Adaptive Probing Strategies for Age-Structured Fish Stocks

1983 ◽  
Vol 40 (5) ◽  
pp. 559-569 ◽  
Author(s):  
D. Ludwig ◽  
R. Hilborn
Keyword(s):  
Management System ◽  
Optimal Size ◽  
Fishing Mortality ◽  
Fish Stocks ◽  
Surplus Production ◽  
Production Models ◽  
Productive Potential ◽  
Adaptive Probing ◽  
Age Structured ◽  
Stock Abundance

This paper examines methods of preventing a stock of fish from being held far below its optimal size. Such sustained overexploitation could arise because the model used to manage the stock poorly represented the stock dynamics, because there are significant errors in the estimates of stock abundance, or because there is insufficient contrast in catch and fishing mortality to generate reliable estimates of the productive potential of the stock. We develop a method to correct for biases due to errors in estimates of abundance and show that this correction does improve estimates of productivity, but not sufficiently to enable a manager to recognize the presence of overexploitation. We demonstrate that the management system must generate significant contrast in catch and effort, and once the contrast is generated the managers can easily find near optimal abundance of the stock. With reasonable levels of contrast even very simple surplus production models will perform well when managing complex age-structured fish stocks.

scholarly journals Comment on “Impacts of historical warming on marine fisheries production”

Science ◽  
2019 ◽  
Vol 365 (6454) ◽  
pp. eaax5721 ◽  
Author(s):  
Cody Szuwalski
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Maximum Sustainable Yield ◽  
Structured Data ◽  
Sea Surface ◽  
Sustainable Yield ◽  
Surplus Production ◽  
Production Models ◽  
Fitting Production ◽  
Age Structured

Free et al. (Reports, 1 March 2019, p. 979) linked sea surface temperature (SST) to surplus production and estimated a 4% decline in maximum sustainable yield (MSY) since 1930. Changes in MSY are expected when fitting production models to age-structured data, so attributing observed changes to SST is problematic. Analyses of recruitment (a metric of productivity in the same database) showed increases in global productivity.

Influence of Various Sources of Error and Community Interactions on Quota Management of Fish Stocks

1987 ◽  
Vol 44 (S2) ◽  
pp. s61-s67 ◽  
Author(s):  
Joseph F. Koonce ◽  
Brian J. Shuter
Keyword(s):  
Control Systems ◽  
Environmental Variability ◽  
Production Method ◽  
Community Interactions ◽  
Fish Stocks ◽  
Surplus Production ◽  
Production Models ◽  
Western Lake ◽  
Wide Range ◽  
Quota Management

We compare the performance of fishery control systems based on population and surplus production models. We show that the population method is superior to a surplus production method over a wide range of observational and structural error conditions. We also show that adaptive fishery control systems have potential to reduce uncertainty surrounding management of fisheries like the walleye (Stizostedion vitreum vitreum) fishery of western Lake Erie where unknown bias and error in harvest statistics combine with environmental variability to contribute substantial uncertainty to the quota derivation process.

Island in the Stream: Oceanography and Fisheries of the Charleston Bump

2001 ◽  
Keyword(s):  
Mortality Rate ◽  
Yellowfin Tuna ◽  
Production Model ◽  
Fishing Mortality ◽  
Target Species ◽  
Surplus Production ◽  
Blue Marlin ◽  
Production Curve ◽  
Age Structured ◽  
Charleston Bump

<em>Abstract.</em>—Atlantic blue marlin are primarily harvested as bycatch in fisheries targeting tunas and swordfish. These target species are managed for maximum sustainable yield (MSY) based largely on guidance from surplus production models that lack age structure. Simulation models were constructed around the life history characteristics of Atlantic blue marlin and yellowfin tuna, one of the target species. Each simulated population was exposed to fishing mortality and the resulting time streams of catches and abundances were used as surplus production model inputs using the computer program ASPIC. The slopes of the stock-recruitment curves of the simulated populations were adjusted until the ASPIC estimates of the intrinsic growth rates for the simulations were equivalent to the estimates derived for these populations in the last ICCAT stock assessments. The equilibrium curves of production on fishing mortality for the age-structured populations were then compared to the logistic production model fitted by ASPIC. For blue marlin, the underlying production curve shifted to the left, and F<SUB> MSY </SUB>was lower than the value estimated by ASPIC. For yellowfin tuna, the underlying production curve shifted to the right and F<SUB> MSY </SUB>occurred at a higher fishing mortality rate than that estimated by ASPIC. These results suggest that the Atlantic blue marlin stock is more vulnerable to fishing mortality than indicated by the production model fitted in the last assessment. Also, the fishing mortality rate that produces MSY for yellowfin is near the extinction level for blue marlin. This characteristic is likely shared by other highly productive stocks that support the fisheries in which blue marlin are killed as bycatch. These results indicate that fishing target species at MSY may result in continued serious depletions of Atlantic blue marlin unless the catchability can be reduced relative to the catchability of the target species.

