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COSEWIC Annual Report - 2005

APPENDIX I

Report on the Marine Fish Workshop and Recommendations for COSEWIC

Halifax, Nova Scotia, 2-4 March 2005

Executive Summary

The purpose:

The mandate of the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) is to assess the status of species that are considered to be at risk of extinction in Canada. This workshop addressed concerns about how COSEWIC assesses the probability of extinction in marine fishes. The workshop participants provided their expert observations and recommendations for consideration by COSEWIC.

The theory: 

The COSEWIC definition for extinction seems appropriate. Some participants, however, questioned whether “extinction” should be used to refer to the disappearance of the last individual of a species, or the point at which numbers are so low that the species no longer plays an ecological role in its environment.

There are many examples of local extinctions of marine fish, although there are few examples of species-level extinctions. Marine fish are as vulnerable to extinction as other taxa at similar population levels and with similar life-history traits. Loss of populations is the first step towards global extinction. Even if there are millions of individuals left after a significant decline, they may still be at risk. The number of individuals remaining after significant population decline may not be as important as other life-history factors that affect the viability of the remaining population.

There was consensus that major ecosystem shifts have occurred following severe stock depletion. Examples were provided.

The data: 

It is important to include all available information in status reports and in assessments, recognizing the strengths and weaknesses of each type of information. For marine fish, data such as catch per unit effort for trends in abundance, age structure, age at maturity, sex ratios, and reconstructed biomass estimates from these metrics are useful. Other examples were provided. Special consideration should be given to species with particular habitat requirements.

There needs to be a cooperative approach during the preparation and review of species status reports; both COSEWIC and the jurisdictions involved can improve in key areas. 

  • Continue to ensure that jurisdictional data (inventories and analysis) are obtained and incorporated into status reports before COSEWIC assessment and SARA listing.
  • There was consensus that jurisdictions need to pay earlier attention to the candidate lists so that key information can be collected to support assessments and reduce uncertainty. 

The scientific community should be consulted as widely as possible (e.g., including fisheries assessment scientists outside of the Department of Fisheries and Oceans).

Community knowledge is a potentially important source of information. COSEWIC should investigate ways to access reliable community knowledge throughout its process.

The assessment process: 

COSEWIC’s process of assessing a species against quantitative criteria (including a decline criterion), and then considering other available information (such as age and size at maturity, vulnerability to fishing and Allee effect/inverse density dependence) is appropriate. Specific suggestions for enhancing these guidelines were provided.

COSEWIC should consider the work done by FAO, CITES, and NMFS on assessment criteria as part of its ongoing work to improve its assessment process. In particular, COSEWIC could consider the ‘modifying factors’ proposed by these groups, such as the role of extent of decline vs. rate of decline and the role of absolute population size relative to population decline. There was a difference of opinion regarding whether extent of decline (decline from a normal historic baseline) should be a modifying factor for the existing decline criterion (criterion A), a replacement for it, or an additional criterion.

Better communication by COSEWIC: 

The meaning of the term “risk of extinction” must be clarified. Risk refers to the probability of extinction. COSEWIC needs to better communicate what it means by “imminent” and “extinction” to ensure that all members of COSEWIC and the public understand what each assessment means.

It is important to provide better information on how COSEWIC operates, how it does its assessments and on the outcome of deliberations.

All sources of information considered and all sources of uncertainty in the assessment should be clearly presented in the status report. It would be very helpful if COSEWIC explained why certain criticisms and/or information obtained during the review process were not accepted as central to the status report and/or assessment.

Fisheries management vs. conservation: 

There is a need to clarify the relationships between reference points used in fisheries management and criteria used by COSEWIC.

1. Introduction 

1.1. About COSEWIC

The mandate of the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) is to assess the status of species that are considered to be at risk of extinction in Canada. The COSEWIC assessment process begins with the selection and prioritization of species requiring assessment, leading to the Prioritized Candidate list; continues with the compilation of available knowledge into the COSEWIC status report; and ends with the assessment of a species’ chance of extinction or extirpation and the COSEWIC status designation.

