We have archived this page and will not be updating it.

You can use it for research or reference.

We have archived this page and will not be updating it.

You can use it for research or reference.

Language selection

Government of Canada / Gouvernement du Canada

Search

A Scientific Review of the Potential Environmental Effects of Aquaculture in Aquatic Ecosystems - Volume 1

A Scientific Review of the Potential Environmental Effects of Aquaculture in Aquatic Ecosystems - Volume I
(PDF, 123 KB)

Table of Contents

Chemical Use in Marine Finfish Aquaculture in Canada: A Review of Current Practices and Possible Environmental Effects

L.E. Burridge
Marine Environmental Sciences, Fisheries and Oceans Canada St. Andrews Biological Station, St. Andrews, New Brunswick

Executive Summary

There has been a great deal of scientific debate regarding the environmental consequences of chemical usage in aquaculture. The debate has also moved into the public domain: where views of the opposing sides are typified by several highly publicized anti-aquaculture articles and, most recently, television documentaries (Ellis 1996; Goldburg and Triplett 1997; Milewski et al. 1997), and the responses to these articles from the finfish aquaculture industry (e.g. Canadian Aquaculture Industry Alliance 2001a,b).

Scientific reviews of the subject have been prepared by Zitko (1994) and GESAMP (1997). Issues raised and recommendations made by these authors have yet to be addressed in a significant manner. In addition, the authors of recent reviews of environmental impacts of aquaculture have identified chemical inputs from aquaculture activity as an area requiring further research (Nash 2001; Anonymous 2002). Several projects recently funded by Fisheries and Oceans Canada's (DFO) Environmental Science Strategic Research Fund (ESSRF) have allowed scientists to begin to address some of these topics. However, these projects are still in the early stages of identifying sources of contamination and potential effects on the environment, particularly to non-target species.

This review is a summary of potential sources of chemical contamination, chemicals that may be involved and knowledge about the potential effects of these compounds. Each identified class of chemical contaminants could be the subject of its own comprehensive review. Pesticides, drugs, persistent organic pollutants and metals are discussed in the context of the Canadian aquaculture industry.

Two classes of compounds will not require further research. Food additives include antioxidants (preservatives) and carotenoid pigments (flesh coloring) and are unlikely to cause any effects in the environment. MS-222 (tricaine methanesulfonate) is used in the New Brunswick aquaculture industry, and no adverse environmental effects are foreseen with its use (Zitko 1994).

Chemicals used in the Canadian aquaculture industry are identified in Table 1. The table summarizes recent scientific information regarding their use, persistence and potentialeffects in the environment. There are relatively few publications in the primary literature regarding the environmental fate and effects of chemicals used in aquaculture in Canada. It is clear that a number of gaps in knowledge exist for each compound or class of compound. A more thorough review of each compound would identify further specific gaps related to that chemical.

For antibiotics, there appears to be no published data collected around Canadian aquaculture sites regarding the following: presence of antibiotics in sediments and aquatic biota; presence and prevalence of antibiotic-resistant organisms in sediments and indigenous species; or antibiotic residues in fish and non-target aquatic organisms. Accumulation of antibiotics in sediments may interfere with bacterial communities and affect mineralization of organic wastes (Stewart 1994), but no studies have been published in Canada.

Most work on pesticides to date has been conducted in the laboratory and has focused on determining the acute responses of aquatic organisms (non-target species) to exposure(s) to anti-sea lice chemicals. Limited field trials have focused on lethality of single treatments. Short-term responses to pesticide applications and long-term studies to establish the natural variability in local populations and measures of change in biodiversity need evaluation. Currently, commercially important non-target species have attracted much of the attention regarding effects of chemicals. There are apparently no data regarding the effects of these chemicals on microorganisms and planktonic species that form the foundation of the marine food chain in the near-shore environment. The chemical formulations of pesticide and disinfectant products have not been determined, and many of the 'inert' ingredients may be toxic to aquatic biota (Zitko 1994).

Little is known about the relationship between aquaculture and environmental contaminants, such as persistent organic pollutants (POPs) and metals. Feeds may be a source of contaminants to farmed fish. Knowledge of the constituents of each formulation is required for an accurate assessment of potential risk. Metals may be deposited near aquaculture sites from at least two other sources: leaching from metal cage structures and antifoulant paints. Chlorinated compounds (Hellou et al. 2000) and metal concentrations (Chou et al. 2002) were found to be higher when the total organic carbon content was high in sediments. Wooden cages with styrofoam floats may be a source of plastic contaminants (Zitko 1994). However, little known is known about the effects of plastics on aquatic organisms.

In addition, generic gaps can be identified in relation to the scientific approach and methodology:

