Design theory in offshore fish cage designing

    Design theory in offshore fish cage designing M. Shainee, H. Ellingsen, B.J. Leira, A. Fredheim PII: DOI: Reference:

S0044-8486(13)00081-1 doi: 10.1016/j.aquaculture.2013.02.016 AQUA 630553

To appear in:

Aquaculture

Received date: Revised date: Accepted date:

19 December 2011 29 October 2012 14 February 2013

Please cite this article as: Shainee, M., Ellingsen, H., Leira, B.J., Fredheim, A., Design theory in offshore fish cage designing, Aquaculture (2013), doi: 10.1016/j.aquaculture.2013.02.016

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ACCEPTED MANUSCRIPT DESIGN THEORY IN OFFSHORE FISH CAGE DESIGNING. M. Shaineea, H. Ellingsena, B. J. Leiraa a

CREATE-Center for Aquaculture Technology, SINTEF Fisheries and Aquaculture, P.O.Box 4762 Sluppen, N7465 Trondheim, Norway Email: [email protected]

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b

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A. Fredheimb

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Department of Marine Technology, NTNU, 7491 Trondheim, Norway Email: [email protected]; [email protected]; [email protected]

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Abstract

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Population increase, food security, employment, stresses on the fresh water resources and uncertainty associated with wild fish stocks are key parameters driving the demand for aquaculture expansion. Limitation in adequate waters in the coastal and near-shore sites for

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aquaculture development and the interactions within and from other coastal services forces the fish farming industry to move further offshore. Impact on the environment is an increasing

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concern that has to be considered in any aquaculture system designing. Moving further offshore could provide a better return on investment through various factors such as reduced

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mortality, better growth rates, less diseases and net fouling. However, moving offshore comes with a new set of challenges in withstanding severe weather conditions and safe and economic functioning of the aquaculture systems. Currently, the offshore fish cage design concepts are in their infancy and there is a race towards an optimum cage design for the offshore environment. Hence, in the aim of deriving an optimum cage design concept, this paper attempts to apply a holistic and theoretical approach to fish cage designing. By the application of theory of design, but different from the traditional engineering designing process, the paper proposes a conceptual framework and a cage design concept for offshore fish cage designing. Keywords: Offshore aquaculture; Design theory; Stakeholder; Functional requirement; Design framework. 1

ACCEPTED MANUSCRIPT 1. Introduction A large percentage of the human population depends on marine living resources for food,

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protein and income. In 2008, 44.9 million people were directly engaged in primary production

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of fish, either by fishing or aquaculture (FAO, 2010). Worldwide, fish products provide at

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least 20% of the animal protein intake for 1.5 billion people and support the livelihoods of approximately 540 million people (FAO, 2010). However, anthropogenic impacts coupled

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with climate change are implying grave doubts on ocean fisheries stocks. Though the proportions of overexploited, depleted and recovering stocks have remained relatively stable

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in the past decade or so (FAO, 2010), uncertainty in actual biomass due to the illusive nature of reporting on discards and by-catches (Alverson et al., 1994; Hall et al., 2000; Kelleher,

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2005), sluggishness in realizing the changing trends in fisheries biomass (Olsen et al., 2008)

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and uncertainty and variability associated with climatic variations (Brander, 2010; Grafton, 2010; Stenevik and Sundby, 2007) are reasons to be concerned and to look for alternatives.

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The human population is increasing constantly and has reached 7 billion in 2011, which exacerbates the need for an alternative. Therefore, an alternative source of food, protein and

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income is eminent. Aquaculture seems to provide a promising alternative. The high demand or future prospect for aquaculture is driven by multiple factors. Olsen et al. (2008) suggested that the growth of the human population will put enormous stress on the availability of water to produce food for humanity. Water scarcity and its limitation on agricultural production and food security are therefore of major concerns (Rijsberman, 2006; UNESCO-WWAP, 2009; Yang et al., 2003). One solution is to enhance the food production from the marine environment. Realizing that the food fish from wild fish harvest cannot keep pace with the growing population, in the opinion of the authors, the only foreseeable alternative is aquaculture. This opinion is shared by many researchers, for example, Olsen et 2

ACCEPTED MANUSCRIPT al. (2008) claims that the likely exhaustion of the capacity of agriculture to feed a growing human population and the need to increase fish production beyond the sustainable exploitation

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of wild stocks to meet the market demands are likely to be the driving forces for further

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expansion of aquaculture.

