Article

A Precautionary Approach to Assessment and Management of Shrimp Stocks in the Northwest Atlantic

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Recent stock assessments for Atlantic Canadian shrimp (Pandalus borealis) stocks, including the Scotian Shelf, the Gulf of St. Lawrence and the Labrador-Newfoundland Shelf, were conducted using the checklist or "Traffic Light" method. Results were viewed positively by many scientists, fisheries managers and industry, and the method has since been adopted by the Northwest Atlantic Fisheries Oganization (NAFO) for "data poor" stocks. It is also being considered by other stock assessment/management organizations. A major drawback of the method in its current form is that it does not link assessments to TACs or other management controls. Modeling results suggest that "Traffic Light" scores can be linked to simple harvest control rules in a way that is consistent with shrimp stock dynamics and management requirements, creating an integrated management framework that could be useful for "data rich" as well as "data poor" stocks.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... The TL displays time series in such a way that helps to perceive likely transitions of indicators and relationships between variables visually (Caddy et al., 2005). This methodology has been applied for single-and multi-species assessments both in the Atlantic and the Mediterranean (Caddy et al., 2005; DFO, 2005; Ceriola et al., 2007, 2008) and appears to be more precautionary than traditional stock assessment methods (Koeller et al., 2000). Over the last times, the methods available to be used in stock assessment models have changed from those using only catch, catch-at-age and survey or CPUE data to methods that use every source of data available in a totally integrated framework (Hilborn, 2003). ...
... Over the last times, the methods available to be used in stock assessment models have changed from those using only catch, catch-at-age and survey or CPUE data to methods that use every source of data available in a totally integrated framework (Hilborn, 2003). In this sense, TL provides a way of bringing a variety of monitoring results, results from traditional stock assessment models and methods, anecdotal observations and political/economic considerations into management decisions (Koeller et al., 2000). One of the main shortcomings in Mediterranean fishery assessments , which is related to their diversity and complexity , is the lack of suitable data because in spite of the existence of fairly reliable historical data series of landings, data on effort are almost absent (Lleonart & Maynou, 2003). ...
... The summary of these indicators, both fisherydependent and independent indicators and both at population and community level, was performed using TL (Caddy, 1999, 2002; Koeller et al., 2000). The TL is a system of red, yellow and green lights which categorise multiple indicators of the state of a fishery and ecosystem, considering red as bad, yellow as intermediate and green as good. ...
Article
Full-text available
The bottom trawl fishery developed on the slope off Balearic Islands (western Mediterranean) has been analysed from different sources of information: (i) data obtained during experimental bottom trawl surveys developed annually since 2001; (ii) daily sale bills from the bottom trawl fleet, available since 2000. Considering both hydrographical and geomorphologic conditions, the study area was divided in four geographical sectors. Multivariate techniques were applied to identify assemblages and their main species, and to investigate the influence of environmental variables in the slope communities. Fishery-independent and fishery-dependent indicators were calculated, both at specific and community level, for the assemblages identified. In all cases, they were summarised using the Traffic Light approach. Three assemblages have been identified in the slope trawl fishing grounds off the Balearic Islands: (1) the almost unexploited shelf break, where teleosts predominate; (2) the upper slope, where teleosts still predominate but crustaceans are also very important (with Nephrops norvegicus as target species); (3) and the middle slope, where crustaceans predominate (with Aristeus antennatus as target species). Depth was the main factor affecting the species composition of the assemblages, although other factors such as area, year and effort level also affect. Indicators estimated from both sets of data suggested an improvement in the state of N. norvegicus, although the results suggest the influence of other factors than fishing impact in the state of this resource. For A. antennatus, marked differences have been found depending on the data source. In the upper slope, indicators suggested an improvement in the state of this assemblage, which can be related to a decreasing trend found in the fishing effort exerted in this depth range. Indicators from the middle slope showed differences for both sets of data. The characteristics of both data sources and of the species analysed are discussed as responsible of these differences. Keywords Nephrops norvegicus – Aristeus antennatus –Assessment–Community–Ecosystem approach–Indicators–Traffic Lights
... Criticisms have been made of the few data series collected for most fisheries, and that few of them incorporate key environmental or other forcing factors. The traffic light system used in fisheries (Caddy 1999, Koeller et al. 2000, Halliday et al. 2001) offers a framework for comparing multiple data series prior to deciding on the critical factors, and which relationships to incorporate into any model of the system being studied. A strategy which avoids building data collection around a specific model, and takes into account key information series outside the immediate area of concern, is less likely to incorporate misconceptions into an eventual management framework. ...
... In his original description, Caddy (1999) In addition to the current year's data being evaluated, Koeller et al. (2000) drew upon a retrospective table of data which showed historical trends in the stock and other variables used in the TL. This stratagem appears to be a less rigorous approach, using historical data that Halliday et al. (2001) refered to as a 'TL stock status index', since it operates ostensibly independently of the approach described above, which they referred to as a 'TL Precautionary Management Framework'. ...
... A traffic light system was used by Koeller et al. (2000) in producing assessment advice for shrimp populations on the Nova Scotian Shelf. In displaying multiple indicators for shrimp populations, a traffic light array was used to follow changes in population characteristics such as biomass or mortality, as well as predator abundance, recruitment and biomass. ...
Technical Report
Full-text available
The Traffic Light approach as a technical procedure was first developed for monitoring the status and level of risk faced by a fish population from fishery-related, environmental, and economic variables (Caddy 1999a). It has also facilitated stock management and stock recovery, in both cases where supporting data series and stock assessment skills were limited. Nonetheless, since the early 2000’s, the range of applications for this methodology have proliferated dramatically into most social and economic sectors, and after a description of the application of the traffic light procedure to fisheries, a second objective of this paper is to show some examples of the recent diffusion of this methodology to a much wider range of applications. Keywords: fishery-related, environmental, and economic variables (Caddy 1999a).
... Efforts are made to develop methodological approaches that were: (1) based on data available at a relatively low cost, and (2) able to provide information on the state of the fishery system acceptable and understandable to all relevant stakeholders. The "Traffic Light" method (TL, Caddy, 1999Caddy, , 2002Koeller et al., 2000) provides a way to evaluate temporal variation of indicator series and to compare the relevance of a wide range of inputs to the management process (Caddy et al., 2005;Michener, 2006). Several papers dealing with the precautionary approach to fisheries indicated the TL as a potentially powerful tool for developing, displaying and integrating technical information for fisheries management planning (Halliday et al., 2001). ...
... Several papers dealing with the precautionary approach to fisheries indicated the TL as a potentially powerful tool for developing, displaying and integrating technical information for fisheries management planning (Halliday et al., 2001). The TL was proposed as a precautionary management framework incorporating decision rules for management actions based on the current state of multiple indicators (Caddy, 1999(Caddy, , 2002Koeller et al., 2000). Halliday et al. (2001) further elaborated the conceptual basis for using the TL method as a precautionary framework for fishery management, by exploring the interface between stock assessment and the rest of the management system, and making proposals for decision rules formulation. ...
... Based on the colours code, the variations of each indicator can be highlighted and the associated information (i.e. good, intermediate or warning state) made available to set objectives and decision rules in a fisheries management framework (Caddy, 1999(Caddy, , 2002Koeller et al., 2000). This approach can be used to set lower or upper bounds beyond which the fishery should not go. ...
