Northern wolffish and spotted wolffish recovery strategy: chapter 6

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5. Threats

A discussion of anthropogenic effects leading to the observed decline cannot be decoupled from natural causes since the two are surely linked. The magnitude of the role of natural vs. anthropogenic effects is poorly understood. It seems likely that a combination of natural and human induced mortality, perhaps in combination with poor recruitment, caused the wolffish populations to decline.

We can however exert control over some of the anthropogenic activities that have an impact on wolffish populations. To do this, we need to know which activities constitute a threat to the populations and their habitat, and how to change or curtail these activities in order to lessen their impacts and, at the same time, increase the chances of recovery of the wolffish populations.

However, the current level of knowledge limits the effectiveness and scope of Canadian recovery initiatives. Population structure, absolute estimates of population size and relative contribution of threats to the decline are unknown. Knowledge of exactly how habitat has and is being utilized and to what extent available habitat is critical to the species survival or recovery is unknown (Kulka et al. 2004). With development of that knowledge, a better understanding of the threats can be achieved and measures required to mitigate factors limiting recovery can be refined.

Preliminary information on total removals of wolffish species combined is provided in Simpson and Kulka (2002), but a species by fishery breakdown is required to evaluate the potential impact on each species. Possible bottom alteration due to fishing activities on or near wolffish habitat needs to be better quantified; there is currently little or no information on the effects of bottom trawling, although trawled locations have been delineated by Kulka and Pitcher (2001). The effects of bilge and ballast water are unknown. Pollution from land-based sources that could affect the well being of the species needs to be identified and, to the extent possible, mitigated. Offshore exploration for minerals, oil and other resources needs to be carried out with environmental protection in mind.

Linking stewardship to recovery activities, communication and education programs need to be specific and understandable for each stakeholder. If these initiatives are ineffective, cooperation from legislators, scientists, industry and all other stakeholders in the protection of an incidentally caught fish with low perceived economic value will be difficult to foster and promote. As a result, it is likely that currently known threats will not be properly mitigated and suspected threats will not be studied to determine their relative effects.

There is a need to delineate temporal and spatial effects of threats and the intensity of these threats on the various life stages of wolffish and their habitats. Regional cooperation to protect these threatened wolffish species and their habitat must be implemented.

5.1 Fishing

The impact of incidental capture of wolffish in many fisheries is thought to be the leading cause of human induced mortality. However, what proportion mortality due to fishing activities contributes to total mortality and to the decline of these species is unclear.

Prior to the requirement to release threatened wolffish species taken incidentally in Canadian fisheries, instituted in 2003-2004, wolffish catches and landings were unregulated. There is no directed fishery for wolffish in Canadian waters, but their extensive distributions which overlap fishing grounds have made them a common bycatch in many of the Atlantic fisheries.

Kulka (1986) and Simpson and Kulka (2002) noted that nearly all bycatch of A. denticulatus were discarded and about half of the other two species were retained, thus landing statistics underestimate actual catches. Reported catches of wolffish were considerably higher in the 1960s and early to mid 1970s prior to the period of decline (Simpson and Kulka 2002). Trawl effort in the years just preceding and during the decline was considerably lower and has remained low since. During the 1980s, Canadian catches, including amounts discarded at sea, exceeded 1,000 t in most years. Catches then declined after 1991, when many demersal fisheries were closed. Kulka and Pitcher (2001) showed that about 20% of the shelf area on the Grand Banks to Labrador Shelf was trawled annually during the early 1980s, dropping to about 5% in the 1990s. Since the early 1990s, the reduced effort has resulted in less bycatch of wolffish, affording them a level of protection.

