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Case study 4: Nephrops Fisheries in the East Atlantic

Introduction - Overview description of the case study

Description of the fishery, stocks and management system

Fishery and stocks

Current total Nephrops landings from the ICES area are around 50 000 t per year, with the largest quantities being taken from sub-areas IIIa, IV, VIa, VII and VIII. Nephrops has a very high market value, the result being that the Nephrops fisheries figure amongst the economically most important sea fisheries in northern and western Europe.

Because of its burrowing behaviour, Nephrops is bound to particular types of sediment, consisting of a mixture of sand and mud. As a consequence, the geographical distribution of Nephrops is very discontinuous, with the highest densities being found in areas of “suitable” sediment and very low or zero densities in between. In 1984, the ICES Working Group on Nephrops Stocks identified so-called Functional Units for Nephrops, which are regarded as geographically isolated biological entities. Since then, these Functional Units have systematically been used as operational units for data collecting, assessment and advisory purposes.

Fishing for Nephrops is mostly done with bottom trawls. In some areas, there are also creel fisheries for Nephrops. Fishing strategies, gear types, mesh sizes and minimum landing sizes differ between areas and Functional Units. Some fisheries are primarily targeting Nephrops, while others are truly mixed fisheries, where Nephrops is one of the target species together with a variety of roundfish, flatfish and/or other Crustacean species.

Owing to the morphology of Nephrops, the size selection of Nephrops trawls is usually poor and this results in high levels of discarding. Mixed fisheries interactions and by-catches of gadoids (mostly cod, haddock and whiting) and hake are often considerable too, the consequence being that there is a major mixed fisheries and “by-catch problem” in many Nephrops fisheries (in terms of both by-landings of fish of commercial sizes, and discarding of undersized or otherwise unwanted fish). Again however, there are marked differences between areas and Functional Units, with cod and haddock being the prime species of concern in the most northern areas, cod and whiting in the intermediate areas, and hake in the most southern areas.

Main assessment and management problems

Assessment problems

There are several problems special problems connected with assessment of Nephrops stocks:

  • Nephrops cannot be aged.
  • It lives in burrows in the sea bed with variable emergence patterns.
  • The behaviour of the two sexes differs, resulting in different exploitation rates.

The methods employed to assess the state of Nephrops stocks and their exploitation include:

  • The analysis of long-term trends in fishery data, e.g. LPUE.
  • Length cohort analysis (LCA), both for each sex separately and for the two sexes combined.

* Yield-per-recruit analyses based on the output of LCAs.

* Age-based VPAs/XSAs, based on “pseudo age groups”. These are obtained by “knife-edge” slicing (based on growth curves) of the length compositions of the removals.

* Abundance estimates based on fishery independent surveys (e.g. TV-monitoring surveys).

The technique used to generate the “pseudo age groups” (viz. knife-edged slicing of the length distributions of the removals) however, is questionable. The method is particularly sensitive to the input parameters for growth and may therefore produce age groups that do not fully reflect the true age composition of the stock. Moreover, a major problem here is that the increase in variability in size of the older individuals may lead to several true ages being included in a single sliced “pseudo age group”. Such biases may have a major impact on the outcome of the assessments and hence on the appreciation of the state of exploitation. ICES also (2005) rejected this ageing method for input to assessments using age based cohort analyses. Another source of concern in the assessments is the lasting uncertainty over the estimates of the natural mortality rates (M) for Nephrops.

In an attempt to overcome these problems, fishery independent surveys (such as underwater TV and trawl surveys) have been introduced as an assessment tool for a number of Nephrops stocks. In recent years the UWTV surveys have proven to be very useful in providing abundance estimates, either as indices or absolute estimates of several Nephrops stocks. Although the uncertainties connected with the estimates of absolute abundance by this method may be high, they are believed to reliable enough as bases for usable estimates of current harvest rates (H.R). Although this survey method is expensive and resource demanding, it has now been used for several years for an increasing number of ICES stocks. Other outstanding problems with Nephrops assessments are the lack of reliable recruitment data and the absence of reliable biological reference points (BRPs) that can help in the evaluation and decision making process.

