Facilitation of fisheries by natural predators depends on life history of shared prey

Predators commonly share prey with human exploiters, intuitively suggesting that there is an inherent human–predator conflict through competition for prey. Here we studied the effects of fishing and predation mortality on biomass distributions and yields of shared prey using a size‐structured model of competing populations, describing the life histories of Baltic Sea sprat and herring. Whereas both species responded in a similar fashion to increased fishing mortality, with decreasing juvenile and adult biomasses, we found that responses to predation mortality differed between species. Sprat only display weak compensatory responses with increasing predation mortality, while over a substantial range of mortalities there was a strong increase in adult (and total) herring biomass, i.e. overcompensation. The observed biomass overcompensation results from relaxed intraspecific competition as predation mortality increased, allowing for faster individual growth rates that in turn lead to a change in population composition (juvenile:adult biomass ratio). Our results suggest that the potential for biomass overcompensation is higher for species exhibiting substantial growth after maturation. Differences in size‐selectivity of predators and fishing mortality resulted in a positive effect of predation mortality on fisheries yields, which can be explained by an overcompensatory response in adult herring biomass. Thus, somewhat counter intuitive, our results suggest that fishermen, depending on prey life history, may actually benefit from allowing for a higher abundance of predators, despite competing for shared prey.     

Fishing destabilizes the biomass flow in the marine size spectrum

Fishing impacts on marine food webs are predicted by simulations of a size spectrum community model. In this model, predation is determined by predator and prey size and abundance, and drives predator growth and prey mortality. Fishing amplifies temporal oscillations in the biomass flow. Oscillations appear at lower fishing intensity and have wider amplitude when fishing is selective (removes a narrow size range) and/or when large fish are targeted, than when fishing is more balanced (catching a larger size range) or when small fish are targeted. A novel index of size diversity is developed, and is shown to be sensitive to both fishing intensity and selectivity. To avoid unstable food web dynamics with potential harmful consequences for fisheries, limiting both fishing intensity and selectivity might be an appropriate exploitation strategy.     

Management reference points to account for direct and indirect impacts of fishing on marine mammals

Reference points can help implement an ecosystem approach to fisheries management (EAF), by establishing precautionary removal limits for nontarget species and target species of ecological importance. PBR (Potential Biological Removal), developed under the U.S. Marine Mammal Protection Act (MMPA), is a limit for direct mortality for marine mammals, but it does not account for indirect effects of fishing due to prey depletion. I propose a generalization of PBR (called PBR*) to account for plausible changes in marine mammal carrying capacity (ΔK) from prey biomass decline relative to two example benchmarks: SSB_MSY (maximum sustainable yield biomass for all known prey species) or SSB_K (unfished prey biomass). PBR* can help identify when indirect fishing effects (alone, or combination with direct mortality estimates) may stymie MMPA objectives, and could inform catch limit estimates for target species that are also important as marine mammal prey. As a case study, I applied PBR* estimates to evaluate the possible combined direct + indirect effects of fishing on cetaceans in northeastern U.S. waters. Estimated distributions for ΔK were based on fish stock assessments and meta‐analysis of predator‐prey relationships from the mammalian literature. Based on this analysis, increased risk of marine mammal depletion due to indirect fishing effects was not evident, although this result must be interpreted cautiously given our limited understanding of cetacean diets and marine trophic dynamics. This study is intended to illustrate a possible practical approach for incorporating indirect fisheries impacts on marine mammals into a comprehensive management framework, and it raises several scientific and policy issues that merit further investigation.     

Species‐specific ontogenetic diet shifts attenuate trophic cascades and lengthen food chains in exploited ecosystems

Ontogenetic diet shifts are pervasive in food websbut rules governing their emergence and the implications for trophic cascades are only partly understood. Recent theoretical advances in multispecies size spectrum models (MSSMs) predict that the emergence of ontogenetic diet shifts are driven primarily by size‐selective predation and changes in the relative abundances of suitably sized prey. Howeverthese assumptions have not yet been tested with data. Herewe developed alternative MSSMs based on different assumptions about the nature of species and size‐based preferences and tested them using an extensive dietary database for the Eastern Bering Sea (EBS). MSSMs with both size and species‐specific prey preferences correctly predicted approximately three‐fold more of the diet links than those that assumed fixed species preferences. Importantlythese model assumptions also had a profound effect on the strength of fishing‐induced trophic cascades and the emergent trophic structure of the community with and without fishing. The diet‐informed models exhibited lower predation mortality ratesparticularly for small individuals (less than 1 g) whichin turnreduced the intensity and reach of fishing‐induced trophic cascades up the size spectrum. If the level and size dependency of piscivory observed in EBS predators is typical of other systemsthe potential for fishing‐induced trophic cascades may be over‐stated in MSSMs as they are currently formulated and parameterized. Representation of species‐specific ontogenetic shifts in diet can strongly influence system responses to perturbationsand the extensions we propose should accelerate adoption of MSSMs as frameworks for exploring size‐based food web theory and developing modeling tools to support strategic management decisions.     

