Migration of moth species in a network of small islands

Rapidly increasing fragmentation of natural landscapes decreases the ability of many species to reach the smaller and more isolated patches of habitat in a metapopulation. The densities of local populations of several moth species and the butterfly Hipparchia semele in a network of small islands, and the rates of inter-island movement and movement patterns, were investigated, to determine the factors affecting the rate and pattern of movements. The estimated population densities ranged from 0.001 to 0.2 individuals/m². The observed emigration and immigration rates depended on island isolation and various traits of the species, with great variability in migration rates among species. Thin-bodied, slow-flying species did not move among the islands, whereas many robust, fast-flying species moved among the islands relatively frequently. Migration rate increased significantly with body size and was significantly higher in oligophagous than in polyphagous species, suggesting that these factors are important determinants of the migration rate of the species. Migration rate was low when the surface temperature of the sea was low, and a greater proportion of individuals emigrated from small than large patches of habitat. The migration distances of female noctuids were shorter than those of males and those of both sexes of the butterfly H. semele. The observed movement patterns are consistent with a metapopulation structure in most of the moth species.     

Anopheles culicifacies giles: Adult ecological parameters measured in rural punjab province,pakistan using capture-mark-release-recapture and dissection methods,with comparative observations onAn. stephensi liston andAn. subpictus grassi

Dispersal, immigration and emigration rates, horizontal and vertical survivorship and absolute population size were estimated for micropopulations of An. culicifacies, An. stephensi and An. subpictus at a series of cattle sheds in rural Punjab Province, Pakistan, during November 1979 and May 1980 using capture-mark-release-recapture and dissection methods. Dispersal was temperature-related, with populations more vagile during May. Mean dispersal distance per individual was low for all species. More than 70% of all recaptures were taken at the point of release and the longest detected flight was 1250 meters. Horizontal survivorship was greater during November and was always less than vertical survivorship calculated from dissection agegrading data. Survivorship during the nulliparous period was greater than survivorship throughout total life, indicating the survivorship curve may be slightly sigmoid. Daily population sizes of endemic and immigrating females and males were calculated usingBailey 's (1952) modification of the Lincoln Index, with the daily captures adjusted for immigration which was highest in May. Daily additions to the indoor resting population exclusive of immigrants were estimated using the method ofManly andParr (1968). The relationship of the present findings to malaria transmission and genetic control were discussed.     

Dispersal in a metapopulation of the bush cricket, Metrioptera bicolor (Orthoptera: Tettigoniidae)

1. I present a stochastic simulation model that describes individual movements of Metrioptera bicolor Philippi in a heterogeneous landscape, consisting of patches of suitable habitat surrounded by a matrix of unprofitable habitats. Although the model is parameterized with information about daily movement behaviour, it can generate spatially explicit predictions about inter-patch dispersal rates for much longer periods, e.g. one generation.
2. Long-term dispersal experiments were conducted to evaluate model predictions. Patch-specific emigration rates and the total distance moved by individuals could be predicted with satisfactory precision. Because of the stochastic nature of the model, it failed to predict which recipient patches emigrating individuals actually chose in a particular situation.
3. Spatially explicit simulations of the movement model were made for the whole natural distribution area of M. bicolor . The results suggest that emigration rates are negatively correlated with patch size. Local populations occurring on small patches may be more prone to extinction than those on large patches, by losing more emigrants than are compensated for by immigration.     

The rise and fall of local populations of ortolan buntings Emberiza hortulana: importance of movements of adult males

Changes in population size of local populations of birds have usually been interpreted in relation to adult return rate and recruitment of young individuals after natal dispersal. Little is known about the importance of redistribution of adult individuals through breeding dispersal. The small Norwegian population of ortolan buntings Emberiza hortulana has a patchy distribution with about 30 long‐term local populations. During a period of general population decline (29% decrease over 7 years), the population trends of local populations (measured as number of males recorded) were highly variable, with some even increasing four‐fold. Comparisons of demographic parameters showed that adult immigration rate (i.e. dispersal of adult males) explained both yearly changes in male population size and population trends over the whole study period better than adult return rate or adult emigration rate, or a measure of recruitment of young males. Adult immigration rates and recruitment rates were correlated, suggesting that both young and adult males find the same places attractive. In the study area, adult sex ratio was strongly male‐biased, and immigration rate was higher when local sex ratio was less skewed. In addition, less skewed sex ratio was related to higher adult return rate and lower emigration rate. We found no relationships between measures of breeding success and population change. We suggest that conspecific attraction may explain the observed patterns. Some local populations may act as hot‐spots attracting adult males from other populations. Thus, local population changes need not reflect overall population growth rate, but may be a consequence of redistribution of adult birds.     

