Shellfi sh Aquaculture and the Environment COPYRIGHTED MATERIAL Chapter 1 The r ole of s hellfi sh f arms in p rovision of e cosystem g oods and s ervices Jo ã o G. Ferreira , Anthony J.S. Hawkins , and Suzanne B. Bricker Introduction It is not unusual to use different culture techniques for the same species at different What i s a f arm? stages of the growth cycle, or to rear benthic organisms off- bottom, taking advantage of a Shellfi sh farms vary widely in type, situation, greater exposure to pelagic primary produc- and size. The type of culture can vary accord- tion, better oxygenation, and predator ing to species, and even within the same species exclusion. various approaches may be used, depending In a similar way, shellfi sh can be grown in on factors such as tradition, environmental intertidal areas, competing for space with conditions, and social acceptance. For instance, other uses (e.g., geoduck grown in PVC tubes mussels are cultivated on rafts in Galicia in Puget Sound, USA; oysters on trestles in (Spain), and on longlines in the Adriatic Sea Dungarvan Harbour, Ireland), or subtidally (Fabi et al. 2009 ). But they are also grown on (e.g., scallop off Zhangzidao Island, northeast poles in the intertidal area in both France China). Cultivation takes place within estuar- ( bouchot ) and China ( muli zhuang ), or dredged ies, coastal lagoons, and bays (e.g., Figure from the bottom in Carlingford Lough 1.1 ), and increasingly in offshore locations, (Ireland) and in the Eastern Scheldt (the where there are less confl icts with other stake- Netherlands). holders in the coastal zone. In many parts of 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. 3 4 Shellfi sh Aquaculture and the Environment Figure 1.1 Aquaculture in Sanggou Bay, northeast China. Longlines used for shellfi sh culture are clearly visible in satel- lite images. the world, onshore cultivation is also a reality, Table 1.1 Dependency of Chinese lease units on as occurs in Guangdong province (China) and carrying capacity. elsewhere for razor clams and oysters, fre- 2 quently in multispecies combinations (e.g., Bay or system Unit name Area (m ) Ferreira et al. 2008a ; Zhang et al. 2009 ; Nobre All land - based Mu 666.66 et al. 2010 ). agriculture (1/15 ha) The size of farms may vary widely, given Sanggou Bay Culture Mu 1600 – 1800 various constraints imposed by physical space, Jiaozhou Bay Culture Mu 3000 – 5000 environmental conditions (which directly infl uence production), ecological effects, and Laizhou Bay Culture Mu 5000 – 8000 social acceptability. An obvious constraint on the viability of a shellfi sh farm is the natural food supply, which in some areas of For the purposes of this text, a farm is the world has a direct relationship to the lease therefore defi ned as an integrated production units. For instance, in China, the aquaculture unit, typically allocated as a lease, subject to cultivation unit is the Culture Mu (Nunes specifi c pressures with associated impacts (Fig. et al. 2003 ); in a similar way to the medieval 1.2 ). This can be an area of sea bottom where bushel, the actual area of this unit varies molluscs are grown (e.g., mussel/oyster culture, among different bays, depending on the typical abalone in pens), off- bottom (but overlying carrying capacity per unit area of each bay, bottom space) such as oyster trestles, or an as exemplifi ed in Table 1.1 for Shandong area of water where rafts or lines are placed province. (droppers off longlines, Chinese lanterns), or Role of shellfi sh farms in the ecosystem 5 Pressures LAND SEA Nitrogen Phosphorus Ponds Fish, shellfish Shellfish structures, Fish cages Inshore Reduced Conflicts Conflicts eutrophication Land use, social issues Wild species, space, social Impacts Figure 1.2 Aquaculture farms: illustration of pressures, activities, and impacts on the coastal fringe. ponds fringing coastal areas (razor clams). 2004 ). The aim of IMTA is to increase long- Whether farms are located on the bottom, off- term sustainability and profi tability per culti- bottom, or as suspended structures, they gen- vation unit (rather than per species in isolation, erally preclude the use of the sea bottom for as is done in monoculture), in which all the other human activities, such as fi shing or rec- cultivation components have economic value, reation, and raise controversial issues related and each has a key role in services and recy- to multiuser interactions, as discussed in cling processes of the system. Chapter 9 (in this book). Many of the analyses presented in this This chapter examines the role of the shell- chapter are carried out by means of mathemat- fi sh farm as a provider of ecosystem goods and ical models, so we begin with a review of services. The focus is on farms located in open methodologies that provide the necessary estuarine and marine waters, from the inter- grounding for the development and applica- tidal zone to offshore locations. Although this tion of such models. We then examine some of book is aimed at shellfi sh ( sensu