Dynamics of black spot sea bream (Pagellus bogaraveo) mean length: evaluating the influence of life history parameters, recruitment, size selectivity and exploitation rates

Stochastic simulations were used to evaluate the influence of recruitment pattern (log‐normal, decreasing), size selectivity (normal, logistic model) and fishing mortality pattern (abrupt, continuous increase in fishing mortality) on the evolution of mean length and the dispersion of mean length for a relatively long‐lived deep‐water species, the black spot sea bream (Pagellus bogaraveo). An abrupt increase in fishing mortality resulted in mean size decreasing and stabilizing at a lower level while a steady increase in fishing mortality caused the continuous decrease in mean size that has been reported for many long‐lived species. Decrease in mean size was greatest for logistic model simulations and for cases where fish were susceptible to capture at a small size. Logistic selectivity, with decreasing recruitment and increasing fishing mortality over time, resulted in mean length and variability in mean length trends similar to that observed for the Strait of Gibraltar fishery. Furthermore, it was found with the declining recruitment that moderate increases in fishing mortality can result in significant decreases in mean length. Given the importance of mean size as an indicator of the state of a resource, these simulations are a useful alternative or complement to standard fisheries assessment methods, helping to provide information on exploitation patterns and rates that can be used for conservation and management.     

Representing Density Dependent Consequences of Life History Strategies in Aquatic Ecosystems: EcoSim II

EcoSim II uses results from the Ecopath procedure for trophic mass-balance analysis to define biomass dynamics models for predicting temporal change in exploited ecosystems. Key populations can be represented in further detail by using delay-difference models to account for both biomass and numbers dynamics. A major problem revealed by linking the population and biomass dynamics models is in representation of population responses to changes in food supply; simple proportional growth and reproductive responses lead to unrealistic predictions of changes in mean body size with changes in fishing mortality. EcoSim II allows users to specify life history mechanisms to avoid such unrealistic predictions: animals may translate changes in feeding rate into changes in reproductive rather than growth rates, or they may translate changes in food availability into changes in foraging time that in turn affects predation risk. These options, along with model relationships for limits on prey availability caused by predation avoidance tactics, tend to cause strong compensatory responses in modeled populations. It is likely that such compensatory responses are responsible for our inability to find obvious correlations between interacting trophic components in fisheries time-series data. But Ecosim II does not just predict strong compensatory responses: it also suggests that large piscivores may be vulnerable to delayed recruitment collapses caused by increases in prey species that are in turn competitors/predators of juvenile piscivores. Received 24 February 1999; accepted 3 August 1999.     

Systematic deviations from linear size spectra of lake fish communities are correlated with predator–prey interactions and lake‐use intensity

Size structure of organisms at logarithmic scale (i.e. size spectrum) can often be described by a linear function with a negative slope; however, substantial deviations from linearity have often been found in natural systems. Theoretical studies suggest that greater nonlinearity in community size spectrum is associated with high predator–prey size ratios but low predator–prey abundance ratios; however, empirical evaluation of the effects of predator–prey interactions on nonlinear structures remains scarce. Here, we aim to empirically explore the pattern of the size‐specific residuals (i.e. deviations from the linear regression between the logarithmic fish abundance and the logarithmic mean fish size) by using size spectra of fish communities in 74 German lakes. We found that nonlinearity was strong in lakes with high predator–prey abundance ratios but at low predator–prey size ratios. More specifically, our results suggest that only large predators, even if occurring in low abundances, can control the density of prey fishes in a broad range of size classes in a community and thus promote linearity in the size spectrum. In turn, the lack of large predator fishes may cause high abundances of fish in intermediate size classes, resulting in nonlinear size spectra in these lakes. Moreover, these lakes were characterized by a more intense human use including high fishing pressure and high total phosphorus concentrations, which have negative impacts on the abundance of large, predatory fish. Our findings indicate that nonlinear size spectra may reflect dynamical processes potentially caused by predator–prey interactions. This opens a new perspective in the research on size spectrum, and can be relevant to further quantify the efficiency of energy transfer in aquatic food webs.     

