Presentation on theme: "Icelandic cod HCR - lessons learned Einar Hjörleifsson Marine Research Institute Reykjavík, Iceland."— Presentation transcript:
Icelandic cod HCR - lessons learned Einar Hjörleifsson Marine Research Institute Reykjavík, Iceland
2 Personal background Academic: Biological oceanographer Professional Stock assessment within MRI NWWG and ACFM within ICES University teaching Communication & partnership with fishermen HCR - limited, but practical experience as being partly responsible for the numbers that the rule uses.
3 Talk structure Icelandic cod - current state of the resource The harvest control rule Stock assessment performance History of the responses to overestimation “Amendments” by fishery scientist Some of the lessons learned
4 Icelandic cod - status of resources
5 Icelandic cod - current status
6 The Icelandic cod HCR Rule recommended TAC T+1 = (0.22 Biomass T + TAC T )/2 Rule set for 1995 TAC T+1 = 0.25 (Biomass T + Biomass T+1 )/2 Additional constraints, min TAC = 155kt Modifications in 2000 TAC T+1 = 0.25 (Biomass T + Biomass T+1 )/2 Additional constraint, 30kt TAC buffer between years T: Assessment year
7 The HCR in numbers (kt)
8 Cod: Landings above advice/HCR
9 Assessment performance
10 Reason Overestimation of immigration Mean weight overestimated, capelin collapse Overestimation of immigration High “catchability”
11 Proportional error in assessment
12 This, despite reasonably good input data! Survey abundance indices Abundance of 3 year olds Abundance of 4 year olds
13 MRI response in 2000 Because the initial HCR was so tightly knit to stock assessment performance the initial evaluations focused on the fishery science June 2000, MRI asked John Pope to review the stock assessment for cod. The main conclusion was that the MRI May 2000 assessment was still overly optimistic with regard to estimating stock abundance in recent years, but that the methodology applied was essentially sound. Several alternative methods gave results with lower abundance in recent years, but all of the methods showed similar patterns in estimating stock abundance. Formally, Pope was not asked to address the HCR directly.
14 Government response in 2001 In response to further reduction in stock estimation in the 2001 assessment the government set up a group led by Rosenberg to address the following questions: 1) could the problem reasonably expect to have been foreseen on the basis of the observed patterns in the data? 2) can advice be provided that would help to avoid a repeat of such problems in the future? The short answer to questions were: If the question is “should this situation have been foreseen and prevented?”, then the answer is probably no. if the question is “could this situation have been foreseen and prevented knowing what we know now?” then the answer is probably yes. The Rosenberg report concludes with numerous additional advice both to scientists and managers -->
15 Rosenbergs general conclusion Managers need to be aware of not just the consequences of a decision, were it to be perfectly (at least on average) implemented. They need also to understand the likelihood of alternative, unintended outcomes, and their consequences. Depending on the result of a detailed risk analysis, the catch fraction in the catch control rule (25%) may need to be adjusted to take account of the probability that the actual catch fraction will exceed the intended level.
16 Rosenbergs general conclusion In essence, an effective and precautionary management procedure needs to respond quickly when stock status is declining and cautiously when it is increasing. Avoids imprudent increase in catch when the assessment indicates that stock is increasing. Essentially banks stock growth for future productivity. Avoids long-term damage to the fishery when the assessment indicates that the stock is decreasing. Reduces risk of reduction in productivity. Will over time stabilise the catches more effectively.
17 Government response in 2002 Appointed, in 2001, the HCR committee to evaluate the experience and explore alternative rules. Preliminary report came out in 2002 A final report is now on the ministers desk Recommend that the initially proposed catch rule should be adopted.
18 Some of the HCRC initial evaluation What if analysis: Yield profile based on various rules Proposed Initial Implemented No action
19 Some of the HCRC initial evaluation What if analysis: B4+ profile based on various rules Proposed Initial Implemented No action
20 Some of the HCRC initial evaluation Originally proposed HCR would have led to slower initial increases in catches than occurred. Originally proposed HCR would likely have led to higher current biomass than realised The exploitation rate would thus on average have been closer to intended target. Conclusion: What may be considered minor changes in the implementation of a HCR (percentage, reference period, etc.) may have significant effect.
21 The fisheries scientists response The evaluation of the high catchability in the late 90’s Currently not satisfactorily explained Catchability is in a sense a technical term describing deviations between different data, given model assumptions While not accounted for, could include numerous causes, not necessarily those related to q
22 Response by MRI Data & process used in models <2001 Tuning data: Surveys & CPUE from the fishing fleet Rely on one model, if similar as last year don’t worry Current data & process Tuning data: Survey indices only Run a variety of models each year, with varying assumption More than one assessor, working initially independently Changes considered to improve estimates hindsight analysis indicates that large overestimation might have been prevented if current approach used.
23 Retrospective analysis using current models
24 I cod - status & HRC projections
25 Some lesson learned I Despite poor recruitment, overestimation and implementation errors B4+ increased by 50% (1995-2004) Exploitation rates have been reduced, although still above long term target Subtle changes in HCR can have profound effects. Attempt has been made at improving the assessment process Alternative assumptions explored annually, uncertainty explored, more than one assessor But no guarantee that similar situation may not occur again.
26 Some lessons learned II Credibility of fishery science damaged (politicians, industry, public) Inclusion of buffer rules in HCR may for that reason alone be justifiable. Need for better communication about what can and cannot be achieved by current stock assessment methods Credibility not totally ruined, government, with the support of the industry and public, adheres to advice ---->
27 Advice and government decision For fishery year 2002-2003 Not included are stocks that are shared with other nations: Oceanic redfish, Greenland halibut, Atlanto-Scandian herring (Íslandssíld!), Blue whiting