COSEWIC Assessment and Status Report on the Yellowmouth Rockfish in Canada – 2010: Population Sizes and Trends

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Yellowmouth Rockfish catch records only extend back to 1971. To reconstruct historical removals of the species prior to 1971,1996–2006 trawl fishery data on the proportion of Yellowmouth Rockfish caught to other rockfish (YMR/ORF) and the proportion of Yellowmouth Rockfish discarded to retained (YMRd/YMR) were applied to historical catch records (Haigh and Starr 2008). While these ratios have remained relatively constant over the ten–year period it is probably unrealistic to assume that modern ratios, taken from a fishery using an Individual Vessel Quota (IVQ) system, resemble past fishery patterns. Historical abundance estimates were made for both US vessels fishing in BC waters from 1930 to 1975 and Canadian vessels from 1945 to 1982. Catch estimates are more difficult to calculate for the large Soviet and Japanese trawling fleets, which operated along the BC coast from 1965 to 1976, because information on species composition and locality of catches are unavailable (Haigh and Starr 2008). However, employing the above YMR/ORF ratio used for domestic fisheries to the largest year of the Soviet fishery (1966) provides a rough estimate of this fishery’s impact on the Yellowmouth population.

Contemporary abundance estimates for Yellowmouth Rockfish are obtained from a variety of research surveys (e.g., bottom trawl, mid–water shrimp tows) and commercial catch–per–unit–effort (CPUE) from the trawl fishery.

Synoptic bottom trawl surveys operate biennially within Queen Charlotte Sound (QCS synoptic bottom trawl survey; north Vancouver Island to southern Hecate Strait), along the west coast of Vancouver Island (WCVI synoptic bottom trawl survey), and west of the Queen Charlotte Islands (WQCI synoptic bottom trawl survey). These surveys target all groundfish species using random tow allocations per stratum and cover depths of 50 to 1300 m. The surveys were only initiated within the last five years and thus do not yet provide sufficient data to detect trends. Based on bootstrapped biomass indices from these surveys, precision of the biomass estimates is considered to be adequate to poor (Haigh and Starr 2008). The biomass indices assume a catchability quotient of q = 1 which is probably too high for Yellowmouth Rockfish, although catchability is unknown for the species. Over time these time series may provide more useful data on abundance trends.

Tow–by–tow data are available from the G.B. Reed historical Queen Charlotte Sound surveys for nine years between 1965 and 1984. Although these surveys cover various geographic areas both within and outside British Columbia, to ensure consistency between surveys, only tows from Goose Island Gully (i.e., tows between 50.90° N and 51.6° N; Fig. 8) were used for abundance estimates. Estimates are based on tows conducted between 147–428 m. These data are available for seven years between 1967 and 1984, for a total of 254 tows. The precision for these indices is considered low (Haigh and Starr 2008).

Figure 8. Locations of all trawls from the G.B. Reed trawl survey (1967–1984) which caught Yellowmouth Rockfish. Only tows in Goose Island Gully which were used in the biomass index calculation are shown. Circles are proportional to catch density (largest circle = 8.11 kg/km²). Also shown are the 100, 200 and 300 m isobaths (from Haigh and Starr 2008).

Map of the locations of all trawls from the GB Reed trawl survey from 1967 to 1984 that caught Yellowmouth Rockfish. For Goose Island Gully, only tows used in calculating the biomass index are shown.

Two shrimp trawl surveys provide additional incidental abundance trend information for slope rockfish in British Columbia. The WCVI shrimp trawl survey covers the west coast of Vancouver Island, and, while it has generated useful indices for other rockfish species (e.g., Bocaccio S. paucispinus and Canary Rockfish S. pinniger), only two observations of Yellowmouth Rockfish were made in the survey over a 33–year period from 1972 to 2007. In contrast, the QCS shrimp trawl survey, covering southern Queen Charlotte Sound, has had a more reliable catch of Yellowmouth Rockfish. This survey has operated since 1999, consistently sampling depths up to 220 m. The survey is divided into three aerial strata: stratum 109 (west of the outside islands and extending into Goose Island Gully), stratum 110 (south of Calvert Island and the mainland) and stratum 111 (between Calvert Island and the mainland). Stratum 111 was omitted from the abundance analysis because no Yellowmouth Rockfish have been caught in this inshore area (Fig. 9) (Haigh and Starr 2008). The majority of remaining tows have occurred in stratum 109 and over 600 usable tows are available during the nine survey years.

Figure 9. Locations of tows conducted by the Queen Charlotte Sound shrimp survey from 1999 to 2007. The tows to the east of Calvert Island represent Stratum 111 which was not used in the analysis (from Haigh and Starr 2008). Tows to the south of Calvert Island are in stratum 110, and the remaining tows west of the coastal islands are in stratum 109.

Map of the locations of tows conducted by the Queen Charlotte Sound shrimp survey from 1999 to 2007.

NMFS triennial bottom trawl surveys along the US west coast extended into Canadian waters in seven years between 1980–2001. The surveys cover the Vancouver International North Pacific Fisheries Commission (INPFC) region (Fig. 10), which is divided by NMFS into strata. The size and definition of these strata has varied over time. To standardize survey data, strata not surveyed consistently from year to year were subsequently omitted, and indices from two years (1980 and 1983) were scaled up so that their area coverage was comparable to later years (Haigh and Starr 2008). All abundance indices for Yellowmouth Rockfish derived from this dataset were highly variable. Furthermore, the bootstrapped coefficient of variation (CV) estimates do not account for the expanded ratios applied to 1980 and 1983 surveys and the uncertainty in these estimates is likely greater than what is indicated.

A general linear model (GLM) analysis of commercial trawl CPUE was conducted for April 1996 through March 2007, using only bottom trawl data. The start date of the analysis coincides with the initiation of the At–Sea Observer Program, which means that identification to species was accurate. Much of the previous catch rate data is considered unreliable due to mis–reporting and variation in trip limits over time.

Because commercial fisheries aim to maximize harvesting rates of target species, and are governed by existing fishery regulations, their CPUE indices may not necessarily accurately reflect fish abundance. A number of factors may account for the observed variability in CPUE values, including date of capture, capturing vessel, depth and location of capture and fishing behaviour (e.g., avoidance fishing) (Schnute et al. 1999). However, large–scale changes in Yellowmouth abundance should be reflected in the CPUE signal, especially if the stock is declining, because vessels will no longer be able to achieve their target catches (Haigh and Starr 2008).

