Seabirds as monitor organisms of contaminants along the German North Sea coast

In the 1980s, significant regional, interspecific and annual differences in contamination with toxic chemicals were found in eggs of breeding birds along the German North Sea coast. In some regions residue levels approached a range endangering breeding success, especially in terns. In 1987, a three-year monitoring-program for common ternSterna hirundo and oystercatcherHaematopus ostralegus was started, in order to recognize such contamination trends. Eggs from 9–14 areas along the coast are now being analysed for chlororganic residues and mercury. First results on geographical and year-to-year variation are presented here, and the advantages of seabird eggs as spatial and temporal monitors of marine pollution are discussed. The suggestion is made to include a shore-breeding bird species in the European monitoring programs. Presented at the VI International Wadden Sea Symposium (Biologische Anstalt Helgoland, Wattenmeerstation Sylt, D-2282 List, FRG, 1–4 November 1988)     

Trends of harbour porpoise (Phocoena phocoena) density in the southern North Sea

In the southern North Sea, harbour porpoise occurrence increased in recent years after a phase of low abundances during earlier decades. Only very few studies on porpoise presence in the southern German North Sea exist so far. As anthropogenic activities will strongly increase in this part of the North Sea during the next years it is most important to assess population level effects. This study focuses on the analysis of temporal and spatial trends in porpoise density in this area of recent change. Dedicated aerial line-transect distance sampling surveys were conducted in the southern German North Sea between May 2002 and June 2013 to assess porpoise density and distribution. Statistical inferences on porpoise population trends were made using a Markov Chain Monte Carlo (MCMC) technique. Two approaches were chosen to test for a trend in porpoise density and an additional model focused on the change in density of calves. During 55,820 km of survey effort 4377 porpoises including 140 calves were recorded. A significant effect of increasing spatial aggregation from the lower density areas in the south-eastern German Bight to hot spot areas in the western parts was detected. For the western part of the study area a significant increase in porpoise density between 2002 and 2013 was detected. Seasons were significantly different with highest porpoise density in spring and successively decreasing densities in summer and autumn. From 2008 onwards high densities were also observed in summer. Calf density increased during the study period and was significantly higher in the west. On the basis of this extensive and unique data set on porpoise occurrence in the southern German North Sea the findings clearly show that especially the south-western German North Sea serves as habitat of increasing importance for porpoises throughout the last decade. Definite reasons still remain unresolved. Changes in prey abundance or less favourable conditions in other areas could be important factors, which may also have caused a southward shift from high density areas in northern waters. On this baseline, further integrative approaches might lead to a sound understanding of the effect of anthropogenic activities on the future development of porpoise populations.     

Migration of Pacific Rim Chum Salmon on the High Seas: Insights from Genetic Data

Wild stocks of chum salmon, Oncorhynchus keta, have experienced recent declines in some areas of their range. Also, the release of hatchery chum salmon has escalated to nearly three billion fish annually. The decline of wild stocks and the unknown effects of hatchery fish combined with the uncertainty of future production caused by global climate change have renewed interest in the migratory patterns of chum salmon on the high seas. We studied the composition of high-seas mixtures of maturing and immature individuals using baseline data for 20 allozyme loci from 356 populations from throughout the Pacific Rim. Composition estimates were made from three time series. Two of these time series were from important coastal migratory corridors: the Shumagin Islands south of the Alaska Peninsula and the east coast of the Kamchatka Peninsula. The third was from chum salmon captured incidentally in the Bering Sea trawl fishery for walleye pollock. We also analyzed geographically dispersed collections of chum salmon captured in the month of July. The time series show dynamic changes in stock composition. The Shumagin Island corridor was used primarily by Northwest Alaskan and Asian populations in June; by the end of July stocks from the Alaska Peninsula and southern North America dominated the composition. The composition along the Kamchatka coast changed dramatically from primarily Russian stocks in May to primarily Japanese stocks in August; the previously undocumented presence of stocks from the Alaska Peninsula and Gulf of Alaska was also demonstrated. Immature chum salmon from throughout the Pacific Rim, including large proportions of southern North American stocks, contributed to the Bering Sea bycatch during the months of September and October. The migration routes of North American stocks is far more widespread than previously observed, and the Bering Sea is an important rearing area for maturing and immature chum salmon from throughout the species' range.     

