FISH OF MISSISSIPPI Warmouth (Lepomis gulosus) BRYANT HALEY Department of Wildlife and Fisheries, Mississippi State University, Mississippi State, MS 39762 USA Abstract—Lepomis gulosus (Curvier 1829) is a sunfish commonly called the warmouth. It is a freshwater fish found throughout the eastern and southeastern portion of the United States. The warmouth are able to tolerate a variety of habitat conditions allowing them to survive in waters with low levels of oxygen and to thrive in areas of elevated salinity and temperature. They are omnivores and eat a variety of foods. No conservation concerns exist for the warmouth in the south or southeastern United States; they are vulnerable or imperiled in a few northern states. The warmouth are good laboratory fish, small-sport fish, and the cane-pole fisherman catches it for food. CONTEXT AND CONTENT Lepomis gulosus is from the Centrarchidae family, the second largest freshwater fish family of the Perciformes order (Table 1). Lepomis is the largest Centrarchid genus with 12 species: L. auritus, L. cyanellus, L. gibbosus, L. gulosus, L. humillis, L. macrochirus, L. marginatus, L. megalotis, L. microlophus, L. miniatus, L. punctatus, and L. symmetricus. Classification Scientific Name Meaning Kingdom Animalia Phylum Chordata Class Actinopterygii ray-finned fishes Order Perciformes perch-like Family Centrarchidae sunfishes Genus Lepomis scaled-gill cover Species gulosus large mouth Table 1. Warmouth classification, scientific name and meaning (Robins et al. 1991; Berra 2008) GENERAL CHARACTERISTICS The first and most obvious distinguishing feature of the warmouth is the redness of their eyes, particularly in breeding males (Becker 1983). This, along with a propensity to frequent stump fields, has earned them the nickname “red-eye stumpknocker” (Laerm and Freeman 1986). The warmouth is likely given its name because its stripes resemble the warpaint of American Indians (Moyle 1976). The fish’s aggressively hard strike, often breaking the surface of the water is thought to be another reason for its name. Its large mouth extends to just beneath its large red eyes lending itself to many of its other nicknames. Some of the warmouth’s common names are bigmouth, Indian fish, sun trout, wood bass, goggle eye, red-eye bream, mud chub, perch mouth, strawberry perch, weed bass, wide-mouth sunfish, yawnmouth perch, mudgapper, jugmouth, molly, and morgan (Ross 2001). Warmouth have deep bodies which are compressed laterally, similar to bluegill. The adult warmouth have olive and mottled brown coloring, some have a purple tint and can change coloring to blend in with surroundings. Their ventral side is gold in color. They range in length from 10.2 to 25 cm long and can reach a typical weight of 1 kg, with the largest warmouth on record caught in Florida weighing in at 1.1 kg (FFWCC 2013). Their mouth is terminal and large. The upper jaw extends to the middle of the eye or farther with their lower jaw protruding noticeably beyond their upper jaw, similar to bass (Mettee et al. 1996). They have a well- developed pad of lingual teeth and patches of teeth on the palatine bones (Ross 2001). Warmouth also have teeth on their pterygoid (Hubbs et al. 1991; Hay 1894). They have sharp cone-shaped teeth on both upper and lower jaws as well as similar, but more rounded, teeth on their lower pharyngeal arches. On the side of their cheek, radiating from the eye and extending to the back of the gill cover are three to four posterior reddish-brown streaks (Etnier 1993). One to two anterior dark streaks radiates forward from their eye toward their mouth (Mettee et al. 1996). Their supramaxilla bone’s length is greater than the width of maxilla. The opercular bone is inflexible “to back margin and will usually fracture if bent forward” (Ross 2001). DISTRIBUTION Warmouth are naturally found in lentic or nearly lentic systems throughout much of the eastern United States from the Great Lakes basins south to Florida and west across the Gulf States to New Mexico (McMahon et al. 1984). They have also been introduced as far west as California; however, they are not native to the area. They prefer clear-watered lakes and large slow-moving streams with muddy bottoms and abundant aquatic vegetation for cover (ODNR 2013). They can also be found in the Everglades of Florida as well as other marshes in the southeastern US. (McMahon et al. 1984). FORM AND FUNCTION The warmouth is commonly confused with the green sunfish and the rock bass as they possess striking similarities in both mouth and body size. Warmouth are, however, generally larger than either of these (TPWD 2004). They are deep bodied and laterally compressed though not as much as a bluegill, being more compressed dorsoventrally and slightly less laterally. The warmouth also has three