Assessment and Management of the South African Purse-Seine Fishery for Small Pelagics

Transcription

1 Assessment and Management of the South African Purse-Seine Fishery for Small Pelagics (Sardine, Anchovy and Round-Herring) NOAA Southwest Fisheries Science Centre & PFMC Workshop on Coastal Pelagic Species Assessments La Jolla 3 rd May 2016 Carryn de Moor, Doug Butterworth, Janet Coetzee Marine Resource Assessment and Management Group (MARAM) Department of Mathematics and Applied Mathematics University of Cape Town

2 risk A Outline Basic Ecology History of Fishery Data Available for Assessments Stock Assessment Results Annual OMP Application Process The Joint Sardine-Anchovy OMP Round Herring Approach Key Issues for Future Assessment and Management Research Related Issues - Penguins

3 risk A Outline Basic Ecology History of Fishery Data Available for Assessments Stock Assessment Results Annual OMP Application Process The Joint Sardine-Anchovy OMP Round Herring Approach Key Issues for Future Assessment and Management Research Related Issues - Penguins

4 Annual Recruitment Process

5 Biological Parameters Anchovy Sardine Round Herring Max length observed 15.5cm CL 23.5cm CL 25.0 cm Max age observed 5 years 10 years 8 years (female only) Juvenile M 1.2 year year year -1 Adult M 1.2 year year year -1 Age at maturity ~1 year ~1-2 years? Length at 50% maturity 10.6 cm cm 14.5 cm van der Lingen et al. (2006) AJMS 28(3&4): B. A. Roel & Y. C. Melo (1990) SAJMS 9:1,

6 risk A Outline Basic Ecology History of Fishery Data Available for Assessments Stock Assessment Results Annual OMP Application Process The Joint Sardine-Anchovy OMP Round Herring Approach Key Issues for Future Assessment and Management Research Related Issues - Penguins

7 Catch History Small Pelagic Fishery: primarily sardine and anchovy, also round herring, chub mackerel and juvenile horse mackerel

8 risk A Important Aspects Annual value : $200 million (30% of total for SA fisheries; hake dominates at 40%) Adult sardine preferred : the most valuable as can-able for human consumption (balance to fishmeal) Anchovy essentially available only as recruits on west coast over April-July Technological interaction : unavoidable juvenile sardine bycatch with anchovy

9 risk A Outline Basic Ecology History of Fishery Data Available for Assessments Stock Assessment Results Annual OMP Application Process The Joint Sardine-Anchovy OMP Round Herring Approach Key Issues for Future Assessment and Management Research Related Issues - Penguins

10 Available Data November hydroacoustic survey May hydroacoustic survey Nov survey length frequencies May survey length frequencies Monthly Commercial length frequencies Other 1984 (total biomass) Anchovy Sardine Round Herring 1985 (recruit numbers) 1984 (total biomass) 1985 (recruit numbers) Only used to separate out recruit biomass Only used to separate out recruit biomass 1987 (total biomass) 1987 (total biomass) DEPM estimates of SSB Parasite prevalence-atlength *NEW*

11 Hydro-acoustic Surveys: Anchovy May 2015 Recruit survey November 2015 Biomass survey

12 Hydro-acoustic Surveys

13 risk A Outline Basic Ecology History of Fishery Data Available for Assessments Stock Assessment Results Annual OMP Application Process The Joint Sardine-Anchovy OMP Round Herring Approach Key Issues for Future Assessment and Management Research Related Issues - Penguins

14 risk A Basics of Assessment Approach Bayesian analysis SCAL (Age-structured at base, but fit to length-structured data) Fit to hydro-acoustic survey estimates of abundance together with November survey and commercial CAL data Anchovy: - Estimate Beverton-Holt S/R curve - Egg survey assumed absolute - Uninformative or hardly informative prior distributions for all estimable parameters (includes those of growth curve) Sardine: - Estimate hockey-stick S/R curve - Informative prior distributions for acoustic survey bias based on distribution of individual acoustic survey errors - All other priors uninformative or hardly informative

15 Anchovy Total Biomass ('000t) Recruits (in billions) Year Year Survey estimates of abundance ( s) shown with 95% CIs Recruits (in billions) Spawner Biomass ('000t)

16 risk A Sardine de Moor and Butterworth (2015) AJMS 37(1):41-51

17 risk A Outline Basic Ecology History of Fishery Data Available for Assessments Stock Assessment Results Annual OMP Application Process The Joint Sardine-Anchovy OMP Round Herring Approach Key Issues for Future Assessment and Management Research Related Issues - Penguins

18 Management Schedule during season November acoustic survey Estimate of biomass Directed sardine TAC OMP (December) May acoustic survey Initial anchovy TAC Initial sardine TAB Estimate of recruitment Further survey and commercial data OMP (June) Revised and final anchovy TAC Revised and final sardine TAB de Moor and Butterworth (2016) Management Science in Fisheries Chapter 11

19 risk A Outline Basic Ecology History of Fishery Data Available for Assessments Stock Assessment Results Annual OMP Application Process The Joint Sardine-Anchovy OMP Round Herring Approach Key Issues for Future Assessment and Management Research Related Issues - Penguins

20 risk A Basics of OMP Approach Used for Management Pre-agreed TAC (and TAB) decision rules selected following simulation testing Constraints on extent of inter-annual TAC changes Empirical TACs calculated directly from survey results (and some commercial data) Joint sardine-anchovy procedure unavoidable juvenile sardine bycatch with anchovy Exceptional Circumstances constraints overridden if survey results below threshold

