Essential Fatty Acid Requirements in Tropical and Cold-Water Marine Fish Larvae and Juveniles

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.

The status of Florida pompano, Trachinotus carolinus, as a commercially ready species for U.S. marine aquaculture

“…Microdiets to evaluate such requirements are well accepted by Florida pompano (Rust et al, 2015). For a thorough review of estimated HUFA requirements in Florida pompano, the reader is referred to Mejri, Tremblay, Audet, Wills, and Riche (2021).…”

Muscle proximate composition of various food fish species and their nutritional significance: A review

“…Fat is considered as the third principal constituent in fish muscle and generally reported within the range from 6% to 20%, primarily located in the subcutaneous tissue, liver, muscle tissue, mesenteric tissue, belly flap and head (Moradi et al, 2011). The amount of lipid in the body of fish is considered a good index of future survival in a few species (Simpkins et al, 2003) and also a strong indicator of reproductive potential in some fish stocks (Mejri et al, 2021). These are regarded as one of the most crucial food reserves and the fat indices are also used as a means of describing the relationship between percent fat and water (Sinclair & Duncun, 1972); such type of relationship has also been extensively used by several researchers in various fishes (Ali et al, 2006; Naeem et al, 2011; Sutton et al, 2000).…”

Microalgal Diet Influences the Nutritive Quality and Reproductive Investment of the Cyclopoid Copepod Paracyclopina nana

“…The R diet alone resulted in a record DHA amount and one of the highest EPA amounts in P. nana. Many studies have pointed out the crucial roles of dietary DHA and EPA in fish development (Rainuzzo et al, 1997;Sargent et al, 1999;Izquierdo et al, 2000;Mejri et al, 2021). These particular fatty acids help maintain the function of visual and neural cells as well as cell membrane structure.…”

“…These particular fatty acids help maintain the function of visual and neural cells as well as cell membrane structure. Therefore, a diet deficient in DHA and EPA could lead to delayed growth and increased mortality in fish larvae (Mejri et al, 2021). DHA is of greater importance than EPA in marine fish as the former is present in high concentrations in fish larval tissue and promotes development to a greater extent than EPA.…”

“…Copepods have a high content of highly unsaturated fatty acids (HUFAs) such as docosahexaenoic acid (DHA) and eicosa-pentaenoic acid (EPA), which are particularly important nutrients for the development of fish larvae (Sargent et al, 1997;McEvoy et al, 1998;Pan et al, 2014;Mejri et al, 2021) thus, copepod species with a high lipid concentration and high fecundity are desirable from an aquaculture perspective. Copepod productivity can be measured by female fecundity and fatty acid content (Souissi et al, 2016;Lee et al, 2017), which is related to the amount of carbon that the copepods ingest.…”