Elsevier

Fisheries Research

Volumes 134–136, December 2012, Pages 6-16
Fisheries Research

Managing mixed fisheries in the European Western Waters: Application of Fcube methodology

https://doi.org/10.1016/j.fishres.2012.07.019Get rights and content

Abstract

Fisheries management is moving towards ecosystem based management instead of traditional single species based advice. To progress towards an ecosystem approach, a new methodology called “Fleet and Fisheries Forecast” (Fcube) has been proposed. In the application of the method, a precise initial fleet and metier segmentation used is important to get representative results in the analysis. Once they were defined, different data aggregations for fleets and metiers were tested with the objective of getting the best aggregation level to get equilibrium between detailed results and real management. Results showed that the difference in the forecast catches in different aggregation levels was low. Finally, hindcasting analyses were carried out to evaluate how sensitive forecasts are to different parameters. Stock indicators and catchability show the highest source of error and the effort share the lowest. In this analysis, Western Waters fleet management results show consistency between stocks and their respective TACs. The study highlights that it is possible to deliver advice within the context of mixed fisheries using the Fcube method.

Introduction

Most European demersal fisheries are mixed fisheries, meaning that more than one species are caught simultaneously by fishing gears. When managing mixed fisheries, conflicts between ecological and economic objectives arise (Greenstreet and Hall, 1996, Jennings et al., 1999, Pope et al., 2000). The problems these conflicts cause arise due to the different stock status, conservation needs and their value.

The currently used Total Allowable Catch (TAC) management system in European waters is based on single-stock status assessments. But it has failed to support a sustainable exploitation of some demersal species and no sign of recovery for some stocks already depleted (Khalilian et al., 2010). Mixed fisheries are characterised by high levels of discarding (Pastoors et al., 2000, Cotter et al., 2002) mainly caused by the continuation of fishing when the quota for one or more species is exhausted. The implications for single-species quota allocations may lead to an increase in discarding at the end of the year.

In an attempt to solve these problems, the 2002 reform of the European Common Fisheries Policy moved from TAC control to TAC and effort control in a mixed-fisheries approach. In TAC and effort control, TAC manages the output, the quantity of fish that is extracted from the sea, meanwhile effort control is managing the input, the level of harvesting capacity. In recent years, ICES has consistently indicated that setting a TAC is not enough to limit fishing mortality on many stocks and has recommended that effort management be applied in those cases (CEC, 2002, Penas, 2007). In 2009, a Green Paper from the European Commission was published (EC, 2009) for the Reform of the Common Fisheries Policy. The reform tries to go a step ahead towards an ecosystem based approach to fisheries management, by including a regional approach for management. However, the main concern still remains on how to integrate these changes, at all stages, starting from stock assessment and scientific advice towards sustainable fishery management.

Here is a method to manage mixed fisheries, given that the Total Allowable Catch (TAC) management system in Europe is currently based on single-stock status assessments. However, other researches show that, alternatives to the currently Total Allowable Catch (TAC) management system exist. There are limited methods were well-defined targets for the management of mixed fisheries are set. Two of these limited methods are described by Gröger et al. (2007) and Da Rocha et al. (2012). Both use maximization methods to define multitarget objectives for mixed-fishery management. Gröger et al. determine targets for five stocks assessed and managed by the National Marine Fisheries Service (NMFS). Da Rocha et al. (2012) define targets for the European northern hake stock (Merluccius merluccius), where fleets also capture northern megrim (Lepidorhombus whiffiagonis) and northern anglerfish (Lophius piscatorius and Lophius budegassa).

In the short term, management measures to be applied on mixed-species multi-fleet management must consider fleet- or fishery-based advice rather than just stock-based advice (STECF, 2003, Vinther et al., 2004, Gascuel et al., 2012). These approaches should attempt to reconcile conflicting management advice for different species within the same fishery, and to generate catch/effort advice that accounts for the mixed-species nature of the fishery in a multi-fleet structure.

