the blood, various cells and organs of the fish receive digested nutrients and oxygen. Waste products are also transported by the blood to organs such as the kidney and liver for removal. This function is made possible by the heart.

Gonads

The gonads are the reproductive organs of the fish. They produce sex cells in the fish. Female fish produce eggs by means of paired ovaries while male fish produce sperm by means of paired testes. The gonads of the fish are located in the same general location. The eggs of some fish are considered a delicacy in certain parts of the world.

Conclusion

Whether you eat the fish you catch or practice catch and release, we hope you have learned a lot from this article about fish anatomy. And, of course, we hope you put a hook N1! You can also view fishing tips videos and read our articles on all types of fishing topics.

And, if you love reading about anatomy of wild game, be sure to check out our article on deer anatomy

east tennessee fly fishing pic

East Tennessee Fly Fishing Surprise

The following is how my wife turned her pick-pocket skills into an East Tennessee fly fishing surprise and an N1 Moment for me. 

Fly Fishing experience?

I had dabbled in fly fishing while in college, but I hadn’t done it in years and would still be considered very much a rookie fly fisherman.

Then, in 2013, while on a family vacation to Sevierville, Tennessee, my wife surprised me with a guided fly fishing trip. She had arranged for me to go on an all-day, smallmouth bass fishing float with Frontier Anglers TN

Smallmouth bass fishing is fun. They are very aggressive fish and are a blast to catch. But, when you put a hook N1 with a fly rod, the experience goes to another level. 

Frontier Anglers TN owner, Josh Pfeiffer, was my guide on this extremely hot July day. But, although the weather was sweltering hot, the fishing was hot as well.

Unfortunately, in addition to hooking several nice smallmouth, I also hooked Josh’s hat 3 consecutive casts (I told you I was a fly fishing rookie, remember?) Thank goodness for patient fishing guides. 

I tucked that trip away in the unforgettable outdoor moments files, but didn’t fish the area again… until 2018. And, this trip was as much of a surprise as the last one!

East Tennessee Fly Fishing Surprise

It was Father’s Day, 2018. My wife and two daughters gave me a few gifts like they do every year. The last gift was an envelope. I opened it up, and inside was a gift certificate for… you guessed it, a fly fishing trip with Josh Pfeiffer. And while I was certainly excited about getting to go fly fishing again with Josh, there was more to the story… 

About a month prior to receiving this gift, I thought it would be great to contact Josh and see if we could set up a time to do a little fly fishing and film some instructional fishing videos. Even after 5 years, I still had his business card in my wallet. So, I emailed him to see what he thought of my idea. He emailed me back and said he might be interested in working something out. But, I got sidetracked and never closed the deal. 

My pick-pocket wife

My wife, who had no idea I had been communicating with Josh, thought that sending me fishing for the weekend would be a great Father’s Day idea. But, she couldn’t remember anything about who had taken me five years earlier. So what did she do? She went through my wallet, of course!

She found Josh’s business card and called him to book the trip. I later asked Josh if he thought it was strange that both my wife and myself were separately contacting him. He said he wasn’t really sure what to think, so he didn’t say anything to my wife. Smart man. 

Fly Fishing with an old friend

So, a few weeks later, I was back on the water with Josh, five years removed from my last fly fishing trip with him. On this second trip, we fished for trout. And just like the previous trip, Josh’s knowledge of East Tennessee fly fishing didn’t disappoint. Over a two day span, I caught close to 30 rainbow trout. And while I love to put a hook N1, that was only part of what made the trip so special. 

I wanted to go fly fishing again with Josh. My wife wanted me to go fly fishing with Josh. But, neither of us knew what the other was thinking. What resulted was a great surprise, a few laughs, and some great fishing.

I thought to myself, you know, this is what we always say at N1 Outdoors. It’s not the size of the fish or the wild game. It’s the unforgettable moments and memories that are made outdoors with friends and family. That’s what we love to celebrate. This trip was no different. 

I’ll do some East Tennessee fly fishing again… and this time it will be a lot sooner than five years!

-By Giles Canter

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Catfish Noodling

If you want to see pure outdoor joy, watch these catfish noodling videos of our friends, Andrew Urban and Luke-Avery Urban and “Aly from Alabama” as they noodle some huge catfish! These videos will make you smile… we promise!

After watching these, you’ll understand why we decided it was time for us to try noodling (be sure and read about that trip below!) You can also read about some other noodling adventures and learn about some other interesting names for noodling.

 

(Andrew’s Catfish Noodling video transcript)

Catfish noodling joy

I think we might get him. Got him! Holy crap! Look at that, son! Look at that! Whoo! That’s a cat daddy right there, boy!

Shake it boy! Look at that. That’s a big boy. Hold him above your head if you can. That is a nice cat!

 

In this noodling video, Andrew’s brother, Luke Avery-Urban, puts a hand N1! Check out this incredible catfish noodling video!

 

(Luke-Avery’s Catfish Noodling Moment video transcript)

Another Catfish Noodling Video Moment

Luke’s under there. He’s got a fish hitting. Let’s see what he’s got. Whoo! Yeah baby! Yeah baby! C’mon… c’mon. I got you. Who’s your daddy?

