BOOK REVIEW

Sandra E. Shumway (Ed.) : Shellfish aquacultureand the environment

Xavier de Montaudouin

Received: 10 February 2014 /Accepted: 26 February 2014 /Published online: 26 March 2014# Springer-Verlag Berlin Heidelberg 2014

In the twenty-first century, there are two certainties concerningmarine resources. First, there will be an increasing need ofmarine products in order to help feed the 8 billion humanbeings in 2028. Second, there is also an increasing concernabout the necessity to preserve the biosphere diversity. Thisbook is written considering both aspects. It is not a book aboutshellfish aquaculture techniques but rather about the interac-tions among shellfish cultures and the environment, scruti-nized at different scales. Thus, on the book cover, the readercan consider that the words “and the environment” shouldreally have the same font than the rest of the title. Globally,this review brings evidence that in most situations, shellfishaquaculture has rarely a negative impact on the environmentbecause molluscan shellfish are largely grown in natural wa-ters without addition of feed, and these waters are required tobe of the very highest quality. The major risk of deleterious

effects, however, is via the introduction of disease agents intonew areas.

The three first chapters deal with aquaculture as an indus-try, primary concerns being environmental integrity, foodsafety, and economic sustainability. Chapter 1 highlights thebenefits of aquaculture on marine ecosystems, especially byremoving waste nitrogen from the sea and consequently de-creasing the risks of eutrophication (see also chapter 5). This isa relevant demonstration of the joint notion of “ecosystemgoods” and “ecosystem services.” The chapter underlines theadded value of integrated multi-trophic aquaculture (IMTA)compared to monoculture and the use of model tools such asASSETS or FARM. A strong limit of aquaculture industrydevelopment is the absolute necessity to keep exceptionallyclean waters (e.g., for raw consumption), which necessitatespolicies taking into account other coastal activities (chapter 2),the development of best management practices (BMP), and anassociated code of conduct (chapters 2 and 3). Chapter 3 inparticular investigates all market strategies that have beenextrapolated to shellfish aquaculture (ecolabeling, traceability,Label Rouge…) and discusses the positive/negative impactfor environment and economic sustainability. The authorsshow the multifaceted paths required to meet FAO guidelines(animal health and welfare, food safety and quality, environ-mental integrity, social responsibility). On the other hand, asthe effects of shellfish aquaculture are often perceived asrelatively harmless to the environment, this explains the factthat ecolabeling programs are still scarce (examples areprovided).

In shellfish aquaculture, most of the production is due tobivalves whose connection with the environment is intimatelyrelated to a suspension-feeding activity. As previously men-tioned, this behavior is a key point to consider shellfishaquaculture as a contributor to the sustainability of coastalecosystems by decreasing the risk of eutrophication. From thepoint of view of production efficiency, suspension feeding

BibliographyShellfish Aquaculture and theEnvironmentSandra E. ShumwayWiley-BlackwellISBN: 978-0-8138-1413-1Hardcover, 528 pagesOctober 2011, 174 €

Responsible editor: Philippe Garrigues

X. de Montaudouin (*)University of Bordeaux, UMR EPOC 5805, CNRS, ArcachonMarine Station—2 rue du Pr Jolyet, 33120 Arcachon, Francee-mail: x.de-montaudouin@epoc.u-bordeaux1.fr

Environ Sci Pollut Res (2014) 21:7781–7783DOI 10.1007/s11356-014-2708-z

calls into question the carrying capacity of an ecosystem (i.e.,how much biomass of a given species is a system capable tosupport without decline of production?). Chapters 4 to 6 dealwith that topic. Chapter 4 focuses on the fundamental questionof the assessment of the quantity of water and/or seston asuspension feeder is able to filter. There is an extensive reviewabout the notion of “clearance rate” (volume of water clearedof particles of a certain size in a given period of time), the mostutilized parameter to measure suspension-feeding activity.The authors, through an updated investigation of the associ-ated literature, discuss the numerous factors explaining thehigh intra- and interspecific variations of clearance rate, andinclude spatio-temporal variations. They are particularly vig-ilant on the different methodological biases that intervene toexplain variability. One strong conclusion is that there is acontinuum of strategies ranging from species that primarilyregulate clearance rate to those that mainly regulate the pro-duction of pseudofeces, to others that employ both mecha-nisms. This extensive chapter ends with identification of twoside-effects of suspension feeder-activity at the ecosystemscale: Firstly, the production of transparent exopolymer parti-cle (TEP) that may enhance seston sedimentation and activatebentho-planktonic coupling; and secondly, the modification ofphytoplanktonic communities by filtration of a given range ofparticles >2 to 8 μm (which can promote picophytoplanktonicspecies). Chapter 5 briefly describes the mutual interactionsbetween phytoplankton and bivalves, and expounds the pos-itive effects against eutrophication (see chapter 1). The authorargues that most cultivated bivalves are naturally gregariousspecies (mussel “beds”, oyster “reefs”) and that high densityculture can promote conditions that are not far from what isobserved in “natural” environments. A negative impact ofbivalves could be facilitation of non-diatom species prolifer-ation (including harmful dinoflagellate) by modifying thesilicate cycle, but this argument is still speculative. The notionof carrying capacity is highly scale-dependent and rathersubjective, a relevant proposed definition being “the carryingcapacity is reached when the positive consequences balancethe negative consequences.” In terms of carrying capacity,however, the usual objective is to balance the biomass offarmed animals with the amount of food available and pro-duction of waste. Thus, chapter 6 comments on the differentsimulation models (biogeochemical, bivalve ecophysiology,and physical oceanographic modes) and explores the relation-ships of these carrying-capacity models with ecosystem-basedmanagement (i.e., farm management).

