Rock Bass vs Largemouth Bass – What’s The Difference?

Largemouth bass and rock bass have many similarities. For this reason many people ask about their differences. Let’s answer, what is the difference between a largemouth bass and a rock bass?

Largemouth bass and rock bass are different species although from the same family. Rock bass is the A. rupestris species, largemouth bass is the M. salmoides species. Largemouth bass has a stronger, fishier flavor than rock bass. Largemouth bass contains more mercury and costs more than rock bass.

This article will compare their tastes, textures, cooking methods, costs, mercury levels and whether one can substitute for the other in recipes. In addition, I’ll do a side-by-side comparison of their habitats, size, weight and nutritional values.

Rock Bass vs Largemouth Bass: Habitats, Size, Weight and Appearance

How can you tell the difference between the two?

The easiest way to tell the difference between a rock bass and a largemouth bass is their body markings, shape and dorsal fin. Largemouth bass have a thicker, longer body compared to the flatter rock bass. Largemouth bass have two dorsal fins, rock bass have one. Largemouth bass have one blotchy, jagged lateral line. Rock bass have multiple black spotted lateral lines.

Other ways to tell the difference:

Rock bass have a tear drop shaped marking under their eyes largemouth bass doesn’t have.
Largemouth bass upper jaw reaches past the eye line. Rock bass jaw doesn’t reach the eye line.
Rock bass have red or orange eyes. Largemouth bass have darker eyes.
Adult largemouth bass average 16″ long. Adult rock bass average 6″ to 10″ long.

Rock Bass and Largemouth Bass Scientific Classifications, Families, Species

Let’s examine their bass species, families, size and habitat.

Rock bass are from:

Family: Centrarchidae
Genus: Ambloplites
Species: A. rupestris
Common nicknames: Red eye, rock perch, goggle eye.

Largemouth bass are from:

Family: Centrarchidae
Genus: Micropterus
Species: M. salmoides
Common nicknames: Green bass, bigmouth bass, largies, bucketmouth.

Habitats

Rock bass are native to North America and can be found from Canada down to Florida and west to Texas. They are mostly found in the eastern and central United States.
When fishing they can be found in streams, ponds, lakes and river basins.
This “bass” species prefer rocky shorelines and vegetation areas. They can be found under docks and near swimming areas.

Bass

Largemouth bass are native to the eastern and central United States, southeastern Canada and northern Mexico. They have been introduced into many other areas as well.
When fishing they can be found in streams, ponds, creeks, lakes and rivers.
This “bass” species prefers warmer waters and murky waters with vegetation. They use logs and similar items as protection.

Fish Appearance

Colors

Rock bass have an olive green to golden brown upper back and sides fading down to a silvery, white belly. They have black spots which form broken lateral stripes down the body. The eyes are red.
- They have the ability to change colors to match their surroundings for protection.
Largemouth have an olive green and gray upper back and body which fades lighter on the sides a white belly. They have dark blotches forming a staggered, horizontal line down the body.

Dorsal Fins

Bass rock has one dorsal fin with 10-13 spines and 11-13 rays.
Largemouth bass has two dorsal fins. The front dorsal fin has 9 spines, and the rear dorsal has 12-13 soft rays.

Anal Fins

The rock bass anal fin has 5-7 spines followed by soft rays.
Large has 3 anal fin spines.

Mouth

The rock bass mouth is large but doesn’t extend past the eye line. The rock bass mouth doesn’t curve upward.
The largemouth bass has a large mouth, wide, and the jaw extends past the eye line. The mouth is protruding and doesn’t curve upward.

Both have teeth inside their mouths.

Body Shape

The rock bass body is flat and is slightly elongated.
The largemouth body have a slender, fusiform (torpedo shape) body shape.

Bass Size and Weight

Rock bass average 6-10″ long and weighs about 1 pound.
Largemouth bass average 15″ long and can weigh up to 20 pounds.

Largemouth bass on average weigh more and are longer than rock bass. Largemouth females weigh more than males the same age.

Bass Lifespan

Rock bass lives up to 8-10 years.
Largemouth bass lives up to 10-16 years.

Bass Diet

Rock bass consume the following:

Insects
Worms
Smaller fish
Minnows
Small crustaceans

Largemouth bass consume the following:

Insects
Small fish
Bluegill
Minnows
Yellow perch
Worms
Snails
Frogs
Crayfish

In a recent article I compared crappie. Find out how these similar sunfish compared in my comparison article.

Watch largemouth bass in their habitat and see how they appear.