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Some countries have already envisioned the opportunities provided by aquaculture to meet the growing demand for fish. Global aquaculture production increased by nearly 50% between

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1997 and 2003, while capture fisheries decreased by nearly 5% in the same period (Brander, 2010). Today, aquaculture is the fastest growing animal food-producing sector to outpace

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population growth, with an annual growth of 6.6 percent (FAO, 2010). Fish produced from aquaculture accounts for nearly half of the food fish consumed by humans (FAO, 2010).

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Analyzing various trends from different sources, Olsen et al. (2008) predicts 0.4% to 5.3%

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growth in aquaculture production per year, for a period between the present and 2020 to 2050.

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Increasing demand for aquaculture has led to competition in acquiring appropriate near-shore waters for farming. Coastal ecosystem services such as near-shore fisheries, housing, leisure activities, safer ship berth, navigation and other commercial and recreational interests are in

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direct competition for limited coastal or near-shore waters (Baldwin et al., 2002). In recent years, there has also been increasing criticism from environmental groups (Colbourne, 2005). Eutrophication, transmittal of diseases to wild fish, inter breeding between the farmed and wild fish, noise, odor and visual pollution are amongst the areas of concern raised by many environmentalists (see Grigorakis and Rigos (2011), for a review). In the meantime, some researchers have also suggested that moving further offshore provides better return on investment (Loverich and Croker, 1993; Sveälv, 1991) for fish farming through various factors. Positive attributes in offshore aquaculture includes less polluted water, natural dispersion and dilution of waste, the possibility of using deeper and bigger 3

ACCEPTED MANUSCRIPT netpens and of almost limitless expansion. As a consequence, offshore aquaculture can lead to reduction in mortality, better growth rates and less visceral fat (Addis et al., 2010; Pogoda et

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al., 2011; Ryan et al., 2007; Sveälv, 1988). Also, offshore farms are less susceptible to

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diseases and marine growth on the cage system. Therefore, aquaculture in offshore waters is

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becoming increasingly attractive and has been a focus of international attention since the 1990s (Langan, 2009). As such, Ireland, Scotland, Faroe Islands, Canada, Canary Islands, Australia, Mediterranean and Mexico have begun offshore fish farming operations (Fredheim

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and Langan, 2009).

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While aquaculture in near-shore waters has to compete with the other coastal activities (Baldwin et al., 2002; DeCew et al., 2005), the desire to move further offshore to reduce

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competition for space among aquaculture operators is also realized. The scarcity of suitable,

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well sheltered sites arising from intensive farming of near-shore waters is partially responsible for forcing the fish cages further offshore, into more exposed environments (Colbourne,

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2005). Not the least of the problems, arising from intensive farming of near-shore waters, is the spread of fish disease and poor growth of fish. For instance, in the mid 80s, Norwegian

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fish farmers started to look into offshore sites after realizing the reduced rate of growth due to the self-pollution of fish farms (Rudi and E.Dragsund, 1993). Morimura (1993), reported that less than just a decade after Japan’s farming industry started, the self-pollution of the water in and around fish farms lead to the spread of fish diseases and causing incomplete growth of fish in breeding. In fact, Morimura (1993), claims that it is this factor along with the impacts of fish farming on other industries such as tourism that lead to the first ever attempt to move the farms further offshore in Japan. Considering the multifaceted factors required for fish farming, the spatial limitations in the narrow coastal corridors are obvious.

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ACCEPTED MANUSCRIPT Moving aquaculture farms offshore will help avoid conflicts between users and address some environmental concerns, while at the same time providing a better production environment.

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However, moving further offshore presents a new set of challenges in withstanding severe

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weather conditions and safe and economic functioning of the aquaculture systems. Currently,

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offshore fish cage design concepts are in their infancy and there is a race towards optimum cage design for offshore or open water environments. The term “offshore” is used here as

Classification of off-shore water developed in Norway based on significant wave heights.

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Significant Wave Height (m) < 0.5 0.5 – 1.0 1.0 – 2.0 2.0 – 3.0 > 3.0

Degree of Exposure Small Moderate Medium High Extreme

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Site Class 1 2 3 4 5

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Table 1

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defined by Ryan (2004)(see Table 1).