Article
The state of demersal fishery in the Southern Adriatic Sea (GFCM-GSA 18, Central Mediterranean), years 1996–2003, from a biological, social and economic point of view was analysed using 47 indicators: 22 biological indicators obtained from fishery-independent data through yearly experimental bottom trawl surveys (“Medits” Programme), and 25 socio-economic indicators estimated from fishery-dependent data, available from the monitoring system of the Italian Institute for Economic Research on Fisheries and Aquaculture (IREPA). Biological indicators were applied for “single-species” (Eledone cirrhosa, E. moschata, Illex coindetti, Merluccius merluccius, Mullus barbatus, Nephrops norvegicus, Parapenaeus longirostris, Raja clavata, Zeus faber) and for “multi-species” analysis. Economic indicators describing economic performance, productivity, costs and prices, and the overall economic sustainability of fishery were estimated. Social indicators and a general indicator summarising social sustainability were also considered. Indicators’ values were displayed using the Traffic Light system. Both fishery-independent and fishery-dependent indicators highlighted a progressive decline of the trawl fishery system in the GSA 18. This decline was mainly related to the ongoing depletion of the traditional fishery target species (mostly long-living, late-maturing species) partially replaced by the increase of traditional accessory species (generally short-living species), as well as to the reduction of productivity and increasing costs. The whole procedure was proposed as a contribution to the identification and applicability of bio-economic indicators for fishery management purposes.
... For instance, Koeller et al. (2000) presented a performance report for the assessment of a shrimp stock. But in the case of several questions, and this is definitely the case of MPA assessment, the interpretation may become more difficult as the number of entries increases. ...
... "improving", "not changing", "getting worse", "undetermined trend" and "question not applicable". A simplified use of color rating is provided by the traffic-light approach to fisheries management (Koeller et al., 2000;Caddy, 2002 ...
Chapter
Full-text available
Marine protected area (MPA) effectiveness is also termed MPA management effectiveness to emphasize that it relates to how well the protected area is being managed, and primarily the extent to which it is protecting values and achieving the various goals and objectives for which it was created (IUCN-WCPA Guidelines: Hockings et al., 2006). Values include ecosystem services and functions, biodiversity, landscape and geomorphological features, as well as cultural, socio-economic, and research- and education-related aspects. Assessing MPA effectiveness has become a crucial issue as many MPAs are designed all over the world in response to international commitments regarding biodiversity conservation and resource management. Such strong commitments cannot be achieved through ineffective MPAs, either because they are poorly enforced (“paper parks”) or poorly designed. Pressure to evaluate management effectiveness is also increasing in a world where accountability and performance evaluation is more and more compelling. While several previous chapters have focused on the assessment of MPA effects, I here consider the issues of assessment in the light of decision support for MPA management. Rather than assessing MPA effects, the focus is thus on assessing MPA effectiveness with respect to intended management objectives.
... The 'traffic light approach' (TLA) describes a management framework using colours to categorise and review the state of multiple indicators (Caddy, 1999;Halliday et al., 2001;Caddy, 2002;Caddy, 2004) and has proved to be popular with the fishing industry and fishery managers as a format for the basis of discussions on stock status (Koeller et al., 2000). Caddy (1999) proposed a series of over 30 quantitative and qualitative indicators whose current values could be scored against reference points to determine whether they have 'red', 'yellow', or 'green' status -'red' being associated with concern about the current and/or future stock status, 'yellow' an intermediate level representing uncertainty about the future status and 'green' with a positive outlook. ...
... Alternatively, pre-agreed management actions may become gradually more severe (for example in terms of effort limits) with increasing number of indicators pointing towards a deterioration. Koeller et al. (2000) showed using simulation testing for a northern shrimp population model that it is possible to link the combined TLA scores to formal management decision rules. In the scenarios tested, they found that a harvest rule based on the combined score from a greater number of indicators performed better in terms of both yield and risk to the stock. ...
... For instance, Koeller et al. (2000) presented a performance report for the assessment of a shrimp stock. But in the case of several questions, and this is definitely the case of MPA assessment, the interpretation may become more difficult as the number of entries increases. ...
... "improving", "not changing", "getting worse", "undetermined trend" and "question not applicable". A simplified use of color rating is provided by the traffic-light approach to fisheries management (Koeller et al., 2000;Caddy, 2002 ...
... TL displays time series indicators in a way that helps to give a clear visual impression of the likely transitions and relationships between the indicators (Caddy et al. 2005). This methodology has been applied for single-and multi-species assessments both in the Atlantic and the Mediterranean (Caddy et al. 2005, DFO 2005, Ceriola et al. 2007) and tends to be more precautionary than traditional stock assessment methods (Koeller et al. 2000). ...
... Finally, the temporal trends for all the above mentioned variables were summarised using the Traffic Light procedure (Caddy 1999, 2002, Koeller et al. 2000. TL is a system of red, yellow and green colours that categorize multiple indicators of the state of a fishery or ecosystem. ...
Article
Full-text available
We assessed the elasmobranch communities exploited by the bottom trawl fishery off the Balearic Islands (northwestern Mediterranean) by analysing two time series containing information with different levels of detail: 1) a long-term series containing the abundance indices of the whole elasmobranch community landed from 1965 to 2009; and 2) a shorter time series from 2000 to 2009 from two different data sources (daily sales records: 2000-2009; bottom trawl surveys: 2001-2009), with information that allowed the shelf and slope to be analysed separately and different community parameters and abundance indices to be studied. Temporal trends of all these variables were used as ecological status indicators and tested with generalized additive models and analysis of variance. They were finally summarised using the Traffic Light methodology. The long-term series showed two marked trends, an inter-annual decreasing trend that would be a consequence of the large increase in fishing effort, and an intra-annual trend with a clear peak in May in accordance with the seasonal biological cycle of these species. However, data from the last ten years revealed differences between the shelf and slope, as some parameters increased significantly over time on the shelf but did not follow any trend on the slope. The Traffic Light methodology captured these differences well, demonstrating its usefulness for interpreting ecological transitions at a glance
... Fortunately, the water mass anomaly was detectable months in advance by the existing coastal ocean observing system, and this knowledge can be used to improve future forecasts. As a start, something akin to a "traffic light" approach (Koeller et al. 2000;Caddy and Defeo 2003) could provide a caveat to interpretation of the forecast when anomalous conditions are detected. Nevertheless, ongoing monitoring is necessary as conditions can change during the forecast period itself. ...
Article
For the period 2005-2009, the abundance of resting cysts in bottom sediments from the preceding autumn was a first-order predictor of the overall severity of spring-summer blooms of Alexandrium fundyense in the western Gulf of Maine and southern New England. Cyst abundance off mid-coast Maine was significantly higher in autumn 2009 than it was preceding a major regional bloom in 2005. A seasonal ensemble forecast was computed using a range of forcing conditions for the period 2004-2009, suggesting that a large bloom was likely in the western Gulf of Maine in 2010. This did not materialize, perhaps because environmental conditions in spring-summer 2010 were not favorable for growth of A. fundyense. Water mass anomalies indicate a regional-scale change in circulation with direct influence on A. fundyense's niche. Specifically, near-surface waters were warmer, fresher, more stratified, and had lower nutrients than during the period of observations used to construct the ensemble forecast. Moreover, a weaker-than-normal coastal current lessened A. fundyense transport into the western Gulf of Maine and Massachusetts Bay. Satellite ocean color observations indicate the 2010 spring phytoplankton bloom was more intense than usual. Early season nutrient depletion may have caused a temporal mismatch with A. fundyense's endogenous clock that regulates the timing of cyst germination. These findings highlight the difficulties of ecological forecasting in a changing oceanographic environment, and underscore the need for a sustained observational network to drive such forecasts.
