The metabolism of organochlorine compound by microsomal enzymes of the shag (Phalacrocorax aristotelis).

1. The activities of microsomal enzymes of adult male shags (Phalacrocorax aristotelis) towards the organochlorine substrates HHDN, HCE and Heom were compred with those of microsomal enzymes of the adult male Wistar rat. 2. Liver homogenates showed similar epoxide hydrase activity to kidney homogenates in the shag, but in the rat liver preparations was much more active than the kidney preparation. 3. Liver microsomes of the shag showed smaller than 8% of the epoxide hydrase activity and smaller than 14% of the hydroxylating capacity of liver microsomes from the rat. 4. The relatively low activity of these enzymes is probably the main reason why the shag has been found to contain relatively high levels of dieldrin in ecological studies.     

Extra-pair paternity in the shag, Phalacrocorax aristotelis as determined by DNA fingerprinting

The frequency of chicks resulting from extra-pair copulation in the shag, Phalacrocorax aristotelis , was measured by DNA fingerprinting. DNA fingerprints were taken from both sexes of 15 pairs and their chicks (28) in a subcolony on the Isle of May, UK. It was found that 18% of the chicks had extra-pair paternity, and one chick (3.5%) was not the offspring of either member of the pair, implying either a polygynous male whose second female was fertilized by another male or adoption. Although no observations of courtship and copulation were made in the same season, observations in a previous year on the same colony of shags showed that 14.1% of the copulations by males were not with the female with whom that male reared young. The similarities and differences are discussed between these results on the level of extra-pair copulations and of extra-pair paternity and those of other studies where both observations of extra-pair copulations and various measures of the degree of extra-pair paternity have been made.     

On a new species of tetrabothriid cestode from the shag Phalacrocorax aristotelis aristotelis (L.)

A new species of tetrabothriid tapeworm parasitic in the gut of the shag is recorded and described.     

Sexual ornament size and breeding performance in female and male European Shags Phalacrocorax aristotelis

Research into sexual selection and animal ornamentation has been largely directed at males in sexually dimorphic species. In contrast, there is relatively little empirical information on female ornamentation. Using the European Shag Phalacrocorax aristotelis , a species in which both sexes have an ornamental crest during pair formation, we investigated the evidence for (1) a correlation between crest size and breeding performance and (2) assortative pairing on crest size. Crest size appeared unrelated to age in either sex, though our sample of males did not include first-time breeders. The year of study was one in which overall breeding performance at the colony was poor. Females that did not subsequently produce a clutch had significantly smaller crests during the courtship period than those that did, suggesting a link between ornament size and current condition. This relationship was also significant in males. Among those birds that did produce eggs, there was a significant relationship between ornament size and laying date, again significant in both sexes, with early breeders having larger crests. Early breeding is generally associated with relatively high breeding performance in European Shags. Given that both males and females contribute substantially to parental care and that there will be intrasexual differences in quality, choosiness is likely to be favoured in both sexes, and individuals were found to be paired assortatively with respect to crest size. Our results suggest that ornament size is related to state in European Shags, and thus may be involved in mate choice in both sexes.     

Genetic structure in the European endemic seabird,Phalacrocorax aristotelis,shaped by a complex interaction of historical and contemporary,physical and nonphysical drivers

Geographically separated populations tend to be less connected by gene flow, as a result of physical or nonphysical barriers preventing dispersal, and this can lead to genetic structure. In this context, highly mobile organisms such as seabirds are interesting because the small effect of physical barriers means nonphysical ones may be relatively more important. Here, we use microsatellite and mitochondrial data to explore the genetic structure and phylogeography of Atlantic and Mediterranean populations of a European endemic seabird, the European shag, Phalacrocorax aristotelis, and identify the primary drivers of their diversification. Analyses of mitochondrial markers revealed three phylogenetic lineages grouping the North Atlantic, Spanish/Corsican and eastern Mediterranean populations, apparently arising from fragmentation during the Pleistocene followed by range expansion. These traces of historical fragmentation were also evident in the genetic structure estimated by microsatellite markers, despite significant contemporary gene flow among adjacent populations. Stronger genetic structure, probably promoted by landscape, philopatry and local adaptation, was found among distant populations and those separated by physical and ecological barriers. This study highlights the enduring effect of Pleistocene climatic changes on shag populations, especially within the Mediterranean Basin, and suggests a role for cryptic northern refugia, as well as known southern refugia, on the genetic structure of European seabirds. Finally, it outlines how contemporary ecological barriers and behavioural traits may maintain population divergence, despite long‐distance dispersal triggered by extreme environmental conditions (e.g. population crashes).     

