Simple Bioeconomic Model Research Articles

Social relationship dynamics mediate climate impacts on income inequality: evidence from the Mexican Humboldt squid fishery

Small-scale fisheries are critically important for livelihoods around the world, particularly in tropical regions. However, climate variability and anthropogenic climate change may seriously impact small-scale fisheries by altering the abundance and distribution of target species. Social relationships between fishery users, such as fish traders, can determine how each individual responds and is affected by changes in fisheries. These informal cooperative and competitive relationships provide access, support, and incentives for fishing and affect the distribution of benefits. Yet, individuals’ actions and impacts on individuals are often the primary focus of the economic analyses informing small-scale fisheries’ formal management. This focus dismisses relevant social relationships. We argue that this leads to a disconnect between reality and its model representation used in formal management, which may reduce formal fisheries management’s efficiency and efficacy and potentially trigger adverse consequences. Here, we examine this argument by comparing the predictions of a simple bioeconomic fishery model with those of a social-ecological model that incorporates the dynamics of cooperative relationships between fish traders. We illustrate model outcomes using an empirical case study in the Mexican Humboldt squid fishery. We find that (1) the social-ecological model with relationship dynamics substantially improves accuracy in predicting observed fishery variables to the simple bioeconomic model. (2) Income inequality outcomes are associated with changes in cooperative trade relationships. When environmental temperature is included in the model as a driver of species production dynamics, we find that climate-driven temperature variability drives a decline in catch that, in turn, reduce fishers’ income. We observe an offset of this loss in income by including cooperative relationships between fish traders (oligopoly) in the model. These relationships break down following species distribution changes and result in an increase in prices fishers receive. Finally, (3) our social-ecological model simulations show that the current fishery development program, which seeks to increase fishers’ income through an increase in domestic market demand, is supported by predictions from the simple bioeconomic model, may increase income inequality between fishers and traders. Our findings highlight the real and urgent need to re-think fisheries management models in the context of small-scale fisheries and climate change worldwide to encompass social relationship dynamics.

The Interaction Between Stock Dynamics, Fishing and Climate Caused the Collapse of the Jack Mackerel Stock at Humboldt Current Ecosystem

The collapse of marine fisheries had caused a cascade of dramatic ecological, social and economic consequences. Recognizing the complex nature of the fisheries collapses, two basic minimum elements should be included in fishery models. First, the dynamics of the fish population and second the changes in the fishing effort that are co-determined by the harvest and economic forces. The rapid and abrupt shifts in abundance exhibited by some marine fish populations can be driven by the fishing fleet behaving like generalist predators. Here we develop a population dynamic model with negative feedback in the fish stock and a sigmoid functional response of the fishing effort, we assume that the rate of change in effort from year to year is a positive function of fishery revenue, but is negatively influenced by fishing costs which are proportional to the annual ratio between fishing effort/stock size. We use this model to consider how changes in the fishing effort driven by ecological and economic forces can generate the observed large abrupt shifts in the abundance of the jack mackerel (Trachurus murphyi) stock at south-eastern Pacific. Our model predict that jack-mackerel stock dynamics can have alternate stable states. Our simple bio-economic model allows us to explore some management responses in a heuristic manner, where the most critical element seems to be the combination of an n-shaped isocline for fish stock growth and a slanted isocline of fishing effort whose slope is highly sensitive to changes in the profitability of the fishery.

Effect of size heterogeneity of Nile tilapia (Oreochromis niloticus) on the optimal harvest time: a bioeconomics approach

A critical problem in the production of Nile tilapia Oreochromis niloticus in intensive and hyper-intensive systems is the heterogeneity of body sizes as it influences the final production and economic yield. The objective of this study was to calculate the bioeconomic effect of size heterogeneity on the production of Nile tilapia at a commercial level and to determine the optimum harvest time (OHT) considering four minimum marketable sizes target (Mms = 350, 400, 450, 500 g). Two seeding strategies were evaluated: homogeneous seeding (HM) with a 96.55 ± 24.51 g initial body weight and heterogeneous seeding (HT) with a 100.17 ± 5.91 g initial weight. Fish from both treatments were stocked at 40 fish m-3 in triplicate using a randomized design. The calculated quasi-profits of variable costs showed an inversely proportional relationship with the minimum market size in both groups. The smaller size dispersion in HM generated higher profits than HT. The OHT for Mms [350, 500 g] of HM population was 180 days, with a mode of 641 g. The OHT was also 180 days for the HT population but only for the Mms [350, 400 g] and a mode of 578 g. In terms of quasi-profits, the HM produced 19.93% more quasi-profit than the HT in the market size of 350 g at 180 days (HM = 0.50 US$ kg-1; HT = 0.44 US$ kg-1). The simple bioeconomic model presented here can help producers manage a series of economic decisions associated with OHT, when targeting different market segments requiring different Mms.

