Viability of dietary substitution of live microalgae with dry Ulva rigida in broodstock conditioning of the Pacific oyster (Crassostrea gigas)

The current study evaluated the microalgae replacement by dry macroalgae (Ulva rigida) in the reproductive success and biochemical composition of the Pacific oyster (Crassostrea gigas) during broodstock conditioning. Five nutritional regimes were tested: 100% macroalgae (diet 1), 50% macroalgae+50% microalgae (diet 2), 25% macroalgae+75% microalgae (diet 3) and 100% microalgae (diet 4). An unfed group was used as a negative control. The microalgae blend was composed of 33% Isochrysis galbana and 67% diatoms (75% Skeletonema costatum+25% Chaetoceros calcitrans). Gonadal maturation was reflected in the physiological condition of the individuals. All treatments, except diet 1, showed an increase in condition index and were fully matured at the end of the trial, with the best physiological condition observed in oysters fed diet 3 and diet 4. Protein and total lipid content increased during the conditioning period, whereas glycogen content decreased. Oysters conditioned with diet 3 had higher protein and total lipid content and lower glycogen content than the other treatments. In addition, diet 3 showed the highest percentage of viable veliger larvae. The current study demonstrated that it is possible to replace 25% of microalgae with macroalgae in the broodstock conditioning, minimizing the operative cost in bivalve hatcheries. © 2018. Published by The Company of Biologists

This work was supported by Project INNOVMAR-Innovation and Sustainability in the Management and Exploitation of Marine Resources [NORTE-01-0145-FEDER-000035] within the line ‘INSEAFOOD, Innovation and valorization of seafood products’, funded by the Northern Regional Operational Programme (NORTE2020) through the European Regional Development Fund. Postdoctoral fellowships were granted to authors T.G.T. [SFRH/BPD/89360/2012] and to author A.C.G. [ref. SFRH/ BPD/72777/2010], by Fundaçaõ para a Ciência e a Tecnologia (Portugal), under the auspices of ESF and Portuguese funds. Z.E.M. is grateful to the project [UID/QUI/ 50006/2013-POCI/01/0145/FEDER/007265] with support from Fundaçaõ para a Ciência e a Tecnologia/MEC through national funds and co-financed by European Regional Development Fund, under the Partnership Agreement PT2020. This work was partially supported by POCI-01-0145-FEDER-006939 [Laboratory for Process Engineering, Environment, Biotechnology and Energy—UID/EQU/00511/2013], funded by the European Regional Development Fund, through COMPETE2020— Programa Operacional Competitividade e Internacionalizaçaõ and by national funds via Fundaçaõ para a Ciência e a Tecnologia, through project NORTE-01-0145-FEDER-000005—LEPABE-2-ECO-INNOVATION, supported by NORTE 2020, under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund.