Cormorant Phalacrocorax Research Articles

Changes in habitat suitability influence non‐breeding distribution of waterbirds in central Europe

Waterbird species have different requirements with respect to their non‐breeding areas, aiming to survive and gain condition during the non‐breeding period. Selection of non‐breeding areas could change over time and space driven by climate change and species habitat requirements. To help explain the mechanism shaping non‐breeding area selection, we provide site‐specific analyses of distributional changes in wintering waterbirds in central Europe, located at the centre of their flyways. We use wintering waterbirds as a highly dynamic model group monitored over a long‐time scale of 50 years (1966–2015). We identified species habitat requirements and changes in habitat use at the level of 733 individual non‐breeding (specifically wintering) sites for 12 waterbird species using citizen‐science monitoring data. We calculated site‐specific mean numbers and estimated site‐specific trends in numbers. The site‐specific approach revealed a general effect of mean winter temperature of site (seven of 12 species), wetland type (all species) and land cover (all species) on site‐specific numbers. We found increasing site‐specific trends in numbers in the northern and/or eastern part of the study area (Mute Swan Cygnus olor, Eurasian Teal Anas crecca, Common Pochard Aythya ferina, Great Cormorant Phalacrocorax carbo and Eurasian Coot Fulica atra). Common Merganser Mergus merganser, Great Cormorant, Grey Heron Ardea cinerea, Common Pochard, Eurasian Coot and Common Moorhen Galinulla chloropus increased their site‐specific numbers on standing industrial waters with traditionally low fish stock. The site‐specific dynamics of bird numbers helped us to identify general preference for sites reducing winter harshness (warmer areas, running waters and more wetlands in the site vicinity), as well as indicating climate‐driven changes in spatial use of wintering sites (northern/north‐eastern range changes and changes in preference for industrial waters). This fine‐scale (site‐specific) approach can reveal large‐scale range and distribution shifts driven by climate and environmental changes regardless of the availability of large‐scale datasets.

Density dependence, prey accessibility and prey depletion by fisheries drive Peruvian seabird population dynamics

In marine ecosystems top predator populations are shaped by environmental factors affecting their prey abundance. Coupling top predators’ population studies with independent records of prey abundance suggests that prey fluctuations affect fecundity parameters and abundance of their predators. However, prey may be abundant but inaccessible to their predators and a major challenge is to determine the relative importance of prey accessibility in shaping seabird populations. In addition, disentangling the effects of prey abundance and accessibility from the effects of prey removal by fisheries, while accounting for density dependence, remains challenging for marine top predators. Here, we investigate how climate, population density, and the accessibility and removal of prey (the Peruvian anchovy Engraulis ringens) by fisheries influence the population dynamics of the largest sedentary seabird community (≈ 4 million individuals belonging to guanay cormorant Phalacrocorax bougainvillii, Peruvian booby Sula variegata and Peruvian pelican Pelecanus thagus) of the northern Humboldt Current System over the past half‐century. Using Gompertz state–space models we found strong evidence for density dependence in abundance for the three seabird species. After accounting for density dependence, sea surface temperature, prey accessibility (defined by the depth of the upper limit of the subsurface oxygen minimum zone) and prey removal by fisheries were retained as the best predictors of annual population size across species. These factors affected seabird abundance the current year and with year lags, suggesting effects on several demographic parameters including breeding propensity and adult survival. These findings highlight the effects of prey accessibility and fishery removals on seabird populations in marine ecosystems. This will help refine management objectives of marine ecosystems in order to ensure sufficient biomass of forage fish to avoid constraining seabird population dynamics, while taking into account of the effects of environmental variability.

Historical Breeding By Pelagic, Double-Crested, and Brandt's Cormorants In the Salish Sea, 1891–1955