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With the aim of deriving an optimum cage design concept, this paper attempts to apply a holistic and theoretical approach to the design of fish cages. Section 2 briefly considers design theory and offers an alternative view to the traditional engineering design process in order to

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reflect that aquaculture development is an emerging industry and hence innovative solutions needs considerable attention paid to the design process. Sections 3 and 4 outline the results of an intensive literature review and ongoing consultations for aquaculture development, such as those currently carried out by European Aquaculture Technology and Innovation Platform (EATiP, 2011), to identify the functional requirements and key design parameters for the design of fish cages. Finally, through design synthesis the paper offers a conceptual framework, which could help designers to systematically design an offshore fish cage. The synthesis of functional requirements and design parameters also allowed the authors to propose a generic concept for the design of an aquaculture cage system. 5

ACCEPTED MANUSCRIPT 2. Design Process The design process is “a systematic problem solving strategy, with criteria and constraints,

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used to develop many possible solutions to solve a problem or satisfy human needs and wants

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and to narrow down the possible solutions”(Karsnitz et al., 2009). In general the process starts

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by defining the problem and relating these problem definitions to a set of functional requirements that have to be satisfied in order to achieve the overarching goals. The process

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ends with the creation of an artifact that satisfies the outlined needs. According to Suh (Suh, 1990), design may be formally defined “as the creation of synthesized solutions in the form of

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products, processes or systems that satisfy perceived needs through the mapping between the functional requirements in the functional domain and the design parameters in the physical

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domain, through the proper selection of design parameters that satisfy functional

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requirements”. The mapping process is not unique and hence the outcome depends on the intuition and experience of the designer and the method that the designer might choose to map

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them. Therefore, assigning correct functional requirements and identifying effective design parameters are very important for the final outcome.

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There are well established approaches to what has been referred to as the mapping process that can be applied to navigate from the functional requirements to the final product. However, choosing the correct process is problematic, as there are far too many methods proposed (see Roy et al. (2001) for a review of methods) and as many critiques for and against different processes. In general, the problem seems to arise due to two schools of thoughts arguing for and against design as a science. Design as a science requires it to have laws and principles in creative process involving design, synthesis and decision making (Simon, 1981). According to this school of thought, the design otherwise remains just as a mysterious creative process, where we can appreciate the outcome of the intellectual endeavor but do not 6

ACCEPTED MANUSCRIPT understand the process that produces the outcome, and cannot quantify the results (Suh, 1990). On the flip side, other school of thought, including Coyne et al. (Coyne, 1990) states

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that, science attempts to formulate knowledge by deriving relationships between observed

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phenomena, while design begins with intentions and uses available knowledge to arrive at an

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entity processing attributes that will meet the original intentions. Therefore, design and science appear to be about different things (Coyne, 1990; Kroes, 2002).

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The opinions of the authors are amongst those, such as Coyne et al. (1990), Jakobsen et al. (1991) and Nadler (1989), who argue that design appears to be ill-structured in the sense that

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there is no straightforward process to be followed. Therefore, there cannot be a unique process as the problems that we try to solve cannot be alike. Stressing this point, Nadler (1989),

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argues that engineering profession alone commonly recognizes at least four generic kinds of

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problems that obviously cannot be handled in identical manner. The four problem areas are: improvement of an existing system; diagnosis and remedy of some trouble; development of a

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new system; and development of new use for an existing system (Nadler, 1989). Therefore, ‘technical artifacts’ (Kroes, 2002; Simon, 1981) require different processes depending on the

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physical structure, technical functions and the environment. The environment here refers to the physical, economic, social and ecological environment. This points out towards a ‘systems thinking’ (Ackoff, 1979a, b), a ‘holistic approach’ or ‘total approach’ (Nadler, 1989) that incorporates social, technical, environmental and ecological principles in the design process. In order to internalize such a wide range of disciplines, the designer has to adopt different approaches, a wide range of skills and knowledge, and consult specialists on the related problems (Pahl and Beitz, 1999).

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ACCEPTED MANUSCRIPT Regardless of the process or processes used in designing, both schools of thought agree that the process should be structured in a purposeful way that is in a clear sequence of main phases

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and individual working steps, so that the flow of work can be planned and controlled (Pahl

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and Beitz, 1999). These main phases, as defined in engineering design, are: 1)

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conceptualizing, that is searching for solution principles; 2) embodying, that is engineering a solution principle by determining the general arrangement and preliminary shapes of key components; and 3) detailing, that is finalizing production and operating details (Pahl and

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Beitz, 1999). Our main attempt in this paper is to formulate a conceptual framework that

attributes of the aquaculture industry.

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encapsulates these phases in designing, but in such a way that the framework reflects the

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3. Functional Requirements

If design is defined as the creation of synthesized solutions in the form of products, processes

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or systems that satisfy perceived attributes of the product, then, functional requirements are the designer’s description of the perceived needs from the product (Suh, 1990). The product

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can be in the form of a physical device, a process, software, system or an organization. For the purpose of the present paper, the product is the fish cage. In axiomatic design, functional requirements are a set of independent requirements that completely characterize the design objective for the given need (Suh, 1990). Since different designers have different levels of experience and knowledge, the designers perceived needs of the product can be very different from the other designers. This is why we see many different designs of fish cages, basically serving a very homogeneous need of growing fish. The design of the cage is very much influenced by the ability of the designer to correctly capture the perceived needs and requirements of the system. 8

