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MANAGEMENT STRATEGIES FOR RECOVERY OF ATLANTIC
COD STOCKS
|
Halibut Catch (t) |
Cod Catch (t) |
% Bycatch |
|
Landings Statistics |
1151 |
76 |
6.6 |
Halibut Comm. Index (observed sets)6 |
123 |
8 |
6.8 |
Thus, at least in this case, there is no evidence to support a view that cod bycatches are under-reported.
The invertebrate fisheries in 4VW have recorded landings as large as or larger than the groundfish fisheries in the period from 1994 (Fig. 30) but the landings statistics show virtually no bycatches of cod or other groundfish species. The highest volume fisheries are for shrimp, snow crab, arctic surfclam and scallops. Introduction of separator grates into shrimp trawl nets in 1991 appears to have essentially eliminated groundfish bycatches7. Only small amounts of finfish bycatch now occur in the fishery and these are primarily flatfishes, capelin and silver hake. Cod are essentially absent from these bycatches. Bycatches of cod do occur in the trap fishery for snow crab but such occurrences are rare8. The hydraulic clam dredges that are used in the surfclam fishery are sufficiently slow and noisy that most groundfish can readily escape. Groundfish that are caught include skates, sand lance, flatfishes, silver hake and monkfish, but in very small quantities (Roddick, 1996). There are no indications that cod is taken as a bycatch in this fishery9. With regard to the scallop fishery, it is known that there are groundfish bycatches and these were, at least in part, landed prior to 1996 and are recorded in landings statistics. A ban on landing groundfish (except monkfish) by scallop draggers was introduced in 1995 and thus there are no recorded landings since then. Presumably, there continued to be groundfish taken as bycatch but cod bycatches in recent years are thought to have been essentially zero10.
In summary, the available evidence does not indicate that there are substantial quantities on cod taken in 4VW as bycatch in other fisheries that are in addition to those already included in the official landings statistics. The scallop fishery is a possible exception.
Minimize the possibility of disruption of spawning and/or incidental mortality from seismic surveys for oil and gas:
The most recent review of the effects of seismic sound on fish and other marine species (DFO, 2004) found no documented cases of fish mortality from exposure to seismic sound under field conditions and concludes that such exposure is unlikely to result in direct fish mortality. The review concludes also that the behavioural changes in fish observed to occur are expected to be of little ecological significance except where they influence reproductive activity. Similarly, it found that the magnitude of mortality that might be caused to fish eggs and larvae is likely to be far below that which would be expected to affect populations. There are no unique features of cod biology that would make it an exception to the conclusions of the review that seismic surveys are unlikely to pose a high risk of mortality. It is pointed out, however, that there is a dearth of scientific information, particularly from field experiments, on the effects of sound on fish.
An integrated ocean management plan for the eastern Scotian Shelf is under development and the present draft of this plan (DFO, 2005) includes a strategy to minimize impacts from sources of acoustic energy by implementing a comprehensive set of mitigation measures for all types of seismic operations. Enough is known about sound in the marine environment to conclude that there are consequences for the fauna and, while these do not appear to be catastrophic in nature, such mitigation measures are warranted. A Canadian Statement of Practice to mitigate the effects of seismic sound in the marine environment was announced on 19 February 200511. This provides a vehicle for avoiding areas at times when finfish spawning is occurring to prevent dispersion of spawning fish and of migration corridors to avoid redirection of fish migration. The statement discounts the possibility of direct mortalities as an important factor, concerning itself only with population level effects.
Minimize the destruction of benthic habitat used by juvenile cod:
It is known that, in inshore areas, juvenile cod occur in heterogeneous areas where there is some vertical structure such as eelgrass, which reduces the risk of predation. COSEWIC assumes that, in offshore areas, juvenile cod are also associated with areas of physically heterogeneous bottom (COSEWIC, 2003). However, there is essentially no information to support this contention, and there is presently no basis on which to identify areas that could be designated critical habitat specifically for juvenile cod.
More generally, however, the present draft ocean management plan for the eastern Scotian Shelf (DFO, 2005) includes a strategy to implement an ecosystem/habitat conservation plan by incorporating benthic protection measures in relevant plans, such as fishing plans. These measures will be based on a benthic habitat classification system that identifies ecologically and biologically sensitive areas. It is likely that habitats rich in vertical structures such as coral beds will be primary candidates for protection and, indeed, there are already measures in place for this purpose.
Present knowledge about how the eastern Scotian Shelf ecosystem functions is rudimentary and the consequences of interventions are very uncertain. There is no guarantee that any actions taken will have a positive effect on cod. The practical possibilities for ecosystem manipulation are limited to actions that might reduce the natural mortality of cod. The above review of factors affecting recovery identified several potentially important sources of natural mortality in cod:
The hypothesis that predation of cod eggs and larvae by pelagic species is an important contributor to recruitment failure in cod is supported by the historical coincidence of events in the southern Gulf of St. Lawrence and by similar circumstantial evidence from the Northeast Atlantic, particularly in the Baltic Sea (Swain and Sinclair, 2000). However, it has not been demonstrated that predation by pelagic species on cod eggs and larvae in the southern Gulf of St. Lawrence has actually been sufficient to cause the reduction in cod recruitment that has been observed. In the case of the eastern Scotian Shelf, not only is the rate of predation on cod eggs and larvae unknown, the biomass of pelagic species is itself poorly quantified. Thus, research to quantify the importance of this issue in 4VW is certainly warranted. However, it is difficult to conceive of management actions that could reasonably be proposed at this time, in addition to those already in the management plans that control the exploitation of these pelagic species.
