Changes in commercially fished shellfish stocks and shorebird populations in the Wash, England

The Wash, in eastern England, supports internationally important populations of 11 species of shorebird. A major commercial shellfishery provides potential conflict between fishermen and nature conservation interests. During the 1990s, high fishing mortality and low recruitment substantially reduced the stocks of cockle (Cerastoderma edule) and mussel (Mytilus edulis). Population models, constructed from estimates of survival and recruitment, indicated that declines in the availability of cockles and mussels were associated with changes in oystercatcher (Haemotopus ostralegus) survival between 1970 and 1998, including three periods of mass mortality, and also the recruitment of juvenile birds to both oystercatcher and knot (Calidris canutus) populations. Emigration of knot may also have taken place. Cockle recruitment was dependent on climatic conditions, whereas mussel populations tended to be stable. The decline in mussel stocks, due to over-fishing, increased the vulnerability of the oystercatcher population to mass-mortality episodes in poor cockle years. The key to preventing major oystercatcher kills in future is to ensure sufficient mussels are available in poor cockle years. Recent cultivation of mussels in inter-tidal areas has been beneficial and is an important management tool for maintaining bird populations.     

The evaluation of key sites for breeding waders in lowland Scotland

This study considers the selection of sites based on the densities of breeding waders that would be considered to be distributed widely across common habitats in Scotland: so-called ‘wider countryside’ species. Five methods to provide a hierarchical classification of sites are assessed. Fifty percent of the populations of redshank (Tringa totanus) and snipe (Gallinago gallinago) occur on just 2 and 4.5% of Scottish lowlands, respectively, yet neither are suitably protected by conservation measures and both would benefit from a carefully targeted approach to their conservation. Three species, lapwing (Vanellus vanellus), curlew (Numenius arquata) and oystercatcher (Haematopus ostralegus) are more appropriately considered to be dispersed species. We propose that, if the density of a breeding wader on a site exceeds the threshold level predicted for the top 1% of Scottish lowland for that species, and if the area of the site exceeds 1 km² then that site be considered to be a key site for farmland waders. The minimum density (in pairs km⁻²) must exceed 16.8 for lapwing, 10.1 for oystercatcher, 6.1 for snipe, 7.5 for curlew or 3.6 for redshank.     

Critical thresholds of disturbance by people and raptors in foraging wading birds

Intertidal areas support during the non-breeding season many wading birds Charadrii that may often take flight in response to the presence of people or of birds of prey on their intertidal feeding and roosting grounds. Disturbance can cause birds to spend energy flying away and to lose feeding time while relocating to different feeding areas, where the increased bird densities may intensify competition from interference and, if of sufficient duration, from prey depletion. Until now, there has been no method for establishing how frequently birds can be put to flight before their fitness is reduced. We show how individual-based behavioural models can establish critical thresholds for the frequency with which wading birds can be disturbed before they die of starvation. It uses oystercatchers Haematopus ostralegus in the baie de Somme, France where birds were put to flight by disturbance up to 1.73 times/daylight hour. Modelling shows that the birds can be disturbed up to 1.0-1.5 times/h before their fitness is reduced in winters with good feeding conditions (abundant cockles Cerastoderma edule and mild weather) but only up to 0.2-0.5 times/h when feeding conditions are poor (scarce cockles and severe winter weather). Individual-based behavioural models enable critical disturbance thresholds to be established for the first time.     

Mass mortality of common eiders (Somateria mollissima) in the Dutch Wadden Sea, winter 1999/2000: starvation in a commercially exploited wetland of international importance

Mass mortality of common eiders (Somateria mollissima) was observed in winter 1999/2000 in the Dutch Wadden Sea. Approximately 21,000 common eiders died. Dissected birds were severely emaciated and 94% were infected with the acanthocephalan parasite Profilicollis botulus. Green shore crabs (Carcinus maenas), intermediate hosts of the parasite, were slightly more ‘available’ than in other years, but parasite infections in the eiders were close to normal. Few eiders were oiled (5%), there were no toxicological, bacteriological, or virological explanations for the observed mortality.In the Wadden Sea, a wetland of international importance, mussel (Mytilus edulis) cultures occur in sublittoral areas, while mechanical cockle (Cerastoderma edule) fisheries are licensed annually after evaluation of available resources. The wintering eiders in 1999/2000 required c. 3.1 million kg ash-free dry mass, while information on mussel and cockle stocks (irrespective of accessibility and profitability) suggested a resource 4.7× the requirement of common eiders only. Food shortage is suggested to have caused the observed mortality, involving both principal (mussels and cockles) and secondary (Spisula) prey.Winter census reports showed shifts in wintering distribution of common eiders in the 1990s, indicating the utilisation of Spisula in the North Sea in poor food years in the Wadden Sea. Following particularly intense fisheries in summer 1999, attempts to feed on Spisula in winter 1999/2000 failed. It is hypothesised that overfishing of mussels and cockles in the Wadden Sea in the early 1990s resulted in structurally reduced food resources, contractions of the foraging area of common eiders, and increased use of secondary prey in the North Sea.     