Population dynamics and production of Daphnia hyalina in a eutrophic reservoir

The population dynamics and production of Daphnia hyaiina^ the dominant cladoceran i n Eglwys Nynydd, a shallow eutrophic reservoir in South Wales, were studied for 2 years against a background of limnological measurements. The appearance and development of successive generations from egg to adult could be followed from changing numbers in arbitrarily defined size classes. Seasonal variations in mean length, mean brood-size and proportion of gravid adults were recorded and mean brood-size was related to changing food and temperature conditions. Egg-development times for D. hyaiina were determined in culture and the population parameters finite birth (S), instantaneous birth (b′), instantaneous population change (r′), instantaneous death (d′) and finite death rates (D) were estimated from field data. Turnover and production estimates were calculated from finite death rates and biomass. The calculated potential rate of increase (b′) was nearly always greater than the observed rate of increase (r′): seasonal changes in death rate (d′) generally parallel changes in birth rate (b′) but remain somewhat out of phase. Population oscillations are probably due t o a delay in the expression of the effects of population density upon birth and death rates. The mean biomass of Daphnia in 1970 was 0-57 mg dry wt/l (0-88 g C/m²) and in 1971 0-32 mg dry wt/l (0.49 g C/m²). Annual production for Daphnia was 11-8 mg dry wt/l (18-2 g C/m²) in 1970 and 8-30 mg dry wt/l (12 8 g C/m²) in 1971. Information available on primary production in the reservoir suggests that the production of Daphnia accounts for less than 2% of gross primary production. However, the pattern of population growth of Daphnia in Eglwys Nynydd almost certainly reflects a food limited system. In summer, blue-green algae may be abundant but serve as a poor food source: throughout the blue-green bloom egg production remains low, at times remaining below 0-5 eggs/adult.     

Dynamics of mutualist populations that are demographically open

1. Few theoretical studies have examined the impact of immigration and emigration on mutualist population dynamics, but a recent empirical study (A.R. Thompson Oecologia, 143, 61-69) on mutualistic fish and shrimp showed that immigration can prevent population collapse, and that intraspecific competition for a mutualistic partner can curb population expansion. To understand in a theoretical context the implications of these results, and to assess their generality, we present a two-species model that accounts explicitly for immigration and emigration, as well as distinguishing the impacts of mutualism on birth rates, death rates and habitat acquisition. 2. The model confirms that immigration can stabilize mutualistic populations, and predicts that high immigration, along with enhanced reproduction and/or reduced mortality through mutualism, can cause population sizes to increase until habitat availability curbs further expansion. 3. We explore in detail the effects of different forms of habitat limitation on mutualistic populations. Habitat availability commonly limits the density of both populations if mutualists acquire shelter independently. If a mutualist depends on a partner for habitat, densities of that mutualist are capped by the amount of space provided by that partner. The density of the shelter-provider is limited by the environment. 4. If a mutualism solely augments reproduction, and most locally produced individuals leave the focal patch, then the mutualism will have a minimal effect on local dynamics. If the mutualism operates by reducing rates of death or enhancing habitat availability, and there is at least some immigration, then mutualism will affect local dynamics. This finding may be particularly relevant in marine systems, where there is high variability (among species and locations) in the extent to which progeny disperse from natal locations. 5. Overall, our results demonstrate that the consequences of immigration and emigration for the dynamics of mutualists depend strongly on which demographic rate is influenced by mutualism. 6. By relating our model to a variety of terrestrial and aquatic systems, we provide a general framework to guide future empirical studies of the dynamics of mutualistic populations.     

Dispersal of deer mice,Peromyscus maniculatus

Summary Dispersal of deer mice, Peromyscus maniculatus, was measured as immigration to and emigration from two control areas, and as immigration to a removal area. The number of mice dispersing was linearly related to the densities on the control areas, while the proportion of the population dispersing (rate of dispersal) was correlated primarily with the rate of increase of control populations. High rates of dispersal were also associated with a breakdown of the established social structure in the spring and fall. Dispersing animals were compared to residents with respect to sex ratio, weight, age, and breeding condition. The types of animals dispersing varied seasonally: light-weight, non-breeding males dispersed in the spring and summer; juveniles and breeding males dispersed at the end of the breeding season; and light-weight mice of both sexes dispersed over the winter. It is proposed that the animals that dominated the dispersal samples each season were moving in response to social pressure from residents, or local limitations of some resource, and thus, that dispersal was adaptive for the individuals concerned. Some tests of the hypotheses concerning resource limitation are suggested.     