Only bottom tows were used in the CPUE analysis because mid–water trawls were unreliable at catching Yellowmouth Rockfish. All observations in which Yellowmouth Rockfish were absent were removed. While these zero–tows may provide important information, the lognormal model used for the analysis required positive values for the dependent observations (Haigh and Starr 2008).

Figure 10. Tow locations in the Vancouver INPFC region for each of the seven triennial surveys that included Canadian waters. The approximate position of the US/Canada marine boundary is shown (dashed line). The horizontal lines are the stratum boundaries: 47°30’, 47°50’, 48°20’, and 49°50’. Tows south of the 47°30’ line were excluded from the analysis. Isobaths are the stratum depth boundaries at 55, 183, 220, 366, and 500 m (from Haigh and Starr 2008).

Map of tow locations in the International North Pacific Fisheries Commission Vancouver region for each of the seven triennial surveys that included Canadian waters.

The estimated total coastwide catch of Yellowmouth Rockfish since the 1930s in Canada (including all Canadian and US fisheries) is at least 60 000 t (Appendix 2) or 41 million fish (using the mean weight ŵ =1.47 kg, s = 0.33, n = 1678; Haigh and Starr 2008).

Yellowmouth Rockfish are caught in much lower numbers along the US west coast and in Alaska, and British Columbia appears to be the population centre for this species.

Yellowmouth Rockfish is an important component of the BC groundfish fishery. The mean annual catch by decade remained fairly constant until the mid–1970s but increased sharply once a Yellowmouth quota was introduced in 1979 (Fig. 11). Catch by Canadian vessels peaked in 1986 (2491 t or 1.6 million fish) and has averaged 1842 t (or 1.2 million fish) annually between 1997–2007. In comparison, the Soviet 1966 trawl fishery caught between 29 000–63 000 tonnes of groundfish in BC. Assuming the Yellowmouth to other rockfish ratio calculated for contemporary domestic trawls, this translates to approximately 1300–3000 tonnes of Yellowmouth caught in the 1966 fishery, an amount comparable to levels harvested annually by Canadian vessels since 1979 (Haigh and Starr 2008).

Figure 11. Catch history of Yellowmouth Rockfish by US and Canadian fleets along the BC coast. Mean annual catches by decade are displayed in horizontal boxes.

Chart showing catch history for Yellowmouth Rockfish caught by United States and Canadian fleets along the British Columbia coast.

Based on the most recent stock assessment in 1999, recruitment has been low in BC Yellowmouth Rockfish since the early 1980s (DFO 1999a, Haigh and Starr 2008 Figure 9). As a result, abundance levels are expected to decline steadily until the next major recruitment episode. Successful recruitment likely will not be evident in the age structure data until cohorts reach seven years of age (DFO 1999a).

Two experimental programs were conducted in the 1980s to assess adaptive management strategies for Pacific ocean perch stocks; these are not directly relevant to Yellowmouth Rockfish assessment although the first showed that this species can be depleted by intensive fishing. The first experiment focused on PMFC Area 3C (southwest Vancouver Island) and consisted of overharvesting the area (by ~160 t of the estimated sustainable yield, or 500 t/yr) for five years (1980–1984), followed by a return to sustainable harvests (300 t/yr) in 1985. Surveys carried out before (1979) and after (1985) the experimental period indicate that the relative abundance of Yellowmouth Rockfish declined by 17.1% (compared with a decline of 55.8% for Pacific Ocean Perch). The total annual catch of Yellowmouth Rockfish decreased from 2077 to 668 kg, and the CPUE declined from 22.1 kg/h to 6.68 kg/h (Leaman and Stanley 1993). The second experiment was originally intended to allow unlimited harvesting for three to five years within PMFC Area 5E (Langara Spit, northwest of Queen Charlotte Islands), followed by no harvesting for an equivalent period. However, the harvesting period was extended to nine years (1984–1992), followed by area closure in 1993. Surveys in 1979 and 1983 in the area reported unreliable biomass indices for Yellowmouth Rockfish (Leaman and Stanley 1993). The area was re–opened to fishing in 1997.

The three synoptic bottom trawl surveys have generated only a few years of data to date and thus are not yet useful for detecting abundance trends (Figs. 12 and 13, Table 3). Nevertheless, over time these surveys may provide valuable information on Yellowmouth population parameters. In particular, the QCS and WCVI surveys generated coefficient of variation values (CVs) under 0.50, suggesting that their precision may be fairly reliable in future (Appendices 3 and 4).

Biomass estimates from the G.B. Reed seven year surveys in Goose Island Gully were relatively uniform for the first five years, but dropped markedly in the last two surveys. Most surveys (except for 1977) had wide error bars and all had high CVs, ranging from 49–84% (Fig. 14, Table 3, Appendix 5). The proportion of tows containing Yellowmouth Rockfish varied from less than 20% to over 50%. The species was mainly captured along the 200 m depth contour around the entrance to Goose Island Gully (Fig. 8). A log–linear regression of the time series provided a non–significant slope estimate of −0.12 yr−1 (p=0.15, Table 3).

Biomass estimates from the QCS shrimp trawl survey have been relatively low and highly variable, with no obvious trend emerging in the time series (Fig. 15, Table 3, Appendix 6). Most catches of Yellowmouth Rockfish were made in the 170–210 m depth range along the upper section of Goose Island Gully. No Yellowmouth were captured at any depth in stratum 110. The proportion of tows capturing Yellowmouth in stratum 109 varied from less than 5% to more than 20% (Fig. 16). A log–linear regression of the time series provided a non–significant slope estimate of 0.059 yr−1 (p=0.52, Table 3).

Figure 12. Relative index for Yellowmouth Rockfish in Queen Charlotte Sound from the QCS synoptic bottom trawl survey. Vertical bars indicate 90% confidence intervals from 1000 bootstrapped biomass index estimates (from Haigh and Starr 2008).

Chart showing the relative biomass index for Yellowmouth Rockfish caught by the Queen Charlotte Sound synoptic bottom trawl survey from 2003 to 2007.

Figure 13. Relative index for Yellowmouth Rockfish on the west coast of Vancouver Island from the WCVI synoptic bottom trawl survey. Vertical bars indicate 90% confidence intervals from 1000 bootstrapped index estimates (from Haigh and Starr 2008).