A fleet and fisheries approach has been implemented recently for providing mixed-fisheries advice in Europe, the “Fleet and Fisheries Forecast” method known as Fcube (Ulrich et al., 2008, Ulrich et al., 2009, ICES, 2006, ICES, 2009a, ICES, 2009b, Hoff et al., 2010). This method was initially developed within the multifleet, multi-species simulation framework TEMAS (fleet-based bio-economic simulation software to evaluate management strategies accounting for fleet behaviour) (Ulrich et al., 2007). Fcube was selected within an ICES workshop (ICES, 2006) as the most suitable candidate approach as replacement of the MTAC (Mixed species TAC evaluation) method (Vinther et al., 2004). MTAC represented an initial attempt to use fleet catch information to give TAC advice for mixed fisheries. However this was unsuccessful for a number of reasons, the main was that catch data used to parameterise the model made no distinction between the fleets and their activity (Ulrich et al., 2008).

In this study the definitions of fleets and metiers used are consistent with the Data Collection Framework of European Commission (EC, 2008) and they have been used in some analysis concerning mixed-fisheries (Marchal, 2008). A fleet segment is defined as “a group of vessels with the same length class (LOA) and predominant fishing gear during the year. Vessels may have different fishing activities during the reference period, but might be classified in only one fleet segment”. A metier is “a group of fishing operations targeting a similar (assemblage of) species, using similar gear, during the same period of the year and/or within the same area and which are characterised by a similar exploitation pattern”. So, in the same fleet segment different metiers could be identified.

The conceptual basis of the Fcube approach is that a fleet can exploit a number of different metiers during the year, hence the partial fishing mortality it exerts on a given species can be estimated from the amount of effort allocated to a given metier multiplied by the catchability of that species in that metier to that fleet, summed across all metiers exploited during the year (Ulrich et al., 2009, ICES, 2009a, ICES, 2009b).

Finally, as in any model, the results are subjected to uncertainties due to parameters estimates and particularly the inability to predict future values of annually variable parameters (Charles, 1998). The impact of assumptions made for their estimation should thus be evaluated.

Using example of mixed fisheries in Western EU waters, the aim of this article is to evaluate the utility of Fcube for predicting how the effort should be allocated in managing mixed fisheries, and how sensitive these predictions and any resulting advice might be to assumptions regarding how fleets are specified and information on stocks and catchability.

Section snippets

Fcube method and strategies

The Fcube method is described in detail in Ulrich et al., 2008, Ulrich et al., 2009 and ICES, 2006, ICES, 2009a, ICES, 2009b, and the main features are summarised below.

Fcube method forecasts the effort level by fleet corresponding to each single stock TAC, i.e. the effort that fleets use to catch their quota share of each stock. It relies on two assumptions, firstly fishing mortality within a metier is proportional to effort and catchability by stock within the metiers and their effort share

Base Case Scenario

In Fig. 2 total international catch forecast for 2007 for each stock under each strategy is shown. Under a certain stock strategy, the total catch of the stock driving the strategy corresponded exactly with its TAC for all the stocks except for megrim. Megrim was the only stock analysed in which discards were included in the assessment. Within the Fcube, as the assumption is that the discarding rate will be equal to the observed average discarding rate, the total forecast catch did not

Discussion

Delivering advice within the context of mixed fisheries appears to be possible using the Fcube method. It is about to be the case for the North Sea. ICES WKMIXFISH (ICES, 2009a) and later ICES AGMIXNS (ICES, 2009b) are the accepted form for mixed-fisheries advice which will be included as part of the advice from 2010 onwards. Although management currently used is based on individual stock assessment, these assessments can in turn be integrated within Fcube application and can help towards

Acknowledgements

This work has been funded through the Basque Country Autonomous Government (Department of the Environment, Land Use Planning, Agriculture and Fisheries) and the FP6EU funded project AFRAME (A Framework for Area and fleet Management, contract no. 44168).

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