Production of trout,Salmo trutta,in a Danish stream

Synopsis The numbers of trout,Salmo trutta, in Granslev », Denmark, were estimated by the removal method on 18 dates from March 1974 to March 1976. Populations density varied from 0.39 to 0.74 trout m^–2 in 1974–1975 and from 0.36 to 0.59 m^–2 in 1975–1976 and at all times four or five year classes were present. The age structure of the population was unstable and the variable natural survival, immigration into and emigration from the study site could not be separated. An annual growth cycle with the most rapid growth for all year classes taking place from May to early August was found. Statistically significant differences between different years occurred in the growth of the 0,I and II age groups, but no evidence of density-dependent growth was found. The biomass ranged from 35.4 to 9.5 g m^–2. The total mean annual biomass was 22.8 and 14.7 g m^–2 in the two years and the II group made the greatest contribution, 44 and 48%, respectively. During 1975–1976 the mean annual biomass of each year class only was about two-thirds of that in 1974–1975. Annual production in the two years was 25.7 (range 24.7–28.5) and 12.6 g m^–2 (range 11.7–15.0) and the II group accounted for about 46 and 38% of the production. In addition eel,Anguilla anguilla, produced about 0.5 g m^–2 yr^–2. The unstable age structure of the trout population was compared with trout populations from other streams. The importance of immigration as a recruitment process in middle and lower reaches of streams and of migrations as a mechanism to optimise utilization of the total stream habitat, as well as temperature as a factor controlling the growth rate are discussed.     

Migratory movements of pacu, Piaractus mesopotamicus, in the highly impounded Paraná River

A mark‐recapture study was conducted in 1997–2005 to investigate movements of stocked pacu, Piaractus mesopotamicus, in the Paraná River Basin of Brazil, Paraguay, and Argentina. Fish raised in cages within the Itaipu Reservoir and in ponds were tagged externally (n = 2976) and released in the Itaipu Reservoir (53.2%) and bays of its major tributaries (46.8%). In total, 367 fish (12.3%) were recaptured. In all, 91% of the pacu moved away from the release site; upstream movements were more extensive than downstream movements. Pacu traveled upstream a maximum of 422 km (average of 41.3 km) at a maximum rate of 26.4 km day⁻¹ (av. 0.8). Downstream movements were limited in terms of number of individuals and distance moved. Fish released during the wet season moved farther than those released during the dry season, and feeding rather than spawning might have been the compelling reason for movement. Although fish passed downstream through dams, none of the marked fish were detected to have moved upstream through the passage facilities. Pacu showed movement patterns not radically different from those of other neotropical migratory species, but their migratory movements may not be as extensive as those of other large migratory species in the basin.     

Negative density-dependent emigration of males in an increasing red deer population

In species with polygynous mating systems, females are regarded as food-limited, while males are limited by access to mates. When local density increases, forage availability declines, while mate access for males may increase due to an increasingly female-biased sex ratio. Density dependence in emigration rates may consequently differ between sexes. Here, we investigate emigration using mark-recovery data from 468 young red deer Cervus elaphus marked in Snillfjord, Norway over a 20-year period when the population size has increased sixfold. We demonstrate a strong negative density-dependent emigration rate in males, while female emigration rates were lower and independent of density. Emigrating males leaving the natal range settled in areas with lower density than expected by chance. Dispersing males moved 42 per cent longer at high density in 1997 (37 km) than at low density in 1977 (26 km), possibly caused by increasing saturation of deer in areas surrounding the marking sites. Our study highlights that pattern of density dependence in dispersal rates may differ markedly between sexes in highly polygynous species. Contrasting patterns reported in small-scale studies are suggestive that spatial scale of density variation may affect the pattern of temporal density dependence in emigration rates and distances.     

A population study in Jamaica on adult Sceliphron assimile (Dahlbom) (Hymenoptera: Sphecidae)

Abstract.

