1           Introduction

This report addresses issues recently raised by the Canadian Sablefish Association (CSA) concerning the anticipated development of the sablefish aquaculture industry in British Columbia. In particular, the CSA is concerned with the potential risks associated with marine net pen sablefish grow out operations. Many of the issues raised are similar to those stemming from the ongoing debate about the impacts of salmon aquaculture in British Columbia. Detailed summaries of the environmental risks of salmon farming already exist. For example, a report by the Commissioner for Aquaculture Development (Anon., 2004) includes reviews of three recent reports: a PFRCC study on the salmon aquaculture debate in British Columbia (Gardner and Peterson, 2003); a NOAA funded study of the net pen salmon farming industry in the Pacific northwest (Nash, 2001); and the 11 volumes included in the "Salmon Aquaculture Review" of the British Columbian Environmental Assessment Office (Anon., 1997). Similar reviews exists for salmon farms outside British Columbia (e.g., Olivier and MacKinnon, 1998; Scottish Association for Marine Science and Napier University, 2002). Rather than re-iterating what has already been published, the following comments and opinions focus primarily on problems that may be of particular significance in the sablefish aquaculture context. The comments are guided by the 1988 Memorandum of Understanding (MOU) between federal and provincial governments. Under the MOU, the federal Department of Fisheries & Oceans (DFO) is responsible for: identifying areas where fish farming can occur; aquaculture research; fish health and inspection; and imposing measures to protect and conserve wild fish and their habitats. The British Columbia government is responsible for aquaculture development and regulation activities.

Sablefish are ecologically distinct from the fish species that are currently being reared commercially in British Columbia (i.e., salmonids). While at sea, adult salmon keep relatively close to the surface, whereas sablefish are typically caught at depths of 500 to 1500 m (Beamish and McFarlane, 1988). Salmon juveniles rear in rivers or in estuaries, whereas juvenile sablefish spend their first 2-5 years in coastal inlets (DFO, 2003), in close proximity to the proposed sablefish net pen locations. Salmon enter rivers and deposit eggs in the substrate, whereas sablefish, which are marine broadcast spawners (Mason et al., 1983), are capable of spawning within the net pens, releasing spawning products into the local waters where they can potentially mix with wild stocks. As such, genetic contamination of wild stocks may more likely result from sablefish farm than from salmon, even in the absence of farm-escapees. These life-history differences need be considered in order to assess the potential environmental effects of sablefish aquaculture. Any environmental impact assessments that are not designed specifically to address the problems of sablefish aquaculture are not likely to adequately identify the problems. Moreover, any management decisions about sablefish aquaculture that are based solely on our knowledge of salmon farming could lead to unexpected or disastrous consequences for the wild resource.

Some potential risks to the wild resource include: the risk of disease or parasite transfer from net pen fish to wild stocks (from escaped fish or because of close proximity of farm sites to juvenile nursery grounds); the loss of valuable juvenile sablefish habitat to new or existing sablefish farms; the pollution of juvenile rearing habitat from farm sewage and fish feeds; the impacts on wild resources from drugs and pesticides used at aquaculture sites; and the genetic interaction between wild sablefish and farmed sablefish (and the potential loss of genetic diversity). Given the potential risk to the wild resource, the precautionary approach would dictate that an environmental impact assessment should be conducted before farmed sablefish are allowed in marine net pens.

This report will discuss each of the CSA's issues with regard to the potential risks of marine net pen sablefish grow out operations. The important questions will be identified, the published literature will be reviewed, and potential research directions will be suggested. We conclude that there are real risks that need to be addressed before marine net pen sablefish aquaculture is permitted in British Columbia.

2           The Precautionary Approach to Sablefish Aquaculture Development

Salmon aquaculture development in British Columbia was accompanied by federal and provincial environmental monitoring activities to determine the magnitude and types of impacts on wild species and their habitats. Despite this, and the availability of considerable background information on salmon biology and ecology, the Auditor General of Canada (AGC) recently pointed out that the DFO "was not carrying out its current regulatory responsibilities to enforce the Fisheries Act with respect to farming operations," and, "there were shortfalls in research and monitoring to assess the effects of salmon farming operations," and, "had not put in place a formal plan for managing risks and for assessing the potential cumulative environmental effects of proposals for new sites" (Anon., 2000a). A cursory review of recent developments indicates that little has been done since the AGC review to rectify this situation. Interestingly, Noakes et al. (2000) echoed similar views on the DFO failure to protect wild salmon stocks from the negative impacts of publicly funded salmon hatchery operations in British Columbia.