Phylogeography and ecological niche modelling of the New Zealand stick insect Clitarchus hookeri (White) support survival in multiple coastal refugia

Aim Increasing our understanding of the effects of the Last Glacial Maximum (LGM) and determining the location of refugia requires studies on widely distributed species with dense sampling of populations. We have reconstructed the biogeographic history of Clitarchus hookeri (White), a widespread species of New Zealand stick insect that exhibits geographic parthenogenesis, using phylogeographic analysis and ecological niche modelling. Location New Zealand. Methods We used DNA sequence data from the mitochondrial cytochrome c oxidase subunit I gene to reconstruct phylogenetic relationships among haplotypes from C. hookeri and two undescribed Clitarchus species. We also used distribution data from our own field surveys and museum records to reconstruct the geographic distribution of C. hookeri during the present and the LGM, using ecological niche modelling. Results The ecological niche models showed that the geographic distribution of C. hookeri has expanded dramatically since the LGM. Our model predicted large areas of suitable LGM habitat in upper North Island, and small patches along the east coast of South Island. The phylogeographic analysis shows that populations in the northern half of North Island contain much higher levels of genetic variation than those from southern North Island and South Island, and is congruent with the ecological niche model. The distribution of bisexual populations is also non-random, with males completely absent from South Island and very rare in southern North Island. Main conclusions During the LGM C. hookeri was most likely restricted to several refugia in upper North Island and one or more smaller refugia along the east coast of South Island. The unisexual populations predominate in post-glacial landscapes and are clearly favoured in the recolonization of such areas. Our study exemplifies the utility of integrating ecological niche modelling and phylogeographic analysis.     

Confirmation of a wintering ground of Ross's Gull Rhodostethia rosea in the northern Labrador Sea

Ross's Gull Rhodostethia rosea is one of the world's least known seabirds; < 1% of the estimated global population can be accounted for at known breeding sites, and its wintering range has never been determined. Anecdotal reports over the last two centuries have prompted extensive speculation as to possible wintering areas used by this species in the north Pacific/Bering Sea region, but none has ever been confirmed. Using satellite and geolocator telemetry, we show that some Ross's Gulls from a colony in the Canadian Arctic winter in a restricted area of the northern Labrador Sea. Our discovery of a wintering area in the northwest Atlantic indicates that Ross's Gulls breeding in the Nearctic may be part of a disjunct population, or that birds breeding in the Palaearctic may winter off the east coast of North America.     

Long-term population dynamics of breeding bird species in the German Wadden Sea area

For no other group of organisms in coastal areas are there so exact and long-term data available as there are for seabirds. Since the beginning of the 20th century, documentation of population size, especially for species breeding in colonies from the groups gulls, terns and auks, is almost complete. These species act as bio-indicators, and data on fluctuations in their population size are useful as they reflect changes in the state of the marine ecosystem. The population development of some of these seabird species (Herring Gull, Guillemot, Common, Arctic and Sandwich Tern) from the German North Sea coast, which primarily feed on fish, is given. Common to all these species is an exponential increase in numbers in recent years (1970–1985). Possible causes for this development, e.g. pressure from enemies or competitors, availability of breeding places, anthropogenic stress and mortality factors, as well as the direct and indirect anthropogenic-influenced changes in the trophic system due to the increasing eutrophication of coastal waters, are evaluated. Signs of a collapse in the stocks of seabrids resulting from environmental pollution are discussed. Consequences resulting from the ecosystem changes, such as reduction of nutrient discharge into the North Sea and the expansion of biological monitoring, are described. Presented at the VI International Wadden Sea Symposium (Biologische Anstalt Helgoland, Wattenmeerstation Sylt, D-2282 List, FRG, 1–4 November 1988)     

Phylogeographic evidence for the postglacial colonization of the North and Baltic Sea coasts from inland glacial refugia by Triglochin maritima L.