Despite the improvements of the assessment of the state of the Nephrops stocks in recent years following the introduction of fishery independent surveys, i.e. UWTV survey technique,there is still need for improvement in the methodology of the Nephrops assessments. The development of new tools for the biological assessment of Nephrops stocks is beyond the scope of this project, but it is the project partners' intention to closely follow up any new developments in the field and to take these into account in the evaluation process.

Management problems

• Problems related to the current TAC system

At present, the Nephrops fisheries in the ICES area are managed through a system of annual or biennial single-species TACs which are set for large management areas defined by ICES boundaries (IIIa, IV, VI, VII, etc.)and boundaies betwen EU and Norway. Both the ICES Working Group on Nephrops Stocks and ACFM have repeatedly pointed out that TACs based on these large areas are not satisfactory. They do not allow for a type of management which takes account of the different levels of exploitation in different Functional Units, which are assessed separately and for which ICES provides management advice separately.

• Problems related to the mixed fisheries interactions and by-catch of gadoids and hake

Mixed fisheries interactions and by-catches of gadoids and hake in the Nephrops fisheries are often considerable. So far, however, this issue has never been properly addressed, neither by the Working Group on Nephrops Stocks, nor by any of the demersal fish Working Groups of ICES. Except for the Nephrops stocks in the southern seas (Bay of Biscay, Iberian Peninsula), there is very little evidence of over-exploitation in Nephrops stocks and hence at present little need to reduce fishing effort on the Nephrops stocks. However, since most Nephrops fisheries, except the creel fisheries, can be considered as mixed fisheries, there is, however, increasing pressure to perform mixed fisheries management strategy evalution, to reduce the overall effort, and / or to improve species selectivity of the Nephrops gears, in an attempt to reduce fishing pressure on the by-catch species.

A further management problem of the Nephrops fisheries in the NE Atlantic is that the Nephrops trawlers may switch activity from Nephrops to other target species (usually gadoids) depending on the relative economic benefits of each activity.

Description of the base case and scenario evaluations

Due to changed coordination of Case Study 4 the Terms of Reference and deliverables of WP4 Case Study 4 are revised as follows:

The two key fisheries management topics to be addressed are:

A. Determination of the sensitivity of the current length based Nephrops stock assessment tools to varying parameter inputs.

B. Determination of the biological and bio-economic impacts of the mixed Nephrops fisheries interactions in relation to management strategy evaluation as well as the biological impact of existing levels of discarding of commercial fish species in selected European Nephrops fisheries. In relation to the latter make evaluation of the potential benefits that might arise from a change in species selectivity of the fishing gears currently used in those fisheries.

Therefore, the revised work plan is split into two components (Topics A and B). Topic A focus on Nephrops stock assessment methods which make use of length-structured data. A study to determine the sensitivity of such models to input data and parameters will be undertaken, with particular focus on the sensitivity to sampling levels and estimates of growth parameters. This will allow for an understanding of what factors most influence such length based stock assessment models and where the key uncertainty lies. This information can then be used to subsequently direct workers as to what the key data is required to most effectively reduce the uncertainty in the model for the future.

Topic B forms an evaluation of the mixed Nephrops fisheries interactions and by-catch and discarding problems.

This part focus on the biological and bio-economic impacts of the mixed Nephrops fisheries interactions in relation to mixed fisheries management strategy evaluation as well as on the biological impact of existing levels of discarding of commercial by-catch species in selected European Nephrops fisheries.

This part forms also an essential planned linkage between the parallel EC Framework 6 gear technology project (NECESSITY). Without this linkage, or indeed this case study, a key component of the NECESSITY project could not be completed. This case study (CS4b) will make estimations of the biological consequences which can be potentially accrued through the use of new gear based technical measures. These new gear technical measures are being developed under the framework of the NECESSITY project, and are intended to reduce discarding of juvenile whitefish in Nephrops fisheries around EU waters. The linkage between the gear development work undertaken in the NECESSITY project and the assessment of the biological impacts through the EFIMAS provides a useful set of deliverables which compliments both EC funded projects.

