Metamorphic and post-settlement success of Holothuria scabra reared on microalgal concentrates compared with live microalgae

Abstract

Commercially available microalgae concentrates used in the culture of Holothuria scabra were compared to live microalgae. Larvae were reared under a fixed daily feeding ration of 20,000 cells mL− 1 using three commercial concentrates (Instant Algae®, Reed Mariculture Inc.): TW 1200 (Thalassiosira weisflogii; TW), TISO 1800 (Isochrysis sp.; TISO), and Shellfish 1800 (mixed diatom; SHELL) and compared with live Chaetoceros calcitrans (CC). The efficacy of diets was evaluated based on larval growth, development, and survival to late auricularia (LA) with hyaline spheres (HS) and post settled juveniles. The average size in TISO (855.7 ± 62.67µm) was significantly higher compared with SHELL. In contrast, larvae in TW did not progress beyond middle LA. Development was much better in CC compared to all the microalgal concentrates. Larvae fed CC reached LA stage earlier, attained significantly larger sizes (1028.43 ± 19.38 µm), and have significantly higher incidence and size of HS. Better metamorphic and settlement performance of larvae in CC and SHELL treatment maybe related to the higher carbohydrate content in these feeds. Average post settled juveniles in CC (9,268 ± 2,183.79) were over three times more in SHELL, and an order of magnitude for TISO. Higher costs per juvenile can be largely attributed to the low post settled juvenile yield and longer feeding duration when using microalgae concentrates. The estimated cost of producing each juvenile using SHELL is $0.036 and $0.210 for TISO, compared to $0.009 per juvenile using CC. Opportunities to optimize the use of microalgal concentrates as supplemental feeds are discussed.