Making progress on bycatch avoidance in the ocean salmon fishery using a transdisciplinary approach

Abstract Transdisciplinary research that crosses disciplinary boundaries and includes stakeholder collaboration is increasingly being used to address pressing and complex socio-ecological challenges in the Anthropocene. In fisheries, we see transdisciplinary approaches being employed to address a range of challenges, including bycatch where fine-scale data are collected by fishers to help advance spatial approaches in which fishing effort is shifted away from bycatch hotspots. However, the spatio-temporal overlap of morphologically undistinguishable fish stocks, some of which are depleted, is a major concern for some fisheries, including the Pacific Northwest troll Chinook salmon (Oncorhynchus tshawytscha) fishery. In this study, we develop and evaluate a transdisciplinary approach to avoid bycatch in the commercial Chinook salmon troll fishery off northern and central Oregon. Based on a unique genetic dataset collected by fishers, fine-scale patterns of stock distribution and spatial stock overlap were assessed. Two hotspots of weak Klamath stock in the study region were identified and related to bathymetry. Results were then fed into a simple bioeconomic model to evaluate costs and benefits of reallocating effort under two scenarios of allowable catch of a weak stock (Klamath). The scenarios demonstrate that effort reallocation could lead to a reduction in Klamath catch as well as to increases in net profit, but outcomes depend on the distance from the fleets' home port to the new fishing area. The output of the model at its current stage should be regarded strategically, providing a qualitative understanding of the types of best fleet strategies. Despite some challenges in transdisciplinarity discussed in this study and the present limitations to incorporate fine-scale changes of Chinook salmon stock distributions in management regulations, we contend that this approach to research has the potential to lead to improved management outcomes.

A bioeconomic analysis of conserving freshwater values in an agricultural landscape

Water is a finite resource that must be shared among multiple users and economic and conservation objectives can often be seen as being in conflict. We explored this perception by conducting an integrated bioeconomic analysis of irrigated agriculture and the conservation of freshwater attributes in an agricultural landscape, the Tasmanian Midlands. We constructed a simple bioeconomic model based on current hydrology, water allocation, land use and freshwater ecosystem values, and quantified the economic returns from irrigation under a range of future climate, agricultural development and conservation scenarios. We found that projected climate conditions and conserving freshwater values in good condition had small effects on economic returns to irrigators, and that enterprise diversity and the area irrigated were major drivers of economic returns in this landscape. The availability of land suitable for irrigation rather than irrigation water itself appeared most likely to limit the economic returns from irrigation in the future. We provide a multi-criteria analysis for comparing development and conservation scenarios at a regional scale to inform planning and decision making in conservation and natural resource management. Our approach brings irrigation and conservation concerns into the same context and demonstrates that conservation need not necessarily limit agricultural development.

Destructive fishing and fisheries enforcement in eastern Indonesia

A simple bioeconomic leader-follower model was constructed to simulate snapper (family Lutjanidae) and grouper (family Serranidae) fisheries in Raja Ampat, Indonesia, an area of significant coral and fish biodiversity. We developed a leader-follower game, wherein the Regency government as the leader chooses an enforcement model to discourage illegal fishing. Fishers are then given a choice to fish using legal gears, such as handlines, or to fish with illegal gears, e.g. dynamite (for snapper) or cyanide (for grouper). Given prices and costs of legal and illegal fishing, the status quo simulations with no Regency enforcement result in a large amount of illegal catch throughout the 50 yr simulation, which agrees with expert opinion that destructive illegal fishing is occurring in the region. In an attempt to include ecosystem-based management principles into Raja Ampat governance, we introduce an enforcement regime in the form of detecting and punishing illegal fishing. Results suggest that current fishing practices do not account for the disproportionate ecosystem effects of destructive fishing, and that elimination of dynamite fishing may be easier for the government due to the high profitability of the live fish trade connected with cyanide fishing.