Concerning the evaluation of different management strategies in relation to the mixed fisheries interactions for the mixed Nephrops and gadoid fisheries (including potential discarding in relation to this) there are strong intra-project linkages to EFIMAS Case Study 2 (North Sea roundfish fisheries) especially in relation to use of the North Sea Roundfish mixed fisheries OM under Case Study 4 enabling bio-economic management strategy evaluation of the interactions in the mixed North Sea roundfish and Nephrops fisheries. Also, there is a similar strong linkage in relation to the development of a common OM between Case Study 4 and the Approach 2 under Case Study 6 (Mixed Northern hake and Nephrops fisheries) which has been applied and implemented in the Nephrops and Northern Hake Mixed Fisheries in the Bay of Biscay and Celtic Sea considering mixed fisheries aspects.

Description of approaches for scenario evaluations

Revised work programme for EFIMAS Case Study 4:

The two key fisheries management topics to be addressed in this EFIMAS Case Study 4 will be as follows:

Topic 4A) Determination of the sensitivity of the current Nephrops stock assessment tools to varying parameter inputs

Work plan for topic 4A (Sensitivity analysis of length based Nephrops assessment tools to varying input parameters): Work started March 2006 and completed March 2008.

Methodology to be used:

Review of old Nephrops WG reports for past similar work

Establishment of a simulation model: a sex-disaggregated seasonal operating model for Nephrops Approach 1 FLR operating model

Assess the effects of varying input parameters

Approach 1: A length-based assessment (LBA) method of the size-transition matrix type has been written in AD Model Builder. Input parameters, assessment data and settings and initial parameter values are all stored in a single input file. It was hoped that an 'FLR' LBA package could be created as part of this case study. However, this has proved beyond the scope of this project and would require some substantial re-writing of the LBA ADMB code due to the large amount of input data and parameters required by LBA. The method operated by creating a temporary input file from the FLStock and survey index objects at each iteration, running the assessment which writes results to temporary files and then reading in the results to appropriate FLR objects. Although this is a rather cumbersome approach, the sets of simulations (250 for each scenario) generally take less than a couple of hours to run.

As the operating model is age-based and makes a conversion to length structured data using a different implementation of growth to the length-based assessment model, the first check was to ascertain how well the assessment model performed given an unbiased absolute abundance index. Model performance was judged on the ability to estimate the current stock status in terms of biomass and fishing mortality and in addition, comparisons were made over the whole time series. Fishing mortality was estimated as the average over ages 3 to 7, which was compared to the average over equivalent lengths (calculated using growth parameters) output from the assessment model. For comparison, the assessment model was also run with the TV survey indices derived with a variety of alternative assumptions (true mean weight, mean weight in catch, actual survey-derived mean weight) about mean individual weight.

Following the initial model runs, other simulations were carried out to investigate the sensitivity to:

• alternative assumptions about changes in burrow detection with individual length

• number of length classes assumed in the assessment model

• missing information on total catch data (due to lack of reliable information on catch due to misreporting for example)

Deliverables: Final report detailing the sensitivity analysis undertaken and the effects and implications of varying model input parameters.

Approach 1, Testing of length-based Nephrops assessment methods using a sexually dimporhic operating model and growth model

Topic 4B) Management strategy evaluation of mixed fisheries interactions and determination of the biological impacts of existing levels of discarding of commercial fish species in selected European Nephrops fisheries, and the potential benefits that might arise from a change in species selectivity of the fishing gears currently used in those fisheries

Concerning the evaluation of the mixed fisheries interactions and potential discarding in relation to this there are strong intra-project linkages to EFIMAS Case Study 2 (North Sea roundfish fisheries) especially in relation to use of the North Sea Roundfish mixed fisheries OM under Case Study 4 enabling bio-economic management strategy evaluation of the interactions in the mixed North Sea roundfish and Nephrops fisheries. Also, there is a similar strong linkage in relation to the development of a common OM between Case Study 4 and the Approach 2 under Case Study 6 (Mixed Northern hake and Nephrops fisheries) which has been applied and implemented in the Nephrops and Northern Hake Mixed Fisheries in the Bay of Biscay and in Celtic Sea considering mixed fisheries aspects.

This work has direct linkage to the allied EU FP6 project NECESSITY as well as the development of simulation tools under the fisheries management evaluation framework in Case Study 2 and Case Study 6.

Work plan for topic 4b: The biological impacts of discarding in selected EU Nephrops fisheries and the consequences of changes to the species selectivity of the fishing gears used in those fisheries

Methodology to be used (main methods):

Method 1.