ACCEPTED MANUSCRIPT For the design to be successful, it is very important to get the functional requirements correct, “because the final design cannot be better than the set of functional requirements that it was

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created to satisfy” (Suh, 1990). Defining appropriate functional requirements and design

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parameters are very subjective and require interdisciplinary knowledge and experience. This

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is especially true for new and innovative designs. In the current research the functional requirements are derived by first identifying the key stakeholders that can influence the design, and then trying to perceive their needs and requirements for the artifact. In the context

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of this paper, stakeholders are defined as those individuals, groups or other sources that can

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impose requirements on the design of the fish cage.

As alluded to, it is the underlying knowledge and experience in the various disciplines that

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provide the crucial starting point of any design. As mentioned in section 1, increasingly the

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aquaculture industry is faced with the criticism from other near-shore industries and environmental groups. The standards set by the authorities are getting stricter. Therefore, an

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important stakeholder in the designing of aquaculture cages should be the society. Here, what is referred to as the society includes the general public, environmental groups, other

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concerned industries, restrictions set by the standards and guidelines, and such ‘outer’ environmental factors as referred to as by Simon (1981) in his book of the sciences of the artificial. It is only logical to allocate the fish and the fish farmer as key stakeholders for the design of the aquaculture cage since they are the primary stakeholders that impose various requirements and constraints on the design. In the current work, fish, fish farmer and the society are identified as the three key stakeholders. Now, the functional requirements are realized by considering the demands of the cultured animal, the demands from the fish farmer in carrying out routine activities on the farm and the societal demands. This is synonymous with the purpose or goal; the character of 9

ACCEPTED MANUSCRIPT the artifact; and the environment in which the artifact performs, respectively, described by Simon (1981) as key factors in fulfillment of purpose or adaptation to a goal in creating an

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artifact.

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In many design problems, the economic and technological viability are also classified as

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functional requirements or constraints. Similarly, societal demands can easily be defined as constraints as these demands lead to guidelines, standards or regulations that cannot be

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breached in designing a system. It has to be highlighted here that in many instances it is difficult to determine some attributes as functional requirements or constraints (Suh, 1990).

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Theoretically two important characteristics that separate functional requirements and constraints are that constraints do not normally have tolerances and they do not necessarily

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have to be independent, whereas the opposite is true for functional requirements (Suh, 1990).

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In designing for emerging industries, such as aquaculture, it is important to keep an open

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mind and allow for creative ideas that could lead to innovative designs. Therefore, as opposed to general traditional design processes, here we identify the economic and technological viability and ‘societal demands’ as functional requirements, rather than constraints, to reflect

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the fact that aquaculture cage design still requires new innovative solutions and we do not want economy and technology to limit possible solutions. For example, a technology not available today or a design solution too expensive at present might be available and acquired at an economically feasible cost in the near future. In well-established industries the economic and technological viability may be considered as constraints, in order to reduce the cost from as early as in the conceptualization stage. However, when finalizing the design, a cage system should be chosen from amongst many viable solutions, based on the cost and technology at the given instance of time. This proposal of delaying the optimization of any solution based on economy and technology in the design 10

ACCEPTED MANUSCRIPT process is a rather different approach to address the issue of losing design freedom before the design knowledge is matured that is also faced in traditional engineering design and

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concurrent engineering design. In traditional engineering design this happens due to making

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important decisions in the early stages of the design, while fixing the error at the later stage

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could be financially overwhelming (Erikstad, 1996). Suh (1990)describes this as:

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“Design decisions made at the initial or upstream stages of engineering affect all subsequent outcomes. Fine-tuning of the later stages of engineering operations may often have marginal effects on the total outcome, and certainly cannot rectify the erroneous decisions made at conception; yet we often relegate the design decisions to the least experienced or the least educated of engineering professionals. The reason why this practice has lasted for so long lies in our inability to reduce design to absolute or scientific principles, rendering the educated and uneducated alike handicapped in this field.” The traditional engineering professionals posit to make efforts making these early decisions

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correct. In concurrent engineering design this is addressed by moving the ‘knowledge curve’

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to the left (see Fig. 1), as described by Mistree et al. (1991), saving valuable time and money.

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“Conceptually, it is evident from any perspective that as a design process progresses and decisions are made, the freedom to make changes as one proceeds is reduced and the knowledge about the object of design increases”. Hence, we propose that for designing

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systems in emerging industries, such as aquaculture, to delay decision making until the very late stages of the design process, allowing for multiple solutions to emerge. This can also be argued for designing systems at the research stage, as the objective then is to find a solution first, before optimizing for cost and other technical parameters.