There is a stronger observational basis supporting the hypothesis that infection of cod by sealworm is a cause of mortality in juvenile and adult cod. Although the evidence for sealworm-induced mortality is actually for American plaice, it is a reasonable expectation that mortality would occur in other species also if infection rate was high enough. It would be useful to have up to date surveys that quantify the current high infection rates in cod that are being reported by fishermen. Although the rate of sealworm infection in fishes is affected by near-bottom water temperatures, infection seems to be related primarily to the distribution and abundance of grey seals (McClelland, 2002). Thus, reducing the population of grey seals has been the primary measure considered for control of parasite infections in groundfish. Unfortunately, there are still too many knowledge gaps to construct mathematical models that could give reliable insights into the effects of a reduced seal population on groundfish infection rates. In the few circumstances where seal herds have been reduced in number by 50% or more, no reductions in groundfish sealworm infection were observed (McClelland, 2002), giving no encouragement to the view that reducing the number of grey seals would reduce the sealworm problem. Recent developments in technology for the sustained-release of vaccines that would give seals a lasting immunity to sealworm infection are worthy of more research attention (McClelland, 2002).
Few predators of large cod have been identified but juvenile cod are preyed upon by a variety of other fish species, seals and whales. Grey seals are likely the most important predators of juvenile cod. A substantial amount of research has gone into understanding the interactions of grey seals and cod and this case is the only one of the three considered here that merits detailed consideration at the present time.
Reduce the abundance of grey seals:
Models of the effects of grey seal predation on eastern Scotian Shelf cod indicate that this was not a major factor in the early 1990s collapse of the 4VsW cod stock (Mohn and Bowen, 1996). However, the issue of whether grey seal predation could inhibit the recovery of cod remains an open question. The most recent cod stock assessment (Fanning et al., 2003) was based on the assumption that the total food consumption by the increasing Sable Island grey seal herd was about 310,000t in 2002 and incorporated new information on the proportion of cod in the seal diet. A new method has been developed to estimate the species composition of the seal diet called Quantitative Fatty Acid Signature Analysis (QFASA). QFASA determines the diet by comparing the fatty acids in potential prey with those found in a small sample of the seal's blubber. This method estimates diet composition over a previous period of weeks or months and thus should not be biased by where samples are collected, in contrast to previous estimates based on faecal samples from Sable Island. These earlier estimates of the proportion of cod in the grey seal diet of about 12% now appear to be too high for application to the population as a whole. In the most recent cod assessment, provisional estimates from QFASA supported an assumption that cod in the seal diet was 1% in recent years and thus that about 3100t of cod was consumed by grey seals in 4VsW in 2002.
Estimation of the diets of grey seals using the QFASA method are now complete for samples collected in 1993-2000 and results for 2004 samples will be available in the near future. This information, along with that from the most recent survey of population size on Sable Island (in 2004), are being used to construct new models of the effects of grey seal predation on eastern Scotian Shelf cod12.
The QFASA technique does not provide age composition estimates of the cod eaten by grey seals, in contrast to analysis of feacal samples, which provide fish otoliths for aging of the cod consumed. Based on these otoliths from feacal samples, ages 1 and 2 make up over 50% by weight (90% by numbers) of cod in the seals diet although ages up to 8 are included. The age composition from faecal samples may give an underestimate of the mortality caused to older cod, however, as it is possible that large cod attacked by seals may be only partially eaten (belly-feeding), and thus their otoliths would be under-represented in faeces.
The present modelling of cod/grey seal interactions, when completed, will provide new estimates of the mortality of cod due to predation by grey seals, but it is not expected that these new results will greatly change the present perception that this could be an important impediment to cod stock rebuilding. However, because of the complexity in grey seal feeding behaviour, reducing the grey seal population does not necessarity promise a reduction in cod predation. Stabilizing the grey seal population, if it were decided to do so, would likely require removals in excess of 50,000 animals annually, assuming the population continues to increase at its previous rate.
General principles:
The Groundfish Management Plan (DFO, 2002b) describes some of the limitations to the decision processes that have been used in the past and identifies the need for a set of decision rules that are consistent among all elements of the management plan, i.e. a more comprehensive decision framework. A decision framework sets out a logical set of criteria for making decisions about the management of any activities that affect the fish stocks in question. This promotes consistency in decision making from year to year and gives transparency to the decision process. Furthermore, having pre-agreed decision rules in relation to conservation issues is a requirement of the Precautionary Approach.
When stocks are at extremely low levels, as is the case of the cod stocks in 4VW at present, there may be widespread agreement that removals should be minimized. However, history shows that as soon as there is an indication of some improvement in stock status there will be advocacy for fishing to be reinitiated. Making a decision on the criteria to be used for fishery reopening prior to any improvements in stock status is likely to produce a more satisfactory result than decision making on an ad hoc basis at the height of controversy among interest groups with divergent opinions.
