Double-crested Cormorants Phalacrocorax Auritus Research Articles

Genetic Sequence Data Identifies the Cercaria of Drepanocephalus spathans (Digenea: Echinostomatidae), A Parasite of the Double-Crested Cormorant (Phalacrocorax auritus), with Notes on its Pathology in Juvenile Channel Catfish (Ictalurus punctatus)

An unidentified xiphidio-type cercaria, previously thought inconsequential to catfish health, was found to be released from marsh rams-horn snails (Planorbella trivolvis) inhabiting ponds on a commercial catfish operation in the Mississippi Delta. A preliminary challenge of cohabiting channel catfish ( Ictalurus punctatus ) with snails actively shedding the unidentified cercariae resulted in death of some fish. A second cohabitation trial yielded similar results, as did a third challenge of 250 cercariae/fish. Histopathology revealed developing metacercariae concentrated in the cranial region, especially within the branchial chamber, with several metacercariae at the base of the branchial arches within, or adjacent to, blood vessels, possibly the proximate cause of death. Genetic sequence analysis of the 18S small subunit ribosomal DNA (ssDNA), 28S large subunit rDNA (lsDNA), and cytochrome oxidase (Cox1) genes all matched the cercariae to Drepanocephalus spathans (Digenea: Echinostomatidae), a parasite of the double-crested cormorant (Phalacrocorax auritus), a piscivorous bird endemic on most catfish farms. This is the first commentary regarding pathology of D. spathans in juvenile channel catfish as well as the first report of the marsh rams-horn snail as an intermediate host in the D. spathans life cycle. The data presented here suggest this parasite could have limiting effects on catfish production, further supporting the need for adequate snail control programs to reduce trematode prevalence on commercial catfish operations.

Effects of egg oiling on ground-nesting double-crested cormorants at a colony in Lake Ontario: an examination of nest-attendance behaviour

Context We assessed the effects of egg oiling on ground-nesting double-crested cormorants (Phalacrocorax auritus) in the context of an emerging management strategy for the largest known cormorant colony on the lower Great Lakes. We designed the present study to answer specific questions in response to concerns raised by stakeholders and members of the public regarding this management technique. Aims The aim of the present study was to examine the behavioural response of adult cormorants to egg oiling. Prior work on this issue has focussed on population-response questions rather than the behavioural level. Consequently, detailed observations on how cormorants respond to egg oiling are lacking. Methods Using instantaneous and focal observations to measure behaviours, we compared Treatment nests (n = 24, 23) to Control (n = 24) and Sham (handled, but not treated; n = 24) nests. We observed nest attendance, incubation and mate-presence behaviour, and divided observations into pre-chick and entire-season categories for analysis. Key results Our study determined that egg oiling does not cause immediate nest desertion by adult birds; Treatment birds incubated their nests as long as did Sham and Control birds. We found no difference among the three groups in the proportion of time a mate was present during incubation for Control and Sham nests in the pre-chick period. We found that the total seasonal duration of nest attendance by Treatment birds was shorter than that for the birds in the other groups. Conclusions Both incubation and mate-presence data suggest that egg oiling did not measurably affect the behaviour of adult cormorants in the pre-chick period. Our study also suggests that Treatment birds attended their nest long enough to preclude re-nesting within the breeding season, although this may not apply for regions with longer nesting seasons. Implications Our study indicates that egg oiling, administered judiciously, may be an appropriate management technique for ground-nesting cormorants, although management targets must be clearly articulated.

Assessing the Validity of the Accelerometry Technique for Estimating the Energy Expenditure of Diving Double-Crested CormorantsPhalacrocorax auritus

Over the past few years, acceleration-data loggers have been used to provide calibrated proxies of energy expenditure: the accelerometry technique. Relationships between rate of oxygen consumption and a derivation of acceleration data termed "overall dynamic body acceleration" (ODBA) have now been generated for a range of species, including birds, mammals, and amphibians. In this study, we examine the utility of the accelerometry technique for estimating the energy expended by double-crested cormorants Phalacrocorax auritus to undertake a dive cycle (i.e., a dive and the subsequent pause at the surface before another dive). The results show that ODBA does not calibrate with energy expenditure in diving cormorants, where energy expenditure is calculated from measures of oxygen uptake during surface periods between dives. The possible explanations include reasons why energy expenditure may not relate to ODBA but also reasons why oxygen uptake between dives may not accurately represent energy expenditure during a dive cycle.