A greater proportion of A. lupus and A. minor was retained in the 1990s. On the Grand Banks to Labrador Shelf, reported Canadian landings were only 23 t in 1996, but increased to 157 t in 1997, 155 t in 1998, 315 t in 1999 and 369 t in 2000. Recent increases are due mainly to bycatch from the cod longline fishery south of the island of Newfoundland. About 250 t are also taken in the yellowtail fishery on the Grand Banks, but all are discarded. In the areas south of the Grand Banks, from the Gulf of St. Lawrence, Scotian Shelf, Bay of Fundy and Gulf of Maine, wolffish landings (almost exclusively A. lupus) were 1,000 to 1,500 t in the 1960s, increasing to about 2,000 t between 1968 and 1979 and peaking at about 4,000 t in 1983 (all countries included). Landings dropped steadily to 1,000 t in the early 1990s and were estimated to average about 625 t in the early 2000s, prior to mandatory release of the threatened species. Canadian landings represent approximately 55% of this total, with the remainder consisting mostly of U.S.A. landings from the Gulf of Maine area. Canadian landings of wolffish since 1986 were primarily from the southwest Scotian Shelf and constituted 81% of the total, with the western Gulf of St. Lawrence contributing 10% and the remainder spread out among other areas (McRuer et al. 2001). Since 2004, all A. minor and A. denticulatus taken incidentally in Canadian waters must be released in a manner that maximizes chance of survival.

Commercial landing statistics lump all wolffish together under the general category “catfish” that includes A. minor and A. lupus. However, fishery observer records do differentiate by species indicating that since the late 1990s, about 80% of the catch of the two threatened species, A. minor and A. denticulatus occurs in the Greenland halibut directed fisheries on the Labrador Shelf and Grand Banks (Kulka and Simpson 2004). Commercial log data are thought to underreport catch rates for all three species, as indicated by fishery observer data from various fisheries.

Areas of greatest decline for all three species, on the inner northeast Newfoundland and Labrador Shelf (where wolffish formed high density concentrations in the 1970s) are areas where trawling seldom or never occurs (Kulka and Pitcher 2001) or any other form of fishing seldom takes place. Some of the most intense fishing effort during the 1970s through the early 1990s was located on the shelf edge, north of the Grand Bank where significant concentrations of the wolffish species still occur and where the vestiges of some commercial species such as cod were concentrated just prior to their collapse (Rose and Kulka 1999). Thus, it is the most intensely trawled areas along the shelf edge from the northern Labrador Shelf to the Grand Banks where the three wolffish species continue to be most abundant. That these species undertake limited movements, (Templeman 1984) and given the mismatch in area of greatest decline for wolffish and trawling activity, while certainly contributing to the total mortality, the evidence is contrary to the hypothesis that trawling is the only or perhaps the proximal cause for the decline in wolffish (Kulka et al. 2004). This suggests significant non-fishery influences coupled with fishery related mortality contributing to the distribution and abundance changes observed.

A significant proportion of fishing mortality for wolffish occur outside Canada’s territorial limit. Non-Canadian bycatch of wolffish in the NAFO (Northwest Atlantic Fisheries Organization) Regulatory Area (NRA) are thought to be underreported (Simpson and Kulka 2002). Depths fished and amount of effort fished in the NRA suggest that those bycatches could constitute a substantial proportion of the mortality since those captures are unregulated and most of the fish are retained for commercial purposes. Fish taken there are probably part of the same population that inhabits Canadian waters.

Presently, release of all threatened wolffish species captured in Canadian waters is mandatory. However, consideration must also be given to the effects that displaced effort would have if area closures are to be considered as part of a recovery strategy. To mitigate the impacts of human fishing activity, mechanisms for identifying potential bycatch caps and associated implementation measures need to be developed. The issue of over-exploitation due to bycatch (limits established for bycatch of wolffish exceeded in fisheries where quota of the directed species have not been reached) should be a focal point for examining the problems involved in managing a multi-species fishery.

The collection and processing of logbook data related to wolffish catches needs to be examined. To do this efficiently, essential input for logbooks must be identified through cooperation between harvesters, observers and scientists. Design of logbooks in the future must take into consideration that other marine species designated as at risk will have to be recorded. Logbooks should be organized to be able to accommodate the integrated collection of harvesting statistics for a wide range of species not currently reported, including wolffish.

