Jarl Giske

University of Bergen | UiB · Dept of Biological Sciences

Abstract A central simplifying assumption in evolutionary behavioral ecology has been that optimal behavior is unaffected by genetic or proximate constraints. Observations and experiments show otherwise, so that attention to decision architecture and mechanisms is needed. In psychology, the proximate constraints on decision making and the processes...

Organisms have evolved to trade priorities across various needs, such as growth, survival, and reproduction. In naturally complex environments this incurs high computational costs. Models exist for several types of decisions, e.g., optimal foraging or life history theory. However, most models ignore proximate complexities and infer simple rules spe...

Evolutionary ecology often studies how environmental factors define optimal phenotypes without considering the bodily mechanisms involved in their regulation. Here we used a dynamic optimisation model to investigate optimally concerted hormonal control of the phenotype. We studied a semi‐realistic situation where hormonal control of appetite, metab...

Growth is an important theme in biology. Physiologists often relate growth rates to hormonal control of essential processes. Ecologists often study growth as a function of gradients or combinations of environmental factors. Fewer studies have investigated the combined effects of environmental and hormonal control on growth. Here, we present an evol...

Unified theories of cognition have traditionally played a vital role in understanding the human mind. In the animal behavior field, however, acceptance of holistic views on the behavioral phenotype that includes diverse cognitive and behavioral traits is rather slow. Studying adaptation and evolution of behavior, especially complex cognition and de...

Using a dynamic optimisation model for juvenile fish in stochastic food environments, we investigate optimal hormonal regulation, energy allocation and foraging behaviour of a growing host infected by a parasite that only incurs an energetic cost. We find it optimal for the infected host to have higher levels of orexin, growth and thyroid hormones,...

Scientific awareness of social learning, especially among vertebrates, has expanded rapidly in recent decades. That literature suggests that social learning may be a second adaptive mechanism that interacts with and refines genetic adaptation. For an individual fish, learning from others reduces the costs of acquiring experience-based behaviors and...

Using a dynamic optimisation model for juvenile fish in stochastic food environments, we investigate optimal hormonal regulation, energy allocation and foraging behaviour of a growing host infected by a parasite that only incurs an energetic cost. We find it optimal for the infected host to have higher levels of orexin, growth- and thyroid hormones...

To understand animal wellbeing, we need to consider subjective phenomena and sentience. This is challenging, since these properties are private and cannot be observed directly. Certain motivations, emotions and related internal states can be inferred in animals through experiments that involve choice, learning, generalization and decision-making. Y...

To understand animal wellbeing, we need to consider subjective phenomena and sentience. This is challenging, since these properties are private and cannot be observed directly. Certain motivations, emotions and related internal states can be inferred in animals through experiments that involve choice, learning, generalization and decision-making. Y...

The Overview, Design concepts and Details (ODD) protocol for describing Individual- and Agent-Based Models (ABMs) is now widely accepted and used to document such models in journal articles. As a standard- ized document for providing a consistent, logical and readable account of the structure and dynamics of ABMs, some research groups also find it...

During the past 50 years, evolutionary theory for animal behaviour has branched into different methodological frameworks focussing on age-, state-, density-, and frequency-dependent processes. These approaches have led to valuable insights in optimal responses, state dependent choices, and behavioural strategies in social contexts. We argue that ti...

Discussions about limiting anthropogenic emissions of CO 2 often focus on transition to renewable energy sources and on carbon capture and storage (CCS) of CO 2 . The potential contributions from forests, forest products and other low-tech strategies are less frequently discussed. Here we develop a new simulation model to assess the global carbon c...

Evolution has since the very beginning resulted in organisms which can sort fitness-related information from noise, evaluate it and respond to it. In animals, the architecture for proximate control of behaviour and physiology has been gradually evolving since before the Cambrian explosion of animal phyla. It integrates many different survival circu...

Growth and survival of Maurolicus muelleri larvae in Herdlefjorden, Norway, were investigated by daily otolith increment analysis. While high egg densities were generally observed throughout the spawning season, three cohorts each with a narrow window of hatching dates were identified. The first of these cohorts was characterized by low growth and...

Theoretical work has suggested an important role of lytic viruses in controlling the diversity of their prokaryotic hosts. Yet, providing strong experimental or observational support (or refutation) for this has proven evasive. Such models have usually assumed " host groups " to correspond to the " species " level, typically delimited by 16S rRNA g...