Breeding within the Salish Sea by Pelagic Cormorant (Phalacrocorax pelagicus), Double-crested Cormorant (P. auritus) and Brandt's Cormorant (P. penicillatus) was summarized from published and unpublished sources for the 1891–1955 period. None of the 3 cormorant species were recorded breeding in the Salish Sea between 1792 and 1891 although sporadic breeding may have been missed. Pelagic Cormorants were first reported breeding at Mandarte Island, British Columbia, in 1891 and afterwards bred there regularly; by 1955, 22 colonies had formed in the central and northern Salish Sea, including the San Juan Islands (n = 9), Gulf Islands (n = 5), inner Strait of Juan de Fuca (n = 4), and northern Strait of Georgia (n = 4). Before regular breeding by Double-crested Cormorants began at Mandarte Island (1927) and Ballingall Islets (1934), they apparently bred sporadically at St. John's Point (Hornby Island) in the northern Salish Sea (1896) and Mandarte Island (1900). By 1955, 8 colonies had formed in the central and northern Salish Sea, including the San Juan Islands (n = 3), Gulf Islands (n = 3) and northern Strait of Georgia (n = 2). Brandt's Cormorants only bred sporadically in the San Juan Islands at Flattop Island (1928), Matia Island (1940) and Lopez Island (<1953). Evidence of breeding in the central Salish Sea by all 3 cormorant species suggested resettlement of individuals from colonies on the outer west coast of Washington through the Strait of Juan de Fuca. Subsequent expansion by Pelagic and Double-crested cormorants in the central and northern Salish Sea suggested local growth after colonization, although impacts from human disturbance and predators affected certain colonies. Reduced harvesting by the shrinking population of indigenous peoples at cormorant colonies on the outer coast of Washington likely prompted colonization of the Salish Sea.

How Nest Site Characteristics Influence Breeding Success in Red-legged CormorantsPhalacrocorax gaimardi

For seabirds, nest site features are an important factor that determines reproductive success. During three breeding seasons (2010–2012), we visited two coastal cliff colonies of Red-legged Cormorants Phalacrocorax gaimardi in the Ria Deseado, Argentina, and studied how nest site characteristics influenced their breeding success. We measured six physical characteristics at 46 nest sites, and we counted the number of fledglings produced each year from each nest (breeding success). We also related nest site temperature and wind exposure with nest site orientation. Breeding success was higher at nest sites with a broad base (greater capacity for holding young) and at nests that were less exposed to winds greater than 25 knots (46.25 km/h), which were sites with a north orientation. The lowest breeding success was observed in nest sites that were exposed to the strongest winds (i.e., sites with a south orientation). Strong winds often blow eggs and chicks away from the nests and increase opportunistic predation by gulls Larus sp. No significant relationship was found between nest site orientation and nest site temperature. Breeding success decreased with the distance to the nearest nest, which agrees with the idea that higher density of reproductive individuals reduces effectiveness of predators. Nest cover, distance from the top of the cliff, and distance from the tide line had no effect on breeding success at this study scale. Our results suggested that nest site characteristics that were related to protection against adverse weather conditions (e.g., strong winds) and avian predation, in combination with a suitable nest space, determined the breeding success of Red-legged Cormorants.

Results of the January 2017 waterbird census in Slovenia

Summary In 2017, the International Waterbird Census (IWC) was carried out in Slovenia on January 14 and 15. Waterbirds were counted on all larger rivers, along the entire Slovenian Coastland and on most of the major standing waters in the country. During the census, in which 235 observers took part, 413 sections of the rivers and coastal sea with a total length of 1,427 km and 200 other localities (164 standing waters and 36 streams) were surveyed. The census was characterized by harsh winter conditions and high proportion of frozen water bodies. Altogether, 51,790 waterbirds of 61 species were counted. Thus, the number of waterbirds and the number of species recorded were close to the 21-year average. The highest numbers of waterbirds were counted in the Drava count area, i.e. 20,064 individuals (38.7% of all waterbirds in Slovenia). By far the most numerous species was Mallard Anas platyrhynchos (46.1% of all waterbirds), followed by Coot Fulica atra (6.8% of all waterbirds), Cormorant Phalacrocorax carbo (5.9% of all waterbirds), Black-headed Gull Chroicocephalus ridibundus (5.7% of all waterbirds) and Mute Swan Cygnus olor (3.9% of all waterbirds). The number of 1,000 counted individuals was also surpassed by Yellow-legged Gull Larus michahellis, Teal An. crecca, Tufted Duck Aythya fuligula, White-fronted Goose Anser albifrons, Pygmy Cormorant P. pygmeus and Grey Heron Ardea cinerea. Among the rarer recorded species, the Red-breasted Goose Branta ruficollis (registered for the first time during the January Waterbird Censuses and only for the third time ever in Slovenia) and Barnacle Goose Branta leucopsis (the first probable A category individual for IWC and Slovenia) deserve special mention. Numbers of the following species were the highest so far recorded during the IWC: Mandarin Duck Aix galericulata (together with 2006 and 2012), Pintail An. acuta, Ferruginous Duck Ay. nyroca, Long-tailed Duck Clangula hyemalis (together with 2003), Goosander Mergus merganser, Pygmy Cormorant, Herring Gull L. argentatus and Caspian Gull L. cachinnans. Number of Pochards Ay. ferina was the lowest so far recorded during the IWC.

