Ontogenetic patterns in prey use by pallid sturgeon in the Missouri River, South Dakota and Nebraska

Abstract

The pallid sturgeon (Scaphirhynchus albus) is an endangered species native to the Missouri and Mississippi rivers. To date, recovery efforts have focused on stocking juvenile fish, but little is known about ontogenetic changes in diet composition. Although diet composition for pallid sturgeon is believed to change from macroinvertebrates to fish, it is unclear at what size and ⁄ or age these ontogenetic diet shifts occur. To evaluate diet composition, 29 hatchery-stocked pallid sturgeon (range 356-720 mm fork length [FL]; mean = 549; SE = 23) were collected from the Missouri River downstream of Fort Randall Dam, South Dakota and Nebraska during summer 2006. The majority of pallid sturgeon (72%) were captured within a large delta region formed by the Niobrara River in the headwaters of Lewis and Clark Lake. Predominant prey of pallid sturgeon based on percent occurrence was Ceratopogonidae (81%), Isonychiidae (67%), Chironomidae (52%), and fishes (24%). Percent composition by wet weight showed that diets were composed of fishes (68%), Ephemeroptera (23%), Decapoda (6%), and Diptera (3%). Graphical analysis of combined data showed that mayflies, particularly Isonychiidae, were an important component of pallid sturgeon diets. Nonetheless, the percent composition of fishes in the diet increased with pallid sturgeon body size; for fish > 600 mm FL (5-7 years of age) diets were composed primarily of fish prey (66%, mostly johnny darters Etheostoma nigrum). These findings highlight the importance of ontogenetic changes in diet composition for pallid sturgeon. Moreover, the unique habitat formed in the delta region is characterized by higher fish and invertebrate densities that may enhance foraging opportunities and thus improve recovery efforts for stocked pallid sturgeon.

A stochastic bioenergetics model-based approach to translating large river flow and temperature into fish population responses: the pallid sturgeon example

“…Diet composition plays an important role in determining growth of pallid sturgeon (Grohs et al 2009). Grohs et al (2009) found that mayflies (Ephemeroptera), particularly the family Isonychiidae, are an important component of the juvenile pallid sturgeon diet.…”

“…Grohs et al (2009) found that mayflies (Ephemeroptera), particularly the family Isonychiidae, are an important component of the juvenile pallid sturgeon diet. In addition, the diet of pallid sturgeon changes from macroinvertebrates to fish as their body length increases, with fish between 350 and 500 mm FL consuming 57% fish by wet weight and those more than 500 mm FL consuming 90% fish by wet weight (Gerrity et al 2006;Grohs et al 2009).…”

“…Grohs et al (2009) found that mayflies (Ephemeroptera), particularly the family Isonychiidae, are an important component of the juvenile pallid sturgeon diet. In addition, the diet of pallid sturgeon changes from macroinvertebrates to fish as their body length increases, with fish between 350 and 500 mm FL consuming 57% fish by wet weight and those more than 500 mm FL consuming 90% fish by wet weight (Gerrity et al 2006;Grohs et al 2009). We used these size ranges and their associated percentages of fish and macroinvertebrates to determine the relationship between FL and P. Based on previous work (Sitaramaiah 1967;Hansen et al 1993;Venturelli & William 2006;Grohs et al 2009), the caloric densities used for prey fish and macroinvertebrates were 4473.5 J g 21 wet mass and 3065.8 J g 21 wet mass, respectively, with caloric density assumed to be constant over time.…”

“…The stochastic bioenergetics model we develop here includes not only point estimates of individual model parameters but also their associated distributions, and thus reflects current uncertainty about their true values. This paper focuses on development of an individual-based bioenergetics model for pallid sturgeon that extends Chipps et al's (2010) pallid sturgeon bioenergetics model with swimming costs (Geist et al 2005), diet shift (Grohs et al 2009;Chipps et al 2010), and parameter uncertainty as key components within a framework for informing management decisions. The goal is a model that comes closer to providing more realistic predictions of pallid sturgeon growth potential within the Lower Missouri River mainstem (the Missouri River mainstem below Gavins Point Dam to its confluence with the Mississippi River).…”

Macroinvertebrate community structure and its seasonal variation in the Upper Mississippi River, USA: a case study

“…Hay (2006) reported that total drift density in the Missouri River was positively correlated with degree-days. Also in the Missouri River, Grohs (2008) noted higher total richness in the summer and fall, but discriminatory power was limited by family-level identifications. And, although temporal patterns were not a focal point of their study, found that community index scores occasionally changed between great river samples taken at the same location several weeks apart.…”