[Sierra, Spanish Mackerel, Scomberemorus sierra]
This prized eating mackerel is found along the East Central Pacific from Southern California to the northern tip of Chili. It can grow to 39 inches and 18 pounds but the photo specimen was 26 inches long and weighed 3 pounds 1-3/4 ounces. Market size around here is between 15 and 26 inches. This fish has rows of gold dots about 1/4 inch diameter below the lateral line until it descends, but they are often hard to see and never show up well in photos. Red List status LC (Least Concern).
More on the Mackerel Family.
Pacific Sierra is a prized eating fish, milder even than Atlantic mackerel and with excellent flavor - similar to Jacks but more delicate - but perhaps still be too strong for the baby spinach set. It's not good for recipes like pickled mackerel that depend on oiliness and strong flavor, but it does make good Ceviche. Of course it sells at a higher price than other mackerels. The photo specimen was sold at 2017 US $2.49 / pound at an Asian market in Los Angeles (San Gabriel), but it can be higher, often $2.99 / pound, while other mackerels sell at $1.99 / pound or less in these stores.
This fish is mild enough to be used in recipes other than those specifically for mackerel. Pan fried fillets work well, skin-on or skin-off, with just a light dusting of rice flour or sweet potato starch. Of course, you fry the flesh side first, then turn i skin side down. It holds together well enough for wet cooking, if the cooking isn't too long.
If you poach half or quarter fillets skin-on, they will curl quite a bit, then relax a bit as they poach. Serve skin side down and they will flatten out completely. This is an excellent fish for baked stuffed mackerel recipes. In California sushi bars, Pacific Sierra is often served raw as "Spanish mackerel", but several other varieties are used under that same name as well - just depends on what they can get.
Scales: You'll have to be a hungry rabbi with really good eyesight to find any scales on this fish, though it is listed as kosher.
Cleaning: This fish presents no particular problems for cleaning, but watch out for the sharp teeth - dead fish do bite. The body cavity is small and there's not a lot in it, but you will have to cut the esophagus off with kitchen shears. You'll also want to use shears to cut the end of the gills loose under the chin, they pull rather hard.
Skin: The skin is thin but fairly strong. When pan fried it shrinks moderately, pulling the fillet thicker, then loosens and blisters. By this time the fillet has taken a set and will remain thicker. Unlike other mackerels, the skin is fairly strong, so it's possible to remove it using the long knife and cutting board Method, and almost no flesh will be lost. Most mackerel recipes are skin-on, because the skin helps keep the tender flesh from flaking apart. The skin does not have a strong or "off" flavor.
Fillet: This fish is easy to fillet because it has a logical and easy to follow fin and bone structure. I find it easier with the head removed before filleting. Tilt the knife sharply under the gill covers to get the maximum amount of flesh. Work gently with a minimum of bending as the flesh is very tender. The rib cage bones rake sharply back and are very thin and fragile, and tend to pull out of the flesh as you clean the fish.
When you've filleted down to the backbone, work steeply over the backbone at the tail and forward to avoid losing flesh. When I get to the rib cage I just cut the ribs from the backbone with kitchen shears and pull them from the fillet - if they haven't already fallen out.
You'll find a row of centerline pinbone bundles that need to be pulled for nearly one third the length of the fillet. They pull a little hard so hold the tender flesh in place with your fingers and pull straight forward with your long nose pliers. Beyond the first third you can still feel them but they're too soft to worry about.
Yield: A 3 pound 1-3/4 oz fish yielded 2 pound 7/8 ounces of skin-on fillet (66%). That's extraordinarily high, but consistent even with smaller fish I've filleted. Skin off it would still be about 1 pound 14 ounce (61%). The thin skirt area can sometimes have a slight bitterness, but if you choose to cut it away, it is small and you won't lose much.
Stock: Unlike most mackerels, the heads fins and bones make an reasonably inoffensive soup stock (see Method). It may still be a little "fishy" for some tastes, but fine for others. There will be little oil, but do carefully remove what oil there is - use your gravy separator.