Table 1: A Summary of Chemical Compounds Used in the Canadian Aquaculture Industry
Chemical Use Persistence in Sediment Bioaccumulation Potential Effects
Oxytetracycline Antibiotic Persistent for long periods depending on environmental factors (Björklund et al. 1990; Samuelsen 1994; Hektoen et al. 1995; Capone et al. 1996); Half-life 419 days under stagnant, anoxic conditions (Björklund et al. 1990) Uptake by oysters and crabs either in the laboratory or in close proximity to salmon cage sites (DFO 1997); Concentration in tissues of rock crabs over US FDA limit (Capone et al. 1996) Resistance to oxytetracycline may occur in fish, non-target organisms and bacterial community near aquaculture sites (Björklund et al 1991; Hansen et al. 1993; Hirvelä-Koski et al. 1994)
Tribrissen Antibiotic Estimated half-life of 90 days at 6-7 cm deep (Hektoen et al. 1995)
Romet 30 Antibiotic Uptake by oysters (Jones 1990; LeBris et al. 1995; Capone et al. 1996; Cross unpublished data)
Florfenicol Antibiotic Estimated half-life of 4.5 days (Hektoen et al. 1995)
Teflubenzuron Drug; In-feed sea lice control Solubility 19 mg·L-1 with a log Kowa of 4.3, indicating a potential to persist (Tomlin 1997); Persistence >6 months in area <100 m from treated cage (SEPA 1999b) Chitin formation inhibitor; Juvenile lobster mortalities reported (SEPA 1999b); Mitigation possible by depuration prior to molting (McHenery 1997; SEPA 1999b)
Emamectin benzoate Drug; In-feed sea lice control Solubility 5.5 mg·L-1 with log Kow of 5, indicating potential to persist (SEPA 1999b) Withdrawal period of 25 days prior to marketing salmon Chloride ion movement disruptor (Roy et al. 2000); Lethal to lobsters at 735 mg·kg-1 of food (Burridge et al. 2002); Induces molting in lobsters (Waddy et al. 2000c)
Ivermectin Drug; In-feed 'off-label' treatment for sea lice control Solubility of 4 mg·L-1 (Tomlin 1997); Could persist for 28 days (Wislocki et al. 1989; Roth et al. 1993) Withdrawal period of 180 days prior to marketing; Accumulated in lobster tissue over 10 days (Burridge, Haya and Zitko unpublished data) Chloride ion movement disruptor (Roy et al. 2000); Cumulative 80% Atlantic salmon mortality to 0.2 mg·kg-1 for 27 days (Johnson et al. 1993); 96h LC50 at 8.5 mg·kg-1 food for shrimp; NOECb was 2.6 mg·kg-1 food (Burridge and Haya 1993)
Azamethiphos Pesticide; Bath treatment for sea lice control Solubility 1.1 mg·L-1 with a log Kow of 1.05, not expected to persist (Tomlin 1997) Unlikely to accumulate in tissues (Roth et al. 1993, 1996) Neurotoxin, acetylcholinesterase (AChE) inhibitor, but not cumulative (Roth et al. 1993, 1996); Mutagenic in vitro (Committee for Veterinary Medicinal Products 1999; Zitko 2001); 1-h bath at 1 mg·L-1: lethal to 15% salmon after 24 h (Sievers et al. 1995); Larval/adult lobster 48-h LC50 at 3.57-1.39 μg·L-1 /NOEC 120 min at 1 μg·L-1 (Burridge et al. 1999a, 2000a); Behavioral responses at >10 μg·L-1 (Burridge et al. 2000a,b)
Copper-based antifouling paints Antifoulant; Reduce fouling biota on nets Elevated copper (Cu) reported in sediments (Burridge et al. 1999a) May accumulate in aquatic biota 100-150 mg(Cu)·kg-1 in sediment may affect benthic fauna diversity (Debourg et al. 1993); Most sample locations > ISQGc of 18.7 mg·kg-1, lethal to amphipods and echinoids (Burridge et al. 1999a)
Iodophors Disinfecting equipment Not expected (Zitko 1994) Formulations may contain compounds harmful or toxic to aquatic biota (Zitko 1994; Madsen et al. 1997; Ashfield et al. 1998)
Chlorine/Hypo-chlorite Disinfectant; Net cleaning Toxic to aquatic organisms (Zitko 1994)
PCBs, PAHs,p,p"-DDE Found in fish feed (Zitko 1994) PCBs not detectable at 0.05-0.10 mg·g-1 dry wt (Burridge et al. 1999a); p,p'-DDE detected at DL=1 ng·g-1, dry wt (Hellou et al. 2000) Changing lipid profiles in wild fish (Zitko 1994)
Cadmium, Lead, Copper, Zinc, Mercury From cage structures; Fish feed Copper >2, zinc 1-2 times higher in sediments below cages than in fish feed (Chou et al. 2002); Cadmium exceeded 0.7 mg·g-1 (Burridge et al. 1999a) May be toxic or accumulate in aquatic biota
Polystyrene beads Styrofoam floats Source of low molecular weight contaminants (Zitko 1994) Benthic fauna altered by altering pore water gas exchange, by ingestion or by providing habitat for opportunistic organisms (Goldberg 1997)

The table includes only compounds known to be used (presently or historically) in Canada. Other classes of compounds are used routinely in other jurisdictions and may be introduced to Canada in the future.

a – log Kow = logarithm of the octanol-water partition coefficient. It is internationally accepted that log Kow >= 3 indicates a potential to bioaccumulate. The Canadian Environmental Protection Act (CEPA) recognizes log Kow >= 5 as indicative of potential to persist and/or bioaccumulate (Beek et al. 2000).

b – NOEC = No Observed Effect Concentration

c – ISQG = Interim Sediment Quality Guidelines

The complete papers can be found in the following document:

Fisheries and Oceans Canada. 2003. A scientific review of the potential environmental effects of aquaculture in aquatic ecosystems. Volume 1. Far-field environmental effects of marine finfish aquaculture (B.T. Hargrave); Ecosystem level effects of marine bivalve aquaculture (P. Cranford, M. Dowd, J. Grant, B. Hargrave and S. McGladdery); Chemical use in marine finfish aquaculture in Canada: a review of current practices and possible environmental effects (L.E. Burridge). Can. Tech. Rep. Fish. Aquat. Sci. 2450: ix + 131 p.

REFERENCES

Date modified: