Using behavior and ecology to exploit schooling fishes

By the late 1980's, humans were removing 76 million metric tons (MMT) of marine fishes annually. The potential sustainable catch is somewhere between 69 and 96 MMT. As a result, major fisheries have collapsed or are in danger of collapsing. Many of these species school. Schooling is effective against gape-limited predators because of dilution and confusion. However, larger predators may exploit schooling behavior to sequester and consume a non-trivial fraction of the group. This is the strategy of fishers. Both gear and fisher behavior have evolved to take advantage of the seemingly canalized response of schooling species. This paper examines the ways artisanal and western fishers have exploited knowledge of the behavior and ecology of schooling species to aid in fish capture. Topics include object association; use of light, sound, and chemicals; perceived barriers; predator-prey and other trophic interactions; inherent cyclical rhythms such as diel migration, lunar spawning, and seasonality; and correlations with the physical environment. Exploiting schooling allows fishers to increase efficiency through knowledge of when and where fish aggregate, or by extending the conditions under which aggregation occurs. However, knowledge of behavioral ecology can also be used to conserve schooling stocks. Gear selectivity, group size and population dynamics, and fisher efficiency are all potential areas of integration between behavioral ecology and fishery management. However, no amount of integration of behavioral ecology into fishery management will have the intended conservation effects if fishing effort is not limited to at least numerical if not behaviorally-sustainable levels.     

Early environment influences later performance in fishes

Conditions fish encounter during embryogenesis and early life history can leave lasting effects not only on morphology, but also on growth rate, life‐history and behavioural traits. The ecology of offspring can be affected by conditions experienced by their parents and mother in particular. This review summarizes such early impacts and their ecological influences for a variety of teleost species, but with special reference to salmonids. Growth and adult body size, sex ratio, egg size, lifespan and tendency to migrate can all be affected by early influences. Mechanisms behind such phenotypically plastic impacts are not well known, but epigenetic change appears to be one central mechanism. The thermal regime during development and incubation is particularly important, but also early food consumption and intraspecific density can all be responsible for later life‐history variation. For behavioural traits, early experiences with effects on brain, sensory development and cognition appear essential. This may also influence boldness and other social behaviours such as mate choice. At the end of the review, several issues and questions for future studies are given.     

Bioeconomics of schooling fishes: selfish fish, quasi-free riders, and other fishy tales

Applying the economic theory of clubs to the biological literature on schooling fish, this paper develops a 'selfish fish' club-theoretic paradigm of why fish join a fish school, and arrive at the following conclusions. A selfish fish: (a) joins the fish school because it derives hydrodynamic benefits (a club good); the selfish fish is a 'quasi-free rider'; (b) has no incentive to completely free ride on the benefits of the club good, because it will be, literally, left behind by the school; the fish school is a self-enforcing exclusive club; (c) has no incentive to shirk leadership role in the school because of the role reversibility of leaders and followers; (d) derives benefits from defense, another club good, via the many anti-predator defensive devices provided by club members; (e) has no incentive to discriminate against odd-looking outsiders, since odd-looking fish in a fish school are attacked by predators more frequently than look alikes. But outsiders display xenophobia toward insiders because outsiders do not wish to become prime targets for predators; the result is the formation of homotypic fish schools. Finally, (f) since escape is the main anti-predator defense manoeuvre, the 'any-one leader' rule for making collective choice of escape is the optimal decision-making rule for members of a fish school; this explains the leaderless, completely decentralized form of organization of fish schools. This paper thus contribute to new and deeper insights into various aspects of the bioeconomics of schooling fish.     

Suction feeding mechanics, performance, and diversity in fishes

Despite almost 50 years of research on the functional morphologyand biomechanics of suction feeding, no consensus has emergedon how to characterize suction-feeding performance, or its morphologicalbasis. We argue that this lack of unity in the literature isdue to an unusually indirect and complex linkage between themuscle contractions that power suction feeding, the skeletalmovements that underlie buccal expansion, the sharp drop inbuccal suction pressure that occurs during expansion, the flowof water that enters the mouth to eliminate the pressure gradient,and the forces that are ultimately exerted on the prey by thisflow. This complexity has led various researchers to focus individuallyon suction pressure, flow velocity, or the distance the preymoves as metrics of suction-feeding performance. We attemptto integrate a mechanistic view of the ability of fish to performthese components of suction feeding. We first discuss a modelthat successfully relates aspects of cranial morphology to thecapacity to generate suction pressure in the buccal cavity.This model is a particularly valuable tool for studying theevolution of the feeding mechanism. Second, we illustrate themultidimensional nature of suction-feeding performance in acomparison of bluegill, Lepomis macrochirus, and largemouthbass, Micropterus salmoides, two species that represent oppositeends of the spectrum of performance in suction feeding. As anticipated,bluegills had greater accuracy, lower peak flux into the mouth,and higher flow velocity and acceleration of flow than did bass.While the differences between species in accuracy of strikeand peak water flux were substantial, peak suction velocityand acceleration were only about 50% higher in bluegill, a relativelymodest difference. However, a hydrodynamic model of the forcesthat suction feeders exert on their prey shows that this differencein velocity is amplified by a positive effect of the smallermouth aperture of bluegill on force exerted on the prey. Ourmodel indicates that the pressure gradient in front of a fishthat is feeding by suction, associated with the gradient inwater velocity, results in a force on the prey that is largerthan drag or acceleration reaction. A smaller mouth apertureresults in a steeper pressure gradient that exerts a greaterforce on the prey, even when other features of the suction floware held constant. Our work shows that some aspects of suction-feedingperformance can be determined from morphology, but that thecomplexity of the behavior requires a diversity of perspectivesto be used in order to adequately characterize performance.     

Appetitive conditioning technique reveals behavioural limits to passage performance in fishes

Numerous environmental features have the potential to act as barriers to fishes in the field. Passage of these barriers depends on two main properties: willingness (behavioural) and physiological capacity. The physiological swimming capacity of fishes has been well studied. However, because most barrier research has focused on the population level effects of man – made barriers, little attention has been given to the behavioural aspects of fish passage. We used appetitive conditioning to create a simple laboratory based protocol to estimate behavioural limits to fish passage. We tested our protocol using barrier height (or passage space) as a model. Our protocol successfully identified behavioural limits in two species, juvenile rainbow trout, Oncorhynchus mykiss, and fathead minnows, Pimephales promelas. Our most interesting observation was that even a partial, submerged barrier had the potential to block fish movements. Our results suggest a potential use for conditioning techniques in assessing factors that constitute behaviour barriers to fishes. This information may help us to better predict fish movements in the field and may help us to design barriers that are more efficient at passing fishes.     

Features heightening cardiovascular performance in fishes,with special reference to tunas

Information on heart rate, cardiac mass, vascular resistance, and myocardial oxygen consumption are considered with a view to identifying special features that heighten cardiovascular performance in fish, and especially in tuna. Fish rarely have heart rates greater than 120 bpm. Skipjack tuna are an exception, with heart rates approaching those of similarly sized mammals. A large relative ventricular mass is a characteristic of, but not exclusive to, active fish. However, the pyramidal shape of this large ventricle in active fish is a distinguishing characteristic. This anatomical form may be important in the coupling of high cardiac stroke volumes (around 1 mL/kg) with high heart rates and blood pressures. Skipjack tuna excel in this regard. The characteristically high cardiac power output and large ventricular mass in active fish necessitates a coronary circulation. In most active fish, however, the coronary circulation is important under extreme conditions (e.g., swimming and hypoxia) rather than for routine performance. Skipjack tuna may be an exception, requiring their coronary circulation for routine performance. Neither total vascular resistance nor the relative O₂ cost of cardiac pumping stand out as being unusual in active fish. Even so, the unusually high resistance of the branchial circulation in skipjack tuna may represent an upper design limit for the structure of individual lamellae.     

Linking functional morphology and feeding performance in larvae of two coral-reef fishes

Despite the well acknowledged phenomenon that the biology of marine teleost fish larvae is much different from that of juvenile and adult conspecifics, very little is known about the changes in design of the feeding apparatus as larvae develop from hatching through metamorphosis. Furthermore, our understanding of the consequences of these developmental changes for feeding performance is very limited. In this study, we examined the relationship between the development of the feeding apparatus and feeding performance in larvae of Amphiprion ocellaris and Pseudochromis fridmani using cluster analysis, multi-dimensional scaling (nMDS), and canonical correspondence analysis (CCA). Several patterns emerge from our analyses. First, the state of development of the feeding apparatus increased in complexity through ontogeny, from a simple, hyoid-driven system at the onset of exogenous feeding to a more complex feeding system involving all adult functional elements of the cranium just prior to metamorphosis. Although the feeding apparatus converged to the hyoid-opercular-mandible linkage state around metamorphosis in both species, P. fridmani had a lesser developed hyoid-mandible linkage system relative to A. ocellaris at the onset of first-feeding. Second, first-feeding larvae fed on smaller, less elusive zooplankton. In contrast, larvae that survived beyond the first-feeding stage fed on more diverse prey types, including larger, more elusive zooplankton. Third, intra- and inter-specific variation in the development of the feeding apparatus is associated with variation in feeding performance. The post-hatch developmental trajectory in both species showed a pattern consistent with stage (i.e., ontogenetic state)-specific shifts in morphology and performance. Furthermore, the number of developmental transitions in both feeding functional morphology and feeding performance differ between species that exhibit contrasting incubation periods.     