We investigated the geographical distribution of genetic variation in 67 individuals of Triglochin maritima from 38 localities across Europe using AFLP markers. Analysis of genetic variation resulted in the recognition of two major genetic groups. Apart from few geographical outliers, these are distributed (1) along the Atlantic coasts of Portugal, Spain and France and (2) in the North Sea area, the Baltic Sea area, at central European inland localities, the northern Adriatic Sea coast and the Mediterranean coast of southwest France. Considering possible range shifts of T. maritima in reaction to Quaternary climatic changes as deduced from the present-day northern temperature limit of the species, Quaternary changes of coastline in the North Sea area and the very recent origin of the Baltic Sea, we conclude that the coastal populations of T. maritima in the North Sea and Baltic Sea areas originated from inland populations.     

Review on the effects of pollution on marine fish life and fisheries in the North Sea

Information on possible effects of pollution on fish life is reviewed with special emphasis to the North Sea. Concentrations of heavy metals are high in onshore waters, sediments and organisms. Offshore regions are considered to be not endangered. In estuaries concentrations of certain heavy metals are often surpassing thresholds, which have been experimentally demonstrated to produce sublethal effects on marine organisms. Also mussel culture areas had to be closed due to excess of cadmium contamination. Mercury in fillets of cod in the southern North Sea sometimes reaches 0.3 ppm representing 1/3 of the legal limit. Reductions of inputs are necessary due to the bioaccumulative and toxic potential of heavy metals. Organochlorine contamination of water, sediments and organisms is higher in the southern than in the northern North Sea. In offshore areas clearly elevated levels of PCB's, which are the dominating organochlorine compound in marine organisms, have been analyzed. At present only a minor fraction of total organochlorine residues accumulated in marine biota is analyzed. Margins between experimentally derived lethal levels and those occurring in marine biota are narrow suggesting that sublethal effects might occur. One of the special concerns in the context of organochlorine contamination has to be seen in the potential of these substances affecting the reproductive capacity of marine organisms. Reduction measures are urgently necessary and should include substances with bioaccumulative and toxicological potential, which are not presently included in Marine Monitoring Programmes. Impact of oil pollution is considered to be a regional problem, although especially in estuaries concentrations in the water column might be high. Input through oil platforms has led to local reductions in benthic communities. Measures have to be taken, to further reduce these inputs also in view to avoid contamination of fish in the vicinity of oil fields. Oxygen depletion in German and Danish coastal waters has been shown to be a severe degradation in coastal water quality resulting in significant impact on fish populations. Indications for large-scale avoidance reactions of low DO-areas and mortalities of fish and benthos organisms have been demonstrated. It is suspected that the low DO-situations are related to increased nutrients input and high phytoplankton production. Improvement of the situation can only be expected, if input of nutrients is reduced. Reasons for the occurrence of toxic plankton blooms are not understood. An intensified research is necessary, to avoid damage to fisheries and mariculture. Although activity of radionucleids in North Sea waters is increased due to input of radioactive material from La Hague and Sellafield reprocessing units, the present levels of activity are not considered to be a threat for marine life. The same holds for thermal pollution, which is, depending on the recipient area, expected to have only local effects. Sewage sludge dumping and discharge of untreated sewage introduce significant amounts of accompanying heavy metals, which can be expected to have a negative influence on the total metal budget of recipient waters. Nutrient input through sewage will exhibit only local effects. Dumping of wastes from titanium dioxide industry are suspected to be causally linked to the occurrence of increased prevalences of certain diseases of dab in the German Bight. Present management strategies should take account of the fact that through dumping of waste from titanium dioxide production significant quantities of heavy metal are introduced into the southern North Sea. Also the incineration of chemical wastes at sea should be reduced due to uncertainties concerning quantities and toxicity of incineration products and their potential impact on marine life. It is concluded that clear evidence exists for pollution impact in estuarine regions. Most of the major estuaries at the North Sea coast show benthos reductions, which can be related to water quality and it has to be assumed that areas of a sublethal effect are located in the vicinity of those areas of well demonstrated effects. They are of unknown size and attempts have to be undertaken to quantify areas of sublethal impact. The occurrence of fish diseases is interpreted as an expression of degraded water quality. Some of the diseases detected can produce mortality, thereby having an as yet unquantified impact on fish populations. The presence of fish diseases also reduces the marketability of catches. It cannot be excluded that changes in species composition of fish populations in German Wadden Sea areas are related to pollution. Concentrations of organochlorine substances in fishes of the southern North Sea give rise to the concern that their reproductive capability might be impaired. Future work has to be directed to this problem. Impact of pollution on populations of marine organisms has so far not been demonstrated.     

