Reaction Distance Research Articles

Ontogenetic changes in behavioural and histological measures of visual acuity in three species of fish

Vision plays an important role in the early life history of fishes. We investigated the ontogenetic changes in visual acuity of early life history stages of alewife,Alosa pseudoharengus, yellow perch,Perca flavescens and bloater,Coregonus hoyi, across a range of sizes. Acuities were determined through histological examination of the retinae of larvae. Reactive distances of larvae to prey were estimated through videophotography of their response to prey and were then converted to measurements of visual angle. Both measures of visual ability improved with size (age) for all species. When behavioural and anatomical measures of ability were compared as a function of size, the data indicate that fish are anatomically more capable of seeing objects than the behavioural response suggests. In two of the three species, the relationship between histological acuity and visual angle was not constant. These results may indicate that while vision may limit initial rates of encounter and feeding, increases in visual acuity mean that in older stages limitations on encounter and feeding are more likely to be behavioural. Furthermore, these results indicate that encounter rates based upon histological estimates of visual acuity will be greater than comparable estimates based upon reactive distances. We recommend calculation of encounter rates based upon reactive distances.

Low level infection by eye fluke, Diplostomum spp., affects the vision of three‐spined sticklebacks, Gasterosteus aculeatus

Experiments have shown thai infection by low intensities of the eye fluke affects the vision of three‐spined stickleback when selecting prey, and also shortens the reactive distance to the prey. The results have consequences for the fitness of the individual, and also for the study of prey selection.

Low level infection by eye fluke, Diplostomum spp., affects the vision of three-spined sticklebacks, Gasterosteus aculeatus

Experiments have shown thai infection by low intensities of the eye fluke affects the vision of three-spined stickleback when selecting prey, and also shortens the reactive distance to the prey. The results have consequences for the fitness of the individual, and also for the study of prey selection.

Diel feeding behavior in larvae of four odonate species

The diel feeding behavior of four coexisting odonate larvae, Aeshna juncea, Coenagrion hastulatum, Cordulia aenea,and Leucorrhinia dubiawas studied in the laboratory. C. hastulatumand L. dubiawere equally active during day and night. While C. hastulatumconsumed an equal number of prey during day and night, L. dubiaconsumed more prey during night. In contrast, A. juncealarvae were most active and consumed more prey during day, while C. aenealarvae were most active and consumed more prey during night. In contrast to the other three species, A. junceashowed a longer reactive distance under light conditions. In A. junceaand L. dubiacapture efficiency was higher under light conditions, whereas in C. hastulatumand C. aeneait was the same irrespective of illumination. The results show that the time niche is an important component of the feeding in this guild.

Turbidity-Induced Changes in Reactive Distance of Rainbow Trout

We used artificial stream channels to conduct feeding trials with wild rainbow trout Oncorhynchus mykiss at three levels of suspended sediment. To examine the effects of turbidity on reactive distance and pursuit speed, we fed rainbow trout (87–185 mm standard length) pieces of mealworms Tenebrio sp. as test prey. A video camera system was used to record the pursuit speed and reactive distance of fish during foraging bouts. Turbidity had a consistent and negative effect on reactive distance (analysis of variance, P < 0.05). On average, reactive distances in the 15- and 30-NTU (nephelometric turbidity units) treatments were only 80% and 45%, respectively, of those observed at ambient turbidities (4–6 NTUs). By contrast, turbidity did not significantly affect pursuit speed. Pursuit speed varied greatly among individuals but was similar for each fish across turbidity levels. These results indicate that sediment-producing activities, such as logging and road building, could reduce foraging success within trout populations.

