Ecosystem Concepts for Sustainable Bivalve Mariculture (2010) / Chapter Skim
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These policy tools are commonly utilized to reduce effects associated with the use of natural resources in commercial activi ties like mariculture. Although mariculture operations may expand the production of seafood without additional exploitation of wild popula tions, they still depend upon and affect natural ecosystems and ecosystem services.
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From page 2... ...
Mariculture gear increases the availability of hard substrates, thereby supporting higher densities of fish and invertebrates that associate with structured habitat, but the presence of artificial hard substrates can also promote colonization and spread of introduced species, such as nonnative tunicates. Such a mix of beneficial and negative effects illustrates the complexity of ecosystem responses to mariculture operations.
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By contrast, adoption of performance standards is likely to encourage innovation among growers. With performance standards, mariculture operations are managed adaptively to maintain key indicators within acceptable bounds, through direct monitoring of ecosystem indicators rather than tracking compliance with specific management practices.
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should be developed and implemented at the ecosystem level because they can be applied to bivalve mariculture more generally with adjustments for the spe cific conditions of each mariculture operation, species, and culture technique. Recommendation: Management of bivalve mariculture should employ performance standards to address carrying capacity concerns at the scale of the water basin but may find the use of BMPs to be more practical and efficient at the local scale, especially where the industry consists of large numbers of small growers.
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Information on the potential effects of mariculture on birds, marine mammals, and marine turtles is largely based upon a general understanding of wildlife ecology and the relation ships of these species to the physical and biological environment rather than on studies to test explicitly the effects of mariculture operations. Potential positive impacts include increased food availability for birds attracted to the fouling organisms on mariculture gear.
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and sediments via biodeposits benthic biota limiting bivalve biomass from bivalve mariculture to levels below carrying capacity for biodeposits Integrate bivalve mariculture with seaweed culture Decreased planktonic Shift planktonic Site selection (highly biomass by overstocking composition; reduce productive area) turbidity allowing greater light penetration Manage stocking density and hence more benthic based on carrying capacity plant production; for filtration deprive native suspension feeders of food Loss of carbonate shell Less habitat for larval Recycle shell from shucking from coastal waters settlement and oyster operations and restaurants, reef biota; reduced taking precautions to buffering capacity for prevent spread of nonnative maintaining pH species Introduction and Large losses of cultured Largely limit transfer to eyed transmission of disease bivalves; transmission larvae screened for disease; organisms of disease to native minimize transfer of adults species with possible and only after screening biodiversity losses and reduction in wild stocks of bivalves Establishment of Loss of native Culture sterile triploids breeding populations biodiversity resulting of nonnative bivalves from competition, Regulate transport and introduced through predation, and habitat processing of live animals culture modification Spread of nonnative Loss of biodiversity Limit stocking to clean seed species associated with resulting from or eyed larvae (no adults)
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From page 7... ...
SUMMARY Performance Standard Approach Desired Outcome Monitoring for hypoxia in sediments Limit organic accumulation in sediments, yet fertilize submerged aquatic vegetation (SAV) Carrying capacity model for estimating Maintain or restore biodiversity and stocking density natural food web structure; enhance water clarity via filtration and improve SAV Monitor for change in plankton habitat composition and performance of native suspension feeders Maintain baseline shell-based habitat and carbonate balance of estuaries and coastal lagoons; compensate for shell removed by harvesting wild bivalve stocks Monitor for disease organisms Avoid spread of disease; maintain health of cultured and native bivalves Monitor for nonnatives in areas near Protect native species and ecosystem mariculture operations structure Monitor for nonnatives at mariculture Protect native species and ecosystem operations and in areas near operations structure continued
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Disease organisms can still be transferred with bivalve seed used in mariculture, but International Council for the Exploration of the Sea protocols for the transport of eyed larvae from hatcheries with rigorous disease inspection programs and producing seed in quarantine greatly reduce the potential for disease transmission. Diseases that occur at low levels within wild populations can flourish in mariculture populations because of altered conditions, such as crowding and temperature fluctua tions.
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From page 9... ...
Additionally, mariculture structures, such as racks, lines, bags, and the cultured shellfish should be studied to determine whether they act only as attractants or also enhance pro ductivity of species known to aggregate around structures. Finding: Continued research efforts could develop appropriate cul turing techniques for native bivalve species, as well as enhance ways of restoring and then sustainably managing depleted native stocks.
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From page 10... ...
The similarity is greatest when comparing wild harvest to mariculture operations that raise bivalves in or on natural bottom habitats because similar or identical harvesting methods are typically used. Impacts of dredge-harvest gear on the benthic communities are greater than for any other bottom-disturbing fishing gear, and the intensity and duration of such impacts of harvest disturbance vary with bottom type.
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Finding: Economic theory suggests that mariculture production will tend to increase supply and reduce the price of the cultured species, thereby reducing economic incentives to harvest wild populations. The effect of lower prices on fishing pressure depends on the condi tion and management of the wild fishery.
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From page 12... ...
If cultured bivalves were used to help restore baseline conditions of filtration, there could be substantial improvements in the ecosystem state through enhanced water clarity and reductions in algal blooms and hypoxia. Carrying capacity models can be used to optimize production of the cultured bivalves; reduce the ecological impacts on the food web; or maintain societal values, such as scenic amenity or recreational opportunity.
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From page 13... ...
In most states, the intertidal or shallow subtidal bottom and overlying waters in which mariculture operations are located are owned by the public with the state acting as trustee. A federal permit may be required if mariculture gear could represent an obstruction to navigation or if the operation is located in federal waters.
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From page 14... ...
Bivalve growers can increase societal accep tance and reduce political opposition to mariculture leases by engaging constructively with the local community and by designing their operations to minimize visual impacts. Mariculture operations that restrict foot or boat traffic in nearshore waters or tidal areas face issues of public use and access rights.
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From page 15... ...
Recommendation: Research at the interface of biology and natural resource economics should be aggressively supported to explore the various proposed ecosystem services of bivalve molluscs and to develop rigorous economic methods of putting values on those services. This could include methods that specify market values for those services that yield to this approach and methods involving "willingness to pay" and other public preference approaches where markets do not exist.
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From page 16... ...
regulating bivalve stocking to require use of eyed larvae from certified hatcheries with an effective and comprehensive disease inspection or to first-generation seed spawned from adult bivalves under quarantine conditions in order to minimize species introductions and disease spread; (5) insuring that bivalve shell fish loading does not exceed levels that have unacceptable negative impacts on the benthos through excessive organic loading or on other components of the ecosystem through clearance of planktonic foods and organic particles from the water column; (6)
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