The recent decline of a New Zealand endemic: how and why did populations of Archey's frog Leiopelma archeyi crash over 1996-2001?

Dramatic changes have been documented in New Zealand's vertebrate faunas since human settlement, involving major declines and extinctions, but over recent years few species have declined in numbers so rapidly as the terrestrial Archey's frog Leiopelma archeyi (Anura: Leiopelmatidae). Long-term monitoring over more than 20 years revealed a major population reduction of the species over 1996-2001 and L. archeyi is now classified as Nationally Critical under the New Zealand threat classification system. The decline progressed northwards in the Coromandel ranges, and mostly larger (female) frogs survived. On a 100 m² study plot at Tapu Ridge, annual population estimates averaged 433 frogs (SE ±32) over 1984-1994, declining by 88% to average 53 frogs (SE ±8) over 1996-2002. A mean annual survival rate of 82% for most years declined to 33% over 1994-1997. There is mounting evidence to suggest that disease is the major agent of decline, supported by (1) the rapidity and severity of decline, (2) the progressive (south to north) nature of decline, and (3) finding frogs with chytriodiomycosis from Batrachochytrium dendrobatidis at the time of decline. Surprisingly, sympatric populations of the semi-aquatic Leiopelma hochstetteri have not declined dramatically, nor has a western population of L. archeyi at Whareorino, despite chytridiomycosis occurring in some frogs there. Sustaining and restoring populations of L. archeyi in New Zealand raises major challenges for conservation management.     

Predicting survival, reproduction and abundance of polar bears under climate change

Polar bear (Ursus maritimus) populations are predicted to be negatively affected by climate warming, but the timeframe and manner in which change to polar bear populations will occur remains unclear. Predictions incorporating climate change effects are necessary for proactive population management, the setting of optimal harvest quotas, and conservation status decisions. Such predictions are difficult to obtain from historic data directly because past and predicted environmental conditions differ substantially. Here, we explore how models can be used to predict polar bear population responses under climate change. We suggest the development of mechanistic models aimed at predicting reproduction and survival as a function of the environment. Such models can often be developed, parameterized, and tested under current environmental conditions. Model predictions for reproduction and survival under future conditions could then be input into demographic projection models to improve abundance predictions under climate change. We illustrate the approach using two examples. First, using an individual-based dynamic energy budget model, we estimate that 3-6% of adult males in Western Hudson Bay would die of starvation before the end of a 120 day summer fasting period but 28-48% would die if climate warming increases the fasting period to 180 days. Expected changes in survival are non-linear (sigmoid) as a function of fasting period length. Second, we use an encounter rate model to predict changes in female mating probability under sea ice area declines and declines in mate-searching efficiency due to habitat fragmentation. The model predicts that mating success will decline non-linearly if searching efficiency declines faster than habitat area, and increase non-linearly otherwise. Specifically for the Lancaster Sound population, we predict that female mating success would decline from 99% to 91% if searching efficiency declined twice as fast as sea ice area, and to 72% if searching efficiency declined four times as fast as area. Sea ice is a complex and dynamic habitat that is rapidly changing. Failure to incorporate climate change effects into population projections can result in flawed conservation assessments and management decisions.     

Low frequency of anti-acetylcholinesterase pesticide poisoning in lesser and Eurasian kestrels of Spanish grassland and farmland populations