COSEWIC categorizes each species into one of six status categories: extinct, extirpated, endangered, threatened, special concern, or not at risk. COSEWIC uses quantitative criteria as a tool for assessing the probability that a species may become extinct. After application of the criteria, COSEWIC also considers rescue effect (immigration of individuals from other populations), significant life-history characteristics not addressed by the criteria (such as age at maturity, dispersal characteristics, longevity), threats, and consistency with its definitions of the status categories. The assessment process used at the time of the workshop is available at: http://www.cosewic.gc.ca/pdf/assess_proc_e.pdf

COSEWIC was designated as an advisory body under the Species at Risk Act (SARA). In this role, COSEWIC provides the results of its assessments to government to consider for legal listing. Legal listing of a species as extirpated, endangered or threatened leads to automatic prohibitions on killing or harming of a species, and to the preparation of recovery plans and action plans, or management plans. Although the government’s decision of whether to legally list a species also takes into account potential economic and social implications of legal listing, COSEWIC’s assessments, based solely on available knowledge, carry substantial weight.

1.2. The purpose and format of the workshop

There has been concern that the methods that COSEWIC uses to classify species according to probability of extinction do not work well for marine species. In particular, there appears to be disagreement over the suitability of the quantitative criteria for evaluating the probability of extinction in marine fishes (or other species with similar life-history traits).

Canada’s Minister of the Environment asked COSEWIC to hold a workshop to address concerns about the process that COSEWIC uses for assessing probability of extinction in marine species. That workshop was held in Halifax, Nova Scotia, Canada on 2-4 March 2005. It involved a variety of international experts on marine species and the use of quantitative criteria, including representation from COSEWIC, the Department of Fisheries and Oceans (DFO), the Government of Newfoundland and Labrador, industry representatives, non-government organizations, IUCN and other international experts (see Appendix 1).

The workshop began with a set of presentations on various topics of particular relevance to those assessing probability of extinction in marine species. The participants then formed four breakout groups, each tasked with a set of questions. Discussions within the breakout groups, and during plenary sessions, allowed the groups to refine their recommendations and comments for COSEWIC.

This report details the discussion topics and results of the workshop, with specific recommendations from the participants: a) to assist COSEWIC in its assessment process and to improve upon the data used to assess marine fish species; b) to improve the means by which COSEWIC communicates its objectives and results; and c) to identify topics for further consideration by COSEWIC.

2. Presentations

Eleven presentations on the first day of the workshop informed the participants of various perspectives regarding the assessment of marine species, provided history and context for using quantitative criteria in assessing species (by  COSEWIC and other organizations such as IUCN and CITES) and investigated some of the diversity within marine species with respect to probability of extinction. This allowed the participants to establish a common terminology and basis for subsequent discussions in breakout groups and during the plenary sessions.

Abstracts for each of the presentations are provided in Appendix 2.

3. Discussion Topics and Recommendations

The intention of the workshop was not to achieve consensus on all the topics discussed. Rather, each working group was tasked to identify areas of uncertainty, note consensus or disagreements and, when possible, provide recommendations to COSEWIC for consideration.

3.1  Which data are useful to assess the probability of extinction in marine fish?

Issue:  While there are many different types of data available for assessing the chance of extinction in marine fish, not all may be equally useful.

Questions:  What data are available to assess extinction probability in marine fish (e.g., scientific surveys, catch statistics, morphometric data, and age ratios)? What is the minimum time series required for estimating probability of extinction?  What are important sources of uncertainty? What are the strengths, weaknesses and relative values of different sources of information?

Data to use in assessing extinction probability of marine fish:

It is important include all available information (including DFO or industry or other stock assessments).

