Shellfish Hatcheries Research Articles

Progress in Live Food Production and Use in Fish and Shellfish Hatcheries

Progress in Live Food Production and Use in Fish and Shellfish Hatcheries

Overwintering hatchery-reared individuals of the soft-shell clam, Mya arenaria L.: a field test of site, clam size, and intraspecific density

Soft-shell clams ( Mya arenaria L.) are a commercially important intertidal bivalve in Maine, USA where they are managed as a common property resource. Ten million 8–12 mm clam juveniles are reared annually at the Beals Island Regional Shellfish Hatchery and are transplanted onto publicly-owned mudflats during the fall or early winter. The success of this strategy is unpredictable because of sporadic occurrence of winter ice formation and subsequent scouring of the intertidal zone. These events, in addition to other severe winter storms, can result in complete mortality of the transplanted seed. Transplanting hatchery-reared seed in the spring, therefore, is preferable, but until now there has been no economically effective technique to hold millions of soft-shell clam seed over the winter. A field experiment designed to test the interactive effect of clam size and density on survival was conducted during the winter of 1991–1992 at a sheltered and exposed site near Beals, Maine, USA. Three sizes of hatchery-reared clam seed (Small, X ̄ = 4.3 mm shell length [SL]; Medium, 8.2 mm SL; Large, 11.5 mm SL) were used. Clam density was approximate and depended on clam size (Small, 18 750 ind, 37 500 ind, and 56 250 ind; Medium, 11 000 ind and 22 000 ind; Large, 4500 ind and 9000 ind). Clams of each size/density combination were added separately to nylon window screen, zippered bags (aperture = 1.8 mm). Bags containing clams were housed in wooden-framed subunits (0.45 m × 0.45 m × 0.08 m) covered with a 12 mm extruded mesh netting. Subunits were arranged vertically in groups of 4–6 and were submerged 1 m above the bottom in shallow water (3–8 m) from November 1991 to April 1992. Mean survival of medium and large size clams at both sites was 97.7%. Significant density effects were detected for both size groups at the sheltered site, although the difference between treatment levels was less than 2%. Mean survival of small clams pooled across sites was 67.8%. At the sheltered site, clams in the uppermost level of the overwintering units had consistently lower survival rates than those nearer the bottom. Density effects for small clams were detected only at the sheltered site where animals held at the highest density had significantly higher survival rates than animals at either of the two lower densities (75.3% vs. 60.3%). Clam loss over the winter may be reduced by suspending seed in seawater instead of transplanting it to intertidal flats.

A simple semi flow-through culture technique for the controlled super-intensive production of Artemia juveniles and adults

A simple semi flow-through Artemia culture unit is described for possible integration in marine fish and shellfish hatcheries as source of a cheap nursery diet. The system does not require the use of feeding pumps and involves minimal care. Food preparation and addition to the feeding tank is reduced to one or two manipulations per day during the meta-nauplius stages (day 1–3) and the juvenile stages (day 4–14), respectively. Biomass productions are superior to those reported for stagnant culture systems and are comparable to those demonstrated for flow-through culture units. This simple rearing technique offers the possibility of producing brine shrimp populations with a uniform size. Furthermore, by varying the feeding regime with the Artemia density at the start of the culture, specific Artemia prey sizes corresponding to the daily physical requirements in shrimp and fish hatcheries can be obtained.

The growth rate of two species of microalgae used in shellfish hatcheries cultured under two light regimes

. The production potential of any shellfish hatchery depends on the capacity of its algal system. The hypothesis that microalgal cultures grown under 12:12h light:dark photoperiod may produce the same cell densities as those using constant light is tested. Two species of marine microalgae used in shellfish hatcheries. Chaetoceros gracilis Schutt and Isochrysis galbana clone T-iso, were grown in cultures at 18°C, under continuous light (1.43 × 107μ-2day-1) and 12:12h light:dark cycles (2.87 × 107μE m-2 day-1). Both light regimes provided equal amounts of light per day. In the continuous light cultures the mean doublings per day for exponentially growing cells were 1.37 and 1.49 for C. gracilis and I. galbana respectively and for the 12:12h light:dark cycles were 1.47 and 1.56 respectively. After 14 days of growth, the numbers of cells per unit of volume showed no significant differences between the two light regimes. The results are discussed in terms of a review of other authors’ findings and in terms of the usefulness of the continuous light method in producing algae to be used in shellfish hatcheries.

Larval and juvenile rearing of black-lip pearl oyster, Pinctada margaritifera (Linnaeus)

The black-lip pearl oyster, Pinctada margaritifera (Linnaeus), has been cultured in the experimental shellfish hatchery at Tuticorin, India. The flagellates Isochrysis galbana and Pavlova lutheri were used independently as larval food at a concentration of 5 cells/μl up to day 5 and the ration was doubled thereafter until spat setting. The initial larval density was 1/ml. Straighthinge veliger stage (75×60 μm) was reached in 20 h, umbo stage (140×130 μm) on day 12, pediveliger (220×210 μm) on day 20 and plantigrade (260×240 μm) on day 23, and spat of 350×300 μm appeared on day 28. I. galbana promoted faster growth and early spat setting as compared to P. lutheri. The modal component of the larval population showed an average growth of 10.98 μm/day. A total of 6.3% of the initial larval population metamorphosed as spat. Juveniles cultured in the laboratory showed a growth rate of 0.09 mm/day. On transplantation to the culture raft in the farm, growth rate increased to 0.4 mm/day. The juveniles suffered heavy mortality after 4 months. It remains to be tested whether P. margaritifera juveniles would have a greater chance of survival in oceanic island conditions, as the natural distribution of the species in India is confined to the Andaman and Nicobar Islands.