Lack of Angling-Sized Yellow Perch in a Canadian Boreal Lake: Potential Influences of Growth Rate, Diet, and Predation by Double-Crested Cormorants

Fisheries for yellow perch Perca flavescens are economically important in North America, but in many lakes this species does not attain sizes desirable to anglers (total length [TL] > 250 mm). We investigated factors potentially contributing to the lack of angling-sized yellow perch in Dore Lake, Saskatchewan. This large boreal lake has a long history of exploitation and is subject to current controversy regarding the impact of double-crested cormorants Phalacrocorax auritus on its fisheries. We found that yellow perch in Dore Lake attained greater maximum ages (mean ± SD = 7.4 ± 1.0 years) but smaller maximum sizes (215 ± 7 mm TL) than other yellow perch populations. Thus, the lack of angling-sized yellow perch in Dore Lake is probably the result of slow growth rates rather than short life spans. Double-crested cormorants preyed heavily on yellow perch, but predation was highly skewed toward much smaller sizes (<100 mm TL) than those preferred by anglers. Stomach contents and stable nitrogen isotopes confirmed that yellow perch in Dore Lake undergo expected ontogenetic diet shifts and become predominantly piscivorous at around age 3. Analysis with stable isotopes also revealed long-term dietary differences between age-2 and age-3 yellow perch captured in littoral versus offshore habitats, suggesting some degree of intrapopulation variability in resource and habitat use among yellow perch in Dore Lake.

Influence of Diet of Double-Crested Cormorants on Thiamine, Lead, and Mineral Contents of Their Eggs

ABSTRACT Throughout much of the Great Lakes basin, reproduction of several fish species is impaired by deficiency of thiamine in their eggs, an effect attributed to consumption of thiaminase-containing forage species, primarily alewife (Alosa pseudoharengus.) Because the double-crested cormorant (Phalacrocorax auritus) nesting on islands in Lake Ontario is known to consume considerable amounts of alewife, we examined cormorant food habits and measured thiamine content in eggs collected in 1999 from six separate nests of cormorants from colonies near Lake Ontario and contrasted them with food habits and eggs of cormorants from Oneida Lake where the alewife is rare. Thiamine concentrations in eggs varied between 4.31 and 11.24 nmoleslg with no significant (P>0.18) difference between mean concentrations for Lake Ontario and Oneida Lake (8.08 vs 8.36 nmoles/g) even though alewife comprised approximately 65 vs 0 % of their diets, respectively. Consumption of other thiaminase-containing species was minor in both lakes. Therefore, consumption of alewife and other thiaminase containing fishes by cormorants on Lake Ontario did not appear to significantly impair the levels of thiamine in their eggs. However, we found that the concentration of thiamine in eggs (T; nmoles/g) was inversely related (P<0.02) to lead (Pb) concentration (μg/g) according to the equation: T = −3.142 Pb + 16.25. This relationship may reflect the known ability of thiamine to chelate lead and increase its excretion.

Water Regurgitation by Adult Double-crested Cormorants: A Possible Mechanism to Assist in Chick Thermoregulation

Abstract A previously undocumented thermoregulatory behavior of adult cormorants for their pre-fledged young was recorded during observations of a Double-crested Cormorant (Phalacrocorax auritus) colony in Lake of the Woods, Ontario. Many adult cormorants were observed regurgitating water over their chicks’ bodies. The authors believe that the warm temperature, intense sun, and calm winds during the observation periods were the primary factors triggering this previously undocumented thermoregulatory behavior.

Fledgling Double-crested Cormorants Rehearse a Food Manipulation Technique with Woody Debris, Algae, and Shells

Abstract Fledgling Double-crested Cormorants (Phalacrocorax auritus) were observed practicing food manipulation techniques with large sticks, algae, and shells at their respective natal colonies in eastern Lake Ontario, North Channel of Lake Huron, and Lake of the Woods. Although practice behaviors have been documented for other species of waterbirds, this behavior has not been recorded previously for Double-crested Cormorants.