In contrast to salmon aquaculture, little is known about sablefish aquaculture. Still, the provincial government recently issued several amendments to existing salmon aquaculture licenses, allowing sablefish to be raised at some salmon farming sites. It would seem reasonable to request that standard environmental and risks assessments be conducted before sablefish grow-out sites are licensed, sited, stocked and operated, so the situation described by the AGC is not duplicated, and so that the UN’s Precautionary Approach (FAO, 1996; Porter et al., 1998) is applied in a responsible fashion with regard to the regulated expansion of this new industry. The current situation seems to support the legitimate and justified concerns expressed by the CSA about allowing untested sablefish farming practices to take place in close proximity to wild sablefish rearing habitats and fishing grounds.

Past studies on salmon farm aquaculture operations provide useful insight on mechanisms by which rearing practices can impact on wild species and their habitats, but there is no substitute for sablefish-specific rearing studies, farm monitoring and impact assessments. The current knowledge base on sablefish aquaculture is clearly insufficient to conduct even a crude qualitative impact assessment. It may take years before the necessary studies yield the information needed to quantify potential impacts with some level of certainty. In the interim, at a minimum, an adaptive management plan (Walters, 1986) should be implemented to learn by direct manipulation of pilot farming operations (under safe/strict conditions), but even such a plan has yet to be formulated and agreed upon by representatives of industry, government and First Nations.

3           The Potential Ecological Risks

Assessments of the ecological risks associated with sablefish net pen culture should be designed to address the concerns outlined in the following sections. 

3.1          Risk of disease or parasite transfer from net pen fish to wild stocks

The main issue concerning sablefish rearing at this stage is determining the susceptibility of penned and wild sablefish to disease or parasites. Since the sablefish net pens will likely be in proximity to existing salmon farms, transfer of pathogens between salmon and sablefish is also of concern.

Sablefish farms and hatcheries can act as vectors for the transmission and amplification of various pathogens, including parasites, bacteria, fungi and viruses. Typically, the pathogens which affect fish in net pens occur naturally in wild fish (Kent, 2000). As such, wild fish are clearly susceptible to the transfer of pathogens from net pen fish back to their natural hosts. In the wild, infected animals are removed by predators at the first sign of weakness (Crawley, 1992). However, in a net pen, infected fish are protected from predators and live longer than they would in the wild, potentially shedding greater volumes of pathogen into the water. Since there is no way for the healthy farm fish to physically separate themselves from the infected fish, the risk of further infection (and possibly epidemic) increases. Moreover, crowding and handling can cause stress responses in captive fish, which can lead to increased susceptibility to disease (see Crosa, 1983). Pathogens could potentially be transmitted from infected farms to the wild sablefish when the farm sites are in close proximity to juvenile nursery grounds (i.e., pathogens get transferred to the wild juveniles) and when escaped farmed fish interact with wild individuals.

A number of observations of diseased sablefish have been documented in the scientific literature. For example, Gores and Prentice (1984) reared 39 sablefish in marine net pens for two years. Disease-related mortalities were attributed to furunculosis (Aeromonas salmonicida) and Vibrio anguillarum. Furunculosis was also reported for rearing experiments conducted at the Pacific Biological Station (Kennedy, 1974). Eight batches of sablefish (from 30 to 373 fish per batch) were reared in separate 3000 L tanks. Furunculosis was diagnosed in three of the eight tanks (Kennedy, 1969, 1970, 1974; Kennedy and Smith, 1971, 1972, 1973), and was present, but not properly diagnosed in a fourth (Kennedy and Smith, 1972). Infection reached epidemic levels in one of the batches (Kennedy and Smith, 1972); that for which stocking density was highest. The strain of Aeromonas salmonicida which caused the furunculosis at the Pacific Biological Station has also been found in wild trawl-caught sablefish (Evelyn, 1971) and in two species of cultured Pacific salmon. Infection transmitted via sea water has been demonstrated (Scott, 1968).

Gores and Prentice (1984) also reported lesions (5 to 8 mm in diameter) at the base of the pectoral fins, operculum and/or anal fin, at times affecting 40% of the penned individuals. The lesions, which the authors could not attribute to any apparent cause, lasted from one to seven months, with greatest intensity from September through December.

In a study of salmonid pathogens found in ocean-caught fishes in British Columbia, Kent et al. (1998) examined 33 sablefish of which four were diagnosed with epitheliocystis, and two were found to be infected with the protozoan parasite Loma. Brocklebank (1996) reported papillomatosis in a farmed sablefish. Papillomatosis is caused by a retrovirus, and results in the growth of epidermal tumors on the skin and scales. The tumors may occur at any site on the body surface and can be 5 mm thick and 4 cm in diameter. Fish that are heavily infested with the tumors may succumb to other secondary bacterial, viral, or fungal infections. No methods of treatment or control are known.