Relevant, reliable and up-to-date information is the key to good decision making. Scientists have, in the past, tended to define stock status in terms of spawning stock biomass and fishing mortality. It has been increasingly recognized that, while these are important factors to consider, it is necessary to take a broader spectrum of biological features into account. When stocks are at very low levels biological indicators are paramount in decision making but technical, economic, social and political considerations are also relevant and there is a need to develop ways to measure these too. While almost any product from a relevant data source may be proposed as an indicator, these 'candidate indicators' need validation before reliance can be put on them. Before a proposed indicator is accepted, a consensus needs to be developed about what the indicator means so that it can be properly interpreted in relation to stock or fishery status (see, for example, Halliday et al. (2001)).
Criteria are required for interpreting the information in data series, i.e. for deciding on whether the most recent data point can be considered 'good' or 'bad' news. The first step in doing this is to decide what indicator values would be expected in a fully recovered fish stock. These values are then used as reference points that allow the most recent values to be put in context. A recovered stock would be one where most or all of the indicators being used have values corresponding to a 'recovered' state. A recovering stock would be one that showed a progressive improvement over a number of years in most, if not all, indicators. Deciding on the indicators that are to be used and the setting of reference points for them is a matter for informed judgement.
Decision rules would determine the actions to be taken based on the values of indicators in relation to their reference points. It may be decided that the directed fishery will remain closed until most or all of the indicators show that reference points have been reached, i.e. until the stock is considered to be fully recovered, or a phase-in strategy may be preferred.
The formulation of decision rules provides the opportunity for enhancing shared-stewardship arrangements. All interested parties should have a say in developing this framework so that there is a general consensus on the criteria set13. The fishing industry has, for some years, been involved in stock abundance monitoring through sentinel and commercial index fisheries. There is scope for expanding the roles played by fishermen in relation to fishery reopening procedures.
Issues specific to 4VW cod stocks:
An issue identified above that deserves attention when formulating a management decision framework for the cod stocks in 4VW is whether the stock assessment / management units should be revised. The present units were established in the early 1970s and do not have a strong scientific foundation. There is a multiplicity of spawning components in 4VW (spring vs. autumn spawners; 4V vs. 4W; inshore vs. offshore), but it is only in 4Vn that any provision is made to assess and manage the local spawning component separately. The 4Vn situation has illustrated the limitations of trying to manage at the level of individual spawning components because of the extensive mixing with adjacent stocks, and there is no reason to expect that the situation would be more conducive to success elsewhere. Nonetheless, this complexity in cod stock structure will likely need to be recognized in recovery planning because there is no assurance that all spawning components will recover or, at least, not all at the same time. Thus, the spatial distribution of cod productivity within 4VW is an important factor to be taken into account when deciding on the conditions under which directed fishing is permitted. It has been proposed that a failure to protect sub-stocks has been an important factor in stock collapses and that a reduction in the space/time scales of fisheries management is required for success in future (Frank and Brickman, 2001).
The descriptions of the status of 4VW cod stocks given above illustrate that there is a fairly wide range of data series (indicators) available for use in decision rules. No decisions have yet been made, however, on which of these should be used, what weight particular indicators should be given or what values should be used as reference points.
Factors other than the status of the stock itself are also relevant to decisions on reopening of directed cod fishing. Bycatches are a primary ecosystem consideration. The implications of cod bycatch in other fisheries were discussed above. A reopening of directed cod fishing raises the issue of additional catches of other species, some of which may themselves be under strict controls on removals, e.g. haddock. The ability to ensure regulatory compliance is another key factor in decision-making. In particular, reopening of a cod fishery without there being confidence that a high level of accuracy of statistics on removals (landings and discards) can be obtained would be unacceptable.
Shared stewardship is seen as a central element of the new fisheries management policy for Atlantic coast fisheries14. It is the stated intention of DFO to encourage resource users, and the legitimate organizations that represent them, to assume a greater role in operational decision making. As noted above, the formulation of decision rules is one essential area for application of this policy. The success of a management decision framework is contingent on pre-agreement by all interested parties.
As part of the National Strategy for the Protection of Species at Risk15, the federal government established the Habitat Stewardship Program (HSP)16 for Species at Risk. Stewardship, in this context, refers to the wide range of voluntary actions that people are taking to care for the environment and is essential to the recovery of species at risk. The overall goal of the HSP is to "contribute to the recovery of …species at risk, and to prevent other species from becoming a conservation concern, by engaging Canadians from all walks of life in conservation actions to benefit wildlife." The HSP became operational in 2000-2001 and allocates up to $10 million per year to projects that conserve and protect species at risk and their habitats.
The HSP provides funding to stewards for implementing activities that protect or conserve habitats for species designated nationally as "at risk" (endangered, threatened or of special concern). As such, it supports many organizations and individuals in their efforts regarding the federal/provincial/territorial National Recovery Program17, the federal Species at Risk Act, as well as complementary provincial/territorial legislation. Many of the SARA's provisions (e.g. critical habitat, partnering and stewardship) are related directly to the HSP. In the context of management strategies for recovery of the cod stocks in 4VW, it would appear that a project could be proposed in order to involve various groups of fishermen in the recovery strategies identified above. Furthermore, the aboriginal fishermen involved in the Scotian Shelf groundfish fishery may be eligible to apply for access to more specialized funds, namely the Aboriginal Aquatic Resource and Oceans Management (AAROM) Program18 as well as the Aboriginal Fisheries Strategy19.