Chart showing the relative biomass index for Yellowmouth Rockfish caught by the west coast Vancouver Island synoptic bottom trawl survey from 2004 to 2006.
Table 3. Summary of existing biomass indices for Yellowmouth Rockfish in British Columbia. The rate of change was estimated with a log–linear regression, and the probability level of the slope estimate is shown (p–value) along with the number of survey estimates used (n points). The final column provides comments on the reliability of the different indices and analyses.
Index name Years Rate of change yr−1 p–value n points Reliability
QCS synoptic bottom trawl survey 2003–2007 −0.097 0.62 4 Low due to short time series but may be useful in the future
WCVI synoptic bottom trawl survey 2004–2006 2 Low due to short time series, but may be useful in the future
G.B. Reed historical QCS survey 1967–1984 −0.12 0.15 7 Highly variable index, proportion of tows with Yellowmouth ranged from <20%–>50%
WCVI shrimp trawl survey 1975–2007 Insufficient data (only two observations of Yellowmouth)
QCS shrimp trawl survey 1999–2007 0.059 0.52 9 Low reliability due to highly variable proportion of tows with Yellowmouth (0–>20%)
NMFS triennial bottom trawl survey 1980–2001 −0.21 0.058 6 Low reliability, relatively few tows (3%) captured Yellowmouth
Combined regression: G.B. Reed, NMFS triennial, QCS groundfish, WCVI groundfish, QCS shrimp 1967–2007 −0.14 0.0001 28 Questionable due to low temporal and spatial overlap
Combined regression: G.B. Reed, NMFS triennial 1967–1998 −0.17 0.009 13 As above
Commercial trawl CPUE 1996–2007 −0.025 11 Catch and effort rates may be influenced by changes in fishing practices over survey period

Figure 14. Relative biomass estimates for Yellowmouth Rockfish from the Goose Island Gully G.B. Reed trawl surveys from 1967–1984, with bias corrected 95% confidence intervals from 1000 replicates (from Haigh and Starr 2008).

Chart showing relative biomass estimates for Yellowmouth Rockfish from the Goose Island Gully G.B. Reed trawl surveys from 1967 to 1984.

Figure 15. Relative biomass estimates for Yellowmouth Rockfish from the QC Sound shrimp trawl survey for 1999–2007, with bias corrected 95% confidence intervals from 1000 bootstrap replicates (from Haigh and Starr 2008).

Chart showing relative biomass estimates for Yellowmouth Rockfish from the Queen Charlotte Sound shrimp trawl survey from 1999 to 2007.

Figure 16. Locations of all trawls from the Queen Charlotte Sound shrimp trawl survey (1999–2007) which caught Yellowmouth Rockfish. Circles are proportional to catch density (largest circle = 2.47 kg/km²). The 100, 200 and 300 m isobaths and the area stratum boundaries for the QCS synoptic bottom trawl survey are also displayed (from Haigh and Starr 2008).

Map showing locations of all trawls by the Queen Charlotte Sound shrimp trawl survey from 1999 to 2007 that caught Yellowmouth Rockfish.

The NMFS triennial bottom trawl survey generated highly variable biomass estimates. Estimates were generally higher in the early years of the survey but error bars and CVs were large for most estimates, making it difficult to detect an overall trend (Fig. 17, Table 3, Appendix 7). The largest Yellowmouth Rockfish catch occurred in 1983 in both Canadian and US waters. Overall, Yellowmouth seems more abundant in the Canadian portion of the survey (Fig. 17). Approximately 3% of all tows (23 of 697) caught Yellowmouth Rockfish over the seven–year survey. No Yellowmouth were caught in the Canadian portion of the survey in 2001, and Yellowmouth were absent from the US portion of the survey in 1980 (Appendix 7). The highest proportion of tows with Yellowmouth in Canada occurred in 1989 (0.092) and in 1983 (0.06) in the US. Yellowmouth was caught in highest frequency between 100–300 m (Haigh and Starr 2008). A log–linear regression of the Canada Vancouver time series provided a non–significant slope estimate of −0.21 yr−1 (p=0.058). It should be noted that the 2001 observation of “0” catch was not included in this analysis.

Figure 17. Relative biomass estimates for Yellowmouth Rockfish from NMFS triennial surveys in the INPFC Vancouver region (total region, Canadian portion, and US portion) with 95% bias corrected error bars estimated from 5000 bootstrap replicates (from Haigh and Starr 2008).

Three charts showing relative biomass estimates for Yellowmouth Rockfish from U.S. National Marine Fisheries Service triennial surveys in the International North Pacific Fisheries Commission Vancouver region. The charts present data for the total region and for the Canadian and U.S. portions of the region.

A combined log–linear regression of the different survey time series was conducted using the G.B Reed, NMFS triennial survey, Queen Charlotte Sound and West Coast Vancouver Island groundfish surveys, and the Queen Charlotte Sound shrimp survey. An analysis of covariance was used with separate intercepts for the survey series and a common slope. The slope estimate was statistically significant (−0.13 ± 0.089, p<0.001, Table 3, Fig. 18). Over the 40–year time period covered by the surveys, this would indicate a decline of 99.6%.

A second combined analysis including only the G.B. Reed and NMFS triennial surveys (which have relatively long time series and overlap temporally) shows a significant declining trend between 1967 and 1998, giving an overall decline in the indices to 2% of the original (Table 3).

The results from both of these combined analyses should be treated with caution. A key assumption of the analysis is that the individual surveys are measuring a common process that is the temporal trend in abundance of the Yellowmouth Rockfish DU. It should be noted that there is little spatial and temporal overlap among these surveys and it is virtually impossible to verify this assumption. Furthermore, Yellowmouth Rockfish catches have been relatively stable over the past 20 years (Fig. 11) and it is difficult to reconcile this with such a large estimated decline in abundance.

Figure 18. Time series on research survey indices (ln scale) of Yellowmouth Rockfish adjusted for their respective intercepts in a combined analysis of covariance. The letters indicate a) G.B. Reed, b) NMFS triennial, c) Queen Charlotte Sound shrimp survey, d) Queen Charlotte Sound synoptic groundfish survey, and e) west coast Vancouver Island synoptic groundfish survey. The fitted line shows the annual rate of change estimated in the combined GLM analysis (slope = −0.14 yr−1).

