- Use of Spray-dried Schizochytrium
sp. as a
- Partial Algal Replacement for Juvenile Bivalves.
- Phil Boeing
- Pacific Seafarms International S.A. de C.V., Cerro Escondido #122,
Mazatlan, Sinaloa, Mexico.
- Two commercially important species of juvenile bivalves (Tapes semidecussata and
Crassostrea gigas) were fed a spray-dried preparation of heterotrophically grown
algae, Schizochytrium sp. in 20 L recirculating downwell systems. All systems were
fed a weekly ration equal to 50% of their live weight as dry weight calculation for live
algae or percentage Schizochytrium sp. substitute. Weekly growth rates of juveniles
as live wet weight increase were measured to determine the effects of the different diets.
Two experiments were performed in duplicate, the first using Tetraselmis suecica, a
live algae control of moderate nutritional value, and the second using an equal mixture of
Chaetocerous sp. and Tetraselmis suecica, a live algae control of high
nutritional value. In the first experiment, 40% and 80% substitution for live algae Tetraselmis
suecica were compared to controls fed 100% live Tetraselmis suecica.
Significantly higher growth over the control was obtained with 40% substitution in Crassostrea
gigas and 40% and 80% substitution in Tapes semidecussata. For the second
experiment, 40% and 80% substitution for equal portions of live algae Chaetocerous sp.
and T. suecica mixture were compared to controls fed 100% live algae mixture.
Significantly lower growth rates were found for Crassostrea gigas at both 40% and
80% substitution. However no significant growth difference was found for Tapes
semidecussata at 40% substitution, in contrast to a significantly lower growth over
the control at 80% substitution. These results suggest that the routine use of
Schizochytrium sp. as a partial replacement of live algae in bivalve culture to be
economically viable, depending upon the unit production cost of the live algae for any
given nursery facility.
Nursery culture of bivalve molluscs is a useful step for improving required growout
time and survival in temperate climates (Anderson and Chew 1982; Bayes 1991). Algal
systems for feeding bivalve nurseries represent a major production cost factor for
shellfish enterprises (Coutteau and Sorgeloos 1992; Laing and Millican 1992; Meyers and
Boisvert 1990; Walsh 1987).
Artificial and replacement diets for bivalve molluscs have been developed and
extensively evaluated (Albentosa et al. 1989; Boeing 1986; 1992; Jones et al. 1974; 1993;
Langdon et al. 1985; Langdon and Siegfried 1984; Langdon and Waldock 1981; Urban and
Langdon 1984). Apparently none of these diets has shown sufficient cost-effectiveness to
be commercially practical. The possibility of using heterotrophically grown spray-dried
algae as a partial or total replacement for live algae has also seen considerable
research, although with only a few algae species (Curtolo et al. 1993; Helm and Hancock
1990; Hidu and Ukeles 1962; Laing et al. 1990; Laing and Millican 1991; 1992; Laing and
Verdugo 1991). Despite reported early successes with heterotrophically grown spray-dried
algae species such as Tetraselmis suecica and Cyclotella cryptica, several
investigators have pointed out the need for more nutritionally valuable species to be made
available for the bivalve industry (Laing and Verdugo 1991; Jones et al. 1993). A recently
commercialized heterotrophically grown spray-dried marine algae, Schizochytrium sp.
(ALGAMAC-2000, Aquafauna Bio-Marine, Los Angeles, CA.) has shown very good acceptability
and performance against controls when used at up to 70% algal replacement for penaeid
shrimp (Boeing 1996; Rosenberry 1996). This product has nutritional qualities which would
seem to make it an excellent candidate for algal substitution in other aquatic species
such as bivalves and fish.
The present paper describes some preliminary results of substituting Schizochytrium
sp. for live algae Tetraselmis suecica and Chaetoceros sp. in the nursery
culture of juvenile Crassostrea gigas and Tapes semidecussata.
Top of Page
- MATERIALS AND METHODS
- Lots of 2-4 mm Tapes semidecussata and 4-6 mm Crassostrea gigas from the
same cohort were used in the experiments. Two independent trials for both species were set
up and carried out in duplicate. For both experiments animals were dried on absorbent
paper and lots of 1.5 g and 2.5 g were weighed out for Tapes semidecussata and Crassostrea
gigas respectively for the first experiment and 2.5 g of each for the second
experiment. Weighing was carried out on an electrobalance to an accuracy of 0.1 mg. Daily
growth rate (DGR) of the bivalves was calculated as a function of increase in wet live
weight per seven day sampling period from the equation:
DGR = (ln final weight- ln initial weight) / 7
Culture containers and methodology were identical for both experiments with the
exception of the live diet species. The juvenile bivalves were grown in 20 L recirculating
downwelling systems, juveniles were kept in 30 cm diameter circular plastic 750 µ m mesh screen containers suspended in 20 L buckets with
exterior air lift circulators fitted. Flow rate to each container was maintained at 4
L/min. The temperature and salinity were maintained at 25 C and 34 parts per
thousand (ppt) respectively. The seawater in the containers was completely changed daily
with seawater filtered to 5 mm and maintained at 25 C.
