Abstract
The giant river prawn (Macrobrachium rosenbergii) is one of the most farmed freshwater crustaceans in the world. Its global production has been stalling in the past decade due to the inconsistent quality of broodstock and hatchery-produced seeds. A better understanding of the role of nutrition in maturation diets will help overcome some of the production challenges. Arachidonic acid (20:4 n-6, ARA) is a fatty acid precursor of signaling molecules important for crustacean reproduction, prostaglandins E and F of the series II (PGE2 and PGF2α), and is often lacking in maturation diets of shrimp and prawns. We examined the effects of ARA in a combination of different fish oil (FO) and soybean oil (SO) blends on females’ reproductive performance and larval quality. Adult females (15.22 ± 0.13 g and 11.12 ± 0.09 cm) were fed six isonitrogenous and isolipidic diets containing one of two different base compositions (A or B), supplemented with one of three levels of Mortierella alpine-derived ARA (containing 40% active ARA): 0, 1 or 2% by ingredient weight. The two base diets differed in the percentages of (FO and SO with diet A containing 2% SO and 2% FO and diet B containing 2.5% SO and 1.5% FO, resulting in differences in proportional contents of dietary linoleic acid (18:2n-6, LOA) and docosahexaenoic acid (22:6n-3, DHA)). After the eight-week experiment, prawns fed diet B with 1 and 2% ARA supplement (B1 and B2) exhibited the highest gonadosomatic index (GSI), hepatosomatic index (HSI), egg clutch weight, fecundity, hatching rate, number of larvae, and reproductive effort compared to those fed other diets (p ≤ 0.05). Larvae from these two dietary treatments also had higher tolerance to low salinity (2 ppt). The maturation period was not significantly different among most treatments (p ≥ 0.05). ARA supplementation, regardless of the base diet, significantly improved GSI, HSI, egg clutch weight and fecundity. However, the diets with an enhanced ARA and LOA (B1 and B2) resulted in the best reproductive performance, egg hatchability and larval tolerance to low salinity. These dietary treatments also allow for effective accumulation of ARA and an n-3 lcPUFA, DHA in eggs and larvae.
Highlights
The giant river prawn, Macrobrachium rosenbergii, is an economically important species cultured in the Indo-Pacific region (New, 2005)
The present study investigated the effect of ARA and LOA given adequate n-3 lcPUFA (FO 1.5–2% of total ingredients) on the reproductive performance of M. rosenbergii female broodstock and larval quality, namely the tolerance to low salinity
We examined the effects of ARA supplementation in two base diets varying in percentages of fish oil (FO) and soybean oil (SO)
Summary
The giant river prawn, Macrobrachium rosenbergii, is an economically important species cultured in the Indo-Pacific region (New, 2005). It is one of the most farmed freshwater crustaceans in the world, especially in the tropical and subtropical regions. World-leading producers of this species included China, Bangladesh and Thailand (117,402, 43,713 and 18,168 tons) in 2013 (FAO, 2016). Its global production has been stalling in the past decade due to inconsistent quality of broodstock and hatchery-produced seeds. Even though the giant river prawn has been successfully domesticated for decades, seeds derived from hatcheries still vary in quantity and quality (Nhan et al, 2009)
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