The Study Group examined the current EC recovery plan proposals for rebuilding 4 cod stocks and 1 hake stock within EU waters. Table 6.1 lists the stocks and their relevant statistics. Background and source material for this section comprised the Norway-EU agreement, an STECF report (Anon 2002d) and an EU consultation document outlining the proposed EU Council Regulation to establish measures for the recovery of cod and hake stocks.
EU recovery plans are a response to ICES advice that there should be a safe and rapid recovery of the relevant. The EU proposal is to establish a recovery programme that rebuilds the tonnage of mature fish to a target level equal to or
i) SSB should increase by 30% (cod) and 15% (hake) per year ii) TAC variability should not to be greater than +/- 50 %
iii) the TAC should not generate a value of F greater than that specified for each stock (the values specified coincide with Fpa, but the term Fpa is not explicitly mentioned)
iv) The target SSB should be reached for 2 consecutive years before recovery plan status is removed.
The EU has requested an ICES view of the plans. The Study Group therefore carried out a qualitative audit of the proposals. It also discussed the developing use of a quantitative simulation framework that could evaluate the suitability of different recovery strategies taking into account various sources of uncertainty, and different assumptions about model structure and the effectiveness of management measures in the real world.
7.2.1 The qualitative audit
The Study Group reviewed the EU proposals in the light of the four STECF criteria.
(1) A measure of stock status
The status of the recovery stocks has been measured against the current ICES reference point values using the ICES assessment output (Anon, 2002a), as shown by the SSB and Blim values in Table 7.1. It is traditionally assumed that this diagnosis is affected only by the uncertainty associated with assessment data (landings, catch-at-age, weight-at-age), and the determination of reference points within a single assessment model structure. However, Patterson et al (2001), and Section 3.4 of the present report, describe the issue of assessment model structure uncertainty. For Northern hake, Section 3.4 showed that the final assessment configuration adopted by a working group is only one of a number of possibilities. Each outcome provides a different perception of the risk to the stock associated with the consequences of fisheries management decisions, and without additional information there is no objective way of choosing between them. Where such multiple scenarios based on alternative models are equally valid, there is no formal procedure for quantifying the additional uncertainty and including it within the specification of the recovery plan.
Table 7.1 SSB, biomass reference points, and recovery parameters for five EU stocks
Stock SSB 2002
(2) The target recovery period
The target recovery period does not appear to be stated explicitly in the plans, but it can be inferred indirectly from the starting SSB, and the target increases in SSB specified for each species. A per annum increase in SSB of 15% for hake and 30% for cod produces an implied recovery time shorter than the calculated generation time, and in that sense could be deemed as compatible with the precautionary approach, but only if the assumptions about recruitment are fulfilled.
Whether recovery is actually achievable on this scale in practice depends on the effectiveness of the management measures that are taken, and on the recruitment that actually materialises. For hake (maturing at 5 years) this may be less critical, but for cod (maturing at 2-4 years) the rate of SSB increase could be more variable. The use of a single biomass criterion for recovery also ignores the differences in biology between cod stocks, and the different level of these stocks relative to their reference points.
(3) The recovery trajectory
The recovery plan trajectory specifies a 15 % SSB increase per annum for hake and 30% increase per annum for cod.
The proposal does not explain the basis for this choice, or link it specifically to any biological analysis of the severity of the problem. The current plan stipulates that the recovery target has to be achieved for 2 consecutive years. It does not discuss how to distinguish between transient or equilibrium states, or the uncertainty of abundance estimation, or the fact that assessments are working in arrears.
(4) The long-term management objective
Bpa is being used as the target in each plan, and no other explicit management objective has been proposed. A long-term objective beyond Bpa deserves serious consideration, however, in order to move stocks away from Bpa, and prevent them from switching recovery procedures off and on in response to short-term stock fluctuations around Bpa. The present measures may therefore be acceptable as a first step but the SG suggests that a long-term management strategy should already be under discussion as part of the recovery plan, especially given the ‘cost’ of engagement with managers and stakeholders.
Although these stocks are below Blim and are well below Bpa, the risk of actual collapse is difficult to define. There is an obvious fear that further years of poor productivity and recruitment could be fatal, yet some stocks have been at or close to their current level for ten years (eg, N Sea cod). In addition to biomass, however, a long-term objective should give serious consideration to the age diversity of the stock, which in most cases is seriously diminished, with possible consequences for reproductive health. Although one or two good year-classes might result in a reasonably rapid attainment of Bpa, the biological requirement to increase age diversity and optimise reproductive potential might take much longer. Although age structure aspects are not included in a precautionary approach based solely on biomass reference point criteria, they are more implicit if management is based on fishing mortality criteria. The most effective long-term target may therefore be to reduce F to at least Fpa, or less, in order to stabilise SSB above Bpa and also improve age diversity. The question of long-term objectives and target reference points is considered in more detail in Section 6.
It is questionable whether sufficient attention has been paid to the issue of carrying capacity. The assumption is that environmental conditions and other constraints will not limit the attainment of the proposed targets. A recent analysis of historical data back to the XVIIth century has shown that the East Atlantic and Mediterranean bluefin tuna displayed significant long-term fluctuations in abundance (Ravier and Fromentin 2001). Such results indicate that carrying capacity could strongly vary over time, and that a single long-term biological reference point may not be appropriate.
The effect of periodic environmental fluctuations on the abundance of cod stocks in the N E Arctic and the Eastern Baltic has already been discussed in Section 4. Long-term fluctuations in abundance have been also documented in several important stocks of cod and herring.
