A Robust Approach to Equilibrium Yield Curves

1986 ◽  
Vol 43 (7) ◽  
pp. 1332-1339 ◽  
Author(s):  
Gilbert G. Walter
Keyword(s):  
Fisheries Management ◽  
Management Strategies ◽  
Real Data ◽  
Concave Function ◽  
Fishing Effort ◽  
Approach To Equilibrium ◽  
Yield Curves ◽  
Fish Stocks ◽  
Robust Approach ◽  
Equilibrium Yield

The surplus yield models of fisheries management usually assume that a concave function of equilibrium yield versus fishing effort exists. However, this function is notoriously difficult to fit to real data for a number of reasons, including the fact that few fisheries are in equilibrium. A procedure for obtaining rough estimates of these equilibrium curves is introduced. Management strategies based on these estimates and the annual yield curves are also presented. The procedures are then applied to several fish stocks.

scholarly journals Costs and Returns of Fishermen in the Massachusetts Inshore Lobster Fishery

1975 ◽  
Vol 4 (2) ◽  
pp. 195-210 ◽  
Author(s):  
J. M. Gates ◽  
J. M. D'Eugenio
Keyword(s):  
Fisheries Management ◽  
Fishing Effort ◽  
The State ◽  
Economic Factors ◽  
Sufficient Criterion ◽  
Fish Stocks ◽  
The Past ◽  
Resource Managers ◽  
Lobster Fishery

The inshore lobster fishery is one of the more important ones in the Commonwealth of Massachusetts, accounting for approximately 14 percent of the total landed value of all species in Massachusetts in 1971. Until recent years this fishery accounted for virtually all the pot landings in the state. Despite numerous attempts at conservation such as gear regulation, size restrictions, and prohibitions on harvesting egg-bearing females, the fishery has been subject to rapidly increasing effort and virtually constant landings. In the past decade it has become obvious to many fishery biologists and economists that conservation of fish stocks is a necessary but not sufficient criterion for fisheries management. Resource managers have become increasingly aware of the interdependence between economic factors and the intensity, location and composition of fishing effort.

A Bayesian spatiotemporal approach to inform management unit appropriateness

2019 ◽  
Vol 76 (2) ◽  
pp. 217-237 ◽  
Author(s):  
Rujia Bi ◽  
Yan Jiao ◽  
Can Zhou ◽  
Eric Hallerman
Keyword(s):  
Great Lakes ◽  
Fisheries Management ◽  
Yellow Perch ◽  
Management Strategies ◽  
Computational Cost ◽  
Bayesian Hierarchical ◽  
Fish Stocks ◽  
Spatiotemporal Correlation ◽  
Management Actions ◽  
Gill Net

One prerequisite for sustainable fisheries management is to match management actions with biological processes. Stocks are fundamental units for fisheries management. Understanding the spatial structure of fish stocks is critical for conducting defensible stock assessments, applying efficient management strategies, and ensuring the sustainability of fish stocks. Yellow perch (Perca flavescens) is an important fishery in the Great Lakes. The appropriateness of its management units (MUs) has been identified as of high concern by the Great Lakes Fisheries Commission. Here we established integrated nested Laplace approximations and stochastic partial differential equations as two powerful tools for modeling spatiotemporal patterns of fish relative biomass. These fast computational approaches were applied to fit a Bayesian hierarchical hurdle model to occurrence and positive mass of yellow perch caught in gill-net surveys. Yellow perch relative biomass index has clear temporal variation and spatial heterogeneity, with the two middle MUs for yellow perch within Lake Erie merging together. The method explicitly models the spatiotemporal correlation structure inherent in biomass survey data at a reasonable computational cost, and the estimated spatiotemporal correlation informs stock structure.

scholarly journals Reproductive hyperallometry and managing the world’s fisheries

2021 ◽  
Vol 118 (34) ◽  
pp. e2100695118
Author(s):  
Dustin J. Marshall ◽  
Michael Bode ◽  
Marc Mangel ◽  
Robert Arlinghaus ◽  
E. J. Dick
Keyword(s):  
Fisheries Management ◽  
Management Strategies ◽  
Reference Points ◽  
Target Level ◽  
Fish Stocks ◽  
Global Food Security ◽  
Common Reference ◽  
Future Assessment ◽  
Traditional Approaches ◽  
Global Food

Marine fisheries are an essential component of global food security, but many are close to their limits and some are overfished. The models that guide the management of these fisheries almost always assume reproduction is proportional to mass (isometry), when fecundity generally increases disproportionately to mass (hyperallometry). Judged against several management reference points, we show that assuming isometry overestimates the replenishment potential of exploited fish stocks by 22% (range: 2% to 78%) for 32 of the world’s largest fisheries, risking systematic overharvesting. We calculate that target catches based on assumptions of isometry are more than double those based on assumptions of hyperallometry for most species, such that common reference points are set twice as high as they should be to maintain the target level of replenishment. We also show that hyperallometric reproduction provides opportunities for increasing the efficacy of tools that are underused in standard fisheries management, such as protected areas or harvest slot limits. Adopting management strategies that conserve large, hyperfecund fish may, in some instances, result in higher yields relative to traditional approaches. We recommend that future assessment of reference points and quotas include reproductive hyperallometry unless there is clear evidence that it does not occur in that species.

