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 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.

scholarly journals Estimating natural and fishing mortality and tag reporting rate of southern rock lobster (Jasus edwardsii) from a multiyear tagging model

2001 ◽  
Vol 58 (12) ◽  
pp. 2490-2501 ◽  
Author(s):  
S D Frusher ◽  
J M Hoenig
Keyword(s):  
Mortality Rates ◽  
Fishing Effort ◽  
Reporting Rate ◽  
Standard Errors ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Rock Lobster ◽  
Relative Standard ◽  
Jasus Edwardsii ◽  
Mortality Estimates

Fishing and natural mortality rates and tag reporting rate for rock lobsters (Jasus edwardsii) in northwest Tasmania, Australia, were estimated using multiyear tagging models. These estimates are necessary for assessment of the resource. Several models were examined that had either two or three tagging events each year, and either combined sexes or kept sexes separate. The model that best described the dynamics of the fishery utilized three tagging events within a year. The year was divided into discrete periods and, within each year, fishing effort and duration of period were used to apportion fishing and natural mortalities, respectively, to the periods. The separation of fishing mortalities by sex was not found to improve the models. Although high (1.0–1.2·year–1), the instantaneous fishing mortality estimates were comparable to estimates obtained from other methods and the relative standard errors were low. Reporting rate estimates were also precise and indicated a lack of participation by the fishing industry. Estimates of natural mortality were low (0.00–0.02·year–1) but imprecise.

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.

Optimal Effort Allocation Among Competing Mixed-Species Fisheries, Subject to Fishing Mortality Constraints

1986 ◽  
Vol 43 (1) ◽  
pp. 90-100 ◽  
Author(s):  
S. A. Murawski ◽  
J. T. Finn
Keyword(s):  
Optimal Allocation ◽  
Mortality Rates ◽  
Fishing Effort ◽  
Discrete Distributions ◽  
Sensitivity Analyses ◽  
Otter Trawl ◽  
Individual Species ◽  
Fishing Mortality ◽  
Effort Allocation ◽  
By Catch

A linear programming (LP) approach to effort allocation among two or more fisheries (fleets) exploiting several common species/stocks is described and applied to otter trawl fisheries exploiting demersal fish stocks on Georges Bank (northeastern United States). Total instantaneous fishing mortality on a particular species (i) is computed as the linear summation of fishing mortalities generated by each fishery (j):[Formula: see text]where fj is the amount of standardized fishing effort exerted in fishery j and qij is the catchability coefficient for species i taken in fishery j. Mortality on species i due to both directed fishing and by-catch can thus be accounted for in the qij's. Optimal allocation of effort among the j fisheries may be considered a minimization problem (minimize Σfj), subject to the constraints that fishing mortality rates on particular species are maintained at, above, or below certain predefined levels. Fishing mortality goals for individual species can be based on various biological and/or economic criteria: fishing mortality rates that prevent growth or recruitment overfishing, or that optimize productivity from predator–prey systems. Other constraints in the LP model may be included to modify optimal solutions based on various economic and social considerations (e.g. protection of certain fisheries). Sensitivity analyses indicate the general infeasibility of maintaining relatively high or low fishing mortality rates on ubiquitously distributed species, while moderately fishing species with more discrete distributions, due to by-catch considerations.

Mark-recapture estimation of mortality and migration rates for sea trout (Salmo trutta) in the northern Baltic sea

2016 ◽  
Vol 74 (1) ◽  
pp. 286-300 ◽  
Author(s):  
Rebecca E. Whitlock ◽  
Juho Kopra ◽  
Tapani Pakarinen ◽  
Eero Jutila ◽  
Adrian W. Leach ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Salmo Trutta ◽  
Mortality Rates ◽  
Fish Population ◽  
Fishing Mortality ◽  
Recreational Fisheries ◽  
Sources Of Information ◽  
Mark Recapture ◽  
Sea Trout ◽  
And Migration

Knowledge of current fishing mortality rates is an important prerequisite for formulating management plans for the recovery of threatened stocks. We present a method for estimating migration and fishing mortality rates for anadromous fishes that combines tag return data from commercial and recreational fisheries with expert opinion in a Bayesian framework. By integrating diverse sources of information and allowing for missing data, this approach may be particularly applicable in data-limited situations.Wild populations of anadromous sea trout (Salmo trutta) in the northern Baltic Sea have undergone severe declines, with the loss of many populations. The contribution of fisheries to this decline has not been quantified, but is thought to be significant. We apply the Bayesian mark-recapture model to two reared sea trout stocks from the Finnish Isojoki and Lestijoki Rivers. Over the study period (1987–2012), the total harvest rate was estimated to average 0.82 y–1 for the Isojoki River stock and 0.74 y−1 for the Lestijoki River stock. Recreational gillnet fishing at sea was estimated to be the most important source of fishing mortality for both stocks, particularly during the 1980s and 1990s. Our results indicate a high probability of unsustainable levels of fishing mortality for both stocks, and illustrate the importance of considering the effect of recreational fisheries on fish population dynamics.

