A fp7 Project: Management and Monitoring of Deep-sea Fisheries and Stocks wp2 – Template for Case Study Reports Case study 2 demersal deep-water mixed fishery Pascal Lorance, Ifremer, Nantes (coord.)
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- Roundnose Grenadier Vb, VI, VII, XIIb
- Black scabbardfish in V, VI, VII, XII
- Portuguese dogfish and leafscale gulper shark
- 3.3.2.Description of benchmark assessments, agreed best practise and rationale
- 3.3.3.Addressin uncertainty
- 3.3.5.Retrospective analyses of assessments
3.3.Assessment methods3.3.1.Justification of the method: for exploratory assessments please describe reasons for selecting the method(s) used. Was any guidance available as to the type of method to use? If so please describe.Only assessment methods used since 2006 are taken into account in sub-section by stock. In the early 2000s, exploratory assessment used De Lury and Schaefer production models (Basson et al. 2002). Roundnose Grenadier Vb, VI, VII, XIIbThis stock is in a data-poor situation with uncertainties in XIIb, and about the level of discards. Therefore, only exploratory assessments can be performed. Discards were taken into account in the assessment in 2008 (WGDEEP, 2008). In 2009 a comparison between assessments including or not discards or using a rebuilt catch time series from science surveys and industrial data showed biomass in recent year is at the same level for all methods (Pawlowski and Lorance, 2009). The inclusion of discards does not substantially change the estimated stock trend in recent years. At the beginning of the fishery, levels of biomass differed between methods. However, there is not enough information on the level of discards in the early 1990s to make sound assumptions that could give credentials towards a particular method to estimate biomass. Due to the lack of information, all age- or length- based assessments were considered not suitable for further development at the ICES WKDEEP benchmark in 2010. A Bayesian surplus production model as well as indicators such as catch-curves and abundance indices from LPUEs were considered to be suitable to describe the trends of this stock. Black scabbardfish in V, VI, VII, XIINo assessment is performed other than reviewing trends in CPUEs from the French fleet of deep-water trawlers database. However the time series is too short to be useful for stock assessment. The state-space model is under development as part of DEEPFISHMAN. Greater forkbeardNo quantitative assessment is performed for this stock. An exploratory model has been presented at the ICES WKDEEP 2010. This model is a Stock Depletion Model based on Roa-Ureta and Arkhipkin (2007) and is intended to be used for data-poor situations. It relies on historical series and landings and effort of the Basque Country trawlers operating in Subareas VI, VII and VIII from 2001 to 2008. For greater forkbeard, it is likely that only trends in survey indicators can be used for assessment purposes because of the by-catch status of the species. Portuguese dogfish and leafscale gulper sharkFor both species, no assessment has been carried out since 2006 other than reviewing trends in CPUEs. An exploratory model has been presented at the ICES WKDEEP 2010 for portuguese dogfish only. The population model is a state-space model that divides the population system dynamics into two processes running in parallel: an unobserved process that describes the female shark’s population abundance in number and an observational model on annual catches. Surplus production model like the one used for Roundnose grenadier is considered as a potential candidate for leafscale gulper shark but not assessment has been carried out so far. 3.3.2.Description of benchmark assessments, agreed best practise and rationaleRoundnose Grenadier Vb, VI, VII, XIIbA benchmark of this stock has been done in February 2010 (ICES WKDEEP). Due to uncertainty in the landings occurring in division XIIb, this area has been excluded from the assessment. As a preparatory process, the main challenges (changes in the fishing depth, discards, uncertainties on ALKs) with the assessment and available data have been presented during the ICES Method Working Group (WGMG, 2009) and some work was performed to quantify the effect of uncertainties on age-length key over the assessment. The members of the working group considered age- or length- based models not adequate for this stock and suggested other approaches such as analysis of commercial LPUEs and life stage-based models. Uncertainties about discards and errors from ALKs are possibly the major weaknesses of the assessment for