Incidental catch of seabirds in Newfoundland and Labrador gillnet fisheries, 2001-2003

Incidental catch of seabirds in gillnet fisheries in Newfoundland and Labrador, Canada, has been identified in several fisheries, but defendable estimates are unavailable. Despite reduced fishing effort in several fisheries, concern remains that catch rates might negatively impact local seabird populations. Based on data sources within Fisheries and Oceans Canada (St. John's, Canada), total numbers of incidentally caught seabirds in nearshore and offshore Newfoundland waters were estimated for the years 2001, 2002 and 2003. Incidental catch rates were derived using net-days as measures of effort, with fishing trips as sampling units. Confidence intervals were estimated using resampling techniques. Most reports originated from the nearshore gillnet fishery for Atlantic cod Gadus morhua, although many birds were captured in other fisheries. The most commonly captured seabirds were murres Uria sp. and shearwaters (genera Calonectris and Puffinus), although other species were also captured in smaller numbers. As many as 2000 to 7000 murres, over 2000 shear- waters (various species), and tens to hundreds of northern fulmars Fulmarus glacialis, gannets Morus bassanus, double-crested cormorants Phalacrocorax auritus, loons (genus Gavia), eider ducks Soma- teria mollissima, razorbills Alca torda, puffins Fratercula arctica, black guillemots Cepphus grylle and dovekies Alle alle were estimated to have been captured annually in the area during the period 2001 to 2003, although catches varied considerably from year to year. Populations of these species are not presently thought to be declining due to this incidental mortality; however, present catch levels may contribute to limited growth in these populations, and populations might be affected if fishing effort were to increase.

Incidental catch of seabirds in Newfoundland and Labrador gillnet fisheries, 2001-2003

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 5:149-160 (2008) - DOI: https://doi.org/10.3354/esr00094 Incidental catch of seabirds in Newfoundland and Labrador gillnet fisheries, 2001–2003 Steven Benjamins1,3,*, David W. Kulka2, Jack Lawson2 1Whale Research Group, Biology Annex, Memorial University of Newfoundland, 297 Mt. Scio Road, St. John’s, Newfoundland and Labrador A1B 3V6, Canada 2Fisheries and Oceans Canada, PO Box 5667, St. John’s, Newfoundland and Labrador A1C 5X1, Canada 3Present address: Joint Nature Conservation Committee, Monkstone House, City Road, Peterborough, Cambridgeshire PE1 1JY, UK *Email: stevenbenjamins@yahoo.com ABSTRACT: Incidental catch of seabirds in gillnet fisheries in Newfoundland and Labrador, Canada, has been identified in several fisheries, but defendable estimates are unavailable. Despite reduced fishing effort in several fisheries, concern remains that catch rates might negatively impact local seabird populations. Based on data sources within Fisheries and Oceans Canada (St. John’s, Canada), total numbers of incidentally caught seabirds in nearshore and offshore Newfoundland waters were estimated for the years 2001, 2002 and 2003. Incidental catch rates were derived using net-days as measures of effort, with fishing trips as sampling units. Confidence intervals were estimated using resampling techniques. Most reports originated from the nearshore gillnet fishery for Atlantic cod Gadus morhua, although many birds were captured in other fisheries. The most commonly captured seabirds were murres Uria sp. and shearwaters (genera Calonectris and Puffinus), although other species were also captured in smaller numbers. As many as 2000 to 7000 murres, over 2000 shearwaters (various species), and tens to hundreds of northern fulmars Fulmarus glacialis, gannets Morus bassanus, double-crested cormorants Phalacrocorax auritus, loons (genus Gavia), eider ducks Somateria mollissima, razorbills Alca torda, puffins Fratercula arctica, black guillemots Cepphus grylle and dovekies Alle alle were estimated to have been captured annually in the area during the period 2001 to 2003, although catches varied considerably from year to year. Populations of these species are not presently thought to be declining due to this incidental mortality; however, present catch levels may contribute to limited growth in these populations, and populations might be affected if fishing effort were to increase. KEY WORDS: Incidental catch · Seabirds · Newfoundland and Labrador · Canada · Murres · Shearwaters Full text in pdf format PreviousNextCite this article as: Benjamins S, Kulka DW, Lawson J (2008) Incidental catch of seabirds in Newfoundland and Labrador gillnet fisheries, 2001–2003. Endang Species Res 5:149-160. https://doi.org/10.3354/esr00094 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 5, No. 2-3. Online publication date: December 23, 2008 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2008 Inter-Research.