• 1 A mark–recapture study on the sphecid wasp Sceliphron assimile (Dahlbohm), analysed by Jolly's stochastic method (1965), was made from 3 December 1974 to 22 February 1975 at Green Bay, St Catherine, Jamaica.
• 2 Population levels in an 18.2 ha study area fluctuated about a mean of 281 for males, 259 for total females and 87 for reproducing females, while the probable carrying-capacity for these reproductives was about 104.
• 3 Mean estimated daily survival rates were 0.903 for males, 0.924 for total females and 0.945 for reproducing females. For the first two categories these rates decreased (p < 0.02) during the study, probably reflecting increasing emigration. Reproducing females probably do not emigrate and their survival did not significantly decrease.
• 4 Minimum age was linearly related to wing wear (r=+0.69, P < 0.001) and the latter associated with the progressive maturation and ageing of the ovaries. All surviving females become parous by middle age.
• 5 The mean rate of fecundity in the field was dependent on female age and was reduced during prolonged drought. Curves of total achieved fecundity appropriate to realistic survival rates give 4.2–16.8 eggs/female. The Jamaican mean was 9.6 ± 2.3 and that for Green Bay 8.6.
• 6 The proportion of females in the Green Bay population was 0.48 ± 0.03 while 0.55 was expected at emergence.
• 7 A cyclic budget is used to estimate immigration and emigration, and these were important causes of population change.
• 8 For Jamaica, only an estimated 28% of females survived to nest.

     

Higher mobility of butterflies than moths connected to habitat suitability and body size in a release experiment

Mobility is a key factor determining lepidopteran species responses to environmental change. However, direct multispecies comparisons of mobility are rare and empirical comparisons between butterflies and moths have not been previously conducted. Here, we compared mobility between butterflies and diurnal moths and studied species traits affecting butterfly mobility. We experimentally marked and released 2011 butterfly and 2367 moth individuals belonging to 32 and 28 species, respectively, in a 25 m × 25 m release area within an 11‐ha, 8‐year‐old set‐aside field. Distance moved and emigration rate from the release habitat were recorded by species. The release experiment produced directly comparable mobility data in 18 butterfly and 9 moth species with almost 500 individuals recaptured. Butterflies were found more mobile than geometroid moths in terms of both distance moved (mean 315 m vs. 63 m, respectively) and emigration rate (mean 54% vs. 17%, respectively). Release habitat suitability had a strong effect on emigration rate and distance moved, because butterflies tended to leave the set‐aside, if it was not suitable for breeding. In addition, emigration rate and distance moved increased significantly with increasing body size. When phylogenetic relatedness among species was included in the analyses, the significant effect of body size disappeared, but habitat suitability remained significant for distance moved. The higher mobility of butterflies than geometroid moths can largely be explained by morphological differences, as butterflies are more robust fliers. The important role of release habitat suitability in butterfly mobility was expected, but seems not to have been empirically documented before. The observed positive correlation between butterfly size and mobility is in agreement with our previous findings on butterfly colonization speed in a long‐term set‐aside experiment and recent meta‐analyses on butterfly mobility.     

Source populations in carnivore management: cougar demography and emigration in a lightly hunted population

Wildlife agencies typically attempt to manage carnivore numbers in localized game management units through hunting, and do not always consider the potential influences of immigration and emigration on the outcome of those hunting practices. However, such a closed population structure may not be an appropriate model for management of carnivore populations where immigration and emigration are important population parameters. The closed population hypothesis predicts that high hunting mortality will reduce numbers and densities of carnivores and that low hunting mortality will increase numbers and densities. By contrast, the open population hypothesis predicts that high hunting mortality may not reduce carnivore densities because of compensatory immigration, and low hunting mortality may not result in more carnivores because of compensatory emigration. Previous research supported the open population hypothesis with high immigration rates in a heavily hunted (hunting mortality rate=0.24) cougar population in northern Washington. We test the open population hypothesis and high emigration rates in a lightly hunted (hunting mortality rate=0.11) cougar population in central Washington by monitoring demography from 2002 to 2007. We used a dual sex survival/fecundity Leslie matrix to estimate closed population growth and annual census counts to estimate open population growth. The observed open population growth rate of 0.98 was lower than the closed survival/fecundity growth rates of 1.13 (deterministic) and 1.10 (stochastic), and suggests a 12–15% annual emigration rate. Our data support the open population hypothesis for lightly hunted populations of carnivores. Low hunting mortality did not result in increased numbers and densities of cougars, as commonly believed because of compensatory emigration.     

