Fish in Focus:   Pirate perch, Aphredoderus sayanus



Pirate perch, Aphredoderus sayanus
from the Ocklokonee drainage in South Georgia
Photo by Will Pruitt

The Pirate Perch
From The Fishes of Iowa

The pirate perch family Aphredoderidae is represented by a single species in the eastern part of this continent. It is a distant relative and shares some physical characteristics with trout-perch and cavefishes. Charles C. Abbott, a pioneer ichthyologist, is credited with giving this fish its common name, pirate perch, after observing that a specimen he kept in an aquarium ate only other fish.

Pirate perch in Iowa occur in widely scattered locations along the Mississippi River and several major tributary streams. Most frequently it is found in the quiet pools and backwaters that are characterized by clear, warm water, absence of current and abundant aquatic plant life or organic debris for cover. Recent fish collections have failed to document this fish at many earlier survey sites, which indicates both their range and abundance have decreased.

Pirate perch is a stout, dark-colored fish, with a single dorsal fin and ctenoid scales on the head and body. The tail fin is slightly notched. The anus is far forward of the anal fin and located on the throat of adults. The mouth is large and oblique with the lower jaw projecting forward. Numerous very small villiform teeth in bands occur on the upper and lower jaws. The gill cover has a sharp spine and the rear edge of the preopercle is strongly serrated. The dorsal fin has 2 to 3 short spines with l0 to ll rays, anal fin 2 to 3 spines with 6 to 7 rays, and the pelvic fin has a single spine with 6 rays. The lateral line is incomplete or absent with 48 to 59 lateral series scales. The upper body is dark olive to black in color with the sides lighter and belly yellowish. The back and sides are thickly speckled with black, and there are two narrow, vertical bars at the base of the caudal fin. Adults are commonly 3 to 4 l/2 inches long with a maximum length of about 5 inches.

This species maintains a solitary existence, seeking protection during daylight in aquatic plants or organic debris. Then in darkness it feeds on immature aquatic insects, small crustaceans and occasionally on small fish. Little is known about spawning requirements. It is likely, however, that eggs are incubated in the gill cavities in a manner similar to cavefishes, which also have the anus located on the throat. Small pirate perch have the anus located just frontal of the anal fin, but the opening gradually migrates forward to the throat as the fish grows in size and matures.


Pirate perch: nest spawner or branchial brooder?
(From the Spring 2000 American Currents)

Because of its secretive nature, the reproductive behavior of pirate perch Aphredoderus sayanus is poorly known. Early works report that pirate perch build and guard nests. Others speculate that the female incubates her eggs in her mouth, basing such speculation on three pieces of evidence: 1) the pirate perch¹s close relationship and anatomical similarity to the mouthbrooding cavefish (Amblyopsis spelaea); 2) the observation that eggs artificially stripped from a female pirate perch moved along a groove towards the branchial cavity; and 3) the fact that a gravid female pirate perch had been found with three eggs in its branchial cavity (the eggs were not identified as to species). Separate accounts of aquarium spawnings by Ray Katula and John Brill, published in American Currents, did not mention any evidence of branchial egg retention. Although neither author actually witnessed the spawning act, both reported that a nest, or depression, had been fanned in the gravel.

Now a scientific paper published in the December 1999 Journal of Freshwater Ecology reports that pirate perch do not appear to be branchial brooders; instead, the species releases adhesive eggs over leaf litter and woody debris. Five adult pirate perch were collected from the wild and maintained in a well-aerated 30 liter (8 gallon) aquarium with leaf litter and woody debris to simulate natural habitat. The tank was kept in a room with restricted traffic and an unshaded window to simulate the natural photoperiod. Water temperature was 17-19°C (63-66°F). The fish were fed live amphipods.

The five pirate perch remained inactive in the tank until the first week of March, when numerous eggs were observed. The eggs floated and drifted until they become attached to any surface with which they came in contact. Eggs were not observed being transferred to the branchial cavities. Nor were eggs observed being fertilized by the males, which begs the question: Would pirate perch, assuming for the sake of argument that they are mouthbrooders, attempt to brood eggs that are unfertilized?

The aquarium experiment confirmed that pirate perch spawn fairly early in the year, from February to March, presumably to avoid interspecific interactions with other larval fishes. Aquarists willing to tackle spawning this odd fish may be wise to begin their efforts before winter turns to spring.


Secret Sex Life of the Pirate Perch Revealed!
(Originally published in American Currents in 2003 by Gerald Pottern)

Until 2003 the reproductive behavior of the pirate perch (Aphredoderus sayanus) remained a mystery and the subject of much speculation. The urogenital pore in pirate perch, swamp fish, and cave fishes (order Aphredoderiformes) is located just behind the gills, and in the cavefish Amblyopsis the eggs are drawn from the urogenital pore forward into the gill cavity, where they are brooded until hatching. Many ichthyologists have presumed that pirate perch probably do something similar, brooding eggs either in the gill chamber or mouth, except that: 1) there was no published report describing a pirate perch spawning event; 2) no live pirate perch had been found with eggs in the mouth or gill cavity; 3) spawnings in aquaria resulted in eggs either scattered about the bottom or in a clump of plants or debris; and 4) the volume of eggs produced exceeds the volume of the mouth and gill cavities.

Finally, William J. Poly of the California Academy of Sciences and James E. Wetzel of Southern Illinois University observed aquarium spawnings by several pairs collected from the Cache River basin in southern Illinois, and have captured the event on film. In the April 2003 issue of Ichthyological Exploration of Freshwaters (Vol 14: 2, p 151-158) the authors report that pirate perch eggs and sperm are drawn by opercular pumping from the urogenital pore into the gill cavity, probably along two thoracic gooves on either side of a central knob immediately anterior to the urogenital pore. The pumping effect is created by rhythmic gill flaring, apparently similar to the behavior used when coughing out food or debris. The margin of each branchiostegal membrane (the gill flap) is curled inward, which may assist this process and prevent loss of eggs or sperm. The gametes are drawn past the gills, into the mouth, and then blown out of the mouth into the spawning substrate, often among fine root mats of trees. The breeding pair is oriented side-by-side, and repeatedly push their snouts into the spawning substrate prior to and during spawning. The male’s cloud of sperm is released while the female is ejecting eggs from her mouth. The eggs are non-adhesive and demersal, and no nest-building or parental care was observed. The authors have termed this unique method “transbranchioral spawning,”describe the morphological features and behaviors associated with it, and discuss its possible evolutionary significance among the cavefishes.

 

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