scholarly journals Quantifying uncertainty and dynamical changes in multi‐species fishing mortality rates, catches and biomass by combining state‐space and size‐based multi‐species models

2021 ◽  
Author(s):  
Michael A. Spence ◽  
Robert B. Thorpe ◽  
Paul G. Blackwell ◽  
Finlay Scott ◽  
Richard Southwell ◽  
...  
Keyword(s):  
State Space ◽  
Mortality Rates ◽  
Fishing Mortality ◽  
Quantifying Uncertainty

A Bayesian state–space mark–recapture model to estimate exploitation rates in mixed-stock fisheries

2006 ◽  
Vol 63 (2) ◽  
pp. 321-334 ◽  
Author(s):  
Catherine G.J Michielsens ◽  
Murdoch K McAllister ◽  
Sakari Kuikka ◽  
Tapani Pakarinen ◽  
Lars Karlsson ◽  
...  
Keyword(s):  
State Space ◽  
Expert Knowledge ◽  
Mortality Rates ◽  
Fishing Effort ◽  
Model Parameters ◽  
Fishing Mortality ◽  
Mark Recapture ◽  
Observation Process ◽  
Mixed Stock ◽  
Reporting Rates

A Bayesian state–space mark–recapture model is developed to estimate the exploitation rates of fish stocks caught in mixed-stock fisheries. Expert knowledge and published results on biological parameters, reporting rates of tags and other key parameters, are incorporated into the mark–recapture analysis through elaborations in model structure and the use of informative prior probability distributions for model parameters. Information on related stocks is incorporated through the use of hierarchical structures and parameters that represent differences between the stock in question and related stocks. Fishing mortality rates are modelled using fishing effort data as covariates. A state–space formulation is adopted to account for uncertainties in system dynamics and the observation process. The methodology is applied to wild Atlantic salmon (Salmo salar) stocks from rivers located in the northeastern Baltic Sea that are exploited by a sequence of mixed- and single-stock fisheries. Estimated fishing mortality rates for wild salmon are influenced by prior knowledge about tag reporting rates and salmon biology and, to a limited extent, by prior assumptions about exploitation rates.

scholarly journals Estimating walleye (Sander vitreus) movement and fishing mortality using state-space models: implications for management of spatially structured populations

2016 ◽  
Vol 73 (3) ◽  
pp. 330-348 ◽  
Author(s):  
Seth J. Herbst ◽  
Bryan S. Stevens ◽  
Daniel B. Hayes ◽  
Patrick A. Hanchin
Keyword(s):  
State Space ◽  
Behavioral Ecology ◽  
Site Fidelity ◽  
State Space Model ◽  
Model Fitting ◽  
Mortality Rates ◽  
Structured Populations ◽  
Sander Vitreus ◽  
Fishing Mortality ◽  
Spawning Site

Fish often exhibit complex movement patterns, and quantification of these patterns is critical for understanding many facets of fisheries ecology and management. In this study, we estimated movement and fishing mortality rates for exploited walleye (Sander vitreus) populations in a lake-chain system in northern Michigan. We developed a state-space model to estimate lake-specific movement and fishery parameters and fit models to observed angler tag return data using Bayesian estimation and inference procedures. Informative prior distributions for lake-specific spawning-site fidelity, fishing mortality, and system-wide tag reporting rates were developed using auxiliary data to aid model-fitting. Our results indicated that postspawn movement among lakes was asymmetrical and ranged from approximately 1% to 42% per year, with the largest outmigration occurring from the Black River, which was primarily used by adult fish during the spawning season. Instantaneous fishing mortality rates differed among lakes and ranged from 0.16 to 0.27, with the highest rate coming from one of the smaller and uppermost lakes in the system. The approach developed provides a flexible framework that incorporates seasonal behavioral ecology (i.e., spawning-site fidelity) in estimation of movement for a mobile fish species that will ultimately provide information to aid research and management for spatially structured fish populations.

scholarly journals An integrated tagging model to estimate mortality rates of Albemarle Sound – Roanoke River striped bass

