bluuebunny/crossref_metadata_2025 huggingface dataset:
Contrasting effects of the extent of sea‐ice on the breeding performance of an Antarctic top predator, the Snow Petrel Pagodroma nivea
Authors: Barbraud Christophe , Weimerskirch Henri
Published: December 2003

Recent studies have shown that the Antarctic Circumpolar Wave and the related sea‐ice cover around the Antarctic continent may have a profound effect on the lower trophic levels of the marine environment. In particular, extensive sea‐ice cover enhances the survival of krill. However, the effects of sea‐ice cover on top predators remain poorly understood. Using time series from 1973 to 1999, we examine the influence of regional sea‐ice extent on a number of indices of breeding performance of an avian predator, the Snow Petrel, in Antarctica. The percentage of breeding pairs was highly variable and there were fewer birds breeding when sea‐ice cover was extensive during July. By contrast, overall breeding success and fledgling body condition were improved during years with extensive sea‐ice cover during the preceding November and July–September. These results indicate that the same sea‐ice conditions may have different effects on the breeding performance of a species. The overall increase in winter sea‐ice extent during the last decade appears to have resulted in an overall improvement of the quality of fledglings produced, and thus probably of future recruitment.
The function of female and male ornaments in the Inca Tern: evidence for links between ornament expression and both adult condition and reproductive performance
Authors: Velando A. , Lessells C. M. , Márquez J. C.
Published: December 2003

Inca Terns Larosterna inca are medium‐size seabirds that breed along the Peruvian and Chilean coast. They are monogamous and both sexes incubate and contribute to chick provisioning. The sexes are similar in appearance and have elaborate ornaments, including a long white moustache of feathers and fleshy yellow wattles. In this paper we report the differences in ornamentation between sexes and examine whether the trait predicts body condition, reproductive performance or chick quality in either sex. The ornaments were similar in size and coloration between the sexes, except for the wattle length, the difference in which can be due to greater head length in males. Moustache length was the most reliable signal of body condition in both sexes. Moreover, there was a significant relationship between the moustache length and reproductive category of adults (non‐breeder, unsuccessful breeder, or one or two chicks fledged). Both asymptotic chick body mass and the T‐cell mediated response of chicks (a measure of immunocompetence) were related to the moustache length of male and female adults. These results provide support for the role of ornaments in mutual signalling of condition in this species. Female and male ornaments predict body condition, reproductive performance and chick quality, as predicted by sexual selection models.
Extra‐pair paternity among Great Tits Parus major following manipulation of male signals
Authors: Otter Ken A. , Stewart Ian R. K. , McGregor Peter K. , Terry Andrew M. R. , Dabelsteen Torben , Burke Terry
Published: December 2003

Female Great Tits are known to eavesdrop on the singing behaviour of males. It is unknown, however, whether manipulation of these signals is sufficient to influence extra‐pair copulations, or whether such potentially costly reproductive decisions are unaffected by altering short‐term signals of condition. Using interactive playbacks, we systematically engaged males in territorial contests in which we could control whether the focal male won or lost the interaction, regardless of the males’ true potential. We then determined the levels and patterns of extra‐pair paternity among experimental and neighbouring pairs using DNA microsatellite analysis. Extra‐pair young were found in equal frequency among the nests of males allowed to win interactions as among those who lost interactions. However, cuckolded males were significantly less variable in allele sizes across the five microsatellite alleles tested than males who were not cuckolded. As measures of genetic variability are increasingly being found to correlate with individual fitness, this may suggest that females are attentive to underlying measures of condition when making extra‐pair decisions. Short‐term modification of the males’ perceived quality may be insufficient to cause females to alter extra‐pair decisions.
Switching to a feeding method that obstructs vision increases head‐up vigilance in dabbling ducks
Authors: Guillemain Matthieu , Duncan Patrick , Fritz Herve
Published: December 2003

A major assumption in most models of foraging is that feeding and vigilance are mutually exclusive. A recent experimental study challenged this hypothesis and demonstrated that birds are able to detect predators while pecking seeds on the ground (head‐down vigilance). Experimental obstruction of head‐down vigilance makes birds increase head‐up vigilance (i.e. the classical overt vigilance posture). For many foragers in the wild, visibility varies between habitats and foraging methods. We compared the vigilance of Teal Anas crecca and Shoveler Anas clypeata when foraging with their eyes above the water surface (shallow feeding, only the bill submerged) and when foraging with their eyes underwater (deep feeding, head and neck underwater, or upending), at three wintering sites in western France. Birds of both species spent less time in head‐up vigilance during shallow foraging than during deep foraging, with no significant difference between sites, which suggests that they are capable of some vigilance during shallow foraging. During deep foraging, the time spent vigilant increased because the frequency of scans was much higher, while scan length decreased. However, these differences could have resulted from variations in the availability of food at different depths. In an experiment where the food availability was constant, we observed the same pattern, with a higher frequency of scans during deep foraging. This study therefore provides strong support for the idea that vigilance and foraging are not always mutually exclusive and shows that switching between searching methods can cause vigilance time – and, as a consequence, loss of feeding time – to vary. This should be taken into account in future field and experimental studies of the trade‐off animals make between vigilance and feeding.
Sex‐dependent frequency and consequences of natural handicaps in American Kestrels
Authors: Dawson Russell D. , Bortolotti Gary R. , Murza Gillian L.
Published: December 2003