scholarly journals Coviability analysis of Western Mediterranean fisheries under MSY scenarios for 2020

2014 ◽  
Vol 71 (7) ◽  
pp. 1563-1571 ◽  
Author(s):  
Francesc Maynou
Keyword(s):  
Management Strategies ◽  
Ecosystem Approach ◽  
Fishing Effort ◽  
Western Mediterranean ◽  
Fishing Mortality ◽  
Fish Stocks ◽  
Alternative Management ◽  
Policy Goals ◽  
Management Measures ◽  
Conflicting Objectives

An ecosystem approach to fisheries (EAF) seeks to manage fisheries sustainably, including all dimensions of fisheries: biological, social and economic aspects. The separate management of these aspects may lead to conflicting objectives. Coviability analysis helps us to rank a set of choices (alternative management measures) objectively, allows us to explore which policies will ensure strong sustainability, and formally recognizes the multi-objective nature of fisheries management. The coviability of the main Western Mediterranean Spanish fisheries was examined with a bioeconomic simulation model under alternative management strategies that implement strong fishing mortality reduction policies. Based on a joint (biological and economic) viability assessment, it has been shown that Western Mediterranean fisheries require the reduction of fishing effort to ∼10% of the 2010 levels. This strong conservation measure would need to be applied as soon as possible in order for European Mediterranean fisheries to be managed at MSY, as required by legally binding international agreements, which may be unrealistic. Large reductions in fishing mortality for stocks that have been subject to high exploitation rates for decades are difficult to achieve with the current paradigm of effort control in the Mediterranean. Instead, reorienting the exploitation of Mediterranean fish stocks with management measures that combine changes in exploitation patterns with seasonal or spatial area closures, should help meet the policy goals of fishing mortality levels compatible with MSY by 2020.

scholarly journals Diversification insulates fisher catch and revenue in heavily exploited tropical fisheries

2020 ◽  
Vol 6 (8) ◽  
pp. eaaz0587 ◽  
Author(s):  
James P. W. Robinson ◽  
Jan Robinson ◽  
Calvin Gerry ◽  
Rodney Govinden ◽  
Cameron Freshwater ◽  
...  
Keyword(s):  
High Resolution ◽  
Fisheries Management ◽  
Management Strategies ◽  
Fishing Effort ◽  
Marine Resources ◽  
Nutritional Security ◽  
Fishing Vessels ◽  
Species Groups ◽  
Catch Rates ◽  
Average Catch

Declines in commercial landings and increases in fishing fleet power have raised concerns over the continued provisioning of nutritional and economic services by tropical wild fisheries. Yet, because tropical fisheries are often data-poor, mechanisms that might buffer fishers to declines are not understood. This data scarcity undermines fisheries management, making tropical fishing livelihoods particularly vulnerable to changes in marine resources. We use high-resolution fisheries data from Seychelles to understand how fishing strategy (catch diversification) influences catch rates and revenues of individual fishing vessels. We show that average catch weight decreased by 65% over 27 years, with declines in all nine species groups coinciding with increases in fishing effort. However, for individual vessels, catch diversity was associated with larger catches and higher fishing revenues and with slower catch declines from 1990 to 2016. Management strategies should maximize catch diversity in data-poor tropical fisheries to help secure nutritional security while protecting fishing livelihoods.

scholarly journals Perceptions matter: how fishermen's perceptions affect trends of sustainability in Indian fisheries

Oryx ◽  
2013 ◽  
Vol 48 (2) ◽  
pp. 218-227 ◽  
Author(s):  
Divya Karnad ◽  
Mayuresh Gangal ◽  
Krithi K. Karanth
Keyword(s):  
Fisheries Management ◽  
Tamil Nadu ◽  
Management Strategies ◽  
Policy Implications ◽  
State Regulations ◽  
Fish Stocks ◽  
Government Incentives ◽  
Fish Catch ◽  
Fishing Area ◽  
Fishing Regulations

AbstractIndian marine fisheries have expanded four-fold in the last 50 years in the form of open-access commons. Although studies predict that fish stocks are on the decline there is little evidence that these declines are being countered by changes in either fishing regulations or fishing practices. Fishermen rarely comply with regulations, instead operationalizing and directing the fishery on their own. In these circumstances understanding how fishermen perceive and use resources has significant management and policy implications. Our study examined fishermen's perceptions about the state of fish stocks and documents current fishing practice and management strategies in India. We surveyed 342 fishermen in two states, Tamil Nadu and Maharashtra. We found that 86% of fishermen perceived a decline in catch and 69% perceived a decline in bycatch. Fishermen adapt to these declines by increasing fishing area and time spent, changing their gear, and overlapping in fishing zones. The convoluted interactions between ineffective community and state regulations guiding their actions has prevented fishermen from developing successful models of sustainable fisheries management. We identified non-compliance with regulations and government incentives as an important livelihood opportunity. Non-compliance drives change in fishing practice by giving fishermen the flexibility to respond to perceived fish catch dynamics by modifying their practices. We recommend strengthening local fishing communities by enabling them to enforce fishing regulations locally and by scaling back of existing government incentives, to protect the sustainability of these fisheries.