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Fig. 1 An illustration showing that the design freedom reduces while the design knowledge increases as the design proceeds.

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Through intensive literature review, including key guiding documents (Europakommisjonen,

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2002, 2009; FAO, 1995, 1997; FEAP, 2000; Sciences, 1998) and on-going consultations (EATiP, 2011) in aquaculture development, the functional requirements attributed to each of

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the identified stakeholders are:

 The cage system should be able to provide optimum growing conditions for the fish:

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from the perspective of fish -‘fish demands’.  The cage system should be able to provide safe and easy conditions for husbandry, monitoring and management activities such as feeding, observation and maintenance: from the perspective of the fish farmer -‘fish farmer demands’.  The cage system should provide social, economic and environmental sustainability – from the society’s perspective -‘societal demands’.

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ACCEPTED MANUSCRIPT Now that the functional requirements are identified, the next step is to derive the design parameters. In line with the design principles, the functional requirements stated here are

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independent from each other and it reflects the needs and the requirements of the artifact.

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4. Design Parameters.

In design theory, the design parameters are considered as the key variables that characterize the physical entity created by the design process to fulfill the functional requirements. This

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can be done by conceiving a physical solution to satisfy the functional requirements. In the following sections each of the functional requirements is analyzed in detail to identify these

Societal Demands: the cage system should provide social and environmental sustainability.

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4.1

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parameters.

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As outlined in section 1, it is the societal demands for food fish, employment and protein that

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trigger the need for further development of aquaculture in the first place. This overwhelming demand in return leads to conflicts within different sectors of aquaculture and the adjoining industries that it tries to co-exist within a narrow strip of coast. The limited coastal area hence

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demands that the future development is moved further offshore, triggering need for new technologies for offshore cage solutions. This also allows reducing conflicts with an increasing group of society, who value coastal areas as places for holidaying and relaxing, and hence consider industrial activities as sources of disturbance and as unsightly. Societal demands are powerful and hence they need to be carefully considered in the design. History has shown that societal demands can sometime lead not only to inventions and technologies, but it also have formed basis for new sciences, such as thermodynamics and communications field (Suh, 1990).

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ACCEPTED MANUSCRIPT From another perspective, society in general is becoming increasingly aware of its mistakes of the past and finding means to reconcile their wrong doings of the past. The general public

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now accepts that it has harmed the environment and wants to take actions to be more

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responsible. These acts of reconciliation introduce the new notion of environmental

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friendliness and sustainability in fish farming and other industries. Therefore, as stressed by Ellingsen and Aanondsen (2006), it is not only the quality of fish that is important to the consumer, but also the environmental impacts of farming, processing and transport to the

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market are becoming important issues as well. As a result, environmental labeling, which

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aims to inform the consumers about the environmental performance and the sustainability of the product is becoming an important part of any design.

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Further, due to the increasing population with a large percentage living on a narrow coastal

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strip, it is understandable that conflicts will arise. Therefore, in any attempt to design a system with many interactions, an intensive stakeholder consultation should be carried out and the

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views of each stakeholder must be reflected in the design. Otherwise, the chances of the design to succeed lessen, though the design is technologically and economically very

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effective. Hence, other industries and people who share the near-shore waters play a key role in fish farm designing. Most of the societal needs finally lead to design standards, guidelines or regulations. However, when designing for a dynamic environment with sentimental needs from the society becoming ever more important, the designer should not only limit the design to these standards and regulations, but the design should have the capacity to surpass such restrictions. In gaining market access, a design solution with more environmentally friendly features may win over equally effective designs, technologically and economically. As Ellingsen et al. (2009) described, consumer preference works as a ‘court of justice’, leading to increased 14

ACCEPTED MANUSCRIPT market share for the products produced through environmental friendly products. Table 2 summarizes the key clusters in the society and identified key design parameters related to the

Consumers Environmental Groups

Fish Demands: the cage system should be able to provide optimum growing

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conditions for the fish.

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PARAMETERS Food fish, income opportunity Visual pollution, smell, space Space, negative perception Environmentally friendly, sustainable, affordable, ethical & quality product Nutrition enrichment, benthic impact, habitat destruction, fish escape, chemical pollution

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FACTOR General Population Coastal Communities Other Industries

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Summary of design parameters related to ‘societal demands’.

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Table 2

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societal demands.