Varying foraging patterns in response to competition? A multicolony approach in a generalist seabird

Reducing resource competition is a crucial requirement for colonial seabirds to ensure adequate self‐ and chick‐provisioning during breeding season. Spatial segregation is a common avoidance strategy among and within species from neighboring breeding colonies. We determined whether the foraging behaviors of incubating lesser black‐backed gulls (Larus fuscus) differed between six colonies varying in size and distance to mainland, and whether any differences could be related to the foraging habitats visited. Seventy‐nine incubating individuals from six study colonies along the German North Sea coast were equipped with GPS data loggers in multiple years. Dietary information was gained by sampling food pellets, and blood samples were taken for stable isotope analyses. Foraging patterns clearly differed among and within colonies. Foraging range increased with increasing colony size and decreased with increasing colony distance from the mainland, although the latter might be due to the inclusion of the only offshore colony. Gulls from larger colonies with consequently greater density‐dependent competition were more likely to forage at land instead of at sea. The diets of the gulls from the colonies furthest from each other differed, while the diets from the other colonies overlapped with each other. The spatial segregation and dietary similarities suggest that lesser black‐backed gulls foraged at different sites and utilized two main habitat types, although these were similar across foraging areas for all colonies except the single offshore island. The avoidance of intraspecific competition results in colony‐specific foraging patterns, potentially causing more intensive utilization of terrestrial foraging sites, which may offer more predictable and easily available foraging compared with the marine environment.     

Spatial patterns in age- and colony-specific survival in a long-lived seabird across 14 contrasting colonies

Demographic rates such as recruitment and survival probability can vary considerably among populations of the same species due to variation in underlying environmental processes. If environmental processes are spatially correlated, nearby populations are expected to have more similar demographic rates than those further apart. Breeding populations and foraging ranges are spatially segregated in colonial seabirds, making them ideal for studying spatial patterns in demographic rates and their effects on local population dynamics. Here we explored variation in age-dependent survival probabilities across 14 colonies of Herring Gulls Larus argentatus breeding along the Dutch North Sea coast. We used long-term mark–recapture data of marked fledglings to estimate survival, and estimated spatial autocorrelation of survival probabilities. We assessed whether survival until recruitment age or until 10 years old (close to their expected lifespan) explained variation in population trajectories of each colony. Juvenile and adult survival showed a strong, but different, north-to-south gradient in survival probability, with lower juvenile but higher adult survival in northern colonies than southern colonies, whereas the spatial pattern of immature survival was less distinct. Neither recruitment nor the proportion of 10-year-old adults alive predicted whether a colony collapsed, declined, remained stable or increased. The distinct spatial pattern in survival suggests variation in regional food availability, which do not seem to drive local population dynamics. The absence of a link between survival and colony trajectories implies that connectivity between populations plays an important role affecting population dynamics.     

Overland movement and migration phenology in relation to breeding of Arctic Terns Sterna paradisaea

It is often implicitly assumed that seabirds migrate using marine environments, but this assumption is increasingly being challenged by electronic tracking data. The arrival and departure routes of Arctic Terns breeding on the North Sea coast of the United Kingdom (UK) are unknown but there has been speculation about the possibility of overland migration. Analysis of light-level geolocator data from birds breeding on the Farne Islands suggests that these birds arrived and left their North Sea colony overland via the Irish Sea, rather than taking coastal routes along the east coast of the UK and through the English Channel. In addition, some departing birds may enter the North Atlantic by crossing Ireland rather than through the Irish Sea. The direction of arrival in spring had a more southerly orientation than the direction of autumn departure. The geolocator data allow migration phenology in relation to breeding to be defined and indicated that the birds arrived around 15 days before the first eggs were laid in the colony. Departure timing may be determined by seasonal progression and not markedly influenced by breeding success. This study supports the idea that overland migration may be a more widespread and consistent strategy for seabirds than has been realized.     

