Dietary supplementation with the microalgae Parietochloris incisa increases survival and stress resistance in guppy ( Poecilia reticulata ) fry

Dietary enrichments with the arachidonic acid (ARA)‐rich microalga, Parietochloris incisa , on the survival of guppy ( Poecilia reticulata ) fry were examined. Diets were applied via Artemia enrichment to fish from two commercial farms for 34 and 36 days of experimental period (trials 1 and 2, respectively). In trial 1, Artemia nauplii were enriched with dry biomass of whole algal cells at 0 (control), 0.1, 0.2 and 0.4 mg mL −1 . Fry fed with Artemia enriched with 0.4 mg mL −1 demonstrated the lowest mortality rates (24% and 1% in farms 1 and 2, respectively) compared with controls (36% and 13% in farms 1 and 2, respectively). In trial 2, fry were fed with Artemia , enriched with whole algal cells (0.4 mg ml −1 ), algal hexane extract (HE; containing primarily ARA‐rich triacylglycerols and β‐carotene; 0.19 mg ml −1 ) or the extraction residue (0.28 mg ml −1 ). Acute stress (5 min air exposure) was applied after 18 days. The lowest mortality was recorded in the whole alga‐fed group (av. 26% and 2.6% in farms 1 and 2, respectively), with a slightly, but not significantly higher mortality in the HE‐fed group (av. 29% and 6.2% in farms 1 and 2, respectively). Elevated lysozyme was associated with the reduced mortality. Overall, the use of P. incisa as a dietary supplement for guppy fry during their first month of life enhanced their survival and stress resistance.