A pilot study was conducted using basal commercial diets for largemouth bass ( Micropterus salmoides ) and koi ( Cyprinus carpio), respectively, with 10% of the basal diet substituted with either soy protein concentrate or a commercial mealworm product (YnMeal™) . The three diets for each species were similar to each other in analyzed proximate composition, and met the known nutrient requirements of the target species. A modest level of mealworm substitution was chosen for the pilot study due to the unknown nutrient availability or palatability of the product.
Concurrent feeding trials were conducted with largemouth bass (LMB) and koi in a recirculating aquaculture system. Juvenile fish were stocked in each of 4 replicate 19-L tanks per diet per species . The LMB (initial weight, 2 g), were stocked at 10 fish per tank, while koi (initial weight, 8 g) were stocked at 7 fish per tank. All fish were fed to satiation twice daily with their respective diets , and both trials lasted 10 weeks. At harvest, there were no differences in weight gain, survival (> 95%), feed intake or feed conversion ratio of LMB or koi among treatments. H ematological parameters and hepatosomatic indices of LMB were also similar among diets. We observed that the bass grew significantly more (nearly 800% weight increase) compared to the koi (about 20%) during the same time period and under uniform water quality conditions. Cyprinid growth can be limited at high densities, and tank size might have restricted koi growth. Therefore, after collecting final weights from the 10-week trial, the koi were restocked into larger tanks (240 L). They are being fed the same diets and will be monitored for additional growth prior to collection of hematological and body composition data. To date, r esults of this pilot study indicate that diets for LMB or koi with 10% mealworm protein are consumed as readily as the commercial or SPC diets, and support growth , feed conversion and survival equally well. Additional trials are planned with higher inclusion levels of YnMeal that will include cost/benefit analysis..