Background to the Precautionary Approach framework

Transcription

1 Background to the Precautionary Approach framework Sustainable Fisheries Framework The Sustainable Fisheries Framework provides the basis for ensuring Canadian fisheries are conducted in a manner which support conservation and sustainable use. Conservation and Sustainable Use policies incorporate precautionary and ecosystem approaches into fisheries management decisions to ensure continued health and productivity of Canada s fisheries and healthy fish stocks, while protecting biodiversity and fisheries habitat. The Sustainable Fisheries Framework applies, and all the policies pursuant to it apply, to fishery decisions on a stock by stock basis. A Fishery Decision-Making Framework Incorporating the Precautionary Approach is one part of an overall Sustainable Fisheries Framework for Canadian fisheries. PA framework applies where decisions on harvest strategies or harvest rates for a stock must be taken on an annual basis or other time frame to determine Total Allowable Catch or other measures to control harvests. In applying the framework, all removals of these stocks from all types of fishing must be taken into account.

2 Background to the Precautionary Approach framework Three components to the general decision framework for the PA: Reference points and stock status zones (Healthy, Cautious and Critical) Harvest strategy and harvest decision rules, and Need to take into account uncertainty and risk when developing reference points and developing and implementing decision rules Wild Atlantic Salmon Conservation Policy (WASCP) identified the concept of lower and upper benchmarks against which to assess stocks status (DFO 2009) Focus of this meeting is part of the first component (definition of limit reference point and critical status zone)

3 Background to the Precautionary Approach framework Removal rate In resource management, the Precautionary Approach is, in general, about being cautious when scientific information is uncertain, unreliable or inadequate and not using the absence of adequate scientific information as a reason to postpone or fail to take action to avoid serious harm to the resource. PA framework is generally presented as a two-dimensional plot with three status zones (Critical, Cautious, Healthy) with stock status on the x-axis and removal rate on the y-axis Ciitical zone Cautious zone Healthy zone 0.6 Maximum removal rate Stock status

4 Background to the Precautionary Approach framework Removal rate Along stock status axis, the Limit Reference Point (LRP) defines boundary between the Critical and the Cautious stock status zones. Upper Stock Reference (USR) point defines boundary between the Cautious and the Healthy stock status zones. A removal reference is defined along the removal rate axis LRP USR 0.8 Ciitical zone Cautious zone Healthy zone 0.6 Maximum removal rate Stock status

5 Background to the Precautionary Approach framework Limit Reference Point defined as the stock level below which productivity is sufficiently impaired to cause serious harm (DFO 2009). Upper Stock Reference is the stock status level below which removals must be progressively reduced in order to avoid reaching the LRP. Removal reference is the maximum acceptable removal rate for the stock when the stock is in the healthy zone (includes all anthropogenic mortality) to comply with the United Nations Fisheries Agreement (UNFA), the Removal reference must be less than or equal to the removal rate associated with maximum sustainable yield When the stock is in the critical zone, management actions must promote stock growth and removals by all human sources must be kept to the lowest possible level.

6 Reference point for Atlantic salmon (conservation) Reference points have been used to provide advice for Atlantic salmon fisheries management since the 1970s. predates the development of the Sustainable Fisheries Framework (PA) 1977: the Canadian Atlantic Fisheries Scientific Advisory Committee (CAFSAC) Anadromous Subcommittee referred to the closure of commercial salmon fisheries and restriction in angling fisheries as responses to spawner abundances in two of the three major New Brunswick rivers (Saint John and Miramichi) declining to less than 25 percent of the estimated optimum spawning escapement 1978: referred to egg deposition rates to achieve smolt production potentials 1979: Symons estimated maximum production levels of 5 smolts per 100 m 2 for two year old smolts, 2 smolts per 100 m 2 for 3 year old smolts and 1 per 100 m 2 for 4 year old smolts would be achieved at egg deposition rates of 220, 165 to 220, and 80 per 100 m : existing data insufficient for providing detailed and accurate advice on management measures to optimize production on a river-by-river basis. achieving potential egg depositions of 200 per 100 m² of salmon rearing habitat or, where possible, at spawning levels associated historically with high levels of recruitment is adequate to conserve stocks and to retain future options