Antimicrobial Susceptibility and Genotypic Characteristic of Campylobacter spp. Isolates from Free-Living Birds in Poland.

Campylobacter spp. is the most commonly reported, bacterial cause of human foodborne infection worldwide. Commercial poultry and free-living birds are natural reservoirs of three particular species: Campylobacter jejuni, Campylobacter coli, and Campylobacter lari. The aim of this study was to determine the genotypic characteristics and antibiotic susceptibility of 43 Campylobacter strains, obtained from free-living birds, in Poland. In total, 700 birds were examined. The strains were isolated from 43 birds (6.14%) from the feces of 7 wild bird species: Mallard ducks Anas platyrhynchos (29 positive/121 tested), great cormorants Phalacrocorax carbo (5/77), velvet scoters Melanitta fusca (4/30), tawny owls Strix aluco (2/5), common buzzard Buteo buteo (1/3), rook Corvus frugilegus (1/6), and Eurasian tree sparrow Passer montanus (1/30). Thirty-eight (88.37%) of obtained strains belonged to C. jejuni and five (11.63%) to C. coli. Other 428 examined birds from different bird species were Campylobacter negative. The antimicrobial susceptibility to nine antimicrobials was also studied in investigated isolates of Campylobacter spp. Sixteen of the examined strains (37.21% of all positive samples) showed susceptibility to all of the nine antimicrobials. Moreover, the prevalence of selected virulence genes, such as flaA, cadF, ceuE, virB11, cdtA, cdtB, and cdtC were all analyzed. The virulence gene that was found most frequently in total number of Campylobacter strains was ceuE (72.10%) and other genes, such as flaA, cadF, cdtA, cdtB, and cdtC, were found in over 60% of all examined strains. Variable antimicrobial susceptibility and the presence of different virulence genes of examined strains, isolated from free-living birds, suggest that special attention should be given to wild birds and any potential approaches to the control of antibiotic-resistant Campylobacter should be discussed.

The Role of Hatching Asynchrony in a Seabird Species Exhibiting Obligate Brood Reduction

Fil: Giudici, Paula Ines. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Centro Nacional Patagonico. Instituto de Biologia de Organismos Marinos; Argentina

Double‐Crested Cormorants: Too Much of a Good Thing?

For centuries, people have viewed double‐crested cormorantsPhalacrocorax auritusnegatively, and human persecution coupled with environmental contamination severely reduced numbers of cormorants throughout North America. Shifts in paradigms for management of our natural resources resulted in reductions in environmental contaminants and regulatory protection of cormorants, allowing for an amazing population resurgence of this adaptable fish‐eating bird. However, for cormorants, as with some other native wildlife species the populations of which have rebounded due to conservation efforts, there have been cormorant‐societal conflicts with respect to commercial and natural resources such as aquaculture and sport fisheries. Increasing resource conflicts caused cormorants to be a priority with agencies responsible for their management, resulting in development of policy to facilitate addressing stakeholder concerns. Subsequent research and management in regard to cormorant issues have been subject to considerable challenges and debate. In this feature, we discuss the primary resource damage issues associated with cormorants, management efforts and outcomes, what we have learned, and the future with regard to cormorant management.

The advertising display of double-crested cormorants varies with microhabitat and time of the season in a tree-nesting colony

Male double-crested cormorants (Phalacrocorax auritus) perform advertising displays at potential nest locations at spring breeding grounds to attract females. Yet, there is no research on how the frequency of this behaviour changes over time or its association with habitat features. Studies of this behavioural display may provide insight into how birds choose areas for nesting, an important issue given the environmental and societal impacts of dense colonies of cormorants. Advertising behaviour was observed in trees throughout the 2014 nesting season, at six different sampling stations, using both scan sampling (for temporal changes in display frequency) and focal sampling (for temporal changes in four microhabitat variables: tree health, height in tree, nest density and presence of a nest). Advertising data (scans N = 484 birds; focal samples N = 827 birds) were divided into pre-incubation, incubation and chicks-present categories using a breeding chronology dataset. The number of cormorants advertising varied temporally and spatially. Using scan data in a marginal model, we found that the number of cormorants advertising was highest at the beginning of the season (peaking at week 3) and lowest once chicks were present. The GLM (focal data) showed that most cormorants advertised without nests especially past the second week of the season. The model also indicated that cormorants advertised in low nest density trees from pre- to mid-incubation. Contrary to our predictions based on colony expansion over the season, we did not observe an interaction of tree health*time or station*time, which suggests that the advertising display revealed a nest site selection process that was not visible at the population level.