A protocol for quantifying the birth, death and emigration rates of produce-associated bacteria, illustrated by its application to Salmonella enterica serovar Typhimurium on cultivated mushrooms

Colony counts, counts of immunostained cells, fluorescent assays for cell viability and titration of a superinfecting bacteriophage were incorporated into a protocol for studying the growth kinetics of produce-associated bacteria in vivo. A set of equations was assembled for measuring the true rates of birth, death and emigration of the bacteria within the frame of a "transit growth" model, thus allowing the independent measurement of the carrying capacity of the substrate and of the overall productivity of the system. Implementation of the protocol on two species of cultivated mushrooms inoculated with Salmonella enterica serovar Typhimurium showed that large bacterial populations developed on Agaricus bisporus A15 but emigration was not detected, whereas resident populations on Agrocybe aegerita FAR142 amounted to 79.7%, 65.1% and 80.7% of the cultivable, dead and total bacterial cells produced, owing to emigration.     

Deconstructing insect herbivore trivial movement in a monoculture and triculture: Limitations of emigration

Significantly higher population densities of a squash pest beetle, Acalymma vittatum, were observed in a squash monoculture than a triculture of squash, maize, and beans. One hypothesis for such differences is that non-host plants in the triculture cause the herbivore to move more frequently resulting in higher emigration rates from the tricultures. Plant to plant movement of the beetle was studied in vegetative winter squash to evaluate if differences in components of trivial movement would generate a higher emigration rate from the triculture. Tenure times were shorter on plants in the triculture than on plants in the squash monoculture, there was no movement directionality, movement distances were greater in squash monocultures than in tricultures and were greater during July than August. In the tricultures, plant-to-plant transitions were primarily to maize from non-host plants and to beans or squash from host plants during July, but during August, movement from any plant was primarily to maize. We integrated the values of the movement components from vegetative winter squash into a simple Markov model, and found that during July, emigration was estimated to be faster from the triculture than the monoculture, supporting the hypothesis. However, in August, emigration was estimated to be slower from the triculture. In August, maize plants were tall and, by acting like a fence, greatly reduced the movement distance of beetles. The effect of the differences in emigration rate on beetle population density was greatest for small patches, indicating that emigration may be important only in small-scale production systems.     

Survival,site fidelity,and the population dynamics of Piping Plovers in Saskatchewan

ABSTRACT To conserve threatened species, managers require predictions about the effects of natural and anthropogenic factors on population growth that in turn require accurate estimates of survival, birth, and dispersal rates, and their correlation with natural and anthropogenic factors. For Piping Plovers (Charadrius melodus), fledging rate is often more amenable to management than adult survival, and population models can be used to estimate the productivity (young produced per breeding female) necessary to maintain or increase populations for given levels of survival. We estimated true survival and site fidelity of adult and subadult (from fledging to second year) Piping Plovers breeding in Saskatchewan using mark‐resight data from 2002 to 2009. By estimating true survival rather than apparent survival (which is confounded with permanent emigration), we were able to provide more accurate projections of population trends. Average adult and subadult survival rates during our study were 0.80 and 0.57, respectively. Adult survival declined over time, possibly due in part to the loss of one breeding site to flooding. Average adult and subadult site fidelity were 0.86 and 0.46, respectively. Adult site fidelity declined during our study at two study sites, most strongly at the flooded site. Male and female Piping Plovers had similar survival rates, but males had greater site fidelity than females in some years. Based on our survival estimates, productivity needed for a stationary population was 0.75, a benchmark used for plover management on the Atlantic Coast, but not previously estimated for Prairie Canada. In stochastic simulations incorporating literature‐based variation in survival rates, productivity needed for a stationary population increased to 0.86, still lower than that previously estimated for western populations. Mean productivity for our study sites ranged from 0.87 to 0.96 fledged young per pair. Our results suggest that fledging rates of Piping Plovers in Saskatchewan were sufficient to ensure a stationary or increasing population during our study period. However, large‐scale habitat changes such as drought or anthropogenic flooding may lead to dispersal of breeding adults and possibly mortality that will increase the fledging rate needed for a stationary population.     