Predicting the effects of exploitation on male-first sex-changing fish

Sex change is widespread among tropical marine fishes, many of which are targeted by fisheries. Conservation concerns have been raised that sex-changing species may be particularly prone to overexploitation by size-selective fishing. In the case of male-first sex-changers, populations may become egg limited if large females are disproportionately killed. However, if males reduce the size at which they change sex in response to higher female mortality, the population may still be sufficiently productive. We develop an age-based model to explore the effects of fishing on two types of male-first sex-changing fish: one with flexibility in size-at-sex-change and one without. These effects were compared with those of non-sex-changing populations with similar life-history and population characteristics. The model predicts that if male-first sex-changers cannot respond to elevated female mortality by adjusting their size-at-sex-change, the population will be more prone to recruitment limitation and extinction than non-sex-changers. These effects will be amplified as smaller individuals become susceptible to fishing mortality. However, if size-at-sex-change is flexible, sex-changers may be as resilient to fishing as non-sex-changers. Knowledge of a species' size-at-sex-change, and the mechanisms controlling it, should be fundamental to the selection of fisheries conservation strategies.     

Prey Selection,Vertical Migrations and the Impacts of Harvesting Upon the Population Dynamics of a Predator-Prey System

A model is developed to describe the interaction between a predator and two prey types located in different regions. Conditions for stability and persistence are analysed. The effects of harvesting the predators are investigated by making the predator mortality rate habitat dependent. Results demonstrate that for any given set of parameter values there is a value of the intrinsic preference of the predator for each prey type at which the system undergoes a Hopf bifurcation. Above this critical value the system evolves towards a stable equilibrium, whereas below it, stable limit cycles arise by Hopf bifurcations. Simulations demonstrate that the presence of demographic stochasticity may destabilise oscillatory populations, thereby causing population extinctions. An application of the model to the foraging behaviour of North Sea cod is described. It is shown that if the preferred prey is more productive, it is likely that the equilibrium will be stable, whereas if the less preferred prey is more productive, populations are likely to display cycles and in the stochastic case become extinct. As cod fishing mortality is increased, the point of bifurcation and region of parameter space for which the system is unstable decreases. An increased understanding of how cod behave may enable fish stocks to be managed more successfully, for example by indicating where marine reserves should be placed.     

Effects of prey size structure and turbulence on feeding and growth of anchovy larvae

Foraging processes in plankton and planktivorous fish are constrained by relative prey and predator size and therefore, these are important variables to include in a foraging model. The distribution of prey biomass across different size classes can be characterized by a size spectrum slope. We present a foraging model for anchovy larvae including the most relevant processes such as prey encounter, capture- and pursuit success, all influenced by light, turbulence and prey characteristics. We modelled ingestion rates and specific growth rate by coupling the foraging model with an existing bioenergetic model, and performed a sensitivity analysis of prey ingestion in turbulent environments assuming either hemispherical or conical perceptive volume. Our results suggest that turbulence has no positive effect because of the low capture ability, small prey size and small visual volume for anchovy larvae. The predicted ingestion is too low to sustain the growth potential of larvae when assuming conical perceptive volume even under prey densities substantially higher than normally found in the field. Ingestion rate is sensitive to the total biomass and the slope of the prey size spectra, specifically because it determines the abundance of prey around the optimal size for the larvae. The model also suggests that small larvae benefit from a prey size structure with steep prey size-spectra slope while a large larva benefit from less steep slopes. The model can act as a link between size-spectra measurements from the field and the foraging conditions of larval anchovies.     

Fishing with a Bait or Lure: A Brief Review of the Cognitive Issues

Bait fishing is a behaviour described in only 12 species of birds, seven of which belong to the family Ardeidae (herons), the remaining five are scattered among four other bird families. This behaviour is defined as having the following characteristics: (1) Objects placed by the bait fisher on the water are buoyant and within a radius at which the fisher can strike at prey. (2) The objects attract or distract the fisher’s prey, with the effect that the fisher enhances its chances of prey capture. A review of the literature indicates that bait items are both selected from and placed within the environment to achieve enhanced prey capture success. It is concluded that bait fishing is a real and distinctive behaviour. The evolutionary route to bait fishing has most likely been through an association between particular floating objects and the occurrence of fish prey. The repositioning of these floating objects and the collection of objects of similar character would have then been sufficient to achieve the bait fishing behaviour now seen. Bait fishing falls within a commonly used definition of tool use. However, it is argued that, as with tool use and tool making in general, this does not necessarily imply special cognitive ability. The rare occurrence of bait fishing both within and across species as could be an indication of cognitive constraint; but this remains undemonstrated. Alternatively, this rarity could be explained if fishing is rarely more profitable than alternative foraging tactics.     

