scholarly journals PRELIMINARY STOCK ASSESSMENT RESULTS FOR SHAD IN AZOV-BLACK SEA BASIN IN TERMS OF DATA LUCKING (2007–2020)

2021 ◽  
Vol 1 (6) ◽  
pp. 34-39
Author(s):  
I.D. Kozobrod ◽  
◽  
M.M. Piatinski
Keyword(s):  
Black Sea ◽  
Stock Assessment ◽  
Safe Zone ◽  
Fishing Mortality ◽  
Stock Status ◽  
Azov Sea ◽  
Stock Biomass ◽  
Stock Recovery ◽  
Assessment Results

Black-azov sea shad Alosa immaculate (Bennett, 1835) stock assessment performed by trending model CMSY in terms of data lucking for period 2007–2020 in R. Model results showed current stock status in biological safe zone (B2020 = 2291 t, BMSY = 1855 t, B2020/BMSY = 1,23) with signs of minor overexploitation by fishing mortality (F2020 = 0,35, FMSY = 0,28, F2020/FMSY = 1,25). Obtained stock biomass estimates shows minor Black-Azov sea shad stock recovery evidence in period 2007–2020. Evidence of light population fishery overexploitation after 2018 are found, perhaps, was caused by IUU-fishery. Paper results underline to eliminate and regulate shad illegal, unreported, unregistered fishery in Azov-Black sea basin

Blue marlin mean length: simulated response to increasing fishing mortality

2003 ◽  
Vol 54 (4) ◽  
pp. 401 ◽  
Author(s):  
C. Phillip Goodyear
Keyword(s):  
Size Distribution ◽  
Stock Assessment ◽  
Size Composition ◽  
Base Case ◽  
Fishing Mortality ◽  
Blue Marlin ◽  
Strong Trend ◽  
Population Simulation ◽  
Assessment Results

Mean length of caught fish often declines noticeably with increased fishing mortality and this trend is regarded as an indicator of excessive fishing mortality. The most recent stock assessment results for Atlantic blue marlins and Atlantic white marlins indicate that these stocks are heavily overfished. However, available data do not suggest a strong trend of decreasing lengths of marlins in the catch. The lack of such a trend has been used to argue that the assessment results are in error. This study uses population simulation to characterize the expected response of the size distribution of blue marlin to the vector of fishing mortality and FMSY estimated for the base case in the most recent stock assessment, and contrasts the results with a similar analysis for Atlantic swordfish. The results indicate that blue marlin should not be expected to exhibit strong trends in mean length with respect to fishing mortality within the range of fishing mortality estimated in the most recent stock assessment, and that the trends in the observed size composition are consistent with the findings of the stock assessment. The findings indicate that declining mean length is not a necessary outcome of excessive fishing mortality in all species.

scholarly journals The current state of the turbot, Scophthalmus maximus (Linnaeus, 1758), population in the northwestern part of the Black Sea

2021 ◽  
Vol 29 (3) ◽  
pp. 164-175
Author(s):  
Bohdan Hulak ◽  
Yevhen Leonchyk ◽  
Volodia Maximov ◽  
George Tiganov ◽  
Vladislav Shlyakhov ◽  
...  
Keyword(s):  
Black Sea ◽  
Stock Assessment ◽  
Scophthalmus Maximus ◽  
The Black Sea ◽  
Northwestern Part ◽  
Fishing Mortality ◽  
Current State ◽  
Turbot Scophthalmus Maximus ◽  
High Level ◽  
Potential Rate

Abstract Turbot is one of the most valuable fish species in the Black Sea commercial fishery. The serious, dramatic depletion of the turbot stock and catches that began in the 1980s was caused by overfishing and poor ecological conditions. The state of the turbot stock began to improve in the northwestern part of the Black Sea in 2016. Landings were at their 30-year maximum in this part of the sea. Catches per unit effort (CPUEs) have been at a stable, high level there for the last few years. Average turbot weight and length have also been increasing. The Stock Synthesis (SS3) framework was used in the stock assessment. According to SS3 analysis, fishing mortality (F) reached the minimum level of 0.29 in 2018. The cumulative SPR (Spawner Potential Rate) index was 0.27, which approximately equaled SPRMSY = 0.25. Thus, currently the turbot stock is mostly moderately exploited at a level close to the management target in the northwestern part of the Black Sea. However, the entire Black Sea population has not fully recovered yet.