7.2.2 Progress towards implementation
Progress towards implementation has already commenced through the TACs agreed for 2002. Using the ACFM catch-option tables, the Study Group therefore compared this 2002 TAC to the landing required to achieve the first annual increment in SSB during 2002, on the basis of the current assessment data, and assuming no other changes. The conclusions are that in the case of North Sea Cod, the agreed TAC matches what is required to implement the first year SSB target. In Irish Sea and West of Scotland Cod, the agreed TAC is lower than required by the plan, potentially leading to a quicker recovery than that required by the SSB target. For Kattegat Cod and Northern Hake the 2002 TACs will only promote an SSB increase of 15% for cod (instead of 30%) and 9% for hake (instead of 15% required). The basis for these conclusions is as follows:
The North Sea Cod example
In the 2001 assessment, SSB (2002) is estimated as 55kt, compared to Bpa of 150kt.
In round figures the required 30% increase in SSB (kt) per year is:
SSB should reach Bpa in 2006. From the ACFM catch option table for 2002, landings of no more than 58kt would be required to achieve SSB of 72kt in 2003.The agreed 2002 TAC is 58kt (including 1.6kt for the VIId component of the stock), which is consistent with the SSB objective.
7.2.3 The Irish Sea Cod example
SSB (2002) is 5.8kt, compared to Bpa of 10kt.The required 30% increase in SSB (kt) per year is 2002 5.8
2003 7.5 2004 9.8 2005 12.7
SSB should reach Bpa in 2004-2005. From the ACFM catch option table, landings of no more 4.0kt are required to achieve SSB at 7.5kt in 2003. The agreed 2002 TAC is 3.2kt, which should allow SSB to recover much more quickly than required by the recovery plan. SSB would then be close to Bpa in 2003.
7.2.4 The West of Scotland Cod example
SSB (2002) is 5.7kt, compared to Bpa of 22kt. The required 30% increase in SSB per year is:
2002 5.7
2003 7.4
2004 9.6
2005 12.5
2006 16.3
2007 21.2
2008 27.5
This stock is so low that SSB is unlikely to reach Bpa until 2007-2008. From the ACFM catch option table, landings of no more than 4.3kt would be required to achieve SSB at 7.4kt in 2003. The agreed 2002TAC is 3.9kt (0.7kt for the VIb component of the TAC excluded), which should allow SSB to recover slightly more quickly than required by the rebuilding plan.
7.2.5 The Kattegat Cod example
SSB (2002) is 5.2kt, compared to Bpa of 10.5kt. The required 30% increase in SSB per year is:
2002 5.2
2003 6.8
2004 8.8
2005 11.4
SSB should reach Bpa in 2004-2005. From the ACFM catch option table, landings of no more than 2.2kt would be required to achieve SSB at 6.8kt in 2003. The agreed 2002TAC is 2.8kt, which would allow SSB to recover by only 15%.
7.2.6 The Northern Hake example
The required SSB in 2002-2006 depends on the assumption for F in 2001 for which ACFM considered two scenarios, F (status quo), or F (TAC constraint). The 15% increase in SSB would require F to be reduced by 50%in both cases, but with the TAC constraint, the recovery period would be shortened, since SSB would reach Bpa (165kt) in 2005, instead of 2006.
(Fsq) (TAC constraint)
2002 98 115
2003 113 132
2004 130 152
From the ACFM catch option tables, landings of 20kt are required to achieve SSB (2003) of 113kt or 132kt respectively. The agreed 2002TAC of 26kt corresponds to SSB (2003) of 107kt and 126kt respectively, an increase of no more than 9%.
These scenarios do not take into account the following factors:
a) sources of assessment uncertainty that affect the current estimate of stock status, or stock status in the future as the recovery plan proceeds. If the stock is, for example, overestimated, the resulting TAC could lead to an increase in effort as catchers seek to achieve their quotas, and this could alter or even halt the trajectory of the recovery.
b) the effect of technical conservation measures that are also being negotiated as part of the recovery plan package c) technical interactions that could cause rebuilding plans to deviate from the desired trajectory through adjustments
in species targetting, leading to unpredicted by-catches of the recovery plan species.
d) the effect of compensatory fishing behaviour such as mis-reporting, or the adoption of technological improvements to counteract perceived restrictions arising from a recovery plan. Although compliance is a tendentious area that is difficult to address, it is relevant to assess what level of non-compliance would compromise the plan. The Study Group did not atempt to evaluate this but it should be included in the specification for an evaluation by simulation.
There may well be a case for utilising ‘fuzzy’ information in obtaining a better understanding of compliance issues.
EU projects which include the collection of information and views directly from fishermen, may provide guidance.
7.2.7 The evaluation of outcomes
Scientists and managers need to know how well stocks are progressing towards the recovery target, and when they actually reach the target. Providing such information to stakeholders also has potential benefits in the hope of ensuring their compliance and their sense of ownership of the process, irrespective of whether the stock trend is positive or negative.
In the short-term, ACFM will need to set terms of reference for working groups to assess if stock changes are in line with the expected stock recovery trajectories, and whether the exploitation pattern is responding to recent changes in mesh size and related technical measures such as closed areas. Comments on age diversity could be requested. The new assessments should take into account whether changes in fleet behaviour are likely to affect the tuning of the assessment, and will also need a clear evaluation of what choices to make regarding the ‘middle year’. Working groups will eventually have to judge whether stocks that have reached Bpa for two years really do qualify to be removed from the recovery plan.