Formation of lateralized motor skills in rats

Adult Wistar rats were trained to get food with a forepaw from a narrow tube under conditions of free choice of a limb. It was shown that the presence or absence of limb preference determined by preliminary short-run testing far from always defines the character and extent of lateralization formed in the process of training. It was also found that reaching the maximal extent of lateralization requires, on average, more extended period of training for the animals, which finally constituted the group of right-handers, than for the rats finally classified as left-handers.     

Effects of life phase and schooling patterns on the foraging behaviour of coral‐reef fishes from the genus Haemulon

During this study (December 2009 to December 2010), underwater visual surveys using the focal animal method were performed in the coastal reefs of Tamandaré, north‐eastern Brazil. The aim was to analyse the effects of the life phase (juvenile and adult) and schooling patterns (school and solitary) on the feeding behaviour (foraging rates and substratum preferences) of four species of the genus Haemulon (Haemulon aurolineatum, Haemulon parra, Haemulon plumieri and Haemulon squamipinna). PERMANOVA analysis (P < 0·05) indicated that ontogenetic changes and schooling patterns directly influence foraging behaviour. Schooling individuals had low foraging rates (mean ± s.d . = 2·3 ± 2·1 bites 10 min^?1) and mobility, usually remaining near the bottom; however, solitary fishes had high foraging rates (mean ± s.d . = 12·5 ± 4·6 bites 10 min^?1). Juveniles preferred feeding in the water column (75% of the total number of bites), whereas adults foraged mainly in sand (80%) and bare rock (20%). All four Haemulon species displayed similar patterns of feeding behaviour as well as preferences for foraging sites and display competition for food resources. In contrast, little is known about their habitat use and foraging behaviour over the diel cycle, particularly the newly settled and early juvenile stages.     

Swimming performance and metabolic rate of three tropical fishes in relation to temperature

Oxygen consumption was measured for three tropical fishes,Exodon paradoxus, Leporinus fasciatus andLabeo erythrurus in relation to swimming speed and temperature. For each species the logarithm of oxygen consumption (mg 0₂ · g^–1 · h^–1) increased linearly with relative swimming speed (1 · s^–1) with the value of the regression coefficients varying inversely with temperature. Active metabolism and critical swimming speed ofE. paradoxus andL. fasciatus increased with temperature to a maximum at 30 and 35° C respectively. Basal metabolic rates ofE. paradoxus andL. fasciatus increased with temperature. Metabolic rates and critical swimming speed of the three fishes studied were consistent with values for polar, temperate and other tropical species over their respective thermal ranges of tolerance. Tropical fishes have lowered their metabolism and swimming performance from that expected for many temperate species at the same temperature.     

Cultural diversity and schooling

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Comparing the performance of multiple mitochondrial genes in the analysis of Australian freshwater fishes

In this study, four mitochondrial genes (cytochrome oxidase I, ATPase, cytochrome b and control region) were amplified from most of the fish species found in the fresh waters of south-eastern Queensland, Australia. The performance of these different gene regions was compared in terms of their ability to cluster fish families together in a neighbour-joining tree, both individually by gene and in all combinations. The relative divergence rates of each of these genes were also calculated. The three coding genes (cytochrome oxidase I, ATPase and cytochrome b) recovered similar number of families and had broadly similar divergence rates. ATPase diverged a little more quickly than cytochrome oxidase I and cytochrome b slightly more slowly than cytochrome oxidase I. All two-gene combinations recovered the same number of families. Results from the control region were much more variable, and, although generally possessing more diversity than the other regions, were sometimes less variable.     

Swimming speed performance in coral reef fishes: field validations reveal distinct functional groups

Central to our understanding of locomotion in fishes are the performance implications of using different modes of swimming. Employing a unique combination of laboratory performance trials and field observations of swimming speed, this study investigated the comparative performance of pectoral and body-caudal fin swimming within an entire assemblage of coral reef fishes (117 species 10 families). Field observations of swimming behaviour identified three primary modes: labriform (pectoral 70 spp.), subcarangiform (body-caudal 29 spp.) and chaetodontiform (augmented body-caudal 18 spp.). While representative taxa from all three modes were capable of speeds exceeding 50 cm s⁻¹ during laboratory trials, only pectoral-swimmers maintained such high speeds under field conditions. Direct comparisons revealed that pectoral-swimming species maintained field speeds at a remarkable 70% of their maximum (lab-tested) recorded speed; species using body-caudal fin propulsion maintained field speeds at around 50% of maximum. These findings highlight a profound influence of swimming mode on performance, with the relative mechanical and energetic efficiency of each swimming mode being of major importance. Combining attributes of efficiency, maneuverability and speed in one mode of propulsion, pectoral swimming appears to be a particularly versatile form of locomotion, well suited to a demersal lifestyle on coral reefs.     