Since harvesting was identified in the COSEWIC Status Report (unpublished) as a cause of the decline of wolffish populations, sustainable harvest bycatch levels need to be determined for each species or population for each fishery (although, as previously indicated, the proximal cause of the decline has yet to be determined). To prevent further population decline and promote population growth for Atlantic Canadian wolffish species, research on life history, population structure and their ecosystem interactions is essential to determine population size and structure, and ultimately how much of the population can be harmed by fishing without affecting recovery.

Harvesting technology, specifically bottom trawling and dredging, have been identified by COSEWIC as possible causes of wolffish habitat alteration. Incremental losses of nesting and shelter habitat (habitat alterations, degradation and associated fragmentation) due to fishing are potential threats to the recovery of wolffish species, a family of fish that apparently have limited dispersal and possible nesting requirements. However, for practical reasons, trawling operations avoid rocky areas since trawling in such areas leads to the destruction of expensive gear. This affords a level of protection for rocky habitats. Also, as noted previously, areas of greatest decline do not correspond with locations of most intense trawling.

5.2 Offshore Oil, Gas and Mining Activities

5.2.1 Seismic Activities

Eastern Canadian waters are a region of intense exploration for petroleum related resources. To identify probable oil and gas reserves, the offshore oil and gas industry uses seismic exploration techniques to evaluate the geology that underlies the sea. This involves the use of towed arrays of airguns – cylinders of compressed air containing a small volume (typically between 10-100 cubic inches) at a pressure of about 2000 psi. The array, containing some tens of cylinders, is repetitively discharged to generate a pressure pulse.

No research has been carried out on the affects of seismic activity on wolffish species but (Sverdrup et al. 1994) suggest that airgun blasts constitute a highly un-physiological sensory stimulus to fish. The noise from airguns generates a compression and decompression wave in the water that, at close range, is sufficient to kill fish at certain life stages (Boudreau et al. 1999). At less than about 5 m, air guns have the potential to cause direct physical injury to fish, eggs and larvae. However, Payne (2004) provides a literature review that suggests that injury to fish eggs and larvae even at close range is limited. It is likely that fish would be driven away from the noise prior to coming close to the air guns, so the risk of physical injury would be greatest for those organisms that cannot swim away from the approaching sound source, especially eggs and larvae. If seismic operations are conducted in areas where larvae are aggregated then higher levels of mortality may occur. However, the level of mortality for marine fish is not regarded as having significant effects on recruitment to a stock (Payne 2004, Dalen et al. 1996). In the case of wolffish, adults and eggs are generally found on or near bottom at distances of 100-900 m away from the surface. Hence, direct physical impact on these life stages will likely be minimal or non-existent. It is the near surface larval stages that could potentially be directly affected by seismic activity. Seismic activity synchronized with periods of larval hatching has the greatest potential for harm.

Little is known about the behavioral effects that may occur at greater distances from the air gun noise source. It is possible that wolffish adults guarding nests could leave the area of disturbance to the detriment of the egg cluster. However, no information exists for wolffish to confirm the potential effects. Effects noted by Dalen et al. (1996) for other fish species included changes in the organism’s buoyancy and changes in their ability to avoid predators. Research indicates a loss of structural integrity and the reduced functional responses indicated a temporary impairment of the vascular endothelium in response to seismic shock in other fish species (Sverdrup et al. 1994).

Research on the sand eel (Ammodytes sp.) indicates that, species lacking swim bladders have a higher hearing threshold than species with swim bladders (Hawkins 1981). The distance at which behavioral effects are induced in species without swim bladders, such as wolffish may likely be shorter than for species that possess swim bladders. Further research is required to determine the hearing capacity of wolffish.

At close distances, airguns produce shock wave forces that have the potential to cause internal damage to air and gas containing organs of fish. One would expect that fish with swim bladders are more susceptible to direct physical injury than those without (i.e. sand eel and wolffish). Therefore, it is incorrect to state that the distance at which biological damage occurs may likely be shorter than for those species with swim bladders. However, if species that lack swim bladders have a higher hearing threshold than species with swim bladders, it would be logical to surmise that the distance at which behavioral effects (i.e. scaring of fish) are induced should be shorter.

