scholarly journals Evolution of the state of fish stocks in the Northeast Atlantic within a precautionary framework, 1970–2003: a synoptic evaluation

2005 ◽  
Vol 62 (8) ◽  
pp. 1603-1608 ◽  
Author(s):  
S.M. Garcia ◽  
J.I. De Leiva Moreno
Keyword(s):  
Time Lag ◽  
The State ◽  
Reference Points ◽  
Fishing Mortality ◽  
Fish Stocks ◽  
The North ◽  
Value Judgements ◽  
The Status ◽  
The Mean ◽  
Spawning Biomass

Abstract The state and trajectory of some of the stocks assessed by ICES in the North Atlantic in the period 1970–2003 are synoptically represented on a single system of representation of fishing mortality and biomass with precautionary reference points used as limits and thresholds. The results indicate that for nearly 30 years, the status of the stocks in relation to the precautionary reference points has been degrading in terms of spawning biomass and excess fishing mortality, driving most resources down close to and often beyond those reference points. The situation seems to have improved during the past decade, with some exceptions, as shown by progressive shift of the mean position of the stocks away from excessive mortality (since the early 1990s) and, after a time-lag, away from low biomass (since the early 2000s). The proposed representation system sticks to the reference points and value judgements used in the ICES context, but could be used with any equivalent precautionary system of representation.

An Alternative Perspective on Recruitment Overfishing and Biological Reference Points

1987 ◽  
Vol 44 (4) ◽  
pp. 913-918 ◽  
Author(s):  
M. P. Sissenwine ◽  
J. G. Shepherd
Keyword(s):  
Fisheries Management ◽  
Reference Point ◽  
Reference Points ◽  
Fishing Mortality ◽  
Alternative Perspective ◽  
Conventional Models ◽  
Definition Of ◽  
Yield Per Recruit ◽  
Spawning Biomass

Biological reference points are used to guide fisheries management decisions. The reference points most often used are expressed in terms of fishing mortality rate (F). Fmsy relates to the maximization of sustainable yield. In principle, it is a most useful reference point, but in practice it is difficult to estimate. Fmax and F0.1 relate to certain levels of yield per recruit and are easily estimated, but they ignore conservation of the resource. Recruitment overfishing has usually been understood to occur when a population has been fished down to a point where recruitment is substantially reduced or fails. It has not been used as a basis for a biological reference point because the definition is vague and cannot be readily related to fishing mortality. Levels of spawning biomass below which recruitment seems to be reduced have been used, but their determination from available data is usually difficult and controversial. We propose an alternative definition of recruitment overfishing in terms of the level of fishing pressure that reduces the spawning biomass of a year class over its lifetime below the spawning biomass of its parents on average. Conventional models and types of data can be used to determine this level of F, denoted as Frep, which clearly relates to the replacement of spawning biomass and thus to sustainability of a population and yield in the long term.

An assessment of the role of the North Atlantic as a CO 2 sink

1995 ◽  
Vol 348 (1324) ◽  
pp. 143-152 ◽  
Keyword(s):  
North Atlantic ◽  
Surface Waters ◽  
Time Lag ◽  
Gas Transfer ◽  
Advective Transport ◽  
Transfer Coefficients ◽  
The North ◽  
The Mean ◽  
The North Atlantic ◽  
Secular Increase