Approximately 38% of the fish reared by Gores and Prentice (1984) became blind in at least one eye, several of which developed severe eye infections causing the eyes to protrude. Similar eye problems were reported by Kennedy (1969).

Moser and Noble (1976) described the occurrence of a myxosporean protozoan parasite (Leptotheca informis) in the gall bladder of a wild-caught sablefish. Moser (1976) described a new myxosporean species found the gall bladders of three individual wild-caught sablefish, and named the new species Ceratomyxa anoplopoma after its host. The copepod Lepeophtheirus parviventris and the larvae of the nematode Phocanema decipiens have also been described in sablefish (Kabata, 1973; Hoskins et al. 1976; both summarized in Margolis and Arthur, 1979). Kabata and Whitaker (1984) examined 30 sablefish specimens and found 14 species of parasite, including seven trematodes, four nematodes, and one each of Cestoda, Acanthocephala and Copepoda. Kabata et al. (1988) found seven species of trematode in 419 sablefish from 13 locations. Whitaker and McFarlane (1997) examined 246 sablefish and found 10 species of parasites of which several had not yet been recorded in sablefish (see Table 1).

Table 1.     List of parasites described in sablefish hosts. Sources are: Moser (1976); 2: Moser and Noble (1976); 3: Margolis and Arthur, 1979; 4: Kabata and Whitaker, 1984); 5: Kabata et al., 1988; and 6: Whitaker and McFarlane (1997).

In addition to these published accounts, the DFO Fish Health Laboratory researchers have recorded the presence of 24 different diseases and parasites in cultured and wild sablefish (Table 2 DFO, unpublished data[1]). Appendix A provides a brief description of the main sablefish diseases that have been reported in the literature or that appear in DFO's database. Many of the diseases are common to salmonid populations (Roberts and Shepherd, 1986) including furunculosis, Vibriosis, Viral Hemorrhagic Septicemia, and Bacterial Kidney Disease.

Table 2.     Diseases and parasites found in wild and cultured sablefish as diagnosed by the DFO Fish Health Laboratory at Pacific Biological Station, Nanaimo, British Columbia. Eighty-three sablefish were examined.

Many of these pathogens can have a major effect on sablefish health, survival and the ability to reproduce. Although vaccines exist for two of the most commonly observed pathogens (furunculosis and Vibriosis; W. C. Clarke[2], pers. comm.), there are others that can be potentially devastating to the wild resource (e.g., Bacterial Kidney disease, Viral Hemorrhagic Septicemia). Sablefish demography is such that a few large year classes contribute heavily to the spawning biomass, and the fishery is dependent on large, periodic recruitment events (Sigler et al., 2001; McFarlane and Beamish, 1986). As such, an outbreak of a serious disease among juvenile sablefish occurring in the "wrong year" could affect recruitment and hence the fishery for many subsequent years (i.e., until the next big recruitment year).

It is clear from the preceding treatment that sablefish can be afflicted with several varieties of muscle, eye and gill parasites. Though many such parasites are non-lethal, they can reduce growth rates and hence fecundity (fecundity is a function of size; Mason et al., 1983; Macewicz and Hunter, 1994). Moreover, muscle parasites can affect the appearance and texture of the meat and hence affect the market value of the fish.

Given that sablefish culture is still in its infancy (i.e., no large-scale facilities are yet operating), relatively few fish have been reared, and hence only a few of the potential problems have been identified. In general, farmed fish are susceptible to many diseases that are seldom seen under natural conditions, and that only becomes a problem when fish are kept under different environmental conditions (Kent, 2000). As such, the diseases that have been reported in the literature, and that are shown in Table 2 likely represent only a small portion of the diseases and parasites to which sablefish are susceptible.

To our knowledge, no studies have been performed to investigate the risk of disease transfer between nearshore salmon net pen operations and the juvenile sablefish that reside in the nearby inshore habitat. Since the proposed sablefish net pen sites will be located in nearshore environments, since juvenile sablefish are known to enter net pens, and since adult and juvenile sablefish will likely be susceptible to all the diseases that afflict adult sablefish, it would be prudent to focus research efforts on identifying those diseases or pathogens that can be readily transferred between farm sablefish and wild juveniles. Given the potential risk to wild fish, these initial investigations should be conducted in a laboratory facility or in land-based tanks.

In order to get a more complete understanding of the types of diseases that can affect sablefish under commercial rearing conditions, it may be necessary to hold large numbers for extended periods of time. Again, the potential risk of wild-stock contamination precludes experimentation in nearshore net pens. As such, any large-scale holding and rearing trials should be conducted in a land-based facility.