Recognize strengths and weaknesses of different types of information (not all data provide equally appropriate metrics of distribution and abundance):

  • Both fisheries-dependent and fisheries-independent data have to be considered. Fisheries-dependent data generally are nonlinear indicators of decline in targeted species but can, in some cases, provide useful metrics of abundance for non-targeted species; fisheries-independent data (scientific surveys) generally are the most useful metrics of abundance and distribution, although their limitations and potential biases (e.g., coverage, catchability) need to be recognized.
  • Context is needed for interpreting fisheries-dependent data (what variables may drive the trends, changes in fish abundance, changes in gear, effort, market price etc.).  All available data (including both fisheries-dependent and fisheries-independent data) should be presented in COSEWIC status reports with a discussion (if required) of their relative merit.

Specific types of data that are most useful for assessment of temporal changes in abundance, distribution, and population status include:  catch per unit effort (CPUE) for trends in abundance, age structure, age at maturity, sex ratios, and reconstructed biomass estimates resulting from these metrics. However, in most cases, CPUE from directed fisheries is well known to be non-linearly related to actual abundance of the target species. This nonlinearity occurs in such a way as to underestimate the amount of decline in actual abundance.

Community knowledge is a potentially important source of information. COSEWIC must improve its communication with the fishing industry early in the assessment process and seek useful information that the industry may provide.

The scientific community should be consulted widely as possible, including fisheries assessment scientists outside of DFO.

Assessment of probability of extinction should give special consideration to species with special habitat requirements, especially:

  • Anadromous species;
  • Species that are estuarine-dependent; and
  • Species whose marine habitats are potentially vulnerable to physical disturbance, especially habitats essential for critical life-history stages.

Documenting sources of data and uncertainties

All sources of information considered should be clearly presented in the status report. It would be very helpful if COSEWIC explained why certain criticisms and/or information obtained during the review process were not accepted as central to the status report and/or assessment.

Identify all sources of uncertainty (e.g., differences in coverage of surveys and the range of the species, type of habitat, as well as the timing of the survey).

3.2  Should we apply the decline criterion to marine fish whose populations still number in the millions? 

Issue:  Of the five quantitative criteria used by COSEWIC, the decline criterion (http://www.cosewic.gc.ca/pdf/assess_proc_e.pdf , Table 2, Criterion A) is most commonly applied to marine fish. This criterion has been criticized as being inappropriate for commercially exploited marine fish because the threshold values in the COSEWIC guidelines are thought by some to result in placement in a status category when the probability of extinction is not sufficient to warrant concern. Another contentious issue concerns the appropriate means of estimating decline and the time period over which the decline is quantified.

Questions: What is the justification for using a 50 or 70% population decline as a reference point? How should the distribution and the dispersion of the remaining fish be considered in assessments?  What reference points should be used when estimating decline, e.g., decline in relation to what past level of abundance?  Over what period of time should the decline be quantified?

The assessment process

As part of COSEWIC’s ongoing work to improve its assessment process, the work done by FAO, CITES and NMFS on assessment criteria should be considered further (e.g., FAO 2001; Mace et al. 2002).

 A decline criterion has a legitimate role in assessing probability of extinction. In COSEWIC’s process, it functions as a starting point for discussion about the status of the species, and that discussion includes consideration of all other available information. This is an appropriate use of all the criteria, including the decline criterion.

Modifying factors

COSEWIC should undertake a careful consideration of potential modifying factors to be used in interpreting decline criteria.

Several modifying factors can be taken into account in interpreting the decline criterion (or other criteria; e.g., absolute numbers, genetic diversity, vulnerability to disease). The relevance of modifying factors will be case specific, as will the availability of information.

The absolute population size is a factor to consider in interpreting the degree to which a given decline provides a reliable metric of extinction probability. Some participants felt that the appropriate critical values for absolute remaining population size (criterion C) generally should be much larger for many marine fish species than for many other taxa (e.g., FAO 2001).

The interpretation of absolute population size should consider other modifying factors because population size alone is not sufficient for evaluating probability of extinction. The relationship of absolute population size to effective population size should be clarified in assessments, in cases when they are unlikely to be similar.

In interpreting the absolute population size relative to a population’s decline, the degree to which the decline is continuing should have a great deal of weight. The weaker the evidence that the rate of decline is decreasing as the abundance declines, the less importance should be given to how many individuals are left. Also, the steeper the slope of the decline overall, the less weight should be given the remaining population size.

