Aphredoderus sayanus (Gilliams, 1824)
Basis for Listing
The Pirate Perch (Aphredoderus sayanus) is a southern species that reaches its northernmost distribution in the southeastern portion of the state (Eddy and Underhill 1974; Becker 1983). It has been recorded in Minnesota only from the Mississippi River system below St. Anthony Falls. Prior to 1989, it was known from only 12 sites in southeastern Minnesota. It is now known from 27 sites, all in the lower Mississippi River and the mouths of its tributaries in Dakota, Wabasha, Winona, and Houston counties. Despite the increase in locational records, the Pirate Perch remains rare in Minnesota and was listed as a special concern species in 1996.
The Pirate Perch has a heavy, soft body, with a maximum total length of 12.5 cm (4.9 in.). Its large head, with scales on the sides, has a projecting lower jaw; both jaws have numerous teeth. Anal and urogenital openings are present just posterior to the gills. There are 2-3 spines on the dorsal fin. Coloration is black or olive on the back and sides, and yellow or white below.
Pirate Perch prefer warm, shallow, slow-flowing or still water. They are found over sand and muck bottoms, and under cover of plants, leaf litter, or other debris in sloughs, ditches and backwaters near the Mississippi River (Hatch et al. in preparation). They are also found in root wads and beaver dams.
In Mississippi River Pools 4 and 8, fish surveys collected 50 Pirate Perch from 1993-2015. The species’ preferred habitat was predominately backwaters (49 fish) while one specimen was collected from a side channel border. Secchi disc readings (transparency) ranged from 28-118 cm (11-46 in.), depths from 0.4-1.8 m (1.3-5.9 ft.), and velocities from 0.0-0.47 m/s (0.0-1.5 ft. /s). However, all but one observation on the latter variable was 0.1 m/s (0.3 ft. /s) or less (LTRMP 2016).
Biology / Life History
Little is known about the life history of the Pirate Perch. In Minnesota, it breeds in the spring. Eggs maintained at 19-20°C (66-68°F) are hatched in 5-6 days (Martin and Hubbs 1973). Pirate Perch are quiet in the daytime, resting under rocks or on plants. They are most active at night, at the bottom of waterbodies, though even then they swim slowly and move little. Their diet consists primarily of insects, with lesser amounts of crustaceans, oligochaetes (segmented worms), small fishes, and algae.
Conservation / Management
As an inhabitant of sloughs that are subject to silting, draining, and dredging, the Pirate Perch is an indicator of the health of its aquatic environment. Water quality should be maintained or improved, and efforts to minimize siltation should be encouraged near Pirate Perch habitat.
Conservation Efforts in Minnesota
The Minnesota DNR Division of Ecological Services received a State Wildlife Grant to conduct surveys for rare fish species in the Mississippi River from the Twin Cities to the Iowa border. These surveys were conducted from 2006-2008 (Schmidt and Proulx 2009), and the Pirate Perch was a targeted species. Additional research needs for the Pirate Perch in Minnesota include life history studies, genetic analysis, and identification of habitat guilds.
The recent inception of Minnesota’s Clean Water Legacy Program will eventually yield benefits to Pirate Perch habitats through nutrient and sediment load reductions.