From cradle to early grave: juvenile mortality in European shags Phalacrocorax aristotelis results from inadequate development of foraging proficiency

In most long-lived animal species, juveniles survive less well than adults. A potential mechanism is inferior foraging skills but longitudinal studies that follow the development of juvenile foraging are needed to test this. We used miniaturized activity loggers to record daily foraging times of juvenile and adult European shags Phalacrocorax aristotelis from fledging to the following spring. Juveniles became independent from their parents 40 days post-fledging. They compensated for poor foraging proficiency by foraging for approximately 3 h d(-1) longer than adults until constrained by day length in early November. Thereafter, juvenile foraging time tracked shortening day length up to the winter solstice, when foraging time of the two age classes converged and continued to track day length until early February. Few individuals died until midwinter and mortality peaked in January-February, with juvenile mortality (including some of the study birds) five times that of adults. In their last two weeks of life, juveniles showed a marked decline in foraging time consistent with individuals becoming moribund. Our results provide compelling evidence that juveniles compensate for poor foraging proficiency by increasing foraging time, a strategy that is limited by day length resulting in high winter mortality.     

Scale-dependent climate signals drive breeding phenology of three seabird species

Breeding at the right time is essential for animals in seasonal climates in order to ensure that the energy demands of reproduction, particularly the nutritional requirements of growing young, coincide with peak food availability. Global climate change is likely to cause shifts in the timing of peak food availability, and in order to adapt successfully to current and future climate change, animals need to be able to adjust the time at which they initiate breeding. Many animals use environmental cues available before the breeding season to predict the seasonal peak in food availability and adjust their phenology accordingly. We tested the hypothesis that regulation of breeding onset should reflect the scale at which organisms perceive their environment by comparing phenology of three seabird species at a North Sea colony. As predicted, the phenology of two dispersive species, black-legged kittiwake ( Rissa tridactyla ) and common guillemot ( Uria aalge ), correlated with a large-scale environmental cue (the North Atlantic Oscillation), whereas a resident species, European shag ( Phalacrocorax aristotelis ), was more affected by local conditions (sea surface temperature) around the colony. Annual mean breeding success was lower in late years for European shags, but not for the other two species. Since correlations among climate patterns at different scales are likely to change in the future, these findings have important implications for how migratory animals can respond to future climate change.     

Influence of body composition on the metabolic rate of nestling European shags (Phalacrocorax aristotelis)

During the early development of avian nestlings, their mass-specific resting metabolic rate (RMR) changes in a biphasic pattern with the peak value often being much higher than that expected for an adult bird of similar body mass. In the present study we examined the possible influence of variations in the size of internal organs in “setting” the high RMR and peak metabolic rate (PMR) during development in a large altricial species, the European shag (Phalacrocorax aristotelis). Thermoneutral RMR and cold-exposure induced PMR were measured in nestlings 15 days old, the age at which the highest RMR occurred during development. Body mass averaged 414 g. Mean values of RMR and PMR were 5.75 W and 9.08 W, respectively; the RMR value corresponds to approximately 250% of the expected value for an adult non-passerine bird of similar body mass. The masses of all the organs measured (breast and leg muscles, heart, liver, intestine, and kidney) varied isometrically with total body mass. However, large chicks had a significantly lower fractional water content than small chicks, suggesting that the former had achieved a higher level of functional maturity. In contrast to what has been suggested for adult birds in general, the heart and kidney masses of shag nestlings were not significantly correlated with the metabolic rates. The intestine length, in contrast, was highly and positively correlated with both the RMR and the PMR, i.e. intestine length was a better predictor of RMR and PMR than was total body mass. In addition, liver mass was positively correlated with RMR. The results of the present study suggest that the liver in particular may play a key role in establishing the high, mass-specific RMR which is attained during development in bird chicks. Our results also support previous suggestions that early in their development, altricial chicks mainly allocate energy to the growth of `energy-processing' organs (such as the intestine and liver) rather than to `energy-consuming' organs. Accepted: 3 March 1999     

