Performance of Endangered Bonytails Fed Four Commercial Diets

Abstract

The bonytail Gila elegans is a critically endangered cyprinid that is endemic to the southwestern United States, where it is cultured in ponds and water reuse systems as part of recovery efforts. Unlike in extensive outdoor pond culture, where natural food productivity plays a primary nutritional role, manufactured feed must provide complete nourishment for fish reared indoors in recirculating systems. The objective of this study was to determine the effects of diet on the growth and survival of juvenile bonytails fed four commercially available feeds over a 120-d period. The four treatment diets were identified as a catfish diet, a trout diet, a high-protein shrimp diet, and a low-protein shrimp diet. Significant (P , 0.05) differences in growth among treatments were observed on sampling day 102. By day 120, the average weight of fish fed the high-protein shrimp diet (36.3 g) was significantly higher than the weights of fish fed the catfish (26.6 g), trout (24.7 g), and low-protein shrimp diets (24.2 g). The specific growth rates measured on days 102 and 120 were significantly greater for bonytails fed the high-protein shrimp diet than for fish fed the other treatments. The feed conversion ratio of fish fed the high-protein shrimp diet was significantly better than those of fish fed the trout and low-protein shrimp diets, while the protein efficiency ratio and apparent net protein retention were generally higher in the high-and low-protein shrimp diet treatment groups than in the other two treatment groups. Overall survival was high (93.5%) and did not differ significantly among treatment groups (P ! 0.05) through 120 d.

Polyculture of Endangered Bonytails and Razorback Suckers in Recirculated Water

“…Water temperature was maintained within this range as an energy conservation measure due to the low ambient temperature of well water at the study site (water chemistry reported by Pioneer Laboratories, Inc., Pensacola, Florida). However, mean 120-d TL (163.4 mm), wet weight (37.0 g), and SGR (0.59%) of the small bonytails across all razorback sucker densities are consistent with results (161.2 mm, 36.3 g, and 0.51%, respectively) that Henne et al (2006) reported for monocultured bonytails of comparable initial size that were fed the same diet in a previous 120-d experiment conducted under similar conditions, including water temperature. The size and growth rates of razorback suckers were not measurably affected by the presence of either bonytail size-class.…”

“…Survival of razorback suckers was not adversely affected by polyculture conditions, as no mortalities were recorded in any treatment during the study. Bonytail survival was high among the three razorback sucker density treatments and was comparable to 120-d survival (mean ¼ 94%; range ¼ 84-97%) of monocultured bonytails in a previous study conducted under similar experimental conditions (Henne et al 2006). However, the significantly lower bonytail survival observed in the small bonytail-low razorback sucker density treatment and the suggestion of a weak interactive effect (P ¼ 0.0435) on bonytail survival should not be ignored.…”

“…All fish were hand fed a commercially available, sinking shrimp production feed (2.4-mm diameter; 40% protein, 15% lipid; Zeigler Brothers, Inc., Gardners, Pennsylvania). Use of this feed in bonytails was previously evaluated (Henne et al 2006). Fish were fed to satiation four times daily (;0700, 0900, 1200, and 1400 hours).…”

Endangered species managing endangered species: Polyculture of piscivorous Colorado Pikeminnow (Ptychocheilus lucius) with production Bonytail (Gila elegans) to control recruitment and increase growth rates

“…Optimizing growth rates has been a specific recovery objective for Bonytail in the lower Colorado River because conservation goals associated with augmentation require a minimum stocking size in an effort to increase post‐release survival (Bureau of Reclamation, ; Lower Colorado River Multi‐Species Conservation Program, ). Although several studies have evaluated aquaculture techniques (i.e., cage culture, diet improvement, polyculture and thermal regimes) to facilitate Bonytail growth (Henne et al, ; Kappenman et al, ; Sowka & Brunkow, ), the effect of uncontrolled recruitment on growth rates of production fish has not been evaluated. The use of biological controls has been shown to greatly reduce densities (Kavanagh & Olson, ; Ward & Slaney, ; Ward et al, ; Westers, ), and, indeed, our results demonstrated Colorado Pikeminnow to be effective at reducing total biomass.…”

“…Although several studies have evaluated aquaculture techniques (i.e., cage culture, diet improvement, polyculture and thermal regimes) to facilitate Bonytail growth (Henne et al, 2007(Henne et al, , 2006Kappenman et al, 2012;Sowka & Brunkow, 1999), the effect of uncontrolled recruitment on growth rates of production fish has not been evaluated. The use of biological controls has been shown to greatly reduce densities (Kavanagh & Olson, 2014;Ward & Slaney, 1988;Ward et al, 1989;Westers, 2001), We observed a positive effect of initial size in both the ∆TL and ∆g models, indicating the starting sizes of fish had a strong effect on their growth over time.…”