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Sedimentation rates were measured on gravity cores collected near finfish cages in Lime Kiln Bay, N.B. in the Western Bay of Fundy using the radionuclide tracers Pb and Cs. Sediment cores collected close to aquaculture sites that have undergone extensive salmon fish farm activity over the past 20 years exhibit elevated levels of Zn and Cu in the upper 50 cm of the cores. Sediment geochronologies indicate that the threshold horizons for elevated Zn and Cu levels conform to the initial introduction of fish farms into Lime Kiln Bay in 1981. The source of the Zn is the fish feed while Cu is associated with chemical agents used to reduce fouling of the cages by marine biota. The highest contaminant levels for Zn (>250 μg g) and Cu (>70 μg g) were measured in sediment cores collected within the “footprint” of previously abandoned sites. The contaminant signals decrease with increasing distance away from the cages to values approaching background levels at distances greater than 200 m from the original cage locations. Zn and Cu concentrations have remained elevated in sediments for the five-year period between the removal of the cages and the date of core collection, suggesting that remobilization of these metals from sediments following the termination of aquaculture operations may be minimal. P is present at elevated levels in sediments close to aquaculture sites because it is an important constituent of marine organic material associated with fish feed pellets and fish farm wastes. Elevated Cd, Mo and U levels were also observed in sediments deposited under salmon cages during past periods of aquaculture operations. These elements are soluble in seawater, but can be authigenically precipitated in sediments under reducing conditions. In the present study they have been used as indirect tracers of fish farm activities owing to their transfer from seawater to sediments under the anoxic sediment conditions generated by the high sediment flux of reactive organic material from aquaculture operations.

The formation and deposition of large, fast-sinking aggregates by flocculation governs the distribution of fine particulate material within the coastal zone. Three major factors control the development of a flocculated suspension: (1) particle number or concentration, (2) particle adhesion efficiency or stickiness, and (3) particle break-up, most often due to an applied shear. The steady state equilibrium size distribution of a flocculated suspension reflects a dynamic balance between particle aggregation and disaggregation; changes to concentration, composition, or turbulence can hence affect the distribution of fine particulate material, both inorganic and organic. Owing to the close association of many surface-active contaminants with flocs, the aggregation dynamics of the particulate material will strongly influence their fate. The introduction of waste feed, faecal material, and their resulting degradation products from open cage aquaculture operations in the coastal zone will potentially increase both particle concentration and particle stickiness. As a result, the natural flocculation and depositional equilibrium of an inlet can shift towards increased deposition of fine-grained particulate material within flocs and the sequestering of contaminants within the sediment. Evidence for such a shift in fine-sediment dynamics and contaminant transport has been found in the Western Isles region of New Brunswick.

A study was conducted in the Bay of Fundy, Canada in 2000–2003 to examine the effects of -dominated algal mats on the population dynamics of the soft-shell clam () and the possible role of Atlantic salmon farming in this interaction. A far-field linkage of the salmon farms to the intertidal zone was determined by the use of zinc:lithium tracers. A combination of laboratory and field-based experiments were conducted to assess the effects of algal mats on the recruitment, production (growth and survival) and behaviour of the clams. The results indicated that increased zinc concentrations were found in intertidal sediments located >1 km from the nearest salmon site. This implies that if the fine particulates from the salmon site were being transported that distance, then the dissolved fraction could also travel that far, providing it was not absorbed by other nutrient sinks along the way. The algal mats were found to negatively affect clam recruitment and behaviour. The experimental results were not as clear for negative effects on biological production, but growth was found to be lower than expected and survival on the beach was low. The economic cost of the eutrophication to the beaches might be substantial (estimated >100000 $CAD per clam beach). One solution would be an integrated culture philosophy where additional crops are intentionally grown and harvested so that a potential liability could become an asset to the marine coastal economy.

We present a review of the benthic macrofaunal changes that are circumstantially linked to intensive marine finfish aquaculture, or mariculture. The community structural and functional changes of macrofauna identified are mostly near-field effects, limited to the farm cage footprint. In common with other organic enrichment events in sediments, the mechanism in mariculture-related macrofaunal change is primarily caused by death due to hypoxia in sediments, followed by re-colonization with specialized organic enrichment tolerant macrofauna. Despite recent attention to the field of mariculture ecology, much still remains to be done to fully understand and manage the ecosystem effects of this activity. In the second part of this chapter we present a case history study from a marine tidal inlet (L'Etang) in the Bay of Fundy, Canada during a period of rapid industrialization, dominated first by pulp mill effluents in the 1970s, and then by salmon mariculture development beginning in the 1980s and continuing today. Circumstantial evidence links the temporal benthic macrofaunal changes found in L'Etang Inlet to far field organic enrichment effects, primarily resulting from pulp mill pollution in the most landward area and salmon mariculture in the seaward end. It is shown that the temporal macrofaunal changes at the seaward end are not due to hypoxia in sediments or to natural seasonal and interannual changes. A new alternative hypothesis in aquaculture ecology is proposed: that the macrofaunal changes are far field effects resulting from the increased sedimentation (quality and amount) associated with intensive mariculture.

