Ulva clathrata meal (2%) was supplemented in a fresh maturation diet for Litopenaeus vannamei broodstock in a commercial larval facility and its effects on reproductive performance, histology and histochemistry of gonad, and biochemical composition of gonad, hepatopancreas, and muscle were analysed. Females that were given Ulva in the diet had reduced mortality compared to controls, with no differences in males. Females fed Ulva also had bigger oocytes but only those in late vitellogenesis (+7%, p < 0.01) and postvitellogenesis (+15%, p < 0.01); they also had a higher proportion of late vitellogenic oocytes in maturation stage II, and a bigger area occupied by cortical rods. No significant differences were found for the proportion of previtellogenic or early vitellogenic oocytes per maturation stage or as a result of Ulva. Females fed Ulva had higher levels of lipids in ovary (+35%, p < 0.05), with no significant differences in biochemical reserves in hepatopancreas or muscle. The total number of eggs (+5%, p < 0.01), nauplii per spawn (+18%, p < 0.01), and hatching rate (+13%, p < 0.01) during the productive cycle were higher for Ulva fed shrimp. Individual follow‐up of marked females during the productive cycle showed a decreased reproductive exhaustion in females fed Ulva over consecutive spawns. Apparently, U. clathrata stimulates advanced vitellogenesis by improving lipid accumulation in gonads, and this in turn increases reproductive performance: inclusion of this algae in shrimp diet could be used to decrease reproductive exhaustion during production.

The effect of supplementing dehydrated seaweed Ulva clathrata (20 g/kg) in the squid fraction of a formulated fresh diet on the reproductive performance of Litopenaeus vannamei broodstock was evaluated in two commercial hatcheries (A and B).The origin of broodstock, use of ablation on females, tank/culture conditions (for maturation, spawning, and larval rearing) were different between hatcheries. Daily mortality was higher (p < .01) for females in the control group compared to Ulvafed group of hatchery A, where females were ablated. No differences in mortality were found for unablated females in hatchery B, or with males from either hatchery.In hatchery A, broodstock fed Ulva produced more eggs (an increase in +5% compared to control, p < .05) and nauplii per female (+18%, p < .01). In hatchery B, broodstock fed Ulva produced significantly more eggs (+26%, p < .05) and nauplii per day (+33%, p < .05). In hatcheries A and B, eggs from broodstock fed Ulva had increased hatching rates (+13 and +7%, respectively, p < .001 in both cases). The number of spawns per day had a tendency to be higher in broodstock fed Ulva in both hatcheries, but the difference did not reach statistical significance (+14% for hatchery A and +20% for hatchery B). Dehydrated U. clathrata appears therefore as a functional additive in L. vannamei maturation diets that enhances the reproductive performance at commercial scale, regardless of the management conditions. K E Y W O R D S egg production, eyestalk ablation, hatching rate, reproductive performance, seaweed, spawn

No abstract