A numerical interpolation scheme based upon the lateral diffusive and advective transport of ocean surface waters has been developed to interpolate measurements made in irregular time and space over the oceans. This has been applied to about 2700 surface ocean P CO 2 measurements observed during the period 1972-1992 in the North Atlantic to give the distribution of sea-air P CO 2 difference (Δ P CO 2 ) over the Atlantic. Although the atmospheric CO 2 concentration has increased by about 28 ppm over this period, the P CO 2 values in the surface waters of subarctic regions have increased little because they are dictated primarily by the properties of underlying deep waters through vertical mixing. Accordingly, Δ P CO 2 values measured north of 50° N have been corrected to the year 1990 using the secular increase of atmospheric CO 2 . Because the surface water P CO 2 value in temperate waters tracks the secular increase in atmospheric CO 2 with a time lag of about two years, no correction was applied to the warm water Δ p CO 2 data. It has been assumed that seasonal variations are the same for each year. The net CO2 flux across the sea surface has been computed over a 4° latitude x 5° longitude grid using the mean monthly A p CO 2 values and the gas transfer coefficients estimated using the mean monthly wind speed. It has been found that the areas of the high latitude North Atlantic and the adjacent seas north of 42° N are net CO 2 sinks of 0.2 to 0.5 Gt G a -1 . The total sink flux of CO 2 over the temperate North Atlantic areas between 18° N and 42° N is balanced approximately by the source flux over the tropical Atlantic between 18° N and 18° S.

scholarly journals Actual status of fishing reserves of the Yesil River

2019 ◽  
Vol 36 ◽  
pp. 1-9
Author(s):  
Zhumagazy Kurzhykayev ◽  
Kuanysh Syzdykov ◽  
Ainur Assylbekova ◽  
Dinara Sabdinova ◽  
Viktor Fefelov
Keyword(s):  
Biological Diversity ◽  
Biological Indicators ◽  
The State ◽  
Reference Points ◽  
Boundary Values ◽  
Sustainable Fisheries ◽  
Fish Stocks ◽  
Fish Resources ◽  
Managerial Decisions ◽  
Careful Management

In this article, the study and prediction of the state of fish resources in the Yesil River was carried out to determine the boundary reference points of the reserve and management decisions in case they are exceeded, to ensure sustainable fisheries and preserve biological diversity. Ichthyological studies, retrospective analyses and rankings of the effects of the water supply of the Yesil River on fish stocks have been carried out, critical values ​​of the biomass of fishing reserves have been determined, as criteria for biologically safe fishing values and targets for management of fish stocks at reaching the boundary values ​​of 24.03 tonnes have been established. According to the results of studies of basic biological indicators, it was determined that roach, bream, pike and perch populations each had an LC50 above LM50, which indicates their low utilization in the fishery industry. A strategy for management of fish stocks, recommendations for the conservation of fishery resources and their rational use has been developed as a result of these findings. The list and status of the monitored indicators for the careful management of fish stocks, as well as a list and indicators of the boundary indicators for the state of fish stocks, was established. These parameters included the fish size of 50% of the sampled fish and 50% of maturity achieved, where the LC50 was observed in the fish in question from 19 to 45.4 cm and LM50 from 12.3 to 41 cm, respectively. The minimum and maximum river levels that ranged from 111 up to 159 cm, as well as the critical value of the commercial reserve, corresponded to the boundary value of 24.03 tonnes. The results of this work will serve as the basis for making future managerial decisions, necessary for sustainable fisheries and conservation of the biological diversity of the Yesil River.

scholarly journals Indicator-based status assessment of commercial fish species in the North Sea according to the EU Marine Strategy Framework Directive (MSFD)

2013 ◽  
Vol 70 (3) ◽  
pp. 694-706 ◽  
Author(s):  
Wolfgang Nikolaus Probst ◽  
Matthias Kloppmann ◽  
Gerd Kraus
Keyword(s):  
North Sea ◽  
Fish Species ◽  
Marine Strategy Framework Directive ◽  
Commercial Fish ◽  
Fish Stocks ◽  
The North ◽  
The Status ◽  
Status Assessment ◽  
The North Sea ◽  
The Eu