Turbidity-induced changes in feeding strategies of fish in estuaries

The aim of this study was to determine the effect of turbidity on the feeding strategies of fish in estuaries. Three species representing different feeding guilds were selected for the investigation. These were Elops machnata (representative piscivore), Pomadasys commersonnii (a macrobenthivore) and Atherina breviceps (a planktivore). The stomach contents of these fish were examined from a clear and a turbid estuary and some experimental work was carried out on A breviceps to test the hypothesis that turbidity affects feeding behaviour. Turbidity was found to have no effect on size selection of prey, but feeding rate, particularly of visual predators, was reduced at higher turbidity levels. This was caused by a decrease in the reactive distance of the fish. It would appear that in order to optimize the aquisition of food under different turbidity conditions fishes have the ability to change their feeding strategies. Visual predators are more affected by turbidity than are macrobenthic feeders.

Influence of temperature on evasive responses of Atlantic herring larvae attacked by yearling herring, Clupea harengus L.

Predation encounters were staged in the laboratory between yearling herring, Clupea harengus L., 66 to 104 mm t.l., and herring larvae, 8 to 30 mm t.l.., at 8,11 and 14o C. Video records were used to quantify prey behaviour. Prey responsiveness, reactive distance, response latency, and apparent looming threshold were not affected by temperature. Response speeds increased with temperature. Predator error rate and capture success showed no consistent thermal effects. Although the experiments could not fully evaluate the influence of temperature on the predators, results suggest that the predator's performance largely governs the outcome of an attack on a larva and that higher temperatures favour the predator by increasing the frequency of its encounter with prey.

Chemical composition of midwater fishes as a function of depth of occurrence off the Hawaiian Islands: Food availability as a selective factor?

The variation with depth in water, lipid, protein, carbon and nitrogen contents (% wet weight) of 42 species of midwater fishes, collected in November 1976 off the west coast of Oahu in the Hawaiian Archipelago, was measured. The Hawaiian fishes show significant relationships between these components and depth of occurrence. The slopes of these relationships are not significantly different from those reported for midwater fishes from off California, USA. However, the fishes from Hawaii have significantly lower lipid levels and higher protein levels than do the species from off California. The deep-living Hawaiian species (500 m and deeper) have significantly lower lipid (% wet weight), but there is no significant difference in protein (% wet weight). The difference in lipid contents at all depths appears to be an evolved characteristic, with the greater lipid levels off California being selected for by greater spatial and temporal variation in the food supply for these fishes off the California coast than off Hawaii. The higher protein contents in the shallow-living Hawaiian fishes appear to reflect greater muscle power selected for in these fishes by the greater water clarity, and therefore greater “reactive distances”, in the surface layers off Hawaii. These conclusions support the general hypothesis that the lower protein contents of bathypelagic fishes are not directly selected by food limitation at depth, but rather result from the relaxation of selection for rapid-swimming abilities at greater depths due to the great reduction at greater depths in the distance over which visual predator-prey interactions can take place. The lower lipid levels in the deeper-living species are apparently made possible by the reduced metabolic rates of these species which reduces their need for energy stores.

Effects of crayfish size, orientation, and movement on the reactive distance of largemouth bass foraging in clear and turbid water

Laboratory experiments were performed in clear and turbid water to determine the effects of prey size, orientation, and movement on the reactive distance of largemouth bass (Micropterus salmoides) when feeding on crayfish (Procambarus acutus). In clear water, the reactive distance increased linearly with an increase in prey size, and prey movement resulted in a significant increase in the reactive distance. Prey orientation (head-on versus perpendicular) did not change the reactive distances. In moderately turbid water, the reactive distance did not increase with increased prey size, and prey movement did not result in any changes in the reactive distance. The absence of any effects of prey orientation in clear water or prey movement in turbid water is inconsistent with results from studies using different species (primarily planktivorous fish). I propose that largemouth bass change their foraging tactics as prey visibility changes. When prey are highly visible (low turbidity), predators attack (react) only after prey recognition, which is based on multiple cues such as prey size (length, width) and movement. When prey are less visible (high turbidity), predators attack immediately upon initial prey sighting, which does not depend on prey size or movement.