Studies on the relationship between the optimal phenotype and its environment have had limited focus on genotype-to-phenotype pathways and their evolutionary consequences. Here, we study how multi-layered trait architecture and its associated constraints prescribe diversity. Using an idealized model of the emotion system in fish, we find that trait...

Trophic mechanisms that can generate biodiversity in food webs include bottom-up (growth rate regulating) and top-down (biomass regulating) factors. The top-down control has traditionally been analyzed using the concepts of "Keystone Predation" (KP) and "Killing-the-Winner" (KtW), predominately occuring in discussions of macro- and micro-biological...

Marine ecosystem acoustics (MEA): quantifying processes in the sea at the spatio-temporal scales on which they occur. – ICES Journal of Marine Science, doi: 10.1093/icesjms/fsu116. Sustainable management of fisheries resources requires quantitative knowledge and understanding of species distribution, abundance, and prod-uctivity-determining process...

Significance This work presents the first detailed analysis to the authors’ knowledge of how species-level diversity is a property emerging from competitive and defensive abilities at the organism level in a microbial system where the diversity-generating mechanism is strain-specific viral lysis. The theoretical analysis constitutes a general case...

Ecologists urgently need a better ability to predict how environmental change affects biodiversity. We examine individual-based ecology (IBE), a research paradigm that promises better a predictive ability by using individual-based models (IBMs) to represent ecological dynamics as arising from how individuals interact with their environment and with...

This study investigates how food web structures in aquatic microbial communities emerge based on different mixotrophic life strategies. Unicellular mixotrophic organisms that combine osmotrophy and primary production with phagotrophy account for significant amounts of primary production and bacterivory in marine environments, yet mixotrophs are sti...

We present a new individual-based approach to model populations of largely inhomogeneous densities. By monitoring different populations at a spatial scale which is inversely proportional to the maximum expected concentration, the Scaled Subspaces Method solves the problem of demographic explosion of the most numerous species. It is intuitively simi...

Optimal life histories in a fluctuating environment are likely to differ from those that are optimal in a constant environment, but we have little understanding of the consequences of bounded fluctuations versus episodic massive mortality events. Catastrophic disturbances, such as floods, droughts, landslides and fires, substantially alter the popu...

Ecological Modelling j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / e c o l m o d e l a b s t r a c t The 'ODD' (Overview, Design concepts, and Details) protocol was published in 2006 to standardize the published descriptions of individual-based and agent-based models (ABMs). The primary objectives of ODD are to mak...

The value of acquiring environmental information depends on the costs of collecting it and its utility. Foragers that search for patchily distributed resources may use experiences in previous patches to learn the habitat quality and adjust their behavior. We map the ecological landscape for the evolution of learning under a range of conditions, inc...

Society has learned that there can be big pay-offs from science. Governments, private companies and funding agencies will therefore want to know whether their investments in research are well placed. As long as scientists ask for funding support, we must accept the right of these agen- cies to ask for proof of results. Within a department, the eval...

IntroductionSpecifying Individuals in IBMsFeatures of Individual—Based ModelsFormulating and Testing IBMSReview of Individual—Based Models in Fisheries BiologyConclusions AcknowledgementsReferences

The acquisition of information is a fundamental part of individual foraging behaviour in heterogeneous and changing environments. We examine how foragers may benefit from utilizing a simple learning rule to update estimates of temporal changes in resource levels. In the model, initial expectation of resource conditions and rate of replacing past in...

Question: To what extent can learning facilitate group formation in a social forager? Model features: An individual-based simulation model is used to explore frequency-and density-dependent interactions between mobile learners and non-selective stayers that forage in a patchy resource environment. Key assumption: Foraging efficiency peaks at interm...

Simulation models that describe autonomous individual organisms (individual based models, IBM) or agents (agent-based models, ABM) have become a widely used tool, not only in ecology, but also in many other disciplines dealing with complex systems made up of autonomous entities. However, there is no standard protocol for describing such simulation...

The life history and vertical distribution of a female cohort of the mesopelagic fish Maurolicus muelleri is simulated using stochastic dynamic programming. The environment is represented by vertical profiles of zooplankton biomass, light intensity and temperature, all variables changing with season. The fish physiology is modelled by dynamic state...

Organisms in nature are both proximate (operating by rules of thumb) and adapted (the rules influenced by natural selection). We introduce new methods that can be used to study in silico versions of organisms behaving according to proximate adapted rules. Our approach goes beyond neural networks and offers an alternative to optimization methods. It...