Extent of Decline vs. Rate of Decline

Extent of decline:  Extent of reduction should be calculated from the average unfished (historic) baseline and not from a recent short-term peak. Use as long a time series as possible, which may mean using multiple information sources to establish a baseline.

Rate of decline:  Decline in recent years or recent generations (used in COSEWIC quantitative criteria, http://www.cosewic.gc.ca/pdf/assess_proc_e.pdf, Table 2).

There was a difference of opinion regarding whether extent of decline from the historic baseline should be a modifying factor for the existing decline criterion (criterion A), a replacement for it, or an additional criterion. There was agreement that the history of the population and particularly its exploitation history will be important to interpreting the degree to which extent or rate of decline are informative about the probability of extinction.

Because of the diversity of interpretations of “decline” (e.g., extent of decline vs. rate of decline), each status report should make clear which one is being used.

The Interface of Management and Conservation

There is a need to clarify the relationships between reference points used in fisheries management and criteria used by COSEWIC, and where possible, to harmonize them. Many participants argued that it is important to ensure that the zones for threatened and endangered do not overlap the zone of fisheries management reference points. Others argued that, at least in some cases, there is no need for this concern, as commercial exploitation would have ended already by the time a population decline triggered assessment by COSEWIC (Dulvy et al. in press). How close the boundaries between fisheries management reference points and criteria used by COSEWIC should be is a crucial question with both a science and a policy component. The group had neither consensus on how close they should be, nor necessarily even if a scientific basis for positioning exists.

3.3 What is the evidence for large-scale or local extinction of marine fish?

Issue:  There are few recorded extinctions of entire species.

Questions:  What do we really mean by 'extinction'?  At what point does a 'management' problem become a 'conservation' concern because recovery becomes unlikely?  What factors affect recovery rates?  What is the evidence for major ecosystem shifts following severe stock depletion? Do the life-history characteristics of marine fish make them less likely to become extinct than other taxa for a given population size?

The COSEWIC definition for extinction seems appropriate (a wildlife species that no longer exists). Some participants, however, questioned whether “extinction” should be used to refer to the disappearance of the last individual of a species, or the point at which numbers are so low that the species no longer plays an ecological role in its environment. “Imminent” probability of extinction can be informed by COSEWIC’s criterion E (e.g., 20% chance of extinction in the longer of 20 years or 5 generations; http://www.cosewic.gc.ca/pdf/assess_proc_e.pdf)

There are many examples of local extinctions of marine fish. There are few examples of species-level extinctions (Dulvy et. al 2003). It should be noted, however, that because many marine fish species are widely distributed, “local” extinctions can occur at a large scale.

The ability to predict future population trajectories often declines as the size of the population declines, so uncertainty increases. A precautionary approach should be used in such cases.

Zones of unacceptable risk to fisheries (outside biological stock abundance limits) overlap with higher probability of extinction and possibly low likelihood of recovery; recruitment can be impaired.

Likelihood of recovery is difficult to predict, however, we can identify conditions that need to be met for recovery to occur.

There was consensus that major ecosystem shifts have occurred following severe stock depletion. Examples discussed included dramatic increases in the abundance of shrimp following the collapse of Atlantic cod throughout much of the North Atlantic (Worm and Myers 2003), and increases in pelagic fish concomitant with declines in the abundance of groundfish (Hutchings and Baum 2005).

Communication of processes and results

COSEWIC needs to better communicate what it means by “imminent” and “extinction” to ensure that all members of COSEWIC and the public understand what each assessment means. Both terms are already defined by COSEWICCOSEWIC should strive for better communication of its processes and assessments:

  • The process COSEWIC uses to derive a status assessment (i.e., use of quantitative guidelines followed by expert opinion decision-making; http://www.cosewic.gc.ca/pdf/assess_proc_e.pdf) seems appropriate;
  • Provide more comprehensive and detailed reason for a species’ designation, capturing the essence of the discussion at the assessment meeting, and how different information sources contributed to conclusions. The reason for designation should also emphasize importance of the species to biodiversity;
  • Better explanation of the COSEWIC process should be reflected in the FAQs on the COSEWIC website;  and
  • Explain any relationship between designatable units and management units so that people understand the assessment better.