The impact of seismic activity and other exploration methods used to research offshore resources needs to be quantified with respect to wolffish and their habitat. There are no documented cases of mortality of any fish species upon exposure to seismic sound under field operating conditions (DFO 2004a). Nothing is known about the possible effect on wolffish species at any stage of their life history, and currently there is scientific uncertainty regarding the potential impacts of seismic activity on marine organisms in general. Any knowledge gained by scientists must be provided as guidance to the industry.

5.2.2 Oil and Gas Exploration and Production

Increased exploration and production of petroleum resources in eastern Canadian waters increases the possibility of oil spills, offshore well blowouts, tanker spills and other potential disasters. These accidents release petrochemicals, dissolved metals (toxic metal ingestion) and other solids to the ecosystem. In addition, exposure to these pollutants and other potential pollutants may result in direct mortality or a host of sub-lethal impairments to wolffish, their prey and their ecosystem (e.g., slower growth, decreased resistance to disease, etc.).

With any petroleum development there is always the chance of a major release of either oil or gas into the environment from a spill associated with the storage and movement of the product after extraction or a blowout during drilling. Well blowouts and major spills, however, have the potential of releasing hydrocarbons at a rate faster than natural ecosystems can accommodate them and of affecting organisms not previously exposed to oil derived hydrocarbons in concentrations greater than trace amounts.

The amount of spilled oil that enters the water by dispersion and dissolution varies considerably with composition and environmental conditions, but generally is on the order of 5-15%. Oil in the water column may have a higher potential toxicity than surface slicks due to the reduced potential for evaporation of the lighter toxic components (Boudreau et al. 1999).

The amount of oil reaching bottom sediments depends on numerous factors including the volume of the blowout, type of blowout (platform or sea floor), hydrocarbon composition, wind, currents and water column structure, depth of water and degree of water column mixing. Transport mechanisms include adherence to particles, incorporation into zooplankton faecal pellets, direct sedimentation of weathered oil particles and vertical mixing.

It remains very difficult to show the impacts of oil-induced mortality on early life stages of finfish and invertebrate resources because of their large and variable natural mortality. The effects of oil on adult fish in the field are difficult to study and therefore knowledge is incomplete. Any mortality of benthic species induced by a single event would probably be limited in both extent and time (Boudreau et al. 1999). If regulations and guidelines are followed, the impacts of accidental events are likely to be negligible for wolffish or other species. As well, the only near surface stage of wolffish is the larval stage and thus, this is the only part of the life cycle that could be potentially effected by the release of hydrocarbons.

Release of hydrocarbons is not the only potential issue. The debris generated from drilling operations has two major components; muds and cuttings. Muds tend to be finer, less dense material, while cuttings are generally coarser and heavier pieces of rock about the size of sand grains (Boudreau et al. 1999). The most obvious impacts of exploratory drilling on the environment have been associated with drilling muds. There are three classes of muds: water- based muds (WBM), diesel oil-based muds (OBM), and alternative-based muds (ABM) that include both mineral oil and synthetics. Once discharged, there are a number of different processes that act on them and that determine their fate and potential impacts on the environment.

The circulation and Benthic Boundary Layer Transport (BBLT) determines the fate of fine particles of drilling mud, the key determinants of dispersion, and how impacts might change with seasons (ESRF 2000). Roughly 10% of the discharged wastes is neutrally buoyant and forms a surface plume (NCR 1983). The factors that significantly affect the depth of descent were found to be mud density, depth of release, initial downward volume flux of the discharge, current strength and water column stratification (Andrade and Loder 1997). Discharged drilling muds can accumulate in low energy systems to smother benthic organisms near the rig and result in their suffocation. Similarly, in high settling velocity of the cuttings, there is reason to believe that smothering might kill significant numbers of slow moving or sessile organisms in the area directly under a drill rig (Boudreau et al. 1999).

