Whether you call it a king mackerel, kingfish, or by its scientific name, Scomberomorus cavalla, the king mackerel is an incredibly important fish.
King mackerel are the largest macks in the family, and they’re critical to both commercial and recreational fishing and the ocean ecosystem at large.
Today, we will cover everything you could want to know about these impressive fish, from their characteristics and appearance to their lifecycle, reproductive and eating habits, and much more.
Characteristics & Appearance
While there are several different mackerel species, the king mackerel is pretty easy to identify, thanks to its characteristics and features.
Weight & Length
King mackerel are the largest and most prolific of the mackerel species. They’re medium-sized fish, and most specimens are around 24-30” long and weigh about 25-30 pounds.
King mackerel can grow much larger than this, and it’s relatively common to see fish in the 50-60 pound range. The largest-ever king mac was 72” long and weighed 99 pounds.
Physical Characteristics & Color
King mackerel look very similar to other mackerel species, but some differences help separate this fish from its cousins.
The most apparent determiner is their size. King mackerel can grow significantly larger than other mack species, reaching 100 pounds.
Even juvenile kingfish who are roughly the same size as other mackerel species have a characteristic tell; Kings have a grey dorsal fin compared to the blackfin of cero and Spanish mackerel.
The king mackerel has a deep olive-colored back that fades to an iridescent silver through the fish’s body. The belly of the fish is white.
Juvenile kings have small yellowish spots, similar to a Spanish mackerel, disappearing as the fish reaches maturity.
King mackerel have a long, spiny first dorsal fin followed by a second, with tiny finlets along the back and belly of the fish towards the tail.
The fish also has a set of pectoral and anal fins. King macks also have a unique lateral line that begins high on the fish’s body and dips low at the anal fin.
Lifespan & Reproduction
King mackerel can live for twenty years or longer, although it’s rare for a fish to make it this long due to environmental conditions and predation.
This species reproduces aggressively throughout the spawning season, and while many of the reproductive activities of king macks remain a mystery, we’ve developed a fairly complete picture of how these fish reproduce.
During the spawning season, females produce as many as 12 million eggs. The females are much larger than males, which is an evolutionary feature intended to increase reproduction and protect the species’ existence.
With the females being so large, they can produce more eggs. Males reach sexual maturity within three years of birth, with females hitting maturity somewhere after two years.
The females continue to evolve throughout their sexual maturity, reaching their peak at four years.
Once fertilized, king mackerel eggs hatch within 24 hours and grow incredibly rapidly, which helps protect the young fish from predators.
King mackerel can be found up and down the Atlantic coast, and two distinct fish populations exist.
The northern population lives off the coast between Massachusetts and central Florida, while the southern population lives between central Florida, the Gulf of Mexico, and Brazil.
Both populations will migrate up and down the coast, and while some intermingling occurs, the two groups migrate to the northernmost points of their territory during spawning season. The northern fish spawn in the northeast, while the southern fish spawn near Florida.
Where Do King Mackerel Live?
King mackerels prefer to inhabit coastal waters and the outskirts of reefs and are most commonly found between 75-110 feet.
These fish will regularly migrate to inhibit the most temperature waters given the time of year.
King mackerel will regularly congregate in deeper waters along the outer continental shelf during spawning season.
Food & Diet
King mackerel are voracious and opportunistic predators that eat a varied diet depending on their size and maturity.
King macks fall squarely in the middle of the food chain. They’re predators in their own right, but they’re also commonly eaten by larger pelagic species such as dolphins, sharks, and tuna.
What Do King Mackerel Eat?
King mackerel might not be the largest fish in the sea, but they’re voracious and violent feeders known to leap from the water in pursuit of prey.
King mackerel eats a diet primarily consisting of small fish, but they’ll also eat shrimp, mollusks, and squid.
Adult macks usually eat fish 6” in size or smaller, and they tend to attack schooling fish such as anchovies, grunt, and herring.
These baitfish congregate near the top of the water column and travel in massive schools, which makes them an easy target for hungry king mackerel, who ascend from deeper waters to feed whenever the opportunity presents itself.
When threatened, these baitfish school together tightly to protect themselves. But, this action makes it easy for king macks to pick off the weakest members of the school.
While baitfish is their favorite, they’ll pick at shrimp, squid, and mollusks in times where baitfish is less abundant.
Threats & Predators
The king mackerel falls squarely in the middle of the food chain, and they face many different threats from predators, humans, and the world at large.
Humans represent perhaps the largest threat to king mackerel, as it’s an important commercial and recreational fishing species.
The northern and southern populations are fished heavily, and many more kingfish are caught as bycatch as commercial boats target other species.
Climate Change & Global Warming
As climate change and global warming continue to affect the oceans, scientists are still unsure what these changes will mean to the kingfish population.
In response to warming oceans, their populations seem to be shifting north to cooler waters.
So far, the only balance this seems to upset is among commercial anglers, but the loss of habitat may prove detrimental to future kingfish.
Kingfish face several different predators over their lifetime. Juvenile kingfish fall prey to several coastal and pelagic species and are at constant predation risk.
Mature kingfish don’t have to worry about as many different predators, but they’re still a favorite meal of dolphins, sharks, and tuna.
While predators and fishing represent the two most significant threats to king mackerel, they also face some other threats.
Most notably, 23 different species of copepods and worms can affect kingfish. While most are relatively harmless, others pose a danger to king mackerel.
Despite the threats they face, king mackerel have a thriving population, thanks to how frequently the fish can reproduce.
According to NOAA fisheries, both kingfish populations are holding strong and aren’t subject to overfishing. According to IUCN, king mackerel have a conservation designation of “least concern.”
Fun Facts About King Mackerel
If you still have an appetite for king mackerel info, check out these interesting facts about kingfish below.
- King mackerel are relatively small fish, but they can grow to sizes of up to 5’ long and 100 pounds
- Despite almost 17 million pounds of king mackerel being caught by commercial and recreational anglers in 2019, the species is not overfished, and their stock is relatively healthy
- King mackerel can live for longer than 20 years
- King mackerel is an oily fish with grayish flesh and smoking the fish is the most popular way to prepare it, along with grilling or pan-frying
- Juvenile king mackerel possess light yellow spots throughout the body of the fish that disappear when it reaches maturity
- While most mackerel species look nearly identical, only king mackerel have a gray dorsal fin
- King mackerel love to hang out around wrecks, buoys, and reefs and spend most of their time in 30-110 feet of water
- Two distinct king mackerel populations live in the Atlantic ocean, with a northern population from Massachusetts to Florida and a southern population inhabiting Florida, the Gulf of Mexico, and South America