7 Reference point for Atlantic salmon (conservation) 1982: first priority was to satisfy resource conservation requirements to achieve optimum sustainable yield which was defined as the annual harvest in weight which can be taken from the stock year after year while maintaining stock size and allowing the greatest socio-economic benefits 1990: Supreme Court of Canada decision in the case of Regina vs Sparrow recognized that aboriginal peoples food fisheries have first right of access to natural renewable harvestable resources, once conservation was assured the court did not define conservation nor provide any guidance on how to determine when conservation needs were met 1991: CAFSAC - considered translating the definition as the spawning escapement below which CAFSAC would strongly advise that no fishing should occur. However, because this level cannot be defined with absolute precision, allowing the stock complex to fall to such a low abundance was regarded as involving unnecessary risks of causing irreversible damage to a resource s ability to recover in a reasonable period of time CAFSAC was not comfortable defining the point of serious harm (LRP)

8 Reference point for Atlantic salmon (conservation) 1991: CAFSAC provided reference level which would be synonymous with a precautionary reference level rather than LRP (my interpretation) CAFSAC, therefore, suggests as an operational translation of conservation the current target egg deposition rate of 2.4 eggs/m 2 of fluvial rearing habitat, and in addition for insular Newfoundland, 368 eggs/hectare of lacustrine habitat. (CAFSAC 1991a). The 2.4 eggs/m 2 reference level is assumed to provide a modest margin of safety for some instream adult losses between the time salmon enter into a river and subsequent spawning, as well as for disproportionate adult exploitation and unequal rate of recruitment of the multiple stocks comprising a river stock complex. CAFSAC considers that the further the spawning escapement is below the biological reference level, and the longer this situation occurs even at rates only slightly below that level, the greater the possibility exists of incurring the following risks, some of which may cause irreversible damage to the stock 1991 to the present : conservation objectives have been defined and treated as equivalent to a Limit Reference Point although management actions have not matched that definition

9 Conservation limits (CL) currently defined for eastern Canada Objective is to maintain spawning escapement above the conservation limit Maritimes : eggs per 100 m² of fluvial habitat (in some rivers, low gradient and very high gradient habitats are discounted) - To maximize freshwater production Newfoundland : eggs per 100 m² of fluvial area eggs per ha of pond area or 105 eggs per ha of pond area for northern peninsula - To maximize freshwater production Québec (developed a precautionary approach framework): adults - egg deposition that results in <25% of recruitment being < 50% of Rmax - upper stock reference: 95 th percentile of spawners that produced Maximum sustainable yield - habitat areas are weighted by habitat quality (units of production) Labrador: eggs per 100 m² of fluvial habitat - Areas for all rivers remain to be measured 9

10 Reconciling PA framework with fixed escapement and single reference point Priority of conservation over resource use enunciated in the Sparrow decision is consistent with the concept of a limit reference point as defined in the PA policy When CAFSAC (1991a) defined an operational translation of conservation, it seems to have been in the spirit of a target reference point (TRP); the further the spawning escapement was below the biological reference level, and the longer this situation occurred even at rates only slightly below that level, the greater the possibility of incurring risks of irreversible damage to the stock. Management of Atlantic salmon in Canada, Europe and internationally is based on a fixed escapement strategy, with all fish in excess of the conservation requirement considered surplus and available for harvest Current conservation limit and fixed escapement strategy for Atlantic salmon resembles the PA strategy within the critical zone and has no adjustments corresponding to the healthy zone

11 Removal rate Removal rate Reconciling PA framework with current fixed escapement and conservation requirement approach applied to date PA framework Fixed escapement / conservation requirement LRP USR 1 Conservation Maximum removal rate Stock status Stock status

12 Harvest Harvest Removal rate Removal rate Reconciling PA framework with current fixed escapement and conservation requirement approach applied to date exploitation rate (example) LRP USR fixed escapement strategy (all fish surplus to conservation are exploited) Conservation Maximum removal rate Stock status Stock status harvest (example) LRP USR Conservation Stock status Stock status

13 Escapement Escapement Reconciling PA framework with current fixed escapement and conservation requirement approach applied to date Spawners (after exploitation) LRP USR Conservation Stock status Stock status spawners increase into the healthy zone spawners are fixed above conservation