scholarly journals Endogenous fishing mortalities: a state-space bioeconomic model

2017 ◽  
Vol 74 (9) ◽  
pp. 2437-2447 ◽  
Author(s):  
José-María Da-Rocha ◽  
Javier García-Cutrín ◽  
María-José Gutiérrez ◽  
Ernesto Jardim
Keyword(s):  
Total Mortality ◽  
Fishing Effort ◽  
Bioeconomic Model ◽  
Fishing Mortality ◽  
Northern Spain ◽  
Management Regime ◽  
Target Management ◽  
Age Structured ◽  
Age Structured Model ◽  
Stock Abundance

Abstract A methodology that endogenously determines catchability functions that link fishing mortality with contemporaneous stock abundance is presented. We consider a stochastic age-structured model for a fishery composed by a number of fishing units (fleets, vessels or métiers) that optimally select the level of fishing effort to be applied considering total mortalities as given. The introduction of a balance constrain which guarantees that total mortality is equal to the sum of individual fishing mortalities optimally selected, enables total fishing mortality to be determined as a combination of contemporaneous abundance and stochastic processes affecting the fishery. In this way, future abundance can be projected as a dynamic system that depends on contemporaneous abundance. The model is generic and can be applied to several issues of fisheries management. In particular, we illustrate how to apply the methodology to assess the floating band target management regime for controlling fishing mortalities which is inspired in the new multi-annual plans. Our results support this management regime for the Mediterranean demersal fishery in Northern Spain.

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.

Estimating Fmsy from an ensemble of data sources to account for density dependence in Northeast Atlantic fish stocks

2020 ◽  
Author(s):  
Henrik Sparholt ◽  
Bjarte Bogstad ◽  
Villy Christensen ◽  
Jeremy Collie ◽  
Rob van Gemert ◽  
...  
Keyword(s):  
Maximum Sustainable Yield ◽  
Data Sources ◽  
Fishing Pressure ◽  
Fish Stocks ◽  
Northeast Atlantic ◽  
Density Dependent ◽  
Production Models ◽  
Pool Model ◽  
Age Structured ◽  
The 1960S

Abstract A new approach for estimating the fishing mortality benchmark Fmsy (fishing pressure that corresponds to maximum sustainable yield) is proposed. The approach includes density-dependent factors. The analysis considers 53 data-rich fish stocks in the Northeast Atlantic. The new Fmsy values are estimated from an ensemble of data sources: (i) applying traditional surplus production models on time-series of historic stock sizes, fishing mortalities, and catches from the current annual assessments; (ii) dynamic pool model (e.g. age-structured models) estimation for stocks where data on density-dependent growth, maturity, and mortality are available; (iii) extracts from multispecies and ecosystem literature for stocks where well-tested estimates are available; (iv) the “Great Experiment” where fishing pressure on the demersal stocks in the Northeast Atlantic slowly increased for half a century; and (v) linking Fmsy to life history parameters. The new Fmsy values are substantially higher (average equal to 0.38 year−1) than the current Fmsy values (average equal to 0.26 year−1) estimated in stock assessments and used by management, similar to the fishing pressure in the 1960s, and about 30% lower than the fishing pressure in 1970–2000.