2017 ◽  
Vol 74 (7) ◽  
pp. 1061-1076 ◽  
Author(s):  
Julianne E. Harris ◽  
Joseph E. Hightower
Keyword(s):  
Striped Bass ◽  
Stock Assessment ◽  
Mortality Rates ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Albemarle Sound ◽  
High Reward ◽  
Accuracy And Precision ◽  
Summer Mortality ◽  
Roanoke River

We developed an integrated tagging model to estimate mortality rates and run sizes of Albemarle Sound – Roanoke River striped bass (Morone saxatilis), including (i) a multistate component for telemetered fish with a high reward external tag; (ii) tag return components for fish with a low reward external or PIT tag; and (iii) catch-at-age data. Total annual instantaneous mortality was 1.08 for resident (458–899 mm total length, TL) and 0.45 for anadromous (≥900 mm TL) individuals. Annual instantaneous natural mortality was higher for resident (0.70) than for anadromous (0.21) fish due to high summer mortality in Albemarle Sound. Natural mortality for residents was substantially higher than currently assumed for stock assessment. Monthly fishing mortality from multiple sectors (including catch-and-release) corresponded to seasonal periods of legal harvest. Run size estimates were 499 000–715 000. Results and simulation suggest increasing sample size for the multistate component increases accuracy and precision of annual estimates and low reward tags are valuable for estimating monthly fishing mortality rates among sectors. Our results suggest that integrated tagging models can produce seasonal and annual mortality estimates needed for stock assessment and management.

scholarly journals Optimal fishing mortality assignment for southern hake Merluccius australis in Chile

2020 ◽  
Vol 48 (4) ◽  
pp. 613-625
Author(s):  
Felipe Lopez ◽  
Jorge Jimenez ◽  
Cristian Canales
Keyword(s):  
Mortality Rate ◽  
Economic Benefit ◽  
Mortality Rates ◽  
Fish Population ◽  
Fishing Effort ◽  
Economic Benefits ◽  
Historical Background ◽  
Total Catch ◽  
Fishing Mortality ◽  
Objective Functions

Since 1979, southern hake (Merluccius australis) has been exploited in Chile from the Bio Bio to the Magallanes regions, between the parallels 41°28.6'S and 57°S. There is evidence of a constant fishing effort and a sustained reduction of the fish population, consistent with a progressive decrease in total annual catches. Management strategies based on the maximum sustainable yield (MSY) and quota assignment/ distribution criteria have not been able to sustain acceptable biomass levels. A non-linear optimization model with two objective functions was proposed to determine an optimal total catch quota for more sustainable exploitation of this fishery. The first function maximizes the total catch over time in response to an optimal assignment of fishing mortality rates per fleet; the second function maximizes the total economic benefit associated with the total catch. The dynamics of the fish population were represented with the equations of a predictive age-structured model. Decision variables were fishing mortality rates and annual catch quotas per fleet, subject to constraints that guarantee a minimum level of biomass escape over a long-term period. The input parameters were obtained from the last stock evaluation report carried out by the Instituto de Fomento Pesquero (IFOP) of Chile. The historical background data of the fishery and the regulatory framework were relevant aspects of the methodology. Five scenarios were evaluated with the two objective functions, including a base scenario, which considered the referential mortality rate as input data as the average mortality rate per fleet from 2007 to 2012. Total economic benefits fluctuate between 102 and USD 442 million for total catches in the range of 108 to 421 thousand tons, which were obtained from maximizing the economic and biological objective functions. Economic benefit/catch ratios were reduced for scenarios with higher constraints on catch limits, and they were more efficient from a biological point of view. Situations with lighter constraints showed in general higher economic benefits and better performance ratios than those with stronger restrictions. The use of optimization models may provide a useful tool to evaluate the effect of regulations for adequate conservation and economical utilization of a limited resource.

scholarly journals North Sea cod recovery?

