Climate change and salmon aquaculture in the Gulf of Maine/Bay of Fundy: some implications

Inka Milewski, Conservation Council of New Brunswick, 180 St. John Street, Fredericton, New Brunswick, Canada, E3B 4A9, e-mail: milewski@nbnet.nb.ca

Introduction

Marine aquaculture in the Gulf of Maine/Bay of Fundy takes place mainly in sheltered areas of the coastal zone which include habitats such as estuaries, salt marshes and mud flats. These habitat also provide temporary or permanent homes for a large number of commercially important animal species such as clams, oysters, lobsters, scallops, salmon, pollock, flounder, herring, and haddock, as well as plants such as kelp and rockweed. Seventy-five percent of commercial fish landings in the United States take place in coastal waters (Chambers 1992). Coastal areas, particularly estuaries, are areas of high biological productivity and provide the ecological foundation for many other non-commercial species such as birds, invertebrates (including plankton) and marine mammals.

It is in these coastal areas where the impacts of climate change - temperature and salinity shifts, storm frequencies, wave action, sea level rise, etc. - will be most evident. Changes in water temperature are likely to have physiological (e.g., growth, health, reproduction) and ecological (e.g., energy flows, migration, competition, predation) impacts on wild and farmed species. However, it has been predicted that aquaculture, particularly at mid to high latitudes, will likely benefit (e.g. longer growing seasons, lower natural winter mortality, and faster growth rates) from global climate change (IPCC 1998; Anonymous 2000; Trodaec 2000). This prediction is based on the assumption that one of the effects of climate change will be a warming trend in ocean temperatures, particularly coastal areas.

Currently, Atlantic salmon (Salmo salar) is the principal marine finfish species farmed in the Gulf of Maine/Bay of Fundy region. The estimated value of farmed salmon in Maine in 1998 was $64.6 million (US) and in New Brunswick, in 2001, the value was $190 million (CND) (USDA 1998; NBDFA 2002). Other marine finfish under experimental cultivation include winter flounder, haddock, Atlantic halibut, sturgeon and cod. Shellfish (e.g., blue mussels and oysters) are also farmed and their harvest values represent less than 5% of the total value of the aquaculture industry in Maine and New Brunswick (USDA 1998; NBDAFA 2002). There is growing interest in both Canada and the U.S. in cultivating scallops.

This paper is one of a series of discussion papers or "white papers" prepared for a symposium held on April 5, 2002 at the College of the Atlantic, Bar Harbor (Maine). The purpose of the symposium was to examine the potential impacts of climate change for marine resource management in the Gulf of Maine. This paper examines some of the implications of climate change for aquaculture development, specifically salmon farming. The paper begins with a short history of the salmon aquaculture industry in Maine and New Brunswick. It is followed by a brief review of the main activities associated with the marine phase of salmon aquaculture production, the potential impact of these activities on the coastal environment, and the implications of climate change for salmon aquaculture. The paper concludes with some thoughts on coastal resource management in response to the impacts of climate change.

Salmon aquaculture in the Gulf of Maine/Bay of Fundy

Salmon farming in the Gulf of Maine/Bay of Fundy region is focused in southwestern New Brunswick and northeastern Maine. In the Bay of Fundy, the first commercial salmon smolt were placed in sea cages in Lord’s Cove, Deer Island (New Brunswick), in 1978. These smolts represented the earliest attempt at salmon farming in the Gulf of Maine/Bay of Fundy. Eighteen months later, they were harvested as adult salmon and sold for $46,000 (CND), demonstrating that salmon farming was possible in this region. By the late 1980's, there were 49 farms producing almost 4,000 mt of farmed salmon in southwest New Brunswick (Table 1).

In the mid 1990's, the price per pound paid to farmers had dropped by almost a half, from a high of $6.35 per pound in 1987 to $3.50 a pound in 1995. The

Table 1. Salmon farming in New Brunswick, 1979-2001. Source: DFO 1999; NB Department of Agriculture, Fisheries and Aquaculture 2002.

Year No. of Farms Production (mt)

1979 1 6

1981 2 24

1983 4 72

1985 18 399

1987 33 1,561

1989 49 3,993

1991 57 8,509

1993 67 10,484

1995 71 14,490

1997 91 20,310

1999 90 22,000

2001 94 40,000 (est)

number of new farms coming into production and the volume of salmon being produced was slowing down. Over the next six years (1990-1996), the industry was hit with lower prices, increased production from foreign producers, disease outbreaks and intense competition for farm sites (Milewski et al. 1997). These factors resulted in a concentration and intensification of the industry where fewer companies were producing more and more salmon. The average number of fish per site in 1997 was 70,000. Today, this number is 200,000 to 300,000 fish per farm, and 94 farms are licensed in New Brunswick.