Estimating exploitation rates of migrating yellowtail flounder (Limanda ferruginea) using multistate mark–recapture methods incorporating tag loss and variable reporting rates

2009 ◽  
Vol 66 (8) ◽  
pp. 1245-1255 ◽  
Author(s):  
Laura Cowen ◽  
Stephen John Walsh ◽  
Carl James Schwarz ◽  
Noel Cadigan ◽  
Joanne Morgan
Keyword(s):  
Mortality Rates ◽  
Assessment Model ◽  
Natural Mortality ◽  
Mark Recapture ◽  
Yellowtail Flounder ◽  
Limanda Ferruginea ◽  
Tag Loss ◽  
Model Migration ◽  
Reporting Rates ◽  
Mortality Estimates

Multistate mark–recapture models can be used to model migration through stratification of the study area into states (location). However, the incorporation of both tag loss and reporting rates is new to the multistate paradigm. We develop a migration model for fish that incorporates tag loss and reporting rates but has as its primary purpose the modelling of exploitation and natural mortality rates. This model is applied to a 2000–2004 yellowtail flounder ( Limanda ferruginea ) tagging study on the Grand Bank of Newfoundland, Canada. We found that exploitation rates varied over both location and years, ranging from 0.000 to 0.047. Migration into the centre of the Grand Bank (state 2) was three times higher than migration out. The estimate of the instantaneous annual natural mortality rate was 0.256, which is equivalent to an annual survival rate of 0.880. We describe how these mortality estimates will be quite valuable in specifying an assessment model for this stock.

An Estimation of the Mortality Rates in a Population of Tilapia esculenta Graham (Pisces, Cichlidae) in Lake Victoria, East Africa

1963 ◽  
Vol 20 (1) ◽  
pp. 195-227 ◽  
Author(s):  
D. J. Garrod
Keyword(s):  
Population Dynamics ◽  
Marked Effect ◽  
Lake Victoria ◽  
Central Africa ◽  
Mortality Rates ◽  
Fishing Effort ◽  
Tropical Fish ◽  
Commercial Fisheries ◽  
Fishing Mortality ◽  
Gill Net

In the commercial fisheries of the great lakes of Central Africa the nylon gill net is the most widespread type of gear in use at present. Recent increases in fishing effort are believed to have had a marked effect upon the abundance of some species and this paper describes a method of estimating the fishing mortality from a fishery of this type. The method is demonstrated in its application to a population of Tilapia esculenta in Lake Victoria. In particular the data from the gill net fishery are combined with the known selectivity of the gear to distinguish between fishing mortality and trends in natural loss from the population with increasing age of the fish. The study also shows that the population dynamics of a tropical fish species are amenable to conventional techniques of analysis.

scholarly journals Partial fishing mortality per fishing trip: a useful indicator of effective fishing effort in mixed demersal fisheries

2006 ◽  
Vol 63 (3) ◽  
pp. 556-566 ◽  
Author(s):  
Adriaan D. Rijnsdorp ◽  
Niels Daan ◽  
Willem Dekker
Keyword(s):  
Fishing Effort ◽  
Fine Tuning ◽  
Positive Trend ◽  
Fishing Mortality ◽  
Auxiliary Equipment ◽  
Solea Solea ◽  
Seasonal And Spatial Variations ◽  
Sea Beam ◽  
Quota Management ◽  
Engine Power

Abstract Effort management has been proposed as an alternative for quota management in mixed demersal fisheries. It requires a metric to estimate the fishing mortality imposed by a given quantity of nominal fishing effort. Here, we estimate the partial fishing mortality rate imposed by one unit of fishing effort (Fpue) during individual fishing trips and explore the usefulness of this indicator for managing North Sea beam trawlers >300 hp targeting sole (Solea solea) and plaice (Pleuronectes platessa). Fpue is positively related to vessel engine power, and increased annually by 2.8% (sole) and 1.6% (plaice). The positive trend was due to an increase in skipper skills and investment in auxiliary equipment, the replacement of old vessels by new ones and, to a lesser extent, to upgrade engines. The average Fpue imposed per day at sea by a 2000 hp beam trawler was estimated to be 1.0 × 10−5 (sole) and 0.6 × 10−5 (plaice), and it showed substantial seasonal and spatial variations. The Fpue of sole and plaice were negatively related in summer and showed no relationship in winter. The existence of predictive seasonal and spatial patterns in Fpue opens up the possibility of fine-tuning management by directed effort restrictions and uncoupling management of plaice and sole.

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