1 / 24

Report of the 10 th Meeting of the Scientific Working Group

Report of the 10 th Meeting of the Scientific Working Group Port Vila, Vanuatu, 19 – 23 September 2011. Meeting of the Deepwater Sub-Group. Bottom Fishery Impact Assessments & Standard.

bwhiteside
Download Presentation

Report of the 10 th Meeting of the Scientific Working Group

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Report of the 10th Meeting of the Scientific Working Group Port Vila, Vanuatu, 19 – 23 September 2011

  2. Meeting of the Deepwater Sub-Group

  3. Bottom Fishery Impact Assessments & Standard • Australia tabled their bottom fishery impact assessment, which was reviewed and commented on by the SWG. The approach of submitting separate impact assessment and management response documents was encouraged. • The draft SPRFMO Bottom Fishery Impact Assessment Standard was finalised. Changes included: • All references to management implications or management responses to an identified risk were removed (e.g. definition of the historical fishing footprint, move-on rule weight thresholds). • Recommendations were included for finer scale (0.1°/ 6 minute) mapping of fishing effort, at the resolution of the data standard. (Penney 2011 - SP-10-DW-02) (DWSG Report, Sections 5 & 6)

  4. Meeting of the Jack Mackerel Sub-Group

  5. Jack Mackerel Catch Trends Reported and/or estimated total catches for the entire SE Pacific stock continued to decline to 522,440 t in 2011, 26% of the recent peak of 2 million t in 2007. There were substantial changes in the proportional contributions of catches by the various fleets between 2010 and 2011.

  6. Jack Mackerel Catch Distribution 2009 Jack mackerel catches off the south-central Chilean coast show a continuous distribution from the coast out to the westwards extent of the current high-seas fishery. In 2009 the SWG recommended that jack mackerel should be managed as one single management unit for the immediate future. There has been a substantial contraction in the abundance and geographic distribution of jack mackerel, with catches by the high-seas fleets extending westwards past 120°W in 2009, but only to about 84°W in 2011. There are also indications of periodic east/west shifts in stock distribution in response to oceanographic changes. 2011 2010 (EU 2011 National Report s, JMSG Report Section 8.4)

  7. Jack Mackerel Assessment Specifications Eight alternative specifications of the JJM model were run to explore the sensitivities to the main data inputs. The base case chosen was the same as the base case used in 2010. Models 2 and 3 were retained for robustness tests and projections. (JMSG Report Section 8.2)

  8. Jack Mackerel Recruitment Trend High jack mackerel catches in the 1990s resulted from steadily increasing recruitment (age 2) from 1970 to 1982, with two exceptionally strong recruitments in 1985 and 1986. Recruitment was below the long-term average from 1988 – 1997 and somewhat above average from 1998 – 2001. Recruitment has been below average since 2002 with five very weak year classes (25% of long term average) from 2006 – 2010. The updated assessment indicates that the 2010 year class was weaker than initially thought. There continue to be signs of a slow increase in recruitment. 2010 Estimate (JMSG Report Section 8.4, Annex JM-03 Fig 17)

  9. Jack Mackerel Fishing Mortality Trend In the updated assessment, fishing mortality (F) increased slowly from 1970 to reach about 0.19 in 1993, and then increased rapidly to 0.58 in 1997. Estimated F declined back down to recent low levels of 0.27 over 2002 - 2003 but has increased sharply again to 0.61 in 2009, the historically highest level. F is estimated to have decreased again to about 0.4 in 2011. An initial estimate of FMSY = 0.15. (JMSG Report Section 8.4, Annex JM-03 Fig 17)

  10. Jack Mackerel Fishing Mortality Trend In the updated assessment, fishing mortality (F) increased slowly from 1970 to reach about 0.19 in 1993, and then increased rapidly to 0.58 in 1997. Estimated F declined back down to recent low levels of 0.27 over 2002 - 2003 but has increased sharply again to 0.61 in 2009, the historically highest level. F is estimated to have decreased again to about 0.4 in 2011. An initial estimate of FMSY = 0.15. (* Additional figure by the SWG Chair)

