Use of biomass of the marine microalga Isochrysis galbana in the nutrition of goldfish (Carassius auratus) larvae as source of protein and vitamins Paula Coutinho 1 , Paulo Rema 2 , Ana Otero 1 , Oscar Pereira 3 & Jaime Fa L bregas 1 1 Departamento de Microbiolog|¤a y Parasitolog|¤a, Facultad de Farmacia, University of Santiago de Compostela, Santiago de Compostela, Spain 2 CIIMAR ^ University of Porto, Rua do Campo Alegre, Porto, Portugal 3 CECAV ^ University of Tra Ł s-os-Montes e Alto Douro, ApartadoVila Real, Portugal Correspondence: P Coutinho, Departamento de Microbiolog|¤a y Parasitolog|¤a, Facultad de Farmacia, University of Santiago de Compos- tela,15782 Santiago de Compostela, Spain. E-mail: coutinho@usc.es Abstract The e¡ect of the replacement of ¢sh protein hidroli- zate and vitamin premix by freeze-dried biomass of the marine microalga Isochrysis galbana in the feed for gold¢sh ( Carassius auratus ) larvae was tested. Lar- vae (3.4  0.7 mg) were fed with three experimental microparticulated diets that di¡er from each other in the percentage of replacement of ¢sh protein hidroli- zate (25% or100%) or vitamin premix by I. galbana biomass. The control diet and the diet containing microalgae biomass as a substitute of 25% of ¢sh protein hidrolizate (MP 25 ) presented the highest sur- vival, being almost 100%, with no signi¢cant di¡er- ences between them. Survival in diets in which 100% of ¢sh protein hidrolizate (MP 100 ) or vitamin premix (MV) had been substituted by microalgal bio- mass was 78% and 66% respectively. Growth, mea- sured as weight, was lower than with the control diet in all treatments in which microalgal biomass was included, with lowest results being obtained with the MP 100 diet. Di¡erences between treatments and control were lower when growth was measured as length. The harvesting and processing microalgae biomass is crucial to maintain the nutritive value and could be the cause for the obtained results. Keywords: Isochrysis galbana, gold¢sh larvae, growth, survival Introduction Microalgae play a vital role in the rearing of aquatic animals and have a special interest for aquaculture. Marine microalgae biomass can be used in animal nutrition as a source of single cell protein (SCP) (Fa Ł b- regas & Herrero1986) or as a nutritive complement in animal feeds (Fa Ł bregas & Herrero1986,1990; Mokady, Abramovici & Cogan 1989; Markovits, Conejeros, Lo- pez & Lutz 1992; Herrero, Abalde & Fa Ł bregas 1993). Microbial proteins have been successfully used as supplement in the alimentation of chicken (5^10%), swine (10^20%) and ¢sh such as rainbow trout, carp and eel (30^50%) (Kihlberg1972).The strategic use of algae in the ¢rst-feeding process may enhance the rearing success of larvae, including survival, growth and fry quality (Reitain, Rainuzzo, Oie & Olsen 1997). Algae can also improve the assimilation of micropar- ticulate diets when added to the rearing tanks of red drum larvae ( Sciaenops ocellatus ) (Lazo, Dinis, Holt, Faulk & Arnold 2000). The marine microalga Iso- chrysis galbana is rich in crude protein and in essen- tial fatty acids (EPA) (Otero, Garc|¤a, Morales, Ara Ł n& Fa Ł bregas 1997). Isochrysis galbana as other species of the Prymnesiophyceae is also an important source of fat-soluble (vitamin A and vitamin E or a-tocopherol), biotin, ascorbic acid and B group vitamins (folic acid, nicotinic acid, pantothenic acid, biotin, thiamin, ri- bo£avin, pyridoxine and cobalamin) (Fa Ł bregas & Herrero 1990; DeRoeck-Holtzhauer, Claire, Besdin, Amicel & Derrien 1993; De Roeck-Holtzhauer, Claire, Bresdin, Amicel & Derrien 1993; Brown, Je¡rey,Volk- man & Dunstan1997; Brown, Mular, Miller, Farmer & Trenerry1999). This suggests that small quantities of this microalga can represent a non-conventional source of vitamins for animal nutrition, as well as a dietary supplement of proteins and fatty acids. The Aquaculture Research, 2006, 37, 793^798 doi: 10.1111/j.1365-2109.2006.01492.x r 2006 The Authors. Journal Compilation r 2006 Blackwell Publishing Ltd 793