In early August we began receiving emails from OTW readers around Cape Cod with pictures of large mackerel taken while targeting bluefish or bonito in Buzzards Bay or off the South Side of the Cape. Just about every email called the fish a Spanish mackerel, but a closer look revealed that every one was in fact not a Spanish, but a juvenile king mack.

When the false albacore arrived on the Cape in force in early September, even more reports of mackerel began coming in. Fishermen found that a slower-than-albie-speed retrieve produced ballistic strikes from mackerel that would launch up to six feet out of the water after hitting the lure. Still many fishermen mis-identified their catches as Spanish mackerel, so here is a quick and easy way to tell which mackerel you’ve caught.

The Cape has a rep for funny fish popping up late in the season, like this random Spanish mackerel Wes caught on a blind cast today. Sounds like we’ll see more, thanks to climate change. From Wikipedia: “With rising water temperatures, the Atlantic (Spanish mackerel) group migrates along the Atlantic coast of the United States from Miami Florida, beginning in late February through July reaching as far as southern Cape Cod, Massachusetts, then returning in fall.” #wildyfishing

A post shared by James Joiner (@jjamesjoiner) on Sep 14, 2017 at 6:31pm PDT

(Social Media Mackerel Mix-up: above – king mack; below – Spanish mack)

Buenas Dias. #spanishmackerel #capecod #fallrun

A post shared by Jimmy Fee (@jamestfee) on Sep 19, 2015 at 5:40am PDT

Juvenile king mackerel and Spanish mackerel can be difficult to tell apart. The characteristic yellow spots that cover the flanks of Spanish mackerel also appear on young king macks. In Cape Cod waters, the fish are of similar size, with most ranging from 3 to 5 pounds, and they are relatively uncommon visitors, which makes it very easy for anglers to confuse one with the other.

If the lateral line of your mackerel makes a sharp dip, you’ve caught a king. The lateral line of Spanish mackerel has a far more gradual dip. Spanish mackerel also have a prominent black spot on their dorsal fin that does not appear on king mackerel. While Massachusetts does not have any size or bag limits on king or Spanish mackerel, in southern states, where king mackerel grow larger and therefore carry a higher minimum size, not knowing which mackerel you’ve caught can put you out of compliance with the fishing regulations.

We don’t know why there are so many king mackerel around Cape Cod this year, but this isn’t the first time they’ve appeared in such numbers. One of the first episodes of OTW TV, filmed in 2002 focused on catching king mackerel while trolling in Buzzards Bay.

If you want to try to catch one, try a slower retrieve and a larger lure when casting around breaking albies. Some anglers reported catching as many as three kings in an outing.