Effect of Altering Dietary Protein: Energy Ratios on Juvenile Pallid Sturgeon Growth Performance

Pallid Sturgeon Scaphirhynchus albus are endemic to the large, freshwater, river systems of North America and have long been prized for caviar production. Declining wild populations and fishing prohibitions have created interest in the culture of these fish. Protein and energy are often the first nutrients examined when attempting to identify diets appropriate for a novel culture species. Therefore, the present study evaluated the effects of different dietary protein: energy ratios on Pallid Sturgeon growth and body composition. Twelve semipurified diets composed of four crude protein (CP) levels (32, 39, 46, and 53%) and three gross energy (GE) levels (3,600, 4,200, and 4,800 kcal/kg) were fed to 180 juvenile Pallid Sturgeon for 18 weeks. Diets were offered to triplicate groups of five fish each in separate tanks. Fish were fed 2% body weight daily and sampled every 3 weeks. Mean weight gain and body composition were significantly affected by GE content of the dietary treatment (P ≤ 0.05), but not by dietary CP or protein and energy interactions (P > 0.05). The most energetically dense diets yielded significantly larger fish than the least energetically dense diets and the intermediate diets were not significantly different from either extreme. These results suggest that Pallid Sturgeon are able to perform similarly across a wide range of protein: energy ratios (79–147 mg protein/kcal), as long as adequate dietary energy (≥3,800 kcal GE/kg) is provided and essential amino acids are not limiting. This research is the first to evaluate dietary protein: energy ratios for Scaphirhynchus sturgeon culture. Research developing the artificial propagation, husbandry, and nutrition of sturgeon species has developed greatly since the 1950s (Conte et al. 1988; Celikkale et al. 2005). This increase in research activity can be correlated with the sharp worldwide decline of Acipenseriformes throughout the 1980s, caused in part by habitat alteration and overharvest of wild stocks (Keenlyne 1997; Catarci 2004; Moghim et al. 2006; Seibert et al. 2011). Throughout the northern hemisphere, sturgeon species are prized for their meat and unfertilized roe, which is processed and marketed as the delicacy, caviar (Catarci 2004). Currently, many sturgeon species are cultured in captivity for both stock enhancement and commercial purposes (Conte et al. 1988; Fajfer et al. 1999; Ballestrazzi and Garavello 2003; Wei et al. 2004; Celikkale et al. 2005; Mohseni et al. 2006). Literature describing the biology and nutritional requirements of Acipenseriformes is incomplete. Singer and Ballantyne *Corresponding author: [email protected] Received June 20, 2013; accepted August 14, 2013 (2004) stated that the study of metabolic and hormonal regulatory systems in Acipenseriformes provides valuable information regarding vertebrate evolution, and developing a better understanding of this information is increasingly imperative given the decline of wild populations. Fortunately, a sizeable body of research has accumulated regarding the anatomy, physiology, and nutrition of sturgeon species (Dabrowski et al. 1987; Doroshov et al. 1997; Hung and Deng 2002; Singer and Ballantyne 2004; Garcia-Gallego et al. 2009). For example, essential amino acid requirements were investigated by evaluating whole-body, specific tissue, and egg composition of White Sturgeon Acipenser transmontanus (Ng and Hung 1994, 1995) and also via wholebody analysis of Siberian Sturgeon A. baerii Brandt (Kaushik et al. 1991). Additional research has focused on feedstuff digestibility (Kaushik et al. 1989; Stuart and Hung 1989; Medale et al. 1991; Herold et al. 1995; Liu et al. 2009), dietary crude 28 D ow nl oa de d by [ So ut he rn I lli no is U ni ve rs ity ], [ B ri an C . S m al l] a t 0 9: 30 0 8 Ja nu ar y 20 14 PROTEIN: ENERGY RATIOS AND PALLID STURGEON GROWTH 29 protein (CP) requirements (Moore et al. 1988; Mohseni et al. 2007), digestive enzyme activities (Buddington and Doroshov 1986a, 1986b; Lin et al. 1997; Furne et al. 2005; Babaei et al. 2011), thermal regimes (Hung et al. 1989a; Mayfield and Cech 2004; Kappenman et al. 2009), and feeding rate and frequency (Hung et al. 1993; Cui et al. 1997; Deng et al. 2003; Mohseni et al. 2006), as well as the effects of culture densities (Fajfer et al. 1999; Celikkale et al. 2005). It is important to note, however, that these previous examples used many different sturgeon species, including White Sturgeon (Buddington and Doroshov 1986a, 1986b; Hung et al. 1989a, 1989b, 1993; Cui et al. 1997; Lin et al. 1997; Ballestrazzi and Garavello 2003; Deng et al. 2003), Siberian Sturgeon (Medale et al. 1991; Liu et al. 2009), Atlantic Sturgeon A. oxyrinchus (Mohler et al. 1996; King et al. 2004), Adriatic Sturgeon A. naccarii (Furne et al. 2005), Chinese Sturgeon A. sinensis (Xiao et al. 1999), Russian Sturgeon A. gueldenstaedtii (Celikkale et al. 2005), Persian Sturgeon A. persicus (Mohseni et al. 2007; Babaei et al. 2011), Lake Sturgeon A. fulvescens (Fajfer et al. 1999), Green Sturgeon A. medirostris (Mayfield and Cech 2004), Beluga Sturgeon Huso huso (Mohseni et al. 2006), and Shovelnose Sturgeon Scaphirhynchus platorynchus (Kappenman et al. 2009). Despite the breadth of previous research objectives, limited information is available regarding the optimization of protein: energy ratios for the grow out of juvenile sturgeon species. Additionally, no literature is available describing specific nutritional requirements of the uniquely freshwater Scaphirhynchus genus of sturgeon. The Scaphirhynchus genus comprises the Pallid Sturgeon S. albus, Alabama Sturgeon S. suttkusi, and Shovelnose Sturgeon. These fish are endemic to the Mississippi and Missouri river basins of North America that flow into the Gulf of Mexico (Keenlyne1997; Tripp et al. 2009a). As with other sturgeon species, the Pallid and Shovelnose Sturgeon are prized for their meat and roe (Tripp et al. 2009b; Seibert et al. 2011). In addition to commercial harvest pressure, lack of recruitment due to impoundment and channelization led to the U.S. federal listing of the Pallid Sturgeon as an endangered species in 1990 (USFWS 1990). Subsequently, in 2010 the Shovelnose Sturgeon was granted limited protection as a threatened species under the U.S. Endangered Species Act of 1973 in regions where it cohabitates with the Pallid Sturgeon (USFWS 2010). As a result, interest in sturgeon culture has developed to supplement and replace harvest of dwindling wild stocks protected by increasingly tight harvest restrictions. Optimization of the dietary protein: energy ratio for Pallid Sturgeon will aid in the development of sustainable sturgeon culture diets, which minimize waste and maximize growth and condition. The present research sets the groundwork for developing juvenile Scaphirhynchus sturgeon diets by providing the first evaluation of the dietary protein: energy ratios.