An overview of the multispecies VPA — theory and applications

Summary Multispecies virtual population analysis is an attempt to take species interactions into account when assessing the status of fish stocks. It was introduced primarily with the aim of lowering the uncertainty in the natural mortality rate as used in single species VPA and to take account of variability between years and ages by calculating inside the model the part of the mortality rate caused by predation. The output of the MSVPA is therefore —in addition to stock sizes and fishing mortality rates as in single species VPA —the amounts consumed of the various species by the predators included in the analysis.The MSVPA model of the predation interactions results in a set of coupled non-linear equations which must be solved for each time step in the analysis. Key parameters in the model are the so-called suitability coefficients, measuring the relative suitability of one species as prey for another species. These parameters must be estimated inside the model and this estimation requires data on the stomach contents of the predators in the model. The MSVPA makes two key assumptions: constant ration size (i.e. independent of time for each species-age combination) and hence fixed weights-at-age and a model of prey selection which leads to a type ii functional feeding response. These assumptions do not hold for all areas and therefore limit the applicability of the MSVPA in its present form.The MSVPA is probably one of the more successful multispecies models in fisheries. Its main application to date has been to the North Sea, and although it has not been used directly as a management tool it has provided input values of parameters used in assessment models as well as valuable insights into the system. For example, it has demonstrated that an increase in mesh size can result in lower long-term yields, an effect opposite to what is predicted if species interactions are ignored. Such insights into the dynamics of the system are useful and MSVPA may therefore have an indirect role to play in management. Nevertheless, due to many uncertainties involved in multispecies modelling in general and MSVPA in particular, it seems doubtful that the use of MSVPA in fisheries management will be much greater in the immediate future than it is at present.     

Antagonistic Selection or Trait Compensation? Diverse Patterns of Predation-Induced Prey Mortality due to the Interacting Effects of Prey Phenotype and the Environment

Differentiation among closely related prey species may result from differing adaptations to heterogeneous environments. Many studies have focused on competition for shared resources as a major factor promoting differentiation, with considerably less attention focused on interacting effects of abiotic factors and predator–prey relationships. To further investigate the effects of interacting selective factors on the outcomes of mortality and survival in aquatic prey, we conducted interrelated laboratory studies examining the effects of water colour and plant density on predator-induced mortality in four dytiscid species (Coleoptera: Dytiscidae) that varied in body size (total body length), and body colouration pattern. Body size was more strongly phylogenetically conserved than colouration pattern, and larger body size generally resulted in decreased predator-induced mortality rates. In contrast, the effectiveness of body colouration patterns in decreasing prey mortality risk depended on water colour and prey body size. In clear water, small and patterned dytiscids had mortality rates equal to medium-sized plain beetles, thereby compensating for differences in mortality risk due to body size differences. Under dark water conditions, small dytiscids experienced higher mortality rates compared to medium-sized dytiscids; however, the effectiveness of colouration patterns in medium-sized beetles decreased to the point that it became detrimental to survival, revealing antagonistic selection. We suggest that colouration patterns are not ubiquitous in prey species and cospecialization in larger size and presence of colouration patterns does not generally result in higher prey survival, because the effectiveness of the two antipredator defences may be restricted to certain phenotype × environment combinations. Our results illustrate how interactions between prey phenotype and variable environmental conditions among habitats dominated by the same predator can lead to adaptive trade-offs, which can increase the number of possible outcomes of predator mediated selection.     