14 Science advisory report on concepts and approaches for defining reference points Describes and proposes candidate reference points Advises on the appropriateness of using reference points that are specific to variations in productivity Reviews analyses and values of reference points for Atlantic salmon Reviews and applies methods to transfer reference points

15 Candidate Limit Reference Points defined on the basis of conservation of the salmon population, unrelated to fishery exploitation objectives one strategy is to maintain sufficient numbers of adult returns despite wide variations in environmental conditions in the marine environment, to ensure adequate opportunity for expression of a diversity of adult phenotypes, and maintain genetic diversity. no hard and fast rules for defining such abundance levels but a number of candidate reference points could satisfy this objective S 0.5Rmax : spawner abundance that produces 50% of maximum recruitment S LRP : spawner abundance that results in a risk level of 25% or less of recruitment being < 50% Rmax S gen : spawner abundance that will result in recruitment to S MSY in one generation in the absence of fishing under equilibrium conditions S opt : spawner abundance that results in maximum potential surplus production (S msy )

16 Substantial evidence of sustained changes in some life history parameters of Atlantic salmon, particularly in survival at sea over the past 40 years Return rates of smolts to a first spawning have declined over the past two decades, with the most important declines occurring in the late 1980s and early 1990s Saint John Penobscott Weak evidence of productivity changes in freshwater as reported for marine environment (with exception of situations where freshwater habitat has been degraded; acid precipitation, barriers, siltation)

17 If productivity in freshwater is stationary, then limit reference points defined on the basis of maintaining freshwater production levels would be robust to variations in marine productivity reference points that are a proportion of the recruitment derived during the density dependent portion of the life cycle are appropriate (S 0.5Rmax ) Some reference points are not robust to variations in the marine survival (S 0.2B0, 0.4B MSY, S opt,) Objective should be to maintain freshwater production to take advantage of better marine productivity periods when they occur this may result in reduced harvest opportunities with more frequent and larger reductions in fisheries exploitation when marine survivals decline but the population will be at reduced risk of extirpation

18 Candidate Upper Stock Reference Points Choice of USR in large part determined by the choice of the limit reference point PA policy states : USR, at minimum, must be set at an appropriate distance above the LRP to provide sufficient opportunity for the management system to recognize a declining stock status and sufficient time for management actions to have effect while socio-economic factors may influence the location of the USR, these factors must not diminish its minimum function in guiding management of the risk of approaching the LRP. USR choice will depend upon the management objective for the resource (ex. maximize yield or fishing opportunities) 80%B msy : recruitment corresponding to 80% of R opt R opt (or B MSY ) : R max or portions of, interesting for recreational fisheries where catch and release opportunities can be maximized

19 Candidate Upper Stock Reference Points No recommendation for Upper Stock Reference Specific USR will depend upon the objectives of the fishery and the risk profile of the management strategy Upper stock reference points would best be determined using full life cycle considerations as recruitment could be subjected to reduced productivity and therefore increased risk of the stock falling to the LRP. At a minimum, the USR must be greater than the LRP There should be a very low probability (<5%) of the recruitment from the spawning stock at USR falling below the LRP

20 Candidate Removal Rate Reference Points UN Agreement of Straddling Fish Stocks and Highly Migratory Fish Stocks (FAO 1995) recommends that F MSY (fishing mortality at maximum sustainable yield) be used as a maximum removal rate and DFO (2009) indicates that the maximum removal rate in the healthy zone should not exceed the value corresponding to F MSY. Removal rate could be defined once the upper stock reference level is defined maximum removal rate would then be: h max = (R usr S usr )/ R usr.

