Yellowfin Herring, Pliosteostoma lutipinnis
The Yellowfin Herring, Pliosteostoma lutipinnis, whose common Spanish name is arenquilla aleta amarilla, is a species in the Longfin Herring or Pristigasteridae Family, known as sardinas machete in Mexico. Globally, there are thirty-eight species in the Pristigasteridae family, that have been placed in nine genera. There is only one species in the Pliosteostoma genus, this fish which is found in Mexican waters of the Pacific.
The Yellowfin Herring have elongated relatively deep compressed bodies that are very flexible, thus giving them an awkward gangly appearance especially when swimming. They are dark dorsally and transition to silvery white ventrally. They have a black spot behind their gill covers. Their fins are yellow. Juveniles have transparent bodies with a silvery mid-flank stripe. They have a large head, a short pointed snout, large eyes, and a projecting lower jaw. Their large oblique mouth extends to mid-eye and is equipped with small teeth located on the roof of the mouth. Their anal fin has a long base and 13 rays and originates before the dorsal fin; their caudal fin is forked; their dorsal fin has 13 rays and originates behind the mid-point of the body; and their pectoral fins are exceedingly long. They have no pelvic fins. They have 15 to 17 gill rakers on their first arch and 27 or 28 scutes along their belly. Their lateral line is complete and extends into the caudal fin base. Their body is covered with rough scales.
The Yellowfin Herring are a coastal pelagic species found over sandy bottoms at depths up to 165 feet. They reach a maximum length of 25 cm (10 inches). They travel in large schools and are known to enter brackish estuaries. They consume zooplankton and small invertebrates including crab and shrimp. Their eggs and larvae are pelagic.
In Mexican waters the Yellowfin Herring have a limited range being found around the tip of the Baja and along the coast of the mainland from Mazatlán south to Guatemala.
The Yellowfin Herring can be easily confused with the Hatchet Herring, Ilisha fuerthii (dorsal fin originates before anal fin origin; small pelvic fins), the Pacific Longfin Herring, Opisthopterus dovii (anal fin originates closer to caudal fin than snout; dorsal fin originates closer to caudal fin than pectoral fins; dark line along back), and the Tropical Longfin Herring, Neoopisthopterus tropicus (very long anal fin base; small pointed dorsal fin; silver stripe along flank).
The Yellowfin Herring are currently considered of Least Concern from a conservation perspective, noting that they have essentially disappeared from the greater Los Cabos area for the last 10 years. They are virtually weightless and of limited value to most. They are retained by subsistence fishermen on a limited basis and used as live bait, for chum, and as cut bait by coastal fishermen.
Yellowfin Herring, Pliosteostoma lutipinnis. Fish provided by the commercial bait salesmen of the greater Los Cabos area, Baja California Sur. Sequence above shows the maturation of the species from juvenile when most of their body is transparent to adult. Lengths: 25 cm (10 inches), 14.1 cm (5.6 inches), and 10.0 cm (3.9 inches).