Natural selection theory suggests that there should be fitness consequences for animals that possess morphological abnormalities such as missing or deformed appendages and other structures. As these characters are expected to be detrimental, morphological abnormalities could be considered “handicaps”. However, little information exists about the nature, prevalence or consequences of naturally occurring handicaps in birds, even though experimental handicapping has been used in some behavioural studies. Here, we document and describe the frequency of natural handicaps in American Kestrels Falco sparverius, and investigate their influence on condition and survival. We considered three different categories of handicap that should negatively impact falcons: missing remiges and rectrices, broken remiges and rectrices, and foot handicaps. Broken feathers, followed by missing feathers, were the most common handicaps detected in kestrels and their prevalence increased throughout the breeding season. Foot handicaps were relatively rare and showed no seasonal trends. There was no effect of any handicap type on body condition or return rates of male kestrels. In contrast, females with either foot handicaps or broken feathers were in significantly poorer condition than control females, and females with broken feathers were less likely than control females to return to the study area in years following initial capture. Given that female kestrels with broken feathers have more fault bars than those without broken feathers, and fault bar formation is related to stresses in a bird's past, we suggest that female kestrels that had broken feathers were of poorer quality than those without broken feathers or those with missing feathers. Females with broken feathers may therefore have been in poorer condition initially than other birds, or if broken feathers are indicative of poor quality, then females with broken feathers may have been less able to cope with the negative impacts of feather loss on flight performance compared to birds with missing feathers.
Foraging trip duration increases for Humboldt Penguins tagged with recording devices
Authors: Taylor Sabrina S. , Leonard Marty L. , Boness Daryl J. , Majluf Patricia
Published: December 2003

Marine animals equipped with data recording devices sometimes show changes in their foraging behaviour, which can indicate an adverse effect of the instrument. We attached time‐depth recorders (TDRs) and radio‐transmitters to study foraging behaviour in Humboldt Penguins Spheniscus humboldti and observed an increase in the duration of foraging trips. We suggest that further tagging of this endangered species be approached with caution since this increase in trip duration may negatively affect reproductive and foraging success.
On cognitive conservation biology: why chickadees leave a patch of woodland
Authors: Grubb, Jr. Thomas C. , Bronson C. L.
Published: December 2003

Although not previously emphasized, colonization of habitat patches by cognitive animals involves both decisions bringing an animal to a particular patch and decisions causing the animal to remain in the patch. We focus on the latter form of decision by examining the habitat and landscape correlates of persistence in chickadees (Poecile spp.) that we introduced into small woodlots previously cleared of conspecifics. The birds’ decisions to remain were associated importantly with the presence of a canopy layer of large trees, and less so with area of the woodland patch and distance they had been transported from the capture site. The decision to persist was little related to landscape features near the focal habitat patch. The future holds promise for application of principles of cognition to landscape biology.
Effects of body size on sympatric shelter use in over‐wintering juvenile salmonids
Authors: Orpwood J. E. , Griffiths S. W. , Armstrong J. D.
Published: December 2003

The study tests two hypotheses: (1) the degree of shelter dominance in Atlantic salmon Salmo salar and brown trout Salmo trutta increases progressively with increasing size differential between heterospecific fish in a pair and (2) shelter dominance, standardized to size differential, correlates with aggression. The results support the first but not the second hypothesis, suggesting that the fitness consequences of high growth performance during the summer are likely to become evident during winter. At this time of year, when mortality is high among both Atlantic salmon and brown trout, shelter dominance may increase the chances of survival.
Tractable models for testing theories about natural strategies: foraging behaviour and habitat selection of free‐ranging sharks
Authors: Sims D. W.
Published: December 2003