Fishing Tips

Some quick fishing tips. Rock bass fishing won’t win many popularity contests amongst anglers. Despite their gamefish appeal, when fishing they are strangely appealing.

When fishing bass they can get caught with almost any angling method. Live bait works extremely well. Fishing within a few feet of the bank is best.

Bass Tastes and Textures

One of the most important things people takes into consideration when choosing a fish is its taste. When comparing the two fish, do they taste the same?

Rock bass has a mild to sweet taste compared to largemouth’s stronger, fishier taste. Largemouth bass may have a fishier flavor depending on the water it was caught in. They both have a firm texture and a little flakey.

Is rock bass fish good to eat? Rock bass is good to eat. Most people are pleased with the mild taste.

To conduct original research, I polled many of my clients, readers and members of food groups I belong to. The following are the results of my poll which consisted of 35 people.

I asked which bass tasted better?

69% preferred the taste of rock bass.
23% preferred the taste of largemouth.
8% said they liked both fish the same.

To conduct more research, I decided to setup my own taste test at home. Both fish were cooked the same and the majority of people had a similar opinion as in the poll.

Bluegill is another sunfish. In my recent article find out which one tasted better in my poll of readers, Bluegill – What’s The Difference? We Compare.

Substitutions: Black Bass?

When preparing recipes for dinner it’s not always possible to locate the type of fish called for. If you have only one or only caught one fishing, you may ask, can I substitute one for the other?

Largemouth bass is not a suitable substitute for rock bass due to its stronger taste and fishier flavor. Although they have similar textures, rock bass fillets are smaller than the largemouth bass fillets. This makes them unsuitable for a largemouth bass recipe requiring a larger size fillet.

Rock bass substitutes:

Bluegill
White crappie
Black crappie
Pumpkinseed
Green sunfish
Lake herring
Tilapia
Pollock

Largemouth bass substitutes include the following:

Salmon
Bluefish
Tuna
Black Sea bass
Mahi Mahi
Walleye

Find out if smallmouth bass can substitute in my article, Smallmouth Bass vs Large: What’s The Difference? Also, find out if their mouths really different?

How to cook largemouth bass.

Smallmouth bass have a different taste. Find out how rock bass compared to them in my article.

Costs

The costs for fresh fish will vary depending on how the fish are caught. When purchasing any fish, be sure to check the label to see if it is wild-caught or farm raised. Therefore, which is more expensive?

Largemouth bass is more expensive than rock bass. The average cost for sunfish fillets is $16 to $22 per pound. Live largemouth bass cost $1.25 per 2-3″ fish. The average live sunfish averages $0.75 to $1 per 3-4″ fish.

I checked online at Walleye Direct and found the following prices:

Wild, crappie fillets (sunfish)
- $22.00 per pound

Seafood Markets:

Wild, sunfish fillets (does not specify which kind of sunfish)
- $18.00 per pound

Dixon Fisheries:

Bluegill fillets (sunfish)
- $14.95 per pound

For stocking ponds, Pond King has the following price per fish:

Black crappie – $1.00 per 3-4″ fish
Bluegill – $0.75 per 3-4″ fish
Hybrid bluegill (green sunfish x bluegill) $0.75 per 3-4″ fish
Largemouth bass – $1.25 per 2-3″ fish

Kevin Garce checking prices of catfish and seafood in his local supermarket. — Checking prices of catfish bass and seafood in my local market

Nutrition

Both are excellent sources of protein, healthy fats, minerals and B vitamins. Both sunfish fish contain the following:

Omega-3 fatty acids
Niacin
Folate
Potassium
Magnesium
B6
B12
B5
Thiamin
Riboflavin
Iron
Selenium
Calcium
Zinc

Fresh water bass provides the following number of nutrients per four raw ounces:

Nutrient	Freshwater bass (4 ounces, raw)
Calories	129
Fat	4.2 g
Saturated fat	0.9 g
Cholesterol	77 mg
Protein	21 g
Omega-3	0.77 g
B-6	0.1 mg
B-12	2.2 mcg
Thiamin	.08 mg
Riboflavin	.08 mg
B-5	0.8 mg
Niacin	1.4 mg
Folate	17.0 mcg
Iron	1.6 mg
Potassium	403 mg
Magnesium	34 mg
Phosphorus	226 mg
Calcium	90.7 mg
Zinc	0.7 mg
Selenium	14.2 mcg

Nutrient Resources ((Nutrition Value: Fish, raw, mixed species, fresh water, bass))¹ ((The Topeka Capital-Journal: Keto, Paleo or Atkins diet? Hunting, fishing can help trim your waistline in 2020))²

They both provide a similar percentage of the same nutrients, except for omega-3 fatty acids. Freshwater bass provides 0.77 g while most smaller sunfish, like rock bass, provide approximately 0.16-0.29 g per 4 ounces.