Chart providing time series on research survey indices (ln scale) for Yellowmouth Rockfish adjusted for their respective intercepts in a combined analysis of covariance.

CPUE indices are relatively high for Yellowmouth Rockfish, averaging over 500 kg/h coastwide. The highest CPUE values were found along the west coast of Moresby Island, an area of relatively low total rockfish catch (Haigh and Starr 2008). An annual decline of 2.5% in Yellowmouth Rockfish CPUE has occurred between 1996–2006, although the trend has levelled out somewhat since 2001 (Fig. 19). As mentioned before, caution should be exercised when interpreting CPUE indices, because they may be affected by a variety of factors unrelated to actual abundance. For example, under the IVQ system, fishers may alternate between targeting and avoiding Yellowmouth Rockfish depending on such conditions as local abundance, market requirements, and quota availability (Haigh and Starr 2008). Additional factors affecting the CPUE indices include time of year (Yellowmouth CPUE peaks in August and dips in December; Fig. 20b), depth (CPUE is highest between 150–300 m; Fig. 20c), and latitude (CPUE is highest between 50.2° N–51° N and lowest between 51° N and 51.6° N ; Fig. 20d). Furthermore, the choice of which vessels to include in the analysis can have a dramatic effect on CPUE trends. For example, the annual rate of decline mentioned above was calculated using all vessels contributing 3% or more of the Yellowmouth catch over the period of the analysis. However, if this threshold is increased to 3.5% the index changes from a declining to an increasing trend (Haigh and Starr 2008).

Figure 19. Annual index trend in Yellowmouth Rockfish commercial trawl CPUE data (1996–2006) based on a general linear model (GLM) analysis with five factors: year, month, depth, latitude, and vessel. The error bars show 95% confidence intervals. The vertical dashed line indicates an adjustment phase during which vessels chose two out of three trimesters to maximize catch within the bounds of quotas and catch limits. Following this period, an individual vessel quota (IVQ) program was introduced, with transferable IVQs managed under a market–based trading system (from Haigh and Starr 2008).

Chart showing the annual index trend in Yellowmouth Rockfish commercial trawl catch-per-unit effort data from 1996 to 2006, based on a general linear model analysis with five factors: year, month, depth, latitude and vessel.

Information on trends in Yellowmouth Rockfish length over time is available from research, charter and commercial trawl surveys since 1967 (Figs. 2123). In general, most individuals captured are between 40–50 cm in all years, although the 2004–2007 charter data indicate an increase in juveniles (~10 cm) caught during this period.

Figure 20. Annual index trend and factor coefficients for the GLM analysis of Yellowmouth Rockfish commercial trawl CPUE data (April 1996 to March 2007). (A) annual CPUE indices (by fishing year) with fitted curve indicating instantaneous decline; (B) month effect on CPUE; (C) depth effect on CPUE where depth is partitioned into 50–m depth zones between 50–500 m; (D) latitude effect on CPUE where WCVI = 48° N to 50.2° N , Scott = 50.2° N to 51° N , QCS = 51° N to 51.6° N , MG–HS = 51.6° N to 52.8° N , and Dixon = 52.8° N to 54.8° N ; (E) vessel effect on CPUE where vessels accounted for > 3% of the Yellowmouth catch over the period of the analysis. Error bars show 95% confidence intervals (from Haigh and Starr 2008).

Five-panel chart presenting annual index trend and factor coefficients for the general linear model analysis of Yellowmouth Rockfish commercial trawl catch-per-unit-effort data from April 1996 to March 2007.

Figure 21. Relative frequency of Yellowmouth Rockfish lengths by calendar year (1966–1982) and trip type. Lengths are binned using 2–cm intervals; n = number of fish, L = mean length (cm) (from Haigh and Starr 2008).

Multi-panel chart showing relative frequency of Yellowmouth Rockfish lengths by calendar year (1966 to 1982) and trip type.

Figure 22. Relative frequency of Yellowmouth Rockfish lengths by calendar year (1983–1995) and trip type. Lengths are binned using 2–cm intervals; n = number of fish, L = mean length (cm) (from Haigh and Starr 2008).

Multi-panel chart showing relative frequency of Yellowmouth Rockfish lengths by calendar year (1983 to 1995) and trip type.

Figure 23. Relative frequency of Yellowmouth Rockfish lengths by calendar year (1996–2007) and trip type. Lengths are binned using 2–cm intervals; n = number of fish, L = mean length (cm) (from Haigh and Starr 2008).

Multi-panel chart showing relative frequency of Yellowmouth Rockfish lengths by calendar year (1996 to 2007) and trip type.

Information on the current status and long–term productivity of Yellowmouth Rockfish populations in neighbouring waters to B.C. is extremely limited, as the species is typically grouped together with other slope rockfish. The population centre for the species appears to occur within its Canadian range. Data from triennial trawl suveys conducted in the Gulf of Alaska indicate that Yellowmouth Rockfish biomass was highly variable in the 1990s (e.g., ranging from 923 tonnes taken in 1996 to 5570 tonnes taken in 1999) (Heifetz et al. 2000). Results from the NMFS US triennial bottom trawl survey indicate that Yellowmouth biomass estimates for the US portion of the Vancouver INPFC region were much lower than for the Canadian portion (Fig. 17). In 2004 Yellowmouth Rockfish represented one of the top eight slope rockfish species harvested in Oregon (10 tonnes caught in bottom hauls) but did not figure in the top eight species for California or Washington (Roberts and Stevens 2006). Since the dispersal capability of the species is presently unknown it is difficult to determine the likelihood of recolonization of Canadian habitat following local extirpation.

Several characteristics of rockfish species make them particularly susceptible to disturbance. In particular, rockfish have relatively low intrinsic rates of increase due to their slow growth, delayed maturity and extreme longevity (Adams 1980; Roberts and Stevens 2006). Recruitment is highly variable and little is known about controlling factors. Many rockfish species exhibit site fidelity once maturity is reached, potentially resulting in small isolated populations vulnerable to localized depletion (Roberts and Stevens 2006). Co–occurrence with a number of other groundfish species makes fishery management at the species level challenging, although recent improvements to management of the groundfish species complex have been made to deal with this issue. Rockfish physiology makes these species prone to complete mortality when brought to the surface from depth (Fort et al. 2006; Haigh and Starr 2008). Taken together, these traits have led to declines in many slope rockfish as a result of overfishing, habitat loss from bottom trawling and adverse environmental changes (Roberts and Stevens 2006).

