Demography and food habits of the shovelnose sturgeon in the Middle Wabash River, Indiana
Abstract
Sturgeon populations worldwide have been declining at an alarming rate. The shovelnose sturgeon, Scaphyrhychus platorynchus, is the smallest and currently most abundant sturgeon species native to North America. While the populations of shovelnose sturgeon in the Mississippi and Missouri Rivers have been highly studied, system specific differences within the Wabash River, as well as between the Wabash and other river systems, may be important to their continued protection. In order to assess system specific differences within the Wabash River shovelnose sturgeon population and between other river systems, information regarding the sex- and season-specific differences in demographic characteristics, as well as dietary requirements, were analyzed. Shovelnose sturgeon were sampled over an 8.22km stretch of the Middle Wabash River, a known spawning habitat. Sturgeon were captured using boat electroshocking (Spring, Summer and Fall 2008) and hoop nets (Spring 2009). Of the 570 shovelnose sturgeon sampled, 168 fish were retained and sacrificed for sex-specific demographic characteristics as well as food habits analysis. Of the 168 sacrificed sturgeon, female sturgeon comprised 11.56% of the total sample, and males 88.44%. Sex ratio was skewed towards males in all sampling seasons with 4:1 males to females in spring 2008, 13:1 males to females in fall 2008, and 12:1 males to females in the spring 2009 sample. Mean CPUE for boat electroshocking across all sampling dates was 35.7 fish/h. April through June catchper- unit-effort (CPUE) ranged from 3–102 fish/hr, while July through November ranged from 12–39 fish/hr. Results from this study support previous findings that shovelnose sturgeon are opportunistic feeders throughout the year. Diets changed throughout the year, and spring fish had a preponderance of Chironomidae larvae in their stomachs, while fall fish had mainly Hydropsychidae larvae. Unlike other reports on shovelnose sturgeon diets, we also observed the remains of small bony fish in a small percentage of stomachs from fish collected during both spring sampling events. Sturgeon captured in the spring also had greater amounts of inorganic materials in their stomachs compared to fish from fall samples. The results presented in this study suggest that there are indeed system specific differences in the demography and food habits of Wabash River shovelnose sturgeon compared to those in the Mississippi and Missouri Rivers. Management plans created for shovelnose sturgeon in other river systems may not be appropriate for the Wabash River population. Management of this species requires system specific regulations in order to sustain a commercial fishery. Additional research on the shovelnose sturgeon should be completed in order to detect whether other system specific ecological characteristics of this species.
Degree
M.S.
Advisors
Goforth, Purdue University.
Subject Area
Aquatic sciences
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