Marine and terrestrial environments differ fundamentally in space‐time scales of both physical and ecological processes. These differences will have an impact on the animals inhabiting each domain, particularly with respect to their spatial ecology. The behavioural strategies that underpin observed distributions of marine species are therefore important to consider. Comparatively little is known, however, about how wild fishes actually respond to gradients in food supply and temperature, and to potential mates. This paper describes how behavioural theory is being used to elucidate the strategies and tactics of free‐ranging sharks in three specific areas of study, namely, foraging on zooplankton, behavioural energetics and sexual segregation. The studies discussed are novel because shark movements were tracked in the wild using electronic tags in relation to simultaneous measurements of prey densities and thermal resources. The results show that filter‐feeding (basking shark,Cetorhinus maximus) and predatory (dogfish,Scyliorhinus canicula) sharks have relatively complex behaviour patterns integrally linked to maximizing surplus power, often through making short and longer term ‘trade‐off’ decisions between optimal foraging and thermal habitats. Interestingly, femaleS. caniculaexhibit alternative behavioural strategies compared to males, a difference resulting in spatial segregation by habitat. Sexual segregation in this species occurs primarily as a consequence of male avoidance by females. Studies on free‐ranging sharks provide a useful model system for examining how a predator's strategy is shaped by its environment. More theory‐based studies of the behavioural processes of sharks are required however, before critical comparisons with other vertebrate predators are possible. Suggestions for further research to address this knowledge gap are given.
The bitterling–mussel interaction as a test case for co‐evolution
Authors: Mills S. C. , Reynolds J. D.
Published: December 2003

The European bitterlingRhodeus sericeus(Cyprinidae) spawns in the gills of freshwater mussels (Unionidae) and shows some obvious adaptations to this type of spawning, such as the development of an ovipositor. Furthermore, recent studies have shown that the fish avoid species of mussels that have a high likelihood of ejecting their eggs prematurely. This leads to the question of whether the interaction between bitterling and mussels could represent a case of co‐evolution, involving evolutionary responses by both species to selection imposed by the other. The evidence for and against co‐evolution is reviewed, incorporating new results from two sets of experiments designed to test for adaptive choices by bitterling according to the mussels’ sex and reproductive state, as well as a preliminary study of potential benefits for mussels from exposure to bitterling. Host preferences by bitterling, both among and within mussel species, may indeed have evolved in response to differences in benefits for offspring survival. There is no evidence yet for any benefits to mussels from receiving eggs, whereas there are costs due to reduced ventilation rates when the gills contain bitterling eggs. While there are differences among mussel species and individuals in their tendency to reject bitterling embryos, these differences do not provide strong evidence for co‐evolution. For example, they may reflect differences in host physiology such as ventilation rate and generalized responses to expelling objects from their gills. Therefore, while bitterling are well adapted for their obligate spawning relationship with mussels, it has been much more difficult to find evidence for adaptations by mussels for dealing with bitterling. This suggests that any co‐evolutionary dynamics between bitterling and mussels may be asymmetric, with stronger responses to selection by the fish than by mussels.
Reproductive success in male sunbleak, a recent invasive fish species in the U.K.
Authors: Gozlan R. E. , Flower C. J. , Pinder A. C.
Published: December 2003

The spawning behaviour of male nest guarding sunbleak Leucaspius delineatus, a recent invasive species in southern England, was studied and quantified for the first time. In the absence of physical differences between territorial and non‐territorial males (i.e. colour, size, etc.), the reproductive behaviour of territorial males was analysed and related to reproductive success. The results showed that females preferred high‐courting and highly aggressive males. The initial cue in female mate choice, however, was based on courtship, while aggression was the decisive behavioural trait in influencing mate choice, providing a direct signal of physical condition and ‘paternal competence’. Some males picked nest sites which were subsequently preferred by other males taking over the nest of a previous male (‘communal nest’), with the new territorial male adopting the eggs already present at the nest. It appears that either due to female preference for nests already containing eggs or lower rates of sired egg predation by dilution among unrelated eggs, sunbleak males have adopted the mating strategy of allopaternal care.
Growth, pigmentation and activity of juvenile Japanese eels in relation to temperature and fish size
Authors: Dou S. , Miller M. J. , Tsukamoto K.
Published: December 2003

The growth and activity of juvenile Japanese eels Anguilla japonica in different pigmentation stages from the glass eel to the elver stage were studied in the laboratory at 15, 20 and 25° C. The growth and activity of the eels were significantly influenced by both temperature and fish size. Growth rate generally declined with increasing fish size, and fish were least active and experienced a low growth during the pigmenting stage at all temperatures. They were nocturnal and spent significantly more time moving (swimming, feeding and moving over the substratum) at 20 and 25° C than at 15° C at night within each pigmentation stage. Accordingly, they grew significantly faster at 20 and 25° C than at 15° C throughout the study. The development of pigmentation appeared to be dependant on water temperature but not on fish size. This study suggested that the growth and activity of juvenile Japanese eels were positively correlated, because fish were least active and grew slowest at low temperature (15° C) or during the pigmenting stage at all temperatures.
The efficiency of adaptive search tactics for different prey distribution patterns: a simulation model based on the behaviour of juvenile plaice
Authors: Hill S. L. , Burrows M. T. , Hughes R. N.
Published: December 2003