COSEWIC should communicate why some criticisms and information obtained during the review process are not accepted as central to the status report and/or assessment.  A written response on main issues raised by jurisdictions could be provided. Significant divergences of scientific interpretation should be addressed in the report.

Improving the review process to increase the quality of reports and assessments

COSEWIC should continue to ensure that all available data are incorporated into reports:

  • There needs to be a cooperative approach during the preparation and review of species status reports; both COSEWIC and the jurisdictions involved can improve in key areas. 
  • o       Continue to ensure that jurisdictional data (inventories and analysis) are obtained and incorporated into status reports before COSEWIC assessment and SARA listing.
  • o       There was consensus that jurisdictions need to pay earlier attention to the candidate lists so that key information can be collected to support assessments and reduce uncertainty. 
  • Six-month interim reports should be provided to a broad range of experts to ensure that no relevant data or interpretations are overlooked.
  • COSEWIC needs to investigate ways to access reliable community knowledge throughout its process (e.g., using accepted social science methodology, atlas programs that have been established for birds, Fisherman Research Society in Nova Scotia, sociological studies looking at different fishing patterns through time).
  • Engagement of community and other stakeholders will increase the confidence that stakeholders have in the COSEWIC species assessment process.

The life-history characteristics of marine fish do not make them any less likely to become extinct than other taxa.

There is much variability in probability of extinction for marine fish: low-productivity species such as sharks, skates and rays are predicted to have higher extinction probabilities than high-productivity species such as herring (Hutchings 2001a,b; Dulvy et al. 2003). There is some archaeological evidence that marine fish haven’t become extinct as often as other species (McKinney 1997). However, there should not be complacency about marine fish extinction.

Important life-history and other ecological characteristics to consider for marine fish include:  habitat, life history (including very low fecundity for some species), genetic drift, susceptibility to bycatch, concentrated and predictable spawning locations, Allee effect, environmental variability, multi-species interaction (e.g., Reynolds et al. 2002; Dulvy et al. 2003; Hutchings and Reynolds 2004; see also section 3.4).

3.4  What life-history and other ecological characteristics of marine fish affect their probability of extinction?
Questions:  Fecundity?  Age at first reproduction?  Use of certain habitats?  Susceptibility to different fisheries?  Trophic level?  How should these variables be included in an assessment of probability of extinction?

Marine fish are as vulnerable to extinction as other taxa at similar population levels and with similar life-history traits. There was consensus that even though marine fish have highly diverse life-history characteristics, they are not different from other taxa with regard to this diversity. Additionally, there is no reason to believe that marine fish species are any more or less resilient than other taxa in their responses to threatening processes, including exploitation, habitat loss, environmental changes, and pollution. There is no evidence that highly fecund species are any more resilient than less fecund species. Life-history traits such as body size and age at maturity can be used to predict vulnerability of fishes to specific threatening processes, in the same way that they predict vulnerability of terrestrial species (Reynolds 2003).

Loss of populations is the first step towards global extinction. There are a few hundred documented examples of local marine fish extinctions (although the various causal factors, including fisheries, have not been established in many cases), but very few examples of species extinctions  (Dulvy et al. 2003). However, normally, loss of populations is the first step towards global extinction. Although it is difficult to scale-up local losses to global extinction in widespread species of marine fishes, it is conceptually no different from making similar extrapolations in other taxa.

Even if there are millions of individuals remaining after a significant decline, the population may still have a high chance of becoming extinct. The number of individuals remaining after a population decline may not be as important as other factors. For example, the viability of the remaining population may be affected by size of individuals, condition, age and size at maturity, viability of eggs, recruitment rate, spatial distribution and population structure of remaining individuals, and by how these variables change over time.