The fish demands the best possible environment for growth. The cultured animal demands

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water of good quality. Though the exact requirement is in general species-dependant, the temperature, salinity, dissolved oxygen (DO), pH, turbidity, pollution, eutrophication and

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diseases, amongst many others are all important parameters required for optimal fish growth. The optimal levels of these parameters are not known for many species, but based on available knowledge and experience non-lethal levels have been identified (Pillay, 2004). Optimum temperature and salinity is critical for fish welfare. Fish and other aquatic organisms have no means of controlling body temperature. A rise in temperature will result in increased metabolic rate and lead to a simultaneous increase in oxygen consumption and activity as well as production of ammonia and carbon dioxide (Beveridge, 1996). The salinity impacts the ionic balance of aquatic animals (Beveridge, 1996). Slightly outside the required temperature and salinity of a given species, the farmed animal can be subjected to unnecessary stress (Kuo 15

ACCEPTED MANUSCRIPT and Beveridge, 1990; Rudi and E.Dragsund, 1993), which in turn adversely impact the feeding, food conversion and growth.

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Other important parameters that have to be considered are the net volume and water

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conditions. A good design should provide enough net volume during a strong current. Net

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deflection, net fouling, depth of the net, size and shape of the net and the water movement are important parameters to be considered for the welfare of the fish and for the optimum fish

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growth. The severe environmental condition generally found in the offshore waters, if not dispersed effectively, can not only be detrimental for the fish growth but also could be lethal.

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Table 3 outlines a summary of ‘fish demands’, which are mostly grouped in either biological or physical parameters.

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Summary of design parameters related to ‘fish demands’. FACTOR

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Good Water Quality

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Table 3

Stocking Density

Feed Conversion

4.3

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Less Motion Smaller Net Deflection

PARAMETERS DO, salinity, temperature, pH, turbidity, pollution, infestation Net volume, DO Motion, stocking density, feeding frequency, feed type Waves, current, wind, cage design Waves, current, cage design

Fish Farmer Demands: the cage system should be able to provide safe and easy conditions for husbandry, monitoring and management activities such as feeding, observation and maintenance.

Major limitations for fish farm designs arise from the limitation to satisfy the ‘fish farmer demands’ (Rudi and E.Dragsund, 1993). The main hindrance in this regard may well be the reluctance on the part of the farmer to opt for new technologies. Most of the offshore cage designs often borrow or extend characteristic features from the near-shore or on-shore fish farming experiences. This limits the available solutions for designing cage systems that can suffice offshore waters. Hence, there is a need to borrow knowledge from other marine or 16

ACCEPTED MANUSCRIPT offshore industries. “Offshore fish production needs technology more akin to offshore oil production than to that developed by the current aquaculture industry”(Colbourne, 2005). In

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any case, a good design should allow easy and safe normal operations on the cage such as

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feeding, surveillance, sorting, inspection and maintenance. Access to the farm for husbandry

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purposes is hence very important to consider in the design of an offshore fish farm as it could influence the practical running and economic feasibility of the whole fish farming operation.

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Feeding and dead fish collection is a daily routine, which in general is carried out manually in conventional fish farming. The development in the technology of computer controlled

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automatic feeding systems (Fullerton et al., 2004) and dead fish collection methods that are employed today increase the ability to overcome the need to visit the farm daily. Net cleaning

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technologies, such as robotic net cleaning systems, helps to overcome the need for labor

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intensive net changing operations for the purpose of removing the biofouling on the net. New net materials such and copper alloy nets that are proposed today further enhance the potential

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for offshore farming (Powell and Stillman, 2009). Treatment of the fish from diseases and malnourishment, and visual observation of the cage

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and the fish are important husbandry activities that require the farmer to access the cage routinely. The technological advancements on various areas of the fish farming operation and the availability of bigger and more sophisticated support vessels, for e.g. (Bridger and Goudey, 2002), help to overcome the limitations on access to the cage. The ‘fish farmer demands’ can be summarized to parameters required to the practical requirements of a successful aquaculture operation (see Table 4). Table 4

Summary of physical parameters related to ‘fish farmer demands’. FACTOR Feeding

PARAMETERS Feeding system, Technology, accessibility

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ACCEPTED MANUSCRIPT

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Treatment method, accessibility Acoustic and imagery devices, accessibility Accessibility, material Accessibility, Mechanism Accessibility Accessibility

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Treatment Monitoring Maintenance Dead Fish Collection Sorting Harvesting

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The resulting design should be able to provide safe and easy access for routine operational activities, or what has been here referred to as the ‘fish farmer demands’, for the designed operational environmental conditions. An important point to highlight here is that the access

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to fish farm for the husbandry activities does not necessarily mean that the fish farmer has to

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physically be present on the cage system. Access can also be by means of robotic or inbuilt automatic systems. In either case, if the ‘down-time’ of the system is more than the period

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required to carry out the ‘fish farmer demands’, the site (Rudi and E.Dragsund, 1993) or the