A synthetic based drilling fluid (IA-35) is presently being used in the Newfoundland & Labrador offshore. Toxicity studies carried out on scallops as well as selected studies with plankton and fish larvae, indicate a very low potential for acute toxicity (Cranford et. al 2000; Armsworthy et al. 2000; Payne et al. 2001). The acute toxicity data available for both synthetic and water-based fluids indicates that discharges from platforms into well mixed waters should result in little or no chemically mediated acute effect (Neff 1987; GESAMP 1993; Payne et al. 1995). It has been demonstrated that cuttings have a very low acute toxicity as well (Payne et al. 2001).

At the Hibernia oil production site on the Grand Banks, the zone of biological effects seems to be localized. However, further studies should be undertaken on resource species such as American plaice. Hydrocarbons and metals decline within 1000m, polyaromatic hydrocarbons (PAHs) are below detection limits, the sediments are non-toxic, and there is no evidence of taint in American plaice caught within 3000 m of the platform. Overall, no significant impacts have been found (ESRF 2000). Extrapolations indicate little or no risk even as close as 1000m or less from the rig site over the life of the project. Risks could also be further reduced at development sites in deeper waters or sites with stronger currents and thus greater potential for particle dilution and dispersion (Payne et al. 2001).

Other literature indicates physical and toxic effects of discharges. Effects of high toxicity oil-based mud were found to be restricted to within 500m of rigs, however, subtle effects in benthic organism diversity and community structure can be observed as far away as several kilometers (Olsgard and Gray 1995; Daan et al. 1990; Kingston 1992). Water-based mud, although not toxic, can bury organisms, and its effects were found at 50-100m. The effects of synthetic-based mud were found at 250-500m. The toxic effects of ester-based muds are greater due to their high oxygen consumption (ESRF 2000).

Produced water contains heavy metals, hydrocarbons, nutrients, radionuclides and added chemicals. At present the environmental impacts of produced water are unclear. The potential for toxic effects may be reduced quickly through dilution but chronic effects may emerge due to long term exposure, and inhibitory effects may be seen. Also, contaminants may be sequestered in the benthic environment through physical and chemical processes (e.g. flocculation). Dilution does not completely abate the effects of dumping, nor does the waste sit still once it gets to the bottom (ESRF 2000).

Petroleum operations in Norway have been in operation for the past 20 years. Environmental assessments indicated distribution of effects of discharges to be up to a 10 km, much wider than predicted in the 1960s (ESRF 2000) but still a relatively small area in relation to the area occupied by wolffish.

Routine operational exploratory drilling activity is likely to have only localized impacts on the ecosystem components reviewed. The actual impacts will be dependent on the location, timing of the activities, and the properties of discharges. There exists a small probability that these impacts will have population and ecosystem level impacts (Boudreau et al. 1999).

In summary, operational discharges would cause some biological effects over relatively short time periods, and small distances from the discharge point. Smothering of benthic organisms by deposited mud and cuttings would not be anticipated outside an estimated 0.5 km radius from the rig. The use of lower toxicity water-based drilling muds should minimize the direct mortality on organisms, as would the use of low toxicity oil for lubrication and a spotting fluid. The zone of impact around a rig would vary with location time and quantity of discharge. Impacts would disappear rapidly once drilling ceases. It is anticipated that the dispersed muds, cuttings and associated hydrocarbons would cause localized sublethal effects for some bottom dwelling organisms. Because of the large degree of spatial and temporal variability in natural populations, and the limitations of current sampling methods, it is expected that it would be very difficult to detect the net result of any impact at the population level (Boudreau et al. 1999). Thus, any potential effects on wolffish would be highly localized insignificant to the population as a whole.

5.3 Ocean Dumping

5.3.1 Sewage Sludge

Sewage sludge may be disposed of in the marine environment by coastal dumping or pipeline discharge and have a known impact on both planktonic and coastal benthic communities. Sewage sludge contains bacteria and viruses, that are known to be toxic to shellfish, but their effect on wolffish is unknown. As much of this dumping is coastal, it is thought that the effect on widely distributed wolffish would be minimal. However, the potential of these effects need to be evaluated, and if identified as harmful, impacts must be mitigated.