Juvenile plaicePleuronectes platessaare particularly useful for studying forager search behaviour because their search paths are essentially two dimensional, and punctuated by natural stops. Their prey occur in a range of natural distributions from highly aggregated to over‐dispersed. Juvenile plaice use area‐restricted search near aggregated prey and extensive search, consisting of longer moves and fewer turns, between aggregations and when searching for dispersed prey. They search for less conspicuous prey items mainly in the pauses between movements. This saltatory search behaviour contrasts with the continuous search that is usually assumed in search models. A simulation model of saltatory search behaviour showed that a strategy combining extensive and intensive search allows the efficient exploitation of a range of natural prey distribution patterns, and that it is particularly effective when the search behaviour is controlled by perceived prey density. This allows the predator to respond to the localized aggregations which often occur in nature. The selective use of intensive search was more efficient than the continuous use of extensive search even in prey distribution patterns that were statistically over‐dispersed.
The dynamics of prey choice in fish: the importance of prey size and satiation
Authors: Gill A. B.
Published: December 2003

Over a number of decades the process of prey choice has been investigated using fishes as model predators. Using fishes for the model has allowed the proximate factors that determine how a mobile predator finds and chooses to eat the prey encountered within a variable 3‐D environment to be estimated. During prey choice a number of constraints exist, in particular most fish predators will eat their prey whole thus their jaws and gut create functional limitations once a prey has been attacked. By considering the relationship between the size of the prey and the predator's feeding apparatus and feeding motivation this study explores the link between mechanistic studies and theoretical, optimal foraging based predictions. How the prediction of prey choices made by the fish following prey encounter can be reconciled with what is likely to be found in the fish's stomach is discussed. This study uses a progression of empirical examples to illustrate how the limits of functional constraints and prey choice at different stages of motivation to feed can be taken into account to improve predictions of predator prey choice.
Use of water flow direction to provide spatial information in a small‐scale orientation task
Authors: Braithwaite V. A. , Girvan J. R.
Published: December 2003

Experiments were designed to investigate whether three‐spined sticklebacksGasterosteus aculeatuscan use direction of water flow as an orientation cue. The fish had to learn the location of a food patch in a channel where water flow direction was the only reliable indicator of the food patch position. Fish from two ponds and two rivers were trained and tested in the spatial task to determine whether river three‐spined sticklebacks are more adept at using water flow as a spatial cue than fish from ponds. All fish were able to use water flow to locate the food patch but one of the two river groups was significantly faster at learning the patch location. When the task was reversed so that fish that had formerly been trained to swim downstream now had to learn to swim upstream andvice versaboth river groups learned the reversed task faster than the two pond groups. In a second experiment, to investigate whether fish from ponds or rivers vary in the type of spatial cue that they prefer to use, fish from one pond and one river were given a choice between two different types of spatial cue: flow direction or visual landmarks. A test trial in which these two cues were put into conflict revealed that the river population showed a strong preference for flow direction whilst the pond population preferred to use visual landmarks.
Fishes as models in studies of sexual selection and parental care
Authors: Amundsen T.
Published: December 2003

Fishes are by far the most diverse group of vertebrates. This fact is in no way, however, reflected in their use as model organisms for understanding sexual selection or parental care. Why is this so? Is it because fishes are actually poor models? The usefulness of fishes as models for sexual selection and parental care is discussed by emphasizing some problems inherent in fish studies, along with a number of reasons why fishes are indeed excellently suited. The pros and cons of fishes as models are discussed mainly by comparison with birds, the most popular model organisms in animal behaviour. Difficulties include a lack of background knowledge for many species, and the problems of marking and observing fishes in their natural environment. Positive attributes include the diversity of lifestyles among fishes, and the ease with which they can be studied experimentally in the laboratory. How useful fish models can be is briefly illustrated by the impressive and broadly relevant advances derived from studies of guppies Poecilia reticulata and three‐spined sticklebacks Gasterosteus aculeatus. A selection of topics is highlighted where fish studies have either advanced or could greatly enhance, the understanding of processes fundamental to animal reproductive dynamics. Such topics include sex role dynamics, the evolution of female ornamentation and mate choice copying. Finally, a number of potential pitfalls in the future use of fish as models for sexual selection and parental care are discussed. Researchers interested in these issues are recommended to make much more extensive use of fish models, but also to adopt a wider range of models among fishes.
Linking models of animal behaviour and habitat management: Atlantic salmon parr and river discharge
Authors: Armstrong J. D. , Holm C. F. , Kemp P. S. , Gilvear D. J.
Published: December 2003