What follows is a number of potential experiments that could be conducted to address some of the important questions about disease transfer. These examples are meant to provide a starting point for discussions about how the necessary questions about sablefish disease transfer can be addressed.

One potential group of experiments could be carried out in a land-based tank which is large enough to contain a scale-model net pen which would occupy a minority of the tank volume (as the rest of the tank would simulate the waters surrounding a net pen site). Control fish would be put in the main part of the tank, and Experimental fish would be put into a scale-model net pen. As such, the Experimental fish would be restricted to a smaller volume and would experience higher stocking density than the Control fish. To examine whether caged fish are more susceptible to disease than wild fish, a number of diseased sablefish could be introduced into the tank. The diseased fish could be introduced into the tank at large (to explore transfer of disease from wild to caged fish) or into the net pen (to explore transfer of disease within the net pen). Rates of infection would be compared between the "farmed" and "wild" populations. It may be favorable to use juvenile sablefish as the Control group.

If it is found that caged sablefish are more likely to contract diseases / parasites than wild individuals, then experiments should be designed to determine what the appropriate stocking densities should be to avoid serious disease outbreaks. In an experimental tank similar to that described above, the densities in the model net pen can be varied from trial to trial to determine acceptable stocking densities. Control fish should be stocked at densities similar to that found in the embayments near the proposed net pen sites.

It may be difficult to directly assess how far the net pens should be from the juvenile rearing habitat to minimize disease transfer. However, the effluent from a tank containing diseased fish could be diluted to smaller and smaller concentrations to mimic a net pen being located farther and farther away. Tanks of wild juvenile sablefish could be subjected to one of a variety of these dilutions, and the rates of infection could be used to determine the dilution required to minimize risk to the wild fish. Given information about flushing in the nearshore environment, distances can be calculated from dilutions, to give an estimate of the minimum distance that pens should be placed away from the juvenile rearing habitat in the nearshore inlets.

3.2          Risk of disease introduction from the importation of exotic species, eggs and milt

The best way to prevent the disease-introduction when placing farmed sablefish into nearshore marine waters is to ensure that all milt, eggs and/or juveniles that are used to seed sablefish farms come from the local area. The use of local origin fish is recommended because there have been several cases in recent history in which the translocation of fish from a localized population into a novel area has resulted in rampant disease outbreaks that wreaked havoc on the local wild stocks. For example, furunculosis was introduced to Norway in the 1980s following the importation of Atlantic salmon smolts from Scotland, and has had significant impact on the wild stocks (Johnsen and Jensen, 1994).

Another reason that local fish should be reared is related to the possibility that sablefish are genetically adapted to local conditions. Local adaptation has been documented to evolve quickly (Hendry et al., 2000), and genetic population structure is common in marine broadcast spawners (e.g., Ruzzante et al., 1999). When local fish are reared, the problems associated with genetic interaction between farmed and wild fish are minimized (see Section 3.7).

There is a need to ensure that the adequate egg fertilization practices are used in hatcheries (if used to supply farms) to ensure that the sablefish produced have levels of genetic diversity akin to those generated via natural spawning events. Also, there is a need to determine if there are pathogens in the flesh, eggs or milt that can be transmitted to hatchery environments and eventually to sablefish farms when these are stocked. It may be prudent to require disease-free certifications for any sablefish eggs that enter a hatchery (similar to those for the salmon industry with respect to IHN). The critical sablefish pathogens must first be identified (see Section 3.1).

3.3          Risk of disease transfer between domestic farmed and wild species

This issue is partly addressed in Section 3.1 above. If farmed sablefish are particularly susceptible to some pathogens, one could logically deduct that wild sablefish may also be susceptible to the same pathogens. However, to demonstrate that there is a significant risk to the wild population(s), one must show that the pathogen can be transmitted via some vector (birds, boats, divers, fish, currents, etc.). Experiments need to be carried out to identify these mechanisms.

3.4          Pollution of habitat from fish sewage

It seems reasonable to assume that all fish farming operations in coastal waters off British Columbia will be subject to the same regulations concerning the allowable discharges (type, amount), irrespective of the species raised. The issue of concern to the sablefish industry is how much waste (mortalities, feces, uneaten food, chemical, etc.) is typically generated over a certain period by a typical operation. Studies need to be conducted to determine how discharge rates and composition of sablefish farming operations (and supporting hatcheries) compare to those of salmon farming operations.

