Canadian Science Advisory Secretariat Secrétariat canadien de consultation scientifique Research Document 2009/088 Document de recherche 2009/088

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1 C S A S S C C S Canadian Science Advisory Secretariat Secrétariat canadien de consultation scientifique Researc Document 2009/088 Document de recerce 2009/088 Pacific sardine (Sardinops sagax) biomass and migration rates in Britis Columbia Biomasse et taux de migration de la sardine du Pacifique (Sardinops Sagax) en Colombie-Britannique J. Scweigert, G. McFarlane, and V. Hodes Fiseries and Oceans Canada Science Branc Pacific Biological Station Nanaimo, B.C. V9T 6N7 Tis series documents te scientific basis for te evaluation of aquatic resources and ecosystems in Canada. As suc, it addresses te issues of te day in te time frames required and te documents it contains are not intended as definitive statements on te subjects addressed but rater as progress reports on ongoing investigations. Researc documents are produced in te official language in wic tey are provided to te Secretariat. La présente série documente les fondements scientifiques des évaluations des ressources et des écosystèmes aquatiques du Canada. Elle traite des problèmes courants selon les écéanciers dictés. Les documents qu elle contient ne doivent pas être considérés comme des énoncés définitifs sur les sujets traités, mais plutôt comme des rapports d étape sur les études en cours. Les documents de recerce sont publiés dans la langue officielle utilisée dans le manuscrit envoyé au Secrétariat. Tis document is available on te Internet at: Ce document est disponible sur l Internet à: ttp:// ISSN (Printed / Imprimé) ISSN (Online / En ligne) Her Majesty te Queen in Rigt of Canada, 2010 Sa Majesté la Reine du Cef du Canada, 2010

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3 Correct citation for tis publication: Scweigert, J., McFarlane, G., Hodes, V Pacific sardine (Sardinops sagax) biomass and migration rates in Britis Columbia. DFO Can. Sci. Advis. Sec. Res. Doc. 2009/088. iii + 14 p. ABSTRACT Te Pacific sardine (Sardinops sagax) is a transient visitor to Canadian waters, annually migrating nortward from spawning grounds off soutern California. As te sardine population as rebuilt over te past few decades, te abundance of fis migrating into Britis Columbia waters as increased, as as interest in arvesting tem. Te difficulty in developing a arvest policy for sardines in Canadian Pacific waters is te uncertainty in te annual migration rate of te coastwide stock into Britis Columbia. Ware (1999) estimated te migration rate of sardine into Canadian waters based on te catces taken in te istorical fisery and proposed a arvest policy based on te United States assessment model and assuming an annual 10 percent migration. A trawl survey as been conducted off te west coast of Vancouver Island since 1997 to monitor sardine abundance and distribution in Canadian Pacific waters wit an objective of providing updated estimates of sardine distribution and migration rate. Based on our re-analysis of te available information on te sardine abundance in Canada from te trawl survey conducted on te west coast of Vancouver Island, we believe tat te currently assumed arvest rate is conservative and sould be updated. Based on te five years for wic a compreensive survey was conducted te average migration rate estimate is18.3 percent. Given tat te survey region does not cover te known distribution of sardines in Canadian waters (suc as te inlets of te west coast of Vancouver Island and Queen Carlotte Sound), tis provides a precautionary estimate of migration for determining allowable arvest. RÉSUMÉ La sardine du Pacifique (Sardinops sagax) visite caque année dans les eaux canadiennes lorsqu elle quitte les aires de frai au large de la Californie pour migrer vers le nord. La population de sardine s étant reconstituée au cours des dernières décennies, l abondance des individus migrant dans les eaux de la C.-B. a augmenté, tout comme l intérêt pour l exploitation de cette ressource. La difficulté associée à l élaboration d une politique sur la pêce à la sardine dans les eaux canadiennes réside dans l incertitude entourant le taux de migration annuelle du stock côtier en Colombie-Britannique. Ware (1999) a estimé le taux de migration des sardines dans les eaux canadiennes selon les prises réalisées dans le cadre de la pêce istorique et a proposé une politique de pêce fondée sur le modèle d évaluation américain, d après un taux de migration annuelle de 10 %. Depuis 1997, on effectue un relevé au calut au large de la côte ouest de l île de Vancouver afin de surveiller l abondance et la répartition des sardines dans les eaux canadiennes et ce, dans le but d établir des estimations à jour de la répartition de l espèce et du taux de migration. Selon notre nouvelle analyse de l information concernant l abondance des sardines au Canada dérivée du relevé au calut effectué sur la COIV, nous croyons que le taux d exploitation actuel est conservateur et qu il pourrait être mis à jour. Selon les relevés détaillés effectués au cours des cinq dernières années, on estime le taux de migration moyen à 18,3 %. Étant donné que ces relevés ne couvrent pas l ensemble de l aire de répartition connue des sardines dans les eaux canadiennes, tels que les bras de mer de la COIV et le détroit de la Reine-Carlotte, l estimation de la migration pour établir le niveau de prélèvement autorisé est prudente. iii