The significance of variable and density-independent post-recruitment mortality in local populations of reef fishes

Abstract In this paper I focus on how post-settlement mortality may modify initial patterns of settlement in reef fish. Infrequent recruitment surveys may underestimate the role of early post-settlement mortality as most mortality in reef fishes occurs shortly after settlement. Consequently, results from infrequent recruitment surveys shed little light on the mechanisms producing patterns of abundance because these surveys ignore early post-settlement mortality. Variation in density-independent mortality may be a common mechanism that can prevent a positive relationship between larval settlement and subsequent population abundance. Although density-dependent mortality is the most commonly recognized mechanism that can disrupt the correlation between settlement and adult abundance, density-independent mortality’ can also destroy this correlation if the variance associated with post-settlement mortality is greater than variance in settlement. This point is illustrated with a simulation model in which I modelled two populations: a piscivorous fish population that was recruitment-limited with constant mortality, and a prey population that had variable recruitment and mortality that was a function of the size of the predator population. The results of this model indicate that even when mortality of prey is density-independent, predation can determine prey abundance when variation in piscivore recruitment is high relative to prey recruitment. Thus, initial patterns of prey settlement can be modified by a recruitment-limited predator population.     

Consequences of size structure in the prey for predator-prey dynamics: the composite functional response

1. Current formulations of functional responses assume that the prey is homogeneous and independent of intraspecific processes. Most prey populations consist of different coexisting size classes that often engage in asymmetrical intraspecific interactions, including cannibalism, which can lead to nonlinear interaction effects. This may be important as the size structure with the prey could alter the overall density-dependent predation rates. 2. In a field experiment with damselfly and dragonfly larvae, 16 treatments manipulated the density of a small prey stage, the presence of large conspecific prey and the presence of heterospecific predators. 3. Size structure in the prey (i.e. when both prey stages were present) decreased the impact of the predator on overall prey mortality by 25-48% at mid and high prey densities, possibly due to density-dependent size-structured cannibalism in the prey. The predation rates on small prey stages were determined by the interaction of large prey and predators. Predation rates increased with prey density in the absence of large prey, but predation rates were constant across densities when large conspecifics were present. 4. The functional response for unstructured prey followed a Holling type III model, but the predation rate for size-structured prey was completely different and followed a complex pattern that could not be explained with any standard functional response. 5. Using additional laboratory experiments, a mortality model was developed and parameterized. It showed that the overall prey mortality of size-structured prey can be adequately predicted with a composite functional response model that modelled the individual functional responses of each prey stage separately and accounted for their cannibalistic interaction. 6. Thus, treating a prey population as a homogeneous entity will lead to erroneous predictions in most real-world food webs. However, if we account for the effects of size structure and the intraspecific interactions on functional responses by treating size classes as different functional groups, it is possible to reliably predict the dynamics of size-structured predator-prey systems.     

Predator-induced demographic shifts in coral reef fish assemblages

In recent years, it has become apparent that human impacts have altered community structure in coastal and marine ecosystems worldwide. Of these, fishing is one of the most pervasive, and a growing body of work suggests that fishing can have strong effects on the ecology of target species, especially top predators. However, the effects of removing top predators on lower trophic groups of prey fishes are less clear, particularly in highly diverse and trophically complex coral reef ecosystems. We examined patterns of abundance, size structure, and age-based demography through surveys and collection-based studies of five fish species from a variety of trophic levels at Kiritimati and Palmyra, two nearby atolls in the Northern Line Islands. These islands have similar biogeography and oceanography, and yet Kiritimati has ～10,000 people with extensive local fishing while Palmyra is a US National Wildlife Refuge with no permanent human population, no fishing, and an intact predator fauna. Surveys indicated that top predators were relatively larger and more abundant at unfished Palmyra, while prey functional groups were relatively smaller but showed no clear trends in abundance as would be expected from classic trophic cascades. Through detailed analyses of focal species, we found that size and longevity of a top predator were lower at fished Kiritimati than at unfished Palmyra. Demographic patterns also shifted dramatically for 4 of 5 fish species in lower trophic groups, opposite in direction to the top predator, including decreases in average size and longevity at Palmyra relative to Kiritimati. Overall, these results suggest that fishing may alter community structure in complex and non-intuitive ways, and that indirect demographic effects should be considered more broadly in ecosystem-based management.     

