Clara Ulrich

Estimation of technical interactions due to the competition for resource in a mixed-species fishery, and the typology of fleets and métiers in the English Channel

In a multi-gear and multi-species artisanal fishery, the level of technical interactions (i.e. the competitive externalities resulting from a shared exploitation of common resources or fishing grounds) among various fishing units is high. Assessing these technical interactions is of great importance for fishery management, as any control applied to one fishing unit may have positive or negative effects on others. The magnitude and direction of these effects cannot be easily measured, unless all fishing units and species in the fishery are considered simultaneously. Technical interactions are particularly important in the complex artisanal fisheries of the English Channel. Using a bioeconomic model of the English Channel that incorporates all the major fishing units (the BECHAMEL model), we describe a method for measuring and classifying the technical interactions due to the competition for resource (stock externalities). The results are used to develop a typology of metiers and fleets based on their overall level of interaction for the resource. We also define fleets and metiers as structuring, dependent, intermediate or autonomous.

A multi-species multi-fleet bioeconomic simulation model for the English Channel artisanal fisheries

Considering the large number of technical interactions between various fishing activities, the English Channel (ICES divisions VIId and VIIe) fisheries may be regarded as one large and diverse multi-country, multi-gear and multi-species artisanal fishery, although rarely studied as such. Awhole-scale bioeconomic model has been constructed. It does not take into account biological interactions, but focuses on competition among fleets. A large amount of biological and economic data have been preliminarily gathered, leading to a substantial increase of the quantitative knowledge available. The main purpose of the model is to study the long-term consequences of various management alternatives on the economic situation of the English and French fleets fishing in the area and on exploited resources. The model describes this feature through the links between three entities on the one hand (stocks, fleets and ‘‘me«tiers’’, i.e. gear targetspecies fishing area), and three modules on the other hand (activity, biological production and economics). The model is described and some simulation results are presented. An example simulating a decrease of one fleet segment effort illustrates these technical interactions among fleets and underlines the interest of a large-scale approach for these fisheries. # 2002 Elsevier Science B.V. All rights reserved.

Achieving maximum sustainable yield in mixed fisheries: a management approach for the North Sea demersal fisheries

Achieving single species maximum sustainable yield (MSY) in complex and dynamic fisheries targeting multiple species (mixed fisheries) is challenging because achieving the objective for one species may mean missing the objective for another. The North Sea mixed fisheries are a representative example of an issue that is generic across most demersal fisheries worldwide, with the diversity of species and fisheries inducing numerous biological and technical interactions. Building on a rich knowledge base for the understanding and quantification of these interactions, new approaches have emerged. Recent paths towards operationalizing MSY at the regional scale have suggested the expansion of the concept into a desirable area of “pretty good yield”, implemented through a range around FMSY that would allow for more flexibility in management targets. This article investigates the potential of FMSY ranges to combine long-term single-stock targets with flexible, short-term, mixed-fisheries management requirements applied to the main North Sea demersal stocks. It is shown that sustained fishing at the upper bound of the range may lead to unacceptable risks when technical interactions occur. An objective method is suggested that provides an optimal set of fishing mortality within the range, minimizing the risk of total allowable catch mismatches among stocks captured within mixed fisheries, and addressing explicitly the trade-offs between the most and least productive stocks.

Sensitivity of some biological reference points to shifts in exploitation patterns and inputs uncertainty for three North Sea demersal stocks

Abstract This study examines the sensitivity of six biological reference points (BRPs), both to variability and uncertainty of their input parameters, and to shifts in exploitation patterns. These shifts arise from accounting for the trends in catchability in extended survivors analysis (XSA) tuning fleets derived from the “hybrid method”. By using non-parametric resampling and Monte Carlo stochastic procedures, we test whether such shifts in exploitation patterns significantly affect reference point values and probability distributions, for various levels of variation of input parameters. This method is applied to North Sea plaice, sole and cod stocks. We show that accounting for catchability trend generally induces only slight changes in reference point mean values. In particular, it is mostly significant over the last decade, especially for plaice, but not when introducing medium levels of uncertainty for the natural mortality.

Rights-Based Management and Participatory Governance in Southwest Nova Scotia

In the late 1980s the ground fish fishery in Atlantic Canada suffered a massive collapse. This collapse and some institutional factors, including a massive cut in the budget of the Department of Fisheries and Oceans, led to a number of management innovations. The chapter focuses on the substantial expansion of both rights-based management and participatory governance and the ways these two changes interacted with one another. The most common form of rights-based management in Nova Scotia is ITQs. However, the smaller boats fishing with fixed gears are using community quotas instead. One community from this group, the one with the largest fishery, has developed an internal ITQ system to allocate its community quota and this approach has proven successful at mitigating some of the social costs of ITQs while retaining most of the economic benefits. Participatory governance in Nova Scotia also extends to some extent to the way scientific advice is developed and used. Overall, this process has improved social robustness, by reducing the feeling of industry of being ignored. It has also improved biological robustness, by increasing the feeling of ownership and responsibility for the resource and improving the commitment to scientific advice.

Reducing discards without reducing profit: free gear choice in a Danish result-based management trial

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Evaluating Biological Robustness of Innovative Management Alternatives

The influence of innovative management alternatives (participatory governance, effort management, decision rules) on biological robustness (BR) in various fisheries relevant to the EU (Baltic, Western Shelf, Faroe Islands, North Sea), was investigated with a numerical simulation model developed in the EU projects EFIMAS (2004–2008) and COMMIT (2004–2007). The index for BR was set as the percentage of years in which standard biological reference points (Bpa, Fpa) were met. The results suggest that new information obtained through participatory governance may affect BR by reducing bias rather than increasing precision, implying that participatory governance should rather focus on potential sources of bias than on (perceived) low sampling efforts. Further analyses suggest that effort-based regimes combined with catch quota restrictions improve BR. However, the relative effect of catch quotas versus effort management on BR varies with circumstances, implying that careful and case-specific analyses are needed to weigh one against the other. This requires more detailed data than generally available at present, including electronic surveillance, detailed catch data, environmental/productivity data, recruitment and misreporting. Finally we analysed a decision rule consisting of a two-step management system, which allows TAC adjustment according to the state of the stock monitored during the fisheries season. Such measures may improve the BR.

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.