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5 INTRODUCTION Te Pacific sardine (Sardinops sagax) is a transient visitor to Canadian waters, migrating nortward from spawning grounds off soutern California in te spring to te ric feeding grounds off Vancouver Island and returning sout in te fall. Sardines were fised extensively in te Pacific Nortwest during te first alf of te 20 t century, disappearing entirely from tis area by te late 1940s. After an absence of almost 50 years, sardines reappeared in Canadian waters in 1992 (Hargreaves et al., 1994, McFarlane and Beamis 2001). As a result, tere as been some debate about sardine spawning in Canadian waters and te possible existence of a nortern sardine stock. Hart (1973) reports observations of sardines wit loose eggs in Canadian waters, owever spawning was not observed. A more recent survey (1997) reports te collection of ripe females near Vancouver Island along wit juvenile sardines (McFarlane and Beamis 2001). Bot istorically (Hart 1937) and in recent years (McFarlane et al., 2005; Scweigert, pers.obs.), tere as been evidence of sardines over-wintering in waters off te west coast of Vancouver Island rater tan migrating sout in te fall. Wintering fis ave been found in inlets and some scools appear to ave been trapped in warm water cells exibiting subsequent die-offs as conditions cooled. Tis was observed in 1998, wile at te same time, quantities of ealty sardine were observed offsore were water temperatures were warmer (McFarlane and MacDougall 2001). Consequently, tere is no apparent evidence of distinct sardine stocks in Canadian waters and available data suggest tat te annual nortward migration is constrained by te 12C isoterm (Ware 2001). In te past few decades, abundance of te California sardine population as increased, resulting in greater migration into Britis Columbia (BC) waters and a renewed interest in te fisery. Te annual sardine quota for fiseries in BC is tied to te estimate of sardine migration and uncertainties in tis estimate present a callenge for developing a arvest policy. Ware (1999) estimated te average migration rate of sardines into Canadian waters to be 10% based on te catces taken from in te United States (US) and Canadian fiseries (Figure 1) and proposed a arvest policy based on te US assessment model tat as been adopted since A trawl survey as been conducted off te west coast of Vancouver Island since te mid -1990s to monitor sardine abundance and distribution in Canadian waters wit an objective of providing updated estimates of migration. Tis report briefly describes te trawl survey results and proposes an updated estimate of te sardine migration rate into Canada. METHODS Surface Trawl Survey Surveys employing mid-water trawls towed near te surface ave been conducted on te west coast of Vancouver Island from 1997 to present to examine te distribution and relative abundance of sardines in Canada (McFarlane and MacDougall 2001). Abundance estimates were calculated using representative catces from te surface to 30 m dept, collected during cruises in late June, July and August. Te July cruises ave generally been most indicative of te relative sardine biomass in Canadian offsore waters. For estimating abundance, te west coast of Vancouver Island was partitioned into 6 regional areas or sampling strata (Figure 2), 5 of wic were sampled in most survey years. Sampling effort was considered to be complete wen sampling occurred in Areas 2-6, wereas wen regions were omitted due to time constraints (i.e. Areas 2 and 3), sampling was considered incomplete and not representative of distribution and abundance. Page 1 of 17 1