The preceding sections describe the history of the fisheries for the cod stocks in 4VW, the status of the stocks in relation to earlier years and the management system that is presently in place. They then discuss the factors that may be affecting recovery of the stocks, identify those where human intervention is possible and give an initial assessment of the scope for action. The possibilities for action now need to be examined in more depth and a consensus needs to be developed on the approaches that offer some prospect of success and are practical to implement, i.e. are cost-effective. To facilitate this, some draft recommendations are presented below. These are ordered by their priority. Consultations are required within DFO and among stakeholders to determine more precisely the scope for action and to make decisions on the actions that actually will be taken.
1. Develop a Management Decision Framework
There is no expectation of cod stock recovery in 4VW in the foreseeable future, and thus no sense of urgency among stakeholders to develop a management decision framework. However, stakeholders are best able to look at issues dispassionately under present circumstances, making this an ideal time to put such a framework in place. In any case, decision frameworks are being formulated for the cod stocks in the Gulf of St. Lawrence and off Newfoundland and Labrador and there will be strong pressure for a consistent approach for the eastern Scotian Shelf stocks. It is important that stakeholders in the eastern Scotian Shelf fisheries be participants in the process and have their views recognized.
A management decision framework for cod should encompass all elements of human activities that affect the status of cod stocks and the take account of the relationships between them. It does not equate simply to setting TACs for cod based on the results of stock assessments, although this is, of course, a core element. For example, it is essential that a surveillance and enforcement plan be an integral part of the framework, and that indicators of compliance are developed. The TAC level established should be a function of the level of regulatory compliance as well as of stock abundance and productivity. Also, it is particularly important, in the present case, to examine issues of stock structure and mixing and take these into account in deciding on an exploitation strategy.
Decision rules for setting TACs must be in conformity with the precautionary approach. A three-zone model is being proposed by DFO that requires definition of "healthy", "cautious" and "critical" zones. A stock in the healthy zone could be exploited under normal fishing conditions but one in the cautious zone would be subject to severe restrictions on exploitation. Removals from a stock in the critical zone would be minimized.
It is recommended that the following actions be taken:
1.1 That DFO Science be invited to draft a proposal for the biological elements of a Management Decision Framework for cod in 4VW that includes decision rules for TAC setting and that specifies:
1.2 That a DFO/Industry working group be charged with:
2. Reduce the abundance of grey seals
Present estimates are that more than 50,000 animals/year would need to be removed from the grey seal herd to cause a reduction in population size. Removing that number of animals raises a number of issues, practical, economical and political, that would need to be satisfactorily addressed before any actions were taken. There are also important scientific issues to consider; in particular, that there is a substantial uncertainty about whether reducing the grey seal population by such amounts would result in reduced predation of cod. It is recommended that any decision on grey seal population reduction be postponed until the results of new scientific analyses, that incorporate the most recent data on grey seal abundance and the contribution of cod to the seal diet, are available. The results of these analyses are expected within the next few months. The costs and benefits of reducing grey seal abundance should then be evaluated.
3. Minimize incidental mortalities
3.1 Recorded catches are fairly low and have declined in most recent years (Table 1). An important component of the fishing mortality in a number of years, for both stocks, has been from commercial index fisheries. As this activity has not produced any information that has proved useful for determining stock status in either area, it is recommended that these commercial index fisheries should be discontinued.
3.2 There is no evidence of there being significant removals of cod from 4VW that are not recorded in the statistical system and thus there is no immediate requirement to act. It is thought that present surveillance programs are adequate to detect an important change in reporting practices. There is not confidence, however, that present surveillance and enforcement programs would be capable of adequately quantifying and controlling cod removals if there was a significant improvement of cod stock status, or in the event of the haddock fishery being reopened. This longer-term issue is considered above as part of the management framework. More immediately, it is recommended that there be a review of at-sea observer program coverage of 4VW fisheries, invertebrate as well as groundfish, to ensure that the base levels are adequate to document present bycatches and to detect any major changes. This is particularly pertinent to the scallop fishery as there is higher uncertainty in that case than for other fisheries about present groundfish bycatches.
4. Shared stewardship
It is a central element of DFO fisheries policy to encourage resource users to take a bigger role in decision making at the operational level with associated increases in accountability and responsibility. There are also implicit costs to the industry under this policy associated with such activities as self-policing and information gathering. Reductions in DFO Science funding for Sentinel surveys, uncertainties about continuity in RV survey series and a reorientation of Science programs away from stock assessment attest to the urgency for the industry to take on an expanded role in relation to resource monitoring. It is recommended that ways to benefit from federal government funding under SARA-related programs, such as the Habitat Stewardship Program, be explored for projects related to 4VW cod recovery, and that other ways to fund data collection and analysis be explored.
5. Mitigation of Seismic Noise
The Statement of Canadian Practice for Mitigation of Seismic Noise of February 2005 provides for protection against disruption of cod spawning or migratory behaviour that could have negative effects at the population level, such as causing recruitment failure. There is no evidence to support a view that direct mortalities of either adults or eggs and larvae are sufficiently great to have population level consequences. As yet, the policy is not supported by practical procedures for its implementation, i.e. times and areas to be avoided by seismic surveys are not defined. While work on this is ongoing, the initiative presently lies with the oil and gas industry to define exclusion areas/times. It is recommended that the fishing industry, in consultation with DFO Science, develop their own views on the definition of locations and times of cod spawning aggregations (and any major migration corridors if such exist) in 4VW and propose that these be codified into the regulatory procedure for seismic surveying as areas/times to be avoided.