Stocking Rate Decisions Are Not Related to What You Paid for Your Land or Pickup

• We develop a simple bio-economic model to reflect the stocking rate decision for a profit-seeking land manager and use it to identify factors influencing the optimal stocking rate. • The optimal stocking rate will be bounded by the rate that maximizes average animal performance and that maximizing total animal production per unit of rangeland. • The optimal stocking rate tends closer toward the upper bound as the ratio of the value of the animal product increases relative to the variable costs of production. • Fixed costs or overhead do not influence the optimal stocking rate, but will affect the amount of profit.

Optimal Selectivity and Effort Cost A Simple Bioeconomic Model with an Application to the Bay of Biscay Nephrops Fishery

This article investigates the relationship between optimal gear selectivity and effort cost in the fishing industry. We first show that optimal selectivity depends negatively on the level of effort cost, but that this relationship is not continuous. Optimal selectivity switches when real effort cost goes beyond a certain level, and this switch induces a non-marginal reduction in the level of fishing effort. In the second part of this article, we show that the current level of real effort cost in the Nephrops fishery of the Bay of Biscay is far below the switch point, which makes high selectivity optimal. The discrepancy between optimal and current selectivity may be explained by the state of the fishery management and also by the fact that selectivity is hardly observable with the type of gear presently used.

The value of Pacific sardine as forage fish

Abstract This paper develops a simple bioeconomic model to investigate the economic and ecological issues associated with the commercial harvest of Pacific sardines relative to their value as forage for commercially, recreationally, and ecologically important predators in the California Current ecosystem. The model was used to evaluate how changes in the net per unit value of sardines, the net per unit value of sardine predators, and the transfer efficiency of predators affect the total net value of sardines, i.e. the net value of catches and the net value from sardine predation. Given recent market conditions for sardines and their commercial predators, and transfer efficiencies derived from predation data of the 1960s, it was found that the value of commercially caught predators and the efficiency by which they convert sardines to exploitable biomass were most important in determining the viability of the sardine fishery. The values assumed for predators that are not commercially caught were of no consequence under these conditions. Taking the value of sardines as forage into account does not necessarily mean an either-or situation for the fishery. As long as there is some measure of net value from the fishery and net value from predation, both benefit society at large.

Interdecadal variability of anchoveta abundance and overcapacity of the fishery in Peru

Paleontological and historical stock abundance estimates indicate that pelagic fish populations inhabiting upwelling ecosystems undergo large interdecadal variations in abundance with amplitudes equal to, if not larger than, the interannual variability. The interdecadal variability is characterized by periods of high and low abundance, termed “pseudo-cycles”, because of their irregular periodicity. Fisheries targeting small pelagic fish suffer from overall overcapitalization, like many other fisheries, but also from an additional overcapitalization problem: a phase displacement between rapid fish population decreases and a slower disinvestment which follows. This lag produces economic hardship. Here we document the fish:fishery relationship for the Peruvian anchoveta. Anchoveta pseudo-cycles of 20 to >100 years are observed, with the present stock abundance most likely located near upper part of the cycle. Fleet overcapacity expressed as the proportion of unused present capacity is estimated at 72% and processing overcapacity at 89%. A simple bio-economic model demonstrates the risks associated with the pseudo-periodicity in fish stock abundance in conjunction with fishery investment, open access, and overcapacity: a timing bomb for the fishing sector. The lag between disinvestment and decrease in fish abundance is quantified. A reduction of the fishing and processing capacity and measures to decrease the investment lag are recommended to limit the social, economical and political tensions that will result from the expected decrease in stock abundance. Finally, some management options to reduce these risks are discussed.

Assessment of Economic and Water Quality Impacts of Land Use Change Using a Simple Bioeconomic Model

The objective of this study is to assess the economic and water quality impact of land use change in a small watershed in the Wiregrass region of Alabama. The study compares changes in water quality and revenue from agricultural and timber production due to changes in land use between years 1992 and 2001. The study was completed in two stages. In the first stage, a biophysical model was used to estimate the effect of land use change on nitrogen and phosphorus runoff and sediment deposition in the main channel; in the second stage, farm enterprise budgeting tools were used to estimate the economic returns for the changes in land use condition. Both biophysical and economic results are discussed, and a case for complex optimization to develop a decision support system is presented.

Effort dynamics in a fisheries bioeconomic model: A vessel level approach through Game Theory

Red shrimp, Aristeus antennatus (Risso, 1816) is one of the most important resources for the bottom-trawl fleets in the northwestern Mediterranean, in terms of both landings and economic value. A simple bioeconomic model introducing Game Theory for the prediction of effort dynamics at vessel level is proposed. The game is performed by the twelve vessels exploiting red shrimp in Blanes. Within the game, two solutions are performed: non-cooperation and cooperation. The first is proposed as a realistic method for the prediction of individual effort strategies and the second is used to illustrate the potential profitability of the analysed fishery. The effort strategy for each vessel is the number of fishing days per year and their objective is profit maximisation, individual profits for the non-cooperative solution and total profits for the cooperative one. In the present analysis, strategic conflicts arise from the differences between vessels in technical efficiency (catchability coefficient) and economic efficiency (defined here). The ten-year and 1000-iteration stochastic simulations performed for the two effort solutions show that the best strategy from both an economic and a conservationist perspective is homogeneous effort cooperation. However, the results under non-cooperation are more similar to the observed data on effort strategies and landings.

Assessment of the Sustainability of Bushmeat Hunting Based on Dynamic Bioeconomic Models

Open-access hunting is a dynamic system in which individual hunters respond to changes in system variables such as costs of hunting and prices obtained for their catch. Sustainability indices used by conservationists ignore these human processes and focus only on the biological sustainability of current offtake levels. This focus implicitly assumes that offtake is constant, says little about the actual sustainability of the system, and fails to provide any basis for predicting the impact of most feasible management interventions. A bioeconomic approach overcomes these limitations by explicitly integrating both the biological and human components of the system. We present a graphical representation of a simple bioeconomic model of bushmeat hunting and use it to demonstrate the importance of considering system dynamics when assessing sustainability. Our results show that commonly used static sustainability indices are often misleading. The best method to assess hunting sustainability is situation dependent, but characterizing supply and demand curves, even crudely, has greater potential than current approaches to provide robust predictions in the medium term.

IN PURSUIT OF COST-EFFECTIVE FISHERIES ENHANCEMENT OF NEW SOUTH WALES BLACKLIP ABALONE, HALIOTIS RUBRA (LEACH) FISHERY

The diverse and often complex essential components of successful marine stock enhancement are briefly reviewed. Progress on a project to enhance the New South Wales blacklip abalone (Haliotis rubra) fishery is discussed to demonstrate that for sedentary reef invertebrates such as abalone, successful enhancement entails an understanding of recruitment and production limiting factors. These include age and size specific growth and mortality rates. These variables encompass the influence of other species within reef ecosystems, especially predators and species that compete directly with them for space, shelter and food. This discussion is also used to demonstrate that such difficult projects can be facilitated and refined using a simple bio-economic model centered on two interdependent tasks. The first is to minimize net costs per unit of additional sustainable production generated by enhancement. The second is to determine the minimum amount of additional sustainable production required to render a project cost-effective. This first task has, as expected, proven complex and its resolution protracted and expensive, requiring innovative biotechnology and a comprehensive knowledge of the natural biology of blacklip abalone. This discussion principally reflects the perspective of the direct potential beneficiaries of abalone fisheries enhancement, namely commercial and recreational fishers and does not deal extensively with wider views and interests of other stakeholders, namely relevant government agencies and NGOs and the general public.

Use of simple bioeconomic models to estimate optimal effort levels in the Korean coastal flounder fisheries

The Korean fishing industry is currently subject to overexploited resources arising from excessive levels of fishing effort. Measures to reduce effort in the industry have been instigated. However, for the mixed gear, multi-species inshore fleet, determining the appropriate level of effort is problematic. This is made more difficult through limited catch and effort data. In this paper, a simple surplus production bioeconomic model for the flounder fishery is developed based on different effort standardisation approaches to estimate the optimal level of effort in the fishery. The model is based on a subset of catch and effort data, and implications of this for the assessment of global effort levels are considered. The results indicate that even with poor information, relatively robust estimates of necessary reductions in fishing effort can be derived.