Growth and survival through the early larval phase probably limit the production potential of many commercially important fish stocks. Attempts to increase the production of these stocks by restocking of juveniles have generally failed. Here, we analyse how enhanced concentrations of phytoplankton and zooplankton affect the survival of fish larvae...

We present an individual-based model that uses artificial evolution to predict fit behavior and life-history traits on the basis of environmental data and organism physiology. Our main purpose is to investigate whether artificial evolution is a suitable tool for studying life history and behavior of real biological organisms. The evolutionary adapt...

The state of the art in spatial modelling in physical and biological oceanography is reviewed in light of its relevance for marine resource management, based on discussions during a workshop in marine spatial modelling. The quality of the spatial models strongly depends on the assimilation of data. With the present level of investment in modelling...

We describe broadly applicable principles for the conservation of wild living resources and mechanisms for their implementation. These principles were engendered from three starting points. First, a set of principles for the conservation of wild living resources (Holt and Talbot 1978) required reexamination and updating. Second, those principles la...

This chapter discusses the models dealing with marine mesozooplankton, and partially discusses the models dealing with limnic zooplankton, fish larvae, and meroplanktonic larvae. The chapter aims to present detailed, specific applications of models on bioenergetics or demography of zooplankton, rather than a general mathematical study of modeling....

We evaluated the costs and benefits of long-distance horizontal migration by pelagic planktivores, Atlantic herring (Clupea harengus), blue whiting (Micromesistius poutassou), mackerel (Scomber scombrus), and capelin (Mallotus villosus) in the Norwegian and Barents seas using a numerical model and tested model predictions against field observations...

Even though individual-based models (IBMs) have become very popular in ecology during the last decade, there have been few attempts to implement behavioural aspects in IBMs. This is partly due to lack of appropriate techniques. Behavioural and life history aspects can be implemented in IBMs through adaptive models based on genetic algorithms and ne...

A conceptual approach to study spatial movements of fish using an individual-based neural network genetic algorithm model is presented. Artificial neural networks, where the weights are adapted using a genetic algorithm, are applied to evolve individual movement behaviour in a spatially heterogeneous and seasonal environment. A 2D physical model (f...

Our ability to model spatial distributions of fish populations is reviewed by describing the available modelling tools. Ultimate models of the individual's motivation for behavioural decisions are derived from evolutionary ecology. Mechanistic models for how fish sense and may respond to their surroundings are presented for vision, olfaction, heari...

Large fluctuations in the fisheries have been a characteristic feature of great importance in the history of the Norwegian people. Herring periods have been times with large fisheries for herring spawning along the west coast of Norway, alternating with periods when the herring was gone. Herring periods and periods without herring appear to have be...

The potential use of functional evolutionary models and mechanistic ecological models as predictive tools in fisheries ecology is discussed. Evolution by natural selection is a force that leads to ecological adaptations of the individuals in the populations. By mechanistic modelling of the sense organs, we may model how individuals perceive their e...

A mathematical model describing competition for a common food resource among visual and tactile planktivores is developed. Sensitivity of the competitive regime to environmental changes are studied by analysing their effects on foraging rates and niche availability of both planktivore types. Depth, spatial, daily and seasonal variations in factors...

Optimal vertical distribution of a copepod population of equal competitors under predation hazard is modelled by ideal free distribution (IFD). The foragers may be limited by both depletable (food) and non-depletable (temperature) resources. Individuals are assumed to maximize growth rate per mortality risk (g/M). Mortality risk is assumed density-...

The size, fecundity and gonad development of Maurplicus muelleri (Gmelin) were studied in Herdlefjorden, western Norway, from January to June 1994. In January, the two age groups formed separate sound-scattering layers (SSL). Juvenile 1-group fish were found to form the upper SSL, while adult 2+ individuals inhabited the lower, these distributions...

A gastric evacuation curve expresses how fast prey disappear from the stomach, and empirical models are used generally for the relationship between weight of prey remaining (Wt) and time (t) after a meal. Unfortunately, empirical models are likely to have restricted applicability because their parameters often represent limited biological mechanism...

The geographical distribution and production of the Barents Sea capelin (Mallotus villosus, Osmeridae) is modelled by the use of a state-variable optimization technique (dynamic programming), where the main objective of individuals always is to maximize fitness, or total expected reproduction (RO), by selecting the most profitable habitats through...

The influence of oceanographic and meteorological conditions and topography on the carrying capacity of organisms in coastal areas of western Norway is investigated by field studies and dynamic modelling. Published data on Calanus finmarchicus, the dominant species in the zooplankton biomass of west Norwegian coastal waters, demonstrate a strong gr...