Prey Detection in Cyprinids during Early Development

Larval and juvenile fish of roach (Rutilus rutilus L), bleak (Alburnus alburnus L), and blue bream (Abramis ballerus L.) were investigated weekly to define the ontogenetic development of prey detection capacities. Visual acuity was determined by measuring reactive distances for zooplankton prey for fish from 8 to 50 mm standard length using video recordings. Data of reactive distances, swimming speeds, and the characteristics of the visual field were combined to calculate prey location volumes. Prey location capacity increased exponentially with fish size which implies enormous differences in prey encounter rates among size classes of cyprinids. Distinct differences of prey location capacities occurred between species in the juvenile, planktivorous stages of the three cyprinids coinciding with the trophic differentiation of the adults.

Early Warning Lowers Risk of Stonefly Predation for a Vulnerable Mayfly

Behavior of Baetis bicaudatus (Ephemeroptera; Baetidae) was video taped in a western Colorado, USA stream to identify the specific stimuli eliciting noncontact responses to predatory stoneflies (Kogotus modestus; Plecoptera; Perlodidae). In situ behavioral and feeding trial experiments were also conducted to assess the effect of removal of Baetis cerci on these responses to predators, on measured reactive distances, and on the vulnerability of Baetis to stonefly predation. Predatory stimuli tested included live stoneflies (tethered and untethered), stonefly models (plasticized), excised fresh stonefly antennae, and wires. Intact Baetis primarily turned their cerci (tail curl behavior) with similar frequencies toward live or model stoneflies that were between 1 and 2 cm downstream, and primarily moved when stoneflies were within 1 cm even before contact. Removal of Baetis' cerci reduced the frequency of tail curl responses and the reactive distance, but increased the frequency of movement responses to noncontact with Kogotus. Neither intact nor cerciless Baetis showed much response to Kogotus antennae and wires. These results suggest that stimuli associated with the whole stonefly, such as visual or more probably hydrodynamic cues, cause Baetis tail curl behavior. However, movement behavior was uniformly high after contact with all predator treatments, and the pattern of movement (swim, drift or crawl) varied with predator stimulus, suggesting that Baetis can discriminate live or model Kogotus, Kogotus antennae, and wires using chemotactile or tactile cues. Removal of Baetis cerci resulted in increased encounter rates (contact) with live, untethered Kogotus, higher capture success, and greater predation rates than on intact Baetis. When touched by all predator treatments, Baetis usually swam, a behavior that stimulates stonefly attacks, but after noncontact tail curl responses, Baetis most often remained stationary. Thus, cerci were apparently effective as an early warning system, enabling Baetis to detect Kogotus before contact, thereby reducing the incidence of dangerous swimming escape behavior, and the susceptibility to predation.

12th Annual Larval Fish Conference Formulation of a Bioenergetic Model for Coregonine Early Life History

Abstract A physiological basis for correlations among type of metabolism, behavior, and lifestyle is described for two early ontogenetic stages of coregonine fishes. Stage I extends from first feeding attempts until the end of metamorphosis, which usually occurs at a total length of 2–3 cm. Stage II extends through the juvenile period to a size of 8–10 cm. During the change from stage 1 to stage II, activities of several glycolytic and muscle enzymes increase severalfold. This increase in enzyme activities indicates a switch in major energy substrates from fatty and amino acids to glycogen. Prey selection data (prey ranked by size and mode of swimming), predator–prey reactive distance, and prey-handling time per unit energy return (profitability time) are given for coregonines in stages I and II. Results from studies of coregonine species from many different locations are incorporated into a deterministic model to estimate relationships between physical and biological environmental factors and fish growth...

A mathematical model of realistic constitutional chemistry. A synthon approach. I: An algebraic model of a synthon

A mathematical model of a synthon is suggested. The synthon is modelled by a special so-calledS-matrix. The notion of isomeric synthons on the set of atoms A and that of a Family of Isomeric SynthonsFIS (A) is introduced. The chemical reaction is represented by a matrix equation and it is modelled by the so-calledSR-matrix. The notion of the reaction distance (RD) between two isomeric synthons is defined. A mathematical theory of the S andSR-matrices is developed.