Stock assessments has been run on affected whitefish stocks, with and without discards to determine effects of discarding. The process is repeated with modified discard data that comes from the using the modified fishing gears.

The FLR framework was used to evaluate the effect of alternative nephrops gears on the commercially exploited gadoid stocks and fisheries (i.e. cod, haddock and whiting). Within commercial fisheries, particularly mixed fisheries, both target and non-target species are often discarded. Discarding represents a potentially significant loss to the productivity of fish stocks; it can have damaging ecological consequences, and is a potential cause of the failure of recovery plans. The Nephrops fishery in the North Sea is classified as a mixed fishery. Nephrops trawls are constructed with smaller meshes than trawls used to target whitefish; consequently, the bycatch of juvenile fish can be substantial. Several new Nephrops trawl designs have been tested in the North Sea. The data from these trials are used to investigate the potential impact of their implementation on cod, haddock and whiting stocks in the North Sea (including the Kattegat and Skagerrak).

Approach 2, Evaluation of sensitivity of the current Nephrops stock assessment tools to varying parameter inputs

Method 2.

Concerning this method a simulation tool in R (in relation to FLR), i.e. the FLR-ISIS (ISIS-FISH in R) has been developed. This comprehensive simulation tool (also mentioned under EFIMAS WP3) has been applied and implemented in the Nephrops and Northern Hake Mixed Fisheries in the Bay of Biscay and Celtic Sea considering mixed fisheries aspects and scenarios. Simulations have been performed, and the results from the simulations and model developments have been reported and is presented in a paper submitted to ELSEVIER (see link to paper below and under WP4 Case Study 6 Approach 2).

Approach 3, Evaluating Hake and Nephrops Fisheries Mixed fisheries interactions using the bio-econimic FLR-ISIS Model

Method 3.

DIFRES has focussed on the linkage between CS4 and CS2 and develop the synergistic components from both of these case studies. This approach focuses mostly on the fleet-based effects of stock-based management procedures (TAC and EFFORT) in a mixed-fisheries context. The main issue dealt with here is how to account for technical interactions and fishermen behaviour in the Management Strategies Evaluation. Within that purpose there was developed a method called F-CUBE which was tested in cooperation with the ICES MIXMAN Study Group 2007-2008 (link below). Two major works have been developed in parallel. A complex full feed-back and stochastic MSE including some major sources of uncertainty has been developed, including cod-haddock interactions only. Furthermore, a specific approach has been developed for investigating the consistency of the various single-species management objectives in the short-term, taking into account simple hypotheses about fleet behaviour.

Approach 4, Evaluating Mixed Fisheries and Discard Scenarios in the North Sea Mixed Roundfish and Nephrops Fisheries using the OM developed under:

Approach 4 similar to Case Study 2 Approach 1

Summary of Results (summary of scenario evaluations)

Results: Topic 4a) A determination of the sensitivity of the current Nephrops stock assessment tools to varying parameter inputs

Approach 1

The first two sets of runs considered in this study (‘Base case’ and ‘Alternative burrow detectability’) show that in order to for this assessment model to give unbiased estimates of stock status (biomass, fishing mortality and recruitment), the survey based biomass index must be unbiased. The work here highlights two issues of importance: i) the detectability of burrows (and whether this is length dependent), and ii) how to Assessing immediate and long -term effects on landings and spawning stock biomass in Norway lobster (Nephrops norvegicus) from the Southwest and South of Portugal by changing trawl codend mesh size, mesh configuration and introducing sorting grids .translate the number of burrows into a biomass estimate (Figures 1 and 2). The process of translating numbers into biomass could be avoided by using an assessment method which could use a ‘total numbers’ index as additional information rather than biomass. However, how well this would work in practice has not been tested within this study. This leaves the issue of size-dependent detectability which is clearly a problem that should be addressed by additional fieldwork.



Figure 1. Performance of stock assessment model in assessing the current status of the stock (and tracking previous dynamics): biomass, fishing mortality & recruitment, comparing 3 methods of translating survey numbers to biomass and assuming burrow detectibility of 1 across all individual length classes.



