Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon

St. Louis, Missouri, 11-13 January 2005

33.  THE REAL POOP ON PALLID STURGEON ECOLOGY: FECAL ANALYSIS AS A TECHNIQUE FOR RECONSTRUCTING DIET AND INFERRING HABITAT AND BEHAVIOR.

Steven G. George*, U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, EE-A, Vicksburg, MS 39180-6199; Phone 601-634-2897; Fax 601-634-3560; Steven.G.George@erdc.usace.army.mil

Jan Jeffrey Hoover, U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, EE-A, Vicksburg, MS 39180-6199; Phone 601-634-3996; Fax 601-634-3560; Jan.J.Hoover@erdc.usace.army.mil

Catherine E. Murphy, U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, EE-A, Vicksburg, MS 39180-6199; Phone 601-634-4233; Fax 601-634-3560; Catherine.E.Murphy@erdc.usace.army.mil

K. Jack Killgore, U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, EE-A, Vicksburg, MS 39180-6199; Phone 601-634-3397; Fax 601-634-2398; Jack.Killgore@erdc.usace.army.mil

Gut contents of a fish provide tangible evidence of where and in what manner that fish was feeding.  Non-destructive extraction of usable gut contents from rare and endangered fishes, however, can be problematic. Colonic flushing is a safe, effective, and practical method for obtaining fecal samples from pallid sturgeon.  There is no risk of suffusing water into the gas bladder and the technique is harmonious with natural body functions of the fish.  Samples are obtained from the majority of specimens tested.  Sample volume is variable allowing description of spatial and temporal variability in feeding intensity.  Prey are readily identified and enumerated from certain indigestible, diagnostic structures.  Burrowing mayflies, net-spinning caddiflies, and larval midges are readily detected as mandibular tusks, sclerites, and head capsules, respectively.  Other invertebrate taxa can be identified from leg parts (crustaceans), elytra (beetles), and occasionally as intact organisms.  Fishes are readily detected as eye lenses, and are frequently identifiable to lower taxonomic levels based on certain skeletal features (pharyngeal teeth, jaws, otoliths).  Dietary data for pallid sturgeon allow inferences of habitat, behavior, and ontogenetic shifts in principal prey items.  Based on relative frequencies of those prey inhabiting finer, softer sediments versus those inhabiting coarser, harder sediments, characteristics of feeding grounds are described.  Based on relative frequencies of littoral versus pelagic prey, or surface versus benthic prey, lateral and vertical position of the fish in the water column during feeding are inferred.