Understanding preferences of animals is of fundamental importance for modelling habitat quality and quantity. Important theoretical developments, for example using ideal free and ideal despotic distributions (IDD), have enabled biologists to build conceptual frameworks for relating habitat preferences of individual animals to distributions and dynamics of populations. At the same time, managers of natural resources have established predictive empirical models as a basis for understanding habitat quality. For example, the Physical Habitat Simulation model (PHABSIM) has been widely applied for managing river flows. The aim of this study was to conduct experiments, using Atlantic salmon parr, to test whether observed population distributions could be predicted using simple behaviour theory and PHABSIM. We show that predictions from PHABSIM depend crucially on population density, discharge and the interaction between density and discharge at the time when the model is parameterized. These findings can, in part, be explained by consideration and application of the IDD. However, the results of the experiments also suggest that models derived from first behavioural principles may need to be unexpectedly complex and species‐specific if they are to capture the population response to variations in water discharge effectively.
Fish cognition: what can we learn, and what do they need to learn?
Authors: Braithwaite V.
Published: December 2003

Fish provide a wonderful opportunity to explore processes that shape and select cognitive ability. In this presentation, I will illustrate three aspects of work that my colleagues and I have used to investigate fish learning and memory over the last decade. First, I will discuss how comparing different populations sampled from contrasting habitats allows differences in cognitive ability to be related to the evolutionary ecology of the fish. I will use examples that have investigated how differences in learning ability between populations of the same species can arise. Here, the examples will be taken from the ubiquitous three‐spined stickleback, and a Panamanian poecilid, Brachyraphis.

The second approach has used fish cognition as a tool to quantify behaviour to enable assessment of different aspects of fish welfare. For example, the recent work investigating pain perception in trout required the use of a learning task to quantify how fish behaviour was modified after noxious stimulation. Ways in which these, and similar, processes can be used in future studies of fish welfare will be discussed.

The final part of the presentation will consider recent work that addresses the problems of releasing hatchery‐reared fish for restocking purposes. Although a common practice, most of the hatchery‐reared fish die shortly after they are released. Much of the observed mortality apparently stems from the fishes’ inexperience with a variable environment. Experiments with juvenile cod and brown trout suggest that both age, and the early rearing environment, have profound effects on fish learning and behaviour. I will discuss how simple modifications to current rearing practices may have large beneficial effects on the post‐release survival of hatchery‐reared fish.
The role of social learning in conservation and fisheries reintroductions
Authors: Brown C. , Laland K.
Published: December 2003

The plight of the world fish stocks is all too well documented. As part of an ongoing attempt to bolster fish stocks for both commercial and conservation purposes, many fish are reared in captivity and released into the wild. It is well known that hatchery‐reared fish have low post‐release survival compared with wild fish of similar age. Part of the reason for this high mortality is that hatchery fish show deficits in virtually all aspects of their behaviour, including prey selection and predator avoidance. Much behaviour requires repeated experience so that it may become fine‐tuned to prevailing circumstances via learning during development. It has been suggested that inappropriate behaviour is encouraged when fish are reared in the unnatural surroundings of the hatchery. However, hatchery fish can be taught to recognise live, novel prey items and predators and the rate of learning is increased in the presence of a more knowledgeable conspecifics. Here we present data showing how social learning protocols can be used to dramatically increase foraging success in juvenile Atlantic salmon. We also outline related aspects of our ongoing research and discuss some of the possibilities for altering hatchery practices to maximize post‐release survival.
Bitterling as models for studies of sperm competition
Authors: Candolin U. , Reynolds J. D.
Published: December 2003

Game theory models of sperm competition predict that sperm expenditure should depend on the intensity of sperm competition. Specifically, there should be an increase in sperm expenditure when a male has one competitor, but a decrease with additional competitors. European bitterling, Rhodeus sericeus, are good models for testing this theory because sperm release by males is readily observable and territorial males regularly compete with variable numbers of sneakers. Females spawn in living freshwater mussels (Unionidae) and males release their sperm over the inhalent siphon both before and after egg laying. Our experiments confirmed that both territorial and sneaker males adjusted their sperm expenditure to the number of participating males, following the pattern predicted by game theory models. The pattern, however, was not always upheld: males increased their aggression level after a female had spawned and no longer adjusted their sperm expenditure to the number of sneaker males. Thus, adjusted sperm expenditure and mate guarding were two alternative responses to increased risk of sperm competition. Males adopted the tactic of sperm adjustment, when mate guarding and aggression against sneakers were costly in decreasing female willingness to spawn.
Stream position choice in salmon parr: maximisation of foraging efficiency
Authors: Carter T.
Published: December 2003