5.3.2 Fish Waste

During the processing of fish and other marine organisms, a large volume of wastes are generated, including fish heads, tails, guts and internal organs. Fish waste can amount up to 75% of the weight of a fish before processing, depending on the species and process. Waste resulting from the industrial processing of fish and other marine organisms is rich in animal proteins and fats. Substances in the fish waste may undergo physical, chemical and biochemical changes when deposited in the marine environment. As well, various chemicals, primarily heavy metals and chlorinated hydrocarbons contained in the fish waste, may be accumulated in marine sediments, and subsequently released into the water column under specific circumstances, thereby becoming available to marine organisms.

The waste is subject to a rapid degradation process under the effects of heterotrophic bacteria. Waste that is not consumed by other marine organisms becomes an object for the activity of heterotrophic bacteria. Continuous dumping of the waste would lead to an increase in the density of heterotrophic bacteria in the dumping area. Eutrophication induced by the dumping of waste may change the structure of plankton and benthic communities. In critical conditions, oxygen depletion may have detrimental impacts, causing mortality.

Fish and other marine organisms may contain various chemicals, such as heavy metals, antibiotics and hormones. Concerns appear warranted regarding the overuse and misuse of certain chemicals, for which a proper risk assessment has not been made in relation to the marine environment. However, these issues apply mainly to coastal habitat and particularly to aquaculture species.

The susceptibility of fish waste to such changes should be considered in light of its eventual fate and potential effects. In addition, various chemicals contained in fish waste, as well as disease vectors and non-indigenous species, may have adverse impacts on wild fish populations consuming the fish waste. The chemicals may accumulate in the marine sediment, affecting benthic flora and fauna. In the past, it was common practice to dispose of such waste at sea, with the risk of overloading the ecosystem.

The effects on wolffish from the above mentioned are unknown, but are likely minimal since most of these effects are localized and coastal whereas wolffish tend to be widely distributed.

5.3.3 Dredging Spoils

It has been shown that sludge material dumped by barges reaches the ocean bottom, but not necessarily at the exact location where it was discharged, and that it has significant effects on the metabolism, diet, and composition of organisms that live there. The movement of dredge spoils from dumping can have multiple impacts on a series of adjacent habitats over time. The distance traveled by various particle types depends primarily on the size and density of the material, current velocities and weather patterns. The impact of the original spoil material may be magnified with subsequent re-suspension and deposition by tidal currents. Contaminants introduced to the sediments from dumping penetrated to a depth of 5cm below the sea floor as organisms living in the sediments burrowed through them. The contaminated materials that have entered the benthic food web have created a new benthic environment favoring species that can exploit the organic material available in sewage sludge.

Hard-bottom assemblages that become smothered by spoils from dumping can suffer drastic macrofauna and macroflora changes. Most invasive macrofauna are either sedentary and limited to settlement on exposed boulders above the spoil, or errant species (Elner and Hamet 1984). A positive effect of dredging was that species richness and individual weights increased in the dredged areas because the holes in the seabed created habitat refugia (Morton 2001). For wolffish, it seems likely that the impact of dumping of ocean spoils would be minimal since the area impacted would be very confined.

Wolffish and their habitat should be considered valued environmental components (VECs) and reported on when decisions are being made with regard to offshore activities requiring Environmental Assessments.

5.4 Military Activity

Military activity has and continues to take place in many areas of eastern Canadian waters. Little is known of the impacts of these activities and their effects on wolffish and their habitat. These effects need to be evaluated and potential impacts mitigated.

5.5 Cables and Pipelines

The placement of physical structures on or in the bottom substrate/water column could affect wolffish habitat although in a spatially limited manner. Given the widespread distribution of wolffish, impacts associated with these activities are likely minimal but need to be quantified.

