Spanish Mackerel vs King Mackerel – What’s The Difference?

Spanish mackerel and king mackerel have many similarities. For this reason many people ask about their differences or if they’re the same. Let’s answer, is king mackerel the same as Spanish mackerel?

King mackerel and Spanish mackerel are not the same, they are different species although from the same family and genus. King mackerel are found in deeper water, near Brazil and the Indian Ocean where Spanish mackerel aren’t found. Spanish Mackerel are smaller and weigh less.

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, appearance and compare their nutritional value.

As a Certified Health Coach many of my clients ask me about fresh fish including mackerel. In addition to coaching clients about them, I’ve purchased, researched and consumed both prior to, during and after writing this article.

Spanish Mackerel and King Mackerel: Habitats, Size, Weight and Appearance

When someone is shopping in the market for fresh, whole fish or trying to catch a mackerel in the water, it may not be immediately obvious which type they’re looking at. For this reason, we want to find out a simple method for identifying each one.

How can you tell the difference between the two?

To tell the difference between a Spanish mackerel and a king mackerel is to check their front dorsal fin and lateral body line. Spanish mackerel have a dark spot on the front of the first dorsal fin which king mackerel doesn’t have. The lateral line on a Spanish mackerel gently slopes down while king mackerel’s line sharply lowers a half way down the body.

Other ways to tell the difference between the two mackerel fish are:

• Adult Spanish mackerel have yellow spots on the sides. Adult king mackerel don’t have spots on their sides.
• Spanish mackerel are smaller and weigh less. Adult Spanish mackerel may grow up to 13 pounds while king mackerel can grow up to 40 pounds. Therefore, one over 20 pounds is more likely a king.
• King mackerel may be found near Brazil or in the Indian Ocean where Spanish won’t be found.

It’s important to note juvenile king mackerel, under 10 pounds have yellow spots on their sides which may make one think it’s a Spanish mackerel. Always check the slope of the lateral line and the front dorsal fin to help distinguish between the two.

Scientific Classifications, Families, Species

Spanish mackerels are from:

• Family: Scombridae
• Genus: Scomberomorus
• Species: S. maculatus
• Common nicknames: Spotted mackerel, spotted cybium.

King mackerels are from:

• Family: Scombridae
• Genus: Scomberomorus
• Species: S. cavalla
• Common nicknames: Sierra, cavalla, kingfish.

Both are from the same family and genus but are different fish species. There are other mackerel species which some people confuse with other species. Let’s take a quick look at some of them.

Horse Mackerel

The pacific jack mackerel species was originally called horse mackerel. The FDA allowed the name to be officially changed in 1948 to increase its marketability.

Sierra Mackerel

Sierra mackerel are found in the Pacific Ocean but are a different species than Pacific Chub or Pacific Jack.

Cero Mackerel

Cero Mackerel are found off the Atlantic coast, Gulf of Mexico and South America to Brazil.

Atlantic Mackerel

The mackerel Atlantic is found off the Atlantic coast of the United States in The Atlantic Ocean. They are not the same species as the Atlantic chub mackerel.

Habitats and Fishing

Spanish mackerel habitats

• They are found off the Atlantic Ocean coast of the United States and in the Gulf of Mexico. They are far north as Massachusetts and south down to Florida.
• They prefer shallow waters and sand bottoms in depths from 10 to 40 feet.

King mackerel habitats

• They are found off the Atlantic Ocean coast of the United States, the Gulf of Mexico and South America. They are as far north as Maine and south past Florida down to Brazil. They are also found in the Indian Ocean and the coast of India.
• They can be found in deeper waters from 40 to 590 feet deep.

Before hoping into your boat and go fishing, be sure to check your State park’s education programs and wildlife websites. To catch mackerel fishing, refer to the State or county for any limitations and waters where fishing may have regulations.

Fishing charters are already aware about what fishing regulations need to be followed. They change for each species of fish.

Appearance

Colors

• Spanish mackerels have a greenish back, silver sides and belly. They have yellow or olive green spots on their sides.
• King mackerels have an olive back, silver sides and white belly. Younger ones, under 10 pounds, have yellowish-brown spots on their sides which fade as they grow older and bigger.

Dorsal Fins

• Both have two dorsal fins. Their front dorsal has about 15 spines and the front is taller than the rear. Their second dorsal has about 15 soft rays.

The front of the Spaniard first dorsal fin is black. The front dorsal fin on the king is colorless or lightly colored throughout the whole fin. Some describe it as a grayish pale colored dorsal fin.

Anal Fins

• Both only have soft rays on their one anal fin.

Tail Fins

• Both of them have a deeply forked tail fin resembling a boomerang.

