170 Marine Macro- and Microalgae: An Overview
use of microalgae for adult fish feed utilization became increasingly important not only because of colour
but also due to enhancing health effects.
Fish feeding represents over 50% of operating costs in intensive aquaculture, with protein being
the most expensive dietary source. Therefore, continuous efforts have been made over the past decades
to find alternative protein sources for aqua feeds, with special emphasis on terrestrial plants. There are
limitations to the use of plant protein sources in fish diets, attributed to their deficiency in certain essential
amino acids, their content of anti-nutritional compounds and to palatability problems. Additionally, recent
interest in several crops as biodiesel raw materials has increased the world’s demand for these crops and
consequently, their price. Besides, its production requires agricultural land and freshwater, which are
becoming very limited resources, and therefore, there is a need to search for alternatives (Pereira et al.
2012). Several improvements on fish health status by feeding with microalgal biomass are detailed in
Table 5.
Apart from their general use in the growth phases previously described, and irrespective of the fish,
shrimp, or mollusc species under farming, sensitive periods of the production cycle where microalgae as
functional ingredients could be highly valued are:
i) Early feeding stages: microalgae are successfully used for larval nutrition, either for direct
consumption, in the case of molluscs and penaeid shrimp, or indirectly, as food for the live prey
(rotifers, Artemia or copepods) fed to small fish larvae. They are also been used during rearing
larvae and juveniles stages of commercially important molluscs, penaeid prawn larvae, crustaceans,
and fish. Although nutritional requirements for some target species have been defined, no set of
nutritional criteria have yet been advanced. Generally, the microalgae must be non-toxic, in an
acceptable size for ingestion, the cell wall should be digestible, and with sufficient biochemical
constituents. Protein content and lipid quality are major factors determining the nutritional value of
microalgae. In marine microalgae strains, its vitamin and mineral contents are also of importance.
ii) Specific physiological stages: during salmon production cycle animal’s undergo a process of
physiological changes (smoltification), which allow them to adapt from fresh water to salt water
environment. It is a critical stage for the industry; in some cases it is still associated to high mortality
rates. Among a vast array of metabolic changes during smoltification, animals present a rise on
thyroid hormones and increased salinity tolerance. As some microalgae are naturally, or could be
produced to be, rich in minerals, they could be of major interest to adequately modulate the salinity
tolerance process in fish.
Table 5. Selected examples of microalgae species used in aquaculture.
Market sector
Microalgae species
Active compounds
Process
AQUACULTURE
Bivalve Molluscs: Isochrysis sp.
Chaetoceros gracilis
Tetraselmis suecica
Pavlova lutheri
Skeletonema costatum
Penaid Shrimp: Tetraselmis chui
C. gracilis
S. costatum
Fish Feed Composition: Hypnea cervicornis
Cryptonemia crenulata
Marine fish larvae “Green Water”:
Chlorella sp.
Isochrysis galbana
Tetraselmis chui Adults:
Chlorella sp.
Spirulina sp.
Salmonids: Haematococcus
Aminoacids Lipids
(PUFA) Vitamins
Minerals
• Direct enhancement
in the immune
system
• Partial replacement
of animal sourced
proteins in adult
diets
• Pigmentation in
salmon’s muscles
ORNAMENTAL FISH Spirulina sp., Dunaliella sp. Chlorella
vulgaris
Pigments (phycocyanin,
beta-carotene and other
carotenoids, chlorophyll)
Carotenoids improve
and intensify the
coloration in fish
Schreckenbach et al. 2001; Becker 2004; da Silva and Barbosa 2008; Azaza et al. 2008.
use of microalgae for adult fish feed utilization became increasingly important not only because of colour
but also due to enhancing health effects.
Fish feeding represents over 50% of operating costs in intensive aquaculture, with protein being
the most expensive dietary source. Therefore, continuous efforts have been made over the past decades
to find alternative protein sources for aqua feeds, with special emphasis on terrestrial plants. There are
limitations to the use of plant protein sources in fish diets, attributed to their deficiency in certain essential
amino acids, their content of anti-nutritional compounds and to palatability problems. Additionally, recent
interest in several crops as biodiesel raw materials has increased the world’s demand for these crops and
consequently, their price. Besides, its production requires agricultural land and freshwater, which are
becoming very limited resources, and therefore, there is a need to search for alternatives (Pereira et al.
2012). Several improvements on fish health status by feeding with microalgal biomass are detailed in
Table 5.
Apart from their general use in the growth phases previously described, and irrespective of the fish,
shrimp, or mollusc species under farming, sensitive periods of the production cycle where microalgae as
functional ingredients could be highly valued are:
i) Early feeding stages: microalgae are successfully used for larval nutrition, either for direct
consumption, in the case of molluscs and penaeid shrimp, or indirectly, as food for the live prey
(rotifers, Artemia or copepods) fed to small fish larvae. They are also been used during rearing
larvae and juveniles stages of commercially important molluscs, penaeid prawn larvae, crustaceans,
and fish. Although nutritional requirements for some target species have been defined, no set of
nutritional criteria have yet been advanced. Generally, the microalgae must be non-toxic, in an
acceptable size for ingestion, the cell wall should be digestible, and with sufficient biochemical
constituents. Protein content and lipid quality are major factors determining the nutritional value of
microalgae. In marine microalgae strains, its vitamin and mineral contents are also of importance.
ii) Specific physiological stages: during salmon production cycle animal’s undergo a process of
physiological changes (smoltification), which allow them to adapt from fresh water to salt water
environment. It is a critical stage for the industry; in some cases it is still associated to high mortality
rates. Among a vast array of metabolic changes during smoltification, animals present a rise on
thyroid hormones and increased salinity tolerance. As some microalgae are naturally, or could be
produced to be, rich in minerals, they could be of major interest to adequately modulate the salinity
tolerance process in fish.
Table 5. Selected examples of microalgae species used in aquaculture.
Market sector
Microalgae species
Active compounds
Process
AQUACULTURE
Bivalve Molluscs: Isochrysis sp.
Chaetoceros gracilis
Tetraselmis suecica
Pavlova lutheri
Skeletonema costatum
Penaid Shrimp: Tetraselmis chui
C. gracilis
S. costatum
Fish Feed Composition: Hypnea cervicornis
Cryptonemia crenulata
Marine fish larvae “Green Water”:
Chlorella sp.
Isochrysis galbana
Tetraselmis chui Adults:
Chlorella sp.
Spirulina sp.
Salmonids: Haematococcus
Aminoacids Lipids
(PUFA) Vitamins
Minerals
• Direct enhancement
in the immune
system
• Partial replacement
of animal sourced
proteins in adult
diets
• Pigmentation in
salmon’s muscles
ORNAMENTAL FISH Spirulina sp., Dunaliella sp. Chlorella
vulgaris
Pigments (phycocyanin,
beta-carotene and other
carotenoids, chlorophyll)
Carotenoids improve
and intensify the
coloration in fish
Schreckenbach et al. 2001; Becker 2004; da Silva and Barbosa 2008; Azaza et al. 2008.