REPLACEMENT OF FISH OIL BY CAMELINA AND BLACK SOLDIER FLY LARVAE OILS IN DIETS FOR JUVENILE TOTOABA Totoaba macdonaldi

F ish oil  (FO)  has been used  for decades as the major l ipid  source in aquafeed s; it is valued because of the richness  in highly unsaturated fatty acids (HUFA), such as docosahexaenoic (DHA, 22:6n-3) and eicosapentae noic (EPA, 20:5n-3)  acids, that promote health, growth, and fillet quality of cultured marine organisms . Research on a lternative sources of lipid to replace FO has increased to address sustainability, cost, and availability concerns. Among them, Camelina sativa  and Hermetia illucens larvae oil s have been tested in marine fish diets with promising results. Camelina  oil contains  up to 45%  of α- linolenic acid (18:3n-3)  and high n-3/n-6 ratio, highly desirable  characteristics for an alternative lipid source. B lack soldier fly larvae  (BSFL)  oil appears to be more palatable or attractable to fis h compared to vegetable oils; it is rich in lauric (12:0) and linoleic (18:2n-6) acids, though th is profile can be improved using  substrates rich in omega-3 fatty acids. Totoaba macdonaldi is a newly cultured marine carnivorous fish ,  endemic to the Gulf of California,  Mexico, whose industry is still developing. In the p resent study, the use of camelina and BSFL oils to replace FO in diets for T. macdonaldi was evaluated.

Four isoproteic (51%) and isolipidic (14%) diets were formulated based on a 2×2 factorial design  with two lipid sources,  camelina and  BSFL oils, each tested at two levels of replacement, 30 and 60%. A control diet containing 100% FO as the  lipid source was used as a reference . Fish w ith an overall initial mean weight of 3.0 ± 0.1 g were stocked at a density of 100 fish/m³ .  Each experimental diet was randomly assigned to five replicate tanks. G rowth performance  and feed utilization were evaluated in terms of weight gain (WG) , survival (arcsine square root transformed before analysis), and feed efficiency (FE), among other variables . Proximate composition and fatty acid profile of experi mental diets, muscle, and liver were determined. D ata were subjected to two-way ANOVA (P≤0.05), and Tukey's  HSD test was used as the mean separation procedure . In addition, Dunnett's test was used to compare the treatment means to the control mean.

After 7 weeks,  fish fed 30% replacement of FO by BSFL oil attained similar growth  as fish fed  the 100% FO control diet (Table 1).  Muscle tissue reflected the fatty acid pro file of the  experimental diets;  fish fed BSFL oil  showed a high content of 12:0  (0.11 mg g−1  of wet tissue ), while 18:3n-3 was higher in those fed camelina oil  (0.27 mg g−1  of wet tissue). The fillet of fish fed 30% BSFL  oil preserved their nutritional quality, with similar  atherogenicity and thrombogenicity indices as the control fish.

Results of this study suggest that 30% of FO can be  successfully  replaced by BSFL oil in diets for  T. macdonaldi without affecting  growth and preserving its nutritional value.