2006 ◽  
Vol 63 (6) ◽  
pp. 961-968 ◽  
Author(s):  
Joe Horwood ◽  
Carl O'Brien ◽  
Chris Darby
Keyword(s):  
North Sea ◽  
Gadus Morhua ◽  
Mortality Rates ◽  
Fishing Effort ◽  
Current Status ◽  
Fishing Mortality ◽  
Commercial Fish ◽  
Fish Stocks ◽  
Stock Assessments ◽  
Low Levels

AbstractRecovery of depleted marine, demersal, commercial fish stocks has proved elusive worldwide. As yet, just a few shared or highly migratory stocks have been restored. Here we review the current status of the depleted North Sea cod (Gadus morhua), the scientific advice to managers, and the recovery measures in place. Monitoring the progress of North Sea cod recovery is now hampered by considerable uncertainties in stock assessments associated with low stock size, variable survey indices, and inaccurate catch data. In addition, questions arise as to whether recovery targets are achievable in a changing natural environment. We show that current targets are achievable with fishing mortality rates that are compatible with international agreements even if recruitment levels remain at the current low levels. Furthermore, recent collations of data on international fishing effort have allowed estimation of the cuts in fishing mortality achieved by restrictions on North Sea effort. By the beginning of 2005, these restrictions are estimated to have reduced fishing mortality rates by about 37%. This is insufficient to ensure recovery of North Sea cod within the next decade.

Modelling pulse fishery systems in data-limited situations

2020 ◽  
Author(s):  
Arnaud Grüss ◽  
Derek G Bolser ◽  
Brad E Erisman
Keyword(s):  
Marine Fish ◽  
Mortality Rates ◽  
Marine Science ◽  
Spawning Aggregation ◽  
Fishing Mortality ◽  
Strong Basis ◽  
Timing Of Reproduction ◽  
Trade Off ◽  
Future Studies ◽  
Fisheries Science

Abstract Per-recruit models have been widely used since the onset of modern fisheries science, particularly in data-limited situations. When the study fishery is a pulse fishery, namely a fishery operating over a brief period followed by a long fallow period, exploitation rates rather than fishing mortality rates are employed to calculate per-recruit quantities. The literature suggests that a discrete per-recruit model is more appropriate than a continuous per-recruit model when per-recruit quantities are expressed as a function of exploitation rates. For this reason, Erisman et al. [Erisman, B. E., Grüss, A., Mascarenas-Osorio, I., Lícon-González, H., Johnson, A. F., and López-Sagástegui, C. 2020. Balancing conservation and utilization in spawning aggregation fisheries: a trade-off analysis of an overexploited marine fish. ICES Journal of Marine Science, 77: 148–161.] recently developed a discrete per-recruit model to examine the impacts of altering exploitation rates for the Gulf corvina (Cynoscion othonopterus) pulse fishery. Using Erisman et al.’s (Erisman, B. E., Grüss, A., Mascarenas-Osorio, I., Lícon-González, H., Johnson, A. F., and López-Sagástegui, C. 2020. Balancing conservation and utilization in spawning aggregation fisheries: a trade-off analysis of an overexploited marine fish. ICES Journal of Marine Science, 77: 148–161.) data, we demonstrate in detail that, under certain conditions, it is reasonable to employ a continuous per-recruit model for a pulse fishery system. We then use the designed continuous per-recruit model to demonstrate how the timing of the pulse fishery within the year relative to the timing of reproduction can be accounted for in a per-recruit model, and we explore the impacts of these model developments. This article serves as a strong basis for future studies that model pulse fishery systems in data-limited situations.