Short distance directional migration in the threatened Socotra cormorant: link to primary productivity and implications for conservation

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 575:181-194 (2017) - DOI: https://doi.org/10.3354/meps12209 Short distance directional migration in the threatened Socotra cormorant: link to primary productivity and implications for conservation Sabir B. Muzaffar1,*, Chris Clarke1, Roxanne Whelan1, Rob Gubiani1, Timothée R. Cook2,3 1Department of Biology, United Arab Emirates University, PO Box 15551, Al Ain, United Arab Emirates 2Institute of Ecology and Environmental Sciences, Department of Evolutionary Ecology, Evolutionary Ecophysiology Team, University Pierre et Marie Curie, Bâtiment 34-44 - 5e étage, 4 place Jussieu, 75252 Paris, France 3FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa *Corresponding author: s_muzaffar@uaeu.ac.ae ABSTRACT: Conservation of threatened seabirds commonly focuses on protection of breeding areas. However, conditions at non-breeding areas also affect population dynamics, calling for a better understanding of seabird migratory ecology. In particular, it is crucial to identify the type of migration and the oceanic conditions determining non-breeding habitat selection. We studied movements of the threatened Socotra cormorant Phalacrocorax nigrogularis breeding at Siniya Island, United Arab Emirates (UAE) (35% of the world population), using platform transmitter terminals (PTTs) deployed on adults during the 2013 and 2014 breeding seasons. Concomitantly, we used remotely-sensed chlorophyll a concentration data (CHL) of areas visited by birds in the Arabian Gulf and Gulf of Oman regions (2002 to 2016 monthly averages), as an index of primary productivity. The migratory pattern of the Socotra cormorant was non-dispersive, fitting with the gregarious habits and group foraging mode of this forage fish specialist. Birds performed a short westward directional migration to islands off western UAE, then moved eastwards to the Strait of Hormuz before returning to Siniya Island. Birds concentrated at a few localities, which therefore represent areas of high conservation priority. During breeding, CHL around the colony was high. During non-breeding, however, CHL around non-breeding areas was low, even though more productive waters were present within foraging range. The mismatch between the non-breeding phase and CHL could be linked to spatial and temporal lags in responses of secondary and tertiary consumers to primary productivity. Effective conservation will necessitate a better understanding of the ecology and distribution of forage fish within the Gulf. KEY WORDS: Seabird · PTT · Chlorophyll a · Arabian Gulf · Anchovy · Herring · Flying fish · United Arab Emirates Full text in pdf format Supplementary material PreviousNextCite this article as: Muzaffar SB, Clarke C, Whelan R, Gubiani R, Cook TR (2017) Short distance directional migration in the threatened Socotra cormorant: link to primary productivity and implications for conservation. Mar Ecol Prog Ser 575:181-194. https://doi.org/10.3354/meps12209 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 575. Online publication date: July 20, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Birds as major predators of fishes in the East Kleinemonde Estuary

This study provides a quantitative account of fish predation by piscivorous birds in the temporarily open/closed East Kleinemonde Estuary and represents the first global attempt to simultaneously relate such consumption to production by a fish community in the same estuary. Cormorants and herons were the dominant predators and seasonal variations in the avifaunal community composition were noted. Based on comprehensive counts over three years, the piscivorous bird population was estimated to have consumed a maximum of 4 414 kg of fish in 1994, 2 400 kg in 1995/96 and 2 960 kg in 2004/05. In 1995/96 fish production in the East Kleinemonde Estuary (55.89 g m−2 a−1) was estimated at 9 780 kg and maximum bird predation amounted to 25% of annual fish production within the system over the same period, assuming that all birds counted on the estuary foraged there and that the diet of these birds comprised only fish. The above 1995/96 figures, together with an estimate of fish predation by the dominant piscivorous fish Lichia amia of 696 kg suggests that birds are probably the single most important natural predator of fishes within this estuary. An unusual mass invasion by marine Cape Cormorants Phalacrocorax capensis during July 1994 was responsible for large-scale predation of fish (2 155 kg) and resulted in the population of estuary-associated marine fishes declining from approximately 63 300 to about 18 600 individuals during the 1994 closed phase. Given that little or no marine fish recruitment was possible while the estuary mouth was closed, piscivorous birds are likely to have a higher predatory impact on populations of juvenile marine fishes in small temporarily closed estuaries than in larger permanently open systems.