DATA LIMITED STOCK ASSESSMENT OF POPULATION DYNAMICS BY CMSY MODEL ON THE EXAMPLE OF BLACK SEA SPRAT IN THE RUSSIAN WATERS

Fisheries ◽  
2021 ◽  
Vol 2021 (3) ◽  
pp. 76-82
Author(s):  
M. Pyatinsky
Keyword(s):  
Black Sea ◽  
Reference Point ◽  
Stock Assessment ◽  
Model Fitting ◽  
Assessment Procedure ◽  
Cohort Model ◽  
Limited Information ◽  
Short Term ◽  
Stock Biomass ◽  
Russian Waters

This study performs approbation of trend CMSY model on the example of Black sea sprat fishing unit, localized in Russian waters. Data sources has been reduced to the level of data limited modeling for indicator and trend models approach. CMSY population model results were compared with previously performed estimations by more powerful cohort model - XSA. CMSY results shows no significant deviations from the XSA results. Forecast scenarios and conclusions based on CMSY model fitting leads to the same statements with previously published results by XSA. CMSY model shows next results: stock biomass in 2019 B2019 = 63,9 ths. t, fishing mortality – F2019 = 0,29. Stock biomass in 2019 was significant below the target reference point BMSY = 105 ths. t and higher then limit reference point Blim = 52,7 ths. t. Some uncertain overexploitation in 2019 was underlined, F2019/FMSY = 1,12. Investigation of forecast scenarios with different total allowed catch levels indicates that there are no features for increasing the catch capacity in short-term projection. CMSY model fitting have passed the necessary stability tests and confirm previously founded results. In summary of this study, we can recommend to use CMSY model for stock assessment procedure in terms of data-limited information background.

scholarly journals Biased stock assessment when using multiple, hardly overlapping, tuning series if fishing trends vary spatially

2009 ◽  
Vol 66 (10) ◽  
pp. 2272-2277 ◽  
Author(s):  
Sarah B. M. Kraak ◽  
Niels Daan ◽  
Martin A. Pastoors
Keyword(s):  
Stock Assessment ◽  
Fishing Effort ◽  
Assessment Procedure ◽  
Moderate Degree ◽  
Fishing Mortality ◽  
Stock Biomass ◽  
Spatial Coverage ◽  
Spawning Stock ◽  
Age Model ◽  
Biased Perception

Abstract Kraak, S. B. M., Daan, N., and Pastoors, M. A. 2009. Biased stock assessment when using multiple, hardly overlapping, tuning series if fishing trends vary spatially. – ICES Journal of Marine Science, 66: 2272–2277. Fishing-effort distributions are subject to change, for autonomous reasons and in response to management regulations. Ignoring such changes in a stock-assessment procedure may lead to a biased perception. We simulated a stock distributed over two regions with inter-regional migration and different trends in exploitation and tested the performance of extended survivors analysis (XSA) and a statistical catch-at-age model in terms of bias, when spatially restricted tuning series were applied. If we used a single tuning index that covered only the more heavily fished region, estimates of fishing mortality and spawning-stock biomass were seriously biased. If two tuning series each exclusively covering one region were used (without overlap but together covering the whole area), estimates were also biased. Surprisingly, a moderate degree of overlap of spatial coverage of the two tuning indices was sufficient to reduce bias of the XSA assessment substantially. However, performance was best when one tuning series covered the entire stock area.