Opportunistic Foraging by Largemouth Bass (Micropterus salmoides)

During 1980, adult largemouth bass diets in Peter and Paul lakes (Michigan's Upper Peninsula), included prey ranging in size from zooplankton (e.g., Daphnia) to vertebrates (fishes, amphibians, reptiles and small mammals). A partial winterkill in 1980-1981 reduced bass populations in both lakes by as much as 50%. Given the observed reduction in adult bass density and presumed reduction in intraspecific competition for food in 1981, we anticipated dietary changes as a consequence of more food being available to each surviving bass. Two approaches to foraging theory were compared in this study. Functional response models predict that density-dependent effects should be seen simply as increased numbers of each prey type eaten and that all prey will remain in the diet. By contrast, optimal foraging theory predicts that an increase in overall prey density will result in lower ranked prey items being dropped from the diet in an inverse order of ranking; the forager should become more specialized as net energy gain increases. Our data demonstrate opportunism in bass foraging behavior but provide support for the general tenets of optimal foraging theory. Large prey in the size range of the cost-curve nadir of adult bass were more abundant in the 1981 stomach samples. Lowest-ranked prey (e.g., Daphnia) became less important in 1981. Overall diet breadth of bass decreased. Growth rates of adult bass were greater in 1981 than 1980. INTRODUCTION Two somewhat different approaches to the study of diet selection have emerged in recent decades. One is based on experimental analysis of the functional components of the predation process (Ivlev, 1961; Holling, 1966). This approach is represented in reviews by Nilsson (1978), O'Brien (1979) and Dill (1983). In general, mechanistic analyses of the predator's perceptive capabilities, behavioral responses, mechanical capabilities and motivational state are combined in what are generally termed functional response models to yield predictions of predation rates on each of the available prey types. A second class of models is derived from extensions of experimental, mechanistic studies that emphasize optimization by the predator. The basic ideas of MacArthur and Pianka (1966) and Emlen (1966) have been expanded to include a theory of diet breadth or diversity (Schoener, 1971). Various published symposia and monographs include reviews of this perspective (Kamil and Sargent, 1981; Pyke, 1984) and its application to fishes (Stroud and Clepper, 1979). Laboratory and field studies have demonstrated the applicability of the optimality approach to foraging by fishes (Werner and Hall, 1974; Vince et al., 1976; Werner, 1979; Mittlebach, 1981; Stoner, 1982). Other models based simply on measures of reactive distance and the probability of successful capture (i.e., functional response models) offer equally tenable correspondence between expected and observed results (reviewed by Dunbrack and Dill, 1983). More recently, evaluation of the constraints imposed on foraging behavior has been developed to assess the roles of predator avoidance (Werner and Gilliam, 1984) and the biomechanical components of prey perception (Li et al., 1985). Although both optimality and functional components will probably

Escape Behaviour and Use of Cover by Young-of-the-Year Brook Trout, Salvelinus fontinalis

The distance between young-of-the-year (YOY) brook trout (Salvelinus fontinalis) and an approaching observer when the trout first fled (reactive distance) was significantly shorter in areas of high cover than in areas of low cover. Reactive distance was negatively correlated with foraging rate in one stream but not in another. These results provide some support for a recent economic model of escape behaviour. Three measures of willingness to take risks while foraging, reactive distance, latency to forage after a disturbance, and use of foraging sites with overhead cover, increased with increasing body size of YOY brook trout. We suggest that stream-resident salmonids become more wary with increasing size because the relative benefits of growing quickly, and hence taking risks while foraging, decrease with increasing body size.

Size-Selective Predation on Zooplankton by the Smooth Newt, Triturus vulgaris

Smooth newt foraging on Daphnia was studied to uncover mechanisms affecting sizeselective predation. Factors examined were size difference between small and large prey, visibility of prey, hunger, foraging experience, encounter rate with the most rewarding prey, and available light. Reactive distances and handling times increased with Daphnia size. The newts' ability to distinguish between small and large prey improved with the size difference of the two prey classes. A clear preference for larger prey was observed. The newts were less successful in capturing large prey than small prey. Brown-pigmented Daphnia were selected significantly more often than pale Daphnia. Well-fed newts were more selective than starved newts.