21 Sardine Harvest Control Rule Directed Sardine TAC (in 1000t) Min TAC Harvest Proportion Observed Sardine Biomass (in 1000t) Observed Sardine Biomass (in 1000t) Max TAC Constrained by max 20% inter-annual reduction Exceptional Circumstances Small sardine TAB = 7% of sardine TAC + fraction (dependent on current sardine biomass and juvenile sardine:anchovy catch ratio) of anchovy TAC

22 Sardine Harvest Control Rule Directed Sardine TAC (in 1000t) Harvest Proportion Observed Sardine Biomass (in 1000t) Observed Sardine Biomass (in 1000t) Biomass = t Biomass = t

23 Sardine Harvest Control Rule Directed Sardine TAC (in 1000t) Observed Sardine Biomass (in 1000t) Normal Industry Preservation Resource Preservation 0.5 Harvest Proportion Observed Sardine Biomass (in 1000t)

24 risk A Anchovy Harvest Control Rules Initial anchovy TAC: Max 25% inter-annual decrease in TAC (unless TAC is very high) Final anchovy TAC: No TAC decrease at finalisation B y,n obs,a - November survey biomass estimate N A y-1,rec0 - November recruit number back-projected from May survey estimate

25 risk A Sardine-Anchovy Trade-Off risk S <0.21 Average Directed Sardine Catch (1000t) Average Anchovy Catch (1000t) risk A <0.25 risk S the probability that sardine 1+ biomass falls below the average 1+ biomass over Nov at least once during the 20 year projection period risk A the probability that anchovy 1+ biomass falls below 10% of the average 1+ biomass over Nov at least once during the 20 year projection period

26 risk A Risk Level : Consider Extent of Depletion Anchovy Sardine No catch OMP-14 No catch OMP Biomass in 2023 ('000t) Biomass in 2023 ('000t)

27 Risk Level: SA sardine 2002 No catch OMP Consider lower percentiles of B OMP /B F= Sardine 1+ Biomass in 2020 ('000t) No catch OMP-04 Maintain a similar level of downward shift under proposed new MP Sardine 1+ Biomass in 2023 ('000t) 2008 No catch OMP Sardine 1+ Biomass in 2027 ('000t)

28 risk A Outline Basic Ecology History of Fishery Data Available for Assessments Stock Assessment Results Annual OMP Application Process The Joint Sardine-Anchovy OMP Round Herring Approach Key Issues for Future Assessment and Management Research Related Issues - Penguins

29 risk A Round Herring Assessment and Management A precautionary upper catch limit (PUCL) of t applies; this is ~ 8% of average recent Nov survey biomass PUCL decrease linearly if Nov survey biomass < t Round herring not an immediate assessment priority as currently underutilised Noted as potential area for expansion in industry (more jobs) - this would increase the priority for a more advanced management approach needing a reliable assessment method Assessment assumes multiple cohorts of recruitment each year Remaining problem is fitting adequately to commercial and survey CAL distributions Rather consider selectivity-at-length?

30 risk A Outline Basic Ecology History of Fishery Data Available for Assessments Stock Assessment Results Annual OMP Application Process The Joint Sardine-Anchovy OMP Round Herring Approach Key Issues for Future Assessment and Management Research Related Issues - Penguins

31 risk A Sardine Stock Structure Higher exploitation levels of sardine in the west

32 risk A Sardine Stock Structure Higher exploitation levels of sardine in the west Evidence for spatial structure parasite data reflect west-to-south movement Assessment as two stocks including movement in progress

33 risk A Sardine: November Biomass de Moor and Butterworth (2015) AJMS 37(1):41-51

34 risk A Sardine: May Recruitment Note different scales on the vertical axes de Moor and Butterworth (2015) AJMS 37(1):41-51

35 risk A Sardine: Hockey-Stick S/R Curve Note different scales on the vertical axes de Moor and Butterworth (2015) AJMS 37(1):41-51

36 risk A Sardine Stock Structure Higher exploitation levels of sardine in the west Evidence for spatial structure parasite data reflect west-to-south movement Assessment as two stocks including movement in progress Concern that south component appears relatively unproductive Interim arrangement for limitation on proportion (based on 2 most recent surveys) of TAC caught west of Agulhas pending OMP revision based on two-stock model

37 risk A Anchovy Concern re under-catching Several factors including environmental legislation, weather and the environment impact on the economics, fishing and processing capacity and catchability of anchovy

38 risk A Ageing Concern that limited research resources for Government Department have meant very little attention in recent years to ageing of sardine and anchovy

39 risk A Outline Basic Ecology History of Fishery Data Available for Assessments Stock Assessment Results Annual OMP Application Process The Joint Sardine-Anchovy OMP Round Herring Approach Key Issues for Future Assessment and Management Research Related Issues - Penguins

40 African Penguin Islands on West Coast Robinson et al. (2015) ICES JMS 72(6):

41 African Penguin Model Results Model fitted to moult counts and tag-recapture data Robinson et al. (2015) ICES JMS 72(6):

42 African Penguin Model Results Adult survival drops at low sardine biomass Robinson et al. (2015) ICES JMS 72(6):

43 African Penguin Model Results No relationship found between reproductive success and forage fish abundance Robinson et al. (2015) ICES JMS 72(6):

44 risk A Island Closure Experiment Commenced 2008 Basic approach: 3-year alternate open/closed to fishing at Robben and Dassen Islands Monitor reproductive indices attempt to differentiate effects of abundance and catch under simulation study to check potential biases results will await international panel review

45 risk A Cost to Industry of Closures Catch rate differential close to vs far from islands effect on costs minimal Opportunity loss model approach (anchovy availability is irregular) Estimated annual cost to industry: $2 million per closure per year

46 Assessment and Management of the South African Purse-Seine Fishery for Small Pelagics (Sardine, Anchovy and Round-Herring) Thank you for your attention Marine Resource Assessment and Management Group (MARAM) Department of Mathematics and Applied Mathematics University of Cape Town