Porichthys notatus

This fish reaches up to 38 cm (15 in) in length, and is one of the largest of the Porichthys toadfishes. It is brownish to olive to iridescent purple dorsally, becoming lighter on the sides and yellowish/golden on the belly, though this can depend on sex. Below the eye is a whitish patch and black crescent. Adults usually lack saddle-marks, but there are 6-7 saddle-marks if they are present. A young individual looks like an adult but may have a few dark saddle-marks. P. notatus has wide pectoral fins and a narrow but rounded tail fin. However, all sexes experience annual fluctuations in body size; for example, body mass peaks for Type I males during pre-nesting season. Similar species include: • Specklefin midshipman (Porichthys myriaster), which differs from the plainfin by bands on its caudal fin that the plainfin lacks and U-shaped branchiostegal photophore series. This is the only other Porichthys species with which the P. notatus overlaps. • Mimetus midshipman (Porichthys mimetus), which differs from the plainfin in that it has 32-36 second dorsal rays instead of 33-38 in the plainfin, as well as. ==Habitat and behavior==

During the nonbreeding season, the plainfin midshipmen typically inhabit moderately deep ocean waters off the Pacific coast of North America, from Canada to Baja California. They can range from shallow water just below the tide to depths of 366 m and prefer sandy and muddy bottoms. Diet Its diet includes crustaceans and fish. As juvenile, they feed on small crustacean larvae and zooplankton. They can be found by lifting up rocks or logs in the intertidal zones during this season. The Type I male claims a nest site, which is generally under a rock or boulders in the intertidal zone. Once underneath, he digs out a cavity using his pectoral fins. A female will come seeking out males—attracted by his vocalizations—to deposit her eggs in his cavity. The male may attract more than one female and end up with over 1000 eggs in his nest. The male tends them by fanning them, keeping the nest clean, and hydrating them if they begin to desiccate at low tide. He protects the larvae post-hatching until they reach their juvenile stage and leave the nest, about 45 days after fertilization. Type II males are consistently smaller in size than Type I. The ratio of gonad weight to body weight of Type II males is on average nine times greater than that of Type I males. It can "breathe" air. Physiologically, it is well adapted to hypoxia, as well as hypercapnia. Even its sperm are quite functional in low-oxygen conditions. The eggs take about 16-20 days to incubate. After hatching, the embryos remain attached to the cavity wall by the yolk sacs for about a month, after which they will detach and bury in the mud. The juveniles are still nocturnal and will bury in the mud during the day and feed at night. They will gradually make their way back to the water. ==Bioluminescence==

P. notatus is bioluminescent. It has photophores in the skin of its head and much of its body. One fish has over 700 photophores, each about a millimeter wide. They contain luciferin. Norepinephrine activates them, producing a distinct fluorescent green glow. The fish is only luminescent during courtship. It may play a role in predator avoidance and potentially attracting prey, as well. In the juvenile, photophores point ventrally, directing their illumination downwards. This helps to shadow the fish in a silhouette that might make it harder for predators to see. Not all individuals express this trait. There are two main populations of the species, a southern population found as far north as San Francisco, and a second population extending to the northern reaches of its range. ==Vocalization==

Both male and female of the species produce vocalizations. The female may produce a brief grunting sound, usually in agonistic encounters. The Type II male performs similar behaviors to the female. The Type I male is much more vocal, both in conflict situations and in courtship. He utters long strings of shorter grunts and growls while fighting, but his courtship call is more of a prolonged hum. This sound is only produced at night. He may produce this sound for over an hour at a time, reaching frequencies near 98-106 Hz. When a male makes the sound, gravid females respond by moving toward him. The fish produces the sound using the muscles of its modified swim bladder. and in the San Francisco Bay Area there are noisemaking populations. The fish is notorious in Sausalito, California, where a community of people live on houseboats. The resident population of the fish becomes very obvious during the breeding season, when it spends the night vocalizing so loudly it keeps the houseboat residents awake. Its calling is most intense between midnight and 6:00a.m. Despite its annoying behavior the fish inspired an affectionate local tribute in Sausalito, the Humming Toadfish Festival. and "an orchestra full of mournful, rasping oboes." ==Predators==

s and other birds will catch and eat plainfin midshipman It is eaten by seals, sea lions, otters, mink, crustaceans, fish, etc. This fish is an important prey for the bald eagle in some coastal areas, being the most common food provided to eaglets by their parents in one study on Vancouver Island. This is a concern, as this fish has been found to contain relatively high levels of contaminants, such as dioxins. It is also prey for the northwestern crow, the glaucous-winged gull, and the great blue heron. P. notatus is host to the parasitic copepods Lepeophtheirus remiopsis and Hamaticolax prolixus. ==Conservation==

P. notatus is not a threatened species. It is widespread and apparently not in decline. ==References==