Assessment of microalgae concentrate as diet for hard clam, Mercenaria mercenaria , larvae

Abstract

The on-site culture of live microalgae represents a major challenge for bivalve hatchery operations due to high cost and labour demands. This study evaluated the efficacy of commercially available microalgae concentrates as a partial or complete replacement diet for live microalgae for culture of the hard clam, Mercenaria mercenaria, larvae.Larvae were fed from D-larval stage to post-set, 2-14 days post fertilization (DPF).Larvae fed the complete replacement diets were significantly smaller than those fed partially replaced or live microalgae diets. Foot development was significantly delayed in larvae fed complete replacement diets compared to partially replaced or live microalgae diets. Although early survival (at 5 DPF) was similar among the treatments, final survival (at 14 DPF) varied significantly among treatments. The average final survival was 69%-77% for larvae fed live microalgae, 60%-61% for larvae fed partially replaced diets and 14%-16% for larvae fed complete replacement diets. These results suggest that a live microalgae diet could be partially replaced by a concentrate to feed hard clam larvae. However, complete replacement diet may be used only for a short duration (up to 3 days) without affecting survival.

Feasibility of Microalgal Concentrates for Production of Post Set Northern Quahogs, Mercenaria mercenaria and Sunray Venus Clams, Macrocallista nimbosa

“…Higher settlement and biofouling were also observed in this study at a greater frequency in tanks in which concentrates were fed compared with tanks receiving live microalgae only. This was noted previously with larval hard clams (Hassan et al 2021), even though concentrates were passed through a 20-μm screen prior to tank addition to circumvent clumping. Southgate et al (2016) also reported problems with the clumping of concentrates fed to winged pearl oysters.…”

“…For this study, two of these products (ISO 1800 and Shellfish Diet 1800) were chosen, as a previous study showed that the survival and growth of hard clam larvae were significantly decreased with both (Hassan et al 2021). Both products are advocated for use with bivalve larvae, juveniles, and broodstock; however, the Shellfish Diet contains a mixture of microalgal species, including some of which are diatoms that may be too large for larvae to ingest.…”

“…The main benefits of concentrates are convenience and a storage life of up to several months when refrigerated (Welladsen et al 2014, Camacho-Rodríguez et al 2016). Several studies have examined the effects on the growth and survival of larvae and post set bivalves fed processed microalgal diets, including the eastern oyster, Crassostrea virginica (Rikard & Walton 2012), the Pacific oyster, C. gigas (McCausland et al 1999, Brown & Robert 2002), the Sydney rock oyster, Saccostrea glomerata (Heasman et al 2000), the winged pearl oyster, Pteria penguin (Southgate et al 2016), the giant clam, Tridacna noae (Southgate et al 2017), the carpet shell clam, Ruditapes decussatus (Albentosa et al 1997), the Manila clam, Tapes philippinarum (Önal et al 2005), and the hard clam (Espinosa & Allam 2006, Hassan et al 2021).…”

Potential for Concentrated Microalgae as Replacement Diets for Juvenile Green-Lipped Mussels, Perna canaliculus

“…Partial replacement of live microalgae using diferent types of formulated diets has been reported for facilitating the aquaculture of a number of species of bivalves. For example, yeast-based diets [21], lipid emulsion [22], microcapsule [23], bacteria [24], and microalgal pastes [25,26] have been used to partially substitute live microalgae for rearing juvenile shellfsh. For example, a replacement of 20% of the dried microalgae Tetraselmis suecica, 80% of yeast and up to 81% of mixed microcapsules and yeast has been found to be a satisfactory diet for juvenile oysters (Crassostrea gigas and Ostrea edulis) and the clams (Mercenaria mercenaria and Ruditapes philippinarum) [15].…”

Growth, survival and fatty acid profile of hard clam, Mercenaria mercenaria, juveniles fed live microalgae diets

“…Past research has evaluated the correlation between the gross biochemical composition of the diet and juvenile hard clam growth (Epifanio, 1979; Wikfors et al., 1992). To improve understanding of the dietary requirements for hard clam hatchery production, our lab has recently evaluated live microalgae and microalgae concentrate diets for larvae (Hassan et al., 2021a, 2021b) and the variations of filtration and ingestion rates of various microalgae species by larvae and juveniles (Hassan et al., 2022). This study aims to identify an optimal microalgae diet based on growth, survival and fatty acid profile for the culture of hard clam juveniles using combinations of T. lutea , P. lutheri , Chaetoceros gracilis and Cyclotella nana .…”