Cusk (Brosme brosme) COSEWIC assessment and status report 2012
Official title: COSEWIC Assessment and Status Report on the Cusk Brosme brosme in Canada – 2012
Long description for title photo
Illustration of the Cusk, Brosme brosme, lateral view. There is one dorsal and one anal fin, both of which are elongate and extend posteriorly to a rounded caudal fin. There is a single barbel on the underside of the chin. The small pelvic fins are located below the rounded and brush-like pectoral fins.
Endangered
2012
Table of Contents
- COSEWIC Assessment Summary
- COSEWIC Executive Summary
- Technical Summary
- Preface
- Wildlife Species Description and Significance
- Distribution
- Habitat
- Biology
- Population Sizes and Trends
- Threats and Limiting Factors
- Protection, Status, and Ranks
- Acknowledgements and Authorities Contacted
- Information Sources
- Biographical Summary of Report Writer
List of Figures
- Figure 1. Cusk (Brosme brosme) (from COSEWIC 2003).
- Figure 2. Sample locations of the Knutsen et al. (2009) study, together with ocean topography and water masses of the North Atlantic Ocean; Rockall (RA) and Mid-Atlantic Ridge (MAR) are located on sea mountains surrounded by deep areas (white areas >1000 m depth and beyond the maximum depth range of Cusk); Greenland (GR), Iceland (IS), Faroe Island (FI), Storegga (SE) and Tromsøflaket (TF) are interconnected with depth <1000 m (grey shaded areas), and are within the recorded depth range of Cusk (from Knutsen et al. 2009).
- Figure 3. Distribution of Cuskin the Northwest Atlantic (from Brown et al. 1996).
- Figure 4. Global distribution of Cusk; relative probability of occurrence is based upon combination of modelled predictions and expert opinion using a variety of data sources (from Harris and Hanke, 2010; see AquaMaps for details).
- Figure 5. Statistical divisions of the Northwest Atlantic Fisheries Organization (NAFO).
- Figure 6. Comparison of Cusk distribution during 1970 – 85 (top panel) to that during 1995 – 2010 (bottom panel) as observed by DFO summer bottom trawl survey; scale is in thousands of individuals.
- Figure 7. Comparison of Cusk distribution during 1963 – 79 (top panel) to that during 1990 – 2010 (bottom panel) as observed by NMFS fall bottom trawl survey; scale is in kg per tow.
- Figure 8. Trend in DFO summer bottom trawl survey area occupied by Cusk; both total (km2) and proportional area are indicated.
- Figure 9. Percentage of commercial groundfish longline trips in 4Xnopq where Cusk were caught (prevalence – commercial fishery), percentage of Halibut industry survey stations which were sampled in all years where Cusk were caught (prevalence – Halibut industry) and percentage of 5 x 5 minute geographic blocks with groundfish longline effort in 4Xnopq where Cusk were caught (range – commercial fishery) (from DFO, 2008).
- Figure 10. Percent of NMFS fall bottom trawl survey sets that caught Cusk.
- Figure 11. Station distribution of 4VsW sentinel longline survey (a: top panel; + indicates pre-2004 stations and circle indicates post-2003 stations) and Atlantic Halibut industry longline survey (b: bottom panel; open circles indicate Halibut survey sets and + indicates DFO summer survey sets for 2000 – 2010).
- Figure 12. Time series of annual surface salinity anomalies (grey dashed line with dots) and 5-year running means (heavy, black line) (from Worcester et al. 2010).
- Figure 13. Mean annual (dashed line) and 5-year running mean (solid line) of the stratification index over the Scotian Shelf; anomalies based on 1971-2000 observations; standard error estimates for each annual value are shown (from Worcester et al.2010).
- Figure 14. Relationship between Cusk proportion mature (sexes combined) and length (cm) based on an analysis of DFO and NMFS spring – summer surveys.
- Figure 15. Growth models of Scotian Shelf and Gulf of Maine estimated by Oldham (1972) and O’Brien (2011) respectively.
- Figure 16. Distribution of Cusk eggs on the Scotian Shelf based upon SSIP sampling during 1978 – 82 (from Harris et al.. 2002); scale in eggs /m3 with + designating no. eggs caught.
- Figure 17. Change in weight (kg) of 65 cm Cusk during 1970 – 2010.
- Figure 18. Share of longline fleet landings in all NAFO areas by tonnage class.
- Figure 19. Trend in annual number of trips fished by tonnage class 2 and 3 longlines in NAFODivs. 4X and 5.
- Figure 20. Trend in abundance of immature (<42 cm) and mature (42 cm+) Cusk in NAFODivs 4VWX, based upon DFO summer bottom trawl survey.
- Figure 21. Decadal change in length frequency of Cusk in NAFODiv 4VWX as observed by DFO summer bottom trawl survey.
- Figure 22. Trend in abundance of immature and mature (53 cm+) Cusk in NAFODivs 5Z-6, based upon NMFS fall bottom trawl survey.
- Figure 23. Decadal change in length frequency of Cusk in NAFODiv 5Z-6 as observed by NMFS fall bottom trawl survey.