Figure 2. Performance of stock assessment model in assessing the current status of the stock (and tracking previous dynamics): biomass, fishing mortality & recruitment, comparing 3 methods of translating survey numbers to biomass and assuming burrow detectibility as a step function at 20 mm.

These sets of results also show that even when an unbiased biomass index is used, there is still a slight bias (< 5 %) in estimated stock biomass and fishing mortality. These biases may result from a number of reasons including: the use of different growth models in the operating model and assessment model, the inability of the assessment model to be able to reproduce the typically very noisy catch-at-length distribution data and the conversion of lengths to ages when comparing estimated and observed fishing mortalities.

Figure 3. Performance of stock assessment model in assessing the current status of the stock (final year values): biomass, fishing mortality & recruitment, with truncated total catch time-series. Model runs assume burrow detectability of 1 across all length classes and labelling relates to number of total years catch data included in the assessment (full time series is 22 years).

A more interesting outcome of the simulations conducted here is that stock status can be reasonably well estimated (given an unbiased biomass index) even when significant amounts of total catch data are missing e.g. the most recent 7 years in the example shown (Figure 3). During the late 1990s and early 2000s, a substantial amount of mis-reporting of Nephrops landings is believed to have occurred in northern Europe. However, given accurate survey abundance indices and catch-at-length frequency information, it may be possible to carry out analytic assessments for some of these stocks. Since the introduction of buyers and sellers legislation at the end of 2005, landings data are thought to be more accurate and therefore assessments could be carried out with a period of missing total catch data in the middle of the time series. However, such scenarios need to be further simulation tested beforehand as uncertainty in estimated fishing mortality may still be high.

Further results and illustrations can be found in the report on this part of the case study.

Results: Topic 4b: The biological impacts of discarding in selected EU Nephrops fisheries and the consequences of changes to the species selectivity of the fishing gears used in those fisheries

Approach 2

Stock assessments have been run on affected whitefish stocks, with and without discards to determine effects of discarding. The process is repeated with modified discard data that comes from the using the modified fishing gears.

==== North Sea ====

Within commercial fisheries, particularly mixed fisheries, both target and non-target species are often discarded. Discarding represents a potentially significant loss to the productivity of fish stocks; it can have damaging ecological consequences, and is a potential cause of the failure of recovery plans. The Nephrops fishery in the North Sea is classified as a mixed fishery. Nephrops trawls are constructed with smaller meshes than trawls used to target whitefish; consequently, the bycatch of juvenile fish can be substantial. Several new Nephrops trawl designs have been tested in the North Sea. The data from these trials are used to investigate the potential impact of their implementation on cod, haddock and whiting stocks in the North Sea (including the Kattegat and Skagerrak).

The model developed examines five trawl designs, and also the scenarios of a cessation of discarding in all North Sea fisheries and in just the Nephrops fishery. The model is deterministic, and evaluates the relative differences between scenarios assuming all other variables remain constant. If discarding of cod, haddock and whiting in the North Sea fisheries were eliminated, stocks would increase by 41%, 14% and 29% respectively within 10 years. Eliminating discarding in the Nephrops fishery alone would increase stocks by 2%, 1% and 13% respectively, reflecting the relative proportion of catches of these species in the Nephrops fishery. For cod and haddock, the introduction of the Nephrops trawl with a grid with a square-mesh codend was the only scenario in which a notable increase in stock number was observed. This trawl design facilitates the escape of fish of all ages/sizes from the trawl, effectively making the Nephrops fishery a single-species fishery. For whiting, stock numbers and landings increased under all scenarios, but forecasted landings were lower than if current discard patterns continued in all except the no-discards scenario. The dependency of the results on the validity of the assumptions and on the accuracy of the input data is discussed. Full details of this work has been peer-reviewed and is published in Fisheries Research (Catchpole et al, 2007). Catchpole et al 2007

==== Irish Sea ====

An Irish case study has been undertaken which modelled the potential effects upons stocks of whitefish which could result from the introduction of the coverless (cutaway) trawl in selected Irish Nephrops fisheries. Full details on this work is contained in the pdf attachment . EFIMAS Irish Sea Nephrops Report