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 STOCK ASSESSMENT AND LONG-TERM DYNAMICS OF AZOV SEA ROACH (RUSSIAN WATERS), BASED ON CMSY MODEL FOR DATA-LIMITED MODELLING IN PERIOD (1999-2019)

Fisheries ◽  
2020 ◽  
Vol 2020 (6) ◽  
pp. 88-94
Author(s):  
Nikolay Zherdev ◽  
M. Pyatinsky ◽  
Inna Kozobrod
Keyword(s):  
River Flow ◽  
Stock Assessment ◽  
Rutilus Rutilus ◽  
Roach Rutilus Rutilus ◽  
Surplus Production ◽  
Azov Sea ◽  
Production Models ◽  
Stock Biomass ◽  
Russian Waters

Stock assessment of Azov sea roach Rutilus rutilus (Linnaeus, 1758) has been performed by CMSY model in period 1999-2019 by data-limited modelling in R. The current population status – in biological safe zone for stock biomass and no overfishing signals (B2019/BMSY = 1,32, F2019/FMSY = 0,53). Perhaps, current paper results can be a slightly incomplete in background that there is no relevant data about IUU fishery ever exists, which can lead to fishing mortality underestimation. Azov sea roach population continue to be in “depleted” status after river flow regulation in 1950’s. Joined continuous biomass estimates time series over whole fishing his-tory 1932–2019 showed at least 2 population collapses: in 1940’s and 1980’s years. According to model re-sults TAC (total allowed catch) should be accepted at level 516.9 t. If the recommendation is followed stock biomass will stay at safety in level 1828.1 t. Data limited modelling shows a good performance for sea roach in background of data lucking and in this reason still the best choose against cohor or surplus production models.

Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

2008 ◽  
Keyword(s):  
Time Series ◽  
Stock Assessment ◽  
Assessment Model ◽  
Current Status ◽  
Total Biomass ◽  
Fishing Mortality ◽  
Research Survey ◽  
Stock Biomass ◽  
Short Time ◽  
Age Range

<em>Abstract.—</em>Catch and research survey data for 1992–2005 on the roughhead grenadier <em>Macrourus berglax </em>stock in the Northwest Atlantic Fisheries Organization (NAFO) Subareas 2 and 3 are fitted using the Extended Survivors Analysis (XSA) model. Despite the short time series available, the wide age range of this species, the low fishing mortality level as estimated by XSA, and the lack of convergence in the retrospective analyses, the results showed that the XSA model provides an adequate fit to the data and the XSA estimated trends are similar to those observed in research surveys. Therefore, we conclude that this assessment model could be an appropriate tool to be used in the quantitative assessment of the roughhead grenadier stock in NAFO Subareas 2 and 3. The model results indicated that the stock biomass has been increasing from 1996 to 2005. The biomass estimated for the beginning of 2005 was around 70,000 metric tons (mt), the highest in the time series. Fishing mortality has declined since 1999 and showed the lowest value in the time series in 2005. However, the retrospective analysis indicated a clear retrospective pattern in the model estimates, with fishing mortality underestimated and total biomass overestimated. Over the last few years, there have been two very good recruitments at age 3, which may lead to an increase of the exploitable biomass in the future. The assessment results showed that the current status of the roughhead grenadier stock in Subareas 2 and 3 is acceptable. The values calculated for the yield per recruit reference points were <EM>F</EM><sub>max</sub> = 0.130 and <EM>F</EM><sub>0.1</sub>= 0.083.

Estimating uncertainty of data limited stock assessments

2016 ◽  
Vol 74 (1) ◽  
pp. 69-77 ◽  
Author(s):  
Alexandros Kokkalis ◽  
Anne Maria Eikeset ◽  
Uffe H. Thygesen ◽  
Petur Steingrund ◽  
Ken H. Andersen
Keyword(s):  
Stock Assessment ◽  
Assessment Method ◽  
Fish Stocks ◽  
Stock Status ◽  
North East ◽  
The North ◽  
Stock Biomass ◽  
Uncertainty Estimates ◽  
Stock Assessments ◽  
Spawning Stock

Many methods exist to assess the fishing status of data-limited stocks; however, little is known about the accuracy or the uncertainty of such assessments. Here we evaluate a new size-based data-limited stock assessment method by applying it to well-assessed, data-rich fish stocks treated as data-limited. Particular emphasis is put on providing uncertainty estimates of the data-limited assessment. We assess four cod stocks in the North-East Atlantic and compare our estimates of stock status (F/Fmsy) with the official assessments. The estimated stock status of all four cod stocks followed the established stock assessments remarkably well and the official assessments fell well within the uncertainty bounds. The estimation of spawning stock biomass followed the same trends as the official assessment, but not the same levels. We conclude that the data-limited assessment method can be used for stock assessment and that the uncertainty estimates are reliable. Further work is needed to quantify the spawning biomass of the stock.