Lesser kestrel Falco naumanni and Eurasian kestrel Falco tinnunculus are two small raptor species commonly breeding in open agro-pastoral systems that have suffered a dramatic decline in their populations during the past few decades due to changes in land use. Direct intoxication by chemicals used in farming has been one of the causes proposed promoting population declines in both species. However, there have been no studies exploring the degree of kestrel intoxication at individual or population levels in the wild. We investigated the inter-population variation in blood levels of acetylcholinesterase (AChE) in nestlings of Spanish Lesser and Eurasian kestrels. AChE was used as an estimator of the degree of organophosphorus (OP) and/or carbamate (CB) exposure or intoxication. In addition, we measured the albumin-globulin ratio (A/G) as an index of general health status. We found only extremely low AChE levels in lesser kestrels from one of the seven studied populations. In addition, we did not find differences in nestling AChE levels between pastoral and agricultural habitats. Furthermore, the present study revealed that two of the seven lesser kestrel populations are suffering from poor health conditions, in one case due to OP-CB poisoning, and the other possibly due to a pathogen infection as suggested by the low A/G ratio observed. Thus, our study suggests that, in general, OP and/or CB pesticide poisoning in traditional agro-pastoral systems in Spain is not currently an important conservation factor for either Lesser or Eurasian kestrels chicks.     

Control of one invasive plant species allows exotic grasses to become dominant in northern Great Plains grasslands

Decline of leafy spurge (Euphorbia esula) in the northern Great Plains of the US is generally viewed as a success story for biological control, but quality of the vegetation that survived the infestation is key to recovery of ecosystem function. In addition, effects of other invasive species, notably cool-season exotic grasses, must be taken into account. Objectives of this study were (1) to evaluate direction and significance of changes in biomass of native and exotic grasses, forbs, and leafy spurge and in plant species composition following control of leafy spurge by flea beetles and (2) to evaluate the relative effects of leafy spurge and exotic grasses on biomass of native grasses, biomass of forbs, and richness of native species. We monitored species composition (1998-2003 and 2008) and biomass (2000, 2002, 2003 and 2008) of these groups on spurge-infested and noninfested permanent plots at three sites with unbroken prairie sod in North Dakota, USA. We found little evidence, in terms of species richness or biomass of native grasses or forbs, that leafy spurge was being replaced by desirable native species, although desirable as well as weedy and exotic species were characteristic of 2008 vegetation at all three sites. Structural equation models revealed that leafy spurge had temporally intermittent negative effects on forb biomass and species richness, but no effects on native grasses. In contrast, exotic grass had consistently strong, negative effects on native grass biomass, as well as stronger negative effects than leafy spurge on native species richness. Although substantial native plant diversity remains at these sites, exotic grasses pose an important threat to these crucial building blocks of native prairie ecosystems.     

A risk analysis for the common hamster (Cricetus cricetus)

The common hamster (Cricetus cricetus) has suffered a dramatic decline in Western Europe though the species is characterized by an extremely high reproductive potential. An individual-based model was developed to determine the risk factors which lead to population decline and to investigate management actions for viable populations. Demographic stochasticity was considered by (a) describing reproduction on an individual basis and (b) distinguishing behavioural patterns according to age and sex. Unknown model parameters were determined by comparing field data and simulated patterns in a specific multi-criteria fashion. We conclude that disturbances such as agricultural management and highway construction are most dangerous to the common hamster in autumn. Complex land management is required which should aim at reducing habitat-specific mortality and favouring the safeguarding of adult and subadult females to protect the most sensitive component of the population. According to the model results, large habitat size is not sufficient for survival, and habitat connectivity may be even more important. Late timing of the harvest and following cultivations was most favourable for population survival.     

How well does a botanical garden collection of a rare palm capture the genetic variation in a wild population?

Conservation is increasingly central to the botanic garden mission. Living plant collections are important components of conservation. Critical evaluation of living conservation collections with population genetic analysis can directly inform ex situ conservation strategy. Here, we quantify the degree of genetic variation captured through a population-based collection protocol, and explore optimal sampling for ex situ conservation. An extensive living collection derived from one population of Leucothrinax morrisii (Arecaceae) provided a model system. We compared 58 specimens from the ex situ collection with 100 individuals from throughout the parent population via 6 ISSR loci. Random bootstrapped resamples of the data were made to model differently structured ex situ collections. Mean diversity (He) differed little between the collection (0.204) and the population (0.216), and genetic distance (D) was very close (0.036). Very few private alleles were found between the collection and the population. Allelic capture, as measured by percent of private alleles, was greater than 94%. Resampled collections of different sizes captured from 48% to 94% of alleles. Pairwise comparison of bootstrapped resamples suggests that increasing the representation of half-sibling groups does not significantly increase allele capture. Increase in allele capture with increasing sample size is greatest at low resample sizes, and showed diminishing returns as resample size increased. No appreciable increase in allele capture was gained through maintaining different half-sibling groups. These data inform sampling for ex situ conservation purposes, and recommend sample sizes of at least 15 individuals, with the upper limit based on resources.     

Are roads and railroads barriers to bumblebee movement in a temperate suburban conservation area?