A simple approach for dealing with dynamics and uncertainty in fisheries with heterogeneous resource and effort distribution

Most fisheries models are based on dynamic pool assumptions. For sedentary and sessile species, these assumptions are inadequate, because they are spatially distributed in patches that vary in size, density and age structure. A simple bioeconomic model, negative binomial (NEGBIN), is proposed; this model relaxes the dynamic pool assumption without entering into the complexities of a geographically structured model. NEGBIN assumes a probability density function (the negative binomial), to describe heterogeneity in the density distribution over the population range. The model incorporates decision theory and different levels of risk aversion in resource management. The uncertainty associated with alternative fishing strategies, given imperfect knowledge about virgin stock biomass, is also included in the analysis. The model is applied to the Mesodesma donacium (surf clam) fishery in the central northern zone of Chile (South America). Alternative management strategies are evaluated with different levels of risk aversion. In the fisheries literature to date, this approach to evaluating the uncertainty associated with spatial allocation decisions has been rare. It is suggested that this kind of analysis, whether accompanied by quantitative probabilities of alternative states of nature or not, is an alternative way of dealing with risk and uncertainty in spatial allocation decisions.

Estimation of biological and economic parameters of a bioeconomic fisheries model using dynamical data assimilation

A new approach of model parameter estimation is used with simulated measurements to recover both biological and economic input parameters of a natural resource model. The data assimilation technique is the variational adjoint method (VAM) for parameter estimation. It efficiently combines time series of artificial data with a simple bioeconomic fisheries model to optimally estimate the model parameters. Using identical twin experiments, it is shown that the parameters of the model can be retrieved. The procedure provides an efficient way of calculating poorly known model parameters by fitting model results to simulated data. In separate experiments with exact and noisy data, we have demonstrated that the VAM can be an efficient method of analyzing bioeconomic data.

Cost minimization and input substitution in the production of gilthead seabream

This paper studies cost minimization decisions by utilizing a simple bioeconomic model for gilthead seabream (Sparus aurata). This model is based on a biological growth model which accounts for the effects of temperature and ration size. Although the implicit production function derived from the growth model is shown to be quasiconcave, it is not homothetic nor quasilinear. Further, technology shows increasing returns with respect to ration size and harvesting time. Optimization decisions are analyzed in two different contexts, a restricted biological setting and an expanded economic problem. It is shown that the optimal ration size increases for the latter context, reaching values commonly accepted in current industrial practice. Even though the elasticity of substitution to the shadow input prices is positive at the optimal ration size, the latter is rather robust to changes in input prices. However, optimal costs show larger sensitivity to the labor price than to the feeding and managerial costs.

Sustainability of marine fishing: a case study of West Bengal

The marine fishery sector in India is important not only for domestic demand for protein food requirements but also from the imperatives of exports. An increased investment in this sector has taken place during the last few years and the fishing fleet has expanded at a very rapid rate. Presently, however, marine fishers are facing difficulties in fish capture in spite of exerting the same and sometimes more effort. Thus the question of the sustainability of marine fishing arises. The sustainability of marine fishing in the Digha-Shankarpur coastal region has been studied through estimation of the maximum sustainable yield based on a simple bioeconomic model. WLS estimation has been done to remove heteroscedastic disturbances. Estimated results show that actual yields of all varieties are still below maximum sustainable yield (MSY) except prawn, which has reached near optimal levels.

A simple bioeconomic model of a marine reserve

We model the effect of a no-take reserve in a marine fishery management area, such as on a coral reef. Implicitly, eggs and larvae are mobile but adults are not; and there is open access fishing outside the reserve. A reserve is found to increase equilibrium catch if the prior ratio of stock to carrying capacity is less than a half, and the catch-maximising reserve proportion rises towards a half as this ratio falls towards zero. After initial adjustment, long-run stability is improved by a reserve. We estimate that coral reef reserves could increase world wide annual catches by about a billion dollars.