Commercial fishing is currently the main threat to Yellowmouth Rockfish. As for other rockfish, intensive fishing practices may disproportionately target the largest, oldest and most fecund Yellowmouth individuals, potentially leading to a truncated age distribution, loss of spawning biomass and diminished recruitment success (Berkeley and Markle 1999).

Yellowmouth Rockfish is captured mainly by bottom and mid–water trawls in BC, although a limited hook–and–line fishery also exists. The species is also taken in small numbers by the halibut fishery (Appendices 2–4). The trawl fishery for slope rockfish has been active since the 1930s but early catch statistics for Yellowmouth Rockfish are unreliable because several species were grouped together for catch reports. Furthermore, no data exist on historical discard levels in groundfish fisheries prior to 1995. Since the late 1970s reporting has improved significantly (DFO 1999a). Today the fishery has 100% observer coverage for bottom trawls and most mid–water trawls, in addition to 100% dockside monitoring, ensuring that all catches (including landings and discards) are enumerated (Roberts and Stevens 2006). In 2006 a three–year pilot plan was implemented to have 100% at–sea electronic and video monitoring for the hook–and–line fishery as well (DFO 2007).

The current standing stock of Yellowmouth Rockfish is unknown. The paucity of historical records on species composition in the commercial fishery makes it difficult to determine the current population status of the species along the BC coast. Data from more recent research surveys are also problematic as they tend to span too short a time period, target other species (e.g., shrimp) and/or do not adequately cover the preferred mid–water habitat of this species. In addition, Yellowmouth Rockfish may be mistakenly identified as Pacific Ocean Perch after capture, which could lead to underestimates of actual harvest or bycatch rates (Love et al. 2002).

Yellowmouth Rockfish is a commercially important species in BC (DFO 1999a). In the 2007–2008 fishing season, the total Canadian catch of Yellowmouth Rockfish had a landed value of approximately $1.5 million, based on a $0.50/lbs price (DFO 2008a).

The Monterey Bay Aquarium’s Seafood Watch Program has classified all slope rockfish as high conservation concern and inherently vulnerable (Roberts and Stevens 2006). The status of the Yellowmouth Rockfish has not been assessed by NatureServe (NatureServe 2007) nor by the BC Conservation Data Centre (Prescott pers. comm. 2007).

Yellowmouth Rockfish are currently managed by catch quotas, which were introduced in 1979. Yellowmouth catch within Area 5E (Langara Spit, northwest of the Queen Charlotte Islands) was managed under a slope rockfish aggregate (Yellowmouth, Pacific Ocean Perch and Rougheye Rockfish S. aleutianus) quota between 1983–1988 and in 1986 coastwide aggregate quotas were in place for these three slope rockfish species. In the past, quotas were based on observed relative abundance of Yellowmouth collected from biomass surveys. However, these surveys were directed at Pacific Ocean Perch, were limited to the Queen Charlotte Sound area (area 5AB) and relied solely on bottom trawl surveys (DFO 1999a; Schnute et al. 1999). Since 1997, quota determinations have also incorporated information from observer data onboard trawl vessels. In addition, the IVQ system was introduced for the BC trawl fishery in 1997, setting area–specific annual catch (retained and discarded) limits on quota species for each vessel.

The Canadian Yellowmouth Rockfish fishery is regulated by an individual quota set each fishing season. For the 2008–2009 fishing season 96.77% (2364 t) of the Yellowmouth total allowable catch (TAC) has been allocated to the trawl fishery, 2.49% (60 t) to the hook and line and 0.74% (18 t) to the halibut fishery. An additional three tonnes have been designated for research purposes (DFO 2008a). In the last two fishing seasons (2006–2007 and 2007–2008) Pacific groundfish trawl fleets have landed less than 60% of the Yellowmouth TAC (Table 4).

Table 4. Proportion of the total allowable catch (TAC) of Yellowmouth Rockfish caught in the groundfish trawl fishery during 2006–2007 and 2007–2008 fishing seasons (DFO 2008b).
Fishing season Total quota (tonnes) Total catch (tonnes) % of TAC harvested
2006–2007 2822.32 1665.02 59
2007–2008 2911.27 1397.86 48

In the US, Yellowmouth Rockfish are managed as part of slope rockfish assemblages to which a total allowable catch is assigned. Yellowmouth Rockfish likely receive partial protection from fishing in RCAs (from Washington to California) and in the eastern Gulf of Alaska where trawling is currently banned (Enticknap and Sheard 2005; Roberts and Stevens 2006).