Abstract Probst, W. N., Kloppmann, M., and Kraus, G. Indicator-based status assessment of commercial fish species in the North Sea according to the EU Marine Strategy Framework Directive (MSFD). – ICES Journal of Marine Science, 70: 694–706. The EU Marine Strategy Framework Directive (MSFD) is structured into eleven descriptors of good environmental status (GES). For each descriptor the current status of the marine environment should be assessed against its GES using ecosystem criteria and indicators. Within Descriptor 3 (D3) the MSFD addresses the status of exploited fish stocks according to three criteria (exploitation rate, stock size and size structure). This study performed an MSFD-compliant assessment of exploited fish stocks in the North Sea by aggregating data from analytical stock assessments and scientific research surveys to calculate indicator metrics for each criterion within each stock time-series. A stock achieved GES, when each indicator for each criterion had a good status. Of 43 assessed fish stock suggested by the EU Data Collection Framework, 63% (27) achieved GES. Though the MSFD explicitly demands that all exploited fish stocks achieve GES, this demand may be challenged by reality, because the status of exploited stocks depends not only on fishing impacts, but also on environmental conditions and ecological interactions. Therefore an alternative approach based on binomial distributions is presented to define limits for GES at the descriptor level. The implications and pitfalls of the applied assessment methods are discussed.

Comparative performance of data-poor CMSY and data-moderate SPiCT stock assessment methods when applied to data-rich, real-world stocks

2020 ◽  
Author(s):  
Paul Bouch ◽  
Cóilín Minto ◽  
Dave G Reid
Keyword(s):  
Stock Assessment ◽  
Assessment Methods ◽  
Production Model ◽  
Fishing Mortality ◽  
Comparative Performance ◽  
Fish Stocks ◽  
Surplus Production ◽  
Stock Biomass ◽  
Surplus Production Model ◽  
The Status

Abstract All fish stocks should be managed sustainably, yet for the majority of stocks, data are often limited and different stock assessment methods are required. Two popular and widely used methods are Catch-MSY (CMSY) and Surplus Production Model in Continuous Time (SPiCT). We apply these methods to 17 data-rich stocks and compare the status estimates to the accepted International Council for the Exploration of the Sea (ICES) age-based assessments. Comparison statistics and receiver operator analysis showed that both methods often differed considerably from the ICES assessment, with CMSY showing a tendency to overestimate relative fishing mortality and underestimate relative stock biomass, whilst SPiCT showed the opposite. CMSY assessments were poor when the default depletion prior ranges differed from the ICES assessments, particularly towards the end of the time series, where some stocks showed signs of recovery. SPiCT assessments showed better correlation with the ICES assessment but often failed to correctly estimate the scale of either F/FMSY of B/BMSY, with the indices lacking the contrast to be informative about catchability and either the intrinsic growth rate or carrying capacity. Results highlight the importance of understanding model tendencies relative to data-rich approaches and warrant caution when adopting these models.

scholarly journals The effective reproductive number (Rt) of COVID-19 and its relationship with social distancing

2020 ◽  
Author(s):  
José Alexandre Felizola Diniz-Filho ◽  
Lucas Jardim ◽  
Cristiana M. Toscano ◽  
Thiago Fernando Rangel
Keyword(s):  
Time Lag ◽  
Critical Issue ◽  
The State ◽  
Mobile Phone Data ◽  
Reproductive Number ◽  
Epidemiological Models ◽  
Social Distancing ◽  
Isolation Index ◽  
The Mean ◽  
The Relationship

AbstractThe expansion of the new coronavirus disease (COVID-19) triggered a renewed interest in epidemiological models and on how parameters can be estimated from observed data. Here we investigated the relationship between average number of transmissions though time, the reproductive number Rt, and social distancing index as reported by mobile phone data service inloco, for Goiás State, Brazil, between March and June 2020. We calculated Rt values using EpiEstim package in R-plataform for confirmed cases incidence curve. We found a correlation equal to -0.72 between Rt values and isolation index at a time lag of 8 days. This correlation is also significant for half of the cities of the State with more than 90,000 people, including the 3 largest ones (and the 7 cities with significant correlations account for 43% of the population of the State). As the Rt values were paired with center of the moving window of 7 days, the delay matches the mean incubation period of the virus. Our findings reinforce that isolation index can be an effective surrogate for modeling and epidemiological analyses and, more importantly, helpful for anticipating the need for early interventions, a critical issue in public health.

