American Fisheries Society Symposium 77:733–743, 2011 © 2011 by the American Fisheries Society A Review of the Interactions between Catfi shes and Freshwater Mollusks in North America JEREMY S. TIEMANN* Illinois Natural History Survey Institute of Natural Resource Sustainability at the University of Illinois Urbana-Champaign 1816 South Oak Street, Champaign, Illinois 61820, USA STEPHEN E. MCMURRAY Missouri Department of Conservation, Resource Science Division 1110 South College Avenue, Columbia, Missouri 65201, USA M. CHRISTOPHER BARNHART Missouri State University, Department of Biology 901 South National, Springfi eld, Missouri 65897, USA G. THOMAS WATTERS The Ohio State University, Department of Evolution, Ecology, and Organismal Biology 1315 Kinnear Road, Columbus, Ohio 43212, USA Abstract.—Catfi shes are important in freshwater ecosystems not only as consumers, but also as essential partners in symbiotic relationships with other organisms. Freshwater mol- lusks are among the many organisms that have interactions with catfi shes. For example, icta- lurids are hosts for larvae of several native freshwater mussel species. The larvae, which attach briefl y to gills or fi ns of fi sh to complete their development to the free-living juvenile stage, disperse via upstream and downstream movement of host fi sh. In turn, freshwater mussels serve as a food source for some catfi sh species while other catfi sh species may use spent mus- sel shells for habitat. Ictalurids also benefi t from the conservation status of many freshwater mussel species. Federal and state laws protecting these invertebrates can preserve water qual- ity and habitat and, at times, provide incentives and funding for conservation and restoration of stream and riparian habitats. Introduction ter gastropods (Lysne et al. 2008). Because catfi shes and aquatic mollusks cohabitate in many ecosys- North American native freshwater mollusks are tems, understanding interactions of these taxonomic among the most imperiled group of organisms in groups can benefi t managers and conservationists. In the world (Lydeard et al. 2004; Christian and Harris this review, we summarize importance of catfi shes 2008). More than 70% of the 297 freshwater mus- to freshwater mollusks and explain how catfi shes sel taxa are extinct, listed federally as endangered can benefi t from freshwater mollusks. or threatened, or in need of conservation, and more than 60% of the 842 freshwater snail taxa are im- Predator–Prey Relationships between periled, critically imperiled, or presumed extinct (Williams et al. 1993; Lysne et al. 2008). In his na- Catfi shes and Freshwater Mollusks tional strategy for the conservation of freshwater Both freshwater mussels and snails are important mussels, Neves (1997) pointed out that the public components of aquatic ecosystems and fi ll several has a lack of understanding of the plight and value valuable ecological and economic roles. Freshwa- of freshwater mussels; the same is true for freshwa- ter mollusks and their feces and pseudofeces are valuable components in food webs (Vaughn and * Corresponding author: [email protected] Hakenkamp 2001; Brown et al. 2008). Freshwater 733 734 TIEMANN ET AL. mollusks are a food source for some catfi sh species, (1888) reported that mollusks accounted for nearly including black bullhead Ameiurus melas, yellow 25% of the diet in black bullhead, 20% in brown bullhead A. natalis, brown bullhead A. nebulosus, bullhead, 15% in channel catfi sh, and 5% in yellow blue catfi sh Ictalurus furcatus, channel catfi sh I. bullhead. We assume effects of catfi sh predation punctatus, and fl athead catfi sh Pylodictis olivaris would vary seasonally and with mollusk density and (Forbes 1888; Edds et al. 2002; Grist 2002). Sev- fi sh size (e.g., gape size). Bailey and Harrison (1948) eral species of madtoms Noturus spp. also have stated that few freshwater mussels were consumed been known to consume mollusks. Gastropods have by channel catfi sh in the Des Moines River because been reported in stomachs of the slender madtom N. mussels were rare in the river, whereas Forbes exilis (Curd 1960), Ouachita madtom N. lachneri (1888) stated that some channel catfi sh collected in (Robison and Harp 1985), and northern madtom N. September and October had nothing but mollusks stigmosus (Tzilkowski and Stauffer 2004). Forbes in their stomach, and brown bullheads collected in (1888) described mollusks as “a decidedly important September and October fed nearly exclusively on element” in catfi sh diet, with bivalves (e.g., unionids fi ngernail clams. Since the time of Forbes (1888), and sphaeriids) and gastropods being nearly equally North American freshwater mollusks have experi- consumed. While some authors have reported catfi sh enced drastic reductions in terms of species richness consuming whole mollusks, including shell (e.g., and biomass as a result of habitat destruction, envi- Graham 1999; Ledford and Kelly 2006), Forbes ronmental contamination, overharvest, and invasion (1888) suggested that catfi shes were able to sepa- of nonindigenous species (Bogan 1993; Williams et rate mollusk bodies from their shells. He stated that al. 1993; Watters 2000). It is unknown what kind of a catfi sh “seizes the foot of the mollusk while the effects, if any, this had on catfi sh predating on native latter is extended from the shell, and tears the animal mollusks. loose by vigorously jerking and rubbing it about.” Within the past 100 years, North America has Forbes (1888) continued by speculating that a catfi sh witnessed invasion of several freshwater mollusks, might be able to crack shells in its jaws to consume including corbiculids (e.g., Asian clam Corbicula the soft parts. He strengthened his argument by stat- fl uminea) in the 1930s and dreissenids (e.g., zebra ing that “no fragment of a shell was ever found in mussel Dreissena polymorpha) in the 1980s (Wat- <the> stomachs, but the bodies of the animals had ters et al. 2009). Asian clams and zebra mussels are invariably been torn from the shell while yet living usually smaller than native freshwater mussels, are – as shown both the fresh condition of the recently in- often very abundant, and have low mobility (Wat- gested specimens and likewise by the fact that the ad- ters et al. 2009). Blue catfi sh have been known to ductor muscles were scarcely ever present in the frag- utilize these as a food source (Grist 2002; Eggleton ments.” He also stated that 120 bodies and opercles and Schramm 2003; Eggleton and Schramm 2004). of Viviparus spp. (as Melanthos and Vivipara), but no Ictalurid consumption of zebra mussels and Asian shells, were counted in one specimen. In describing clams varies seasonally and can be dependent upon catfi shes, Forbes (1888) stated, “the capacious mouth, fi sh size and location of the fi sh (e.g., main chan- wide esophagus, and short broad stomach, admit ob- nel versus fl oodplain lake) within a particular habitat jects of relatively large size and of nearly every shape; (Eggleton and Schramm 2003; Bowers et al. 2005; the jaws, each armed with a broad pad of fi ne sharp Bowers and de Szalay 2007). Magoulick and Lewis teeth, are well calculated to grasp and hold soft bodies (2002) noted that blue catfi sh selected against more as well as hard; the gill-rakers are of average number energetically rich shad (Dorosoma spp.) during and development; and the pharyngeal jaws— broad, summer months, instead choosing more abundant stout arches below and oval pads above, with thin op- and energetically poor zebra mussels. Effects this posed surfaces covered with minute, pointed denticles dietary shift may have on catfi shes are unknown — serve fairly well to crush the crusts of insects and but has been implicated in declines in total length of the shells of the smaller mollusks and to squeeze and other fi shes. French and Bur (1996) found that total grind the vegetable objects which appear in the food. length of 6-year-old female freshwater drum Aplodi- The use made of the jaws in tearing mollusks from notus grunniens in Lake Erie signifi cantly declined their shells <sic> is probably the most peculiar feed- following invasion of dreissenids, presumably due ing practice of these animals.” to increased feeding on the nonindigenous mus- Data are limited on when and how much cat- sels. While any effects have yet to be documented fi shes consume native freshwater mollusks. Forbes in catfi sh, they would counteract management goals CATFISH–MUSSEL INTERACTIONS 735 of increasing size of blue catfi sh to increase angler water mussels. The article stated that even though satisfaction (e.g., Dames et al. 2003). some ictalurids consume freshwater mussels, legal- Catfi shes may help to control these nonindig- ity of using mollusks as bait varied from state to enous species (e.g., Robinson and Wellborn 1988; state. For example, in Missouri, it is legal to possess Bartsch et al. 2005), but sheer abundance and high up to fi ve freshwater mussels (other than species of fecundity of Asian clams and zebra mussels make it conservation concern) per day with a fi shing license, doubtful that fi shes will ever eradicate them (Thorp and these may be used as bait (MDC 2010); how- et al. 1998; Magoulick and Lewis 2002). Rather, ever, in Ohio, it is illegal to possess any freshwater catfi shes could become vectors in dispersal of these mussels, including invasive species (Watters et al. nonindigenous mollusks because both zebra mus- 2009). Promoting awareness of freshwater mollusk sels and Asian clams can pass through blue catfi sh conservation among anglers could be a valuable tool undigested (D. Shoup, Oklahoma State University, for aquatic managers because improving freshwater personal communication). This potential for spread- mollusk populations and protecting their habitats ing nonindigenous mollusks needs to be considered would benefi t not only mollusks themselves, but when moving fi shes between water bodies or into also could bolster catfi sh populations and improve hatcheries.