North and South American Haplotypes ofDrepanocephalus auritus(Digenea: Echinostomatidae) Are Released fromBiomphalaria havanensis(Mollusca: Planorbidae) Inhabiting Catfish Aquaculture Ponds in Mississippi, U.S.A.

Trematodes of the subclass Digenea are a major impediment to catfish aquaculture in the southeastern United States. Catfish production ponds are ideal feeding grounds for piscivorous birds, and given the variety of aquatic snails that inhabit these ponds, they offer a prime environment for the propagation of digenetic life cycles. In July 2014, snails morphologically consistent with Biomphalaria havanensis L. Pfeiffer, 1839, were collected from 2 different catfish production ponds in the catfish farming region of eastern Mississippi. These snails were refractory to Schistosoma mansoni Sambon, 1907, infection, and phylogenetic analyses based on internal transcribed spacer (ITS)1 and ITS2 fragments placed the snails within the B. havanensis/obstructa complex. Some (1.5%) of these snails shed cercariae morphologically and molecularly consistent with Drepanocephalus auritus Kudlai, Kostadinova, Pulis, and Tkach, 2015 (formerly reported as Drepanocephalus spathans Dietz, 1909), an echinostomatid parasite of the double-crested cormorant Phalacrocorax auritus Lesson, 1831, and channel catfish Ictalurus punctatus Rafinesque, 1818. Juvenile channel catfish were challenged individually with ∼275 cercariae of D. auritus per fish, resulting in limited mortality (2 out of 10 fish). Surviving fish were euthanatized 7 d postchallenge, and the presence of metacercariae was confirmed histologically. Parasite-associated pathology was consistent with previous studies. Subsequent molecular analysis of 5 different gene targets confirmed morphological identifications. Previous research has suggested the existence of discrete North American and South American haplotypes of D. auritus. Mitochondrial cytochrome c oxidase subunit 1 and nicotinamide adenine dinucleotide dehydrogenase subunit 1 sequences demonstrated that both haplotypes were released by snails in this study, suggesting a broader distribution of these genetic variants than previously thought. Along with Planorbella trivolvis Say, 1817, this work identifies a second snail species common to catfish aquaculture ponds that releases D. auritus infective to juvenile channel catfish and is the first report of B. havanensis as an intermediate host for D. auritus in North America.

Plasma Biochemistries and Morphometric Indices of Body Condition in Imperial Cormorant (Phalacrocorax atriceps) Chicks

Fil: Gallo, Luciana. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Centro Nacional Patagonico. Instituto de Biologia de Organismos Marinos; Argentina

Occurrence of Nematodes in the alimentary tract of great cormorants [Phalacrocorax carbo (Linnaeus, 1758)] in colonies located in the upper and lower Vistula River

Abstract The occurrence of nematodes in the alimentary tract of great cormorant Phalacrocorax carbo (L., 1758) nestlings was studied in the Włocławek Reservoir located on the Vistula in central Poland and in adult birds wintering in the south of Poland, with the food base in the upper Vistula. Mixed (max 4 species) nematode infections were found in all birds. Apart from Contracaecum rudolphii Hartwich, 1964 found in all studied birds, the third- and fourth-stage larvae as well as adult individuals of the following species were also present: Eustrongylides excisus Jägerskiöld, 1909, Anisakis simplex (Rudolphi, 1809), Hysterothylacium aduncum (Rudolphi, 1802), Desmidocercella numidica Seurat, 1920, Synquaria squamata (Linstow, 1883), Cosmocephalus obvelatus (Creplin, 1825), Baruscapillaria carbonis (Dubinin et Dubinina, 1940). The overall mean intensity of infection with nematodes was 23.4 ± 11.6 in nestlings and 175.7 ± 110.9 in adult cormorants. The most common species was C. rudolphii with the mean infection intensity of 12.5 ± 5.9 in nestlings and 154.6 ± 111.4 in adults. The second most common species was E. excisus. S. squamata, C. obvelatus and D. numidica were less common in both age groups. A. simplex and H. aduncum were found only in nestlings, while B. carbonis only in adults.