Juvenile Atlantic salmon or parr (Salmo salar L.) maintain station at certain locations in flowing stream water. This position choice is assumed to involve the maximization of energy intake, based upon food availability which is usually directly related to water flow rate. Conversely energy expenditure, including station holding behaviour, foraging and defending preferred sites, is inversely related to water flow rate. Adaptations of parr to life in fast flows implies that station holding is energetically inexpensive at water speeds up to the maximum sustained holding speed, which is fish specific, thus the most important energetic consideration for parr is the ability to maximize food intake. Ten groups of three parr were each observed for 60 min within an artificial stream tank over a heterogeneous substratum. Individual position choice and behaviour were recorded continuously. For each location chosen by the parr the potential upstream line‐of‐sight (LOS), defined as the maximum distance upstream that the water surface would be visible, was calculated. At those sites where foraging behaviour was observed, the mean upstream potential LOS was significantly greater than at sites where other behaviours were observed and at 400 randomly generated sites within the tank. When foraging, parr usually take food from the stream drift and there is a significant time expenditure on food location, identification and catching. Results presented here would seem to confirm that to maximize time available to make these decisions, a fish would be expected to maximize the distance over which it can observe potential food particles.
Costs and benefits of a cleaning mutualism
Authors: Cheney K. L. , Côté I. M.
Published: December 2003

Mutualisms can be thought of as ‘biological markets’ in which species trade resources, which can be manipulated by one or both participants. However, temporal and geographical variation in the outcome of mutualisms generates dynamic mosaics of co‐evolved interactions, therefore, outcomes of mutualistic interactions may be difficult to interpret with a ‘snapshot’ quantification of costs and benefits. Cleaning interactions are often used as classic examples of mutualism but assessing benefits to clients has been difficult. In this study we examined the outcome of the interaction between Caribbean cleaning gobies (Elacatinus evelynae) and longfin damselfish (Stegastes diencaeus), by comparing interactions at a number of locations. Previously we have shown that longfin damselfish benefit from cleaning interactions by a significant but small reduction in ectoparasite loads and we suggested that the costs of travelling and seeking cleaners by territorial damselfish may limit the net benefit of cleaning to the client (Cheney & Côté, 2001). Here, we investigate how the relationship alters between geographical locations and in one site, over 3 consecutive years, under varying environmental conditions to elucidate key components affecting cleaning symbioses.
The cost of cleanerfish mimics to their models
Authors: Côté I. M.
Published: December 2003

In aggressive mimicry, a ‘predatory’ species resembles a model that is harmless or beneficial to a third species, the ‘dupe’. Perhaps the most extraordinary case of aggressive mimicry occurs in Indo‐Pacific cleaning symbioses, where cleaner wrasses (the models) remove ectoparasites from larger fish clients. Several species of fangblennies mimic cleaners in behaviour and coloration. Instead of removing ectoparasites, however, fangblennies tear off fins, skin and scales from unsuspecting clients (the dupes). There is some debate over the extent to which cleanerfish mimics are really mimics because in some populations, the contribution of fish tissue to fangblenny diet is limited. In this study, I examine the impact of the resemblance between bluestriped fangblennies (Plagiotremus rhinorhynchus) and its putative model, the juvenile bluestreak cleaner wrasse (Labroides dimidiatus), on the model's cleaning activity to test the theoretical prediction that mimics should decrease the fitness of their models. I show that the presence of a bluestripe fangblenny in the vicinity of cleaner wrasses results in significantly lower client visit rates and inspection times compared to cleaners without a fangblenny nearby, and discuss why cleaner wrasses tolerate mimics near cleaning stations.
Detecting predator–prey relationships in the sea
Authors: Dulvy N. K. , Polunin N. V. C.
Published: December 2003

Understanding the strength and diversity of predator‐prey interactions among species is essential to understand ecosystem consequences of population‐level variation. Directly quantifying the predatory behaviour of wild fishes at large spatial scales (>100 m) in the open sea is fraught with difficulties. To date the only empirical approach has been to search for correlations in the abundance of predators and their putative prey. As an example we use this approach to search for predators of the keystone crown‐of‐thorns starfish. We show that this approach is unlikely to detect predator–prey linkages because the theoretical relationship is non‐linear, resulting in multiple possible prey responses for single given predator abundance. Instead we suggest some indication of the strength and ecosystem importance of a predator–prey relationship can be gained by using the abundance of both predators and their putative prey to parameterize functional response models.
On the interaction of turbulent flow and feeding behaviour of juvenile Atlantic Salmon (Salmo salar)
Authors: Enders E. C. , Buffin‐Bélanger T. , Boisclair D. , Roy A. G.
Published: December 2003