scholarly journals A meta-analysis of the status of ICES fish stocks during the past half century

2007 ◽  
Vol 64 (4) ◽  
pp. 707-713 ◽  
Author(s):  
Henrik Sparholt ◽  
Mette Bertelsen ◽  
Hans Lassen
Keyword(s):  
Time Series ◽  
Meta Analysis ◽  
Fishing Mortality ◽  
Fish Stocks ◽  
Half Century ◽  
The Past ◽  
Past Half Century ◽  
The Status ◽  
1960S And 1970S ◽  
Past Half

Abstract Sparholt, H., Bertelsen, M., and Lassen, H. 2007. A meta-analysis of the status of ICES fish stocks during the past half century. – ICES Journal of Marine Science, 64: 707–713. Based on a meta-analysis of time-series of stock size, recruitment, and fishing mortality, the general status of fish stocks within the ICES Area (i.e. the Northeast Atlantic) is evaluated. The analysis is based on data for 34 (7 pelagic, 27 demersal) commercial stocks. The stocks were selected based on the quality of the data and the length of the time-series. The analysis indicates that most pelagic stocks recovered to sustainable levels with high productivity after several had collapsed in the 1960s and 1970s. In contrast, most demersal stocks have continued to decline over the past half century and are now recruitment-overfished. By reducing fishing mortality on demersal stocks on average by half and building up the stocks by a factor of about two, management could be brought in line with international agreements. If recruitment-overfishing is avoided for all demersal stocks and discarding is minimized, their yield might be almost doubled over the current yield. Among the major management initiatives during the past half century, only the closure of the pelagic fisheries in the mid-1970s can be clearly identified in the time-series as having had a direct effect on stock status.

scholarly journals Current status and temporal trends in stocks of European eel in England and Wales

2007 ◽  
Vol 64 (7) ◽  
pp. 1368-1378 ◽  
Author(s):  
A. Bark ◽  
B. Williams ◽  
B. Knights
Keyword(s):  
Temporal Trends ◽  
Model Development ◽  
Standing Stock ◽  
Reference Points ◽  
Current Status ◽  
European Eel ◽  
England And Wales ◽  
The Status ◽  
The Mean ◽  
Electric Fishing

Abstract Bark, A., Williams, B., and Knights, B. 2007. Current status and temporal trends in stocks of European eel in England and Wales. – ICES Journal of Marine Science, 64: –. An extensive 4-year programme of catchment surveys, data collection, and model development for eels was undertaken to establish the status of the stocks in England and Wales, so that appropriate management action can be taken. Nine test catchments representing different geographical areas and catchment types were studied, covering 14 rivers, two estuaries, and a fresh-water lagoon. Data were collected via electric fishing, fykenetting, fixed eel racks, and elver traps. In all, 13 500 eels were caught, weighed, and measured, and the sex and age of a subsample of 1400 determined. Despite declining recruitment, eel stocks in some, perhaps many, west coast rivers are probably still at or near to carrying capacity, with male-dominated populations. In other rivers, particularly those towards the southeast of England, current and historical data indicate declining female-dominated stocks. For rivers where recruitment is not limiting, there appears to be a direct relationship between the standing stock of eels and the mean nitrate level. This relationship potentially facilitates the application of a biomass-based biological reference point for eels for application to individual catchments. The data also suggest that it may be possible to develop reference points based on mean eel length or sex ratio.

scholarly journals Performance of precautionary reference points in providing management advice on North Sea fish stocks

2004 ◽  
Vol 61 (8) ◽  
pp. 1305-1312 ◽  
Author(s):  
G.J. Piet ◽  
J.C. Rice
Keyword(s):  
North Sea ◽  
Status Quo ◽  
Reference Points ◽  
Reference Level ◽  
False Alarms ◽  
Commercial Fish ◽  
Fish Stocks ◽  
The North ◽  
Management Advice ◽  
Sea Fish