 

Watch our friend Aly noodle a huge blue cat below!

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(Aly From Alabama’s Catfish Noodling video transcript)

Aly From Alabama Noodles Big Blue Cat

It’s a big, big fish. It’s a big blue, I think. Or, a good size flat. It bit me good. It’s got to be a blue.

I can’t get my hand in its gill. I wish you could feel this fish right now. Can’t tell what’s going on.

It just swallowed my whole hand! My whole hand is in its stomach. It’s starting to go crazy.

That’s big blue. I didn’t even think it was a blue. It swallowed my whole hand like that.

It stinks! She’s a stinky one.

 

What Is Noodling Anyway?

Watching catfish noodling videos like the ones above from the Urban brothers and Aly from Alabama made me want to put a hand N1 too! What was it about sticking your hand into dark holes where you couldn’t see anything and hoping something huge would bite your hand?

blue catfish noodling pic

Some call it hand fishing. Some call it grabbling (or grabblin), and some call it noodling. We weren’t sure what the buzz was all about, but we were fascinated to find out.

So, we scheduled our first noodling trip with Luke-Avery Urban on Clarks Hill lake in Lincolton, Georgia.

But first, a limit out

Luke-Avery was generous enough to spend the whole day with us, teaching the N1 Outdoors audience how to fish for striped bass and hybrid bass. So, we spent the first part of the day striper fishing and it turned into a striper and hybrid limit

Once we had limited out on striped bass and hybrid, we were off to some boat ramps that had produced some quality noodling trips over the years for Luke-Avery. 

Catfish spawning

Spawning time is the optimal time for noodling catfish. We learned that water temperature is key in learning when the catfish spawn happens. The female lays her eggs in hollow logs, crevices or caverns under the bank, and in holes or openings under boat ramps, which is where we would be searching.

Once the female catfish lays her eggs, the male guards the nest fiercely until the hatch occurs. We found out that they will bite down hard on anything entering the nest!

Optimal water temperatures for blue catfish is 70-84 degrees, while some believe that 81 degrees is the magical temperature for blue cats. Most believe that the flathead catfish spawn an temperatures of 66-75 degrees. Whatever the perfect temperature is for each, we were able to experience both species in one outing! 

Hurt at first bite

At our first stop, I got to experience what it feels like to get bit on the hand when trying to noodle a catfish for the first time. I learned quickly that it’s best to keep your fingers together when noodling. The first bite was actually on just my little finger. It sure didn’t feel very good! If you have never experienced how strong the mouth of a catfish is, noodling will help you understand!

Luke-Avery said he’s taken a lot of grown men noodling and most of the have yelled underwater the first time they get bit. I was determined to not do that. But, I will say I was certainly startled. 

I tried multiple times to grab the catfish in that first hole and just could get a grip fast enough. Finally, Luke-Avery said to let him try. He stuck his hand into the hole and got bit as well. When he came up he said, “that’s a blue cat. They bite harder than a flathead catfish does.” (Flathead catfish are sometimes referred to as mud cats, yellow cats or shovelhead catfish.)

catfish noodling giles picWe left that hole and moved farther down the boat ramp. Eventually, we were both diving down in 10 feet of water checking other holes. Luke-Avery was able to pull out a nice blue cat.

My first catfish noodling success

When we left there, we went to another ramp where Luke-Avery had noodled some 40+ pound catfish in prior years. We got bit several times but were having trouble landing any cats. Finally, I was able to get a hand N1 and land my first flathead catfish! It was a rush for sure!

I found out that noodling was definitely worth all the hype and I can’t wait to put a hand N1 again!

Another Catfish Noodling storycatfish noodling man

Summer is upon us and in Southern Illinois, and that means it’s time for catfish to start spawning, which means noodling! Catfish swim up in holes under all sorts of things such as stumps, boat ramps, and rocks.

With noodling, the first thing you do is feel around with a stick in the hole because fish this big will be in holes 15, maybe 20 feet, back. We found a big flathead catfish under a boat ramp and we knew it was time to Noodle1. So, I went under the murky water and put my arm in the hole, waving it around inside there and… Bam, I got bit!

So, I grabbed its bottom jaw and ripped it out of the hole while putting my other hand under it. We ran a stringer in it to see how big it was once he broke the surface. It was a monstrous 40+ pounder! I’ll never forget the day I put a hand N1! 

– By Charles Farmer

So, Can I Go Noodling For Catfish In My State?

You may have watched these videos and read these stories and said, “There’s no way I’m ever doing that!” But, you might love experiencing the thrill of catching a catfish with your bare hands and wonder, “Is noodling legal in my state?”

According to Wikipedia, as of 2002, noodling was legal in 12 states in the U.S.

If you live in one of the following 15 states, you may be ready to put a hand N1! (But, be sure to check your local game laws for legality and restrictions.)

• Alabama

• Arkansas

• Georgia

• Illinois

• Kansas

• Kentucky

• Louisiana

• Maryland

• Mississippi

• North Carolina

• Oklahoma

• South Carolina

• Tennessee

• Texas

• Wisconsin

Have fun, be safe, and put a hand N1!

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