Anthropogenic activities can dramatically modify the riverine habitat of juvenile Atlantic salmon (Salmo salar). In the perspective of protecting and restoring the fluvial habitat, bioenergetic models are often used to estimate fish habitat quality. These models determine the habitat quality as the ratio between the energetic gains (food) and costs (growth, metabolism) of a fish. The energetic costs of swimming in a river are generally estimated using the average flow velocity without consideration of the effect of turbulence. Juvenile Atlantic salmon (JAS) live in rivers characterized by intense velocity fluctuations, which are often described as a succession of high‐ and low‐speed flow regions. These flow structures are likely to affect the JAS activity that consists of long periods of sit‐and‐wait at the top of a protuberant rock interrupted by short bursting motions to capture drifting food particles. To minimize the energetic costs, it is hypothesized that JAS use low‐speed flow regions to initiate and undertake their feeding motions. To improve bioenergetic modelling, this study aimed at analyzing the relation between turbulent flow structures and the feeding behaviour of JAS in a natural gravel‐bed river. We filmed eight JAS during 30 min with a submersible video camera while simultaneously measuring velocity fluctuations close to the fish in the St. Marguerite River, Quebec, Canada. Our results show that the proportion of time used for feeding motions decreases with increasing turbulent intensity and mean flow velocity; and that JAS do not seem to prefer low‐speed flow regions to initiate their feeding motions.
The relationship between dominance behaviour and growth as a function of habitat stability and community complexity: a test using salmon and trout
Authors: Höjesjö J. , Stradmeyer L. , Armstrong J. , Griffiths S.
Published: December 2003

When two or more species coexist, there is often a differentiation in habitat use, temporally and/or spatially, either due to differences in habitat preference or in competitive abilities. Trout and salmon, for example, often coexist in the same river but whereas trout generally occupy pools, salmon are more often found in riffles. This segregation might be due to differences in habitat preference but could also occur as a consequence of salmon being out‐competed by trout from the pools. Food in riffle sections has been found to be relatively unpredictable in time and space whereas pools are believed to be more spatially predictable. It should therefore be easier for fish to monopolize food resources in pools than riffles and hence the importance of dominance might be most significant for pool‐dwelling fish. In agreement with this theory, dominance have been shown to increase growth rate in brown trout whereas no such relationship has been found in salmon. This experiment was therefore designed to detect whether the relationship between growth rate and dominance in salmon might vary depending on whether they co‐exist with trout or are free to select pool habitat with no trout present. The experiment was carried out in an indoor stream landscaped with both pools and riffles and equipped with a feeding system designed to mimic natural spatial and temporal variation in food supply. This set up allowed us to perform controlled behavioural observations under near‐natural conditions. The results from this study will be presented and discussed.
New modelling of complex fish migration by application of chaos theory and neural network
Authors: Kim Y‐H.
Published: December 2003

Rules or patterns of movement or migration were still vague even for the main commercial fishes due to different routs in scale or in different, times resulting from complex environments to complex behaviour concept. The quantitative model of fish migration has been investigated using chaos theory to mimic more realistic fish movements by time steps from environmental and biological stimuli. The model uses three steps within a model neural network such as input stimuli, central decision‐making and response output in fish movements. The stimuli in the first step include the main physical (temperature, salinity, light, flow etc.) and biotic factors (prey, predator, life cycle etc.) which could be quantified as intensity parameters which were then normalized as ratios. The decision‐making process can be generated available signals for motor neuron using Lorenz chaos equations by the relevant stimuli. The response of fish movements from the output signal representing speed and direction can be re‐regulated as object‐oriented migration depending on physiological state or life cycle by third response filtering. The simulation results seen as 2‐dimensional seasonal migration for demersal fishes in the southern sea of the Korean Peninsula represented more realistic meandering tracks than the interpolated tracks in previous reports.
The myth of the sperm cloud – or why is testes size not affected by spawning mode in seahorses and pipefishes
Authors: Kvarnemo C. , Simmons L. W. , Ah‐King M. , Elofsson H.
Published: December 2003

One can predict fish species that spawn externally to have larger testes for their body size than internal fertilizers, to produce greater numbers of sperm as a response either to increased risk of sperm competition from sneaker males, or to counter the dilution of sperm in open water. Using museum specimen, we measured testis and body mass of 95 mature males, belonging to 21 genera of the family Syngnathidae (pipefishes and seahorses). In this family all species show paternal care, ranging from eggs being simply attached to the skin of the male, to completely enclosed in a brood pouch. The former unprotected group is thought to fertilize the eggs externally, whereas the latter protected group has internal fertilization, as the male fertilizes the eggs inside his own pouch. Hence, expecting smaller relative testis investment in the genera that have protected compared to unprotected brood care, to our surprise we found this not to be the case. Instead, all genera showed the same relationship between testis and body mass, regardless of brooding type. New results of ours, however, from Nerophis ophidion, a pipefish species that lacks brood pouch, show that the mode of fertilization in older literature (external fertilization after egg transfer when the male sinks through a sperm cloud) has been misjudged, and that this pipefish in fact, has internal fertilization inside the female before egg transfer. If this exciting finding proves to be true for other pouchless Syngnathids as well, the mystery of the museum data will be resolved.
Why there is better evidence for culture in fish than chimpanzees
Authors: Laland K. N.
Published: December 2003