to four brown bars on its cheek and teeth on its tongue where the green sunfish and rock bass both lack this tooth patch (Ross 2001). The rock bass is also identified as having five to seven anal spines as opposed to the three to four spines on the warmouth (UWSGI 2013). Warmouth have two dorsal fins, the first with 10 spines and the second with 9-10 soft rays; however, they are joined together and appear as one. The anal fin has 3-4 spines and 8-10 soft rays. The pelvic fin is thoracic, below the pectoral fin (Becker 1983). Fins have a darkly mottled appearance. Pelvic fins contain melanophores. There is no adipose fin. They have 36-40 lateral ctenoid scales (UWSGI 2013). The lateral line is complete and follows the anterior arch (Ross 2001). Warmouth are easily sexed as the male warmouths are slightly larger than females and are marked with an orange spot at the posterior termination of the dorsal fin (Larimore 1957). They also have gold and/or light blue specks on their side. Breeding males will have more intense coloring with an increase in the golden yellow colors along with bright red eyes. ONTOGENY AND REPRODUCTION They typically spawn in early spring; however, the breeding season of the warmouth begins in March and can run until September. They may spawn two or more times a season (Laerm and Freeman 1986). Unlike the other sunfish species, warmouth are solitary nesters. They do not spawn in colonies (ODNR 2013). The male warmouth will use his caudal fin to fan the area he wants the nest to create a bowl-shape nest. Their nest is built on gravel or rock in the shallows near the water’s edge (Larimore 1957: Laerm and Freeman 1986). These nest sites are situated, almost without exception, in very dense cover (Laerm and Freeman 1986). Warmouth perform an intense courting ritual. The body of the male fish turns yellow and the redness of his eyes deepens in hue. The male and female fish swim together in the center of the nest. The female releases up to 63,200 eggs striking the male’s face with her body in the process. It is believed that this action by the female signals the male to release his milt (Ross 2001). When spawning is completed, the nest is guarded by the male until the hatchlings are ready to leave the nest (Laerm and Freeman 1986). This usually occurs in a little over a week. After hatching, the warmouth fry grow at a rate of 38 mm per year, assuming the presence of adequate resources. They will become sexually mature in the second year of their seven-year lifespan (Laerm and Freeman 1986). ECOLOGY Migration.--Warmouth are typically a non-migratory species, traveling no more than 100 or so miles for spawning or wintering. According to O’Connell and Vrancken (2010), during the year following Hurricane Katrina, warmouth traveled approximately seven kilometers or 4.34 miles downstream from Bayou Lacombe where their habitat had been destroyed and increased debris had caused a decrease in dissolved oxygen levels. The warmouth requires an oxygen level of 3.6 ppm at 20 C but can survive for a short time in water with oxygen levels down to 1.0 ppm (Larimore 1957). Even though dissolved oxygen levels had remained fairly stable downstream, salinity levels and water temperatures were elevated and yet warmouth had migrated downstream and had created new habitat and had increased abundantly during the year following Katrina (O’Connell and Vrancken 2010). No warmouth were found upstream in the 2006 sampling. Diet.--The warmouth is an invertivore/carnivore and more than other sunfish, tends towards piscivory. It also feeds on aquatic insects and crustaceans (Cook 1959). At the larval stage the primary source of food consists of small crustaceans such as copepods, ostracods and cladocerans (Pflieger 1975). In a compilation of studies on warmouth 3.3-8.7 inches long, the warmouth’s summertime diet consisted mainly of crayfish (Larimore 1957). The one autumn study performed on warmouth 3 inches, diet consisted mainly of fish and mayflies (Larimore 1957). In warm water warmouth may consume 4% of its body weight in food per day (Hunt 1960). Warmouth rarely feed at any time other than the early morning (Larimore 1957). This can render them more difficult to catch than other centrachids, though they will bite artificial lures readily as well as angleworms, minnows, white grubs or crickets (Cook 1959). BEHAVIOR Social and hierarchal behavior.—Warmouth in a natural environment are not prone to congregating in schools and therefore have little social hierarchy (Wallus 2008). Many fish form groups in the winter but warmouth do not (Larimore 1957). Even though aggregation may occur around the warmouths’ desire for similar cover or habitat and for a short period of time after hatching, they are typically an independent unsociable species (Wallus 2008).