Prehistoric Human Impacts on Waterbirds at Watmough Bay, Washington, USA

ABSTRACT The well-preserved faunal remains from shell middens in the Pacific Northwest of North America provide a unique opportunity for investigation of the long-term history of human and animal interactions in coastal settings. Recent analysis of a large sample of birds from the Watmough Bay site (45-SJ-280) in the Gulf of Georgia reveals dramatic changes in hunting practices between ca. AD 300–700. Initially the site occupants hunted Double-crested Cormorant (Phalacrocorax auritus) chicks from nearby nesting colonies. Subsequently, diving ducks were hunted more intensively. The most likely hypothesis is that the cormorants moved their nesting colonies farther away from Watmough Bay in response to repeated human hunting, and people living at the site switched instead to hunting sea ducks, possibly using submerged netting technology. In addition to adding to our knowledge about the impacts of pre-industrial human hunting, the evidence from Watmough Bay provides data about past breeding distributions and relative abundances of bird species that may be of value in addressing biological conservation issues.

Investigating the functional link between prey abundance and seabird predatory performance

Investigating the relationships that link marine top predators and their prey is crucial for an understanding of the mechanisms that operate within marine food chains. Many seabird species capture their prey underwater, where direct and continuous observation is difficult. However, in a captive setting, predator-prey interactions can be studied under controlled conditions and in great detail. Using an underwater video-array, we investigated the prey-capture behaviour of a foot- propelled pursuit diver, the double-crested cormorant Phalacrocorax auritus, targeting juvenile rain- bow trout Oncorhynchus mykiss. We tested the effects of prey density, prey size, light conditions and prey behaviour (schooling vs. solitary trout) on the foraging performance of 9 cormorants. As pre- dicted, prey density exerted the strongest influence on cormorant foraging success. While we found an apparently linear relationship between prey density and prey capture rate, a density below the threshold of about 2 g m -3 resulted in disproportionately lower catch per unit effort (CPUE) values. If such a threshold density exists in a natural setting, it could have important implications for birds con- fronted with a decline in food abundance, when density levels will be reduced. We also demonstrate the marked impact of fish behaviour on the predatory performance of cormorants. Capture success of cormorants was significantly lower and pursuit duration significantly higher when birds attacked schooling rather than solitary trout. By contrast, prey size and light conditions did not have a measur- able effect on cormorant prey-capture performance. Our study is an experimental investigation into the prey-capture performance of an avian pursuit diver within a captive setting. We provide input values that should be incorporated into ecological models, which might help to understand predator requirements in a changing environment.

MOVEMENTS OF DOUBLE-CRESTED CORMORANTS FLEDGED ON THE COLUMBIA RIVER ESTUARY

Double-crested cormorants (Phalacrocorax auritus) have been the subject of increased research throughout North America in recent years, primarily as a result of conflicts with sport and commercial fisheries (Nettleship and Duffy 1995; Hatch and Weseloh 1999; Tobin 1999). In the Pacific Northwest, attention has been focused on the consumption of juvenile salmonids by double-crested cormorants in the Columbia River estuary (Collis and others 2002; Roby and others 2003; Anderson and others 2004). Most cormorant research has addressed food habitats, foraging patterns, and productivity. Little information is available concerning migration patterns and long-term movements of west coast cormorants. Erwin

A comparison of three methods to investigate the diet of breeding double-crested cormorants (Phalacrocorax auritus) in the Beaver Archipelago, northern Lake Michigan