Estimating predation rates in experimental systems: scale-dependent effects of aggregative behaviour

We studied the effect of arena size on estimates of prey mortality rate in predation experiments. In a laboratory experiment involving two of the dominating benthic species in the northern Baltic Sea, the predacious isopod Saduria entomon , and its main prey, the amphipod Monoporeia affinis , the prey mortality rate increased with container radius. The densities of both predator and prey close to the wall increased with container size. We hypothesised that this scale-dependent coaggregation of predator and prey caused the mortality rates to increase with arena size. We tested the hypothesis with the help of a simple model, by calculating the expected number of prey eaten in containers of different size from experimental data on the distributions of predator and prey within the arenas. A significant relationship between expected and observed numbers eaten supported our hypothesis. As the aggregative response was most pronounced in large arenas, this leads to the counterintuitive conclusion that large containers produced more biased estimates of morality rates than small containers.
To further study the effects of coaggregation we explored a general simulation model where both predator and prey preferred the habitat close to the arena wall. The model predicted a humpshaped relationship between encounter rate and arena size. This suggests that when predators and prey show a scale-dependent tendency to aggregate along arena walls, the most accurate estimates of predation rates may be obtained with very small or very large arenas.     

Prey size spectra and prey availability of larval and small juvenile cod

The aim of the present study is to describe the prey preference characteristics of cod larvae and assess preference variability in relation to species and size composition of copepod prey. A further aim is to examine the hypothesis that dietary prey size spectra remain the same during the larval stage when viewed on a relative predator/prey size scale. The study is based on stomach analysis of larval/juvenile cod in the size range 10–35 mm from nursery grounds in the North Sea. Stomach contents (species, size) were compared to environmental composition and preference indices were calculated. Prey size spectra had the expected relationship to larval cod size, and preference for given copepod species could be ascribed to their relative size. Additional species-specific preferences were evident, for example the larger Pseudocalanus and the larger Calanus spp. were highly preferred. Available prey biomass was highest in the areas of a hydrographic front, where larvae have been shown to concentrate. Changes in prey availability with larval growth depend strongly on specific prey biomass spectra at a given location. Both increasing and decreasing prey availability at increasing larval size were indicated, dependent on location. The findings illustrate the usefulness of coupling dietary prey size spectra and biomass spectra of available prey sizes during studies of ichthyoplankton feeding ecology.     

The impact of mortality on predator population size and stability in systems with stage-structured prey

The relationships between a predator population's mortality rate and its population size and stability are investigated for several simple predator-prey models with stage-structured prey populations. Several alternative models are considered; these differ in their assumptions about the nature of density dependence in the prey's population growth; the nature of stage-transitions; and the stage-selectivity of the predator. Instability occurs at high, rather than low predator mortality rates in most models with highly stage-selective predation; this is the opposite of the effect of mortality on stability in models with homogeneous prey populations. Stage-selective predation also increases the range of parameters that lead to a stable equilibrium. The results suggest that it may be common for a stable predator population to increase in abundance as its own mortality rate increases in stable systems, provided that the predator has a saturating functional response. Sufficiently strong density dependence in the prey generally reverses this outcome, and results in a decrease in predator population size with increasing predator mortality rate. Stability is decreased when the juvenile stage has a fixed duration, but population increases with increasing mortality are still observed in large areas of stable parameter space. This raises two coupled questions which are as yet unanswered; (1) do such increases in population size with higher mortality actually occur in nature; and (2) if not, what prevents them from occurring? Stage-structured prey and stage-related predation can also reverse the 'paradox of enrichment', leading to stability rather than instability when prey growth is increased.     

A Concept of Bayesian Regulation in Fisheries Management

Stochastic variability of biological processes and uncertainty of stock properties compel fisheries managers to look for tools to improve control over the stock. Inspired by animals exploiting hidden prey, we have taken a biomimetic approach combining catch and effort in a concept of Bayesian regulation (BR). The BR provides a real-time Bayesian stock estimate, and can operate without separate stock assessment. We compared the performance of BR with catch-only regulation (CR), alternatively operating with N-target (the stock size giving maximum sustainable yield, MSY) and F-target (the fishing mortality giving MSY) on a stock model of Baltic Sea herring. N-targeted BR gave 3% higher yields than F-targeted BR and CR, and 7% higher yields than N-targeted CR. The BRs reduced coefficient of variance (CV) in fishing mortality compared to CR by 99.6% (from 25.2 to 0.1) when operated with F-target, and by about 80% (from 158.4 to 68.4/70.1 depending on how the prior is set) in stock size when operated with N-target. Even though F-targeted fishery reduced CV in pre-harvest stock size by 19–22%, it increased the dominant period length of population fluctuations from 20 to 60–80 years. In contrast, N-targeted BR made the periodic variation more similar to white noise. We discuss the conditions when BRs can be suitable tools to achieve sustainable yields while minimizing undesirable fluctuations in stock size or fishing effort.