6. Protect Juvenile Habitat
Knowledge about the habitat of juvenile (ages 0-2) cod in offshore areas is inadequate to define locations that are of particular importance to their survival. However, the steps being taken to develop a benthic habitat classification system will provide a vehicle for protection of biologically sensitive areas such as those rich in vertical structure, i.e. those areas postulated to be important to juvenile cod. It is recommended that protection of potentially important juvenile cod habitat be given due consideration when deciding on the measures to be incorporated into fishing plans to protect heterogeneous areas of sea bed.
REFERENCES
Brander, K.M. 1995. The effect of temperature on growth of Atlantic cod (Gadus morhua L.). ICES J. mar. Sci., 52: 1-10.
Bundy, A., Fanning, L.P. (Submitted). Can Atlantic cod (Gadus morhua) recover? Exploring trophic explanations for the non-recovery of cod on the eastern Scotian Shelf, Canada. Can. J. Fish. Aquat. Sci..
Campana, S., Fanning, P., Fowler, M., Frank, K., Halliday, R.G., Lambert, T., Mohn, R., Wilson, S., Stobo, W., Hanson, M., Sinclair, A. 1995a. Report of the 4Vn cod working group on the scientific value of a 4Vn cod (May-Oct.) stock assessment. DFO Atlantic Fisheries Res. Doc., 95-16, 110pp.
Campana, S.E., Mohn, R.K., Smith, S.J., Chouinard, G.A. 1995b. Spatial implications of a temperature-based growth model for Atlantic cod (Gadus morhua) off the eastern coast of Canada. Can. J. Fish. Aquat. Sci., 52: 2445-2456.
Choi, J.S., Frank, K.T., Leggett, W.C., Drinkwater, K. 2004. Transition to an alternate state in a continental shelf ecosystem. Can. J. Fish. Aquat. Sci., 61: 505-510.
COSEWIC . 2003. COSEWIC assessment and update status report on the Atlantic cod Gadus morhua in Canada. Ottawa, xi + 76pp.
DFO . 2002a. Cod in Sydney Bight (Div 4Vn May-October). DFO Science Stock Status Report, A3-02 (2002) (Revised): 9pp.
DFO . 2002b. Groundfish Management Plan, Scotia-Fundy Fisheries, Maritimes Region, April 1, 2002 - March 31, 2007. Miscellaneous document, unpublished, 23pp + 8 annexes.
DFO . 2003a. Eastern Scotian Shelf cod. DFO Science Stock Status Report, 2003/020: 9pp.
DFO . 2003b. State of the Eastern Scotian Shelf ecosystem. DFO Ecosystem Status Report, 2003/004: 25pp.
DFO . 2004. Review of scientific information on impacts of seismic sound on fish, invertebrates, marine turtles and marine mammals. DFO Can. Sci. Advis. Sec. Habitat Status Report, 2004/002: 15pp.
DFO . 2005. Eastern Scotian Shelf Integrated Ocean Management Plan (2006-2011): Draft for Discussion. Oceans and Coastal Management Report, 2005-02: 81pp.
Dutil, J.-D., Lambert, Y. 2000. Natural mortality from poor condition in Atlantic cod (Gadus morhua). Can. J. Fish. Aquat. Sci., 57: 826-836.
Fanning, L.P., Mohn, R.K., MacEachern, W.J. 2003. Assessment of 4VsW cod to 2002. Canadian Science Advisory Secretariat (CSAS) Research Document, 2003/027: 41pp.
Frank, K.T., Brickman, D. 2001. Contemporary management issues confronting fisheries science. Journal of Sea Research, 45: 173-187.
Frank, K.T., Drinkwater, K.F., Page, F.H. 1994. Possible causes of recent trends and fluctuations in Scotian Shelf/Gulf of Maine cod stocks. ICES mar. Sci. Symp., 198: 110-120.
Halliday, R.G. 2002. A review of measures to control size at first capture of groundfish on the Scotian Shelf with special reference to haddock in NAFO Div. 4VW. Canadian Science Advisory Secretariat Research Document, 2002/100: 18pp.
Halliday, R.G., Fanning, L.P., Mohn, R.K. 2001. Use of the traffic light method in fishery management planning. Canadian Science Advisory Secretariat (CSAS) Research Document, 2001/108: 41pp.
Lambert, Y., Dutil, J.-D. 1997. Condition and energy reserves of Atlantic cod (Gadus morhua) during the collapse of the northern Gulf of St. Lawrence stock. Canadian Journal of Fisheries and Aquatic Sciences, 54: 2388-2400.
McClelland, G. 1995. Experimental infection of fish with larval sealworm, Pseudoterranova decipens (Nematoda, Anasakinae), transmitted by amphipods. Can. J. Fish. Aquat. Sci., 52 (Suppl. 1): 140-155.
McClelland, G. 2002. The trouble with sealworms (Pseudoterranova decipens species complex, Nematoda): a review. Parasitology, 124: S183-S203.
McClelland, G., Martell, D.J. 2001a. Spatial and temporal distributions of larval sealworm, Pseudoterranova decipens (Nematoda: Anisakinae), in Hippoglossoides platessoides (Pleuronectidae) in the Canadian Maritime Region from 1993 to 1999. NAMMCO Sci. Publ., 3: 77-94.