In Maine, salmon farming takes place principally in Cobscook Bay, but the industry has expanded into other areas along the coast. The first commercial Atlantic salmon farm began In Cobscook Bay in 1982 and the first harvest of 20 mt occurred in 1984 (Baum 1998). By 1996, there were 50 leases covering 860 acres, 563 of which were in Cobscook Bay (Alden 1997). Annual harvest of farmed salmon in Maine now exceeds 12,000 mt (over 33 farm sites) with 90 percent of this production taking place within 50 km of the Canadian border and about 60 percent in close proximity to the New Brunswick industry (Baum 1998; DFO 1999).

Although significant federal, state and provincial government funding is available to scientific institutions and industry organizations for research and development of new species, Atlantic salmon will likely remain the main finfish species farmed in the Gulf of Maine for at least the next decade. According to Muir and Young (1998), many marine species still require at least 5 to 10 years of focused and sustained development before new species can occupy a significant niche in the market. Some industry and scientific analysts are also suggesting that it is more sensible to concentrate development effort and scientific research on a relatively few species than diluting effort amongst more and more species (Muir and Young 1998; New 1999).

Potential impacts of salmon aquaculture on the coastal environment

The global production of farmed Atlantic salmon (Salmo salar) has risen dramatically in the past decade. In 1990, world-wide production was 225,492 metric tonnes (mt) and the total production for 2001 was estimated at 940,000 mt (Roberts 2001). By the year 2010, world-wide production of farmed salmon is estimated to reach almost 2,000,000 mt (IntraFish 1999). Not only has production increased, but the intensity of salmon aquaculture has also increased. In the 1970's and 1980's, salmon farms were raising tens of thousands of fish per farm and farms were generally scattered over a large geographic area. Today, a single salmon farm can cover many hectares of coastal area and raise hundreds of thousands of fish per farm site. World-wide production has also increased due to the introduction of various salmon species to countries (e.g., Australia and Chile) and regions of countries (e.g., west coast of Canada and the United States) where the species did not exist naturally ( Thomson and McKinnell 1997; Reilly et al. 1999; Winkler et al. 1999).

Almost all farmed salmon production takes place in sheltered areas of the coastal zone. These areas provide protection from heavy seas, suitable year-round temperature and, depending on the location, some tidal flushing (Saunders 1995). Coastal sites also provide salmon growers with convenient and inexpensive access to their grow-out sites. New technologies and production techniques have allowed the salmon aquaculture industry to expand into previously undeveloped sites such as offshore and more wave-exposed areas (Rosenthal et al. 1995). Space limitations and environmental problems such as disease outbreaks have forced some producers into new areas that may be marginal for salmon farming, ecologically sensitive, or in conflict with traditional uses of the area (Millar and Aiken 1995; Cripps and Kelly 1996; Muir 1996).

Along with the rise in salmon production, there has been an increase in public and scientific concern about the environmental impact of salmon aquaculture. This concern has led to increased research which in turn has led industry to make improvements in feed quality, feeding control and husbandry practices. Food conversion ratios (the weight of food fed: biomass of fish produced) have dropped, the dietary levels of nitrogen and phosphorus levels have decreased, and the use of antibiotics has dropped 90% per unit weight (Beveridge et al. 1997). The benefits gained from these improvements may have been offset by the overall increases in the number of fish farms and fish production. For example, the waste discharges from individual farms may have decreased but the number of farms and the number of fish per farm has increased. The result is a net increase in waste discharges. Furthermore, the ability to improve feeding efficiencies and food conversion ratios may have peaked and there may be considerably less room for reduction of waste outputs in the future (Beveridge et al. 1997; Burd 1997).

The number of scientific and industry reports that have been published on the impacts of various activities associated with marine finfish, specifically salmon, aquaculture on the coastal environment is extensive. A search of the Aquatic Sciences and Fisheries Abstracts (ASFA) reveals that between 1990 and 2000 there were over 1000 scientific publications on the environmental impacts of salmon aquaculture on the marine environment. Many of these studies have been reported and summarized in numerous academic, governmental, and non-governmental reviews such as Baird et al. (1996), Ellis (1996), GESAMP (1997), Goldburg and Triplett (1997), ICES (1999), Black (2001), Tlusty et al. (2001) and Wildish and Héral (2001).