The role of adrenaline as a modulator of cardiac performance in two Antarctic fishes

The present work was performed to test the hypothesis that Antarctic teleosts rely mostly on cholinergic inhibition for autonomic modulation of the heart. The effects of adrenaline on the inotropic properties on paced, isometrically contracting muscle strips were examined in two distinct Antarctic teleosts, the haemoglobinless icefish Chaenocephalus aceratus and the red-blooded Notothenia coriiceps. All tissues examined revealed a negative force-frequency relationship. Under baseline conditions C. aceratus contracted with a force twice as great as that of N. coriiceps. While the degree to which ventricular tissues responded to adrenaline varied between species, adrenergic stimulation significantly increases myocyte contraction force in this group of fishes. Contraction and relaxation times were not significantly affected by adrenaline concentration while absolute rates of contraction were. Adrenergic stimulation does not enable tissues to achieve higher contraction frequencies, but is shown to be a potent modulator of contraction force.     

Bite performance in clariid fishes with hypertrophied jaw adductors as deduced by bite modeling

Within clariid fishes several cranial morphologies can be discerned. Especially within anguilliform representatives an increase in the degree of hypertrophy of the jaw adductors occurs. The hypertrophy of the jaw adductors and skeletal modifications in the cranial elements have been linked to increased bite force. The functional significance of this supposed increase in bite force remains obscure. In this study, biomechanical modeling of the cranial apparatus in four clariid representatives showing a gradual increase in the hypertrophy of the jaw adductors (Clarias gariepinus, Clariallabes melas, Channallabes apus, and Gymnallabes typus) is used to investigate whether bite force actually increased. Static bite modeling shows that the apparent hypertrophy results in an increase in bite force. For a given head size, the largest bite forces are predicted for C. apus, the lowest ones for C. gariepinus, and intermediate values are calculated for the other species. In addition, also in absolute measures differences in bite force remain, with C. apus biting distinctly harder than C. gariepinus despite its smaller head size. This indicates that the hypertrophy of the jaw adductors is more than just a correlated response to the decrease in absolute head size. Further studies investigating the ecological relevance of this performance difference are needed.     

Interference affects food-finding rate in schooling sticklebacks

Experiments on sticklebacks seeking for food patches show that foraging in schools enhances food-finding rate of individuals. A stochastic information-sharing model characterizes food-seeking behaviour in which food-finding by one in a school of fish results in food-sharing by many. The model predicts the food-finding rate of a randomly selected individual in a school of n fish to be that of a solitary forager weighted by the inverse of the school size, 1/n. In sticklebacks this seems not to be the case, however. Though the food-finding rate of individuals in the school reduces with n , the improvement is much slower than predicted by the basic model. We argue that a variant of the information-sharing model accounting for interference among individuals affecting their food-seeking behaviour fits the data better.     

Enhanced symbiotic performance by Rhizobium tropici glycogen synthase mutants

We isolated a Tn5-induced Rhizobium tropici mutant that has enhanced capacity to oxidize N,N-dimethyl-p-phenylendiamine (DMPD) and therefore has enhanced respiration via cytochrome oxidase. The mutant had increased levels of the cytochromes c(1) and CycM and a small increase in the amount of cytochrome aa(3). In plant tests, the mutant increased the dry weight of Phaseolus vulgaris plants by 20 to 38% compared with the control strain, thus showing significantly enhanced symbiotic performance. The predicted product of the mutated gene is homologous to glycogen synthases from several bacteria, and the mutant lacked glycogen. The DNA sequence of the adjacent gene region revealed six genes predicted to encode products homologous to the following gene products from Escherichia coli: glycogen phosphorylase (glgP), glycogen branching enzyme (glgB), ADP glucose pyrophosphorylase (glgC), glycogen synthase (glgA), phosphoglucomutase (pgm), and glycogen debranching enzyme (glgX). All six genes are transcribed in the same direction, and analysis with lacZ gene fusions suggests that the first five genes are organized in one operon, although pgm appears to have an additional promoter; glgX is transcribed independently. Surprisingly, the glgA mutant had decreased levels of high-molecular-weight exopolysaccharide after growth on glucose, but levels were normal after growth on galactose. A deletion mutant was constructed in order to generate a nonpolar mutation in glgA. This mutant had a phenotype similar to that of the Tn5 mutant, indicating that the enhanced respiration and symbiotic nitrogen fixation and decreased exopolysaccharide were due to mutation of glgA and not to a polar effect on a downstream gene.