Using Variance Structure to Quantify Responses to Perturbation in Fish Catches

AbstractWe present a case study evaluation of gill‐net catches of Walleye Sander vitreus to assess potential effects of large‐scale changes in Oneida Lake, New York, including the disruption of trophic interactions by double‐crested cormorants Phalacrocorax auritus and invasive dreissenid mussels. We used the empirical long‐term gill‐net time series and a negative binomial linear mixed model to partition the variability in catches into spatial and coherent temporal variance components, hypothesizing that variance partitioning can help quantify spatiotemporal variability and determine whether variance structure differs before and after large‐scale perturbations. We found that the mean catch and the total variability of catches decreased following perturbation but that not all sampling locations responded in a consistent manner. There was also evidence of some spatial homogenization concurrent with a restructuring of the relative productivity of individual sites. Specifically, offshore sites generally became more productive following the estimated break point in the gill‐net time series. These results provide support for the idea that variance structure is responsive to large‐scale perturbations; therefore, variance components have potential utility as statistical indicators of response to a changing environment more broadly. The modeling approach described herein is flexible and would be transferable to other systems and metrics. For example, variance partitioning could be used to examine responses to alternative management regimes, to compare variability across physiographic regions, and to describe differences among climate zones. Understanding how individual variance components respond to perturbation may yield finer‐scale insights into ecological shifts than focusing on patterns in the mean responses or total variability alone.Received July 26, 2016; accepted February 28, 2017 Published online April 25, 2017

Screening of protozoan and microsporidian parasites in feces of great cormorant (Phalacrocorax carbo)

The global population of great cormorants (Phalacrocorax carbo L.) is on the rise. These birds, characterized by rapid metabolism, can deposit large quantities of feces, and because they breed on the land but forage on water, both terrestrial and aquatic environments can be simultaneously affected by their activities. The contribution of great cormorants in the dispersal of bacterial and viral pathogens has been immensely studied; whereas, the occurrence of eukaryotic parasites such as protozoans and microsporidians in these birds is little known. The present study investigated the presence of dispersive stages of potentially zoonotic protozoans belonging to the genera Blastocystis, Giardia and Cryptosporidium, and Microsporidia spores in feces collected from birds inhabiting the breeding colony established at one lake island in Poland, Europe. The feces were examined by coprological techniques (staining with iron hematoxylin, Ziehl-Neelsen, and modified Weber’s chromotrope 2R–based trichrome), and with immunofluorescence antibody MERIFLUOR Cryptosporidium/Giardia assay. As found, the Cryptosporidium oocysts were identified rarely in 8% of samples (2/25; 3–5 × 103/g) and no cysts of Giardia and Blastocystis were detected. Microsporidian spores were detected in 4% of samples (1/25) but at very high frequency (4.3 × 104/g). No dispersive stages of parasites were identified in water samples collected from the littoral area near the colony. Despite the profuse defecation of cormorants, their role in the dispersion of the investigated parasites may not be as high as hypothesized.

The role of cormorants, fishing effort and temperature on the catches per unit effort of fisheries in Finnish coastal areas

Population increase of piscivorous cormorants in Europe and in North America has created a conflict between fisheries and the species. The impact of cormorants on natural fish populations and yields of fishermen is still under debate. We investigated potential connection of the great cormorant Phalacrocorax carbo abundance, fishing effort and water temperature with the economically important perch Perca fluviatilis and pikeperch Sander lucioperca yields, measured as catches per unit of effort (CPUE) in gillnet fishing along the Finnish coastal areas (Baltic Sea) using 50km International Council for the Exploration of the Sea (ICES) grids. Since cormorants generally take smaller prey than fishermen, we expected 2–5 years time lag effect of the cormorant numbers on CPUE. Correspondingly, we expected 4–7 years lag effect of temperature on CPUE. Despite the population increase of cormorants, CPUE of perch increased in 10 out of 29 ICES grids during the study period 2005–2014. Pikeperch CPUE increased in five out of 24 grids and decreased in one. There was significant annual variation in CPUE values of perch and pikeperch, but values were not significantly associated with changes in cormorant numbers and temperature either annually or long-term. However, the CPUE values of pikeperch decreased towards the north, which is likely temperature driven as northern colder waters are less suitable for this species than southern waters. There was no clear evidence that either predation by cormorants or fishing effort are associated with long-term trends of perch and pikeperch stocks on a larger scale along the Finnish coast. The increasing CPUE values in several areas indicate that stocks are more abundant than ten years ago despite an increasing cormorant population. Our study approach can be used to monitor potential changes in stocks and impacts of cormorant in the future.

