Pirate Perch

Aphredoderus sayanus

Pirate_perch_Aphredoderus_sayanus_female_3-22-13.jpg

Pirate perch female, side view photo with black background
Pirate perch, Aphredoderus sayanus, female
Lance Merry
Family

Aphredoderidae (pirate perches) in the order Percopsiformes (trout-perch and allies)

Description

The pirate perch is a small, grayish fish that is heavily speckled with black. There is a narrow vertical dark bar at the base of the tail fin. another bar is often visible beneath the eye. The fins are dusky. Breeding adults are tinged with purple or violet; breeding males are nearly black. There is only one dorsal fin and no adipose fin. The body is rough to the touch (the scales are rough-edged ctenoid scales); the tail fin is slightly notched, but without a fork. The anus is located far forward on the body, in the throat area; in Missouri, the only other fish with that characteristic are the cavefishes. The pirate perch is most closely related to cavefishes and trout-perch.

Size

Total length: 3 to 5 inches.

Habitat and conservation

Bottomland lakes, overflow ponds, and quiet pools and backwaters of slow-moving streams and ditches. In the Mississippi River, it seems to prefer protected inlets and overflow waters. Inhabits areas with clear, warm water, abundant cover, and no current.

This solitary, secretive fish hides during daylight hours about thick growths of aquatic plants or accumulations of organic debris. Pirate perch venture out to feed at night. Most active at dawn and dusk, living on or near the bottom.

Foods

Carnivorous, feeding on aquatic insects, small crustaceans, and small fish. It fees by sucking in food items when its mouth is opened quickly.

image of Pirate Perch distribution map
Distribution in Missouri

Occurs in Missouri's southeastern lowlands and adjacent parts of the Ozarks. Also in a few locations along the Mississippi River.

Life cycle

Spawning apparently occurs in May. Breeding biology is not well-known. The nests of this species might be guarded by both male and female, but since it appears the eggs are incubated in the female pirate perch's gill cavities, that might not be the case.

The idea of the females carrying fertilized eggs in their gill cavities is supported by the positioning of the anus ― technically, it's a cloaca (clo-AY-cuh), a single opening that combines the openings for excretory and genital functions. That the anus/cloaca is located far forward on the fish's body seems to be an adaptation to allow for the easy transfer of eggs from the cloaca to the mouth. This is the case for some species of cavefishes, which also have the cloaca positioned far forward. Additionally, a wild-caught female pirate perch was found to be carrying eggs in her gill chamber. Interestingly, in the smallest young pirate perch, the cloaca is located just in front of the anal fin, but as the fish grows and reaches sexual maturity, the cloaca gradually moves forward on the body.

Lifespan is about 4 years.

Human connections

It's called a "pirate perch" because early observations of the fish noted it eating other fishes. It's clear that it mainly eats aquatic insect larvae, but the name stuck.

The species name, sayanus, was bestowed on this fish to honor the famous American naturalist Thomas Say (1787–1834). He helped found the Academy of Natural Sciences in Philadelphia, published monumental reference works on U.S. insects and shells, formally described more than 1,000 species of beetles alone, and went on several expeditions, including the famous Stephen Long exploration of the Rocky Mountains. Many other animals were named after him, including a genus of flycatchers (the phoebes), Sayornis.

Ecosystem connections

The pirate perch is the only species in its family, the Aphredoderidae. Several related species are known as fossils. It, along with the cavefishes and several other groups, seems to be a holdover from an ancient fauna that occupied the Mississippi Valley before the ancestors of most modern-day fishes had migrated into the region. Like the trout-perch, it seems to be the surviving remnant of a larger group that is now mostly extinct.

A study published in 2013 indicated that the pirate perch employs an unusual form of camouflage to conceal its presence from the prey it hunts. For species such as aquatic beetles and tree frogs that are preparing to lay eggs, it is important to find aquatic habitats without fish, because fish would eat their larvae. They use their sense of smell to detect the presence of fish in the water, and they avoid laying eggs in water that smells like fish. Apparently, however, they cannot detect the presence of pirate perch, so the pirate perch are somehow not emitting an odor, cloaking their odor, or mimicking another odor. It's like an arms race between predators and prey.