Sebastes reedi
Yellowmouth Rockfish sébaste à bouche jaune
Range of Occurrence in Canada: Pacific Ocean (Marine waters along BC’s continental slope)
Demographic Information
Generation time (average age of parents in the population)
  • (assuming 50% maturity reached at 10 years and a natural mortality rate of 0.05)
30 yrs
Observed percent reduction in total number of mature individuals over the last 10 years or three generations:
  • see table summarizing indices (Table 3)
  • no stastically significant trends in individual research vessel surveys over varying periods. However, three of the four slope estimates were negative.
  • 99% decline over 40 years in index combining four RV surveys. However, these surveys had little spatial and temporal overlap
  • annual decline of 2.5% over 10 years in commercial CPUE index
  • reliability of all indices considered relatively low for this species
Indications of decline in surveys with longest time series and in commercial CPUE, possibly substantial
Projected or suspected percent reduction or increase in total number of mature individuals over the next 10 or 5 years, or 3 or 2 generations Unknown
[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over any [10 or 5 years, or 3 or 2 generations] period, over a time period including both the past and the future. Unknown
Are the causes of the decline clearly reversible? Unknown
Are the causes of the decline understood?
  • decline probably due to fishing potentially compounded by variable recruitment
Causes of variable recruitment not well known; fishing could be involved
Have the causes of the decline ceased?
  • fishing continues; recruitment remains variable
No
[Observed, inferred, or projected] trend number of populations N/A (single population)
Are there extreme fluctuations in number of mature individuals? No
Are there extreme fluctuations in number of populations? N/A
Extent and Area Information
Estimated extent of occurrence 48 000 km²
[Observed, inferred, or projected] trend in extent of occurrence Unknown
Are there extreme fluctuations in extent of occurrence? Probably not
Index of area of occupancy (IAO) 11 000–34 000 km²
[Observed, inferred, or projected] trend in area of occupancy Unknown
Are there extreme fluctuations in area of occupancy? Probably not
Is the total population severely fragmented? No
Number of current locations N/A
Trend in number of locations N/A
Are there extreme fluctuations in number of locations? N/A
Trend in area and/or quality of habitat Unknown
Number of mature individuals in each population
Population N Mature Individuals
Total Unknown
Number of populations (locations) N/A
Quantitative Analysis
Not carried out N/A
Threats (actual or imminent, to populations or habitats)
Commercial harvest may pose direct threats to populations through overfishing and indirect threats through habitat destruction caused by bottom trawling.
Rescue Effect (immigration from an outside source)
Status of outside population(s)?
USA: Information limited on current status in US waters. BC is probably the population centre of the species.
Is immigration known? No
Would immigrants be adapted to survive in Canada? Probably
Is there sufficient habitat for immigrants in Canada? Probably
Is rescue from outside populations likely? Unknown
Current Status
COSEWIC: Threatened (April 2010)
Status and Reasons for Designation
Status: Threatened Alpha–numeric code: A2b
Reasons for designation:
As with other rockfish species, this slow–growing (generation time 30 years), long–lived (maximum age 100 years) species is vulnerable to commercial fishing. Research vessel surveys indicate that abundance has declined considerably over the past 40 years (1.5 generations). While contemporary surveys designed specifically for groundfish species indicate a recent period (5 years) of relative stability, it is not clear that the decline has ceased. The initial period of decline occurred as the commercial fishery for this and other rockfish species developed. Although this is considered normal for a newly exploited population, the total decline in abundance is inferred to be well beyond what is optimal for an exploited population. The absence of any strong recruitment events during the last 20 years is also a concern. The species is an important component of BC’s commercial fisheries. Fishing continues to be a threat and there is no established limit reference point to help manage these fisheries in a precautionary manner.
Applicability of Criteria
Criterion A (Decline in Total Number of Mature Individuals): Meets Threatened A2b based on a suspected continuous long–term decline from an unfished condition to a level inferred to between 30 and 50% of the optimal level for an exploited population.
Criterion B (Small Distribution Range and Decline or Fluctuation): Not met as extent of occurrence and index of area of occupancy exceed thresholds.
Criterion C (Small and Declining Number of Mature Individuals): Not met as population size estimate not available, and certainly larger than threshold.
Criterion D (Very Small Population or Restricted Distribution): Not met.
Criterion E (Quantitative Analysis): Not undertaken.

The report writer is grateful to Rowan Haigh (Department of Fisheries and Oceans) and Paul Starr (Canadian Groundfish Research and Conservation Society) for their much appreciated assistance in the writing of this report. Environment Canada provided funding and support.

List of authorities contacted

Barry Ackerman, Groundfish Trawl Coordinator, Dept. of Fisheries and Oceans, Vancouver, BC.

David Clark, Ecological Information Specialist, Parks Canada, Gatineau, PQ

Ann Clarke, Science Officer, COSEWIC Secretariat, Ottawa, ON.

Lara Cooper, Canadian Science Advisory Secretariat, Dept. Fisheries and Oceans, St. Andrews, NB

Courtney Druce, Species at Risk Officer, Dept. of Fisheries and Oceans, Vancouver, BC.

Jeff Fargo, Head of Flatfish Assessment Program, Pacific Biological Station, Dept. of Fisheries and Oceans, Nanaimo, BC.

Alain Filion, Science Officer, COSEWIC Secretariat, Ottawa, ON.

Kevin Fort, Species at Risk Biologist, Canadian Wildlife Service, Delta, BC.

David Fraser, Species at Risk Specialist, BC Ministry of the Environment, Victoria, BC.

Monique Goit, Science Officer, COSEWIC Secretariat, Ottawa, ON.

Gloria Goulet, Aboriginal Traditional Knowledge Coordinator, COSEWIC Secretariat, Ottawa, ON.

Rowan Haigh, Research Biologist, Slope Rockfish, Pacific Biological Station, Dept. of Fisheries and Oceans, Nanaimo, BC.

Heather Holmes, Marine Ecologist, Pacific Rim National Park Reserve, Parks Canada, Ucluelet, BC.

Vicki Marshall, Fisheries Assessment Stock Coordinator, BC Ministry of the Environment, Victoria, BC.

Patrick Nantel, Conservation Biologist, Species at Risk Program, Parks Canada, Gatineau, PQ.

Harry Nyce, Sr., Nisga’a Wildlife Committee and Joint Fisheries Management Committee, Gitwinksihlkw, BC.

Sue Pollard, Aquatic Species at Risk Specialist, BC Ministry of the Environment, Victoria, BC.

Howard Powles, Marine Fishes Subcommittee, COSEWIC, Gatineau, PQ.

Erin Prescott, Information Specialist, BC Conservation Data Centre, BC Ministry of the Environment, Victoria, BC.

Norm Sloan, Marine Ecologist/Ecosystem Coordinator, Gwaii Haanas National Park Reserve and Haida Heritage Site, Parks Canada, Queen Charlotte, BC.

Paul Starr, Scientist, Canadian Groundfish Research and Conservation Society, Nanaimo, BC.

Jenny Wu, Data Management and Mapping Specialist, COSEWIC Secretariat, Ottawa, ON.

Lynn Yamanaka, Head of Inshore Rockfish Program, Pacific Biological Station, Dept. of Fisheries and Oceans, Nanaimo, BC.

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Andrea L. Smith obtained her M.Sc. in conservation biology and her Ph.D. in evolutionary ecology, both at Queen’s University. She has worked on a variety of research projects, including studying seabird ecology in British Columbia, the Canadian arctic and the Galapagos, endangered species in Hawaii and the Mojave desert, and forest bird communities in Mexico. Andrea has written several articles on environmental issues for the magazine ON Nature and conducted a gap analysis on provincial natural heritage policy for Ontario Nature. She now works as a researcher at York University’s Institute for Research and Innovation in Sustainability (IRIS), examining the interdisciplinary challenges of preventing and controlling invasive species.

No collections were examined for this report.