Migration and Allee effects in the six-spot burnet moth Zygaena filipendulae

Abstract 1. Migration into local populations may increase the likelihood of persistence but emigration may decrease the persistence of small and isolated populations. The dispersal behaviour of a day-flying moth Zygaena filipendulae was examined to determine whether emigration is correlated positively or negatively with population size and host plant density.
2. A mark–release–recapture study showed that most moths moved small distances (< 40 m on average) and only 6% of movements were > 100 m.
3. Twenty-five individuals moved between populations, a measured exchange rate of 8%. Moths were more likely to move between patches that were close together and they moved to relatively large patches.
4. The fraction of residents increased with increasing population size in the patch and increasing host plant cover. Relatively high proportions of individuals left small patches with small moth populations.
5. Moths released in grassland lacking Lotus corniculatus (the host plant) tended to leave the area and biased their movement towards host plant areas, whereas those released within an area containing L. corniculatus tended to stay in that area.
6. Biased movement away from small populations and areas of low host plant density (normally with low population density) was found. This migration-mediated Allee effect is likely to decrease patch occupancy in metapopulations, the opposite of the rescue effect. The effects on metapopulation persistence are not known.     

Feeding rate may affect dispersal in the orb-web spider Nephila clavata

Population parameters of the orb-web spider Nephila clavata were estimated at two sites with different spider densities (for 2 successive years at the high density site and 1 year at the low density site), and the relationship between survival rate and feeding conditions was examined. The rate of decrease of population density was almost constant over time and nearly the same at the two sites. Daily survival rate (sum of the effects of mortality and emigration) was low during August to early September and increased markedly thereafter. Daily immigration rate (number of immigrants/number of residents) was high during August to early September. Since there were strong negative correlations between survival and immigration rates, low survival rate seems to be caused by a high rate of emigration. Strong positive correlations were found between survival rate and feeding frequency (mean percent observed feeding). Analysis of covariance revealed that the parameters of the regression between survival rate and feeding frequency did not differ significantly among three occasions. These results suggest that feeding condition has a significant influence on dispersal activity of populations in this spider.     

Interpatch movement and edge effects: the role of behavioral responses to the landscape matrix

Animal interpatch movement and spatial distribution are known to be influenced substantially by the composition of the landscape matrix, but little is known about the underlying mechanisms. In previous mark–recapture experiments we have found that the rates of emigration and immigration for the planthopper Prokelisia crocea are greater within a matrix composed of the introduced grass smooth brome (Bromus inermis) than a mudflat matrix. Additionally, census data indicated that individuals aggregate near the edge of host‐plant patches (prairie cordgrass; Spartina pectinata) bordered by mudflat, but not in patches bordered by nonhost grasses such as brome. Here, we investigate the mechanistic basis of these matrix effects by tracking the individual movements of planthoppers released at the edge of brome‐ and mudflat‐bordered cordgrass patches, and within homogeneous habitats of each type (cordgrass, brome, and mudflat). We found that patch edges bordered by brome were three times more permeable to emigration than mudflat‐bordered edges. Also, planthoppers exhibited no tendency to avoid edges by moving away (i.e. towards the patch interior). Within homogeneous habitats, comparison of the fractal dimension of movement paths revealed that movement was more linear in mudflat than in brome or cordgrass. In addition, planthoppers exhibited greater step lengths (distance moved per 10‐min interval), shorter residency times (duration of pauses between movements), and greater rates of net linear displacement in mudflat than brome and cordgrass. We attribute the planthopper's distributional patterns within patches to the lower permeability of mudflat than nonhost grass edges and the absence of edge–avoidance behavior. Contrary to conventional wisdom that low‐resistance matrix types (e.g. those that promote high displacement rates) enhance interpatch dispersal rates, dispersal success may be higher in brome matrix because tortuous movement through this matrix increases the planthopper's rate of encounter with cordgrass patches.     

The breeding-season population structure of three sympatric, territorial sticklebacks (Pisces: Gasterosteidae)

Animals breeding only once late in life should spend most of the time during their one reproductive season attempting to reproduce. Contrary to this prediction, we found that the individuals of three species of sticklebacks (Pisces: Gasterosteidae) spent very short periods of time on their breeding ground. Tidal flooding of the site controlled patterns of fish immigration and emigration. Inundations early in the breeding season brought in new immigrants which replaced most resident fish. However, towards the end of the breeding season there was less immigration and a higher percentage of the residents remained in their pools. We expected to see movements among pools by surplus males searching for sites to establish a territory; instead, few fish moved among pools, and most of those that did were females. A high energetic cost of breeding in this unstable habitat may best explain these residency patterns.