21 Limit Reference Point : maintain production from freshwater to provide some assurance of sufficient numbers of adult returns to ensure the diversity of adult phenotypes and genetic variability at a minimum, the LRP (S LRP ) is defined as the abundance of spawners that results in less than 25% chance of recruitment (as smolts or adults) being less than half of maximum recruitment 25% risk level is provided as a default value in the absence of other guidance from management No recommendation for a specific Upper Stock Reference is made. choice depends upon the objectives of the users and the risk profile and risk tolerance of the management strategy at a minimum, the USR must be greater than the LRP and there should be a very low probability (<5%) of the recruitment falling below the LRP when the stock at USR is exploited at the maximum removal rate Maximum removal rate in the healthy zone should not exceed the removal rate at MSY (calculated once USR is defined)

22 Removal rate Candidate Reference Points for the PA More accustomed to thinking about salmon in terms of spawner recruit relationships with spawners on the x-axis and recruits on the y-axis PA framework has stock status on the x-axis (index of total abundance) and the removal rate on the y-axis Limit reference point (LRP) Upper stock reference (USR) 0.8 Ciitical zone Cautious zone Healthy zone 0.6 Maximum removal rate Stock status

23 Recruitment Example of a stock and recruitment relationship (Beverton-Holt) which can be used to define reference points 2,500 2,000 1,500 recruitment 1,000 1:1 (replacement) line 500 gain line (recruits spawners) ,000 1,500 2,000 2,500 Spawner abundance replacement point = 1627 spawners maximum recruitment ~ 1760 fish maximum gain ~ 745 fish recruitment at maximum gain ~ 1186 fish spawners for maximum gain ~ 441 fish exploitation rate at maximum gain = 0.63

24 Recruitment Example of a stock and recruitment relationship (Beverton-Holt) which can be used to define reference points 2,500 2,000 1,500 1, Recruitment Gain (yield) 80% Rmax Rmsy S50%Rmax Smsy ,000 1,500 2,000 2,500 Spawner abundance Candidate limit reference points spawners for 50% maximum recruitment (S50%Rmax) ~ 261 fish spawners for maximum gain (Smsy) ~ 441 fish Candidate upper stock reference points recruitment at maximum gain (Rmsy) ~ 1186 fish 80% of maximum recruitment (80%Rmax) ~ 1400 fish

25 Exploitation rate Recruitment Reconciling stock and recruitment relationship to Precautionary Approach framework (example) 2,500 2,000 1,500 USR Rmsy 1,000 Cmsy 500 Smsy 0 LRP ,000 1,500 2,000 2,500 Spawner abundance S50%Rmax Fmsy = Cmsy / Rmsy = (Rmsy Smsy) / Rmsy LRP USR Stock status (abundance before exploitation)

26 Conclusions Can move from single reference point and fixed escapement strategy to PA framework Need to check that the conservation value corresponds to a LRP LRP, USR and maximum removal rate are based on abundance before fishing, not spawners LRP as a minimum should be S 0.5Rmax, but can be higher USR can be defined once fisheries management objectives and risk tolerance are agreed Removal rate would be a direct calculation based on USR

27 Part II - Developing limit reference points for salmon populations of Gulf Region based on analyses used to develop the science advisory report of 2015 specific to limit reference points analyses use data from 14 rivers of eastern Canada with egg deposition and smolt production data has data from a limited number of years from Margaree River and Kedgwick River (Restigouche) use a Beverton-Holt stock recruitment relationship consider the consequences of three potential factors on the egg to smolt production dynamic presence of lacustrine habitat used by juveniles (present only in Newfoundland) mean smolt age (does time spent in freshwater affect density independent survival rate) proportion of eggs from MSW salmon (egg survival reported to be related to egg size, with survival of eggs from grilse < survival of eggs from MSW salmon, at least under hatchery conditions) proposed limit reference point (Slrp) is the egg deposition that results in a low probability (< 25%) that resulting recruitment will be < 50% of maximum recruitment

28 Egg to smolt monitoring locations and data sets used in the analyses Mean assessed smolt production Index River 1 Nashwaak 2 Big Salmon 3 Pollett 4 LaHave 5 Margaree 6 Kedgwick 7 Saint Jean 8 Trinite 9 Little Codroy 10 Conne 11 Rocky 12 NE Trepassey 13 Campbellton 14 Western Arm Brook

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30 Mean age (years) Latitude Lacustrine area (ha) Fluvial Lacustrine Western Arm Brook Campbellton NE Trepassey Rocky Conne Little Codroy Trinite Saint Jean Kedgwick Margaree LaHav e Pollett Big Salmon Nashwaak 5e+04 1e+05 2e+05 5e+05 1e+06 2e+06 5e+06 Fluvial area (m.sq.) summary of information available including: sizes of rivers and amount of lacustrine habitat years with data, and characteristics of salmon populations (mean age of smolts, prop. eggs form MSW) Spawning year fluvial habitat areas used are published values for Quebec, used rearing areas rather than units of production for compatability Proportion eggs from MSW

31 Smolts per 100 sq.m. Eggs (per 100 m² of fluvial habitat area) to smolt (per 100 m² of fluvial habitat area) data from fourteen rivers of eastern Canada Fluvial Lacustrine Eggs per 100 sq.m.