Fishery Regulations in the ICNAF Area

1973 ◽  
Vol 30 (12) ◽  
pp. 2436-2443 ◽  
Author(s):  
A. S. Bogdanov ◽  
K. G. Konstantinov
Keyword(s):  
Atlantic Ocean ◽  
Fisheries Management ◽  
Mesh Size ◽  
Fishing Effort ◽  
International Commission ◽  
Northwest Atlantic ◽  
Important Species ◽  
Fish Stocks ◽  
Major Species ◽  
Demersal Species

Several countries have been fishing in the Northwest Atlantic Ocean for 300 years, and recently pressure on the stocks has increased greatly. The need for conservation resulted in the creation of the International Commission for the Northwest Atlantic Fisheries (ICNAF) in 1950. By 1972 16 countries were party to the Convention.When the Convention came into force, the catch in the Convention area was 1.7 million metric tons; by 1968 this had risen to 3.9 million metric tons, after which it has declined, largely because of lower cod, herring, and haddock catches.The main objective of ICNAF is to maintain the fish stocks at levels permitting maximum sustainable yields. The first regulation applied by the Commission was the fixing of minimum sizes of trawlnet meshes used to catch a number of important demersal species. At its 1972 meeting other measures were introduced, notably the fixing of maximum quotas for several subareas and for the more important species. ICNAF is therefore the international commission which has the most thorough and extensive regulation measures.At meetings in 1971 and 1972 the Commission concluded that exploitation of the major species in the ICNAF area was extremely high and that it was necessary to reduce fishing effort. These conclusions were arrived at on the basis of intensive research. Ten years of research on cod stocks is described as an example of this kind of work. It led to the conclusion that mesh size limitations were not sufficient to maintain the stocks of cod, and this was one of the strong reasons for adoption of the quotas, a step which is of great significance in international fisheries management.

CRITICAL FACTORS OF WATER CONTENT FOR FISH STOCKS IN THE WATER RESERVOIRS OF KAZAKHSTAN

2017 ◽  
pp. 9-18
Author(s):  
Saule Zhangirovna Asylbekova ◽  
Kuanysh Baibulatovich Isbekov ◽  
Evgeniy Vyacheslavovich Kulikov
Keyword(s):  
Water Content ◽  
Water Level ◽  
Water Availability ◽  
Hydrological Regime ◽  
Fishing Effort ◽  
Water Reservoirs ◽  
The Caspian Sea ◽  
Annual Fish ◽  
Commercial Fish ◽  
Fish Stocks

The hydrological regime of water reservoirs in different years has a decisive impact on the abundance of commercial fish stocks and the quality of ichthyocenoses. In this connection in 2015-2016 there was conducted a retrospective analysis and ranking of hydrological regime impact on these factors. The paper gives evaluation of catches and fish stocks under different scenarios of water availability in the main fishing ponds of the Republic of Kazakhstan that give about 80% of the annual fish catch of the country (except the Caspian Sea). There were analyzed 2000 factors of hydrological regime (water level, annual discharge) and 1845 factors of fishing stocks (catches, abundance, fish biomass). The paper determines the critical characteristics of water availability for fish stocks. There have been proposed a number of administrative decisions and actions in case if water content would approach to the critical level. Among them: limitation of fish catches in the following year; widening zones restricted for fishing; intensification of safety measures of the fish young in residual ponds during arid periods; introduction of catch standards for a unit of fishing effort in low-water years, high-water years and years with normal water level in rivers.

Taking Stock of Genetic Concepts in Fisheries Management

1991 ◽  
Vol 48 (4) ◽  
pp. 722-731 ◽  
Author(s):  
R. W. Gauldie
Keyword(s):  
Fisheries Management ◽  
Growth Rates ◽  
Allele Frequencies ◽  
Frequency Variation ◽  
Sustainable Yield ◽  
Fish Stocks ◽  
Meristic Count ◽  
Intuitive Idea ◽  
Selection Mechanisms ◽  
Insight Into

The historical development of the idea of isolated stocks of fish that can be managed as separate management units has been as strongly tied to the intuitive idea of separate races as it has been to the practical necessities of jurisprudence and the estimation of both biomass and sustainable yield by fisheries managers. Demonstrating the existence of isolated fish stocks and delineating their boundaries has generally proved unsuccessful. Various techniques ranging from meristic count differences to polymorphic allelism have usually failed. However, in the pursuit of isolated stocks, biochemists have uncovered a great deal of information about the variation of polymorphic allele frequencies over time and space. Following the shift in opinion away from stochastic to natural selection mechanisms in allele frequency variation, it is evident that the observed variation in allele frequencies allows more insight into the biology of fishes than into the breeding structure of populations. These insights argue against the idea of isolated stocks of fish with homogeneous growth rates that are the basis of the sustainable yield models in favour of migration-linked stocks with heterogeneous growth rates.

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