5.6 Marine and Land-Based Pollution

Any human activity which has the potential to cause degradation to wolffish habitat, though marginal, needs to be identified, cleanup undertaken where appropriate, and prevention measures put in place. Associated land-based forms of pollution including runoff that contain excess nutrients, sediments, pathogens, persistent toxins or oil may significantly affect the marine ecosystem. The magnitude of change and its form depends on many factors including, the types of dissolved or suspended particles, such as non-biodegradable organic chemicals. These pollutants may adversely affect the reproductive capabilities of wolffish, their prey and surrounding vegetation as well as interfere with their general health.

5.7 Global Climate Change

The role of climate change as a factor in the decline of wolffish populations is currently unknown. Atmospheric changes may lead to changes in ocean productivity, species composition and habitat. Alterations in the chemical, biological and physical composition of habitats may influence population reproduction, mortality rates and individual behaviour. Historical data sources could be used to examine relationships between climate and trends in the distribution and abundance of wolffish. The investigation of climate change as a factor in the decline of wolffish is not a trivial task. It may be that no definitive answers will be found.

5.8 Natural Mortality (parasites, disease, predation and environment)

As with the vast majority of marine species, little is known of the effects of parasites, diseases, predation or environmental conditions on the survival of wolffish species. Pathological conditions and causal factors need to be identified as well as potential predators. Natural mortality may have played a significant role in the decline of these species, but as yet these processes are poorly understood.

5.9 Summary of Threats

Impact of incidental capture of wolffish in many fisheries is thought to be the leading cause of human induced mortality. However, the live release of spotted and northern wolffish mitigates the affect of incidental capture to some degree (see Part B, Section 5.3). Other potential sources of harm (habitat alteration, oil exploration and production, pollution, shipping, cables and lines, military activities, ecotourism and scientific research) are considered to have negligible impacts on the ability of both spotted and northern wolffish to survive and recover (DFO 2004b).

It is also recognized that non-human elements (environmental influences) may have played a role in the decline of the species and these effects cannot be controlled/mitigated. These environmental effects may continue to play an unpredictable role in the future. Thus, this document addresses anthropogenic influences only.

A discussion of anthropogenic effects leading to the observed decline cannot be decoupled from natural causes since the two are surely linked. The magnitude of the role of natural vs. anthropogenic effects is poorly understood. It seems likely that a combination of natural and human induced mortality, perhaps in combination with poor recruitment, caused the wolffish populations to decline.

We can however exert control over some of the anthropogenic activities that have an impact on wolffish populations. To do this, we need to know which activities constitute a threat to the populations and their habitat, and how to change or curtail these activities in order to lessen their impacts and, at the same time, increase the chances of recovery of the wolffish populations.

However, the current level of knowledge limits the effectiveness and scope of Canadian recovery initiatives. Population structure, absolute estimates of population size and relative contribution of threats to the decline are unknown. Knowledge of exactly how habitat has and is being utilized and to what extent available habitat is critical to the species survival or recovery is unknown (Kulka et al. 2004). With development of that knowledge, a better understanding of the threats can be achieved and measures required to mitigate factors limiting recovery can be refined.

Preliminary information on total removals of wolffish species combined is provided in Simpson and Kulka (2002), but a species by fishery breakdown is required to evaluate the potential impact on each species. Possible bottom alteration due to fishing activities on or near wolffish habitat needs to be better quantified; there is currently little or no information on the effects of bottom trawling, although trawled locations have been delineated by Kulka and Pitcher (2001). The effects of bilge and ballast water are unknown. Pollution from land-based sources that could affect the well being of the species needs to be identified and, to the extent possible, mitigated. Offshore exploration for minerals, oil and other resources needs to be carried out with environmental protection in mind.

Linking stewardship to recovery activities, communication and education programs need to be specific and understandable for each stakeholder. If these initiatives are ineffective, cooperation from legislators, scientists, industry and all other stakeholders in the protection of an incidentally caught fish with low perceived economic value will be difficult to foster and promote. As a result, it is likely that currently known threats will not be properly mitigated and suspected threats will not be studied to determine their relative effects.

There is a need to delineate temporal and spatial effects of threats and the intensity of these threats on the various life stages of wolffish and their habitats. Regional cooperation to protect these threatened wolffish species and their habitat must be implemented.