Six chart panels illustrating length-at-age relationships for specimens collected on a) non-observed domestic commercial trips, b) research surveys, c) charter surveys, d) domestic commercial trips, e) research and charter surveys combined, and f) all domestic commercial trips, using the von Bertalanffy growth equation.
Six chart panels illustrating length-at-age relationships for specimens collected on a) non-observed domestic commercial trips, b) research surveys, c) charter surveys, d) domestic commercial trips, e) research and charter surveys combined, and f) all domestic commercial trips, using the von Bertalanffy growth equation.
Six chart panels illustrating length-at-age relationships for specimens collected on a) non-observed domestic commercial trips, b) research surveys, c) charter surveys, d) domestic commercial trips, e) research and charter surveys combined, and f) all domestic commercial trips, using the von Bertalanffy growth equation.
Six chart panels illustrating length-at-age relationships for specimens collected on a) non-observed domestic commercial trips, b) research surveys, c) charter surveys, d) domestic commercial trips, e) research and charter surveys combined, and f) all domestic commercial trips, using the von Bertalanffy growth equation.
Six chart panels illustrating length-at-age relationships for specimens collected on a) non-observed domestic commercial trips, b) research surveys, c) charter surveys, d) domestic commercial trips, e) research and charter surveys combined, and f) all domestic commercial trips, using the von Bertalanffy growth equation.
Six chart panels illustrating length-at-age relationships for specimens collected on a) non-observed domestic commercial trips, b) research surveys, c) charter surveys, d) domestic commercial trips, e) research and charter surveys combined, and f) all domestic commercial trips, using the von Bertalanffy growth equation.
Year CA Trawl US Trawl Zn HL Shed II Halibut Total HL Total
1930
1931
1932
1933
1934 0 0
1935 2 2
1936 3 3
1937 3 3
1938 4 4
1939 4 4
1940 9 9
1941 3 3
1942 63 63
1943 204 204
1944 85 85
1945 14 887 901
1946 16 447 463
1947 0 234 234
1948 1 379 380
1949 1 461 463
1950 3 410 413
1951 7 410 417
1952 18 361 379
1953 2 142 144
1954 10 137 147
1955 12 179 191
1956 7 178 185
1957 10 118 128
1958 11 113 124
1959 38 124 162
1960 6 101 107
1961 9 146 155
1962 36 265 301
1963 17 261 278
1964 42 172 215
1965 34 229 263
1966 22 406 428
1967 27 333 360
1968 36 446 482
1969 45 809 854
1970 55 564 619
1971 66 520 587
1972 174 564 738
1973 142 727 868
1974 83 423 506
1975 110 250 360
1976L 189 189
1977 1,596 1,596
1978 1,214 1,214
1979L 438 438
1980 548 548
1981 1,039 1,039
1982 1,160 1,160
1983 1,524 1,524
1984 1,324 1,324
1985 1,628 1,628
1986 2,491 2,491
1987 1,857 1,857
1988 1,322 1,322
1989 1,611 0 0 1,611
1990 1,666 12 12 1,678
1991D 1,225 13 13 1,238
1992L 1,475 13 13 1,487
1993 1,157 10 10 1,167
1994D 1,231 12 12 1,243
1995T 1,391 24 2 26 1,417
1996D,O 1,402 12 6 19 1,421
1997Q,T 1,939 7 2 9 1,948
1998 1,795 9 2 11 1,806
1999 2,008 9 2 11 2,020
2000T 1,803 9 3 12 1,815
2001 1,930 10 4 15 1,945
2002 1,941 25 7 32 1,973
2003 1,860 14 0 8 22 1,883
2004 1,917 12 0 9 21 1,938
2005 1,816 15 5 20 1,835
2006 1,613 1,613
2007 1,680 0 11 11 1,691
Total 48,848 11,175 204 0 77 282 60,305

D Dockside monitoring program (DMP) started: 1991 – halibut; 1994 – trawl; 1996 – ZN H&L
O Obserwer program started: 1996 – ZN H&L
L Limited vessel entry: 1976 – trawl; 1979 – halibut; 1992 – ZN H&L
Q Individual vessel quota (IVQ) system started for TAC species: 1997 – trawl
T Trip limits implemented: 1995 – ZN monthly limit on rockfish aggregate; 1997 – trawl trip limit of 15,000 lbs for combined non–TAC rockfish; 2000 – halibut option D with annual limit of 20,000 lbs of rockfish aggregate.