Keep reading the next section below to find out how the nutrients benefit health, especially omega-3s.

In this article I compared smallmouth to spotted bass. Find out their differences, Spotted Bass vs Smallmouth Bass: What’s The Difference?

Rock Bass and Largemouth Bass Health Benefits

Omega 3 Fatty Acids

The omega-3 fatty acids in both bass help keep arteries healthy and are considered heart healthy. The omega-3s may help with the following:

Lowering triglycerides.
Reduce inflammation.
Reduce plaque buildup.
Keeping bad cholesterol low.
Keeping good cholesterol high.
Help keep the heart rhythms more normal.

DHA and EPA, two of the fatty acids, are associated with lowering blood pressure and improving the health of blood vessels ((National Center for Biotechnology: Marine Omega-3 Supplementation and Cardiovascular Disease)).

Studies suggest omega-3s can help reduce joint pain and stiffness in people with rheumatoid arthritis. They may also boost the effectiveness of anti-inflammatory drugs.

Magnesium

Both bass provide approximately 34-39 mg of magnesium per four ounces. It calms and relaxes the whole body including blood vessels. Magnesium has been shown to help improve sleep related problems like insomnia ((National Institutes of Health: Magnesium)).

Magnesium helps keep blood pressure levels balanced and stable. A recent study researched 22 studies and concluded magnesium supplementation decreased diastolic and systolic blood pressure³.

Magnesium helps control muscle and nerve function, blood sugar and blood pressure.

In the muscles and heart, magnesium competes with calcium to help the muscles relax after contracting. When the body is low in magnesium, calcium can over stimulate the heart muscle’s cells causing a rapid or irregular heartbeat.

B Vitamins

The B vitamins provided by both bass include B1 (thiamin), B2 (riboflavin), B3 (niacin), B9 (folate) B6, B12 and B5. B vitamins help support the following:

Digestion.
Brain function.
Energy levels.
Red blood cells.
Cardiovascular disease.
Nerve function.

Calcium

The two bass provide approximately 85-90 mg of calcium per four ounces. Calcium is important for blood pressure and the heart. Harvard Health reports calcium helps maintain blood pressure because it helps to control the relaxing and tightening of blood vessels⁴.

Calcium also helps the following:

Build and maintain strong bones.
Muscles need calcium to function properly.
Improve nerve function.

Potassium

Both bass provide approximately 357-400 mg. Potassium helps the body get rid of excess sodium which helps reduce fluid build-up. These help keep systolic and diastolic blood pressure lower ((American Heart Association: How Potassium Can Help Control High Blood Pressure)).

The more potassium you consume, the more sodium your body will lose. Consuming too much sodium or not enough potassium throws off the delicate balance the kidneys need to remove the excess water⁵.

According to Harvard Health, a number of studies have shown a connection between low potassium levels and increased blood pressure⁶.

Phosphorus

The two bass provide approximately 203-259 mg of phosphorus per four ounces. It has been shown in scientific research to help with the following:

Promote healthy nerve conduction.
Aides the kidneys in waste removal.
Promote teeth and bone strength.
Muscle recovery after exercise.
Muscle contraction.
Help the body store and manage energy.

Selenium

There are 13-14.2 mcg of selenium per four ounces of both bass. Many people don’t write about the benefits of selenium. I’m unsure why because many studies⁷ show selenium may help to protect the following:

The immune system
Thyroid
Cognitive issues
Heart disease

Mercury Levels

The EPA and The FDA have issued suggestions and warnings about mercury levels in fish and how often they should be consumed⁸. This is especially important for young infants, pregnant women and developing children.

They established three lists:

Best fish
Good choices
Ones to avoid

Therefore, which of the two bass has more mercury?

Largemouth bass have more mercury than rock bass. Freshwater bass has been listed on some states advisory warnings for high levels of mercury. Rock bass is one of the FDA’s best choice of fish regarding mercury levels.

If you’re pregnant, breast feeding or has a young child, Always check with a physician prior to eating new foods or changing your dietary habits.

These mercury warnings can change over time or affect only a particular area or state. Please check with your local EPA and FDA for the current recommendations⁹.

FAQs

Will a largemouth bass eat rock bass?

An adult largemouth bass will eat a smaller rock bass. Largemouth bass consume many smaller fish including sunfish. Largemouth bass can consume fish up to approximately 50% of its body length.