Return to Conservation Biology Research on Fish

Porterfield, J., and P. Ceas. 2012. Life histories of the northern longear sunfish (Lepomis megalotis peltastes) and pugnose shiner (Notropis anogenus) in Minnesota, with examinations of other rare non-game fishes. Final report submitted to the State Wildlife Grants Program, Minnesota Department of Natural Resources. 63 pp. State Wildlife Grants Program final report. 


The northern longear sunfish (Lepomis megalotis peltastes) was recognized by the Minnesota DNR as a Species in Greatest Conservation Need due to its perceived spotty Minnesota distribution and its threatened status in Wisconsin. Except for the preliminary data on distribution and abundance gathered by Porterfield and Ceas (2008), nearly all other life history data comes from studies that were conducted outside of Minnesota on stream-dwelling populations (Cooke and Phillip, 2009), versus the lake-dwelling populations that we find in Minnesota. The pugnose shiner (Notropis anogenus) is listed as a Species of Special Concern in Minnesota, as a Threatened Species in Wisconsin, and as an Endangered Species in Ontario. Very little is known about this species. This study, funded by the Minnesota State Wildlife Grant program examined the life history of lake-dwelling populations of both species.

Northern longear sunfish (LES) were quite restricted in the lake habitat they used. Characteristics of the lakes where we found LES are : clear water (an average secchi disk reading of 9’ or greater), shorelines that have relatively undisturbed stretches of emergent aquatic plants, extensive shallows (< 3’ depths), and a firm substrate that was usually rich with organic detritus and submerged plants. However, adult LES were not present in the shallow shoreline waters after ice-out until aquatic plant regrowth had begun. LES remained in the shallows during the warmer months of the year (mid-May – August), but once the aquatic vegetation began to die back in late Summer/Fall the fishes disappeared from the shallows. Juvenile sunfishes (generally < 30 mm) were found scattered along the vegetated shorelines, and were generally associated with areas of thick bulrush beds or dense muskgrass. Shoreland development, including the presence of boat docks/piers, did not appear to be a limiting factor compared to the large-scale removal of aquatic vegetation (or alteration of the aquatic vegetation by extensive nutrient input or soil erosion). Otolith analysis revealed that, on average, about six growing seasons are required for northern longear sunfish to reach 100 mm total length (TL). During the summer spawning season the distinctive saucer-shaped nests could be found in clearings within the plant beds, often right next to the shoreline, at depths of 6-36 inches (15-92cm). Larger/older individuals (Age 4+) tended to move into the shallows first and spawn in June. Once these older individuals left the breeding ground then the younger/smaller individuals moved in to spawn. We did not observe colonial nesting or cuckoldry, as has been reported for some riverine populations (Dupuis and Keenleyside, 1988), but nesting densities were quite low when compared to that riverine study. Stomachs of LES contained mostly Amphipods (Scuds – Gammerus spp.), and caddisfly (Trichoptera) larvae in 2010, and Amphipods and midge (Chironomidae) larvae in 2011, and on a given sampling date these prey were often consumed by most LES examined. When looking at trends, females and males had similar diets. As expected, LES would actively take prey from the water column and from the sides of plants and rocks. A different feeding behavior had the LES using its lower jaw to frequently scoop up substrate and we assume that this technique is used to capture scuds. Through stable isotope analysis we noticed a shift in feeding location from the pelagic to littoral zone, which correlates with the appearance of LES in the shallows in mid-May. The trophic feeding position did not change significantly throughout the summer, indicating that as LES moved into the shallows they did not change where they were feeding on the food chain.

Pugnose shiners (PNS) were also were quite restricted in their habitat use, requiring clear water lakes with shorelines that have relatively undisturbed stretches of emergent aquatic plants. Fishes were found in May in deeper (4-6’) water, which corresponded to 15-30m from shore. As the summer progressed, and as the aquatic vegetation grew thicker in the shallower waters, pugnose shiners were then found closer to shore in waters 3-4’ deep. Unlike LES, however, pugnose shiners were rarely found in the very shallow waters (1-2’ deep) immediately adjacent to shore, which can make sampling via backpack electrofishers problematic. PNS were always associated with dense aquatic vegetation, and were not found in open waters. As with the LES, pugnose shiners were found in the shoreline shallows from approximately mid-May to mid-October. The results of the stable isotope data suggest that as April turned into May the fishes were migrating from the deeper portions of the littoral zone into the shallow portions. In the field and in aquaria pugnose shiners are an extremely wary/skittish fish, which made behavioral observations difficult, and spawning was not observed. Females of Age 1 (35mm TL Ave. length) contained abundant Mature/Mature Ripe ova by mid-May in 2010, 2011, and 2012 and were believed capable of spawning. Age 2 males were sexually mature by mid-May. The testes of Age 1 males became mature by early July, and thus Age 1 males were potential spawners during late summer. Snelson (1971) hypothesized that pugnose shiners were herbivorous given the elongated intestine, but Suttkus and Bailey (1990) stated that the serrations on its pharyngeal teeth may be an adaptation to feeding on microcrustaceans. Our observations on a much larger data set demonstrate that pugnose shiners feed on both microcrustaceans and filamentous green algae, and that there are times when the species feeds almost exclusively on specific prey items. Stomachs of PNS contained mostly Ostracods, filamentous algae, water mites (Hydracarina), and Cladocerans, with Ostracods making up the majority of the diet overall, but there were a few sampling periods when the stomachs of pugnose shiners would contain large quantities of filamentous algae or water mites. Juvenile pugnose shiners were not found in the study areas. During spring and summer 2013 when we return to Fish Lake to capture and observe spawning individuals, we will also make a conscious effort to find juveniles and fill in the gaps in the early life history of the species.Following the protocol established in 2004 and used again in ’05 and ‘06, twenty 1-mile stream segments within the Rock and Big Sioux watersheds of southwestern Minnesota (Missouri River system) were selected randomly using an ArcView extension program. Based on known habitat preferences, aerial photos of the twenty stream segments were reviewed to identify the 10 most likely sampling sites within each stream segment. If off-channel habitats were present, then these were included as potential sample sites. A brief field reconnaissance of each stream segment allowed us to ra k the ten sites within each segment according to which sites appeared most suitable for Topeka shiners, and sampling was conducted using a 10’ x 5’ eighth-inch mesh minnow seine.

Full document (3314 KB) This is a PDF file.
You will need Adobe Acrobat Reader to download it.