McClelland, G., Martell, D.J. 2001b. Surveys of larval sealworm (Pseudoterranova decipens) infection in various fish species sampled from Nova Scotian waters between 1988 and 1996, with an assessment of examination procedures. NAMMCO Sci. Publ., 3: 57-76.
Mohn, R., Bowen, W.D. 1996. Grey seal predation on the eastern Scotian Shelf: modelling the impact on Atlantic cod. Can. J. Fish. Aquat. Sci., 53: 2722-2738.
Mohn, R.K., Beanlands, D., Black, G.A.P., Lambert, T. 2001. Assessment of the status of 4Vn cod (May to October) 2000. Canadian Science Advisory Secretariat (CSAS) Research Document, 2001/105: 52pp.
Mohn, R.K., MacEachern, W.J. 1994. Assessment of 4VsW cod in 1993. DFO Atlantic Fisheries Res. Doc., 94/40: 37pp.
Rice, J., Rivard, D. 2003. Proceedings of the Zonal Assessment Meeting - Atlantic Cod. Canadian Science Advisory Secretariat (CSAS) Research Document, 2003/021: 133.
Roddick, D. 1996. The Arctic surfclam fishery on Banquereau Bank. DFO Atlantic Fisheries Research Document, 96/36.
Sinclair, A.F., Swain, D.P., Hanson, J.M. 2002a. Disentangling the effects of size-selective mortality, density, and temperature on length-at-age. Can. J. Fish. Aquat. Sci., 59: 372-382.
Sinclair, A.F., Swain, D.P., Hanson, J.M. 2002b. Measuring changes in the direction and magnitude of size-selective mortality in a commercial fish population. Can. J. Fish. Aquat. Sci., 59: 361-371.
Swain, D.P., Castonguay, M. 2000. Final Report of the 2000 Annual Meeting of the Fisheries Oceanography Committee including the Report of the Workshop on the Cod Recruitment Dilemma. Canadian Science Advisory Secretariat (CSAS) Proceedings Document, 2000/17: 105pp.
Swain, D.P., Sinclair, A.F. 2000. Pelagic fishes and the cod recruitment dilemma in the Northwest Atlantic. Can. J. Fish. Aquat. Sci., 57: 1321-1325.
Zwanenburg, K., Black, J., Mohn, R. 2002. Indices of fish distribution as indicators of population status. Canadian Science Advisory Secretariat Research Document, 23pp.
Table 1. Removals from 4Vn and 4VsW cod stocks by known causes (metric tons).
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2001 |
2002 |
2003 |
|
4Vn |
||||||||||
Bycatches |
39 |
14 |
28 |
43 |
61 |
97 |
68 |
134 |
39 |
27 |
Sent. survey |
18 |
29 |
10 |
13 |
36 |
44 |
14 |
11 |
15 |
7 |
Comm. index |
0 |
3 |
20 |
50 |
180 |
164 |
168 |
53 |
69 |
122 |
RV survey |
0.4 |
0.6 |
0.5 |
0.3 |
0.2 |
0.2 |
0.4 |
0.5 |
1.0 |
0.1 |
Total |
57 |
47 |
58 |
106 |
277 |
305 |
250 |
198 |
124 |
156 |
4VsW |
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Bycatches |
366 |
276 |
256 |
247 |
257 |
236 |
150 |
150 |
78 |
48 |
Sent. survey |
0 |
4.2 |
5.7 |
3.3 |
5.1 |
3.5 |
2.6 |
1.3 |
1.5 |
1.5 |
Comm. index |
0 |
0 |
46.7 |
77.2 |
12.0 |
57.6 |
4.3 |
8.6 |
10.5 |
0.1 |
RV surveys |
1.0 |
1.2 |
2.6 |
4.5 |
1.2 |
1.6 |
0.5 |
0.7 |
0.3 |
0.3 |
Total |
367 |
281 |
311 |
332 |
275 |
299 |
158 |
161 |
90 |
50 |
Table 2. Groundfish Management Plan Objective 1: Conservation of the Ecosystem. Strategies and management measures that pertain to 4VW. |
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General Objectives |
Strategies |
Management Measures |
1.1 Maintaining community diversity by protecting benthic communities susceptible to disturbance |
Protect high diversity coral beds |
(Lophelia Coral Conservation Area established on SE corner of Banquereau Bank, June 2004) |
Protect benthic communities in the Gully |
Establish The Gully as a Marine Protected Area (Designated May 2004) |
|
1.2 Maintaining species diversity |
Keep stock size of target species above established limits |
Control fishing mortality (F) |
Minimize incidental mortalities on non-target species, particularly species at risk |
Restrict directed catches and impose caps on bycatches |
|
1.3 Maintaining population diversity |
Maintain spawning components of target species |
Define management areas that correspond to stock distributions |
1.4 Maintaining trophic structure |
(Insufficient knowledge at this time to establish strategies) |
|
1.5 Maintaining productivity of populations by managing exploitation of target species |
Keep exploitation rates at moderate levels |
Control fishing mortality (F) through annual TACs and bycatch rules |
Avoid wastage by managing size and species selection during fishing |
- Specify aspects of gear construction, principally mesh size - Implement temporary and permanent closures of areas of small fish concentration - Restrict small-mesh groundfish fisheries to specified areas - Establish minimum fish size limits |
|
Prevent disturbance of fish during spawning |
Maintain previously established provisions (none in 4VW) |
Table 3. Bycatch limits in 4VW by fleet sector in Conservation Harvesting Plans for 2002-03. |
|
Fleet Sector |
Bycatch Limits |
Mobile>65' |
5% weekly with 2% overall cap for each of cod and haddock when directing for flatfish and /or redfish in 4VW. 10% weekly with 5% overall cap for cod and haddock combined when directing for pollock in 4VW. |