Contrasting decadal trends in mortality between large and small individuals in skate populations in Atlantic Canada

2013 ◽  
Vol 70 (1) ◽  
pp. 74-89 ◽  
Author(s):  
Douglas P. Swain ◽  
Ian D. Jonsen ◽  
James E. Simon ◽  
Trevor D. Davies
Keyword(s):  
State Space ◽  
Early Life ◽  
Mortality Rates ◽  
State Space Models ◽  
Natural Mortality ◽  
Juvenile Growth ◽  
Life Stages ◽  
Grey Seal ◽  
Early Life Stages ◽  
Scotian Shelf

Mature thorny (Amblyraja radiata), winter (Leucoraja ocellata), and smooth (Malacoraja senta) skates have declined to very low abundance in the southern Gulf of St. Lawrence (SGSL) and on the eastern Scotian Shelf (ESS). We used stage-structured state-space models to examine decadal patterns in mortality rates in these skates. Mortality at early life stages (embryos in egg cases, hatchlings, and (or) small juveniles) appeared to decrease between the 1970s and the 2000s. In contrast, estimated mortality rates increased for larger individuals over this period. Although potentially confounded in models with effects of any changes in juvenile growth, the estimated increases in mortality could not instead be attributed solely to changes in growth. Increases in the mortality of large individuals appeared to reflect increases in natural mortality, possibly due to predation by grey seals. Increases in natural mortality were not evident for skates on the neighbouring western Scotian Shelf, where grey seal abundance has remained lower. Even in the absence of fishing, recovery of skates is unlikely under current ecosystem conditions in the SGSL and on the ESS.

A sequential Bayesian methodology to estimate movement and exploitation rates using electronic and conventional tag data: application to Atlantic bluefin tuna (Thunnus thynnus)

2009 ◽  
Vol 66 (2) ◽  
pp. 321-342 ◽  
Author(s):  
Hiroyuki Kurota ◽  
Murdoch K. McAllister ◽  
Gareth L. Lawson ◽  
Jacob I. Nogueira ◽  
Steven L.H. Teo ◽  
...  
Keyword(s):  
Auxiliary Information ◽  
Bluefin Tuna ◽  
Mortality Rates ◽  
Fishing Mortality ◽  
Thunnus Thynnus ◽  
Multiple Sources ◽  
The West ◽  
Movement Rates ◽  
Bayesian Methodology ◽  
Atlantic Bluefin Tuna

This paper presents a Bayesian methodology to estimate fishing mortality rates and transoceanic migration rates of highly migratory pelagic fishes that integrates multiple sources of tagging data and auxiliary information from prior knowledge. Exploitation rates and movement rates for Atlantic bluefin tuna ( Thunnus thynnus ) are estimated by fitting a spatially structured model to three types of data obtained from pop-up satellite, archival, and conventional tags for the period 1990–2006 in the western North Atlantic. A sequential Bayesian statistical approach is applied in which the key components of the model are separated and fitted sequentially to data sets pertinent to each component with the posterior probability density function (pdf) of parameters from one analysis serving as the prior pdf for the next. The approach sequentially updates the estimates of age-specific fishing mortality rates (F) and transoceanic movement rates (T). Estimates of recent F are higher than the estimated rate of natural mortality and higher in the east than in the west. Estimates of annual T from the west to the east are higher for larger fish (6% for ages 0–3 to 16% for ages 9+). These estimates are also higher than those obtained from tagging studies before the 1990s and could be associated with changes in stock composition.

Fishing mortality rates of giant clams (Family Tridacnidae) from the Sulu Archipelago and Southern Palawan, Philippines

Coral Reefs ◽  
1988 ◽  
Vol 7 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Cesar L. Villanoy ◽  
Antoinette R. Juinio ◽  
Lambert Anthony Me�ez
Keyword(s):  
Mortality Rates ◽  
Fishing Mortality ◽  
Giant Clams

A Method of Estimating Mortality Rates from Change in Composition

1962 ◽  
Vol 19 (1) ◽  
pp. 159-168 ◽  
Author(s):  
Robert H. Lander
Keyword(s):  
Population Size ◽  
Mortality Rates ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Numerical Example ◽  
Final Population ◽  
Special Case

This paper examines the problem of estimating mortality rates from knowledge of catch and of the change in composition caused by selective fishing on one of two classes of a closed population.Estimators of fishing mortality in the presence and in the absence of natural mortality are given. An estimator of natural mortality is shown for the special case where final population size is known.A numerical example illustrates the method. Certain problems are discussed and two types of application are suggested.

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