The demographic impact of extreme events: stochastic weather drives survival and population dynamics in a long-lived seabird

1. Most scenarios for future climate change predict increased variability and thus increased frequency of extreme weather events. To predict impacts of climate change on wild populations, we need to understand whether this translates into increased variability in demographic parameters, which would lead to reduced population growth rates even without a change in mean parameter values. This requires robust estimates of temporal process variance, for example in survival, and identification of weather covariates linked to interannual variability. 2. The European shag Phalacrocorax aristotelis (L.) shows unusually large variability in population size, and large-scale mortality events have been linked to winter gales. We estimated first-year, second-year and adult survival based on 43 years of ringing and dead recovery data from the Isle of May, Scotland, using recent methods to quantify temporal process variance and identify aspects of winter weather linked to survival. 3. Survival was highly variable for all age groups, and for second-year and adult birds process variance declined strongly when the most extreme year was excluded. Survival in these age groups was low in winters with strong onshore winds and high rainfall. Variation in first-year survival was not related to winter weather, and process variance, although high, was less affected by extreme years. A stochastic population model showed that increasing process variance in survival would lead to reduced population growth rate and increasing probability of extinction. 4. As in other cormorants, shag plumage is only partially waterproof, presumably an adaptation to highly efficient underwater foraging. We speculate that this adaptation may make individuals vulnerable to rough winter weather, leading to boom-and-bust dynamics, where rapid population growth under favourable conditions allows recovery from periodic large-scale weather-related mortality. 5. Given that extreme weather events are predicted to become more frequent, species such as shags that are vulnerable to such events are likely to exhibit stronger reductions in population growth than would be expected from changes in mean climate. Vulnerability to extreme events thus needs to be accounted for when predicting the ecological impacts of climate change.     

Diving depths of Shags Phalacrocorax aristotelis breeding on the Isle of May

Information on maximum dive depth and the time spent at various depths was obtained from 49 Shags Phalacrocorax aristotelis. On average, the maximum dive depth was 33–35 m; the overall maximum was 43 m. Shags dived repeatedly to the same depth and spent c. 55% of the time between 25 and 34 m which indicated that they were foraging close to the seabed. About 46% of the time underwater was spent foraging and 54% travelling. Average underwater swimming speed was 1.7-1.9 m per second.     

Foraging range and feeding locations of Shags Phalacrocorax aristotelis during chick rearing

We used radio-tracking techniques to determine the foraging range and feeding locations used by individual Shags Phalacrocorax aristotelis during chick rearing on the Isle of May, Scotland. The mean (±s.d.) foraging range was 7.o±1.9 km (maximum 17 km) and there were no significant sex or year differences. All feeding sites were within 7 km of land. Most (> 90%) were either within 2 km of the colony or in two discrete areas 5–13 km to the north and west. Use of the areas varied between years with both males and females making more use of the north area in 1987 than either 1988 or 1989. Birds used > 11% of the area of sea within the maximum recorded feeding range. This restricted distribution appeared to be related to water-depth and bottom sediment type. Shags fed most frequently in water 21–40 m deep, with a bottom of either gravel and sand, or rock with thin patchy sediment cover.     