Pollution of the sea and its effects.

Marine pollution has been studied under the following groupings of effects; harm to living resources, hazards to human health, reduction of amenities and interference with other users of the sea. This paper is concerned mainly with the first two categories and their interrelation. Apart from certain seabirds affected by oil, the major stocks of marine animals show no evidence of reduction by pollution. Pollution effects are generally insignificant in relation to other factors governing reproductive success, survival, growth and population size. Even in the North Sea, which has received a greatly increased pollution load during the last three decades, both total production of fish and catch per unit of effort (a measure of abundance) of cod, haddock and plaice increased during the 20 years 1950--69. Very recent decreases have been due to over-exploitation but, except in certain estuaries and immediate coastal waters, direct damage by pollution to marine populations and ecosystems is not evident. Pollution effects can, however, be detected by chemical analysis. The paper examines human health risks arising in the marine environment, particularly from contaminated seafood, especially in relation to sewage pollution, metals such as mercury, cadmium and lead, synthetic organic substances and oil.     

Sex differentiation in seasonal distribution of the starry smooth-hound Mustelus asterias

This mark-recapture study of starry smooth-hound Mustelus asterias tagged during the summer months near the Dutch coast demonstrates a large-scale spatial sex differentiation in their circannual migration patterns and small-scale spatial sex differentiation during summer. Overwintering occurs in the North Sea, English Channel and Bay of Biscay, with significantly more males in the Northern North Sea and more females in the Bay of Biscay. During summer, sheltered sea arms off the Dutch coast were almost exclusively used by adult females. In subsequent summers post-release, both sexes were mostly confined to the Southern North Sea, suggesting philopatry.     

Spatial patterns in at-sea behaviour during spring migration by little gulls ( Larus minutus ) in the southeastern North Sea

At-sea distribution of seabirds has been studied on different scales and with different focus in many parts of the world. However, factors and/or processes causing certain patterns are often not easily explained. This also holds true for fast migrating species of international conservation concern, such as the little gull (Larus minutus) in the German Bight (southeastern North Sea). In this study, we used multiyear distributional data in combination with behavioural observations and food sampling to investigate spatial and temporal patterns and their possible causes during spring migration. The results show a highly focussed migration pattern during the last week of April and the first week of May. The river Eider seemed to play an important role as main migration route. Highest numbers were found either close to the mainland or close to the offshore islands. Little gulls used certain subareas for intense feeding (i.e. the region near Helgoland and the outlet of river Elbe) and others for migration. Hydrographic phenomena such as fronts and foam lines play an important role within the feeding sites and strongly influence behaviour and distribution. Feeding behaviour as well as samples of probable prey revealed different quality of feeding sites according to the energy density of the most abundant probable food items (drowned insects versus zooplankton and fish). In conclusion, the area utilisation of L. minutus during spring migration in the German Bight showed a clear pattern, and sites with main feeding action should be regarded as sensitive for little gulls, at least during spring migration.     

