complete replacement of live microalgae by freeze-dried microalgae throughout the whole process of mass rearing seabream larvae. q 2001 Elsevier Science B.V. All rights reserved.
Keywords: Sparus aurata; Algae; Freeze-dried; Larvae; Enrichment; Rotifers; Seabream
1. Introduction
Ž .
The farming of gilthead seabream Sparus aurata
is an important commercial activity in the Mediterranean area. Hatchery production of juvenile seabream has
dramatically increased during the nineties, and it is a key factor in the development of this industry. Production in most hatcheries relies on feeding procedures, which are
based on the use of live phytoplankton and zooplankton species. One of the features of
Ž these feeding regimes is the use of the so-called Apseudogreen waterB Papandroulakis et
. al., 1996 , a method characterised by a regular supply of cultured microalgae to larval
tanks. The presence of microalgae in fish larval tanks has improved the growth and Ž
. survival of the larvae e.g. Naas et al., 1992; Reitan et al., 1993, 1997 . Green water is
achieved by adding small amounts of live microalgae, such as the Eustigmatophyceae, Ž
. Nannochloropsis species Yoshimatsu et al., 1995; Hernandez-Cruz et al., 1994 . The
´
Ž .
Haptophyceae, Isochrysis galbana, is also used Howell, 1979; Reitan et al., 1993 . This latter alga is a good nutritional complement when Nannochloropsis species are added to
Ž .
the larval rearing medium Mourente et al., 1993 . In order to reduce cost, it is desirable to replace live microalgae with long-term
preserved microalgae. Obtaining long-term preserved algae that provide good culture performance may also contribute to a future diversification and a higher level of
specialisation in the marine aquaculture industry. The use of preserved microalgae for Ž
. the rearing of marine fish larvae was mentioned by Yamasaki et al. 1989 , and Sommer
Ž .
et al. 1990 reviewed the potential of processed microalgae in aquaculture. One of the initial studies using dried algae was that carried out with juvenile bivalves by Laing and
Ž .
Millican 1992 . Rotifer culture has also been successfully carried out using preserved Ž
. Ž
algae that was either frozen Lubzens et al., 1995 , freeze-dried Yufera and Navarro,
´
. Ž
. 1995 or condensed Maruyama et al., 1997; Yoshimura et al., 1997 .
Larvae of S. aurata have been reared by the addition of frozen concentrated Ž
. microalgae during the first 20 days of culture Papandroulakis et al., 1996 . Later,
Ž .
Navarro and Sarasquete 1998 described the laboratory growth and the histology of S. aurata larvae during the first 15 days when freeze-dried Nannochloropsis oculata was
added to the rearing water. In the present study, the effect of using freeze-dried N. gaditana and I. galbana on growth and survival of mass reared seabream larvae is
described. The study was performed for a longer period than Navarro and Sarasquete Ž
. 1998 . In addition, three different regimes of rotifer enrichment were used in the
assessment of freeze-dried algae. The aim of both procedures was to obtain a better understanding of the effects of solely using freeze-dried microalgae. Thus, the influence
Ž of using dry algae during the first stage of rearing seabream larvae that of rotifer
. feeding was also evaluated during subsequent growth, up to an age when compound
diets are taken. Finally, changes in some parameters of water quality, caused by the presence of freeze-dried N. gaditana in the larval tanks, were considered.
2. Materials and methods