Table 2 identifies the main activities associated with the marine phase of salmon aquaculture production, the pathways or connections to the environment of the various activities and the potential effects of these activities on the environment and its associated wildlife. The information in the table was compiled based on a review of the scientific literature of the past ten years. The table identifies potential interactions only and makes no assumptions about the degree or magnitude of the impacts to the environment. The magnitude of an impact will depend on many factors such as the scale and duration of the activity, the biological and oceanographic setting in which the activity takes place, and the combined effect of other past, existing and imminent activities in the area. Ultimately, the determination as to whether environmental impacts will occur can only be addressed through some type of comprehensive environmental impact assessment process.

Table 2. Major activities associated with the marine phase of salmon aquaculture and their potential effect on the coastal environment and its wildlife (from Milewski 2001).

Activity

Pathway

Potential Effect

net pens

fish feed

therapeutants and chemicals

- siting and physical structure

- lights

- predator control using firearms

- noise generated by acoustic

harassment devices (AHDs)

- fish escapement

- release of uneaten food and

faeces

- release of nitrogen and

phosphorus

- antibiotics

- pesticides

- disinfectants and anti-foulants

- direct mortality through entanglement

- behavioural changes in coastal pelagic fishes, birds and marine mammals

(e.g., avoidance)

- loss of habitat for pelagic species

- shifts in plankton communities in response to photoperiod changes

- behavioural changes in fishes, birds and marine mammals

- direct mortality

- behavioural changes in invertebrates, fishes, birds, and marine mammals

(e.g., avoidance)

- loss of habitat created by acoustic exclusion zones

- interference with communication signals

- temporary hearing loss or permanent hearing damage

- disease transmission to other species

- genetic interactions with wild salmon

- displacement of wild salmon and other fishes from natural habitat (e.g., through

competition, predation)

- suffocation and displacement of benthic organisms

- loss of foraging, spawning and/or nursery habitat for wild species

- loss of biodiversity

- fragmentation of benthic habitat

- inter-ecosystem costs (e.g., forage fishery)

- change in water quality

- mortality of plankton (including fish and invertebrate egg and larvae)

- increased primary productivity

- shift in plankton community composition

- increase in harmful algal blooms

- alteration of coastal food webs

- tainting of wild species

- changes in benthic bacterial community

- direct mortality and sublethal effects

- tainting of wild species

- behavioural changes in mobile invertebrates

and fishes

- direct mortality and sublethal effects

- tainting of wild species

- behavioural changes

Despite extensive scientific research on the impacts of salmon aquaculture on the marine environment, there are still many gaps in our knowledge. For example, very little research has been done on the impacts of acoustic exclusions zones created by AHDs on marine mammals and fishes (e.g., displacement from traditional feeding, nursery, or refuge areas), pathogenicity of infectious agents transmitted from farmed salmon to wild non-salmonid fishes or invertebrates, impacts of nitrogen and phosphorus loading from aquaculture on harmful algal blooms (HABs) or phytoplankton community composition, and the impacts of the long-term sequential use of pesticides on non-target species and subsequent population- or community-level impacts (Milewski 2001). At the same time, it is widely acknowledged that salmon aquaculture can: 1) contribute to coastal nutrient pollution; 2) result in the release of toxic compounds; and 3) interfere with the performance of existing wild salmonid stocks (Bugden et al. 2001; Ernst 2001; Haya et al. 2001; Hindar 2001).

Some implications of climate change on salmon aquaculture

Temperature changes, increased precipitation and sea level rise have been identified as key scenarios arising from global warming trends. These conditions will likely give rise to changes in salinity, dissolved oxygen, variations in storminess and wave action, water depth, turbidity and ice in coastal areas. In turn, these oceanographic changes will have a wide range of physiological and ecological impacts on biological communities, as well as operational impacts on aquacultural operations. Table 3 presents a checklist of some oceanographic variables influenced by climatic changes that will likely have physiological, ecological and operational impacts on salmon aquaculture.

Table 3. Checklist of some oceanographic variables likely to

have an impact on salmon aquaculture. (Adapted

from Page and Robinson,1997)

Oceanographic Variables

Physiological Impacts

(e.g., growth, development, reproduction, disease)

Ecological Impacts

(e.g., organic and inorganic cycles, predation, parasitism)

Operational Impacts

(e.g., siting, feed quality/ availability, sea cages technology)

temperature

salinity

dissolved oxygen

water currents

waves

ice

water depth

turbidity

For example, temperature changes could increase the frequency of harmful algal bloom responsible for massive fish kills and shellfish poisoning. Changes in wind velocity could affect flushing rates. A decrease in flushing could lead to decreased oxygen levels, reduced food availability for shellfish, and increased accumulation of waste beneath net pens. As for food quality and availability, most farmed marine finfish species depend on wild fish converted to fish meal and fish oil as their principle food source. Any large-scale global reduction (as a result of climate change) in fisheries that supply the raw materials for fish feed manufacturers (e.g., herring, capelin, anchovies, etc) could likely affect the cost and future of aquaculture development.