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design is not good enough, even if the system can survive the predicted maximum storm

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forces. 5. Design Synthesis

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Design synthesis is bringing the different parts together to create something tangible. As design is a recursive process, synthesis appears repeatedly throughout a design, where one moves from a more abstract representation to a more refined one (Westerberg, 1989). Some claim that design is essentially a process of creative mental synthesis (Kokotovich and Purcell, 2000). In this line of thinking, Lawson (2006), in his book writes that, “design involves a highly organized mental process capable of manipulating many kinds of information, blending them all into a coherent set of ideas and finally generating some realization of those ideas”. For this reason, synthesis is represented as an all-encompassing factor in the proposed conceptual framework in Fig. 2. Synthesis provides a means to focus on the general task while working on the individual steps, without which, there is a great risk of 18

ACCEPTED MANUSCRIPT reaching an overall solution, despite the optimization of individual steps (Pahl and Beitz, 1999). In the current work, synthesis has been done within and in between each step.

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5.1 Conceptual framework for designing fish cages.

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Reflected in the discussion of previous sections, the framework requires first identifying the key stakeholders and perceiving their needs and requirements as the functional requirements. The design parameters are then those that best fulfill the functional

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requirements in the physical space. The resulting design concept of the cage system, therefore, demands some inherent attributes (‘fish farm demands’), such as the

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characteristics required to withstand the environment. Economic and technological viability is emphasized as criteria for optimization because they are not considered as

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constraints. Additional optimization or synthesis should also be carried out within the

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creative and trade space, based on different optimization parameters for different type of

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fish, environment and demands of the other stakeholders. Knowledge and synthesis are used within and in between each step and hence they are placed on the outer circle of the framework (see Fig. 2), suggesting that the whole process is molded by them. The two-

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way arrows in the framework suggest the iterative nature of the design and refinement process, depending on the knowledge gained with time.

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Fig. 2 A conceptual framework to design an optimum fish cage.

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A concept for fish cage designing.

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5.2

By summarizing with the use of conceptual framework, this section outlines a concept for fish

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cage designing. It is the demand of the society that creates the need for further development of aquaculture. Societal demands also suggest that the cages should be located further offshore to

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avoid conflicts, socially and environmentally. Therefore, further expanding the aquaculture production and moving further offshore are complementary to each other due to the limitations to expand further in near-shore waters. So a key question is, how does society make productive use through sustainable farming of the 90% of the world’s ocean space that does not currently contribute significantly to world seafood production (Corbin, 2007)? Now, if the demands of the fish are considered, these demands lead to selecting a site with the biological conditions optimal for the growth of cultured fish. Near-shore areas, compared to offshore areas, are more susceptible for unstable conditions due to influences from the shore, such as run-off from rivers and industrial facilities. Parameters related to the quality of water, 20

ACCEPTED MANUSCRIPT such as diseases, oxygen content and pollution from the fish farm, are in general better off at offshore sites due to the increase of water exchange at these sites. In general, offshore waters

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provide better and more stable conditions for the optimal growth of fish.

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Cleaner offshore waters in general can avoid strong tidal currents, problems related to

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assimilation of organic waste and chemicals (Pogoda et al., 2011), and limitation on the depth compared to near-shore waters. However, offshore sites can also be subjected to excess

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growth of phytoplankton, where a large amount of dissolved inorganic nitrogen from the fish farm is released into stratified surface waters (Gowen and Edwards, 1990). Though the tidal

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currents in offshore sites are smaller in magnitude, the resultant current can generally be stronger in offshore locations (Gowen and Edwards, 1990). Stronger wave conditions found in

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offshore waters could result in seasickness of the fish in shallower cages as the water

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particles under a wave follow in a circular orbit and the fish is subjected to this motion (Helling et al., 2003). In fact, it has been documented that fish, like salmon, avoid the

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energetic surface layer during stormy weather and dive deep into the cage (Anras et al., 1999), reducing the effective volume of the cage. In fact this behavioral response is so strong that it

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overrides vertical distribution towards other favorable environmental variables such as temperature and light (Oppedal et al., 2011). The stronger water exchange could also reduce the feed conversion ratio as the feed may drift out of the cage before being consumed by the fish. The turbulent water associated with the adverse weather conditions could also reduce the visibility and hence, negatively impact the feed conversion ratio. Therefore, dissipating, reflecting or avoiding the adverse weather conditions should be carefully considered in the design for fish cages. This is especially important in offshore designs.