6 - 2 -Te total surface volume of eac region was estimated using te maximum dept fised (30m): Total surface volume (km 3 ) = Regional area (km 2 ) * km Eac region contained 3-5 transects wit 2-51 tows or sets per transect. Transects were run parallel or perpendicular to te sore, depending on weater, tides and currents, out to a bottom dept of 500 m. Tows of minutes duration were conducted sequentially along te lengt of eac transect (i.e., constant fising). Te swept volume of eac tow was determined by multiplying te area of te opening of te trawl net by te distance travelled: Swept Volume (km 3 ) = Net eigt (km) * Net widt (km) * Distance (km) From eac tow, total sardine catc was recorded by piece count or by weigt. If sardine catc was only recorded by weigt, te total number of fis caugt was estimated by dividing weigt (in kg) by te average individual sardine weigt for tat region. Using estimates of swept volumes for tows from te same region, estimates of average swept volumes and 95% confidence intervals were calculated for eac region. Day/ Nigt Calibration From 1997 to 2004 all sets were conducted during daytime ours. In July 2005, day/nigt catc comparisons were conducted off Nootka Sound and Barkley Sound to estimate day/nigt catc ratios. In tese areas, all sets were completed during 2 days and 2 nigts of fising. In 2006 and 2008, all tows were conducted at nigt and te calibration factor from te 2005 day/nigt catc ratios was applied to results from tese 2 years to represent daytime catces. Abundance Biomass estimates were calculated from data collected during cruises from 1997 to 2008 (Table 1). Biomass estimates were calculated according to te metod described in Beamis et al. (2000) assuming a stratified random sampling design. For eac regional stratum, total abundance was estimated as te number of sardines per swept volume times te total swept volume: were C V = v c = regional stratum (Areas 2 to 6) C = estimated number of sardines in stratum c = average number of sardines caugt in stratum V = estimated surface volume of stratum v = average swept volume of all sets in stratum N = V / v, or te total number of possible samples of size v in stratum Te corresponding variance estimator for abundance in te t stratum is: 2

7 2 Sc var( C ) = N ( N n ) n were catc sample variance by stratum is represented by: S 2 c = n i ( c ( n i c 1) ) 2 c i = number of sardines caugt in sample i in stratum c = average number of sardines caugt in stratum n = number of samples taken in te t stratum Abundance in number of sardines was converted to weigt (kg) by multiplying abundance in numbers by average weigt (kg) of an individual sardine by stratum: were B V = v c w w = average sardine weigt (kg) in stratum For 1997, 1999, and 2001, te average sardine weigt in all strata was estimated as kg because fis sizes were similar. Te corresponding variance estimator for abundance (weigt) in te te stratum is: 2 Sb var( B ) = N ( N n ) n were catc sample (weigt) variance by stratum is represented by: S 2 b = n i ( w c w ( n 1) c ) 2 Minimum and maximum biomass estimates were determined using an approximate 95% confidence interval determined as te average biomass plus or minus twice te standard error (square root of te estimated sample weigt variance). Migration Rates Estimates of te annual migration rate for eac survey year were developed by calculating te ratio of estimated biomass off te west coast of Vancouver Island and te total biomass estimate for te coastwide population, as presented in te annual United States sardine assessment (Hill et al., 2008). 3

8 RESULTS Abundance Sardine biomass estimates for te west coast of Vancouver Island from complete surveys (Areas 2-6) were calculated for years:1997, 1999, 2000, 2001, 2004, 2006 and 2008; wereas biomass estimates from incomplete surveys were calculated for 2002 and 2005, and no surveys occurred in 1998, 2003 and 2007 (Tables 1-4, Figure 3). A summary of te number of sets conducted in eac region eac survey year is presented in Table 1. In 2000 and 2004, sardine trawl catc distributions were especially patcy, wic was tougt to be partly attributed to gear avoidance and ig variability in daytime scool densities and depts. Consequently, sampling data for tese two years are not considered representative of distribution and abundance and are treated as anomalous (Tables 3 and 4). Te results of te 2005 day/nigt calibration trials sowed average day time catc rates to be iger tan nigt time rates by approximately 21%. Terefore, tis calibration factor tat was applied to te 2006 and 2008 catces to calculate an adjusted biomass estimate. Te adjusted estimates are presented in Table 3. For te entire time period, average annual estimates of biomass range from 14,793 t (2002) to 258,702 t (2006) wit considerably ig peak years in 2006 and 2008 (Figure 3). Sardine biomass estimates for 1997 and 1999 were 88,626 and 79,398 tonnes respectively, and similar to te 2000 and 2001 surveys, te majority of sardines were found in te soutern 3 strata (Areas 4-6). Tere were anecdotal reports of large quantities of sardines in insore waters in 2000 and 2001, particularly te inlets along te west coast of Vancouver Island and tese fis would not ave been detected by te trawl survey Migration Rates Migration rates are calculated as te ratio of biomass estimated off te west coast of Vancouver Island and te total coastwide biomass of Pacific sardine as presented in te annual United States stock assessment document (Hill et al., 2008, Table 4). Based on all annual estimates of average biomass from te trawl survey time series, migration rates range from 1.9% to 34.7%, or 12.9% over all years (Table 4a). Wen calculation of migration rate is limited to survey data for years wit representative survey coverage (omitting years wit incomplete effort and anomalous catc distributions), estimated migration ranges from 5.0% to 34.7%, corresponding to an overall average rate of 18.3% (Table 4b). As wit te abundance estimates, te 2006 (27.2%) and 2008 (34.7%) migration rate estimates are te igest on record. DISCUSSION During te early 20 t century, te Canadian fisery took on average about 10% of te combined US and Canadian sardine catc in te Pacific Nortwest (Figure 1). Assuming te Canadian and US fiseries arvested te available supply of sardines at about te same rate, ten on average about 10% of te sardine population migrated to BC in te summer. Tis was te basis for te procedure proposed by Ware (1999) for determining te probable biomass of Pacific sardine in Canada and for proposing a arvestable surplus, wic is also based on annual US stock assessment results (Hill et al., 2008, Appendix A). Te procedure proposed by Ware as been used to make arvest recommendations to fiseries management since it was adopted by PSARC for Compared to istorical estimates, recent scientific catc data from te trawl survey suggest increased levels of migration into Canadian waters; consequently, tere as 4

