Shellfish Aquaculture and the Environment (Shumway/Shellfish Aquaculture and the Environment) || Balancing Economic Development and Conservation of Living Marine Resources and Habitats: The Role of Resource Managers
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Balancing e conomic d evelopment and c onservation of l iving m arine r esources and h abitats: the r ole of r esource m anagers Tessa L. Getchis and Cori M. Rose
Bivalve shellfi sh production represents a large and growing segment of the U.S. and global seafood industry, with nearly 20% of domestic and 27% of worldwide aquaculture produc-tion being attributed to shellfi sh aquaculture (U.S. Department of Agriculture National Agricultural Statistics Service 2006 ; Food and Agricultural Organization of the United Nations 2008 ). Although production is increas-ing, there is uncertainty and public concern with respect to the ecological effects of aqua-culture practices, which threatens to constrain further development of the industry (Food and Agricultural Organization of the United Nations 2008 ; National Research Council
2010 ). This ambiguity has led to both local and sweeping national changes to the manner in which shellfi sh aquaculture is regulated and the husbandry standards by which shellfi sh producers must adhere to, in the United States and elsewhere.
Evaluation of the effect of bivalve shellfi sh aquaculture on the marine and estuarine near - shore environment has, until recently, predom-inantly focused on near - fi eld assessment of the effects of highly intensive operations outside of the United States (Cranford et al. 2003 ). It has been assumed that because, unlike fi nfi sh aquaculture, shellfi sh cultivation occurs in open water without the addition of feed, the likelihood for adverse effects was low. This incomplete rendering led to a general mindset
Shellfi sh Aquaculture and the Environment, First Edition. Edited by Sandra E. Shumway. 2011 John Wiley & Sons, Inc. Published 2011 by John Wiley & Sons, Inc.
426 Shellfi sh Aquaculture and the Environment
water quality degradation (Chapter 7 ); changes in sediment chemistry and composition (Chapter 10 ); habitat degradation, altered bio-diversity and community structure (Chapters 5 and 9 ); the introduction of nonnative species including predators, pests, and disease; the spread of harmful algal blooms (Chapters 13 and 14 ); and the loss of genetic diversity in wild shellfi sh populations (Chapter 12 ).
Some studies have indicated that intensive shellfi sh production can result in ecosystem - level changes in water quality (Souchu et al. 2001 ), phytoplankton biomass (Nichols et al. 1990 ; Banas et al. 2007 ), and benthic sediment chemistry and composition (Dahlback and Gunnarsson 1981 ; Kaspar et al. 1985 ; Figueras 1989 ; Grant et al. 1995 ; Cranford et al. 2003 ) (see Fig. 15.1 ).
Direct and indirect impacts to critical habitats and changes in biodiversity have been linked to operations that utilize sub-merged or fl oating cultivation structures, inter-tidal rearing methodologies such as predator netting, or harvesting gear such as dredges. Physical disturbance such as scouring and
that shellfi sh cultivation is a benign use of the marine environment. However, the con-tinuing controversy over the effects of marine fi sh farming and the common misconception that shellfi sh aquaculture incorporates similar husbandry techniques has driven environmen-talists, scientists, regulators, and industry in the United States and elsewhere to reconsider this view. Consequently, there has been more of an impetus to fully investigate and properly document the potential for immediate and local effects resulting from shellfi sh farming, as well as the probability for longer - term and estuary - wide effects to occur. The purpose of this chapter is to highlight the current frame-work for and emphasize the national trends in the regulation of bivalve shellfi sh aquaculture within the United States.
Environmental e ffects
The principal concerns with respect to the interaction of shellfi sh aquaculture and the environment are generally considered to be
Figure 15.1 Longline mussel culture.
Development and conservation: Role of resource managers 427
and disease - causing organisms is a signifi cant ecological and economic problem (McKindsey et al. 2007 ). As such, most states now require a shellfi sh transport permit that certifi es that the product (larvae, seed, or adult shellfi sh) is a native species, disease/toxin - free, and will not pose harm to existing shellfi sh populations.
Recent studies have demonstrated the potential for a loss of genetic diversity when hatchery stocks interbreed with wild popula-tions of shellfi sh (Arnold et al. 2004, 2009 ). Interbreeding is especially diffi cult to prevent or control as many molluscan shellfi sh are broadcast spawners and larvae can be carried long distances away from their reproductive populations (Chapter 12 in this book).