Factors influencing food-load sizes brought in by Shags Phalacrocorax aristotelis during chick rearing

Weights of food loads brought back to the colony by 26 Shags Phalacrocorax aristotelis rearing chicks were determined using the water-offloading procedure. Loads consisted almost entirely of lesser sandeels Ammodytes marinus. Load size was extremely variable, ranging from 8 to 208 g with a mean load weight of 106 g. Data on foraging behaviour collected concurrently demonstrated that Shags brought back heavier loads when they were feeding farther away from the colony and when brood biomass was larger. These two variables together explained 70.3% of the variation in load size. We postulate that adults had already digested their own food requirements by the time they arrived back at the nest, and the contents of the loads were therefore primarily for the young. On 67% of trips, Shags caught, on average, more than one fish per dive. This estimate ignores the food requirements of the adult, and therefore true prey-capture rates must have been higher.     

Larval anisakid infections of some tropical fish species from north-west Australia

Despite the commercial and zoonotic importance of larval anisakid infestations of teleosts, their distribution among Australia's diverse marine fish fauna is poorly understood. A preliminary survey of Australia's tropical north-west revealed a generally high prevalence of larval anisakids representing four genera (Anisakis, Terranova, Thynnascaris and Raphidascaris) among only seven fish species. The potential impact of high larval anisakid infections on both the health of recreational fishermen and aquaculture environments is discussed.     

Age-related effects of a nonbreeding event and a winter wreck on the survival of Shags Phalacrocorax aristotelis

During 1993, about half the adult Shags Phalacrocorax aristotelis alive on the Isle of May, southeastern Scotland, failed to breed. The proportion not breeding was highest (66%) for individuals aged 14–21 years and lowest (12%) for those aged 3–6 years. In February 1994, a prolonged spell of onshore winds resulted in a wreck of these adults such that overwinter survival was reduced from the normal 88% to 14.7%. The age-specific pattern of survival over this winter differed from previous years, with birds aged less than 7 years and more than 16 years surviving less well and middle-aged individuals surviving better than expected. Whether an individual had bred or not in 1993 had little effect on the chances of survival of the youngest and oldest individuals, as most died. However, among Shags aged 12–15 years, those which had bred survived markedly less well than those which had not, indicating that there had been some cost involved to birds in breeding in 1993.     

Philopatry and colony fidelity of Shags Phalacrocorax aristotelis on the east coast of Britain

Shag Phalacrocorax aristotelis colonies from the Firth of Forth south to the Fame Islands (SE Scotland and NE England) were surveyed in 1982 and 1983 for nesting Shags ringed as chicks or adults in the previous 20 years. On average, 5% of 863 Shags ringed as chicks were breeding away from their natal colony, and only 1% of 401 marked adults had left their breeding colony. The proportion p of chicks that settled at or beyond distance D from the natal colony followed the relationship p = 0.263D-^0.771, implying that more Shags moved 10 km or beyond to breed than expected from diffusion models or a constant-rate dispersal model; adjusted for birds that settled outside the study area, the relationship was p = 0.314D^-0771. There was no effect of colony size on emigration rate, but females showed a greater tendency to settle away from the natal colony than did males. At the natal colony, more males (69%) than females (47%) nested within 300 m of their birthplace. Two mechanisms appear to determine where a Shag settles to breed: a navigational one governing the return to the natal colony, plus the competitive process of nest-site establishment.     

Does food shortage delay development of homeothermy in European shag nestlings (<Emphasis Type="Italic">Phalacrocorax aristotelis</Emphasis>)?

Nestlings seem to face a trade-off between reducing the basal level of energy metabolism, as an energy-saving response, and maintaining thermogenic capacity during temporal food shortage. In the present study we examined developmental responses to short-term diet restriction of 12–16 day old nestling European shags kept under laboratory conditions and tested whether temporal food shortage delay the development of homeothermy. During food shortage the European shag nestlings substantially reduced basal level of energy metabolism, resulting in significant energy savings. The reduction in basal level of energy metabolism corresponded with a reduction in peak metabolic rate. At the same time, the low peak metabolic rate of diet-restricted nestlings was offset by a lower mass-specific minimal thermal conductance, and an increased mass-specific absolute scope. Consequently, the insulation and the portion of peak metabolic rate available for regulatory thermogenesis seemed to develop normally, as expected from age, during the period of food shortage. Further, the degree of homeothermy, measured as the index of homeothermy, was not significantly lower in diet-restricted nestlings compared to controls at the same age. We conclude that temporal food shortage did not significantly delay the development of homeothermy in the European shag nestlings despite substantial reductions in basal level of energy metabolism and peak metabolic rate.Communicated by: G. Heldmaier     