... There is no consensus in fishery science regarding the management of prawn stocks. Management advice for most prawn stocks in the North Atlantic is basically formulated by a qualitative assessment of trends in stock condition in response to catch history (Koeller et al., 2000). For the relatively slow growing prawns of northern waters, the use of standard techniques such as VPA and length-based methods has not been successful (Quinn et al., 1998). ...
Article
Full-text available
This study estimates reproductive parameters (length at first maturity, reproduction period, and fecundity), mortality, and maximum sustainable yield for Macrobrachium amazonicum on Combu Island (Amazon estuary). Samples were taken monthly between March 2003 and February 2004. Ovigerous females were recorded throughout the year, with reproductive peaks in the middle of the flood period (March), in the low water period (September), and the peak dry period (December) of the Guamá River. The size at which 50% of the females were mature was 60.8 mm TL. Absolute fecundity varied between 40 and 3375 eggs per female. The exploitation rate for maximum sustainable yield (EMSY) for males was lower than that for females. For both sexes, EMSY was below the exploitation rates (E). The present study demonstrates the need for management of the prawn fishery on the islands in the Amazon estuary, such as establishing a minimum commercial size. Spanish Este estudo tem o objetivo de estimar os parâmetros reprodutivos (tamanho de primeira maturidade, período reprodutivo e fecundidade), mortalidade e rendimento máximo sustentável do Macrobrachium amazonicum da Ilha do Combu (Estuário Amazônico). As amostras foram coletadas mensalmente, entre março de 2003 e fevereiro de 2004. Fêmeas ovígeras foram registradas ao longo de todo ano, com picos reprodutivos no meio da enchente (março), vazante (setembro) e pico de mínima vazão (dezembro) no Rio Guamá. O tamanho na qual 50% das fêmeas estão maduras é de 60,8 mm de comprimento total. Fecundidade absoluta variou entre 40 e 3375 ovos por fêmea. A taxa de exploração para a obtenção do rendimento máximo sustentável (ERMY) para machos foi inferior ao obtido para as fêmeas. Para ambos sexos ERMY foi abaixo das taxas de explotação atuais (E). O presente estudo demonstra a necessidade do manejo da pesca de camarão nas ilhas do estuário Amazônico, como por exemplo o estabelecimento de tamanho mínimo de comercialização.
... Ideally we should use biomass to monitor changes in species status but this would allow only a fragmentary picture of historical events, and the 33 yr FAO landing data set is of course too short to cover the higher levels of commercial production which occurred prior to 1970 for some long-exploited species such as cod, which is an inevitable deficiency of the results presented here. Other uses of a traffic light display were by Koeller et al. (2000) to monitor shrimp populations, who used a traffic light array to display multiple indicators for a range of population characteristics such as biomass or mortality, as well as predator recruitment and biomass. Another by monitored a wide range of indicators for age group abundance and environmental/fishery changes for a crab, Chionoecetes opilio, and from regularities in the traffic light chart suggested an approach to fishery forecasting. ...
Article
Fishery landings data series from 1970 to 2002 for the Northeast (FAO Area 27) and Northwest Atlantic (Area 21) with 73 and 42 species or species groups respectively, were mapped onto single charts as a diagnostic of the overall state of fisheries in these two regions, and could be appreciated simultaneously for the entire exploited suite of species as a series of contiguous bar charts. Charts were compared with that for a similar data set of 42 species or species groups from the Mediterranean and Black Seas (FAO Area 37). A “traffic light convention” partitioned the range of landings by species over the period into four equal intervals; coloured respectively red, yellow, green and blue between zero and the highest annual landing of the species. This allowed a model-free display of changes in the timing of species’ landings at the overall ecosystem level, as represented by the important commercial resources in the three areas. The year T 50 by which 50% of species landings had been harvested over the period, was considered a comparable measure of the response of individual species to exploitation. For a significant proportion of groundfish and pelagic fishes, the time to reach T 50 occurred early in the Atlantic time series. The hypothesis was tested that this measure of the depletion schedule is related to some aspect of species biology, as judged by data from the FISHBASE database. Except for commercial invertebrates where landings peaked late in the Northwest Atlantic time series, no significant regression was found between T 50 values per species and any biological characteristic of the species of finfish tested, suggesting that scheduling may reflect overcapacity and targeting by fisheries and/or regime changes. A decline in peak landings proceeded sequentially over time for the large proportion of all finfish species in the North Atlantic following a broadly similar trajectory. Possible exceptions were deeper water species where fisheries began later, suggesting that “fishing down the bathymetry” has occurred. A more synchronous “pulse” of high landings occurred in the Mediterranean and Black Seas in the mid-late 1980s, which was postulated as due to an increase in system productivity. Although regime changes and quota management cannot be excluded as partly responsible for the persistent low landings late in many time series, the main conclusion is that for all three areas, the effects of fishing overshadow those resulting from differing biological characteristics, habit, or species interactions. Although quota control may in part be responsible for low landings of some species late in the time series, the fishery management regimes that applied during 1970–2002 cannot be considered sustainable. This was confirmed by comparative analysis fitting a variety of models to the raw landing data. Of the mathematical models considered, the Hubbert curve, first used to predict the trajectory of extraction of non-renewable petroleum resources globally over time, best fitted the largest proportion of species time series. This seems to confirm that a hypothesis of harvest sustainability cannot be supported by the landing data.
... Science courts, structured fora for confrontation between opposing sides in controversies have been tried with some success (Irwin 1995). Guston (1999) Koeller et al. (2001) describe the use of the "traffic light" method which is gaining acceptance in Canada. This is based on a simple trichotomy of green, yellow, red 1, 0, -1 which are summed across a matrix indicators of such things as fishing success, stock abundance, resource productivity. ...
... The close linkage between indicators and RPs for the same indicator series needs to be borne in mind, and can be expressed as a 'phase diagram' colour coded as in figure 4 using the 'traffic light' approach, and extended to multiple indicators (e.g. Caddy 1999b; Koeller et al. 2000; Halliday et al. 2001). Definition of boundary values may be established by consensus or based on experience with the fishery in previous years, rather than relying solely on critical values generated by population models. ...