9 been increasing interest in te fisery for arvesting opportunities. Based on our analysis of trawl survey data from te west coast of Vancouver Island and on oter recent observations of sardines in Canadian wasters, we suggest tat te currently assumed average migration rate of 10 % from Ware (1999) is conservative and sould be updated to take into consideration te more recent information. From 1992 to 1996, small numbers of sardines were captured in bot commercial and researc sets targeting Pacific ake off te soutwest coast of Vancouver Island. Since 1997, large numbers of sardines ave been captured in surface waters off te west and norteast coasts of Vancouver Island, Queen Carlotte Sound, and in inlets surrounding Vancouver Island in bot researc surveys and commercial fiseries. From 1997 to 1999, sardines were found in te Strait of Juan de Fuca, in te Strait of Georgia, along te west coast of Vancouver Island, Hecate Strait, and off souteast Alaska. Sardine distribution in 2000 was concentrated on te west coast of Vancouver Island and ranged as far sout as Barkley Sound and as far nort as te mainland of Britis Columbia, nort of Vancouver Island. From 2001 to 2003, sardine distribution became progressively concentrated near sore along te soutwest coast of Vancouver Island and progressively less prevalent in researc cruises. By 2004, sardines were rarely captured offsore or along te researc grid; owever, large commercial catces of sardines were made in inlets and te sallows along te west coast of Vancouver Island. In 2004, sardines were also commercially caugt in inlets of Queen Carlotte Sound. In 2005, part of te survey was directed at developing a relationsip between day and nigt sampling. Te calibration trials were done to explore catc efficiency and sampling representivity since daytime beaviour of fis scools was suspected to ave iger gear avoidance and patcier vertical and orizontal distributions. Sampling by nigt was subsequently determined to be more conducive to estimating sardine biomass by surface trawl gear. For similar reasons, nigt trawl sampling for sardines is applied in Oregon (Emmett et al., 2005). Wile nigt trawl sampling was conducted in 2006 and 2008, te distribution of sardine catces extended along te entire west coast of Vancouver Island and relatively ig catces of sardine occurred. Future work sould explore an optimal sampling design for te trawl survey, and review te calibration of day and nigt catces. Te trawl surveys conducted off te west coast of Vancouver Island sampled sardines in offsore waters, wic did not include inlets, oter insore areas, nor areas nort of Vancouver Island, all known to ave contained significant quantities of sardine in recent years. Consequently, te average biomass estimate from te trawl surveys can be assumed to provide a minimal approximation of te total biomass of sardines in Canadian waters. Te average migration estimate from all of te available west coast of Vancouver Island survey years, including tose wit incomplete coverage is 12.9 % wile for te five years for wic survey coverage was considered to be representive, te average migration rate estimate is 18.3 %. Given tat tese surveys do not cover te entire known distribution of sardines in Canadian waters, we feel tat a migration rate estimate based on te average of te trawl survey estimates for te complete surveys of 18.3 % is conservative and precautionary and recommend tat tis approac be used for determining arvest levels in te sort term. Future analysis sould be undertaken to investigate te application of a running average migration rate or oter decision rules for providing precautionary arvest guideline for sardines in Canadian waters. 5