Like most livestock operations, however, farmed aquatic species are grown and harvested under conditions that, for the most part, are controlled by the livestock owner. Net pens and shellfish collectors, rafts or lines can be moved from site to site in response to changing environmental conditions. Warming trends, as well as improvement in net pen technology, may allow aquaculture sites to expand into regions previously unsuitable because either sea temperatures were too cold or there was a presence of ice (Drinkwater 1997; Page and Robinson 1997; New 1999). According to Hicks (2000), "farmed fish are not nearly as sensitive to [temperature changes or ocean circulation] because the farmer can modify the temperature of the water the fish are being reared in and supply the fish with alternate food supplies. The farmer is able to exploit the changes that are expected from global warming. The farmer can take advantage of warmer water to grow fish more quickly and increase the variety of fish they produce".

In addition, genetic manipulation through natural breeding programs or genetic engineering can be used to increase growth rates, improve disease resistance, broaden the environmental range within which species can be cultured and create new products (New 1999). Disease and pest outbreaks can also be treated with a wide variety of chemotherapeutants. While the raw materials for fish feed manufacturers may be a constraint in the short term, the aquaculture industry is actively developing fish feeds that will use proteins produced from grains and oilseeds, rendered products and seafood processing waste (Hardy 2000).

Conclusion

Climate change will pose challenges for the aquaculture industry and other coastal marine resources and users. As this brief review illustrates, the operational flexibility inherent in livestock operations may give the aquaculture industry a production advantage over wild fisheries. A wide range of technological (e.g., genetic engineering, recirculation and off-shore grow-out systems, etc.) and management (e.g., application of vaccines and other chemotherapeutants, changing feed formulations, site selection, etc) solutions can be used to protect farmed fish from many of the environmental impacts resulting from climate change. Wild fishes must rely on natural adaptation and selection which occur over very long time scales.

The coastal zone, where much of aquaculture currently takes place, however, is already under tremendous development pressure and it is unlikely to diminish with the anticipated impacts of climate change. Expanding coastal population growth, pollution, oil and gas exploration, sand and gravel mining, fishing, recreational and tourism developments and, more recently, aquaculture are already exacting a toll on marine coastal ecosystems. The prospect of more development, as is projected, in coastal areas does not bode well for marine resources or biodiversity.

The depletion and degradation of coastal ecosystems have not gone unnoticed by fishermen, scientists, coastal residents and policy makers. A new approach to coastal resource management - integrated coastal management (ICM) - is being widely discussed (see review by Donnan 2001). The aim of ICM would be to co-ordinate and manage human activities in coastal areas with a view to ensuring the sustainability of marine resources. An unstated assumption of the ICM process is that all development activities have equal access and right to marine resources. Although there has been a proliferation of ICM initiatives around the world in the past decade, there are relatively few examples where ICM is actually being implemented (Doonan 2001).

Given the declining state of marine and global natural resources, marine resource management must become more restoration-oriented rather than development-oriented, as implied by the ICM approach. Under a restoration focus, coastal management decisions would be guided by three factors: 1) scale; 2) baselines; and 3) ecological consideration. Scale refers to the level at which scientific information is gathered. Data must be gathered at the appropriate ecological, geographical and human units of management. These units of management are community, ecosystem and seascape levels. This factor gives recognition to the fact that local ecosystems are unique and that extrapolating across large regions is, and has proven to be, risky. It also recognizes that all ecosystems are connected and that local actions can have major effects on other or larger regions up to the global level.

Baselines refer to historical relationships - both human and ecological. It is possible to reconstruct ecological food webs to pre-industrial times. These historic reconstruction provide a useful base from which to measure how humans have modified species composition, dominance patterns and food-web structure and they can be used to direct the restoration of ecosystems and economies.

Finally, ecological consideration include such basic components as trophic relationships, energy flows, carrying capacity and assimilative capacity. Neglecting ecological considerations in management has resulted in natural constraints to growth and, at the same time, to a deterioration of the environment in which the development is located. The need to determine the natural capacity of an estuary or bay without diminishing its ecological integrity should outweigh the need to meet artificial allocation or production targets.

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