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ACCEPTED MANUSCRIPT The biological parameters have very little to do with the design of the cage per se. However, the selected site will overwhelmingly influence the biological characteristics and the physical

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design. The environmental conditions of the selected site dictate the forces that the cage

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system has to cope with. The other important parameter from ‘fish demands’ is the fish

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welfare. This factor directly leads to physical attributes of the design of the system. While the biological factors in ‘fish demands’ signify the need to move the cages further offshore, the physical factors signify the need to stay as close to the shore as possible or incorporation of

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design attributes to effectively cater for the strong environmental forces. This is assuming that

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in general offshore waters have better biological conditions for the fish and the near-shore waters are less severe in terms of environmental forces. In conjunction with the key outcome from ‘societal demands’ to move further offshore, the solution is to find a way to effectively

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function in the conditions found in the offshore waters. The demands of the fish farmer can be summarized to easy and safe access to the fish farm,

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and the technology available to carry out the routine husbandry tasks. The current practices favor the farm system to be placed in calmer near-shore environments. However, as outlined

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in section 4.3 the access to the farm does not necessarily require the farmer to be physically present at the farm every day, but other technological means can be used to carry out the husbandry tasks. In fact, eliminating the need for the farmer to be physically in a hazardous environment may be the safest and cheapest solution. Therefore, the challenge is to find engineering solutions at an affordable cost to cater the demands of the fish farmer. The fish farmer demands will also influence the physical attribute of the cage system. For example, depending on the technology available the cage can be designed to be automatically fed. Hence, the fish farmer demands and available technology to fulfill those demands put some conditions on the ‘fish farm demands’. 22

ACCEPTED MANUSCRIPT Therefore, conceptually the optimum design is a cage system placed in offshore waters with optimum biological conditions that provides the best structural integrity to cope with severe

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environmental forces and with the ability to allow safe and effective husbandry tasks. But also

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equally important is the welfare of the fish. Hence, the design must not only be robust enough

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to survive the strong environmental forces, but, it should have means to avoid or dissipate the excess energy to provide a stable environment for the fish to grow. Therefore, from a designing point of view, the challenge for the designer is to design a system that copes best

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with the environmental forces. This can be by avoiding/dissipating and withstanding the

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forces or using a combination of these concepts, but at an affordable price, technologically and economically.

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6. Conclusion

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Application of design theory and principles to derive a conceptual framework for the design

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of fish cages resulted in a design process that is different from traditional engineering design processes. The framework allows harnessing the increase in design knowledge with the time,

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while keeping the design freedom wide open until the very late stages of the design process. With the rate of increasing population and the uncertainty in the capacity of wild fish stocks fulfilling the food, social and economic demands, the need to overcome the challenges of fish farming in the open ocean is pressing. The ‘societal demands’ require the fish farms to be placed further offshore. The ‘fish demands’ also suggest that moving offshore with the ability to effectively cater for environmental forces is more desirable. The ‘fish farmer demands’ does not necessarily contradict moving offshore, if reliable engineering solutions are sought for husbandry tasks.

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ACCEPTED MANUSCRIPT Therefore, a viable solution for aquaculture development is a robust offshore cage system designed for optimal operation and welfare for the fish farmer and fish, respectively.

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Instead of trying to extend the onshore and near-shore fish farm designs and technology to

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adapt to offshore sites, ideas should be borrowed from more developed and advanced

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knowledge from offshore and marine industry (Colbourne, 2005). Perhaps, this will allow designers to come up with more effective designs that achieve market acceptance. The knowledge and experience from the onshore and near-shore fish farming is necessary, but ‘ we

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need to drop our land bound conveniences’ (Loverich and Croker, 1993) and ‘become more

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than mariners who travel on the sea or fishermen who extract from it’ (Loverich and Croker,

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1993) to perceive designs capable for offshore fish farming.

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ACCEPTED MANUSCRIPT Acknowledgements This work stemmed out of a Ph.D. course, MR8100-Theory of Marine Design, by Professor

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Stein Ove Erikstad, given at the Department of Marine Technology, Trondheim, NTNU.

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Therefore we would like to thank Professor Stein Ove Erikstad for providing feedback on

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different aspects of design principles applied in this paper. Further, we are grateful for the insight provided by Professor Stian Erichsen, by giving feedback to the initial draft of the paper. We would also like to thank the two anonymous reviewers and the journal editor for

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providing constructive feedbacks, which helped to improve the quality of the paper

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considerably

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ACCEPTED MANUSCRIPT Research Highlights

There is an overwhelming demand for aquaculture expansion.

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Fish, fish farmer and societal groups with a stake are found to be key stakeholders.

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Economical and technological viability is taken as functional requirements.

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Optimum design is a robust offshore system allowing husbandry tasks and effective waste management.

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Design should also consider characteristics for fish welfare.

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