Article
Full-text available
The management of marine fisheries needs to undergo dramatic change in the new millennium, in response to the well–documented evidence of global overfishing and the general depletion of commercial fish stocks. The axioms of sustainable development and equilibrium productivity of wild ecosystems are identified as misleading concepts, which nonetheless underlie current approaches to the management of living marine resources. Current trends in marine fisheries landings worldwide provide little evidence of sustainability of marine resources under current management paradigms, where biological, economic and social aspects of fisheries are usually treated as different disciplines. While open–access conditions are less widespread than formerly, except for many straddling and highly migratory resources, fishers usually have access to the resource year–round throughout its range. Despite quotas, the nominal control of capacity and technical measures protecting juveniles, top–down management has generally been unable to prevent stock depletion, particularly of the older spawners that for demersal stocks often support recruitment. An integrated solution to the complexity of managing wild resources seems not to have been achieved. Any new paradigm should assert the basic unpredictability of fisheries at the system level and require a broader range of performance indicators to be incorporated into the decisional framework. This must reflect the non–equilibrium nature of marine systems, and give greater importance to resource (as opposed to harvest) continuity in the face of regime shifts, and promote habitat restoration and conservation of genetic resources. The new management framework requires co–management and collective decision–making to be incorporated within a precautionary and pre–negotiated management framework. This must explicitly recognize that decision–making occurs in conditions of model–based uncertainty and precautionary approaches should be incorporated at all levels, not least of which is to avoid the assumption that all resources can be harvested in a sustainable fashion through time. Redundancy in data inputs to management are needed to avoid the surprises that model–based sampling occasionally leads to, for example, when regime changes reduce productivity in response to climatic fluctuations. Emergency frameworks imposing non–discretionary rules must be invoked when overfishing and/or regime change trigger reference points indicating stock depletion. Non–discretionary recovery plans should then override rights–based systems and persist until fish populations recover to pre–established healthy levels, which may in turn need to await the return of a favourable regime. In fact, some stocks may require periodic rebuilding after regime–induced collapses or because of a combination of ecological or economic impacts, hence a constant harvest policy may not always be possible. It will probably also be necessary to discard the axiom that a stock should be available to harvesting throughout its range and seasonal cycle. Technological advances mean that time– and area–specific access rights are now practical options, through satellite monitoring of vessel operations, even offshore. More fundamentally, the basic axiom of ‘enlightened self interest’ underlying current methods of management will need to be tempered by an increased ethical concern for the fragility of natural ecosystems.
... This method establishes a precautionary decision framework based on a multiplicity of indicators based on biological, fishery and environmental data (and can include the outputs from complex assessment models). The Traffic Light approach has been applied in some cases where there were insufficient data to allow the use of mathematical modelling, such as assessments for shrimp (Koeller et al. 2000) and crab (Caddy et al. 2005), but has not yet been accepted as a preferred alternative to reliance on traditional methods. ...
Article
The roots of fisheries science on the Atlantic coast of Canada go back to 1898.The primary research agencies were the Fisheries Research Board of Canada andpredecessors until the early 1970s and subsequently the federal department responsible for fisheries. Canadian research on Atlantic fisheries expanded substantially after the Second World War, at about the time the International Commission for the Northwest Atlantic Fisheries was formed, and increased again after the 1977 extension of fisheries jurisdiction, but gradually declined from the 1980s. Initially research was directed at improving and expanding the fisheries through exploring for new resources and by introducing and testing new fishing methods and new processing technologies, but increasingly was directed towards rational exploitation of the fisheries as international fishing effort greatly expanded in the 1960s. By the 1980s, the provision of short-termadvice on catch limits occupied a large proportion of science resources. This paper describes these changes with primary reference to groundfish fisheries, which were the most important for much of the period.Les racines des sciences halieutiques sur la côte atlantique du Canada remontent à 1898. Jusqu’au début des années 1970, les principaux organismes de recherche étaient le Conseil de recherche sur les pêcheries du Canada et ses prédécesseurs. Par la suite, le ministère fédéral responsable des pêches a assumé ce rôle. La recherche menée au Canada sur les pêches dans l’Atlantique a pris beaucoup d’ampleur après la Seconde Guerre mondiale, à peu près au moment où la Commission internationale pour les pêcheries de l’Atlantique Nord‑Ouest a été créée, et également après l’élargissement du champ de compétence du Canada en matière de pêche en 1977, mais elle est en période de déclin graduel depuis les années 1980. Au début, la recherche était axée surl’amélioration et l’expansion des pêches par le biais de l’étude de nouvelles ressources et de l’élaboration et de l’essai de nouvelles méthodes de pêche et technologies de transformation. Au fil du temps, le point de mire de la recherche est devenu l’exploitation rationnelle des ressources halieutiques, étant donné l’important accroissement de l’effort de pêche sur la scène internationale dans les années 1960. Dans les années 1980, une bonne part des ressources scientifiques étaient occupées à fournir des conseils à court terme à propos des limites de prises. Le présent document décrit ces changements en mettant l’accent sur les pêches de poissons de fond, qui étaient les activités les plusimportantes pour la majeure partie de cette période.
... Forecasting fishery performance and stock abundance for northern shrimp is a desirable adjunct to the stock assessment process. Assessment methodology for shrimp, currently used in eastern Canada and by NAFO, interprets and evaluates multiple indicators of stock performance to produce an overall, qualitative evaluation of resource status Koeller et al., 2000). However, most indicators reflect current status while relatively few address prospects for either recruitment (males) or spawning biomass (females). ...
Article
Full-text available
The physical environment of the ocean is believed to have a major influence on pandalid shrimp populations and there are numerous studies that incorporate environmental variables to predict and forecast landings from the fishery and/or resource abundance. Cause-and-effect mechanisms are not clearly understood in many instances but the predictive nature of the relationships provides a potentially powerful forecasting tool. Meaningful indicators of the prospects for shrimp stocks that support valuable commercial fisheries are necessary in a comprehensive stock assessment process. In this paper, a time-series analysis is used to estimate a predictive model for standardized annual catch rates (an abundance index) in a shrimp fishing area off the mid Labrador coast (NAFO Div. 2HJ). Environmental data (annual winter ice cover) are incorporated in a transfer function to improve predictions of catch rates and facilitate their forecasting. Results support the hypothesis that cold conditions, which result in more extensive ice cover, are favourable for the northern shrimp (Pandalus borealis) at early life-history stages. Predictions of annual catch rates fit the observed values well in most cases and a catch-rate forecast for several years is provided. Possible functional mechanisms are discussed.
... Although shrimp are now one of the most important target species in these waters, little progress has been made in developing a standardized predictive tool for stock assessment (cf. Stefánsson et al., 1994;Cadrin and Clark, 1999;Hvingel and Kingsley, 2000;Koeller et al., 2000;ICES, 2001;NAFO, 2001). ...
Article
A new integrated Bayesian framework for making quantitative assessments, predictions, and risk analyses of shrimp (Pandalus borealis) stock development is constructed. A biomass dynamic model, based on the logistic function but including an explicit term for cod predation, suggests that the quantity of shrimp consumed by cod could equal that taken by the fishery. The model proved superior to an alternative model in its ability to estimate parameters central to the assessment; the alternative model subsumed cod predation as part of an overall population growth effect without a time trend. Two series of shrimp biomass indices, catch, cod biomass estimates, cod consumption estimates, and prior distributions of model parameters provided information to the models. Process and observation errors were incorporated simultaneously using a state-space modelling framework. A Bayesian approach was used to construct posterior probability distributions of model parameters and derived variables relevant for management advice, including quantification of future risk of transgressing reference points in relation to alternative management options.