This is not to suggest that the benefi cial aspects of shellfi sh culture should be over-looked or underestimated. The current body of knowledge and scientifi c documentation is replete with the value of shellfi sh and shell-fi sh aquaculture for their ability to improve water quality and clarity making the environ-ment more suitable for aquatic organisms.
sedimentation can indirectly impact biodiver-sity by altering or removing essential habitat. Of particular interest to resource managers is the potential for adverse effect to threatened or endangered species (e.g., mammals, birds, turtles, and migratory fi sh) and protected habi-tats such as submerged aquatic vegetation ( SAV ) (see Fig. 15.2 ). Such disturbances to fed-erally protected species such as Pacifi c salmon (Simenstad and Fresh 1995 ; Thom 2009 ) as well as negative impacts to special habitat such as seagrasses have been documented (Everett et al. 1995 ; Tallis et al. 2009 ). However, these impacts are very site and gear specifi c. In addi-tion, intentional and accidental introductions of aquatic organisms have resulted in signifi -cant and often undesirable consequences to aquatic environments (Nichols et al. 1990 ). Aquaculture, in general, is now the leading cause of nonnative introductions (Chapter 14 in this book) to inland aquatic ecosystems (Welcome 1988 ) and introductions to marine waters have also been documented. In addition to the unintended spread of the target culture species, the proliferation of predators, pests,
Figure 15.2 Aquaculture operations in eelgrass beds.
428 Shellfi sh Aquaculture and the Environment
level of three - dimensional complexity and hard substrate that results in enhancement of the diversity and abundance of biota that is similar or greater than natural marine habitats (Brehmer et al. 2003 ; Crawford et al. 2003a ; DeAlteris et al. 2004 ; O Beirn et al. 2004 ; Roycroft et al. 2004 ; Lindahl et al. 2005 ; Pinnix et al. 2005 ; Wechsler 2006 ; Powers et al. 2007 ; Clynick et al. 2008 ; Erbland and Ozbay 2008 ) (see Fig. 15.3 ).
Filter - feeding molluscs achieve this by reduc-ing excess phytoplankton associated with eutrophication and other fi ne particulate matter, and transforming inorganic nutrients into bioavailable forms (Reusch et al. 1994 ; Peterson and Heck 2001a, 2001b ; Newell 2004 ; Newell and Koch 2004 ). In addition, the shellfi sh, the physical aquaculture struc-tures themselves, and in some cases the associ-ated shell deposits can all serve to provide a
Figure 15.3 Physical aquaculture structures as enhanced three - dimensional structure and hard substrate for other organ-isms. (A) A lobster (inset) in a cage full of oysters; (B) a godwit foraging among cages.
Development and conservation: Role of resource managers 429
The effects of aquaculture on the estuarine environment, whether benefi cial or detrimen-tal, are highly dependent on the species cul-tured and the type, scale, intensity, and frequency of the activity (Kaiser et al. 1998 ; Folke et al. 2004 ; Vaudrey et al. 2009 ; see also Chapter 9 in this book). In addition, the inten-sity and temporal and spatial extent of the effects may vary in response to the local envi-ronment s resistance to change (Bradbury et al. 1983 ; Simenstad and Fresh 1995 ). Most experts agree that scale and intensity are two of the more important management consider-ations when permitting aquaculture and that understanding the effect of scale is critical to planning for sustainable aquaculture produc-tion (Dumbauld et al. 2009 ). Unfortunately, information on these effects is lacking as few studies in the United States until recently have assessed the cumulative and additive effects of multiple farms and estuary - wide effects of shellfi sh aquaculture.
Social e ffects
In addition to environmental effects, other major considerations in the siting of aquacul-ture operations include the impact to naviga-tion and other competing uses of the coastal zone, and concern that the activity will result in undesirable aesthetic impacts such as visual and noise pollution. Societal issues such as these also have the potential to impede the growth of the bivalve shellfi sh aquaculture industry along populated coastlines (see Fig. 15.4 ).
Although these impacts are diffi cult to assess and mostly due to subjective interpreta-tion, their consideration is nonetheless neces-sary as coastal waters are generally held in public trust for the benefi t of all (Fernandez 1996 ). Although it is important to mention that societal concerns can be critical to the successful siting of shellfi sh aquaculture proj-ects, we note that their discussion is beyond the scope of this chapter.
The uncertainty with respect to environ-mental interactions and social confl icts associ-ated with shellfi sh aquaculture