A Summary Of Global Stock Recovery Plans For Marine Organisms, Including Indicative Information On The Time To Recovery, And Associated Regime Changes That May Affect Recruitment And Recovery Success

No abstracts are to be cited without prior reference to the author.A desk study searched primary and grey literature, the WWW, and through personal communications, for any evidence of stock recovery plans or fisheries closures promoting recovery of depleted stocks. Rarely is complete information on stock recovery plans reported, so analysis of this provisional listing can only be indicative, but forms a useful starting point for a database on this important subject. Some 58 cases were found where a recovery effort has apparently been attempted, with 11 (46%) for demersal resources, 8 (67%) for pelagic fish stocks and 8 (67%) for invertebrates, showing some degree of success. Although it is premature to discuss success rates or time for recovery given that most recovery efforts began after 1995, where recovery times have been documented, these ranged from 3+ to 30 yr, with demersal recovery periods generally longer than for pelagics. A categorisation of resource suggests that for ‘irregular’, ‘spasmodic’ and ‘periodic’ resources, a formal recovery effort is only likely to be successful short of closure if carried out in periods of high productivity, and a main objective of management should be to ensure survival of a broad range of age classes until the next good period for recruitment. For invertebrates, ‘recovery’ may be spontaneous, and tied to declines in finfish predators. Other information relevant to recovery planning was reviewed, including empirical estimates of periods of natural low productivity from relevant time series. From published estimates of periodicities in finfish time-series and the long-term climatic data which would affect recovery time, the median duration of poor production and presumably poor recruitment, is 4-6 yr for non-depleted stocks, and 75% of periods of poor production fall within intervals of 10-11 yr or less. Other studies however suggest that periods as long as 30 yr may be dominant. A simulation assumed that a stock is now within a poor recruitment regime, and that adding 2 better-than-average ycs is one feasible criterion for recovery. The probability of good recruitment occurring, and the further duration of a poor regime, determine the duration of the recovery period. For a range of assumptions for these 2 parameters, recovery time may extend from 4-8 yr to 14-22 yr or longer. The stock-recruit relationship has been shown to differ for Canadian stocks between good and poor regimes, and the dangers of estimating recovery times by extrapolating from spawner-recruit data collected during high production regimes is illustrated.

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