Mouth

• Spanish and king mackerel have sharp teeth inside their mouth on the lower and upper jaws. Both have a large mouth which doesn’t extend past the eye line.

Body Shape

• Both have a long, narrow body which tapers towards the tail.

Scales

• The scales on the Spanish and king mackerel are small.

Size and Weight

• Spanish mackerel averages 19-33 inches long and weighs up to 13 pounds. The females grow longer and weigh more than the males.
• King mackerel can grow to 30-50 inches long and weigh up to 40 pounds or more.

Lifespan

• Spanish mackerel lives up to 12 years.
• King mackerel lives up to 20 years.

Diet

Spanish mackerel consumes the following:

• Small fish
• Anchovies
• Shrimp
• Squid
• Herring
• Menhaden
• Alewives

King mackerel consume the following:

• Squid
• Menhaden
• Clupeidea
• Cutlessfish
• Striped anchovies
• Minnows
• Northern mackerel
• Blue runners

Species resources¹² 

I recently published an article comparing Cero Mackerel. You can check it out and find if it is better.

Tastes and Textures

One of the main reasons people chooses a particular food to eat is its taste and texture. When comparing the two, let’s find out which one tastes better.

Spanish mackerel and king mackerel have a similar medium flavor taste. Their flavor is not considered mild or sweet. Spanish mackerel and king have an oily flesh but Spanish mackerel is a little more oily due to its higher fat content. Both have a similar firm texture which breaks apart into small flakes. 

To conduct some original research, I polled clients, readers and people in food groups. I ask them which mackerel tasted better?

• 72% said Spanish.
• 21% said king.
• 7% said they had no preference.

If you’re interested in how the Atlantic mackerel compared, check out my article. 

Substitutions

When preparing recipes for dinner you may have just one type in the refrigerator ready to be used. In addition, it’s not always possible to locate the type called for in the recipe.

In this situation you’ll wonder if you can substitute one for the other.

Spanish mackerel and king mackerel can substitute for each other due to their similar medium flavors. Their firm textures are similar allowing both fish to be cooked using similar cooking methods. Both of them can be cooked by grilling, searing, frying, broiling or baking. 

Other Spanish mackerel substitutes include the following:

• Tuna
• Bass
• Northern pike
• Catfish
• Bullhead
• Salmon

The king mackerel substitutes are:

• Bass
• Northern pike
• Tuna
• Bullhead
• Salmon
• Catfish

When substituting always stick to the following:

• Same size and weight.
• Stick with similar fillets, whole fillet or cross section.
• Stick with skinless or skin when the recipe calls for one.
• Texture is more important for certain cooking methods. Like using a firmer texture when grilling³.

How To Cook Spanish Mackerel

The most popular ways to cook include:

• Grilling
• Frying
• Searing
• Broiling
• Baking

Flavor pairings:

• Olive oil
• Lemon
• Smoked paprika
• White wine
• Cajun

Find out what taste people preferred, Atlantic or Spanish, in my article. 

How To Cook King Mackerel

Foods For Anti Aging do not recommend consuming king mackerel due to their high mercury levels. Please see the mercury section down further in this article. 

Even though, some people still enjoy eating them and try to use the smaller ones which probably contain less mercury. Some people may find them a little fishy therefore the preparation is important.

Many people soak them in icy water, rinse the fillets and soak it again. Repeat this process until the flesh and the water become clearer.

Popular ways to cook:

• Grilling
• Broiling
• Searing
• Frying
• Baking

Flavor pairings:

• Lemon juice
• Olive oil
• Italian dressing
• Smoked paprika
• Cajun
• White wine

Cost

The costs for fresh seafood will vary depending on how they are caught and where they are sold. When purchasing any seafood, be sure to check the label to see if it is wild-caught or farm raised. Let’s take a look at how much each one costs.

Spanish mackerel fillets cost more than king mackerel fillets per pound. The average cost for Spanish fillets is $19.98 per pound. The average costs for fresh king fillets are $18.97 per pound.