==== Portuguese Coast ====

A case study has been undertaken pertaining to the nephrops fisheries located off the Portuguese coast. In this model the Portuguese workers successfully identified the immediate and long term effects on landings and spawning stock biomass of nephrops Norwegicus from the southwest and south of Portugal as a result of changing trawl cod end mesh size, configuration and introducing a sorting grid. Full details on this work are detailed in the pdf attachment (document and powerpoint presentation). EFIMAS-NECESSITY Changes in Gear Selectivity_Nephrops_Portugal
EFIMAS_Nephrops case study_Portugese Report

== Bay of Biscay ==

A case study has been undertaken by french Colleagues who examined the effect upon stocks of Nephrops norwegicus in the bay of Biscay in relation to various fishing gear changes. full details are contained in the attached pdf document. EFIMAS_Nephrops_case_study_Bay of Biscay_France

Approach 3

IFREMER has focussed on evaluating Hake stocks and Nephrops fisheries interactions in local waters by further developing the existing French model. A main issue in the dynamics of mixed fisheries is that of technical interactions, leading to incidental catch and discarding. Technical interactions largely depend on the allocation of fishing effort between métiers and fishing grounds which in turn is tightly linked to economic conditions and to the expected profitability of alternative options for fishing effort allocation. We developed a bioeconomic fishery model to investigate these issues, and in particular to explore the possibilities of mitigating these interactions through appropriate policy options. The bioeconomic model was developed using and creating FLR (http://www.flr-project.org) packages as part of the EFIMAS project http://europa.eu.int/comm/research/fp6/ssp/efimas_en.htm). The model is spatially- and seasonally- explicit, it considers population dynamics, exploitation dynamics and policies are explicitly modelled, building in the fishery model underlying the ISIS-Fish software (http://www.ifremer.fr/isis-fish\). The model is applied to the hake-nephrops fishery in the Bay of Biscay. The fishery generates a large amount of by-catch of juvenile hake, particularly at recruitment time. We modelled the dynamics of the main fleets exploiting hake and nephrops, and investigated the consequences of alternative policy options, including Marine Protected Areas, closed seasons, and selective devices.

Approach 3, Evaluating Hake and Nephrops Fisheries Mixed fisheries interactions using the bio-econimic FLR-ISIS Model

Approach 4

DIFRES has focussed on the linkage between CS4 and CS2 and develop the synergistic components from both of these case studies. This approach focuses mostly on the fleet-based effects of stock-based management procedures (TAC) in a mixed-fisheries context. The main issue dealt with here is how to account for technical interactions and fishermen behaviour in the Management Strategies Evaluation. The various stocks must not be considered separately, but rather together in an integrated manner, since the catches of each stock are also dependent of the effort exerted on other stocks, and thus, of the management objectives for those. In particular, the current TAC system is meant to create discards of valuable fish, because it is not always possible to avoid catching a stock whose quota is exhausted, while targeting another one.

As such, most effort has been put on (i) description of the international fleets and metiers, and their technical interactions, (ii) development of the Fcube approach for the analysis of mixed-fisheries management, (iii), linkages with economic modelling of the dynamic of the fleets and (iv) evaluation of some current single-species Harvest Control Rules (HCR) in the mixed-fisheries context.

Two major works have been developed in parallel, and are presented below. In one side, a complex full feed-back and stochastic MSE including some major sources of uncertainty has been developed, including cod-haddock interactions only. The dynamics of all stocks are calculated simultaneously at each time step of the MSE, depending on a level of effort common for all stocks. This model was built alongside the guidelines and software developement from WP3, and participated in turn largely to the improvement of FLR in terms of fleet-based objects and methods.
On the other side, a specific approach has been developed for investigating the consistency of the various single-species management objectives in the short-term, taking into account simple hypotheses about fleet behaviour. This was done within EFIMAS as well as ICES SGMixMan and EU FP6 AFRAME. This approach, called Fcube (“Fleets and Fisheries Forecast”) was run for the main demersal species in the North Sea (cod, hadock, whiting, saithe, plaice, sole and Nephrops).

Ultimately, both works will be merged in order to get a complete approach testing alternative single-species management objectives for the whole North Sea demersal fisheries, including economic aspects as well as both short-term and long-term considerations. This will done within the final year of EU FP6 AFRAME project.