Four cases of gastric submucosal mass suspected as anisakiasis

Anisakiasis is a parasitic disease caused by ingestion of raw fish infected with anisakid larvae. Endoscopic changing patterns of submucosal lesions in chronic gastric anisakiasis have not been known yet. Here we report 4 cases of suspected gastric anisakiasis which were improved during follow-up periods without surgical treatment. The patients presented with abdominal pain, nausea and vomiting after consuming raw marine fish, and visited our gastroenterology outpatient department. Their endoscopic findings showed firm and yellowish submucosal masses accompanied with eccentric erosions. Histologic findings showed severe eosinophilic infiltrations. In blood tests, peripheral eosinophil counts and total IgE levels were elevated. We believed that all cases were caused by larval anisakid infections. The submucosal mass lesions disappeared during the follow-up periods of 2 to 4 mo.     

The chromosomes of a catfishParasilurus aristotelis from Greece

The karyotype of the catfish,Parasilurus aristotelis, from Lake Trichonis, Greece, shows that the species has a diploid chromosome number of 2n = 58. Comparison with published data on the karyotypes of other species belonging toParasilurus shows the same chromosome number but different arm numbers. Reported karyological data of the European populations ofSilurus indicate that they have a diploid number of 2n=60. A reduction in chromosome number is assumed to be connected with speciation and, therefore,Parasilurus probably forms a separate group from that ofSilurus.     

Immediate and delayed effects of a gale in late spring on the breeding of the Shag Phalacrocorax aristotelis

At the beginning of May 1982, a westerly gale destroyed or damaged 49% of 761 Shag Phalacrocorax aristotelis nests on the exposed west side of the Isle of May, southeast Scotland; 518 nests on the sheltered east side acted as controls against which to assess subsequent effects of the gale on Shag reproduction and recruitment.
On sites affected by the gale, 90% of pairs rebuilt their nest and laid a second clutch, on average 18 days after the loss of the first one. First-time breeders nested closer to the sea, suffered greater damage to their nests, and deserted their damaged nests more readily after the gale than did experienced ones; a quarter of potential recruits to the west side were deterred from breeding in that year.
By the end of the season, the number of chicks fledged per pair was 31% lower on the west side than on the east. The difference was caused partly by nest desertion, partly by greater hatching failure of full clutches in apparently undamaged nests and especially by lower fledging success of pairs that renested. Irrespective of breeding experience, delayed early breeders produced more chicks than late breeders nesting at the same time, showing that late breeders were of poorer intrinsic quality than early breeders. This was one reason for a seasonal decline in Shag productivity, although environmental factors also played a role.
During April-July, gales like that of May 1982 occur on average once every 5 years on the Isle of May. Despite the disruption that they may cause to nesting Shags, the impact on the long-term growth of the colony is small.     

Larval anisakids parasitizing the blue whiting, Micromesistius poutassou, from Motril Bay in the Mediterranean region of southern Spain

A total of 301 blue whiting, Micromesistius poutassou Risso, 1826, ranging in length from 17 to 28 cm, from Motril Bay (Mediterranean coast, south Spain) were examined for anisakid nematodes, as these fish are common items in the Spanish Mediterranean diet. Three anisakid species were morphologically identified with a total prevalence of 10.63%. Anisakis simplex s.l. Rudolphi, 1809 had a prevalence value of 6.65%, compared with 2.66% for A. physeteris Baylis, 1923 and 2.33% for Hysterothylacium aduncum Rudolphi, 1802. Variations in prevalence values with season and host size are discussed. Allozyme markers (leucine aminopeptidase-1) were used to identify anisakid nematodes assigned to the A. simplex complex and all examined larvae were found to correspond genetically to A. pegreffii Nascetti et al., 1986.