At this stage of the book, the role of bivalves, as filter-feeders, in the control of primary production is evident, andconsequently, their ability to reduce occurrence of phyto-plankton blooms and related deleterious effects is stronglysuggested. On the other hand, high densities of bivalves couldalso stimulate algal production by releasing nutrients throughfeces, pseudofeces, and excretion. Chapter 7 is focused on the

subtle relationship between bivalves (in aquaculture) and eu-trophication processes. This analysis is accompanied by anextensive review of the literature dealing with, for example,shellfish aquaculture and eutrophication, or comparing nutri-ent excretion rates among the main cultivated bivalves. Oneconclusion is that, in most cases, ecosystems have sustainedeither negligible or localized significant adverse effects con-tributing to eutrophication from bivalve aquaculture (out of 72investigated areas). Ecosystem malfunction mainly occurswhen hydrodynamics is poor and/or density is too high (e.g.,Sacca di Goro example) which underscores the need to con-sider ecosystem-carrying capacity. However, while bivalveculture can improve water quality by avoiding an overloadof nutrients, it is also observed that many shellfish populationsare nowadays negatively impacted by increasing land-basedsources of population. Chapter 7 also comes back to thebenefits of IMTA (chapter 1), and a thoroughly detailed ex-ample is provided in chapter 8 with mussel aquaculture inSweden.

Beyond control of eutrophication, shellfish aquaculturegenerates numerous “ecological services” that are describedin chapter 9. As engineer species, the habitat they build (reefs,shell aggregation, and shell accumulations) often promotesdiversity and may be essential for several associated species,including finfishes, shore birds, and presumably mammals.This chapter focuses on a fourth habitat, “cultured specieswith associated gear” (ropes, rebars, etc.) and discusses pos-itive and negative impacts on the environment, with specialattention to the case of northern quahog. The risk of shellaquaculture based on new exotic species (e.g., Crassostreaariakensis from China/Japan to Chesapeake Bay) is also ar-gued. A less studied role of (infaunal) bivalves as key speciesis their ability to bioturbate and bioirrigate the sediment andconsequently to impact surrounding benthic communities(chapter 10). However, many studies show that the mostvisible impact of shellfish activity is often observed whenmechanical harvesting is required (chapter 11) and provokeshabitat loss, biomass decline (including capture of non-targetspecies), and sediment resuspension (turbidity and its negativeeffect on submerged aquatic vegetation). On the other hand,resulting impact is also relatively easy to detect, and a protocolbased on two-way analyses of variance design is proposed(BACI, for before-after-control-impact).

An up-to-date review about shellfish culture requires achapter considering recent practice dealing with genetics sensulato, through crossbreeding attempts, selection, or triploidy(chapter 12). These research strategies appear less risky thanthose dealing with introductions or translocations which re-quire enforced controls (quarantine, extensive disease testing).Some progress was made in terms of yield improvement(Pacific oyster) and disease resistance. Infectious diseases areoften considered as the first source of mortality in aquaculture.Disease occurrence is the expression of the interaction between

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pathogen agents and hosts in a given environment (maindrivers being salinity and temperature). Shellfish cultures rep-resent hot spots due to high “host” density and possible trans-port among sites, both promoting epizootic diseases.Chapter 13 provides discussion of health management andbiosecurity, pointing out the particular problem of transfersthat may act as a vector of pathologies. Most examples concernthe top four parasites that cause mortality in shellfish culture,Haplosporidium, Perkinsus, Marteilia, and Bonamia, but ex-tend to other pathogens (Vibrio spp., viruses, etc.). Even with-out any associated pathogens, transfer of shellfish amongaquaculture sites represents a potential threat for exotic speciesintroduction, along with other traditional vectors, such as shipfouling and ballast or aquarium activity (chapter 14). Fourtables enumerate native- and non-native-cultured bivalves(1), bivalve species that have escaped in regions outside theirnative range (and impacts) (2), species introduction associatedwith bivalve aquaculture activity (3), and their impact (4).

Apart from scientific expertise and farmers management,the two following chapters highlight the role of resource

managers exemplified by the US shellfish industry (regula-tions, best management practices (BMP), organization of per-mitting agencies, marketing) (chapter 15) and the necessity todevelop educational programs (primary, middle, and uppergrades) that provide outreach and technology transfer to shell-fish aquaculturists (chapter 16).

Finally, chapter 17 is the inescapable focus on the implica-tions of global climate change for shellfish aquaculture, aparticularly climate-sensitive sector of the economy. This partprovides an interesting review of the literature concerning themain possible causes and consequences related to climatechange that may impact bivalve production, e.g., sea acidifi-cation, increased frequency of exceptional meteorologicalevents, or temperature increase that could (1) enhance fre-quency and/or virulence of pathogenic infection, (2) increasefrequency and intensity of harmful algae blooms (HABs), and(3) affect reproduction/recruitment/growth/survival of bi-valves. The authors also consider the possible benefits ofwarmer waters and conclude in suggesting adaptation process-es by stakeholders.

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