We investigated how habitat fragmentation affects the movement of marked bumblebees between plant patches in a temperate conservation area in metropolitan Boston, Massachusetts. Our study was conducted on populations of sweet pepperbush (Clethra alnifolia L. f.) separated by a road and natural woodland, and buttonbush (Cephalanthus occidentalis L.) separated by a railroad. Bumblebees showed high site fidelity and only rarely crossed roads or railroads. When bees captured at one sweet pepperbush population were moved across a road to a new sweet pepperbush population and released, they returned to their original site, some within 20 min of their capture. When all inflorescences were removed from one sweet pepperbush patch, most bees moved to another sweet pepperbush population on the same side of the road. The results show that while bumblebees have the ability to cross a road and railroad, these human structures may restrict bumblebee movement and act to fragment plant populations because of the innate site fidelity displayed by foraging bees. Moreover, marked bees were almost never observed to move between populations unless they were displaced, or forced to seek additional forage sites.     

Microbial communities in forest floors under four tree species in coastal British Columbia

We compare forest floor microbial communities in pure plots of four tree species (Thuja plicata, Tsuga heterophylla, Pseudotsuga menziesii, and Picea sitchensis) replicated at three sites on Vancouver Island. Microbial communities were characterised through community level physiological profiles (CLPP), and profiling of phospholipid fatty acids (PLFA).Microbial communities from cedar forest floors had higher potential C utilisation than the other species. The F layer of the forest floor under cedar contained significantly higher bacterial biomass (PLFA) than the F layer under the other three tree species. There were differences in microbial communities among the three sites: Upper Klanawa had the highest bacterial biomass and potential C utilisation; this site also had the highest N availability in the forest floors. Forest floor H layers under hemlock and Douglas-fir contained greater biomass of Gram positive, Gram negative bacteria and actinomycetes than F layers based on PLFA, and H layers under spruce contained greater biomass of Gram negative bacteria than F layers. There were no significant differences in bacterial biomass between forest floor layers under cedar. Fungal biomass displayed opposite trends to bacteria and actinomycetes, being lowest in cedar forest floors, and highest in the F layer and at the site with lowest N availability. There were also differences in community composition among species and sites, with cedar forest floors having a much lower fungal:bacterial ratio than spruce, hemlock and Douglas-fir. The least fertile Sarita Lake site had a much greater fungal:bacterial ratio than the more fertile San Juan and Upper Klanawa sites. Forest floor layer had the greatest effect on microbial community structure and potential function, followed by site, and tree species. The similarity in trends among measures of N availability and microbial communities is further evidence that these techniques provide information on microbial communities that is relevant to N cycling processes in the forest floor.     

Inbreeding in red-cockaded woodpeckers: Effects of natal dispersal distance and territory location

Inbreeding depression constitutes a significant threat to the viability of small populations. In addition to small size and isolation of populations, short distance dispersal may elevate risk of inbreeding, but empirical evidence is scarce. Inbreeding depression has been demonstrated in the highly endangered red-cockaded woodpecker Picoides borealis. It has been suggested that conservation efforts to support extant populations should aim at spatially aggregating territories to enhance dispersal success. This however may aggravate inbreeding risk because distance between territories and hence dispersal distances become short. We analysed empirical data from a long-term study of the demography of the red-cockaded woodpecker and found that inbreeding risk varied inversely with natal dispersal distance of the mother. Using an individual-based, spatially explicit population model that incorporates simulations of environmental and demographic stochasticity and an empirically derived, species-specific estimate of inbreeding costs, we demonstrated that inbreeding depression significantly elevated extinction risk in this species. On the other hand, even though dispersal distances in populations with spatially aggregated territories were shorter and the proportion of inbred individuals was higher than in other populations of the same size, such populations were still more persistent. Despite the overall adverse effect of inbreeding depression on viability of red-cockaded woodpecker populations, lowering interterritorial distances can be viewed as a valuable conservation tool. Given the small size and isolated location of most extant red-cockaded woodpecker populations however, our findings suggest that inbreeding depression represents a significant threat to the survival of this species.     