  11. Jack Mackerel Assessment – F by Age Class Fishing mortality is highest on ages 5 to 12+, substantially exceeding FMSY on these ages since the early 1990s, particularly 1995 – 2002 and 2006 onwards. (JMSG Report Annex JM-03, Figs 14 & 15)

  12. Jack Mackerel Immature and Mature Biomass Trends Mature biomass declined rapidly after 1990 to a low level in 1999 before increasing again to a recent peak in 2004. Mature biomass has since declined to the historically lowest level in 2011. Immature biomass is estimated to have increased slowly from 2009 onwards as a result of some increase in recruitment. (JMSG Report Annex JM-03, Fig 18)

  13. Jack Mackerel Spawning Biomass Trend Spawning biomass is estimated to have declined below 40% of the unfished level in 1992, and to have declined below 20% of unfished mature biomass in 1996. The ratio of spawning biomass to the spawning biomass that would have existed had no fishing occurred is estimated to have declined to 5% in 2011.

  14. Jack Mackerel Spawning Biomass Trend Spawning biomass is estimated to have declined below 40% of the unfished level in 1992, and to have declined below 20% of unfished mature biomass in 1996. The ratio of spawning biomass to the spawning biomass that would have existed had no fishing occurred is estimated to have declined to 5% in 2011. (* Additional figure by the SWG Chair)

  15. Jack Mackerel Assessment - Projections 10-year projections of future total biomass (B) and fishing mortality (F) to 2021 were conducted assuming future recruitment at average levels from 2006-2010 (25% of the long-term average). Four constant catch scenarios were explored: 520,000t, 390,000t, 260,000t, 130,000t and 5,000t, these being approximately 100%, 75%, 50%, 25%, and 1% of the 2011 catch. Stochastic 10-year projections of spawning biomass (kt; left panel) and fishing mortality (average ages 2-12; right panel) for the base case model (Model 1) under the assumption that future recruitment has the same mean and variance as the 5-year period 2006-2010 (25% of long-term average), assuming a constant catch of 390,000 t (about 75% of 2011 catch). SSBmedian Fmedian (JMSG Report Section 8.4, Annex JM-03 Fig 22)

  16. Jack Mackerel Assessment – Projection Medians Projections of median spawning biomass (kt, left panel) and fishing mortality (over ages 2‐12; right panel) for the 2011 JM assessment base case model (Model 1) under the assumption that future recruitment has the same mean and variance as the 5‐year period 2006‐2010 and alternative constant future catch levels of 520,000t, 390,000t, 260,000t, 130,000t and 5,000t. Fishing Mortality Spawning Biomass (kt) (JMSG Report Section 8.4, Annex JM-03 Fig 24)

  17. Jack Mackerel Assessment – Projection Results • Projections indicate that, for the base case (Model 1), for the 2006 to 2010 5-year average recruitment scenario, there is a 21% probability of a decrease in spawning biomass under future constant catches of 520,000t, with median predicted spawning biomass in 2021 projected to be 1.23 times current spawning biomass. • Under the sensitivity analyses explored, for model 3 there is a 100% likelihood that spawning biomass will decline under catches at 520,000, whereas under model 2 there is a 0% probability of a decline, with spawning biomass predicted to increase to 1.7 times current levels by 2021. • Projections at catches of 390,000 t show a high probability of an increase in spawning biomass by 2021 under all model runs, with spawning biomass potentially increasing from 1.3 times to 2.2 times current levels. Probability of SSB2021 < SSB2012 Ratio of SSB2021 / SSB2012 (JMSG Report Section 8.4)

  18. Jack Mackerel Historical Trends in SSB Ratio and F Combining the historical trends in spawning biomass ratio (SSB / Unfished SSB, on the x-axis) with the historical trends in fishing mortality (F, on the y-axis), provides a stock status trajectory plot showing how SSB and F have varied over the history of the fishery. Because the jack mackerel stock undergoes substantial natural fluctuations, spawning biomass has to be expressed as a ratio of the estimated unfished SSB in each year, to allow years to be compared. F and SSB ratio provide the basis for dynamic reference points and this stock-status trajectory plot can be used to compare the status of the stock with any chosen reference level along the SSB-ratio and F axes. (* Additional figure by the SWG Chair)

