EVALUATION OF BLACK SOLDIER FLY Hermetia illucens LARVAE AS A FISH MEAL REPLACEMENT IN PRACTICAL DIETS FOR LARGEMOUTH BASS Micropterus salmoides

Protein meal derived from the larvae of the black soldier fly (Hermetia illucens) (BSFL) shows promise as an alternative protein source in the diets of a variety of fish species. The larvae are capable of assimilating organic materials from food waste or food and beverage manufacturing. The resulting BSFL can then be turned into a valuable feedstuff. Carnivorous fish species like the largemouth bass (LMB) (Micropterus salmoides) require higher protein levels than omnivores and protein is the most expensive ingredient in aquatic diets. Fish meal has traditionally been the main source of protein in fish diets, however this source is derived from natural stocks that have reached maximum yields. Therefore, alternative protein sources of high quality must be developed to support sustainable growth in aquaculture.

A 12 week study is being conducted to determine if BSFL can substitute for fish meal in diets for LMB. Five test diets were formulated to be isonitrogenous and isocaloric (42% protein and 12% fat). The control diet derived the majority of its protein from sardine fish meal. The four experimental diets contained decreasing percentages of fish meal and increasing inclusions of BSFL protein (25%, 50%, 75% and 100%). The research is performed in a recirculating aquaculture system where 20, 114-L glass aquaria were randomly stocked with 25 LMB fingerlings (8.4 ±1.9 g) each. There are four replicate tanks per dietary treatment. Dissolved oxygen, pH and temperature are logged daily and water quality data on alkalinity, salinity, total ammonia and nitrite is monitored bi-weekly. The study will conclude in October 2016. At stocking, baseline fish and diet samples were taken. Whole body proximate analysis will determine the lipid, moisture and ash content of the baseline fish. Amino acid and fatty acid profiles will be analyzed on the diets and amino acid profiles will be analyzed on fish. At the conclusion of the experiment; fish in each aquarium will be removed, measured for total length and weighed. From each aquarium ten random sample fish will be analyzed for whole body proximate composition and amino acid profiles. The overall growth performance variables measured for the fish are specific growth rate, feed conversion ratio, apparent protein utilization and protein efficiency ratio.  Specific growth rate (SGR, % body wt/d) was calculated from SGR = [(ln Wf - ln Wi) / t] X 100, where Wf = final weight (g), Wi = initial weight (g), and t = time in days. Feed conversion ratio was calculated as FCR = total diet fed (g) / total wet weight gain (g). Apparent protein utilization APU =[(final body protein - initial body protein) X100] / total protein fed. Protein efficiency ratio was calculated as PER = (final body weight - initial body weight) / protein fed.

The potential to reduce or stabilize feed costs by evaluating an alternative protein sources could be important in expanding aquaculture of LMB as well as other aquaculture species.