I checked the Fulton fish market online for prices:

• Wild king fillet
  • $18.97 per pound
• Wild Spanish fillet
  • $22.40 per pound

I also checked Citarella online for prices:

• Spanish fillet
  • $20.56 per pound

I checked Fresh Direct online and found the following prices:

• Wild Spanish fillet
  • $16.99 per pound

Nutrition Comparison

Below is a nutrient comparison per four ounces:

Nutrient	King mackerel, raw (4 Ounces)	Spanish mackerel, raw (4 Ounces)
Calories	119	158
Fat	2.3 g	7.1 g
Saturated Fat	0.4 g	2.1 g
Cholesterol	60 mg	86 mg
Protein	23 g	22 g
Omega-3	0.37 g	1.64 g
B-6	0.5 mg	0.4 mg
B-12	17.6 mcg	2.7 mcg
Thiamin	0.11 mg	0.14 mg
Riboflavin	0.54 mg	0.19 mg
B5	0.9 mg	0.8 mg
Iron	2.0 mg	0.5 mg
Niacin	9.7 mg	2.6 mg
Folate	9.0 mcg	1.1 mcg
Potassium	493 mg	505 mg
Magnesium	36 mg	37 mg
Phosphorus	281 mg	232 mg
Calcium	35.1 mg	12.4 mg
Zinc	0.6 mg	0.5 mg
Selenium	41.3 mcg	41.3 mcg

Nutrient Resources⁴⁵

Both fish contain a wide variety of similar nutrients. Spanish mackerel contains more of some nutrients while king contains more of others. Let’s take a close look and determine which is healthier.

Spanish mackerel is healthier than king mackerel due to its higher percentage of omega-3 fatty acids, minerals and lower levels of mercury. The FDA recommends avoiding king mackerel due to its high mercury levels. Spanish mackerel provides more, B1, potassium and magnesium.

It’s unfortunate king contains a high level of mercury because it also provides many beneficial nutrients. It provides more B6, B12, riboflavin, B5, niacin, folate, phosphorus, calcium and zinc.

In addition, it contains less calories, total fat, saturated fat and cholesterol than Spanish mackerel.

I also compared Atlantic Mackerel and Pacific Chub Mackerel in a recent article. Find out which one tasted better in my reader poll, Atlantic Mackerel vs Pacific Chub Mackerel: The Differences.

Health Benefits

B Vitamins

The B vitamins provided include the following:

1. B1 (thiamin)
2. B2 (riboflavin)
3. B3 (niacin)
4. B5
5. B6
6. B9 (folate)
7. B12

B vitamins help support the following:

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

Omega 3 Fatty Acids

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

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

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 boost the effectiveness of anti-inflammatory drugs. In addition, they’ve been shown to help reduce joint pain and stiffness in people with rheumatoid arthritis.

Potassium

Potassium helps the body get rid of excess sodium which helps reduce fluid build-up. The result keeps 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 water⁶.

According to Harvard Health, a number of studies have shown a connection between low potassium levels and increased blood pressure⁷.

Calcium

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 vessels⁸.

Calcium also helps the following:

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

Selenium

Selenium is a nutrient which doesn’t receive much press. I’m unsure why many people don’t write about it more. Many studies⁹ show selenium may help to protect the following:

• Cognitive issues
• Heart disease
• Thyroid
• The immune system

Magnesium

Magnesium helps to calm and relax the whole body including blood vessels. It 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 pressure¹⁰.

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.

Mercury Levels

The EPA and The Food and Drug Administration have issued warnings and suggestions regarding mercury levels in fish and how often they should be consumed¹¹. This is especially important for the following:

• Pregnant women
• Developing children
• Young infants

They established a list of the following:

• Best fish
• Good choices
• Fish to avoid

Therefore, which one has more mercury?

King mackerel has more mercury than Spanish mackerel. Spanish mackerel is listed on the FDA’s good choices of fish regarding mercury levels. King mackerel is listed on the FDA’s choices to avoid list. 

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.

If you’re consuming fish from the best list, The FDA recommends eating two to three servings per week total for adults. From the good choices list, they recommend eating them once per week.

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 recommendations¹².

Another mackerel article I recently published, Chub Mackerel vs Jack Mackerel: What’s The Difference?

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Tuna vs Mahi Mahi – What’s The Difference? Let’s Compare

1. NOAA Fisheries: Spanish Mackerel [↩]
2. Delaware.gov: King Mackerel [↩]
3. Sea Grant North Carolina: Fish Flavors and Substitutions [↩]
4. USDA: Fish, mackerel, king, raw [↩]
5. USDA: Fish, mackerel, Spanish, raw [↩]
6. National Center for Biotechnology Information: The Effect of the Sodium to Potassium Ratio on Hypertension Prevalence: A Propensity Score Matching Approach [↩]
7. Harvard Health: Potassium lowers blood pressure [↩]
8. Harvard Health: Key minerals to help control blood pressure [↩]
9. National Institutes of Health: Selenium [↩]
10. National Center for Biotechnology Information: Effect of magnesium supplementation on blood pressure: a meta-analysis [↩]
11. FDA: Advice about Eating Fish [↩]
12. National Center for Biotechnology Information: Mercury accumulation in largemouth bass (Micropterus salmoides) in a Florida lake [↩]