Live algae Tetraselmis suecica and Chaetoceros sp. were grown in
semi-continuous cultures, in Guillard´s enriched f/2 medium with sterilized seawater
filtered to 1 mm. Cultures were harvested every day in the
exponential phase of growth in volumes dependent on the division rates of the algae.
Tests were run using a feed ration calculated at the
beginning of each week from the
live wet weight biomass of each container as a 50% dry weight of food to wet weight
biomass of bivalves per week. The daily ration was one seventh of this value fed in two
doses, one in the morning and one eight hours later. For the live algal diets the volume
of culture fed was taken from the cell density of the algae culture calculated from
hemacytometer counts. The dry weights of the algae were calculated by filtering a
measured volume of algal culture of known cell density through Whatman GF/C 57 mm glass
fibre filter discs, washing with 4% ammonium formate solution, then drying to a constant
weight at 65 C. The dry cell weights were found to be 200 pg/cell for
Tetraselmis suecica and 120 pg/cell for Chaetoceros sp. In
the first experiment the live algae component used was Tetraselmis suecica, in the
second experiment the live algae component used was an equal mixture by dry cells weights
of Tetraselmis suecica and Chaetoceros sp. The required amount of the
spray-dried algae for the substitution of the live diets was first weighed then mixed with
filtered seawater for 30 sec. in a domestic blender.
Top of Page
- The results of the first experiment show that Schizochytrium
sp. is capable of
sustaining significantly better growth than controls in juvenile T. semidecussata
at up to 80% algae substitution when Tetraselmis suecica was the only live
algae feed (Table 1). Significantly higher growth over T. suecica fed controls was also
obtained with C. gigas juveniles at the 40% substitution (Table 2). Although T.
suecica has been noted as a moderate to good food for juvenile bivalves (Laing and
Verdugo 1991), our experiments show this species, cultured under our conditions, to be of
poor nutritional quality as indicated by the slow growth of the control animals (Fig. 1).
Other investigators have found T. suecica to have a low food value in bivalve
feeding experiments possibly due to the presence of a rigid cell wall which may
complicate digestion (Cordero and Voltolino 1994).
|95 % Tukey analysis for T. semidecussata first experiment
|3 80% replacement
|2 40% replacement
Top of Page
- The growth rates of both T. semidecussata and C. gigas in the second
experiment at 40% and 80% Schizochytrium sp. replacement were significantly greater
than control growth rates in the first experiment. This would seem to indicate a
magnification of the utility of spray-dried diet replacement in the presence of low to
poor live algae sources. Due to the high cost of production, it is unlikely that most
commercial facilities would be able to provide the amounts of high quality select live
algae species used in the second experiment. The costs for culturing live algae for aquatic
animals have been reported by investigators to vary between US$20.00/kg dry weight and
US$594.00/kg dry weight, depending on the location and size of the culture facility
(Donaldson 1981, Laing and Millican 1992). The greater number of published cost estimates
for live algae production at bivalve facilities are around US$200.0/kg dry weight (Walsh
1987, Walne 1976, Coutteau and Sorgeloos 1992). If these live algae production costs are
only marginally accurate for todays bivalve nursery facilities, then there are
realistic economic savings to be realized with Schizochytrium sp. replacement for
live algae. For small bivalve hatcheries or larvae setting facilities using algae paste or
naturally available algae, the economics may prove greater yet. These cost reductions may
be further amplified when consideration is given to capitalizing hatchery live algae
production systems for new start up or existing facility expansion.
These experiments are preliminary and limited to only two species of commercial
bivalves. In spite of the efforts to obtain homogenous mixing of the Schizochytrium sp.
in the containers, some settling was observed which may have affected the results.
Undoubtedly, the improved mixing from well engineered upwelling systems characteristic of
many commercial bivalve nursery facilities will alleviate this problem.
- The authors wish to thank the following people who made this work possible: Dr. Carlos
Martinez Palacios for support and use of the C.I.A.D. facilities, Mazatlan, Mexico; Dr.
Dominico Voltolina, I.C.M.L, Mazatlan, Mexico, who so kindly provided all the algae used
in the study; Mr. Ted Kuiper of Kuiper Mariculture, Eureka, CA., who supplied the
bivalves; and Aquafauna Bio-Marine, Hawthorne, CA., who provided the AlgaMac-2000.
Top of Page
- LITERATURE CITED
Albentosa, M.E., E. Naessens, P. Leger, P. Coutteau, P. Lavens, and P.
Sorgeloos. 1989. Promising results in the seed culturing of the manila clam Tapes
semidecussata with a manipulated yeast product as a partial substitute for algae. p.