10 AKNOWLEDGMENTS We appreciate te ongoing support of te captains and crew of te W.E. Ricker and te numerous students and casual staff wo participated in te surveys over te years for teir successful completion. Bill Andrews for is role in co-ordinating and conducting muc of te biological sampling. Reviewer comments by Jaclyn Cleary greatly improved te report and Linnea Flostrand provided elpful editorial assistance. REFERENCES Beamis, R. J., D. McCaugran, J. R. King, R. Sweeting and G.A. McFarlane Estimating te abundance of juvenile coo salmon in te Strait of Georgia by means of surface trawls. N. Am. J. Fis. Manage. 20: Emmett, R. L., R. D. Brodeur, T. W. Miller, S. S. Pool, P. J. Bentley, G. K. Krutzikowsky, and J. McCrae Pacific sardine (Sardinops sagax) abundance, distribution and ecological relationsips in te Pacific Nortwest. CalCOFI Report. 46: Hargreaves, N.B., D.M. Ware and G.A. McFarlane Return of te Pacific sardine (Sardinops sagax) to te Britis Columbia coast in Can. J. Fis. Aquat. Sci. 51: Hart, J.L A brief account of te life-istory of te pilcard. B.C. Fiseries Department Report. pp Hart, J. L Pacific fises of Canada. Bulletin of te Fiseries Researc Board of Canada 180: Hill, K.T., E. Dorval, N.C.H. Lo, B. J. Macewicz, C. Sow and R. Felix-Uraga Supplemental Attacment 1 to te Pacific Sardine Stock Assessment and Management Measures Agenda Item G.2.b. Assessment of te Pacific sardine resource in 2008 for United States management in Pacific Fisery Management Council, Portland, OR, USA (2008) (147p). McFarlane, G.A., and R.J. Beamis Te re-occurrence of sardines off Britis Columbia caracterises te dynamic nature of regimes. Prog. in Oceanog. 49: McFarlane, G.A., and L.A. MacDougall Biological information for Pacific sardine (Sardinops sagax) captured during researc cruises, Can. Tec. Rep. Fis. Aquat. Sci. 2372: 149p. McFarlane, G.A., L.A. MacDougall, J. Scweigert, C. Hrabok Distribution and biology of Pacific sardine (Sardinops sagax) off Britis Columbia, Canada. CalCOFI Report. 46: Ware, D.M Life istory of Pacific sardine and a suggested framework for determining a B.C. catc quota. DFO Can. Sci. Advis. Sec. Res. Doc. 1999/204. Ware, D.M Forecasting te time of arrival and availability of Pacific sardine in Britis Columbia. Unpublised manuscript prepared for DFO and BC Sardine Association. 22p. 6

11 Table 1. Summary of te number of sets and survey areas sampled from 1997 to Number of sets wit sardine catces are also sown. Year Survey Area Number of sets Sets wit sardines

12 Year Area Volume of area Swept Volume (km3) Swept volume 95% Average kg Average number of fis Minimum (ave - 95%CI) Biomass (Mt) Average Maximum (ave + 95% CI) ,509 7,499 9,172 11, ,673 4,069 8, ,154 12,696 39,454 54,853 89, ,222 4,234 5,176 6, ,521 12,902 15,355 18, Biomass Totals: 66,762 88, , ,186 6,146 6,744 7, ,127 4,345 4, ,774 4,159 4, ,307 6,487 8,690 13, ,262 44,122 55,459 71, Biomass Totals: 64,656 79, , ,819 4,296 4, ,369 38,961 43,452 49, Biomass totals: 42,964 47,947 54, ,616 33,804 43,824 62, Biomass Totals: 33,839 43,865 62, no fising ,087 7,688 8,720 10, ,973 4,403 4, Biomass totals: 11,696 13,161 15, ,995 8,917 10, ,692 12,050 12,867 13, Biomass totals: 27,591 30,504 34, no fising ,008 15,498 16,097 16, ,885 22,547 23,710 25, ,275 69,710 71,949 74, Biomass totals: 107, , , ,577 7,865 8,216 8, ,422 10,595 11,741 13, ,510 11,035 69,730 85, , ,154 9,193 58,381 66,905 78, ,328 36,512 41,464 47, Biomass Totals: 183, , , ,476 7,254 8,029 8, ,398 9, , , , ,005 34,003 39,412 46, ,329 13,390 14,641 16,151 Table 2. Estimated sardine biomass for te west coast of Vancouver Island for all survey years Biomass Totals: 163, , ,253 8