Abstract For 17 stocks in the North Sea, the performance and effectiveness of management advice using precautionary reference points was evaluated. Three criteria were used to identify whether a stock was within safe biological limits: SSB < Bpa, F > Fpa, or SSB < Bpa and F > Fpa. Four scenarios were considered, comparing the advice in the assessment year with what is retrospectively (2002 assessment) known to be the status of the stock at that time: (1) stock outside safe biological limits, advice to reduce fishing; (2) stock outside safe biological limits, advice for status quo harvesting; (3) stock within safe biological limits, advice to reduce fishing; and (4) stock within safe biological limits, advice for status quo (or increased) harvesting. Signal Detection Theory was applied to these scenarios, and the proportion of Hits (1 and 4), Misses (2), and False Alarms (3) were determined for each year as the proportion of the stocks for which the respective scenarios applied. Using both Bpa and Fpa was deemed the approach with the lowest error rate, and it resulted in about the same proportion of Hits in management advice as when Bpa alone was used (62%), but the proportion of Misses was slightly lower (24% vs. 26%). Therefore, the suggested EcoQ element would be the proportion of commercial fish stocks within safe biological limits (i.e. SSB > Bpa, F < Fpa), and the Ecological Quality Objective (EcoQO) should be that this EcoQ should be at or above a desired level. This desired level is a societal/political decision relative to the EcoQ reference level (i.e. where the anthropogenic influence on the ecological system is minimal), which by definition is 100%. At present, probably <10% of North Sea fish stocks are within safe biological limits, despite the relatively high Hit rate of >60%. A possible explanation is that most of these stocks (e.g. flatfish and roundfish) are caught in a mixed fishery, for which TAC management is less effective.

scholarly journals Evaluation of the exploitation of Eastern Baltic cod (Gadus morhua callarias L.) stock in 1976–1997

2003 ◽  
Vol 60 (5) ◽  
pp. 1114-1122 ◽  
Author(s):  
Krzysztof Radtke
Keyword(s):  
Gadus Morhua ◽  
Management Strategies ◽  
Mortality Rates ◽  
Reference Points ◽  
Fishing Mortality ◽  
Safe Level ◽  
Stock Biomass ◽  
Spawning Biomass ◽  
Eastern Baltic ◽  
Baltic Cod

Abstract Big changes occurred in the Eastern Baltic cod biomass and catches in the 1976–1997 period. At present, the Eastern Baltic cod stock spawning biomass (SSB) and catches are approximately five times lower than their highest ever recorded levels observed in the middle of the 1980s. The reasons for the stock decline, namely low recruitment and high fishing mortality, are widely known and well described in the literature. Throughout the whole period, the International Council for the Exploration of the Sea (ICES) made scientific recommendations regarding the exploitation level of the cod stock. The ICES presented and analysed different management strategies based on fishing mortalities which corresponded to biological reference points (BRP) and also recommended total allowable catches (TACs) for cod, taking into account the sustainability of cod resources. In fact, in most years the TAC established by the International Baltic Sea Fisheries Commission (IBSFC) and cod catches (observed exploitation) exceeded the ICES-recommended TAC and thus their scientific advice was neither taken into account by the IBSFC nor by fishermen. This paper evaluates: (1) the would-be state of the Eastern Baltic cod stock if it had been exploited according to ICES-recommended TAC levels, as compared with observed stock exploitation; and (2) the potential effects of management using fishing mortality rates which correspond to BRP on SSB estimates and catch levels, as compared with observed stock exploitation. It is concluded that if ICES advice had been followed, the cumulative cod catches in the 1976–1997 period would have been the same as those observed, but the stock biomass would have been much higher and at a safe level (SSB above 240 000 t). Furthermore, from the comparative analysis of different management strategies based on BRP and the observed strategy, it appears that other management strategies could have been applied which would have produced a higher biomass and greater cumulative catch numbers than those observed.

Sign in / Sign up

Export Citation Format

Share Document