scholarly journals Assessing the Potential of Catch-Only Models to Inform on the State of Global Fisheries and the UN’s SDGs

2021 ◽  
Vol 13 (11) ◽  
pp. 6101
Author(s):  
Rishi Sharma ◽  
Henning Winker ◽  
Polina Levontin ◽  
Laurence Kell ◽  
Dan Ovando ◽  
...  
Keyword(s):  
Stock Assessment ◽  
Fishing Effort ◽  
The State ◽  
Sources Of Information ◽  
Ongoing Research ◽  
Traditional Assessment ◽  
Stock Status ◽  
Stock Assessments ◽  
Recent Developments ◽  
Measure Of Performance

Catch-only models (COMs) have been the focus of ongoing research into data-poor stock assessment methods. Two of the most recent models that are especially promising are (i) CMSY+, the latest refined version of CMSY that has progressed from Catch-MSY, and (ii) SRA+ (Stock Reduction Analysis Plus) a recent developments in field. Comparing COMs and evaluating their relative performance is essential for determining the state of regional and global fisheries that may be lacking necessary data that would be required to run traditional assessment models. In this paper we interrogate how performance of COMs can be improved by incorporating additional sources of information. We evaluate the performance of COMs on a dataset of 48 data-rich ICES (International Council for the Exploration of Seas) stock assessments. As one measure of performance, we consider the ability of the model to correctly classify stock status using FAO’s 3-tier classification that is also used for reporting on sustainable development goals to the UN. Both COMs showed notable bias when run with their inbuilt default heuristics, but as the quality of prior information increased, classification rates for the terminal year improved substantially. We conclude that although further COM refinements show some potential, most promising is the ongoing research into developing biomass or fishing effort priors for COMs in order to be able to reliably track stock status for the majority of the world’s fisheries currently lacking stock assessments.

scholarly journals Depleted marine fish stocks and ecosystem-based management: on the road to recovery, we need to be precautionary

2010 ◽  
Vol 68 (1) ◽  
pp. 212-220 ◽  
Author(s):  
Anna Gårdmark ◽  
Anders Nielsen ◽  
Jens Floeter ◽  
Christian Möllmann
Keyword(s):  
Fisheries Management ◽  
Marine Fish ◽  
Assessment Model ◽  
Fishing Mortality ◽  
Fish Stocks ◽  
The Road ◽  
Stock Status ◽  
Ecosystem Based Management ◽  
Management Plans ◽  
On The Road

Abstract Gårdmark, A., Nielsen, A., Floeter, J., and Möllmann, C. 2011. Depleted marine fish stocks and ecosystem-based management: on the road to recovery, we need to be precautionary. – ICES Journal of Marine Science, 68: 212–220. Precautionary management for fish stocks in need of recovery requires that likely stock increases can be distinguished from model artefacts and that the uncertainty of stock status can be handled. Yet, ICES stock assessments are predominantly deterministic and many EC management plans are designed for deterministic advice. Using the eastern Baltic cod (Gadus morhua) stock as an example, we show how deterministic scientific advice can lead to illusive certainty of a rapid stock recovery and management decisions taken in unawareness of large uncertainties in stock status. By (i) performing sensitivity analyses of key assessment model assumptions, (ii) quantifying the uncertainty of the estimates due to data uncertainty, and (iii) developing alternative stock and ecosystem indicators, we demonstrate that estimates of recent fishing mortality and recruitment of this stock were highly uncertain and show that these uncertainties are crucial when combined with management plans based on fixed reference points of fishing mortality. We therefore call for fisheries management that does not neglect uncertainty. To this end, we outline a four-step approach to handle uncertainty of stock status in advice and management. We argue that it is time to use these four steps towards an ecosystem-based approach to fisheries management.

Sign in / Sign up

Export Citation Format

Share Document