13 Table 3. Pacific sardine biomass estimates for all years including tose adjusted using te nigt/day conversion factor (2006 and 2008). Note te partial surveys in two years (2002 and 2005). Survey Average Maximum Year area description biomass (mt) biomass (mt) ,172 11, ,069 8,522 Complete 4 Survey 54,853 89, ,176 6, ,355 18,961 Total: 88, , ,744 7, ,345 4,588 Complete 4 Survey 4,159 4, ,690 13, ,459 71,123 Total: 79, , ,296 4,910 Anomalous distribution 5 43,452 49, Total: 47,947 54, Complete 4 Survey ,824 62,285 Total: 43,865 62,336 Year area Survey description Average biomass (mt) Maximum biomass (mt) Incomplete Survey 8,720 10, ,403 4, Total: 13,161 15, Anomalous 4 distribution 8,917 10, ,867 13, Total: 30,504 34, Incomplete Survey 16,097 16, ,710 25, ,949 74,336 Total: 111, , ,941 10, ,207 15,930 Nigt survey 4 103, ,596 adjusted to day 5 80,955 94, ,172 58,045 Total: 258, , ,715 10, , ,541 Nigt survey 4 adjusted to day 47,689 56, ,716 19,543 Total: 229, ,977 9

14 Table 4. Percentage of te coastwide Pacific sardine biomass estimated to be in te Canadian zone. Estimates representing total biomass in US and Canadian waters are from Hill et al., Biomass for 2006 and 2008 adjusted to daytime catc rates. a) All survey years. year Average biomass (mt) Maximum biomass (mt) Total biomass (mt) (US and Canada) Proportion in Canadian waters Average Abundance Proportion in Canadian waters Maximum Abundance , , , , , , ,947 54,239 1,002, ,865 62, , ,161 15, , ,504 34, , , , , , , , , , , Overall: b) Survey years 1997, 1999, 2001, 2006 and 2008 (excludes years wit incomplete survey coverage or believed to ave anomalous sardine distribution). year Average biomass (mt) Maximum biomass (mt) Total biomass (mt) (US and Canada) Proportion in Canadian waters Average Abundance Proportion in Canadian waters Maximum Abundance , , , , , , ,865 62, , , , , , , , Overall:

15 Figure 1. Percentage of te combined United States and Canadian sardine catc landed in Britis Columbia. Te average is 10%. However, tere were extended periods were te fraction was appreciably iger (e.g to 1932), and lower (e.g to 1941), taken from Ware (1999). 11

16 Figure 2. Pacific sardine survey areas for te west coast of Vancouver Island delineating te sampling regions. 12

17 Pacific Sardine estimated biomass: WCVI 300, , ,000 mt 150, ,000 50, Year Nigt Time Day Time Figure 3. Estimated Pacific sardine biomass estimates in te Canadian zone from WE Ricker sardine trawl surveys on te west coast of Vancouver Island conducted from 1997 to Surveys in 2002 and 2005 were incomplete. Results for nigt time surveys in 2006 and 2008 adjusted to day time. Catc distributions in 2000 and 2004 are considered anomalous. 13

18 Appendix A: Procedures For Recommending Pacific Sardine Harvests Te US formula (Hill et al., 2008): were H = (Total Biomass Cutoff) x Fraction x Distribution H = total US arvest (California, Oregon, Wasington); Biomass = total biomass of age 1 and older fis at te beginning of season; Cutoff = lowest biomass were arvest is allowed (currently 150,000 tonnes); Fraction = MSY control rule for proportion of stock to be arvested; Distribution = fraction of stock biomass in US Waters (87% in 2008). Fraction is a proxy for F msy, wic is te fising mortality rate to acieve MSY and is te environmental-based percentage of te biomass above te Cutoff tat can be arvested by te fisery. Fraction depends on ocean temperatures because F msy and sardine productivity are bot iger at warmer water temperatures: Fraction or F msy = T T , were T is te average sea surface temperature at Scripps Pier, California during te preceding tree seasons but F msy is constrained to range between 5 and 15%. Based on te current ocean conditions te exploitation fraction for 2009 will remain at 15%. On tis basis, te United States assessment assumes a very small migration rate of only 13% tat is actually targeted by te Mexican fisery and makes no consideration for te fis in Canada. Te BC Formula (Ware, 1999): Te following relationsip represents te estimate of sardine biomass tat will potentially migrate to BC te following season: BC Biomass (tonnes) = Total Coastwide Biomass (tonnes) x BC Migration rate 14