Mapping the spawning grounds of North Sea cod (Gadus morhua) by direct and indirect means

Despite recent evidence for sub-stock structuring, North Sea cod are assessed as a single unit. As a consequence, knowledge of sub-stock trends is poor. In particular, there are no recent evaluations of which spawning grounds are active. Here we report results from the first ichthyoplankton survey to cover the whole North Sea. Also, this survey, conducted in 2004, was the first to make extensive use of DNA-based molecular methods to unambiguously identify early developmental stage cod eggs. We compare the findings from the plankton survey with estimated egg production inferred from the distribution of mature cod in contemporaneous trawl surveys. Results from both approaches were in general agreement and showed hot spots of egg production around the southern and eastern edges of the Dogger Bank, in the German Bight, the Moray Firth and to the east of the Shetlands. These areas broadly coincide with known spawning locations from the period 1940 to 1970. We were, however, unable to directly detect significant numbers of cod eggs at the historic spawning ground off Flamborough (northeast coast of England). The results demonstrate that most of the major spawning grounds of cod in the North Sea are still active but that some localized populations may have been reduced to the point where it is now difficult to detect the presence of eggs in the plankton.     

The diet of Common Guillemot Uria aalge chicks provides evidence of changing prey communities in the North Sea

Local differences in feeding conditions have been suggested as a cause of regional variation in seabird demography but multi‐colony comparisons of diet are rare. In UK waters the main fish eaten by seabirds during the breeding season belong to three families: Ammodytidae, Clupeidae and Gadidae. Climate change and fishing are affecting these fish stocks and so probably impact on predators such as seabirds. We used standardized observations of prey brought in for chicks to make the first integrated assessment of the diet of Common Guillemot Uria aalge chicks at a UK scale. Chick diet varied markedly among the 23 colonies sampled between 2006 and 2011. Sandeels (Ammodytidae), probably Lesser Sandeels Ammodytes marinus, were the commonest prey. Their contribution to the diet varied both latitudinally and among marine regions, with the proportion significantly higher for a given latitude on the west coast compared to the east. The non‐sandeel component of the diet showed latitudinal changes, with small clupeids, probably Sprats Sprattus sprattus, predominant at southern colonies whereas juvenile gadids were the main alternative to sandeels in the north. Comparison of our Guillemot chick diet with data collected 15–30 years earlier suggests that the proportion of sandeels in the diet has decreased at colonies bordering the North Sea. No significant change was apparent in Atlantic colonies but historical data were limited. The early years of our study coincided with a population explosion of Snake Pipefish Entelurus aequoreus in the Northeast Atlantic and North Sea. Pipefish were recorded in Guillemot chick diet at several northern and northwestern colonies in 2006 and 2007 but have been absent since 2009. Spatial and temporal variation in chick diet accorded broadly with patterns expected as a result of rising sea temperatures and impacts of fishing. Guillemot chick diet could potentially be a useful indicator of changes in the distribution and abundance of forage fish.     

Diseases in North Sea fishes

Prior to the studies reviewed here, only lymphocystis and skeletal deformities of a variety of fish species and certain diseases of eel were known to occur in the German Bight (North Sea). From 1977 until now, 9 externally visible lesions on North Sea fishes were observed; in addition to those mentioned before, they comprise: fin rot, ulcerations, epidermal papilloma, hyperplasia, pseudobranchial tumour, eye diseases and gill swellings. With the exception of information on changes in frequencies of vertebral deformities of herring from the 1950's to the 1970's, there are no long-term data characterizing changes in frequencies of the diseases under study. For pseudobranchial tumours of cod and epidermal papilloma of dab, information is provided on occurrence and abundance. The distribution pattern of cod afflicted with pseudobranchial tumours is strongly influenced by the migratory behaviour of the fish. Epidermal papillomas of dab were more frequently found at stations within the inner German Bight than in neighbouring areas. The Bight is used for dumping of wastes from titaniumdioxide production. Further disease hot spots are areas off the Humber estuary and the British coast. Analysis of chromium in dab from the German Bight revealed elevated concentrations in epidermal tissues of specimens from the dumping area compared with that found in dab from neighbouring localities. Particulate iron was demonstrated to occur in mucous cells of dab from the dumping area. From increased levels of heavy metals with cancerogenic potential in sensitive target tissues and from increased prevalences of diseased fish in the dumping area it is concluded that these phenomena are possibly causally linked. In the vicinity of the Humber estuary high disease rates were encountered and areas with high prevalences of dab afflicted with epidermal papilloma extended over regions shown to be transport routes for persistent pollutants such as radioactive materials. It is therefore suggested that the long-range distribution of fish diseases in the southern North Sea might reflect the long-range transport of persistent pollutants.     