... Re-examination of these reasons deserves some priority in the light of the technical difficulties and changed situations in the North Sea and elsewhere. Pragmatic rules to control catches/landings or effort without direct links to annual stock assessments have been proposed (Koeller et al. 2000;Parma 2002;Walters and Martell 2002;Shepherd 2003). These alternatives may become more widely acceptable in future. ...
Article
This critical review argues that several methods for the estimation and prediction of numbers-at-age. fishing mortality coefficients F, and recruitment for a stock of fish are too hard to explain to customers (the fishing industry, managers, etc.) and do not pay enough attention to weaknesses in the supporting data, assumptions and theory. The review is linked to North Sea demersal stocks. First, weaknesses in the various types of data used in North Sea assessments are summarized, i.e. total landings, discards. commercial and research vessel abundance indices. age-length keys and natural mortality (M). A list of features that an ideal assessment should have is put forward as a basis for comparing different methods. The importance of independence and weighting when combining different types of data in an assessment is stressed. Assessment methods considered are Virtual Population Analysis, ad hoc tuning, extended survivors analysis (XSA). year-class curves, catch-at-age modelling, and state-space models fitted by Kalman filter or Bayesian methods. Year-class curves (not to be confused with 'catch-curves') are the favoured method because of their applicability to data sets separately, their visual appeal, simple statistical basis, minimal assumptions. the availability of confidence limits, and the ease with which estimates can be combined from different data sets after separate analyses. They do not estimate absolute stock numbers or F but neither do other methods unless M is accurately known. as is seldom true.
... It is generally agreed that there is no single indicator that can provide management with all the information required for an EAF (FAO, 2003;Rice, 2003;Jennings, 2005). Rather, a suite of indicators that captures a range of impacts on the various attributes of the ecosystem and their response is required, with the results synthesized or integrated through means such as trafficlight analysis (Koeller et al., 2000;Halliday et al., 2001;Caddy, 2002), multivariate methods DFO, 2003;Coll et al., 2010), or a decision-tree approach Jarre et al., 2006;Trenkel et al., 2007). ...
Article
Full-text available
Bundy, A., Shannon, L. J., Rochet, M-J., Neira, S., Shin, Y-J., Hill, L., and Aydin, K. 2010. The good(ish), the bad, and the ugly: a tripartite classification of ecosystem trends. – ICES Journal of Marine Science, 67: 745–768. Marine ecosystems have been exploited for a long time, growing increasingly vulnerable to collapse and irreversible change. How do we know when an ecosystem may be in danger? A measure of the status of individual stocks is only a partial gauge of its status, and does not include changes at the broader ecosystem level, to non-commercial species or to its structure or functioning. Six ecosystem indicators measuring trends over time were collated for 19 ecosystems, corresponding to four ecological attributes: resource potential, ecosystem structure and functioning, conservation of functional biodiversity, and ecosystem stability and resistance to perturbations. We explored the use of a decision-tree approach, a definition of initial ecosystem state (impacted or non-impacted), and the trends in the ecosystem indicators to classify the ecosystems into improving, stationary, and deteriorating. Ecosystem experts classified all ecosystems as impacted at the time of their initial state. Of these, 15 were diagnosed as “ugly”, because they had deteriorated from an already impacted state. Several also exhibited specific combinations of trends indicating “fishing down the foodweb”, reduction in size structure, reduction in diversity and stability, and changed productivity. The classification provides an initial evaluation for scientists, resource managers, stakeholders, and the general public of the concerning status of ecosystems globally.
... The example inFigure 4 illustrates a procedure for dealing with multiple indicators, including predator recruitment and biomass (Koeller et al., 2000). Several indicators in a traffic light array may measure various population characteristic such as biomass or mortality directly or indirectly. ...
Article
Full-text available
Several teams studying the biology and fishery of swordfish in the Italian Seas, have been recently involved in the first Mediterranean attempts of measuring recruitment processes in this species. The interest of this kind of research was suggested by ICCAT to the Italian MiPAF. In ICCAT studies, recruitment indexes of large pelagic fish, such as swordfish or bluefin tuna, are presented in the framework of VPA assessment, when the structure of the fished stock is studied in details in the time series. They are also related to large scale climatic or oceanographic factors. In the present note we recall the main biological parameters of the swordfish in our study area, the Ligurian Sea, presenting time series of both longline CPUE (kg per 1000 hooks) and recruitment indexes. Possible relationships between recruitment levels and abundance of spawners are also discussed. Results show that the CPUE of swordfish longlines (kg/1000 hooks) since 1992 are increasing. The recruitment index, in terms of number of fish aged 1 per 1000 hooks, doesn’t show a positive trend but is oscillating around an average of 1.72, a figure which appears higher than in oceanic longline fisheries. The adult fish abundance is growing. These positive aspects of the Ligurian fishery appear to be related to the limitation of fishing activities, which were introduced in the study area in the framework of the establishment of an offshore Cetacean Sanctuary.
... The simplicity of the index, which has been acclaimed in many methodologies using the traffic lights approach (e.g. Koeller et al., 2000;Garcia, 2009), guarantees its utility for non-specialist managers. Nevertheless, overly simple composite indices have been criticized as they can be poor in design and structure, they may lack important components of the system they attempt to assess and eventually produce low-quality results that are misleading (Saisana and Tarantola, 2002;Nardo et al., 2008). ...
Article
Full-text available
The present work presents an integrated comparative assessment of the sustainability of fishing tactics or metiers (combinations of area, season, fishing gear, and target species). An index, which includes biological, conservation, socioeconomic, and management criteria, was created for this purpose: the “Metier Sustainability Index” (MSI25). It was designed using the traffic lights approach and comprises 25 indicators that refer to the “health” of the fisheries. Additionally, the MSI25 provides an indication of the “certainty” of that information with regard to the data type/heterogeneity. Subsequently, the index was tested using data from six case studies (81 metiers) from the Mediterranean and the Atlantic. The index showed that 63.0% of the metiers were “sustainable”, 21.0% were “unsustainable” and 16.0% were “under pressure”; 59.3% of characterizations were considered as “certain”. The index evaluation showed significant differences between areas and gears. This paper considers the characteristics of the datasets used, the case management status, and the applicability of the index in improving the management of specific fisheries. Overall, the MSI25 was found to be a useful tool for the evaluation and management of highly heterogeneous fisheries and data from various sources and types.
... A broad indicator-based approach to monitoring successive life history stages and their environment offers more opportunity to pick up changes in critical factors over time, such as might be due to regime shifts or changes in ecosystem components. The traffic light system (Caddy, 1999; Koeller et al., 2000; ) offers a framework for comparing data series prior to deciding what critical factors to incorporate into models. It also provides a way of confronting different indicator series, and comparing the relevance of a wide range of informational inputs to the management process, and is well adjusted for understanding by non-technical audiences. ...
Article
A traffic light procedure is used for comparing temporal evolution of indicators of the snow crab (Chionoectes opilio) abundance, fishery success and environmental change. Indicators related to recruitment success in the fishery between 1968 and 2003 were followed and comparisons with life history stages (in trawl surveys conducted over 15 years) allowed the temporal sequence of events in the life cycle to be established. Although recruitment seems to be synchronized with bottom temperature, and may be related to abundance changes in groundfish predators, the main factors determining recruitment fluctuations appear to be density-dependent interactions between life history stages. Establishing the abundance and timing of successive life history stages using the traffic light approach seems to provide a reliable indication of their passage through the fishery, and might be used to make forecasts of the condition of the fishery several years ahead. The analysis raises the question of which of a number of possible density-dependent factors are dominant. Two management approaches by reference points and fisheries control rules are suggested.