In general, it has been assured that the work under CS4 is done in cooperation with the work under Case Study 2, Approach 1 (and Approach 3), as well as in coperation with Case Study 6, Approach 2. This has been with focus on the mixed fisheries aspects as well as the discard issues in these mixed roundfish and nephrops fisheries.

Approach 4, Results of evaluating Mixed Fisheries and Discard Scenarios in the North Sea Mixed Roundfish and Nephrops Fisheries using the OM developed under: Approach 4 similar to Case Study 2 Approach 1

Dissemination

Bastardie, F., Pelletier, D., Mahevas, S., Guyder, O., Thebaud, O., Santurtun, M., and Prellezo, R. (Submitted). ISIS-FLR: a spatially and seasonally bioeconomic model for mixed fisheries. Application to the Northern hake / Nephrops fisheries of the Bay of Biscay (and Celtic Sea). Submitted ELSEVIER.

Dobby, H. & Hillary, R. (2008). Sensitivity testing of a length-based approach to Nephrops stock assessment using FLR. Report of EFIMAS Case Study 4a.

Catchpole, T.L. , A.N. Tidd, L.T. Kell, A.S. Revill and G. Dunlin. 2007. The potential for new Nephrops trawl designs to positively effect North Sea stocks of cod, haddock and whiting Fisheries Research Volume 86, Issues 2-3, September 2007, Pages 262-267. Catchpole et al 2007

ECONOWS (2008). ECONOWS: Report from the Economic Workshops of EFIMAS.

EFIMAS Irish Sea Nephrops Report

EFIMAS-NECESSITY Changes in Gear Selectivity_Nephrops_Portugal

EFIMAS_Nephrops case study_Portugese Report

EFIMAS_Nephrops_case_study_Bay of Biscay_France

Hoff, A., and Frost, H. (2006). Economic response to harvest and effort control in fishery. Report no. 185. Institute of Food and Ressource Economics. Copenhagen.

Hoff, A., Frost, H. (2008). Modelling economic response to harvest and effort control in the North Sea cod fishery. Aquat. Living Resour., 21 (forthcoming).

ICES SGMixMan 2006, 2007, 2008

ICES WKNEPHSEL 2007

MSE :
Presentation to AFH (French Association of Fisheries Science) Conference, 19-21 June 2007, La Rochelle, France
Presentation to MODSIM07 Conference, 10-13 december 2007, Christchurch, New Zealand
with Hamon et al. peer-review publication in conference proceedings

Presentation to ICES SGMixMan, January 2008.
Presentation to EFIMAS Conference, March 2008.

Fcube :
Presentation to ICES SFMS, ICES Symposium on Fisheries Management Strategies, 27-30 June 2006, Galway, Ireland.
Reeves and Ulrich, 2007 paper presented to ICES ASC, 17-21 September 2007, Helsinki, Finland.
Presentation to ICES AMAWGC, February 2008

Links to Other Work

This works links up to the work in EFIMAS Case Study 2 and Case Study 6 as described above. Also, the work uses data provided from the EU FP6 NECESSITY Project as well as deliver needed simulations to the results of the NECESSITY Project. Furthermore, the work is conducted in cooperation with the ICES Nephrops Assessment Working Groups. Some of the work in relation to development of some of the simulation models in B-Adapt (CS4 Approach 1) has been done under a English national project. The ISIS-Fish Model has as well been applied under Case Study 9 besides in Case Study 6 and here in Case Study 4.

(See also under Dissemination)

References

Bastardie F., Pelletier D., Mahevas S., Guyader O., Thebaud O., Sauturtun M., Prellezo R. 2008 ISIS-FLR: An FLR-based bioeconomic operating model for mixed fisheries: framework and application submitted

Bell, M., Redant, F and Tuck, I. 2007. Nephrops species. In Lobsters: Biology, Management, Aquaculture and Fisheries. Edited by B. Phillips, Blackwell Publishing, Oxford.

Catchpole, T.L. , A.N. Tidd, L.T. Kell, A.S. Revill and G. Dunlin. 2007. The potential for new Nephrops trawl designs to positively effect North Sea stocks of cod, haddock and whiting Fisheries Research Volume 86, Issues 2-3, September 2007, Pages 262-267.

Chambers, J., M. 2000. Programming with data - a guide of S language, Mathsoft.