Year n n+ E [B] B B0.05 B0.95 CV
2003 236 38 1814 1800 761 3399 0.364
2004 234 48 4256 4251 1165 9493 0.477
2005 224 44 1770 1782 667 3673 0.430
2007 257 75 1656 1625 838 2788 0.302
Year n n+ E [B] B B0.05 B0.95 CV
2004 98 2 29.3 28.9 0.0 82.0 0.736
2006 166 9 159.0 161.8 46.8 317.3 0.435
Survey
year
Relative biomass (t) Mean bootstrap biomass (t) Lower 95% bound biomass (t) Upper 95% bound biomass (t) Bootstrap
CV
Analytic
CV
1967 366.5 357.5 82.9 830.0 0.501 0.509
1969 321.8 325.5 38.1 749.2 0.581 0.570
1971 770.2 799.3 81.7 2393.3 0.795 0.836
1973 398.9 404.6 95.2 845.7 0.468 0.492
1976 418.9 418.4 73.6 1045.4 0.569 0.569
1977 26.3 26.0 4.3 72.7 0.658 0.645
1984 89.8 86.2 5.9 280.5 0.802 0.799
Survey
year
Relative biomass (t) Mean bootstrap biomass (t) Lower 95% bound biomass (t) Upper 95% bound biomass (t) Bootstrap CV Analytic
CV
1999 17.8 17.9 3.9 51.0 0.604 0.609
2000 26.3 26.3 0.0 97.8 0.911 0.937
2001 44.3 44.4 8.9 105.4 0.526 0.538
2002 97.3 96.5 9.3 351.2 0.871 0.835
2003 34.0 34.5 8.5 72.7 0.459 0.456
2004 36.0 35.1 7.8 87.7 0.567 0.584
2005 11.2 11.0 0.0 42.5 0.884 0.887
2006 55.8 56.7 7.0 135.1 0.533 0.539
2007 62.9 63.9 26.3 116.9 0.366 0.371
Estimate type Survey year Relative biomass (t) Mean bootstrap biomass Lower bound biomass Upper bound biomass Bootstrap CV Analytic CV
Total Vancouver 1980 139 141 0 361 0.609 0.661
1983 613 627 138 1608 0.575 0.585
1989 202 203 16 622 0.735 0.753
1992 15 14 2 43 0.713 0.726
1995 72 69 1 222 0.778 0.791
1998 6 6 0 20 0.925 1.000
2001 0 0 N/A N/A N/A N/A
Canada Vancouver 1980 151 153 0 391 0.609 0.661
1983 442 461 0 1478 0.746 0.739
1989 187 189 18 594 0.752 0.771
1992 11 10 0 41 0.898 0.917
1995 56 55 1 172 0.780 0.791
1998 4 5 0 17 0.931 1.000
2001 0 0 N/A N/A N/A N/A
U.S. Vancouver 1980 0 0 N/A N/A N/A N/A
1983 180 177 3 650 0.943 0.946
1989 14 14 1 36 0.624 0.616
1992 4 4 0 10 0.606 0.631
1995 16 15 0 51 0.825 0.791
1998 1 1 0 5 0.972 1.000
2001 0 0 N/A N/A N/A N/A
Year 3C 3D 4B 5A 5B 5C 5D 5E UNK CST
1971 5 5
1972
1973 177 177
1974 79 79
1975 0 1 2
1976 12 12
1977 333 3 4 1,257 1,596
1978 0 11 98 1,105 1,214
1979 2 0 6 25 405 438
1980 25 23 500 548
1981 0 0 46 69 925 1,039
1982 6 1 1 179 322 169 482 1,160
1983 33 40 411 342 58 640 0 1,524
1984 6 120 28 591 64 514 1,324
1985 4 412 128 371 37 0 676 1,628
1986 1 982 227 91 10 1,179 2,491
1987 7 703 439 82 67 0 559 1,857
1988 7 169 364 359 17 1 407 1,322
1989 43 315 599 245 24 386 1,611
1990 40 280 437 382 50 0 478 1,666
1991 37 217 490 339 20 1 121 1,225
1992 60 273 526 443 47 3 124 1,475
1993 48 301 383 247 19 2 157 1,157
1994 70 383 0 578 140 15 0 44 1,231
1995 65 275 672 290 16 1 72 1,391
1996O 112 242 0 487 418 26 0 116 1,402
97I 7 148 380 39 3 0 18 594
1997 24 326 882 642 20 7 38 1,939
1998 55 163 772 612 70 0 173 1,795
1999 66 97 802 758 66 1 220 2,008
2000 23 92 554 603 88 0 442 1,803
2001 42 82 809 521 43 1 432 1,930
2002 54 83 702 706 20 1 476 1,941
2003 22 30 0 820 617 31 0 340 1,860
2004 53 28 846 781 30 0 179 1,917
2005 24 22 596 971 40 2 161 1,816
2006 18 35 541 837 13 0 169 1,613
2007 21 44 0 370 992 8 12 233 1,680
Total 950 5,862 1 14,622 12,935 1,137 35 12,930 0 48,471

I Interim period (Jan–Mar) before implementation of IVQ in 1997 for offshore trawl. Fishing years prior to this period are calendar years; fishing yeas after this period run from April to March.
O Obserwer program started in 1996

Year 3C 3D 4B 5A 5B 5C 5D 5E UNK CST
1989 0.3 0
1990 0.5 2.2 0.1 0.3 0.5 0.7 0.5 6.9 12
1991 0.2 0.2 0.3 1.8 0.5 3.8 1.9 4.2 13
1992 0.0 1.0 5.6 0.0 0.4 5.5 13
1993 1.4 0.8 0.9 0.4 6.5 10
1994 0.0 9.6 0.1 1.7 12
1995 0.1 9.9 1.2 0.0 6.8 5.7 24
1996 0.0 0.7 7.8 0.0 0.2 3.0 0.6 12
97I 0.0 0
1997 0.2 1.9 0.1 0.0 1.3 3.2 7
1998 0.0 0.0 0.0 4.0 0.0 0.0 4.5 0.4 9
1999 0.1 0.2 4.5 0.0 0.0 0.0 3.4 0.4 9
2000 0.1 0.0 4.2 2.3 0.0 0.0 1.9 0.1 9
2001 0.0 0.0 6.5 1.8 0.0 0.0 1.7 0.1 10
2002 0.1 14.9 3.2 0.2 0.0 3.7 2.8 25
2003 0.1 6.3 7.0 0.2 0.7 14
2004 0.1 7.8 3.7 0.1 12
2005 0.1 0.0 12.8 1.9 0.0 15
2006 0.0 0
2007 0.0 0.0 0.2 0.1 0.0 0
Total 2 5 1 94 28 5 3 52 14 204

I Interim period (Jan–Mar) before implementation of IVQ in 1997 for offshore trawl. Fishing years prior to this period are calendar years; fishing yeas after this period run from April to March.

Year 3C 3D 4B 5A 5B 5C 5D 5E UNK CST
1995 0.0 0.0 0.0 0.0 0.0 2.1 2
1996 0.1 0.0 0.1 0.4 1.0 2.0 0.0 2.7 6
97I 0.3 0
1997 0.1 0.1 0.6 0.6 0.0 0.0 0.9 2
1998 0.0 0.2 0.2 0.5 0.9 0.3 0.0 0.0 2
1999 0.0 0.4 0.1 0.3 1.4 0.1 0.0 0.1 2
2000 1.6 0.6 1.1 0.0 3
2001 2.1 0.9 1.3 0.0 4
2002 3.5 1.2 2.7 0.0 7
2003 5.0 2.0 1.0 0.0 8
2004 4.7 1.9 2.7 0.0 9
2005 2.5 1.1 1.3 0.0 5
2006 0.1 0.2 8.3 5.0 0.0 0.0 0.1 14
2007 0.1 0.1 6.3 4.1 0.0 0.0 0.2 11
Total 0 21 0 16 20 2 2 11 6 78

I Interim period (Jan–Mar) before implementation of IVQ in 1997 for offshore trawl. Fishing years prior to this period are calendar years; fishing yeas after this period run from April to March.

Regional areas used in the halibut fishery are assigned to the following PMFCs: QC=5E, PR=5D, NC=5D, CC=5B, WC=2D, SG=4D. PFMA areas are assigned PMFC areas using PFMA centroids in PMFC polygons.

1 Note that in Fig. 3 all AO grid cells with fewer than three fishing vessels have been excluded due to privacy concerns. These grids are, however, included in all AO calculations.

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