... Consequently, the Integrated Management Plan for the stock, the first in the region, took a conservative approach to harvesting. In addition, a new stock assessment methodology using multiple indicators of stock health and environmental conditions -the 'Traffic Light' approach -was developed and implemented (Caddy 1998;Koeller et al. 2000aKoeller et al. , 2011Koeller 2003Koeller , 2008, taking its cue from the new emphasis on an ecosystem approach to fisheries management. It was the first to do so in the region, and the resultant advice and subsequent management actions led to conservation measures that contributed to long-term sustainability. ...
... We need a procedure for first examining and hence displaying multiple indicators on environment, recruitment, biomass and if possible predator abundance (KOELLER et al., 2000), and the Traffic Light approach has already been adopted for a similar overview role by the SAC subcommittee on Marine Environment and Ecosystems (SCMEE, 2005). This approach allows a large number of indicators to be displayed together in a 'model-free' environment where preconceptions as to causative factors are set aside, and observations that some time series show similarities or differences are allowed to support one or other conclusion as to possible causative factors. ...
Article
Local context and practical constraints are important in deciding on assessment procedures for Mediterranean and Black Sea fisheries, and in formulating management measures that reflect the resource life history, fishery configuration and availability of data. A brief review of existing methods is provided, and a recommendation that practical approaches need to focus on developing the indicators and reference points appropriate for fisheries management decisions. In both the Black Sea and Mediterranean Sea proper, experience suggests environmental and ecosystem concerns must be given a high priority in the assessment process.
... Improving existing methods and developing alternative ways for providing management advice for data-limited fisheries are therefore imperative (Kelly and Codling 2006;Punt et al. 2011;Pazhayamadom et al. 2013). When formal fish stock assessments cannot be completed, expert judgement can be made based on the trend of empirical stock indicators (Koeller et al. 2000). However, many existing methods require reference points and (or) data from a reasonable number of years to detect these trends (Blanchard et al. 2010). ...
Article
Full-text available
We demonstrate a harvest control rule based on the self-starting cumulative sum (SS-CUSUM) control chart that can maintain a fish stock at its starting (status-quo) level. The SS-CUSUM is an indicator monitoring tool commonly used in quality control engineering and does not require a long time series or pre-defined reference point for detecting temporal trends. The reference points in SS-CUSUM are calibrated in the form of running means that are updated on an ongoing basis when new observations become available. The SS-CUSUM can be initiated with as few as two observations in the time series, and can be applied long before many other methods, soon after initial data become available. A wide range of stock indicators can be monitored but in this study, we demonstrate the method using an equally weighted sum of two indicators: a recruitment indicator and a large fish indicator from a simulated fishery. We assume that no life history data are available other than two years of both indicator data and current harvest levels when the SS-CUSUM initiates. The signals generated from SS-CUSUM trigger a harvest control rule (SS-CUSUM-HCR), where the shift that occurs in the indicator time series is computed and is used as an adjustment factor for updating the Total Allowable Catch (TAC). Our study shows that the SS-CUSUM-HCR can maintain the fish stock at its starting status-quo level (even for overfished initial states) but has limited scope if the fishery is already in an undesirable state such as a stock collapse. We discuss how the SS-CUSUM approach could be adapted to move beyond a status-quo management strategy, if additional information on the desirable state of the fishery is available.
... My main problem with most of the above works is not what is said (I agree with just about all of it, except maybe the witch doctoring), but that I wasn't cited anywhere. Perhaps not entirely by coincidence I have applied many of these sentiments in my own approach to fishery management (Koeller et al., 2000). Based on my reference pointless, data-based assessment last year I managed to convince fishermen and managers to decrease the shrimp TAC on the Scotian Shelf by 40%. ...
Article
Applied fisheries science is currently undergoing a fundamental philosophical self-examination. This is due to some spectacular local failures in fish stock management in the recent past, and major international initiatives (ecosystem-based fisheries management, codes of conduct and the precautionary approach) which require interpretation and implementation. There is no shortage of responses to the call for a new collection of fish stock assessment and management systems (paradigm), often in the form of philosophical papers in the sections of scientific journals dedicated to such treatments. In this paper I offer some opinions on the opinions, viewpoints and perspectives which have gained attention over the last few years. It is a practitioner’s opinion. Fish stock assessment should be modeled after medical practice in which the stock is the patient, the biologist is the doctor, and the fishery is the sustainable disease.
... It has been applied for single-and multi-species assessments both in the Atlantic and the Mediterranean (e.g. Caddy et al., 2005;Ceriola et al., 2007) and appears to be more precautionary than traditional stock assessment methods (Koeller et al., 2000). As above, if this approach reveals negative trends in population or ecosystem indicators, corrective measures will be designed. ...
... This approach was firstly proposed as a type of precautionary management framework suitable for use in fishery assessment in data-poor situations (Caddy, 2002), but it can also be used to assess the status of all stocks whether rich or poor in data (Halliday et al., 2001). It has been applied for single-and multispecies assessments both in the Atlantic and the Mediterranean (e.g., Caddy et al., 2005;Ceriola et al., 2007) and appears to be more precautionary than traditional stock assessment methods (Koeller et al., 2000). As above, if this approach reveals negative trends in population or ecosystem indicators, corrective measures will be designed. ...
Article
Full-text available
The serious overfishing of most Mediterranean stocks demands urgent reforms of the management measures aiming to guarantee the sustainability of resources, notably when compared with the improvement observed in other European areas. The new EU Common Fisheries Policy (CFP) constitutes an excellent opportunity to introduce the changes needed for such a reform. According to this CFP, all European fish stocks should be brought to a state where they can produce at MSY by 2020 at the latest. The CFP also establishes that the objective of sustainable exploitation should be achieved through multiannual plans (MAPs) adopted in consultation with relevant stakeholders having fisheries management interests such as fishermen, non-governmental organizations, and policy makers. Together with the MSY and MAP approaches, the new CFP contains several other measures, directed to guarantee the ecological and socio-economic sustainability of fisheries by means of the implementation of the ecosystem approach to fisheries management (EAFM). With this new perspective, the CFP wants to avoid past failures of fisheries management based on monospecific approaches. This study is a first step toward the application of the EAFM in the Balearic Islands by means of the development of a harvest strategy with defined objectives, targets, limits, and clear management control rules aimed at optimizing socioeconomic and ecological objectives in the framework of the new CFP. Different management scenarios designed to achieve that goal were modeled for the main demersal commercial fisheries from the study area, the bottom trawl, and small-scale fisheries. The work begins with a general description of those fisheries, their main fishing grounds, and assessments of the exploitation status of the main target stocks in order to establish the current situation. Secondly, alternative management scenarios to maximize catch and profits while considering societal objectives were evaluated by means of bio-economic models. Thirdly, management measures were provided based on the previous modeling and discussions with stakeholders. Finally, a monitoring scheme was outlined to assess the progresses of the proposed management actions. This work is intended to be a working example of co-management (fishers, policy-makers, and scientists) in the Mediterranean in the framework of the new EU CFP.
