We recently completed an assessment of an overfished U.S. stock under a rebuilding plan. The rebuilding plan is intended to achieve the spawning potential at 30% of the unfished potential (i.e. SPR30%) in 2017. Our (2015) analysis suggested that the stock could not rebuild to that target, even at fishing mortality = 0. Management council staff argued that under this condition, U.S. National Standard Guidelines (NS1) allow an annual catch limit (ACL) computed using an equilibrium projection at 75% of FSPR30 (the proxy for F at optimal yield). This would delay the rebuilding of the stock for about 60 years, and permit fishing mortality levels that have recently resulted in ongoing depletion. Does anyone else have examples like this? How do other regulatory councils manage under this scenario?
continue to keep fishing mortality at zero, and change the U.S. national standard guidelines (NS1) rules.
I agree! I'm checking to see if this Council's interpretation of NS1 (when a rebuilding plan has expired or cannot be met) is consistent with the intent of the guidelines. Perhaps it is not.
If a plan fails to meet a target it can be because either the targets were not appropriate, the strategy was not sound or unforeseen factors played a role. Assuming nothing out of the ordinary happened and from your description of the situation, the target was unrealistic from the beginning. My approach would be to present the managers alternative scenarios where different F levels are applied and compute the probability that the stock would be at a new target or a set of targets. Targets are defined in terms of stock status goal and time to reach the status goal. The management can then discard unacceptable scenarios and focus on those that can be realistically (from the manager perspective) applied and the science can respond to questions that make use of risk levels not to meet the goals. In the end, it is up to the manager to decide how much risk they are willing to accept under viable scenarios, and their choice may not be our most desirable alternative, but it is what would be enforced, so better know how thick the ice is.
Good plan. We are doing something like that, just waiting for some input from our management council.
We have found that a previously overexploited linefish species, on which a moratorium was placed (F=0) in 1997 appears to have made negligible recovery. We suspect that another species has filled the niche space left behind and is potentially making it difficult for the protected species to bounce back. I mention this because, in our situation it seems that intra-species dynamics are not the only factors making it difficult for the protected species to bounce back. Any amount of fishing effort on this particular stock, which is so degraded, would place undue extra pressure.
An additional factor to consider is whether there is any un-targeted mortality - are the fish caught as by-catch in a permitted fishery for example? On the west coast of Scotland we have failed to see much recovery of cod despite restrictive TACs, cod recovery plans etc. Many potential reasons for the failure to rebuild have been suggested with the latest being an increase in predation by grey seals. The problem with all this is that eventually the industry argues that if it aint coming back why should they be subject to restrictions - unless one can really answer the question of why rebuilding is not occuring it is quite difficult to respond to this point.
Thanks for all the great responses. We agree that environmental effects and predation could both be at play.
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