Equilibrium Yields and Yield Isopleths from a General Age-Structured Model of Harvested Populations

1985 ◽  
Vol 42 (11) ◽  
pp. 1766-1771 ◽  
Author(s):  
Timothy A. Lawson ◽  
Ray Hilborn
Keyword(s):  
Structured Model ◽  
Surplus Production ◽  
Pacific Halibut ◽  
Production Models ◽  
The Pacific ◽  
Hippoglossus Stenolepis ◽  
Equilibrium Yield ◽  
Stock Recruitment ◽  
Age Structured ◽  
Age Structured Model

The equilibrium properties of an age-structured model that includes any arbitrary age-specific weights, vulnerabilities, fecundities, and natural mortality rates, combined with stock–recruitment relationships, are derived. The numbers, biomass, and catch at each age can be calculated quite simply. These relationships can be used to construct yield-isopleth diagrams, or to plot equilibrium yield and biomass against harvest intensity. We used the results to compute yield isopleths for the Pacific halibut (Hippoglossus stenolepis) fishery. The analysis can also include a fishing season of any specified length. Relationships are given to translate the aggregate properties of the age-structured models into several alternative surplus production models.

scholarly journals Understanding the Dynamics of Ancillary Pelagic Species in the Adriatic Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Silvia Angelini ◽  
Enrico N. Armelloni ◽  
Ilaria Costantini ◽  
Andrea De Felice ◽  
Igor Isajlović ◽  
...  
Keyword(s):  
Adriatic Sea ◽  
Production Model ◽  
Horse Mackerel ◽  
Surplus Production ◽  
Robust Model ◽  
Production Models ◽  
The Status ◽  
History Of ◽  
Age Structured ◽  
Fish And Shellfish

The status of fishery resources in the Mediterranean Sea is critical: most of the fish and shellfish stocks are in overexploitation and only half of them are routinely assessed. This manuscript presents the use of Surplus Production Models (SPMs) as a valid option to increase the number of assessed stocks, with specific attention to the Adriatic basin. Particularly, the stock of European sprat (Sprattus sprattus), Mediterranean horse mackerel (Trachurus mediterraneus), and Atlantic horse mackerel (Trachurus trachurus) living in the Adriatic Sea have been evaluated comparing three SPMs: Catch Maximum Sustainable Yields (CMSY), Stochastic surplus Production model in Continuous Time (SPiCT), and Abundance Maximum Sustainable Yields (AMSY). The different approaches present some variations; however, they generally agree on describing all the stocks close to the reference values for both biomass and fishing mortality in the most recent year. For the European sprat, AMSY results are the most robust model for this species’ survey data allow depicting a clearer picture of the history of this stock. Indeed, for the horse mackerel species, CMSY or SPiCT results are the preferred models, since for these species landings are not negligible. Notwithstanding, age-structured assessments remain the most powerful approach for evaluating the status of resources, but SPMs have proved to be a powerful tool in a data-limited context.

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.

scholarly journals Stock assessment and projections incorporating discard estimates in some years: an application to the hake stock in ICES Divisions VIIIc and IXa

2010 ◽  
Vol 67 (6) ◽  
pp. 1185-1197 ◽  
Author(s):  
C. Fernández ◽  
S. Cerviño ◽  
N. Pérez ◽  
E. Jardim
Keyword(s):  
Time Series ◽  
Stock Assessment ◽  
Reference Points ◽  
Assessment Model ◽  
Marine Science ◽  
Fishing Mortality ◽  
Change Over Time ◽  
Age Structured ◽  
Available Information ◽  
Over Time

Abstract Fernández, C., Cerviño, S., Pérez, N., and Jardim, E. 2010. Stock assessment and projections incorporating discard estimates in some years: an application to the hake stock in ICES Divisions VIIIc and IXa. – ICES Journal of Marine Science, 67: 1185–1197. A Bayesian age-structured stock assessment model is developed to take into account available information on discards and to handle gaps in the time-series of discard estimates. The model incorporates mortality attributable to discarding, and appropriate assumptions about how this mortality may change over time are made. The result is a stock assessment that accounts for information on discards while, at the same time, producing a complete time-series of discard estimates. The method is applied to the hake stock in ICES Divisions VIIIc and IXa, for which the available data indicate that some 60% of the individuals caught are discarded. The stock is fished by Spain and Portugal, and for each country, there are discard estimates for recent years only. Moreover, the years for which Portuguese estimates are available are only a subset of those with Spanish estimates. Two runs of the model are performed; one assuming zero discards and another incorporating discards. When discards are incorporated, estimated recruitment and fishing mortality for young (discarded) ages increase, resulting in lower values of the biological reference points Fmax and F0.1 and, generally, more optimistic future stock trajectories under F-reduction scenarios.

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