... Shrimps are the target of many valuable fisheries in the world and an important internationally traded commodity (Gillett 2008), partly because of their large stock sizes and high productivity, but also because of the high market prices paid for the products. In spite of their commercial and ecological importance, however, many of these stocks are considered ''data poor'', and only very simple assessment methods are applied to manage these valuable resources (Koeller et al. 2000). The case study species for the test of the new methodology, North Sea brown shrimp (Crangon crangon L.), is a typical example: despite annual catches of up to 35,000 t, more than 600 commercial vessels from seven nations and a peak landing value of more than 100 million Euro, the fishery is almost unregulated (ICES 2009). ...
Article
Full-text available
Shrimps are economically and ecologically very important, yet a lack of ageing techniques and hence unknown growth rates often impairs analytical assessments and management. A new method for the determination of in situ growth rates of shrimps is presented, based on dry weight condition. Since this index oscillates from low values directly after moult to highest values prior to moult in constantly feeding shrimp, the lowest observed pre-moult condition followed by a moult was introduced as a reference value to separate growing and starving individ-uals in field data. Experiments with Crangon crangon confirmed that (1) post-moult condition varies in a narrow physiologically optimal range, regardless of recent growth increments, and (2) dry weight condition prior to moult is closely related to the subsequent length increment. The method was applied to estimate growth increments from in situ dry weight condition data of C. crangon. The new method can easily be applied to other related species, since the required data can be obtained from very simple short-term experiments.
Chapter
Full-text available
Environmental Risk Analysis (ERA) consisting of risk assessment, management and communication can be applied to assess ecological and environmental changes associated with industrial-scale marine finfish aquaculture development. Physical, chemical, and biological variables are identified that may be used to detect thresholds for changes in ecosystem structure and function in order to apply ERA. Changes due to predictable or unpredictable effects may be local or far field. Predictable effects such as reduced dissolved oxygen, increased nutrients and organic matter, or lower diversity of benthic fauna in the vicinity of net-pens can be modeled to quantify local impacts on water column and sediment variables. Far-field and long-term risks such as interactions of escapees with natural stocks and effects of fishing to obtain food for cultured fish are more difficult to predict and quantify. Despite this, scoring methods using single or multiple indicators may be applied to determine the degree of risk associated with all identified potentially negative effects. ERA should be part of an integrated planning approach where aquaculture development occurs within abroad framework to include all development and user groups within the coastal zone. Environmental observations and models can then be combined with effective aquaculture husbandry practices to manage environmental risks from all sources.
Article
Growth and sexual development of northern shrimp Pandalus borealis was determined on the Scotian Shelf during two periods, one of low and one of high population abundance, using deviation and modal analysis. Growth rates were higher during the period of low abundance, probably due to density dependent effects and higher temperatures. Faster growth during the first period was associated with a smaller size at transition (Lt) from male to female and a smaller maximum size (Lmax), while slower growth during the later period was associated with a larger Lt and Lmax (and older age). Results are consistent with the theory of invariance in the ratio of pandalid Lt/Lmax and its implications, i.e. that growth can be determined from measurements of Lt or Lmax alone. Lt was not a good indicator of short-term changes in population abundance; consequently Lt or Lmax should be used as measure of growth, not abundance. The theoretical and practical implications of the results are discussed. In particular, it is suggested that decreased fecundity resulting from an increased growth rate and decreased Lt and Lmax is responsible for the negative lagged relationships between temperatures and abundance in stocks at the southern limit of their distribution. It is also suggested that measurements of Lt and/or Lmax could be used in quantitative assessment models and to develop harvest limit reference points.
Article
Progress with stock recovery plans to date for depleted marine resources is reviewed, based on published and publicly available sources. Most plans began within the last two decades, so quantifying progress is difficult, but some 60 cases were found where a recovery effort had been explicitly tackled by either a closure or restrictive measures, and seven documented case studies were used to draw general conclusions on recovery procedures and to provide a list of considerations for best practice in recovery planning. More successes were documented for pelagic .sheries than demersals, especially with closures, while spontaneous recoveries of some depleted invertebrate resources seem related to reductions in predator pressure. Few shared, straddling or highly migratory stocks have been restored to date. Most successful recoveries occurred in the centre of the species geographical range and/or in favourable regimes. Success seems to depend on non-discretionary fishery control laws being applied. Depletions aggravated by unfavourable climatic regimes will be difficult to reverse, as illustrated by a simulation. Durations of recovery plans in particular depend on regime, and using stock information from favourable regimes to predict plan duration should be treated with caution. Although successful recoveries to date have tended to be decadal, a considerable proportion are still underway, and are likely to exceed this duration.
Article
An examination of population trends for northern shrimp (Pandalus borealis) and its key predators off eastern Newfoundland and Labrador provided the basis for investigating predator–prey relationships within an ecosystem that experienced major changes in species composition during the 1980s and 1990s. Populations of several demersal fish species, known to feed on northern shrimp, declined to historically low levels by the early 1990s and remained depressed thereafter. Some declines were precipitous from the late 1980s to early 1990s, coincident with an increase in shrimp. Populations of other important predator species increased throughout the 1990s along with shrimp. Lacking representative estimates of shrimp consumption, the net effect on predation mortality was unquantifiable and it was not possible to demonstrate with certainty that the major increase in shrimp biomass that occurred throughout the 1990s resulted from a concomitant reduction in predation mortality. Factors (and their interactions) relevant to the dynamics of shrimp populations include the effects of ocean climate, predation, competition, as well as commercial harvesting.
Article
Full-text available
Despite the economic importance of Pandalus shrimp fisheries, few analytical tools have been developed to assess their stocks, and traditional stock assessment models are not appropriate because of biological specificities of Pandalus species. In this context, we propose SPAM (Sex-Structured Pandalus Assessment Model), a model dedicated to protandric hermaphrodite pandalids stock assessment. Pandalids are difficult to assess because the cues affecting sex change, size at recruitment, and mortality variability are not well understood or characterized. The novel structure of the model makes it possible to adequately describe variability in natural mortality by stage and in time, as well as variability in size at sex change and recruitment. The model provides traditional stock assessment outputs, such as fishing mortality estimates and numbers of individuals, and provides in addition yearly natural mortality estimates. The model is applied to the exploited shrimp stock of Pandalus borealis in Sept-Îles (Québec, Canada) as an illustrative example of the utility of the approach.
Article
The emerging fisheries science paradigm may be drifting in what some applied fisheries scientists consider an intractable assignment – Ecosystem-Based Fisheries Management (EBFM) or the Ecosystem Approach to Fisheries (EAF). In this paper I suggest that the lack of progress in implementing EBFM-EAF is partly psychological and that the multidisciplinary approach to it should include psychology, a discipline that has largely ignored the overwhelming problems of fisheries management.
Article
Reference points for harvesting Pandalid shrimp are categorized into five general approaches: historical proxies, biomass dynamics models, dynamic pool models, stock-recruit models, and demographic production models. Each of these approaches has different data requirements and underlying assumptions. Estimation of biological reference points from these methods can be viewed as a hierarchy, using data-poor proxies in the lowest tier to applying more informative demographic production models in the highest. Based on a review of Pandalid life histories, precautionary-approach reference points, and methodologies for estimating reference points and their applications to Pandalid shrimp stocks, we advocate a progression from proxies to more informative models and the requisite advancement of research programs to develop reliable reference points for Pandalid shrimp stocks.
