Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon

St. Louis, Missouri, 11-13 January 2005

29.  A LABORATORY EXAMINATION OF SUBSTRATE, DEPTH, AND LIGHT USE BY JUVENILE PALLID (SCAPHIRHYNCHUS ALBUS) AND SHOVELNOSE (SCAPHIRHYNCHUS PLATORYNCHUS) STURGEON.

Teresa C. Allen*, U.S. Army Corps of Engineers, St. Louis District, CEMVS-PM-E, 1222 Spruce Street, St. Louis, Missouri 63103; Phone 314-331-8084; Fax 314-331-8806; Teri.C.Allen@mvs02.usace.army.mil

Robert D. Davinroy, U.S. Army Corps of Engineers, St. Louis District, Applied River Engineering Center, Foot of Arsenal Street, St. Louis, Missouri 63118; Phone 314-263-4714; Fax 314-263- 4166; Robert.D.Davinroy@mvs02.usace.army.mil

Dawn M. Lamm, U.S. Army Corps of Engineers, St. Louis District, Applied River Engineering Center, Foot of Arsenal Street, St. Louis, Missouri 63118; Phone 314-263-8090, Fax 314-263- 4166; Dawn.Lamm@mvs02.usace.army.mil

We investigated the influence of substrate type, depth, and light, on microhabitat selection in juvenile pallid (Scaphirhynchus albus) and shovelnose (Scaphirhynchus platorynchus) sturgeon.  Individuals and groups of sturgeon were placed in an 18,927 l (5000 gal) elliptical flume, and their distributions were recorded every 10 minutes over a two hour period.  Data were analyzed as contingency tables using an exact Kruskal-Wallace of two ordered multinomials to test for differences in distributions.  The difference between the two populations at each level of the multinomial table was analyzed as the differences between binomial proportions using asymptotic tests, except when the numerator was small (<10).  All individuals and groups used sand significantly more and gravel significantly less than expected (P < 0.0001 all cases).  Use of sand/gravel mixture and woody structure was not significantly different than expected.  Depth was categorized into shallow, medium, and deep areas based on equal interval distributions.  Individuals and groups did not use depth in proportion to its availability (P < 0.0001 all cases).  All used deep areas significantly more, and medium and shallow areas less than expected based on availability (P < 0.0001 all cases), with the exception of individual shovelnose, in which case the use of medium depth areas was not significantly different than expected (P = 0.1642).  Light was categorized into very light, light, dark, and very dark areas.  Individuals and groups failed to use light in proportion to its availability (P < 0.0001 all cases).  All used very dark areas significantly more than expected based on availability (P < 0.0001 all cases).  Use of dark areas by individual shovelnose (P = 0.0013), groups of pallids (P = 0.0446), and groups of shovelnose (P <0.0001) was significantly more than expected based on availability.  Proportional availability and use of dark areas did not differ significantly in individual pallids (P = 0.0839) and mixed species groups (P = 0.7707).  All used light areas significantly less than expected (P < 0.0001 all cases).  Additionally, individual shovelnose (P < 0.0001), groups of pallids (P < 0.0001), and mixed species groups (P <0.0001) all used very light areas significantly less than expected (P < 0.0001 all cases).  Use of very light areas by individual pallids (P = 0.5026), and groups of shovelnose (P = 0.3547) did not differ significantly from availability.  This study is the first investigation of juvenile pallid and shovelnose sturgeon habitat selection in a large-scale artificial stream system.  Field studies of microhabitat selection by juvenile pallid and shovelnose sturgeon should be carried out to substantiate the results of this study, and to identify critical habitat for recovery and management of sturgeon species.  Proper management of the species likely requires river improvements that provide sturgeon with access to a broad range of habitat conditions over time, including system-wide habitat diversity; natural variation in flow, velocity, temperature, and turbidity; high water quality; a broad prey base; and free-flowing sections which provide suitable spawning and rearing sites.