  19. Jack Mackerel Historical Trends in SSB Ratio and F Historical trends in estimated jack mackerel spawning biomass ratio (SSB / UnfshedSSB) and fishing mortality (F) from 1979 to 2011 are compared here with some potential reference points : 40%UnfishedSSB, 20%Unfished SSB, FMSY and 2*FMSY. The stock first dropped below 40%UnfishedSSB and FMSY in 1992, with F> 0.3 after 1994. The stock declined below 20%UnfishedSSB in 1996, with F reaching very high levels by 1997. There was then a rapid decline in F to just below F=0.3 by 2000, followed by a slow recovery of SSB to around 20%UnfishedSSB in 2003 - 2005. F increased rapidly after 2005 to the historically highest level in 2009. As a result, SSB has declined to historically lowest levels (about 5% of Unfished SSB) in 2010/11 despite a decline in F after 2009. (* Additional figure by the SWG Chair)

  20. 2010 Advice on Status of Jack Mackerel In October 2010, In October 2010,the 9th meeting of the Scientific Working Group advised that: • “Jack mackerel catches have declined steadily since 2006, and continued to decline in 2010, with provisional (to September) 2010 catches being at the lowest level since 1976. … Assessment results indicate that total biomass has declined by 79% since 2001 to 2.1 million t, the lowest level in the history of the fishery. Current total biomass levels are estimated to be 9% - 14% of the biomass which would have existed if there had been no fishing. • Under 5-year average recruitment, for the base case assessment, there is a 100% probability that biomass will continue to decline at … 2010 catch levels (711,783 t), with projected biomass in 2020 of 10% of current biomass. At 75% of current catches, there is a 54% chance that biomass will continue to decline, with projected biomass in 2020 of 97% of current biomass. At 50% of current catches [355,500t], all models indicate that biomass will increase …” (SWG9 Report, October 2010)

  21. 2011 Advice on Status of Jack Mackerel Advice on jack mackerel stock status at the 2011 meeting was based on stock assessments conducted using the Joint Jack Mackerel (JJM) statistical catch-at-age model: • Jack mackerel catches by all but one of the fleets continued to decline in 2011, with overall 2011 catches being 69% of 2010 catches. Updated assessment results indicate that current biomass is now estimated to be 10% - 19% of the total biomass which would have existed if there had been no fishing, which is slightly higher than the estimated range from the 2010 assessment. The 2011 assessments results indicate a continuing decrease in fishing mortality and a slight increase in estimated total biomass over 2010, but a continuing decrease in spawning biomass.

  22. 2011 Advice on Status of Jack Mackerel • There continue to be indications of slightly improved recruitment in recent years, although the updated assessment indicates that the apparently strong recruitment observed by a number of fleets in 2010 was actually lower than the recruitment in 2009, and well below long-term average levels. Significant catches of 2 year old recruits were only made by the North Chilean (Fleet 1) fleet in 2011 and the resulting estimate of higher recruitment in 2011 is highly uncertain, and still well below long-term average levels. • Projection results under the assumption of average recruitment at the levels estimated for the recent five-year period 2006 – 2010 indicate that catches should be maintained below 520,000 t to maintain spawning biomass at least at current levels. Catches below 390,000 t are projected to have a high probability of resulting in spawning stock rebuilding under most projections.

  23. Approval and Actions Required The SWG is seeking approval and support for the following: • Bottom Fishery Impact Assessment Standard: Approval and adoption of the draft SPRFMO Bottom Fishery Impact Assessment Standard, to replace the SPRFMO interim Benthic Assessment Framework. • Jack Mackerel Stock Assessment: Consideration of extending Scientific Working Group meetings for an additional two days in years when jack mackerel assessments are conducted, to allow adequate time for preparation of input data, if this cannot be done inter-sessionally by flag states.

  24. Questions ?

More Related