Conference Paper
Fatty liver is a common phenomenon concerned in today's healthcare. Using B-ultrasound modality can help identify the abnormal disease in cardiology. This paper presents an extraction method for fatty liver ultrasound image feature. Through the extraction, one can easily analyzes ultrasound images from clinical practices in fatty liver pathology. After selecting a region of interest in a B-ultrasonic image, and introducing a median filter, the quality of image is significantly improved. The selected image region is divided into several small regional areas. By changing the selected image gray-scale and making the average gray of these small pieces, the image features can be easily identified. The difference between abnormal and normal liver are finally identifies through multi-grade gray levels contraction. Experimental results from the proposed method demonstrated its feasibility and applicability for high performance fatty liver classification.
Article
The use of indicators in management of invertebrate resources is placed in the context provided by more extensive applications in finfish fisheries. Indicators proposed for the Convention on International Trade in Endangered Species based on extent-of-decline and trend analysis are appropriate should full assessments be unavailable. Measuring reproductive performance frequently builds on egg-per-recruit considerations, given that age structure and stock-recruit relationships are rarely available. Reference points derived from models are compared with direct use of data series, and a broad-brush approach providing a redundancy of indicators is recommended. Indicators may measure productivity as well as biomass and exploitation rate, but ecosystem, spatial, habitat, environmental characteristics, and socioeconomic considerations also require monitoring. There is a need to integrate multiple indicators and limit reference points into harvest rules and other decisional infrastructures. The various driving force - pressure - state - impact - response classifications of indicators in use for environmental assessment are now being proposed for marine resources and offer one context for combining multiple indicators. Another is provided by the traffic light approach already used for invertebrate fisheries. The use of indicators and reference points in stock rebuilding is described.
Article
This concept paper discusses a semi-quantitative approach to precautionary fishery management easily understood by stakeholders and other non-technical personnel. A check- list is provided incorporating some 30 qualitative or semi-quantitative criteria to be com- pleted by resource experts as a preliminary basis for deciding on priorities for precaution- ary management of marine resources or fisheries. Four tables are provided (incorporating characteristics respectively, of landing trends, environment and ecosystem, the stocks, and the fishery). The scoring of this checklist permits a semi-quantitative comparison between fisheries in terms of their relative vulnerabilities to non-precautionary harvest- ing, and allows qualitative but informed opinions to play a part. This approach may also be used in determining which aspects of the fishery require particular attention from re- search and management, including, if necessary, the formulation of appropriate Limit Reference Points. It is proposed that multiple precautionary reference points be used which are rela- tively simply formulated and understood by stakeholders. These would need to be built into a management system incorporating pre-negotiated responses. Analogous to fuzzy logic principles, a methodology is proposed whereby a suite of simple limit reference points can be tuned to provide a gradated management response to the status of multiple precautionary criteria or indices, possibly including the results of questionnaires described in this paper. In this approach the fisheries management cycle incorporates a resource 'traffic light' in the public domain which indicates the state of the fishery, and incorpo- rates a prenegotiated set of management actions in response to the number of red lights on a multiple Limit Reference Point board. The management action should increase in sever- ity depending on the number of indicators that turn from green to red.
Resource status of northern shrimp (Pandalus borealis) off Baffin Island, Labrador and northeastern Newfoundland second interim review
  • D G Parsons
  • P J Veitch
  • G T Evans
  • Ms
PARSONS, D. G., P. J. VEITCH, and G. T. EVANS. MS 1999. Resource status of northern shrimp (Pandalus borealis) off Baffin Island, Labrador and northeastern Newfoundland second interim review. Can. Stock Ass. Sec. Res. Doc., No. 112: 53 p.
Report of Canadian Atlantic Fisheries Scientific Advisory Committee Special Meeting, Invertebrates and Marine Plants Subcommittee, Shrimp Management Alternatives
  • R K Mohn
  • D G Parsons
  • L Savard
MOHN, R. K., D. G. PARSONS, and L. SAVARD. 1992. Report of Canadian Atlantic Fisheries Scientific Advisory Committee Special Meeting, Invertebrates and Marine Plants Subcommittee, Shrimp Management Alternatives, December 58, 1989. Ottawa, Canada. Can. Tech. Rep. Fish. Aquat. Sci., 1884(iv), 30 p.
Shrimp of the Estuary and Gulf of St
  • L Ms
SAVARD, L. MS 1999. Shrimp of the Estuary and Gulf of St. Lawrence. Fisheries and Oceans, Canada, Science – Stock Status Report, C4-06: 12 p.
Practical application of the precautionary approach. Fisheries Resource Conservation Council (FRCC) Working Paper
  • J.-C Ms
BRÊTHES, J.-C. MS 1998. Practical application of the precautionary approach. Fisheries Resource Conservation Council (FRCC) Working Paper: 13 p.
The Scotian Shelf shrimp (Pandalus borealis fishery in 1999
  • P Koeller
  • M Covey
  • M King Ms
KOELLER, P., M. COVEY, and M. KING. MS 1999. The Scotian Shelf shrimp (Pandalus borealis fishery in 1999. Can. Stock Ass. Sec. Res. Doc., No. 172, 38 p.
A checklist for fisheries resource management issues seen from the perspective of the FAO Code of Conduct for Responsible Fisheries
  • J F Caddy
CADDY, J. F. 1996. A checklist for fisheries resource management issues seen from the perspective of the FAO Code of Conduct for Responsible Fisheries. FAO Fish. Circ., 917, 22 p.
Evaluation des concentrations de crevettes nordiques (Pandalus borealis) du norde du golfe du Saint Laurent (Divisions 4RST de l'OPANO)
  • S Hurtubise
SAVARD, L., and S. HURTUBISE. 1991. Evaluation des concentrations de crevettes nordiques (Pandalus borealis) du norde du golfe du Saint Laurent (Divisions 4RST de l'OPANO): 35 p.
Report of Scientific Council Workshop on the Precautionary Approach to Fisheries Management
  • Nafo
  • Ms
NAFO. MS 1998. Report of Scientific Council Workshop on the Precautionary Approach to Fisheries Management. NAFO SCR Doc., No. 76, Serial No. N3069, 62 p. 1998. Scientific Council Reports, p. 162163.
Practical application of the precautionary approach
  • J.-C Brêthes
  • Ms
BRÊTHES, J.-C. MS 1998. Practical application of the precautionary approach. Fisheries Resource Conservation Council (FRCC) Working Paper: 13 p.
Evaluation des concentrations de crevettes nordiques
  • L Savard
  • S Hurtubise
SAVARD, L., and S. HURTUBISE. 1991. Evaluation des concentrations de crevettes nordiques (Pandalus borealis) du norde du golfe du Saint Laurent (Divisions 4RST de l'OPANO): 35 p.
Shrimp of the Estuary and Gulf of St. Lawrence. Fisheries and Oceans, Canada
  • L Savard
  • Ms
SAVARD, L. MS 1999. Shrimp of the Estuary and Gulf of St. Lawrence. Fisheries and Oceans, Canada, Science Stock Status Report, C4-06: 12 p.