Mobile<65' |
By-catch provisions for each trip will be: 5% daily bycatch of each cod and haddock, with a 2% overall cap when directing for redfish and flatfish in 4VW. 10% per trip bycatch of cod and haddock combined, when directing for pollock in 4VW to a maximum 5% overall cap. |
Fixed 65'-100' |
10% daily for each of cod or haddock |
Fixed 45-65' |
The total bycatch of all species under moratorium will be restricted to a maximum cap of 10% when directing for other groundfish such as pollock or Atlantic halibut in 4VW. |
Fixed <45' |
The total bycatch of all species under moratorium will be restricted to a maximum cap of 10% when directing for other groundfish such as pollock, or Atlantic halibut in 4VW. |
Table 4. Summary of the measures in place in the groundfish fishery to prevent the capture of small groundfish in 4VW. |
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Measure |
Specific Aspect |
Requirements |
|
Gear regulations in large-mesh directed fisheries |
Mobile gear |
Cod/haddock/pollock |
130mm square mesh except diamond mesh allowed for pollock in 4VW if 155mm |
Flatfish |
155mm square mesh except 145mm diamond for Danish seiners in 4VW |
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Skates |
300mm (codend), 254mm (body) |
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Gillnets |
4VWX5Y |
140mm mesh or larger |
|
Line gears |
#12 circle hook or equivalent (#14 circle for boats over 65' in most areas) |
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Gear regulations in small mesh fisheries |
Silver hake |
Directed sp. |
55mm square mesh |
Bycatch spp. |
Separator grate with 40mm bar spacing |
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Redfish |
90mm mesh |
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Minimum size guidelines |
Cod, haddock and pollock |
<43cm |
|
White hake |
<43cm (fixed gear <45'), <45cm (fixed gear 65'-100'), no guidelines for other categories |
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American plaice and yellowtail flounder |
<30cm |
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Witch flounder |
<33cm |
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Atlantic halibut |
<81cm to be released alive |
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Greenland halibut |
<45cm |
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Redfish |
<22cm |
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Area closures |
Protect small haddock |
Emerald-Western banks (4W) closed year-round |
|
Fishing windows |
Protect small haddock |
Silver hake fishing restricted to defined windows in basins and on shelf slope |
Table 5. Average bycatch rates of cod in 4VW groundfish fisheries, 1994-2001, from DFO landings records.1 |
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Directed Species |
Directed Species Landings |
Cod Landings |
Percentage Cod of Directed Species |
4Vn (May-Oct.) |
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Atlantic halibut |
9 |
3 |
30.5 |
White hake |
70 |
10 |
13.7 |
Pollock |
118 |
5 |
4.3 |
Flatfish |
664 |
17 |
2.5 |
Redfish |
2293 |
2 |
0.1 |
4VsW |
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Atlantic halibut* |
273 |
28 |
10.2 |
Cusk |
78 |
7 |
9.4 |
White hake |
322 |
30 |
9.3 |
Dogfish |
37 |
2 |
5.1 |
Pollock* |
1108 |
46 |
4.2 |
Redfish |
3210 |
27 |
0.8 |
Flatfish |
1074 |
7 |
0.6 |
Skates |
994 |
1 |
0.1 |
Silver hake |
12220 |
1 |
0.01 |
*Includes directed haddock fishery by longline in Atlantic halibut directed fishery and by otter trawl in pollock directed fishery. Results of treating haddock as a separate fishery are: |
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Atlantic halibut |
271 |
20 |
7.3 |
Pollock |
1105 |
45 |
4.1 |
Haddock |
39 |
9 |
23.9 |
1
Note that this table summarizes the data in the DFO statistical database by main species caught in each sub-trip. This method identifies more directed fisheries than would be the case if the data were summarized by main species sought. However, data are not available by main species sought.
Fig. 1. NAFO Subdivisions 4Vn, 4Vs, and Division 4W.
Fig. 2. 4VsW cod: Nominal catches by Canadian and foreign fleets.
Fig. 3. 4VsW cod: Nominal catches by Canadian mobile and fixed gear fleets.
Fig. 4. 4VsW cod: Survey abundance indices – July RV (solid line), March RV (small dashes) and sentinel (large dashes). (Age 3+ for RV, 34 cm+ for sentinel, surveys.)
Fig. 5. 4VsW cod: Distribution indices from summer (top) and winter (bottom) surveys.
Fig. 7. 4VsW cod: Condition factor from July and March RV surveys for 4W and 4Vs cod (pseudo Fulton's K at 45 cm).
Fig. 6. 4VsW cod: Mean length at age 5 for 4Vs and 4W in summer research vessel surveys.
Fig. 8. 4VsW cod: Length at 50% maturity for females in 4Vs and 4W.