Massive immigration balances high anthropogenic mortality in a stable eagle owl population: Lessons for conservation

The modern anthropized landscape is a major source of hazards for large animals such as raptors. Collisions with cables, vehicles and trains, as well as electrocution cause casualties, which may negatively impact populations. Yet, demographic studies of that impact remain scarce, which is an impediment to evidence-based conservation action. We studied the dynamics of an eagle owl (Bubo bubo) population in the northwestern Alps (Switzerland). We estimated, firstly, its demographic parameters using a Bayesian integrated population model; secondly, the frequency of different types of casualty through radio-tracking. Thirdly, we investigated the effects of reductions of human-related mortality on population trends. The breeding population was small but remained fairly stable during 20 years, suggesting that it was apparently in a good shape. However, survival probabilities of all age classes were very low (?0.61), productivity fairly good (0.93), and immigration very high (1.6 females per pair and year), indicating that the population operated as a sink. Half of the mortality was caused by infrastructure, with electrocution accounting for 24% of all fatalities. The elimination of electrocution would result in a strong population increase (17% annually). Under that scenario, immigration rate could decline by 60% and the population would still remain stable. Given that the supply of recruits from elsewhere is likely to continue, we can expect a rapid local population recovery if dangerous electric pylons are mitigated systematically. Our study demonstrates that detailed demographic analyses are necessary to diagnose problems occurring in populations and to identify efficient conservation actions.     

Beyond the wetland border: Estimating the impact of roads for two species of water snakes

We used models integrating road maps, traffic volume, and snake movements to examine the potential for roads to contribute to mortality in two species of water snakes that differ in their vagility, use of terrestrial habitats, and conservation status. Road networks and traffic volumes typical of three regions in Indiana, USA, may account for mortality of 14-21% of the population per year in the more vagile, terrestrial, and imperiled copperbelly water snake (Nerodia erythrogaster neglecta) but only 3-5% mortality in the more sedentary, aquatic, and common northern water snake (Nerodia sipedon). The majority (>91%) of road crossings and associated mortality are predicted to occur during overland migrations to other wetlands, suggesting roads bisecting travel routes between wetlands may function as mortality sinks. Our models highlight the proportionately greater risk of mortality for the more vagile and imperiled species, N. e. neglecta, and suggest current wetland conservation strategies that focus on the wetland alone are unlikely to adequately protect wetland biodiversity from certain types of anthropogenic habitat modification. What is needed is a landscape approach to wetland conservation that considers not only the quality of wetlands and nearby terrestrial habitats, but also ensures that terrestrial corridors between wetlands remain permeable and offer safe passage for wildlife.     

Comparative use of vendace by humans and Saimaa ringed seal in Lake Pihlajavesi, Finland

The Saimaa ringed seal, Phoca hispida saimensis, is one of the most endangered ringed seals in the world. Its total population consisted of 240 adult seals in the Saimaa lake complex in 2000. We estimated the amount of vendace, Coregonus albula, consumed by the seals and compared it with fishermen’s vendace catches and our vendace stock estimates in Lake Pihlajavesi, Finland. Our study area was the habitat of 43 mature seals and 17 immature seals as well as 12 pups in 2001. Five commercial two-boat trawlers fished in the area. Vendace stock size was estimated at 660 tonnes i.e., 12 kg ha⁻¹ in the study area in August-September 2001. The vendace catch by fishermen was approximately 250 tonnes, and the vendace consumption by the Saimaa ringed seal was estimated at 68 tonnes in 2001. We estimated that during the whole year seals ate approximately 8% of the vendace spawning stock biomass in the area while fishermen caught 30% of it. The seals and the fishermen together used less than 10% of the available vendace biomass in each month. Fishing pressure on the vendace stock was highest in August-October. The amount of vendace eaten by the seals exceeded the vendace catch in fisheries only in December-April. In periods of low vendace density, the seals can consume a higher proportion of the stock and reduce the catch per unit of effort in fisheries. However, our assumption that seals fed only on vendace should be considered as an extreme scenario when considering the conflict between fisheries and the seal.     

Population sizes, site fidelity and residence patterns of Australian snubfin and Indo-Pacific humpback dolphins: Implications for conservation

Very little is known about the ecology of snubfin Orcaella heinsohni and Indo-Pacific humpback dolphins Sousa chinensis in Australian waters. We used photo-identification data collected between 1999 and 2002 in Cleveland Bay, northeast Queensland, to estimate abundance, site fidelity and residence patterns of these species in order to make recommendations for their effective conservation and management. Our abundance estimates indicate that less than a hundred individuals of each species inhabit this coastal area. Even with relatively unbiased and precise abundance estimates population trends will be extremely difficult to detect in less than three years unless changes in population size are very high (>20% p.a.). Though both species are not permanent residents in Cleveland Bay, they both used the area regularly from year to year following a model of emigration and reimmigration. Individuals of both species spend periods of days to a month or more in coastal waters of Cleveland Bay before leaving, and periods of over a month outside the study area before entering the bay again. Because of their small population sizes and movement patterns, snubfin and humpback dolphins are particularly vulnerable to local extinction. Our results illustrate that: (1) detection of population trends should not be a necessary criterion for enacting conservation measures of both species in this region, and (2) efforts to maintain viable populations of both species in Cleveland Bay must include management strategies that integrate anthropogenic activities in surrounding areas.     