- Figure 24. Trends in Cusk biomass indices (kg / 1000 hooks) based on Industry Atlantic Halibut survey. The legend is as follows: LM is the GLM estimate assuming lognormal error, GLM NB is the GLM estimate assuming negative binomial error (this is the index used in trend analysis), and Average is the simple mean of the fixed station catch rates.
- Figure 25. Temporal change in Cusk proportion at length in industry Atlantic Halibut survey.
- Figure 26. Comparison of Cusk average proportion at length observed in the Halibut and DFO summer trawl survey during 2000 – 2010.
- Figure 27. Trends in CPUE indices for tonnage class 2 and 3 longliners fishing in NAFODiv 4X5 during July – September; note that the Harris & Hanke (2010) index was only for NAFODiv 4X.
- Figure 28. Decadal changes in landings of tonnage class 2 and 3 longliners operating in NAFODiv 4X5 during the 2nd and 3rd quarters of the year.
- Figure 29. Observed (dots) and model predicted (lines) ln(indices) of Cusk biomass; 4X5 longline CPUE (top panel) and DFO summer survey (bottom panel).
- Figure 30. Posterior density plots of model parameters; tau.com and tau.rv are the observation error on the CPUE and DFO survey indices, s is the process error, Commercial and Survey Q are the CPUE and DFO survey catchability; the remaining legends are self-explanatory.
- Figure 31. Trend in proportion that annual Cusk biomass is of carrying capacity (K) from state – space model; 25th, 5th (median) and 75th percentiles provided.
- Figure 32. Cusk abundance indices from the DFO trawl survey adjusted for hyperdepletion, the commercial longline CPUE, and the Halibut longline survey, standardized to their 2000 – 2010 means.
- Figure 33. Log linear regressions of Cusk abundance from the DFO trawl survey index (1974-2010), the same index adjusted for hyperdepletion, the commercial CPUE index (1986-2010) and the Halibut longline survey (1999-2011). The range of the y-axis values in each panel is the same thus allowing visual comparison of the estimate slopes.
- Figure 34. Trend in Ln Proportion annual biomass of carrying capacity from Bayesian Surplus Production Model.
- Figure 35. Total annual reported landings of Cusk in the Northwest Atlantic.
- Figure 36. Longline landings of Cusk by quarter of the year.
List of Tables
- Table 1. Number of Cusk observations (individual fish) made on DFO Maritimes Science surveys.
- Table 2. Number of Cusk observations (individual fish) made on NMFS Science surveys.
- Table 3. Summary of key features of industry surveys conducted in Scotian Shelf – Gulf of Maine area.
- Table 4. Number of fixed stations sampled during 4VsW Sentinel and Atlantic Halibut surveys.
- Table 5. Association between Cusk catch, depth, and bottom temperature on the Scotian Shelf as observed in the DFO summer bottom trawl survey during 1970 – 2010; top panel enumerates total number of sets and bottom panel enumerates only those sets on which Cusk were caught.
- Table 6. Number of longline and trawl trips with observer coverage during 1977 – 2011 in NAFODiv. 4X5.
- Table 7. Number of DFO Maritimes Science commercial port samples of Cusk by gear (otter trawl, line and gillnet) and quarter during 1960 – 2010.
- Table 8. Abundance (000s) and biomass (t) indices of Cusk from DFO summer bottom trawl survey.
- Table 9. Abundance (000s) and biomass (t) indices of Cusk from NMFS fall bottom trawl surveys.
- Table 10. Indices of Cusk biomass estimated from Industry Atlantic Halibut survey. Units are undefined.
- Table 11. Cusk catch rate indices based upon analysis of commercial tonnage class 2 and 3 longline catch rates (t/trip) in NAFODiv 4X – 5 during July – September.
- Table 12. Summary of posterior quantiles of parameters for Bayesian State – Space model of Cusk; Process, Obs, CPUE and Obs, RVare the process error and observation error on the two biomass indices, P1970 and P2010 are biomass / K for the indicated years. Units for MSY and BMSY are tonnes.
- Table 13. Summary of log-linear regression results for the various abundance indices for Cusk. Slope estimates are presented for three time periods (12, 24 and 36 years). The final column gives the estimated percent change in abundance for each time period.
- Table 14. Percent decline in proportion biomass of carrying capacity during 1970 – 2007 under different catch, CPUE and DFO summer survey updates to Bayesian surplus production model of Davies and Jonsen (2011).
- Table 15. Reported landings (t) of Cusk for all countries by NAFO Statistical Areas.
- Table 16. Canadian landings (t) of Cusk by NAFO Statistical Area.
- Table 17. US landings (t) of Cusk by NAFO Statistical Area.
- Table 18. Canadian Cusk landings (t) in the Northwest Atlantic by gear.
- Table 19. Cusk discard rates (kg Cusk discarded per kg of all species landed; courtesy of K. Clark) (from study by Gavaris et al.. 2010).
- *Table 20. Comparison of 2005-06 and 2009-10 Cusk bycatch studies (from Pezzack 2011).
- *Table 21. Comparison of Cusk discards in Southwest Nova Scotia Lobster fishery determined by Gavaris et al. (2010), the 2005-07 study of Harris and Hanke (2010) and the 2009-10 study of Pezzack (from Pezzack 2011).
- Table 22. Cusk discards (t) in Southwest Nova Scotia Lobster fishery estimated based upon recent DFO discard studies.
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