Bacterial pathogens of oyster larvae (Crassostrea gigas) in a Tasmanian Hatchery

Diseases causing high mortality occurred in a hatchery for rearing juvenile oysters, C. gigas, at Bicheno, Tasmania, during 1980. Outbreaks of the disease characteristically showed three peaks: in 7-10-day- old larvae, in older larvae several days before setting, and in spat 1-2 weeks after setting. Various marine bacteria were cultivated from inactive larvae and other hatchery specimens, and the predominant strains were identified. When given to normal young larvae at doses of 1 × 105-5 × 105 or 1 × 10-5-5 × 107 bacteria (total dose), seven strains (five strains of Vibrio, two strains of Alteromonas) caused fatal infections in most animals. This is the first report of pathogenic marine bacteria in an Australian shellfish hatchery.

AN INDUSTRY REVIEW OF THE OPERATIONS AND ECONOMICS OF MOLLUSCAN SHELLFISH HATCHERIES IN WASHINGTON STATE

ABSTRACTMolluscan shellfish hatcheries have been in operation since 1969 in Washington State. The progress and overall performance of these facilities since that time are reviewed. Hatchery operations are discussed from the viewpoint of biological methods and financial success.Biologically, a comparison of hatchery seed is made with the imported Japanese seed and the domestically cultched seed in Washington State. The oyster seed market is analyzed in relation to quality of seed, number of oysters per shell, competition from natural seed sources, failure to standardize a case of seed and the inability to supply promised markets.Economically, the discussion is of the advantages and disadvantages of a hatchery operation with reference to facility size, operational economics and market demand.

Construction, operation and performance of a modified diatomaceous earth filter for shellfish hatcheries

A commercially available diatomaceous earth filter has been successfully modified for microfiltering sea water used to grow bivalve larvae. The filter consistently removes up to 96% of the suspended matter in the water down to at least 2.3 microns, and reduces the number of heterotrophic bacteria to between 1 and 5 × 10 2 ml −1. Growth and development of bivalve larvae in this water is excellent.

Ultraviolet light disinfection of shellfish hatchery sea water: I. Elimination of five pathogenic bacteria

Filtered sea water was seeded with one of five oyster-pathogenic bacteria to obtain a final concentration of 10 5 cells/ml. UV irradiation at a dose of 93 312–155 520 μW s −1 cm −2 rendered the contaminated sea water safe for rearing fertilized eggs of Crassostrea virginica. Fertilized oyster eggs were reared until the larvae began to set in filtered, UV-irradiated sea water and in filtered, non-UV-treated sea water. The data suggest that when a pathogenic bacterium is present the potential for disease is much greater in non-UV-treated sea water.

FROM A HATCHERY…LIGHTLY

ABSTRACTMuch attention has been given to recent advances in the art of bivalve molluscan mariculture arising from the contributions of private research groups, university programs, government agencies and commercial enterprises. The state‐of‐the‐art of bivalve culture is briefly explored here, areas of need are identified and these are then related to the capabilities and limitations of shellfish hatcheries. After differentiating the various types of hatcheries and describing their goals and capabilities, the author' company is used as a tool to illustrate and discuss the contributions which the industry can expect from commercial hatcheries and to identify those things which must be done by organizations other than hatcheries. In conclusion, the author perceives that real progress in the advancement of bivalve molluscan mariculture will occur only through the combined efforts of several groups and call for an enhanced coordination of effort.

BACTERIAL DISINFECTION IN SHELLFISH HATCHERY DISEASE CONTROL

AbstractControl of disease in shellfish culture is a complex and pervasive problem which can cause extensive loss of time, money, and efficiency. Many shellfish diseases are caused by pathogenic bacteria introduced into the hatchery system through a contaminated water source, an infected animal from natural waters, or a tainted food supply. It is the intent of this paper to explore 4 methods of bacterial disinfection in shellfish hatcheries: ultraviolet light treatment of bacterial shellfish pathogens, the addition of silver (AgNO3) to shellfish larval culture waters, ozone disinfection of contaminated culture water, and standard antibiotic treatment (neomycin) in shellfish hatchery disease control. The efficacy of each system is examined and recommendations are made for the incorporation of standard disease prevention methods in shellfish hatchery operations.

Vibrio anguillarum and larval mortality in a California coastal shellfish hatchery.

Vibrio anguillarum was isolated as a pathogen in the commercial culture of oyster spat at Pigeon Point, Calif. A water-soluble, heat-stable exotoxin extracted from cultures of the vibrio inhibited larval swimming and contributed to larval mortality. Although the vibrio was insensitive to penicillin in standard plate testing, this antibiotic proved useful in preventing mass larval mortalities in the hatchery.

Shellfish Hatcheries—Present and Future

Abstract The history of the development of shellfish hatcheries is summarized. Studies of the salinity, temperature, pH tolerances, and food requirements of clam and oyster larvae, as determined at the Milford laboratory, are cited to show the factors that govern the location and operation of successful shellfish hatcheries. Examples of how these requirements are met in presently operating commercial hatcheries are given. Some possible directions for future shellfish culture are suggested, using hatchery techniques for developing and utilizing new genetic strains of shellfish, and using newly-developed predator control methods and improved shellfish farming practices.