3.5          Loss of juvenile habitat

Ideally, surveys should be conducted before the proposed grow-out sites are operated to determine the usual densities of wild juvenile sablefish in the area, and the environmental attributes of the area. At a minimum, this would provide pre-impact data needed to determine the impact (if any) of the aquaculture operation on the wild population and their habitats. It would be prudent, at least initially, to restrict aquaculture operations to sites located more than a set minimum distance from known juvenile sablefish rearing areas. This would comply with the Canadian Fisheries Act, administered by DFO, which requires "no harmful alteration, disruption or destruction of fish habitat" resulting from industrial activity or development. This act also requires that the DFO takes measures to protect "critical fish habitats," which includes areas used for rearing and migration of wild fish. This would also reduce the potential for direct contact and disease transfer between wild and farmed sablefish.

3.6          Impacts on wild resources from drugs and pesticides used at aquaculture sites

At this stage it has not been yet been shown that certain sablefish rearing conditions (typical and/or crowded/stressful) require drugs, antibiotics, pesticides and other chemicals. As for the other chemicals, it seems reasonable to expect that government regulations will likely apply to all marine farming operations irrespective of the species raised. Initial research should focus on the chemical supplements (type, dose, etc.) required for typical sablefish farming operations, and determine suitable siting locations.

3.7          Genetic interaction between wild and farmed fish

Large-scale, commercial sablefish rearing practices have not yet been established, and it is possible that maturing farmed sablefish would spawn in the net pens. The potential impacts are difficult to predict given the lack of information about the viability of the products of shallow-water, near-shore sablefish spawning. It is not known if sablefish can produce viable gametes at shallow depths. It is not known if the fragile sablefish eggs will be able to survive in the more turbulent waters near-shore (see Alderdice et al., 1988). Differences in behaviour and growth rate between wild juveniles and those that result from net pen spawning are unknown, hence it is difficult to predict how effectively domestic offspring will compete with wild juveniles in the near-shore nursery grounds. Studies are needed to address these issues.

In addition to net pen spawning, there is a possibility of genetic interaction resulting from the mixing of wild and escaped farmed fish on the spawning ground. There is currently no information available that addresses this issue. It is not known whether escapees will forage properly since they would be habituated to eating pellets. If the escapees survive, it is not known whether they will migrate to spawning grounds. Controlled feeding studies, coupled with an experimental escapee tagging program should be done to investigate these issues.

One way to avoid the issues associated with genetic interactions is to allow only sterile sablefish to be used for aquaculture purposes (assuming sablefish can be sterilized), at least initially. Note that since sterile escapees may still compete with wild mature sablefish for food or other resources (leading to a potential loss in productivity), escapes should nevertheless be deterred as effectively as possible.

It should be noted that the mixing of locally resident spawners with a non-local (farmed escapee) would produce less viable offspring under two scenarios: 1) local adaptation; and 2) domestication.

Local Adaptation

In the first scenario, the wild fish must be genetically adapted to their local environments, such that spawning with non-locals would result in offspring that are genetically maladapted to the local conditions. For local adaptations to manifest, and for genetic differences to be maintained, individuals must home to the same spawning ground each year (or show year-round site fidelity), such that there is little mixing of local populations during the spawning season. Homing has not been demonstrated in sablefish, though year-round site fidelity may occur as 75-80% of tagged Vancouver Island and Queen Charlotte Sound sablefish were recaptured up to nine years later less than 50 km from the locale at which they were tagged (Beamish and McFarlane, 1988). Nevertheless, straying rates (the proportion recaptured more than 200 km away) were large enough (10-12%) for genetic panmixis (assuming the strays spawn in their new location), and there is yet no conclusive proof of genetic population structure in North American sablefish.

The single published study on sablefish genetics (Gharrett et al., 1983), a preliminary report, indicated that some genetic substructure may exist, but the results were inconclusive because the sablefish were not collected during the spawning period, when any existing sub-populations are most likely to be physically separated. The lead author believes that his paper has many shortcomings, and hopes to use newly developed techniques (described in Matala et al., 2004) to revisit the data in a more rigorous manner (A. J. Gharrett[3], pers. comm.). Meanwhile, Beamish and McFarlane (1988) referred to the only other genetic study of sablefish by quoting personal communications from G. Winans and G. Stauffer at the NW and Alaska Fisheries Center (Seattle, WA), writing that they have completed an "extensive comparison" which "concluded that, in general, sablefish stocks are one population." A shortcoming of the study, similar to that of Gharrett et al. (1983), is that the analysed sablefish were not collected during the spawning period. Winans' paper is now in manuscript form and is currently undergoing peer review (G. A. Winans[4], pers. comm.).

The use of parasites as biological tags is a well-established technique for differentiating fish stocks (e.g., Sherman and Wise, 1961). When parasites are restric