Fish have comparatively small brains and are not renowned for their intelligence. Yet a series of laboratory experiments on the guppy reveals that they can be surprisingly good at learning from each other, and that social learning processes can mediate behavioural traditions analogous to the tool using traditions of different populations of chimpanzees. Transmission chain experiments have established that arbitrary and even maladaptive information can be socially transmitted among shoals of fish. Studies of behavioural innovation in guppies are strikingly consistent with findings of equivalent studies in primates. There are strong sex differences in innovatory tendencies and social learning abilities in guppies, which also parallel observations of primates. These studies suggest that the adage ‘necessity is the mother of invention’ may be a characteristic feature of animal innovation. When considered in combination with the findings of transfer experiments carried out on natural populations of fish, it becomes apparent that fish are an excellent model system for studies of animal social learning and culture.
Being there and getting there: balancing the costs of migration against the benefits of changing habitat for North Sea plaice
Authors: Metcalfe J. , Hunter E.
Published: December 2003

To improve survival and reproductive success, many fish species have evolved migratory life‐histories, showing ontogenetic and/or seasonal changes in habitat use. Individuals move between different areas, each of which is ‘best’ for a particular activity, such as feeding, growing or spawning. The benefits of moving to a different habitat, however, have to be balanced against the costs of migration, so any behaviour that reduces the cost of movement would be expected to expand the migratory range and thereby increase the range of habitats that can be exploited.

Previous tracking experiments in the southern North Sea have shown that plaice selectively exploit the tidal streams to aid their spawning migration. Here we examine whether this behaviour is primarily (1) an energy‐saving strategy, or (2) a transport mechanism by which fish that are unable to navigate over long distances can be carried reliably between feeding and spawning grounds. Because selective tidal stream transport requires that fish remain stationary on the sea‐bed during the ‘non‐transporting’ tide, energetic calculations predict that this behaviour is beneficial only when the current speed exceeds a critical, size‐dependent, value. We have used detailed information about migratory behaviour from individual fish to calculate the metabolic costs and the likely reproductive benefits of different migratory strategies. Our results show that plaice use selective tidal stream transport only in areas where the tidal streams are suitably fast, indicating that this behaviour is primarily an energy saving strategy.
Gender bent but not in the mind of fish
Authors: Nash J.
Published: December 2003

There is strong evidence that environmental exposure to endocrine disrupting chemicals (EDCs) is resulting in significant alterations to the reproductive system of many wildlife populations. Most of these studies measure chemically induced changes to the endocrine system or reproductive morphology and mostly provide simple markers of exposure. The heightened concern over the effects of EDCs is however primarily driven by the hypothesis that this disruption may have serious deleterious consequences on reproductive success. In extensive laboratory studies on breeding populations of zebrafish, I have shown that multigenerational exposure to environmentally relevant levels of endocrine disruptors cause very significant reductions in reproductive success. Lifetime exposure to 5 ng/l of ethynylestradiol, for example, caused complete reproductive failure. These reproductive failures were not caused by exposure proximate to the timing of spawning but by the disruption of development during earlier embryonic and larval sexual differentiation. Histology revealed that male gonads had not differentiated into functional testes. Significantly, these sterile males still initiated spawning in females and resulted in unfertilized eggs. This differential in the sensitivity of behaviour compared to gonadal disruption raises important issues in understanding the implications of endocrine disruption in wild populations. Moreover, the particular mode of reproduction behaviour that is used by a species fundamentally affects the population level impact of endocrine disruptors. This paper will discuss these results and how a greater understanding of the dynamics of group spawning may help in assessing the potential impact of endocrine disruption
Adaptive filial cannibalism in the beaugregory damselfish
Authors: Payne A.
Published: December 2003

Cannibalism of small numbers of offspring by a parent has been proposed as an adaptive parental strategy, by providing energy to support parental care. There are few empirical studies, however, to support this hypothesis. The beaugregory damselfish, Stegastes leucostictus, is a marine teleost that does not actively ventilate its eggs by fanning them. Partial cannibalism is common in this species, but in field studies was found to be unrelated to ration level. Filial cannibalism differed from predation in the pattern of egg eating; filial cannibalism was characterised by a random pattern of egg loss from a clutch rather than an aggregated distribution. Embryos developed quicker and had higher survival rates when they were at low densities and in nest sites where oxygen levels were high, and experimental reduction of oxygen levels increased rates of filial cannibalism. Here I present a hypothesis for filial cannibalism in the beaugregory damselfish; males cannibalise egg clutches in order to reduce clutch density and improve oxygen supply to the remaining embryos. I use a model of filial cannibalism to demonstrate how oxygen mediated cannibalism may be adaptive, and discuss the evolution of filial cannibalism in the beaugregory damselfish and other teleosts.