7-8. In: Aquaculture Europe 89, Bordeaux, France, Oct. 2-4, 1989. Short
Communications and abstracts. Bilard, R. and N. De Pauw (Comp.). European Aquaculture
Society Special Publication 10, Bredene, Belgium.
Anderson, G. J. M.B. Miller, and K.K. Chew. 1982. A guide to manila clam
aquaculture in Puget Sound. Washington Sea Grant Publication No. WSG-82-4. 45 p.
Bayes, J.C. 1981. Forced upwelling nurseries for oysters and clams using
impounded water systems. In: C. Claus, N. De Pauw and E. Jaspers (Eds.), Nursery Culturing
of Bivalve Molluscs. Special Publication European Mariculture Society, Bredene,
Belgium, 7: 73-83.
Boeing, P.L. 1986. Nursery culture of bivalve molluscs, with a report on
preliminary supplementary feeding trail with microcapsules. Paper presented at the 1st
Ineramerican Congress of Aquaculture, Salvadore, Bahia, Brazil, Sept. 4-8, 1986.
Boeing, P.L. 1992. Polyculture of hard clam (Tapes semidecussata)
with white shrimp (Penaeus vannamei) in shrimp ponds. Project E3-D Regional Program
of Technical Co-operation in Fisheries. CEE-PEC-ALA/87/21. Guayaquil, Ecuador.
Cordero, B., and D. Voltolina. 1994. Growth of Mytilus
galloprovencialis fed with four microalgae and two feeding regimes. Journal of the
World Aquaculture Society 25: 471-476.
Coutteau, P., and P. Sorgeloos. 1992. The use of algal substitutes and
the requirement for live algae in the hatchery and nursery rearing of bivalve molluscs: an
international survey. Journal of Shellfish Research 11: 467-476.
Curatolo, A., M.J. Ryan, and J.P. Mercer. 1993. An evaluation of the
performance of manila clam spat (Tapes philippinarum) fed on different rations of
spray-dried algae (Tetraselmis suecica). Aquaculture 112: 179-186.
Helm, M.M. and S. Hancock. 1990. Growth of small bivalve spat on
heterotrophically grown spray-dried algae. In: World Aquaculture 90. June 10-14,
1990. Halifax, NS Canada, Book of Abstracts IMPRICO, Quebec, Canada, pp 65.
Hidu, H., and R. Ukeles. 1962. Dried unicellular algae as food for
larvae of the hard-shell clam, Mercenaria mercenaria. Proceedings of the National
Shellfisheries Association 53: 85-101.
Jones, D.A., J.P. Mumford, and P.G. Gabbot. 1974. Microcapsules as
artificial food particles for aquatic feeders. Nature 247: 233-239.
Jones, D. A., M.S. Kamarundin and L. Le Vay. 1993. The potential for
replacement of live feeds in larval culture. Journal of the World Aquaculture Society 24:
Laing, I., A.R. Child and A. Janke. 1990. Nutritional value of dried
algal diets for larvae of manila clam (Tapes philippinarum). Journal of the Marine
Biological Association of the United Kingdom 70: 1-12.
Laing, I. and P.F. Millican. 1991. Dried-algae diets and indor nursery
cultivation of Manila clam juveniles. Aquaculture 95: 75-87.
Laing, I. and P.F. Millican 1992. Indoor nursery cultivation of juvenile
bivalve molluscs using diets of dried algae. Aquaculture 102: 231-243.
Laing, I., and C.G. Verdugo. 1991. Nutritional value of spray-dried Tetraselmis
suecica for juvenile bivalves. Aquaculture 92: 207-218.
Langdon, C.J., D.M. Levine and D.A. Jones. 1985. Microparticulate feeds
for marine suspension feeders. Journal of Microencapsulation 2(1): 1-11.
Langdon, C.J. and C.A. Siegfried. 1984 Progress in the development of
artificial diets for bivalve feeders. Aquaculture 39: 135-153.
Langdon, C.J. and M.J.Waldock. 1981. The effect of algal and artificial
diets on the growth and fatty acid composition of Crassostrea gigas spat. Journal
of the Marine Biological Association of the United Kingdom 61: 431-448.
Meyers, J.A. and R.N. Boisvert. 1990. The economics of producing algae
and bivalve seed in hatcheries. Aquaculture 86: 163-179.
Rosenberry, R. 1996. ALGAMAC-2000. Shrimp News International 21(1): 4.
Urban, E.R. and C.J. Langdon. 1974. Reduction in costs of diets for the
American oyster, Crassostrea virginica (Gmelin), by the use of non-algal
supplements. Aquaculture 38: 277-294.
Walsh, D.T., C.A. Withstandley, R.A. Kraus, and E.J.
Mass culture of selected marine microalgae for the nursery production of bivalve seed.
Journal of Shellfish Research Vol. 6: 71-77.
Top of Page