Drouineau, H., Mahevas, S., Pelletier, D., Beliaeff, B. 2006. Assessing the impact of different management options using ISIS-Fish: the French Merluccius merluccius - Nephrops norvegicus mixed fishery of the Bay of Biscay. Aquat. Living Resour., 19, 15-29

ECONOWS (2008). ECONOWS: Report from the Economic Workshops of EFIMAS.

EFIMAS Addendum to ContractEFIMAS_502516_Addendum to Contract_24May2006

Hoff, A., and Frost, H. (2006). Economic response to harvest and effort control in fishery. Report no. 185. Institute of Food and Ressource Economics. Copenhagen.

Hoff, A., Frost, H. (2008). Modelling economic response to harvest and effort control in the North Sea cod fishery. Aquat. Living Resour., 21 (forthcoming).

ICES, 2003a. Report of the Working Group on Nephrops Stocks. ICES CM 2003/ACFM:18.

ICES SGMixMan 2006, 2007, 2008

ICES WKNEPHSEL 2007

Mahevas S., Pelletier D. 2004. ISIS-Fish, a generic and spatially explicit simulation tool for evaluating the impact of management measures on fisheries dynamics. Ecological Modelling, 171, 65-84

Mahevas, S., Bertignac, M., Daures, F., Guyader, O., Marchal, P., Pelletier, D., Prellezo, R., Santurtun, M., Thebaud, O. 2006. Hake/Nephrops mixed fishery of the Bay of Biscay: ISIS-Fish 2.0 parametrization in TECTAC report.

Sullivan, P. J., Lai, H-L & Gallucci. 1990. A catch-at-length analysis that incorporates a stochastic model of growth. Can. J. Fish. Aquat. Sci., 47:184-198.

Tuck, I. D., Chapman, C. J. and Atkinson, R. J. A. 1997. Population biology of the Norway lobster, Nephrops norvegicus (L.) in the Firth of Clyde, Scotland – I: Growth and density. ICES J. of Marine Science, 54: 125-135.

Acknowledgements

EFIMAS Contribution to the work

The main work has been conducted under the EU FP6 EFIMAS Project, among other this works links up to the work in EFIMAS Case Study 2 and Case Study 6 as described above. However, much work has also been done in relation to the EU FP6 NECESSITY Project, as EFIMAS uses data provided from the EU FP6 NECESSITY Project. On this basis EFIMAS deliver needed simulations and direct results from those to be used in the NECESSITY Project. Furthermore, the work is conducted in cooperation with the ICES Nephrops Assessment Working Groups.

Participants

Coordinator: Andy Revill, Topcic Leader Helen Doby

Participants: Sten Munch-Petersen, J. Rasmus Nielsen, Clara Ulrich-Rescan, Katell Hamon, Ayoe Hoff, Hans Frost, Francois Bastardie, Dominique Pelletier, Laurence Kell, Alex Tidd, Richard Hillary, Coby Needle, Steven Holmes, Liz Clarke, Fátima Cardador, Cristina Silva, Wim Demaré, Ciaran Kelly, Jos Smit, Simon Mardle, Sean Pascoe, Frank Redant, ………..

Meeting Documents and Other Case Specific Work - working documents, models, analyses etc.

  • Delivery Matrix by April 2006 (Note: See text from Meeting Minutes WP4 from EFIMAS Maastricht Meetings, September 2006).

annex_portuguese_report_nephrops_cs4.pdf Assessing immediate and long-term effects on landings and spawning stock biomass in Norway lobster (Nephrops norvegicus) from the Southwest and South of Portugal by changing trawl codend mesh size, mesh configuration and introducing sorting grids. Fátima Cardador (1), Paulo Fonseca (2), Cristina Silva (1) and Aida Campos (2)

(1) EFIMAS/IPIMAR, (2) NECESSITY/IPIMAR

Nephrops - changes in gear selectivity

Presentation of IPIMAR Contribution to EFIMAS Case Study 4 at NECESSITY meeting - Crete (March 2007)

Fátima Cardador 2007/04/27 12:00

J. Rasmus Nielsen 2007/02/03 10:34J. Rasmus Nielsen 2008/06/10 14:10J. Rasmus Nielsen 2008/11/04 15:22

 
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