32 Smolts per 100 m² Eggs per 100 m² Stock (eggs per 100 m²) and recruitment (smolts per 100 m²) data from the 14 rivers of eastern Canada

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34 Slrp =

35 Slrp = Slrp =

36 Slrp =

37 Slrp =

38 Decisions to make - use the combined egg to smolt time series to derive the Limit Reference Point for southern Gulf populations (YES) - choice of model and biological covariates - use the model that includes presence/absence of lacustrine habitat use by juveniles for rearing (for southern Gulf rivers, use the output for fluvial areas only ) (YES) - mean smolt age covariate: limited information on this except for Miramichi, mean age likely in the range of 2.5 to 3.0 (NO) - proportion of eggs from MSW is more variable among populations, can infer this from intermittent monitoring, angling catches and some info on sex ratios (yes) - suggest this is the one we should use - examples: - Restigouche = 95%; 152 eggs per 100 m² - Northwest Miramichi (1992 to 2013) = 75%; Slrp = 174 eggs per 100 m² - Southwest Miramichi (1991 to 2013) = 89%; 154 eggs per 100 m² - Margaree (1988 to 1996) = 95%; Slrp = 152 eggs per 100 m² - mainland NS rivers - Morell River (PEI) = - if there are no data for a particular river on proportion of eggs from MSW, then use the LRP value for fluvial rivers on average (272 eggs per 100 m²) - because we are estimating a limit reference point, we should choose a value in the distribution which is higher than the median (50:50 chance). Propose using the 75 th percentile i.e. 1 chance in 4 that the LRP is actually higher than the value chosen (risk adverse for an LRP) (YES)

39 Part III LRP egg deposition values for rivers in Gulf Region - based on estimates of areas of rivers - currently using total wetted area estimates, some are coarse but usable - translating egg requirements to fish: - propose basing on principles of evolutionary history - egg requirements would be translated to fish requirements using population characteristics, including prop. of eggs from MSW value used to define Slrp - prop. from MSW = grilse are 20% female, MSW are 80% female - fecundity of female grilse = 3000, fecundity of MSW female = large salmon equivalent = 0.8 * Slrp.eggs /(fec.msw * prop.female.msw) - small salmon equivalent = 0.2 * Slrp.eggs / (fec.1sw * prop.female.1sw) - harvest decision rule and USR discussions will be based on same principles

40 For Quebec, new management measures announced March includes three status zones (like the PA) - healthy zone: populations not put in peril by a sustainable exploitation rate - cautious zone: abundance is less than optimal but not alarming, exploitation rate adjusted to favour rebuilding - critical zone: populations at low abundance and thus in peril, exploitation rate must be at lowest level possible.

41 Reference values - genetic limit reference: 90% chance of maintaining genetic diversity within 100 years. Any population with adult abundance < 200 fish is in the critical zone, no exploitation is allowed - demographic limit reference: spawner abundance (egg deposition) that results in 75% or greater chance of achieving 50% Rmax - upper stock reference: 95 th percentile of the posterior distribution of the MSY egg deposition rate - management targets: at the discretion of the managers, for example to favour catch and release opportunities (Rmax) rather than yield to harvests, by default must be greater than the upper stock reference

42 Revised reference value (eggs, ) 6.E+06 5.E+06 Upper stock reference Demographic LRP 4.E+06 3.E+06 2.E+06 1.E+06 0.E+00 0.E+00 1.E+06 2.E+06 3.E+06 4.E+06 5.E+06 6.E+06 Previous Conservation Limit (eggs, 1999 to 2015) Previous single conservation limit lies between the revised demographic LRP and the revised USR