Matrilinear phylogeography of Atlantic salmon (Salmo salar L.) in Europe and postglacial colonization of the Baltic Sea area

Sixty‐four samples from 46 salmon populations totalling 2369 specimens were used for polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) analysis of the mitochondrial ND1 region. The final analyses included 3095 specimens from 60 populations in Northern Europe. A subsample was analysed by RFLP of ND3/4/5/6. Representative RFLP haplotypes from different parts of the distribution area were sequenced and the phylogeny of European haplotypes and their relations to the North American lineage was described. The four common European haplotypes derive from the ancestral ND1‐BBBA (rooting the European clade to the North American) by one‐step substitutions: AAAA < AABA < BBBA > BBBB. The Swedish west‐coast populations differ from the geographically close southern Baltic, indicating absence of inward and limited outward gene flow through the Danish straits during the last 8000 years. Within the Baltic Sea, only three ND1 haplotypes were detected and there was no variation for ND3/4/5/6. In the whole southern Baltic and in lakes Vänern, Ladoga and Onega the haplotype AABA dominated. Proposed postglacial colonization routes to the Baltic Sea are discussed in relation to the haplotype distribution pattern.     

Climate,copepods and seabirds in the boreal Northeast Atlantic – current state and future outlook

The boreal Northeast Atlantic is strongly affected by current climate change, and large shifts in abundance and distribution of many organisms have been observed, including the dominant copepod Calanus finmarchicus, which supports the grazing food web and thus many fish populations. At the same time, large‐scale declines have been observed in many piscivorous seabirds, which depend on abundant small pelagic fish. Here, we combine predictions from a niche model of C. finmarchicus with long‐term data on seabird breeding success to link trophic levels. The niche model shows that environmental suitability for C. finmarchicus has declined in southern areas with large breeding seabird populations (e.g. the North Sea), and predicts that this decline is likely to spread northwards during the 21st century to affect populations in Iceland and the Faroes. In a North Sea colony, breeding success of three common piscivorous seabird species [black‐legged kittiwake (Rissa tridactyla), common guillemot (Uria aalge) and Atlantic puffin (Fratercula arctica)] was strongly positively correlated with local environmental suitability for C. finmarchicus, whereas this was not the case at a more northerly colony in west Norway. Large seabird populations seem only to occur where C. finmarchicus is abundant, and northward distributional shifts of common boreal seabirds are therefore expected over the coming decades. Whether or not population size can be maintained depends on the dispersal ability and inclination of these colonial breeders, and on the carrying capacity of more northerly areas in a warmer climate.     

Identifying glacial refugia in a geographic parthenogen using palaeoclimate modelling and phylogeography: the New Zealand stick insect Argosarchus horridus (White)

We have used phylogeographic analysis of mitochondrial DNA (COI and COII genes) and ecological niche modelling (ENM) to reconstruct the population history of Argosarchus horridus (White), a widespread species of New Zealand stick insect. These data were used to address outstanding questions on the role of glacial refugia in determining the distribution and genetic structure of New Zealand species. Phylogeographic analysis shows a general pattern of high diversity in upper North Island and reduced diversity in lower North Island and South Island. The ENM indicates that during the last glacial maximum, A. horridus was largely restricted to refugia around coastal areas of North Island. The ENM also suggests refugia on the northeast coast of South Island and southeast coast of North Island and this prediction is verified by phylogeographic analysis, which shows a clade restricted to this region. Argosarchus horridus is also most likely a geographic parthenogen where males are much rarer at higher latitudes. The higher levels of genetic variation in northern, bisexual populations suggest southern and largely unisexual populations originated from southwardly expanding parthenogenetic lineages. Bayesian skyline analysis also provides support for a recent population size increase consistent with a large increase in geographic distribution in the late Pleistocene. These results exemplify the utility of integrating ENM and phylogeographic analysis in testing hypotheses on the origin of geographic parthenogenesis and effects of Pleistocene environmental change on biodiversity.