José A. A. De Oliveira

Management procedures in a fishery based on highly variable stocks and with conflicting objectives: experiences in the South African pelagic fishery

The pelagic fishery in South Africa targets mainly anchovy, Engraulis capensis, and sardine, Sardinops sagax, both of which have varied substantially in abundance during the history of the fishery. Since 1988, there has been progress in this fishery towards the use of management procedures as the basis for determination of management regulations, where a management procedure is defined as a set of rules, derived by simulation and normally implemented for three to five years, specifying how the regulatory mechanism is set, the data collected for this purpose and how these data are to be analysed and used. Advantages of management procedures include formal consideration of uncertainty, the ability to choose decision rules based on their predicted medium-term consequences and a saving in workload compared with annual assessments.This paper discusses the lessons learned in application of management procedures and their precursors in this fishery. The high variability in abundance of the two stocks, the trend in their relative abundance, the substantial uncertainties in information, strong pressure to meet socio-economic goals and the conflicting objectives which arose between the directed anchovy and directed sardine fishery are identified as major problems in implementation of procedures and management of the resources. However, the use of management procedures is considered to have led to greatly improved communication with the industry and to substantial input by them into the management process. The procedures and the simulations upon which they were based also enabled consideration of the major sources of uncertainty in understanding of the resource dynamics and facilitated the development of procedures that were robust to them.It is argued that biological uncertainty greatly exacerbated the problems in application of the procedures but probably cannot be markedly reduced in the near future. Management procedures must be robust to likely variability and uncertainty. Of equal importance are identification and selection of achievable objectives, and allocation to the political decision makers and not to the scientists, of responsibility for determining acceptable trade-offs between conservation and socio-economic goals. Other issues, including the importance of long-term rights and allowance for flexibility in fishing practice, are also highlighted

Chapter 15 Operational management procedures: An introduction to the use of evaluation frameworks*

Publisher Summary A management procedure is a simulation-tested set of rules used to determine management actions, in which the data, assessment methods, and the harvest control rules for implementing management actions are prespecified. An operational management procedure (OMP) is defined as a management procedure that is currently being used to determine management actions or has been intensively tested by a competent management body to a level where it could be used in practice. An important benefit of management procedures is they can be designed to satisfy a variety of pre-agreed management objectives, including both biological and economic factors, making them more likely to be acceptable to a wide range of user groups. However, the modelling philosophy may be difficult to understand for non-experts, which means that extra effort is needed to explain them and how they are designed. This chapter describes various aspects of management procedures, including the philosophy behind them, how they are constructed based on available data and knowledge, their objectives, the methods used to evaluate them, and their differences and advantages over traditional stock assessment and management regimes. In addition, some examples of management procedures are also reviewed.

Fishing for MSY: using “pretty good yield” ranges without impairing recruitment

28 Pretty Good Yield (PGY) is a sustainable fish yield corresponding to obtaining no less than a specified large 29 percentage of the Maximum Sustainable Yield (MSY). We investigated 19 European fish stocks to test the 30 hypothesis that 95% PGY yield range is inherently precautionary with respect to impairing recruitment. An FMSY 31 range was calculated for each stock as the range of fishing mortalities (F) that lead to an average catch of at 32 least 95% of MSY in the long term simulations. Further, a precautionary reference point for each stock (FP.05) 33 was defined as the F resulting in a 5% probability of the spawning stock biomass falling below an agreed 34 biomass limit below which recruitment is impaired (Blim) in long‐term simulations. For the majority of the stocks 35 analysed, the upper bound of the FMSY range exceeded the estimated FP.05. However, larger fish species had 36 higher precautionary limits to fishing mortality, and species with larger asymptotic length were less likely to 37

Testing spatial heterogeneity with stock assessment models

This paper describes a methodology that combines meta-population theory and stock assessment models to gain insights about spatial heterogeneity of the meta-population in an operational time frame. The methodology was tested with stochastic simulations for different degrees of connectivity between sub-populations and applied to two case studies, North Sea cod (Gadus morua) and Northeast Atlantic sardine (Sardina pilchardus). Considering that the biological components of a population can be partitioned into discrete spatial units, we extended this idea into a property of additivity of sub-population abundances. If the additivity results hold true for putative sub-populations, then assessment results based on sub-populations will provide information to develop and monitor the implementation of finer scale/local management. The simulation study confirmed that when sub-populations are independent and not too heterogeneous with regards to productivity, the sum of stock assessment model estimates of sub-populations’ SSB is similar to the SSB estimates of the meta-population. It also showed that a strong diffusion process can be detected and that the stronger the connection between SSB and recruitment, the better the diffusion process will be detected. On the other hand it showed that weak to moderate diffusion processes are not easy to identify and large differences between sub-populations productivities may be confounded with weak diffusion processes. The application to North Sea cod and Atlantic sardine exemplified how much insight can be gained. In both cases the results obtained were sufficiently robust to support the regional analysis.