A comparison of three methods to investigate the diet of breeding double-crested cormorants (Phalacrocorax auritus) in the Beaver Archipelago, northern Lake Michigan

Nutrient transfer from sea to land: the case of gulls and cormorants in the Gulf of Maine

1. The structure of communities is influenced by the transport of resources across ecosystem boundaries. Seabirds are capable of introducing large amounts of marine-derived nutrients to land, thereby modifying resource availability to terrestrial species. 2. In this study we investigated the hypothesis that variation in nesting densities of great black-backed gulls Larus marinus and double-crested cormorants Phalacrocorax auritus would modify the effect of these species on soil nutrients and plant species composition on offshore islands in the Gulf of Maine, USA. 3. Our results showed a significant positive correlation between nest density and concentrations of ammonia and nitrate in soils, but no significant relationship between nest density and phosphate. Ammonia and phosphate concentrations were good predictors of plant species composition; there were more annual forbs than perennial grasses in the abandoned cormorant colony compared with the gull colonies. Extremely high concentrations of ammonia in the highest density colony (active cormorant) may have been the main factor inhibiting plant germination at this site. All of the plant species in gull and cormorant colonies showed enriched delta(15)N signatures, indicating substantial input of marine-derived nitrogen from seabirds. 4. Our study demonstrated that gulls and cormorants are effective vectors for the transport of marine nutrients to terrestrial ecosystems. However, transported nutrients occurred in particularly high concentrations in areas with nesting cormorants. Nesting densities and species-specific variation in resource transport should be considered when predicting the effects of seabirds and other biogenic vectors of allochthonous resources.

The Effect of Oil Spraying on Eggs of Double-Crested Cormorants

Spraying eggs with oil has been used as a method of decreasing the reproductive success of super abundant avian species. Double-crested Cormorant (Phalacrocorax auritus) abundances have created a potential disturbance to some endangered species of birds, sport fishing communities and aquaculture facilities. The hatching success of oil sprayed Double-crested Cormorant eggs was investigated. Oil spraying was done during the first, second, or third week of the egg’s incubation to determine the most effective time during the incubation period for a one-time treatment. The oil spraying technique was 95–98% effective at preventing hatching. Hatching success was independent of the week of incubation that an egg was sprayed with oil. The maximum number of eggs on the colony occurred four weeks after the first egg was laid. This would be the most efficient week to spray the colony to decrease hatching success.

Conservation Implications of the Large Colony of Double-crested Cormorants on East Sand Island, Columbia River Estuary, Oregon, U.S.A.

Abstract The breeding colony of the Double-crested Cormorant (Phalacrocorax auritus) on East Sand Island in the Columbia River estuary has grown dramatically over the last 13 years, in contrast to declines at other colonies along the coast of the Pacific Northwest. Immigration from other colonies has occurred and the East Sand Island colony is now the largest for the species on the Pacific coast of North America. Despite substantial increases in the size of the East Sand Island colony, overall numbers of the West Coast subspecies (P. a. albociliatus) appear to be slowly increasing relative to the interior population (P. a. auritus). Based on the most recent regional population data available, a conservative estimate indicates that the colony on East Sand Island represents over 30% of P. a. albociliatus breeding adults. We advocate that the subspecies P. a. albociliatus be considered a distinct population segment and managed according to overall population size and trends for this subspecies.

DIET OF DOUBLE-CRESTED CORMORANTS (PHALACROCORAX AURITUS) WINTERING ON THE CENTRAL TEXAS COAST

Abstract Diets of double-crested cormorants (Phalacrocorax auritus) wintering on the central Texas coast were determined from the contents of 51 stomachs from Lavaca Bay and 28 stomachs from upper Laguna Madre. Diets consisted primarily of striped mullet (Mugil cephalus) and Gulf menhaden (Brevoortia patronus) in Lavaca Bay and striped mullet and Gulf toadfish (Opsanus beta) in upper Laguna Madre. Birds seemed to prefer striped mullet in both bays, and these fish were significantly larger than the other fish consumed. There were no differences between bays in the numbers of fish in bird stomachs; however, fish consumed by birds in upper Laguna Madre were larger than those taken by birds in Lavaca Bay. Based on the results of this study, there is no evidence that double-crested cormorants pose a significant threat to commercial or sport fisheries on the Texas Gulf Coast.