COSEWIC’s application of the life-history guidelines is an integral part of the assessment process (http://www.cosewic.gc.ca/pdf/assess_proc_e.pdf, Table 5). However, the guidelines can be enhanced:

  • There is no evidence that high fecundity makes fish populations particularly resilient to, or likely to recover from, human impacts (Sadovy 2001). Therefore fecundity should not be used as part of the criteria for assessing vulnerability to extinction or potential for recovery. (Add this as footnote to Table 5)
  • The level of threat to important habitats for various life stages is an important consideration during the assessment, but it is particularly weakly documented for nearly all marine species.
  • In its assessments, COSEWIC should continue to consider effective conservation, protection and management measures that may be in place.
  • Species that aggregate at certain stages of their life cycles are potentially vulnerable to human impacts, e.g., during spawning or overwintering, or in nursery areas; COSEWIC already considers these factors when calculating Area of Occupancy (A of O; tables 2 and 3), but may need to highlight this explicitly when A of O is not part of the quantitative criteria that apply to a particular species.

4. References

Dulvy, N.K., Jennings, S.J., Goodwin, N.B., Grant, A., & Reynolds, J.D. in press. Comparison of threat and exploitation status in Northeast Atlantic marine populations. Journal of Applied Ecology.

Dulvy, N.K., Y. Sadovy and J.D. Reynolds. 2003. Extinction vulnerability in marine populations. Fish and Fisheries 2003: 25-64.

FAO 2001. A background analysis and framework for evaluating the status of commercially exploited aquatic species in a CITES context. Second technical consultation on the suitability of the CITES criteria for listing commercially-exploited aquatic species, Windhoek, Namibia, 22-25 October 2001, Food and Agriculture Organization of the United Nations. FI: SLC2/2001/2: 19 pp.

Hutchings, J.A. 2001a. Conservation biology of marine fishes: perceptions and caveats regarding assignment of extinction risk.  Can. J. Fish. Aquat. Sci. 58: 108-121.

Hutchings, J.A. 2001b. Influence of population decline, fishing, and spawner variability on the recovery of marine fishes.  J. Fish. Biol. 59 (Suppl. A): 306-322.

Hutchings, J.A. and J.D. Reynolds. 2004. Marine fish population collapses:  consequences for recovery and extinction risk. BioScience 54:297-309.

Hutchings, J.A., and J.K. Baum. 2005. Measuring marine fish biodiversity: temporal changes abundance, life history and demography.  Phil. Trans. R. Soc. 360: 315-338.

Mace, P.M., A.W. Bruckner, N.K. Daves, J.D. Field, J.R. Hunter, N.E. Kohler, R.G. Kope, S.S. Lieberman, M.W. Miller, J.W. Orr, R.S. Otto, T.D. Smith, N.B. Thompson, J. Lyke and A.G. Blundell. 2002. NMFS / Interagency Working Group Evaluation of CITES Criteria and Guidelines. U.S. Department of Commerce, NOAA Technical Memorandum NMFS-F/SPO-58, 70 pp.

McKinney, M.L. 1997. Extinction vulnerability and selectivity: combining ecological and paleontological views. Ann. Rev. Ecol. Syst. 28:495-516.

Reynolds, J.D. 2003. Life histories and extinction risk. In: Macroecology (eds. T.M. Blackburn& K.J. Gaston), pp. 195-217.  Blackwell Publishing, Oxford.

Reynolds, J.D., N.K. Dulvy, and C.R. Roberts. 2002. Exploitation and other threats to fish conservation. In: Handbook of Fish Biology and Fisheries: Volume 2, Fisheries (eds. P.J.B. Hart & J.D. Reynolds), pp. 319-341.  Blackwell Publishing, Oxford.

Sadovy, Y. 2001. The threat of fishing to highly fecund fishes. J. Fish. Biol. V. 59(Supp. A): 90-108.

Worm, B., and R.A. Myers. 2003. Meta-analysis of cod-shrimp interactions reveals top-down control in oceanic food webs.  Ecology 84: 162-173.