Advanced broodstock diets for the mangrove red snapper and a potential importance of arachidonic acid in eggs and fry

Mangrove red snapper fed advanced broodstock diets containing squid meal and squid oil exhibited higher hatching rates, cumulative survival and survival activity index than those fed a basal diet or a basal diet supplemented with mixture of antioxidants. On the other hand, fatty acid analyses of ovaries and fry of wild fish and eggs and larvae of broodstock fed raw fish revealed high arachidonic acid (ARA) and docosahexaenoic acid (DHA) levels and relatively lower eicosapentaenoic acid (EPA) levels consequently showing high ARA/EPA and DHA/EPA ratios compared to cold water species. This suggests that ARA may be nutritionally more important for egg and larval development and survival in tropical marine fish and its supplementation in broodstock diets may enhance reproductive performance of mangrove red snapper

Arachidonic acid is a major fatty acid in gonads of coral reef fishes and improves larval survival of rabbitfish Sigunus gutattus

The supply of wild fry of coral reef fishes for aquaculture has resulted in the deterioration of their natural stock status, causing public concern. Through a series of studies on the establishment of artificial-fry production technologies for coral reef fishes, we found that ovary, testis, eggs and fry of coral reef fishes have high or intermediate levels of arachidonic acid (ArA), which is a relatively minor component in temperate and cold-water species. In gonadal polar lipids of selected coral reef, in particular demersal fishes (19 species), ArA, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) levels ranged from 6.0% to 19.4%, from 0.9% to 6.2%, and from 7.9% to 27.8%, respectively. It is notable that the major highly unsaturated fatty acids (HUFA) of polar lipids in all coral reef fish gonads are DHA and ArA (not EPA) in a ratio of about 2:1. This result allowed us to speculate that not only DHA but also ArA may be nutritionally much important for egg development and larval growth in coral reef fishes. Thus, feeding trials were conducted to investigate the effects of dietary ArA supplementation on reproductive performance of coral reef rabbitfish (Siganus guttatus) broodstock. The number of spawning and the number of hatched larvae tended to be better in broodstock fed diets with ArA than in those fed a diet without ArA. Next, larval rearing tests were conducted to investigate survival and growth in rabbitfish fry fed live rotifers which had been enriched with or without ArA. Fry fed the rotifers enriched with a combination of DHA Protein Selco (Inve Aquaculture, Baasrode, Belgium) + 5% ArA (VEVODAR CRUDE ARACHIDONIC OIL, DSM Food Specialties, Delft, the Netherlands) showed significantly the best survival (44.4 ± 4.5% for Day 17 fry), although growth was not different among treatments. The present study indicates that ArA is not a minor component in coral reef fishes, and that dietary ArA is very promising for the improvement of fry production technologies of the coral reef fishes.The present study was financially supported by the collaborative project titled “Studies on Sustainable Production Systems of Aquatic Animals in Brackish Mangrove Areas” between Japan International Research Center for Agricultural Sciences, Japan and the Aquaculture Department, SEAFDEC, Philippines

Hatchery-produced milkfish (Chanos chanos) fry should be fed docosahexaenoic acid-enriched live food: A case of the difficulty in the transfer of improved aquaculture technology in the Philippines

Levels of highly-unsaturated fatty acids, the most important nutritional factors in fry production of marine fish, were compared between hatchery-produced and wild-caught milkfish Chanos chanos fry. The most striking difference found between the fry was in docosahexaenoic acid (DHA: 22:6n-3) levels: DHA levels in hatchery-produced fry were only 37% and 18% of those in wild-caught fry in the polar lipids and neutral lipids, respectively. However, high DHA levels were detected in ovary and spawned eggs from hatchery-reared broodstock. Investigation on the time course change in DHA levels of hatchery-produced fry revealed that the DHA levels of polar lipids drastically declined from 25% at day 0 posthatching to 5% at day 14 posthatching. Nannochloropsis sp. and rotifers Brachionus sp., which were used as live food from day 2 to day 14, did not contain DHA with relatively high eicosapentaenoic acid (EPA: 20:5n-3) levels. DHA level was restored to 13% in 45-day old fry by feeding of formulated diets with a substantial amount of DHA from day 15. Thus, the lack of DHA in the live food appears to lead to the low DHA level in hatchery-produced fry. On the other hand, the cost of DHA enrichment for one milkfish fry was estimated to be 2.6 Philippines centavos, which is equivalent to about 10% of the market price of milkfish fry. The increase of the production cost might not be accepted in domestic hatcheries under competitive marketing with imported fry. Financial and marketing support by the government will be one of the measures to encourage the stable production of domestic milkfish fry with high quality in the Philippines. It is also necessary to conduct institutional campaigns to inform local fry producers and milkfish farmers of the importance of DHA-enrichment

Arachidonic acid distribution in seaweed, seagrass, invertebrates and dugong in coral reef areas in the Philippines

Arachidonic acid (ArA) was not a minor component, and ArA distributes widely in coral reef organisms. Seagrass had high linoleic acid and linolenic acid levels with low Ara, EPA and DHA levels, while some species of seaweed had intermediate or high ArA levels (5% to 12%). In starfish, sea cucumber and some species of corals, ArA was the first major fatty acid (20% to 30%), but DHA levels were very low. Bivalves, abalone and shrimps had intermediate ArA levels. Total lipids of abdominal muscle and liver of dugong had respectively ArA levels of 7.8% and 11.0%, which were higher than EPA levels (2.4% and 1.6%), but DHA levels (0.4% and 2.3%) were low. It is clear that ArA is a major fatty acid in coral reef animals. The present results suggest that the existence of an ArA-rich food chain may be widespread in coral reef areas, and that the widespread existence of ArA-rich food chain may lead to intermediate or high ArA contents in tropical species

Arachidonic acid distribution in mangrove organisms in the Philippines, Malaysia and Japan

There has been little information on the importance of arachidonic acid (20:4n-6, ArA) in fish and other aquatic animals, although the importance of eicosapentaenoic acid (20:5n-3, EPA) and docosahexaenoic acid (22:6n-3, DHA) has been highlighted. The present study was conducted to investigate essential fatty acid composition, especially ArA distribution in mangrove organisms in the Philippines, Malaysia and Japan. The overall results revealed that ArA was not a minor component in mangrove organisms, and that the existence of ArA in mangrove organisms is widespread, irrespective of the differences in species, geography and environment. Both mangrove green and dead leaves were rich in linoleic acid (18:2n-6 LA) and linolenic acid (18:3n-3 LNA), which are respectively precursors of ArA and EPA & DHA, although ArA, EPA and DHA were not detected in these leaves. Mangrove invertebrates contained intermediate to high ArA. Especially, mangrove snails had very high ArA levels with low DHA levels, and thus the snails appeared promising as a new dietary source rich in ArA. Most of fishes in mangrove areas showed entirely higher ArA levels than EPA levels. As overall traits, ArA/EPA ratios of mangrove animals were higher than those of cold and temperate water species .The present results suggest that ArA may be nutritionally more important for egg and larval development, and that its supplementation in diets can enhance the development of broodstock management and fry production technologies in mangrove areas. The information of the present report can be used as a guideline for development of appropriate broodstock and/or larval diets in mangrove areas