Ecosystem Concepts for Sustainable Bivalve Mariculture (2010) / Chapter Skim
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5 Carrying Capacity and Bivalve Mariculture
5 Carrying Capacity and Bivalve Mariculture
Pages 87-106
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From page 87... ...
The expansion of bivalve mariculture and the increase in environmental awareness have encouraged a more ecosystem-based perspective for managing and developing bivalve culture. For example, polyculture or integrated aquaculture is a growing trend that considers the ecosystem as a whole and allows for the culture in one location of multiple species that are presumably synergistically related (Box 5.1)
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From page 88... ...
sac charina with mussels or with scallops (Food and Agriculture Organization of the perspective has led to the development of prognostic site-assessment tools and practical ecosystem-performance indicators. The need to understand and predict the response of interlinked ecosystem processes and to determine the consequences of these for management and commercial decisions has resulted in the emergence of ecosystem modeling as an important tool for bivalve mariculture management.
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From page 89... ...
3. Ecological carrying capacity -- the stocking or farm density above which "unacceptable ecological impacts" begin to manifest.
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From page 90... ...
The development of ecological carrying capacity indicators and models is relatively new but has the potential to feed into EBM systems, which in turn would support the ideals and goals of the ecosystem-based approach to mariculture management. The ability to predict ecological carrying capacity is crucial to assessing the impact of development and expansion of large-scale bivalve mariculture operations and also helps in the identification of appropriate indicators and metrics that allow performance standards to be determined.
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From page 91... ...
Modeling ecological carrying capacity with feedback from stakeholders in the system holds promise, but due to its newness, it is also the least understood and practiced. Ultimately, it will be important to quantify the values presented by stakeholders in a science-based effort in order to determine the proper limits to bivalve mariculture in local waters.
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From page 92... ...
Recent models consider potential impacts of phytoplankton removal by a filtering bivalve or community of bivalves, and some attempt to include effects on related species such as seaweeds, which are relevant to system energy flow and ecological stability in the marine food web. The modeling frameworks and supporting data have evolved during the past 10–15 years to the point of providing guidance for the development of mollusc farms, their management, and potential economic effects of bivalve mariculture (Table 5.1)
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From page 93... ...
and far-field effects (e.g., nutrient cycling, pelagic carry ing capacity) , and as a result, estimates of this quantity require modeling frameworks that include a range of space and time scales that are rel evant to the processes affecting ecological carrying capacity.
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From page 94... ...
(2007) Ecological and production Mussels and lower trophic levels Byron et al.
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From page 95... ...
CARRYING CAPACITY AND BIVALVE MARICULTURE Management Model Framework Simulation Application Application Coupled circulation, primary Estimation of production carrying None production, and oyster growth capacity and optimum-seeding model strategy Conceptual Theoretical evaluation of None minimum carrying capacity requirements Population dynamics model Assessment of oyster standing None stock production Inverse analysis of carbon flow in Assessment of local food None lower trophic levels availability for oyster farming Coupled two-dimensional Estimation of environmental Potential circulation–biogeochemical model carrying capacity for polyculture system Population model for oysters and Assessment of standing stock None mussels and production changes and environmental effects Individual-based species models Assessment of seeding and Potential and multi-cohort population harvesting strategies of models polyculture management strategies EcoPath: linear food web Estimation and comparison None of ecological and production carrying capacity for bivalve culture Nitrogen budget, lower trophic Assessment of mussel production None level, and mussel growth on nitrogen budgets and dynamics Circulation, biogeochemical, Assessment of farm location and Potential bivalve growth, production, and practice on production outputs eutrophication and nutrient management Coupled biological–circulation– Assessment of effects of food None chemical model depletion EcoPath Defined production and social None carrying capacity continued
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From page 96... ...
Furthermore, simply including hydrodynamic models with a proven track record in providing modeling frameworks for mariculture systems is not sufficient; the results from these models must be provided at space and time scales that are appropriate for the ecosystem context and for the mariculture system. The availability of a hydrodynamic model allows estimates of oxygen and nutrient regeneration and flushing times of stratified systems, as applicable to most estuaries, which have a bearing on the capacity of the system to produce bivalves and the degree of interaction between cultured bivalves and other filter-feeding organisms in the system.
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From page 97... ...
. These factors have implications for ecological carrying capacity.
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From page 98... ...
phytoplankton production is driven primarily by externally derived nutrients, whereas in dry summer periods, phytoplankton production is driven by nutrients derived from mollusc excretion and sediments. The modeling frameworks that provide ecological and production carrying-capacity estimates include ecosystem components that are represented in models that range from simple box models to fully spatialexplicit (three-dimensional)
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From page 99... ...
(2006b) developed a framework for how social carrying-capacity studies can be used to calibrate ecological carrying capacities and frame a societal debate about what are "acceptable" impacts (Figure 5.1)
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From page 100... ...
MARINE SPATIAL PLANNING: LOCATING NEW OR EXPANDING PRESENT MARICuLTuRE OPERATIONS Bivalve mariculture has been an important activity in the United States for more than 100 years; thus, many existing farms were sited well before the current social and ecological carrying-capacity concerns discussed in this report were considered. Today, the combination of greater concern over ecological effects, more intense use conflicts with growing coastal populations, and greater demand for mollusc leases driven by growing markets for seafood is forcing resource managers to evaluate existing mariculture operations and subject applications for new or expanded
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From page 101... ...
, E coli sources, intense stormwater runoff, or where harmful algal blooms are likely to occur, although these considerations have not always been taken into account when locating bivalve mariculture sites.
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From page 102... ...
. Progress has been made in mapping bivalve mariculture structures as habitat in some west-coast areas using GIS, but effects of habitat changes due to mariculture and functional value of these habitats has yet to be assessed fully (Ward et al., 2003; Carswell et al., 2006; Dumbauld et al., 2009)
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From page 103... ...
In addition to enhancing native bivalve populations that are declining (Beck et al., 2009) , bivalve restoration and presumably bivalve mariculture can serve to enhance habitat for other species and provide valuable ecosystem services, including production of other fish and invertebrates (Coen et al., 1999; 2007; Peterson et al., 2003; Grabowski and Peterson, 2007)
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From page 104... ...
The current generation of models is moving toward the development of frameworks that can provide estimates of production and ecological carrying capacity. These models include details of multiple factors that influence the structure and function of the marine ecosystems and the interactions of these systems with bivalve mariculture.
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From page 105... ...
While current modeling efforts try to incorporate the above points into estimates of ecological carrying capacity, the development of models for estimation of carrying capacity needs to progress in parallel with a coordinated and sustained empirical measurement effort that will provide the information needed to validate the projections from the models and subsequently modify the models in response. FINDINGS AND RECOMMENDATIONS Finding: Some attempts have been made to include an evaluation of uncertainty in the parameters used in model-based estimates of bivalve production and ecological carrying capacity.
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From page 106... ...
Our understanding of factors that affect ecological carrying capacity will evolve as scientists learn more about the functioning of marine ecosystems. Recommendation: Managers should utilize models based on empiri cal data that can estimate carrying capacity relative to bivalve pro duction, ecosystem, and social constraints.
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