1.1.2 Considerations

1.1.2.1 Government regulations

The first consideration is to determine if government regulations permit construction of a bivalve hatchery at the desired site.

This can be done quickly by making enquiries of local, state, provincial or federal authorities. If regulations do not permit construction of a hatchery at the desired site one must decide if it is preferable to find another location where construction is permitted, or attempt to change existing government regulations to allow construction at the desired site.
It is likely that a number of permits and licences will be required to ensure compliance with local building codes and national and local environmental regulations before any construction is allowed. This can be a lengthy, costly and time consuming process and may require an assessment of the potential impact of the hatchery on the local environment before permission is either granted or not granted to begin the construction phase.

 

1.1.2.2 Seawater quality

Before committing to what is considered to be a suitable location for a hatchery it is of paramount importance to ensure that good quality seawater exists year-round at the prospective site. This point cannot be overemphasized. If a good seawater source is not available, it will be difficult, if not impossible, to develop an efficient and profitable hatchery operation. For this reason every effort should be made to obtain as much information as possible about the quality of the seawater throughout the year at a potential site - or sites. Information is required not only for surface waters but also for the entire water column, since thermoclines may develop or upwelling may occur periodically. If previous oceanographic surveys have been undertaken in the area, copies of the data should be examined. If such surveys have not been undertaken, one should be prepared to undertake a detailed sampling of the waters at the proposed site for at least a year.
Environmental parameters of seawater that need to be examined will depend in part on geographic location and the intended species for culture. Bivalve larvae as well as juveniles and adults have strict physiological requirements, such as water temperature, salinity and oxygen levels and these must be maintained in a hatchery operation. Water temperatures are higher in the tropics than in temperate regions and indigenous bivalves are well adapted to tolerate these conditions. But in a hatchery situation temperatures must not be allowed to drop too low or larval and juvenile survival and growth will be adversely affected. In temperate areas water temperatures must not be allowed to exceed upper or lower lethal levels to larvae and juveniles. Salinity can vary widely and tolerance to these fluctuations differs among bivalve species. Some require high oceanic levels of salinity while euryhaline (estuarine and brackish water) species exhibit much wider tolerance. Periods of heavy rainfall may not only cause periods of low salinity, but heavy associated runoff can increase quantities of silt and other materials which may lead to problems in a hatchery. Dense concentrations (blooms) of some marine algal and bacteria species may release toxic substances that may cause reductions in both the survival and growth of bivalve larvae or juveniles, or mass mortalities in extreme cases. As much data as possible on these parameters should be collected prior to deciding on the adequacy of a site for a bivalve hatchery. Remedial measures to improve inadequate quality seawater can be extremely costly and may adversely effect the profitability of a venture.
Locations possibly influenced by effluents discharged from industrial plants should be avoided. The lethal and sublethal effects of many industrial pollutants are not completely understood, nor are the additive effects they may exert when several industries are discharging a range of potentially toxic wastes in nearby waters. Effects of such effluents can be extremely damaging to bivalve larvae. For example, an anti-fouling ingredient added to marine paints, tributyltin (TBT), has been found to be highly lethal to bivalve larvae even at concentrations of a few parts per billion. Drawing a seawater supply from the vicinity of marinas and commercial docks needs to be avoided. If feasible it is advisable to undertake bioassay studies using bivalve embryos to help determine the quality of the water at the potential hatchery site. The presence of deleterious materials may be transitory or seasonal in nature, so sampling for bioassays should be carried out over a period of at least a year and be done preferably on a weekly basis.
Agricultural – forestry included – and domestic sources of pollution should also be avoided. It has recently been shown that runoff from some cultivated lands can carry concentrations of pesticides at levels deleterious to the growth and survival of bivalve larvae. Domestic pollution may not only contain pollutants that are toxic to bivalve larvae but the high organic content can cause depletion of oxygen levels and increased levels of bacteria that could also lead to reduced growth and mortalities of larvae.
Another consideration when deciding upon the location of a bivalve hatchery is whether “civilization” will soon encroach on the site. Urbanization with its ancillary problems is one of the main concerns in bivalve culture. If the site will soon be encompassed by urbanization then every effort must be made to ensure that sources of potential pollution will be kept to a minimum. This will require working closely with planners and developers.

1.1.2.3 Siting the hatchery

The hatchery should be located close to the ocean so that the distance required to pump water is kept to a minimum. This negates the necessity of having to maintain great lengths of pipe. It should also be located as close to sea level as possible to avoid problems of pumping water any great vertical distance. If fluctuations in surface seawater temperature and salinity occur regularly, the intakes for the pipes will need to be located at depth (up to 20 m below the surface) to maintain more constant water temperature and salinity. Depending on the nature of the geological strata, it may be possible to drill wells close to the shore to access seawater aquifers. A water source of this nature will be at a more constant temperature year-round and will already be pre-filtered by percolation through the strata. It may, however, require oxygenating before use. It is always wise to consult with a suitably qualified engineer when making decisions on the best methodology and technology to procure the water supply.
Sufficient area needs to be available at the site to accommodate the hatchery and ancillary buildings and also to allow for any future expansion. The need for adequate surveillance should also be considered.
Other considerations that need to be kept in mind for a site include an adequate supply of electrical power, a source of freshwater and a skilled labour force to operate the hatchery. Good communications should exist so that required materials and supplies can be acquired quickly and larvae and seed can be quickly shipped to their various destinations. The proximity of institutions such as universities, government laboratories and libraries should also be considered since such resources can be of great assistance in operations and in helping towards solutions to problems that may arise.
It is a worthwhile preliminary to prepare a check list of parameters that must be met, or at least reviewed, when considering a site for a bivalve hatchery and work through the list to ensure the site meets as many of the requirements as possible.