About Porichthys notatus Girard, 1854
Porichthys notatus Girard, 1854, commonly called the plainfin midshipman, is one of the largest toadfish species in the Porichthys genus. This fish reaches a maximum total length of 38 cm (15 in). Its dorsal coloration ranges from brownish and olive to iridescent purple, fading to a lighter shade on the sides and becoming yellowish or golden on the belly; this color pattern can vary by sex. It has a whitish patch and black crescent marking below the eye. Most adult plainfin midshipman lack dark saddle-marks, but when present, there are 6 to 7 of these markings. Juveniles share the adult appearance, but may have a small number of dark saddle-marks. This species has wide pectoral fins and a narrow, rounded tail fin. Four lateral lines run along its head and body sides. It has 33 to 38 soft rays in its long second dorsal fin, 30 to 35 anal fin rays, and 17 to 20 pectoral fin rays. Body size differs between females and the two male morphs of this species. The species is distinguished from other members of its genus by the placement of its photophores. All Porichthys have a set of photophore groups along the sides and underside of the body: branchiostegal, gastric, gular, lateral, mandibular, pleural, and ventral photophores. In P. notatus, the branchiostegal photophore series forms a V-shape. The pleural photophore series ends posterior to the pleural lateral line, a trait it shares with the specklefin and mimetus midshipmen. Porichthys notatus is sexually dimorphic, and also has two distinct male morphs that are tied to different breeding strategies. Females have a standard length ranging from 9.6 to 15.2 cm, and weigh between 11.1 and 47.3 g. Type I males have a standard length of 12.0 to 21.0 cm, and weigh 30 to 206 g. Type II males are smaller, with a standard length of 6.5 to 10.5 cm and a weight of 3.9 to 17.3 g. Body size and mass of all sexes and morphs fluctuate annually; for example, Type I males reach their peak body mass during the pre-nesting season. P. notatus overlaps in range with only one other Porichthys species, the specklefin midshipman (Porichthys myriaster). Specklefin midshipman differ from plainfin midshipman by having bands on the caudal fin (which plainfin midshipman lack) and a U-shaped branchiostegal photophore series instead of a V-shape. Mimetus midshipman (Porichthys mimetus) differ from plainfin midshipman by having 32 to 36 second dorsal fin rays, compared to the 33 to 38 rays of P. notatus. During the nonbreeding season, plainfin midshipman live in moderately deep waters off the Pacific coast of North America, ranging from Canada to Baja California. They can be found from shallow water just below the tide line down to depths of 366 m, and prefer habitats with sandy or muddy bottoms.