this stock. Multi-Year Catch Curve: this model brings mortality estimates. From assumption on natural mortality, it is therefore possible to estimate the fishing pressure. This model makes use of catch and landings in number data and quite easy to implement although it is still under development. Abundances indices from LPUEs make full use of haul-by-haul data provided by the French industry based upon tallybooks from volunteer vessels. The details from haul-by-haul database permit to estimate reliable abundance indices as information such as changes in practices and fishing gear/grounds is taken account. Standard logbook data do not have such resolution therefore their reliability is limited to the appropriateness of the assumption made on fishing effort. The adopted assessment model at the ICES WKDEEP benchmark workshop was a Bayesian surplus production model (based on Pella Tomlinson biomass dynamic model). This approach, only considered as indicative of trends, was selected as it was considered as the most parsimonious approach with respect to the lack of data and short time series. The reliability of the model output is expected to improve over time when more data accumulate. Black scabbardfish in V, VI, VII, XIINo benchmark assessment has been performed. Greater forkbeardNo assessment method has been adopted at the ICES WKDEEP benchmark workshop in 2010. This stock should be assessed based upon survey indicators. Portuguese dogfish and leafscale gulper sharkNo assessment method has been adopted at the ICES WKDEEP benchmark workshop in 2010. 3.3.3.Addressin uncertaintyRoundnose Grenadier Vb, VI, VII, XIIbPrevious exploratory assessments have not included so far uncertainties. Uncertainties on ALKs and level of otolith samplings have been included in a benchmark assessment by bootstrapping the ALK and evaluating the effects for the assessment of using ALKs of different sizes. The current Surplus Production model used for this stock within ICES WGDEEP is Bayesian and therefore provides probabilities of distribution of biomass and fishing mortality for each year of the run as well as probabilities of distribution of MSY indicators. Black scabbardfish in V, VI, VII, XIINo quantitative assessment carried out. Greater forkbeardNo quantitative assessment carried out. Portuguese dogfish and leafscale gulper sharkNo quantitative assessment carried out. 3.3.4. Multispecies: is your stock included in any multi-species assessments? If so please describe. If not should it? If yes, please describe a suitable way to go forwardMonospecific assessments have been mostly exploratory, poorly reliable, most often strongly driven by a single time series of abundance index from the French trawl fishery. Abundance index need to be revisit using (1) longer time series now available (more years with both additional recent years and files from 1984 put back into the current format of the Ifremer statistics database). In addition to this archive data back to 1972 have also been made available recently (at least years 1972-79 being incomplete and reliability need checking). Ttally book data on a haul by haul basic allows for better assessment of the impact of fishing tactics on catch. This could allow for a better interpretation of trends in abundance indexes. The most obvious example is with change over the fishing depth over time. On-board observation data also provide knowledge of the species composition of the catch according to fishing strategy The project could consider developing range of indicators by species, for groups of species and the total catch. This should provide some multispecies assessment to analyse questions such as:
Lastly, a multispecies modelling is envisaged for the case study in WP4. 3.3.5.Retrospective analyses of assessmentsNo retrospective analysis is performed on the Roundnose Grenadier assessment nor for any other deep-water species assessed in ICES Subareas V, VI, VII and XII. Directory: lib -> exe exe -> Homework Problem Set 3 Solution I. Reading Assignment exe -> System Modeling Assessment & Roadmap wg exe -> Artemis-2011-1 decision and platform support for model‐based eVolutionary development of Embedded systems Date of preparation exe -> Date: January December 2011 Java 5 Language psm for dds (dds-java) exe -> Notes on bcd by N. Toge (Jan. 5, 2005) Instrumentation and Control General exe -> Case Study 3 Report – Black scabbardfish in ixa exe -> 1 Beneficiaries (Partner Description) exe -> Pre-requisites exe -> Suggested (Sample) Research Project Topics (Fall 2010) Download 2.38 Mb. Share with your friends:
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