Essential fatty acid requirements in tropical and cold-water marine fish larvae and juveniles

Authors: MEJRI, SAHAR - Harbor Branch Oceanographic Institute; RICHE, MARTIN - Harbor Branch Oceanographic Institute; WILLS, PAUL - Harbor Branch Oceanographic Institute; TREMBLAY, REJEAN - Rimouski Sea Sciences Institute; AUDET, CELINE - Rimouski Sea Sciences Institute

Submitted to: Frontiers in Marine Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2021
Publication Date: 5/19/2021
Citation: Mejri, S., Riche, M., Wills, P., Tremblay, R., Audet, C. 2021. Essential fatty acid requirements in tropical and cold-water marine fish larvae and juveniles. Frontiers in Marine Science. 8:680003. https://doi.org/10.3389/fmars.2021.680003.
DOI: https://doi.org/10.3389/fmars.2021.680003

Interpretive Summary: The wide variety of natural marine habitats presents constant challenges in the field of aquaculture. Developing methods in aquaculture requires a detailed understanding of various dynamic ecological processes including embryological development. In order to encourage the survival of captive species at the larval stage, research must be conducted to characterize diets and developmental processes. This review paper will focus on currently published research and primarily results from our laboratory regarding the diet during larval development of the Florida Pompano (Trachinotus carolinus) and the North American Winter Flounder (Pseudopleuronectes americanus).

Technical Abstract: To improve survival at early developmental stages (larvae and juveniles) of captive fish species, essential nutrients (i.e., essential fatty acids [EFA]) need to be identified. The physiological needs are likely to be different among species, particularly among those using different thermal habitats, because lipids are largely used to maintain cell membrane integrity (homeoviscous adaptation) in fishes. This review paper will focus on currently published research and the main results from our laboratories regarding optimum qualitative EFA requirements during larval and early juvenile stages in a warm-water marine species, the Florida pompano (Trachinotus carolinus), and a cold-water marine species, the winter flounder (Pseudopleuronectes americanus). To identify the qualitative optimal EFA requirements, we calculated the ratio of certain fatty acids (FA) in larval or early juvenile tissues to total FA present in the diet. This ratio indicates whether a specific FA from prey is selectively incorporated by larvae and juveniles. Overall, we found that young larvae from both cold- and warm-water species have greater demands for n-3 and n-6 highly unsaturated fatty acids (HUFA) than do larvae at weaning stages. However, the qualitative EFA requirements of the cold-water species at all early developmental stages were higher than those of the warm-water species. Enriched rotifer diets provided satisfactory amounts of omega 3 and omega 6 in Florida pompano, with small selective retention for docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (ARA), suggesting a potential minor diet deficiency in these EFA. There were higher deficiencies in the cold-water species fed enriched rotifers, as demonstrated by the higher selective retentions of all EFA (DHA, EPA, and ARA), with the exception of larvae fed with copepods. The physiological needs in EFA for juvenile development seemed to be better met for both species when they were fed micro pellets. From the beginning of settlement and in young juveniles, qualitative values of 12% DHA, 10% EPA, 5% ARA, and 40% PUFA of total FA seem to be required for winter flounder juvenile development. In Florida pompano, these requirements could be met until larger juvenile stages, with 15% DHA, 3% EPA, 2% ARA, 2% DPA, and total PUFA below 30% of total FA. This review was done to aid future research aiming to develop nutritionally balanced microdiets or live-prey enrichment diets to satisfy the physiological requirements of captive tropical and cold-water marine fish species.