bivalve the available options in the area of predictive mollusc) aquaculture, it is impossible to modeling, and the remainder of the chapter address the current state of the art of shellfi sh reviews two main aspects: farming without the inclusion of integrated multitrophic aquaculture ( IMTA ), an approach 1. Ecosystem goods supplied by shellfi sh that has been practiced in Southeast Asia for farms. The emphasis is on production, and thousands of years, both in ponds and in open its optimization, including IMTA. systems (Ferreira et al. 2008a ), and is currently 2. Ecosystem services supplied by shellfi sh attracting considerable interest (Neori et al. farms. The environmental role of shellfi sh 2004 ; Ridler et al. 2007 ; Paltzata et al. 2008 ). farms extends well beyond the harvest of IMTA combines, in the right proportions, shellfi sh per se, and includes interactions the cultivation of fed aquaculture species (e.g., such as top - down control of eutrophication fi nfi sh) with organic extractive aquaculture symptoms (see Chapters 7 and 8 in this species (e.g., molluscan shellfi sh) and inor- book). ganic extractive aquaculture species (e.g., sea- weeds) for a balanced ecosystem management Case studies are used throughout to illustrate approach that takes into consideration site the practical application of principles and specifi city, operational limits, and food safety techniques in real - world situations, drawing guidelines and regulations (e.g., Neori et al. from examples worldwide, including the 6 Shellfi sh Aquaculture and the Environment European Union ( EU ), North America, and 2. Landings statistics are often inaccurate due Southeast Asia. to underreporting, and in some cases (Watson and Pauly 2001 ), overreporting. 3. Farming practice, in the sea as on land, is Methods of s tudy adapted according to variations in growth, environmental conditions, and market Defi nition of c ulture p ractice requirements. Corresponding data with respect, for example, to the dimensions of An accurate description of culture practice is target species, or timings of seed and a key factor in the implementation of success- harvest, are by nature fuzzy. Models that ful aquaculture models. The parameters of use a deterministic approach do not accom- interest may be divided into three groups, modate this type of information well. In which will be examined in turn: cases where natural spatfall is used (e.g., by means of oyster spat collectors) as opposed 1. Spatial parameters : These include the farm to hatchery - purchased seed, there is an dimensions, positioning (e.g., height above additional stochastic component of interan- tidal datum for intertidal culture such as nual variability. oyster trestles), orientation, internal parti- tioning, and crop rotation. Because all these data are model forcing func- 2. Temporal parameters : Data such as the tions, they severely constrain simulation periods of seeding and harvest, together outputs. For instance, in Belfast Lough, the with the seeding and harvest effort, are lease areas for bottom mussel culture are critical for accurate simulations of rotated over a 3 - year cycle to allow an annual production. harvest for animals which grow to maturity 3. Morphological and physiological parame- over a period of 30 months (Fig. 1.3 ). Clearly, ters : The range of weights of seed or spat, a failure to account for this will overestimate the cutoff weight for harvest, mortality production, irrespective of the accuracy of the rates, and any relevant infl uences on growth underlying growth models. (e.g., fouling) are the fi nal elements of As a fi nal caveat, the determination of culture practice description that must be natural mortality ( m ) poses a particular chal- considered. lenge. In general, this is applied as an average Although these data appear, in general terms, easy to acquire and less challenging to inter- Harvest Harvest pret and simulate than measures of individual Year 3 Year 4 growth or biodeposition, experience shows Seeding Seeding that accurate validation of culture practice Year 1 Year 2 poses a major challenge and can be a signifi - cant liability for ecological models of aquacul- ture (Ferreira et al. 2008b ). The main Seeding diffi culties in obtaining consistent data are due Year 3 to the following factors: Harvest 1. Commercial interests introduce an element Year 5 of confi dentiality that is diffi cult to Figure 1.3 Crop rotation in northern Irish mussel bottom overcome. culture (Ferreira et al. 2007b ) . Role of shellfi sh farms in the ecosystem 7 for the culture period, neglecting the fact that algal blooms, losses of submerged aquatic the mortality rate will depend both on the life vegetation [ SAV ]); and (3) Future Outlook stage of the organism (e.g., will be higher for (Response) — an evaluation of likely future small animals and postspawning) and on conditions resulting from changes in nutrient environmental factors such as temperature, load that are based on projected population dissolved oxygen ( DO ), and predation.