Chemicals (sea lice therapeutants) currently authorized in North America and Europe for the treatment of sea lice infestations in cultured salmon may be classified into two major groups. The classification is based on their routes of administration, and includes bath techniques (organophosphates, pyrethroids and hydrogen peroxide) and additives in feed (avermectins, chitin synthesis inhibitors). The ecological risk posed by the use of the chemicals is reviewed and assessed in this chapter. While the biological effects of sea lice therapeutants on aquatic animals that may live near salmon culture sites have been studied under laboratory conditions, field studies on the efficacy, fate and distribution, and biological effects are limited. In general, the in-feed treatments are more convenient to administer and posed less ecological risk than the bath treatments. As an example, the approach adopted by the UK was used to assess the environmental safety of the sea lice therapeutants. It was concluded that there are considerable differences between the environmental characteristics of fish farm sites and their ability to accept discharges of sea lice treatments without giving rise to unacceptable environmental impacts. Such site-specific risks can be managed through the application of appropriate environmental quality standards for the chemicals concerned, and site-specific assessment of the maximum acceptable rate of use of the treatments.

Various antibiotics have been used over the past 20 years and continue to be registered for use in finfish aquaculture in the United Kingdom, Norway, Ireland, and Canada. These include β-lactam (Amoxicillin), macrolide (Erythromycin), phenicols (Florfenicol), quinolones (Oxolinic acid, Piromidic acid, Naladixic acid, Flumequine), fluoroquinolone (Sarafloxacin), sulphonamides (potentiated sulphonamides), and tetracyclines (Oxytetracycline). Vaccines have largely replaced antibiotics as a means for controlling bacterial pathogens in cultured finfish but these anti-microbial agents continue to be applied to control disease in both hatcheries and grow-out stock. Bacterial strains resistant to specific antibiotics used in aquaculture have been cultured from mixed microbial communities in sediments after treatments of cultured fish stocks with antibiotics cease. This chapter considers modes of action, factors affecting environmental persistence and ecological aspects of antibiotic resistance of the major antibiotics currently used in finfish aquaculture in Canada and Europe.

As net-pen aquaculture in coastal waters grows, regulatory agencies must consider the potential for localized eutrophication. To avoid excessive nutrient concentrations, Maine sees value in dispersing farms over larger regions. Often, little environmental baseline information exists in these new areas on which to base a risk assessment. This case history attempts to convey the process by which a permitting decision was made using a weight-of-evidence approach. By drawing on readily available sources of information, simple models, and basic water quality monitoring data, the effect on Blue Hill Bay by an existing salmon farm was analyzed and the potential effect of a proposed net-pen aquaculture was predicted. In the process, a range of carrying capacities was developed, depending on temporal and spatial scale. The exercise has potential value to regulatory scientists and policy makers by identifying new research, monitoring, and compliance issues. In the end, the exercise demonstrates that neither aquaculture nor carrying capacity should be viewed as static and in isolation from other stressors.

A management system for marine fish farms in Norway has recommended the use of simple electrode measurements of redox potentials (E) and pH in sediments for monitoring of environmental effects at net cage locations. In the present paper we present results of such measurements performed over 15 years at farm locations in coastal Norway. Together with other chemical analyses of sediment and pore water, the electrode measurements provided a suite of biogeochemical variables used for environmental state assessment. The impact of external control factors such as biomass, local bathymetry and current velocities on the benthic effect parameters was investigated and comparisons were made with alternative effect variables such as macrofaunal community structure. It was found that simple two-dimensional plots of pH vs. either E or pS (= − log[ΣHS]) maintained a high degree of discrimination between stations located at different distances from farm locations and provided a state assessment with high relevance to farm management. Compared to other methods, electrode measurements are cost-effective, applicable on a wide variety of benthic substrates and provide superior resolution in the high end of the organic enrichment gradient.

To be successful, environmental management must be comprehensive and take into account the activities of all participants who share that environment. In this chapter aquaculture is discussed as an activity in the marine coastal zone that not only shares the waters, but also has a particular need to maintain the quality of those waters. Emphasis is placed upon the need for an effective system of integrated coastal zone management. Environmental management problems stemming from aquaculture can be minimized by selection of the areas most suitable for culture, applying the best technology and maintaining operations at levels within the assimilative capacity of the area. The contributions of aquaculture to nutrification and pollution are presented and the need to understand their impacts is discussed. Treatment of infectious diseases among the farmed species as an integral part of a comprehensive environmental quality program is advocated. A central problem in environmental management is the lack of proven indicators of environmental quality. As the condition of the biota reflects the environmental conditions under which they live, it is considered possible to measure environmental quality by using captive and wild biota as sentinel species. These measurements can be made indirectly on whole animal or plant responses or directly through measurements of stress as revealed either by changes in blood constituents or on changing concentrations of stress proteins such as anti-microbial histone-like proteins of the skin, or from the array of heat shock proteins now better understood as stress proteins or molecular chaperones.

Environmental Risk Analysis (ERA) consisting of risk assessment, management and communication can be applied to assess ecological and environmental changes associated with industrial-scale marine finfish aquaculture development. Physical, chemical, and biological variables are identified that may be used to detect thresholds for changes in ecosystem structure and function in order to apply ERA. Changes due to predictable or unpredictable effects may be local or far field. Predictable effects such as reduced dissolved oxygen, increased nutrients and organic matter, or lower diversity of benthic fauna in the vicinity of net-pens can be modeled to quantify local impacts on water column and sediment variables. Far-field and long-term risks such as interactions of escapees with natural stocks and effects of fishing to obtain food for cultured fish are more difficult to predict and quantify. Despite this, scoring methods using single or multiple indicators may be applied to determine the degree of risk associated with all identified potentially negative effects. ERA should be part of an integrated planning approach where aquaculture development occurs within a broad framework to include all development and user groups within the coastal zone. Environmental observations and models can then be combined with effective aquaculture husbandry practices to manage environmental risks from all sources.