Relative Vulnerability to Avian Predation of Juvenile Salmonids Tagged with Passive Integrated Transponders in the Columbia River Estuary, 1998–2000

Abstract Caspian terns Sterna caspia and double-crested cormorants Phalacrocorax auritus that colonize dredge-spoil islands in the Columbia River estuary prey upon millions of juvenile Pacific salmonids annually. We estimated the relative vulnerability of various salmonid stocks to these predators by using data from passive integrated transponder (PIT) tags detected on these colonies; 96,382 tags were detected from the 1998–2000 migration years. On tern colonies, detection rates were highest for tags from steelhead Oncorhynchus mykiss and lowest for tags from yearling chinook salmon O. tshawytscha. However, detection rates on cormorant colonies were similar for tags from steelhead and coho salmon O. kisutch but lower for tags from yearling chinook salmon. Analyses based on migration history showed tags of transported fish were frequently detected in lower proportions than those of their counterparts that migrated in-river, the pattern being most pronounced in steelhead. Analyses based on origin (hatchery ...

Estimates of Changes in Seabird Numbers in the Grand Manan Archipelago, New Brunswick, Canada

Abstract A census of the Grand Manan Archipelago, New Brunswick, Canada, found nine seabird species nesting at 22 sites. Herring Gull (Larus argentatus) and Common Eider (Somateria mollissima) were the most widely distributed species, with a combined 89% of all breeding seabirds in the region. Although fewer, the Great Black-backed Gull (Larus marinus) and Black Guillemot (Cepphus grylle) were widely distributed. Other seabirds had more limited distributions; one Common Tern (Sterna hirundo) colony, three Double-crested Cormorant (Phalacrocorax auritus) colonies and one mixed colony of Razorbill (Alca torda) and Common Murre (Uria aalge). Leach’s Storm-Petrel (Oceanodroma leucorhoa) numbers were not determined, but were found nesting on three islands and were suspected to be nesting on two others. Comparisons with historical data showed increases in gulls, Razorbill and Common Murre, whereas eiders had remained relatively stable over the past two decades, but had decreased in recent years. Insufficient da...

Colony Size and Diet Composition of Piscivorous Waterbirds on the Lower Columbia River: Implications for Losses of Juvenile Salmonids to Avian Predation

We investigated colony size and diet composition of piscivorous waterbirds (gulls, terns, and cormorants) nesting on the lower Columbia River from the mouth (river km 0) to the head of McNary Pool (river km 553) in 1997 and 1998. The study was prompted by concern that avian predation might constitute a significant source of mortality to juvenile salmonids Oncorhynchus spp. during out-migration. The diet of California gulls Larus californicus and ring-billed gulls L. delawarensis nesting in colonies above The Dalles Dam (river km 308) included few fish and very few juvenile salmonids. The sole exception was a small colony of California gulls in which salmonids accounted for 15% (by mass) of the diet. Juvenile salmonids were, however, an important component of the diet of colonial waterbirds nesting in the Columbia River estuary. On Rice Island (river km 34), salmonids accounted for 74% (by mass) of the diet of Caspian terns Sterna caspia, 46% for double-crested cormorants Phalacrocorax auritus, and 11% for glaucous-winged−western gulls L. glaucescens × L. occidentalis. Juvenile salmonids were especially prevalent in the diets of colonial waterbirds on Rice Island during April and May. By comparison, juvenile salmonids were significantly less prevalent in the diet of cormorants and gulls nesting lower in the estuary on East Sand Island (river km 8), presumably due to the greater availability of marine forage fishes. Our results indicate that avian predation on juvenile salmonids in the lower Columbia River is more prevalent in the estuary than near the large upriver gull colonies. Furthermore, the high incidence of salmonids in the diets of Caspian terns, cormorants, and gulls nesting on Rice Island suggests that the impact of avian predation on survival of smolts may be reduced by discouraging piscivorous birds from nesting there, while encouraging nesting on East Sand Island and other sites nearer to marine foraging areas.