Random Search by Herbivorous Insects: A Simulation Model

A stochastic simulation model that relates the success of various herbivore searching behaviors to the density and arrangement of food plants was developed. It was designed to be field—testable with all model parameters directly measurable in field experiments. The model uses probability distributions and parameter ranges that are in accordance with published herbivore movement data. In the model, herbivore insect searching success depends in a complex manner upon parameters such as insect move lengths, turning angle concentration, reactive distance, risk of mortality while searching, plant density, plant dispersion, and plant stand size. Simulation results preclude simple generalizations and indicate that the outcome of interactions between plant density, plant dispersion, and herbivore searching behavior depends heavily upon parameter values. I argue that species—to—species shifts in the details of the simple searching process that I simulate could explain the (experimentally observed) high variation in herbivore response to vegetation texture. I discuss plant and insect strategies that are optimal" within biological constraints. For example, results from the model suggest that under many conditions clumping by plants can be an effective escape strategy from searching herbivores. This contradicts the claim that plant spatial distribution does not affect insect searching success, a claim that is justified only if it is assumed that organisms search (infinitely long) without biological cost. The importance of considering the cost of ineffective search is emphasized.

Search dynamics in fruit-parasitic insects

This paper examines methodology for evaluating and employing forager perceptive abilities into descriptive models for insects that visually search for resources. Using host seeking, female tephritid fruit flies as model parasitic insects a reactive distance envelope model, based upon earlier work of Holling (1966), is developed and tested in the laboratory and field. The laboratory derived values accurately predict the frequency at which flies detect fruit clusters in nature. Further, the envelope is shown to be assymetric wherein flies searching below fruit clusters discover those clusers more readily than similar sized clusters located below searching flies. The concept of the reactive envelope is integrated with forager search paths and host distribution into simple simulation models that test the hypothesis that host encounter rate and patch residence time may be greatly influenced by variation in any of the three aforementioned search parameters. It is concluded that models that include details of: (1) host density and distribution, (2) forager movement patterns, (3) forager perceptual constraints and, (4) forager information processing and memory, provide appropriate tools for evaluating foraging behaviour of animals in nature.

Mechanismes intervenant dans l'estimation des distances predateur-proie chez Ranatra

Data from previous experiments on predator-prey distance estimation during ontogeny are compared to theoretical interpretations. In Ranatra the relationships between performance (maximum reactive distances), effectors (length of forelegs) and receptors (eyes) do not remain constant during nymphal development, contrary to Mantids (Maldonado et al., 1973). The hypothesis of an automatic morphological adaptation occurring after each moult cannot be retained. Burkhardt et al.'s (1973) theoretical analysis of binocular vision in insects was applied to Ranatra : for the first four nymphal instars, the calculated limits of binocular vision coincide with maximum reactive distances. This could explain why these animals do not react to prey items presented at distances equal to the length of their forelegs before the 5th instar. The theoretical limits of binocular vision are further away than the maximum capture distances and the length of their forelegs for 5th instar nymphs and adults ; the length of their forelegs would then limit capture possibilities.

The effect of parthenogenic eggs in Daphnia magna on prey location by the bluegill sunfish (Lepomis macrochirus)

The distance at which the bluegill sunfish (Lepomis macrochirus) can locate Daphnia magna with parthenogenic eggs is shown to be significantly greater than the reactive distance for non-gravid Daphnia of the same size. This difference is due to greater visibility of the gravid prey and not to different locomotor behavior, since there was no correlation between the number of eggs carried by a Daphnia and the antennal beat frequency. Based on this experiment and other observations, an explanation is given for selective predation of polymorphic cladoceran populations.