The effects of land use and climate on red kite distribution in the Iberian peninsula

The main breeding populations of the red kite (Milvus milvus L.), have been declining in the Iberian peninsula during the last decade. However, there is a lack of regional assessments of habitat suitability that identifies limiting ecological factors for the species and areas with conservation problems. In this work we present a regional model for the distribution and abundance of breeding red kites in the Iberian peninsula. The occurrence and estimated abundance in 100 km² UTM squares resulting from road censuses were modelled with broad-scale explanatory variables obtained from satellite imagery, thematic digital cartography, climatic data and spatial coordinates. The occurrence model incorporated mainly climatic variables and had a good discrimination ability, while the abundance model incorporated mainly land-use variables and had a lower explanatory power (r²=0.14). The predictions somewhat overestimated the results of the censuses, and this agrees with the decline of population size and range observed for this species in the Iberian peninsula. These models are relevant in the conservation of the species: first, they suggest the limiting factors for red kite in the Iberian peninsula, and, second, they generate predictive maps pointing out both areas in which conservation problems may be acute (suitable locations that are unoccupied), and areas where no data is available but the red kite is likely to be present (thus guiding further survey and research).     

Do meadow birds profit from agri-environment schemes in Dutch agricultural landscapes?

Since 1992 the European Union helps member states to reverse the loss of biodiversity in agricultural landscapes by the financial support of agri-environment schemes. Long-term studies investigating the effects of these schemes are an essential prerequisite for the development of an effective policy to restore biodiversity on farmland. In Dutch meadow landscapes almost all agri-environment schemes focus on the restoration of meadow bird populations by postponement of the mowing date. Between 1990 and 2002 we measured long-term changes in meadow bird densities in areas with and without agri-environment schemes in the Netherlands, both before and after the start of the contract. During these years bird territories were surveyed during five field visits between 15 March and 15 June. Densities of black-tailed godwit (Limosa limosa), and redshank (Tringa totanus) were higher in the areas with management agreements, but these differences were already present before the start of the contracts. After the start of the management contracts densities of black-tailed godwit and oystercatcher (Haematopus ostralegus) did not increase, while those of lapwing (Vanellus vanellus) and redshank even declined relative to the control areas. It is concluded that the current agri-environment schemes are not sufficient to restore meadow bird populations in Dutch agricultural landscapes. In addition to the prescribed postponement of the mowing date, it is probably necessary to raise groundwater levels and to reduce fertilization to allow for the development of an open vegetation structure that will increase chick survival to sufficiently high levels.     

Status and conservation of the grey seal, Halichœrus grypus, in France

We investigated the status of the grey seal in the Molène archipelago, western Brittany, where a Marine National Park is planned. We combined regular censuses, photo-identification and satellite telemetry to investigate trends in grey seal abundance, site fidelity, individual movements and haulout site use. Individual movements and seasonal variations in abundance suggest that the seals used the Molène archipelago alternatively with other haulout sites of the South-west British Isles during their annual cycle. Nine out of 16 seals fitted with Satellite Relay Data Loggers (SRDLs) moved to the Isles of Scilly, English Cornwall, Wales or the Channel islands. On average the seals spent 85% of their time Near Haulout, 56.8% of which in the Molène archipelago. Overall the seals spent 66% of their tracking time within the boundaries of the Marine National Park. From 1997 to 2000 in the Molène archipelago, we observed a peak in number during the moulting season (mean = 49.8 seals) and a lower abundance during the breeding season (mean = 38.3 seals). The sex ratio was strongly skewed towards males during the moult (between 3.1 and 5.3-1), and was close to 1:1 during the summer. Inter-annual site fidelity outside the breeding season was very high, varying from 70% to 95% of identified seals, suggesting that the observed movements constitute rotations rather than random dispersion. From 1991/1994 to 1997/2000, the mean number of seals counted at haulout sites increased by 7%, close to the rates of increase observed in the core population of the British Isles at the same period. The Marine National Park may be too restricted for the overall conservation of the population but management plans should be aimed at preserving the characteristics of the habitat for the grey seal.