Diet width theory is a branch of optimal foraging theory, used to predict which fractions of the potential food encountered should be pursued. For pelagic fish, it is generally assumed that light is the dominant stimulus for both prey encounter rate and mortality risk. In order to achieve encounter rates allowing selective feeding, the pelagic pred...

A stochastic dynamic optimization model for the diel depth distribution of juveniles and adults of the mesopelagic planktivore Maurolicus muelleri (Gmelin) is developed and used for a winter situation. Observations from Masfjorden, western Norway, reveal differences in vertical distribution, growth and mortality between juveniles and adults in Janu...

Population characteristics, individual life-history variables, feeding and vertical distribution of the mesopelagic fish Mller's pearlside Maurolicus muelleri collected in 1990 in Masfjorden, western Norway, are reported as well as environmental variables from the fjord. Minimum size at maturity was far smaller than reported from previous investiga...

Several aspects of zooplankton mortality risk (body size, inherent contrast, beam and diffuse light attenuation, depth, ambient light level, selectivity, predator saturation) are studied from a predator-prey encounter model where the predator is assumed to feed by vision. The steepness of the vertical gradient in risk decreases with zooplankton siz...

Optimal timing of juvenile releases in extensive cod mariculture can be investigated by adopting a theoretical framework based on evolutionary and ecological relationships. Optimal timing of release will generally be after cod have reached a size at which they settle to the benthic fjord habitat. -from Authors

A model for visual feeding by aquatic predators is derived. The predator's visual range, which depends on its visual capability, surface light, water clarity, and size and contrast of the prey, is emphasised. Central to the model is the assumption that a prey may be recognized only if the difference in retinal flux, with and without the prey image,...

Reproductive value (RV) and net reproductive output (R o) are frequently used fitness measures. We argue that they are only appropriate when intervals between reproductive events are fixed, as they are dimensionless generation-to-generation scalings with units offspring per parent. A fitness measure should account for two different effects of a dec...

Adult two-spotted gobies Gobiusculus flavescens (Fabricius) distributed themselves according to the Ideal Free Distribution (IFD) when 10 individuals were offered equal amounts of prey items at two sites in aquaria. As ratios between the prey supply at the two sites increased, however, increasing deviations from the IFD were observed. It is suggest...

To investigate the validity of static optimization models, the vertical distributions of two age groups of Maurolicus muelleri is compared to the optimal annual ontogenetic growth rate: mortality risk trade-offs as determined from generation-time based life-history equations. Calculations indicate that juvenile feeding rate was near the maximum for...

The carrying capacity for cod in a Norwegian fjord was analysed by means of a simulation model. Four age groups of cod were represented as well as the main prey groups labrids, gobies and benthic organisms. These groups made up a near-shore compartment of the model, while nutrients, phytoplankton, herbivorous, carnivorous and gelatinous zooplankton...

To support an assessment model, we propose a set of numerical models where distribution and growth of capelin (Mallotus villosus) is modelled by biological (evolutionary, ecological) and physical forces. The basics of a dynamic optimization fish distribution model is outlined. This model must be coupled to hydrodynamicallmeteorological (temperature...

Habitat profitability is analysed with a set of simple equations comprising predation risk, food availability, sex ratio, number of offspring per survivor, generation time and expected reproductive outcome. We show that organisms with fixed generation time should prefer hunger instead of increased feeding if the increase in feeding is associated wi...

The distribution, biomass, and predator-prey relationships of the pelagic assemblage in Masfjorden, western Norway, was studied in January 1989. The pelagic biomass was dominated by particulate organic matter. Biomasses of copepods, macroplankton, and mesopelagic fishes were of the same order of magnitude, while the biomass of larger pelagic fishes...

The "ODD" (Overview, Design Concepts, and Details) protocol was published in 2006 as a way to standardize the published descriptions of individual-based and agent-based models (ABMs). The primary objectives of ODD are making model descriptions more understandable and complete, thereby making ABMs less subject to criticism for being irreproducible....

A gastricevacuationcurveexpresseshow fastpreydisappearfrom thestomach,and empirical models areusedgenerallyfortherelationship between weightofpreyremaining(W t)and time (t)aftera meal. Unfortunately,empiricalmodels are likelyto have restricted applicability becausetheirparametersoftenrepresentlimitedbiological mechanisms . Thispaper developsa simpl...