Group foraging in Socotra cormorants: A biologging approach to the study of a complex behavior.

Group foraging contradicts classic ecological theory because intraspecific competition normally increases with aggregation. Hence, there should be evolutionary benefits to group foraging. The study of group foraging in the field remains challenging however, because of the large number of individuals involved and the remoteness of the interactions to the observer. Biologging represents a cost‐effective solution to these methodological issues. By deploying GPS and temperature–depth loggers on individuals over a period of several consecutive days, we investigated intraspecific foraging interactions in the Socotra cormorant Phalacrocorax nigrogularis, a threatened colonial seabird endemic to the Arabian Peninsula. In particular, we examined how closely birds from the same colony associated with each other spatially when they were at sea at the same time and the distance between foraging dives at different periods of the day. Results show that the position of different birds overlapped substantially, all birds targeting the same general foraging grounds throughout the day, likely following the same school of fish. There were as many as 44,500 birds within the foraging flock at sea at any time (50% of the colony), and flocking density was high, with distance between birds ranging from 8 to 1,380 m. Birds adopted a diving strategy maximizing time spent underwater relative to surface time, resulting in up to 72% of birds underwater in potential contact with prey at all times while foraging. Our data suggest that the benefits of group foraging outweigh the costs of intense aggregation in this seabird. Prey detection and information transmission are facilitated in large groups. Once discovered, shoaling prey are concentrated under the effect of the multitude. Fish school cohesiveness is then disorganized by continuous attacks of diving birds to facilitate prey capture. Decreasing population size could pose a risk to the persistence of threatened seabirds where group size is important for foraging success.

Characterisation of 11 Microsatellite DNA Markers from the Neotropic Cormorant (Phalacrocorax Brasilianus)

The advances of molecular techniques have increased the development of cost and time-effective libraries of molecular markers, such as microsatellites, which allow us to estimate genetic parameters in order to characterise species' population structures. The Neotropic Cormorant ( Phalacrocorax brasilianus) is one of the most abundant and widespread seabirds from the American continent, being present in a wide range of habitats, however further information about genetic markers in this species is scarce. A total of 26 pairs of primers were synthesised and 22 microsatellites were amplified correctly; 11 of them were polymorphic. The number of alleles per locus ranged from three to seven with a mean of 4.6 per locus. Six loci showed significant departure from Hardy–Weinberg equilibrium. The microsatellite markers identified and characterised in the present study are the first set developed for P. brasilianus and will contribute to the genetic map, quantitative traits mapping, and phylogenetic analysis of this species.

Exploring potential effects of cormorant predation on the fish community in Saginaw Bay, Lake Huron

Abstract Stakeholders and fishery managers expressed concern that double-crested cormorant Phalacrocorax auritus predation may be a factor in the recent poor survival of yellow perch Perca flavescens in Saginaw Bay. We quantified cormorant diets from two nesting colonies in Saginaw Bay during April–September in 2013 and 2014, with special emphasis on impacts to yellow perch. Cormorants (n = 691) were collected when returning to colonies after foraging. Stomachs were removed and preserved in the field. Diet items were identified, enumerated, and measured (n = 23.373). Cormorant diets from Saginaw Bay indicate a heavy reliance on round goby and Notropis species as prey during the breeding season, consistent with other areas of the Great Lakes where round goby and cormorants coincide. Respectively, the three most common prey species observed by number (%) and biomass (%) pooled across years and sites were round goby Neogobius melanostomus (56.6%, 42.1%), emerald shiner Notropis antherinoides (25.2%, 12.5%), and yellow perch (8.0%, 14.1%). Diet composition was more variable at Spoils Island than at Little Charity Island. Overall cormorant consumption (estimated using cormorant consumption demand rates) of yellow perch was compared to walleye consumption. Cormorant consumption of age-1 yellow perch was 13–17% as much as mean walleye consumption of yellow perch in 2013 and 8–11% in 2014. The cumulative effects of walleye and spring cormorant predation likely represent a recruitment bottleneck for yellow perch in Saginaw Bay. Future studies determining age-specific abundance of yellow perch would facilitate better determination of cormorant predation significance.