Fig. 9. 4VsW cod: Spawning stock biomass (based on q-corrected July RV survey estimates).
Fig. 10. 4VsW cod: Year class strengths (based on q-corrected July RV survey estimates at ages 1 and 2).
Fig. 11. 4VsW cod: Estimates of total mortality (Z) from July RV surveys (3yr running means).
Fig. 12. 4Vn (May-Oct) cod: Nominal catches by country (top) and by gear – all countries (bottom). (Note different time scales between panels.)
Fig. 13. 4Vn (May-Oct) cod: Abundance indices from July RV surveys (kg/tow) and sentinel surveys (kg/ 100,000 hooks).
Fig. 14. 4Vn (May-Oct) cod: Distribution index (stratified area occupied) from July RV surveys.
Fig. 15. 4Vn (May-Oct) cod: Mean length at age 5 in July RV surveys.
Fig. 16. 4Vn (May-Oct) cod: Condition factor (pseudo Fulton's K at 50 cm) from July RV surveys.
Fig. 17. 4Vn (May-Oct) cod: Spawning stock biomass (age 5+ biomass from SPA).
Fig. 18. 4Vn (May-Oct) cod: Recruitment at age 3 from July RV surveys.
Fig. 19. 4Vn (May-Oct) cod: Estimates of total mortality (Z) from July RV surveys.
Fig. 20. Temperature anomalies at 100 m depth on Misaine Bank, in 4Vs.
Fig. 21. Vertical density stratification in the top 50 m of the water column on the eastern Scotian Shelf.
Fig. 22. Abundance of grey seals on Sable Island.
Fig. 23. 4VsW cod: Recruitment rate (recruits/SSB).
Fig. 24. Pelagic species abundance in 4VW from summer RV surveys (top – Atlantic herring; middle – Atlantic mackerel; bottom – capelin). Note: dotted line indicates different vessel/gear used prior to 1982.
Fig 25. Phytoplankton abundance as measured by the colour index from CPR data for 4VW.
Fig. 26. Abundance of the copepod, Calanus finmarchicus, as measured by counts in CPR data in 4VW.
Fig. 27. Changes in mean length at age 5 for four groundfish species in 4VW.
Fig. 28. An index of fish condition for the groundfish species in 4VW.
Fig. 29. Seismic survey activity on the Scotia Shelf. (3D technology has more closely spaced survey lines than 2D.)
Fig. 30. Average landings (tons) by species group by cod management area, 1994-2001.
[1] A Special Concern species is defined as a species that is particularly sensitive to human activities or natural events but is not an endangered or threatened species. [ return to text ]
[2] http://www.sararegistry.gc.ca/the_act/SARA_e.pdf or Canada Gazette Part III, Vol. 25, No. 3, January 31 2003, 104pp.[ return to text ]
[3] Available from RAP Administrator, Science Branch, DFO Maritimes Region, BIO, Dartmouth, B2Y 4A2 Tel: (902) 426-7070. [ return to text ]
[4] Fishermen report that the increased catches of herring and mackerel in bottom trawl surveys on the offshore banks corresponded with a reduction in abundance inshore (interpreted as due to movement offshore) and a deepening of their distribution, which would make then more available to RV surveys. This suggests that the higher RV survey catches are, at least in some part, due to behavioural changes. [ return to text ]
[5] Note that Table 5 summarizes the data in the DFO statistical database by main species caught in each sub-trip. This method identifies more directed fisheries than would be the case if the data were summarized by main species sought. [ return to text ]
[6] Data provided by K. Zwanenburg, Science Branch, Scotia-Fundy Sector, Maritimes Region, DFO. [ return to text ]
[7] P. Koeller, Science Branch, Scotia-Fundy Sector, Maritimes Region, DFO; personal communication. [ return to text ]
[8] M. Biron, Science Branch, Gulf Sector, Maritimes Region, DFO; personal communication. [ return to text ]
[9] D. Roddick, Science Branch, Scotia-Fundy Sector, Maritimes Region, DFO; personal communication. [ return to text ]
[10] G. Robert, Science Branch, Scotia-Fundy Sector, Maritimes Region, DFO; personal communication. [ return to text ]
[11] http://www.dfo-mpo.gc.ca/media/newsrel/2005/scp-epc_e.htm [ return to text ]
[12] W. D. Bowen, Science Branch, Scotia-Fundy Sector, Maritimes Region, DFO; personal communication. [ return to text ]
[13] This is consistent with the rationale for public consultations about the potential social and economic impacts of SARA listings. See: DFO 2004. Legal listing consultation workbook, Atlantic Cod Maritimes population. 12 pp. [ return to text ]
[14] DFO 2004. Policy Framework for the Management of Fisheries on Canada's East Coast. [ return to text ]
[15] http://www.speciesatrisk.gc.ca/Q4_e.cfm [ return to text ]
[16] http://www.cws-scf.ec.gc.ca/hsp-pih/default_e.cfm [ return to text ]
[17] http://www.speciesatrisk.gc.ca/recovery/default_e.cfm [ return to text ]
[18] http://www.dfo-mpo.gc.ca/media/newsrel/2003/hq-ac99_e.htm [ return to text ]
[19] http://www.dfo-mpo.gc.ca/communic/fish_man/afs_e.htm [ return to text ]
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Last updated: 2005-12-15 |