The great Cormorant (<i>Phalacrocorax carbo</i>) at lower lake Constance/Germany: dietary composition and impact on commercial fisheries

Gaye-Siessegger, Julia

doi:10.1051/kmae/2014015

Cited by 7 publications

(6 citation statements)

References 15 publications

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“…The cormorant is an opportunistic predator, the diet of which is primarily comprised of a few of the most abundant fish species of small sizes (Martyniak et al 2003, Russel et al 2003, Gwiazda and Amirowicz 2010, Gaye-Siessegger 2014, OvegDrd et al 2017). Seasonal and spatial variation is often observed in the diet of the cormorant nesting in northeastern Poland (Martyniak et al 1997, Krzywosz andTraczuk 2012).…”

Section: Discussionmentioning

confidence: 99%

Great cormorant (Phalacrocorax carbo) predation on pikeperch (Sander lucioperca L.) in shallow eutrophic lakes in Poland

Traczuk

Kapusta

2017

Archives of Polish Fisheries

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Abstract. Increases in the population abundance of the piscivorous great cormorant (Phalacrocorax carbo) has led to conflicts with fisheries. Cormorants are blamed for decreased fish catches in many lakes in Poland. The aim of this paper is to describe to role of pikeperch (Sander lucioperca) in the diet of cormorants nesting in a colony on the island in Lake Warno³ty. Since the breeding colony is located in the vicinity of Lake OEniardwy, the largest lake in Poland, the cormorants use the resources in this lake. In 2009-2016, 18,432 regurgitated fish were collected, of which 593 were pikeperch. The share of pikeperch among fish collected in 2009-2012 did not exceed 2%, but from 2013 this increased substantially to maximum of 38.2% in 2015. The smallest pikeperch had a standard length of 8.4 cm, and the largest 42.5 cm. Pikeperch mean length differed by year, and the length distribution was close to normal. The sizes of the regurgitated pikeperch indicate that cormorants prey almost exclusively on juvenile specimens. The results of the present study indicate that cormorant predation has a significant impact on pikeperch populations in lakes in the vicinity of the colony, and the great cormorants are possibly a significant factor in the effectiveness of pikeperch management. When planning for the management of fish populations in lakes subjected to cormorant predation pressure, it should be borne in mind that predation by this piscivorous bird species impacts the abundance and size-age structure of fish populations.

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Section: Discussionmentioning

confidence: 99%

Great cormorant (Phalacrocorax carbo) predation on pikeperch (Sander lucioperca L.) in shallow eutrophic lakes in Poland

Traczuk

Kapusta

2017

Archives of Polish Fisheries

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“…For this purpose, morphological prey mass estimations via regression formulae based on prey hard parts are commonly used (e.g.,. Keller, ; Veldkamp, ; Gaye‐Siessegger, ). Unfortunately, the erosion of hard parts during digestion can bias the size estimation and therefore this method is criticized (Carss & Group, ).…”

Section: Discussionmentioning

confidence: 99%

Diet analysis in piscivorous birds: What can the addition of molecular tools offer?

Oehm

Thalinger

Eisenkölbl

et al. 2017

Ecology and Evolution

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In trophic studies on piscivorous birds, it is vital to know which kind of dietary sample provides the information of interest and how the prey can be identified reliably and efficiently. Often, noninvasively obtained dietary samples such as regurgitated pellets, feces, and regurgitated fish samples are the preferred source of information. Fish prey has usually been identified via morphological analysis of undigested hard parts, but molecular approaches are being increasingly used for this purpose. What remains unknown, however, is which dietary sample type is best suited for molecular diet analysis and how the molecular results compare to those obtained by morphological analysis. Pellets, feces, and regurgitated fish samples of Great Cormorants (Phalacrocorax carbo sinensis) were examined for prey using both morphological hard part analysis and molecular prey identification. The sample types and methods were compared regarding number of species detected (overall and per sample) as well as the prey species composition and its variability among individual samples. Via molecular analysis, significantly higher numbers of prey species were detected in pellets, feces, and fish samples. Of the three sample types, pellets contained the most comprehensive trophic information and could be obtained with the lowest sampling effort. Contrastingly, dietary information obtained from feces was least informative and most variable. For all sample types, the molecular approach outperformed morphological hard part identification regarding the detectable prey spectrum and prey species composition. We recommend the use of pellets in combination with molecular prey identification to study the diet of piscivorous birds.

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“…) or reduced in size due to digestive erosion, prey hard part remains were measured in this study to estimate the size of the fish via regression formulae available for a wide variety of fish taxa (e.g. Härkönen , Gaye‐Siessegger ).…”

Section: Discussionmentioning

confidence: 99%

“…The length of the fish prey was either measured directly on undigested fish or calculated from fish‐bone regressions. For the latter, intact key bones were measured under a dissecting microscope to the nearest 0.1 mm and fish lengths were calculated using regression formulae for sagittae (Härkönen , Emmrich & Duettmann , Gaye‐Siessegger ), chewing pads (Veldkamp , Emmrich & Duettmann ), and pharyngeal bones, jaws and praeopercula (Cech , Emmrich & Duettmann ).…”

Section: Methodsmentioning

confidence: 99%

Maximizing dietary information retrievable from carcasses of Great Cormorants Phalacrocorax carbo using a combined morphological and molecular analytical approach

Oehm

Thalinger

Mayr

et al. 2015

Ibis

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Avian carcasses can provide important information on the trophic ecology of birds. Usually, the number of carcasses available for examination is limited and therefore it is important to gain as much dietary information per specimen as possible. In piscivorous birds and raptors, the stomach has been the primary source of dietary information, whereas the gut (intestine) has so far been neglected as it usually contains only a few morphologically identifiable hard parts of prey. Molecular approaches have the potential to retrieve dietary information from the gut, although this has not yet been verified. As well as identifying the prey, it is important to estimate any secondary predation to avoid food web errors in dietary analyses. The assignment of accidentally consumed prey is notoriously difficult regardless of the prey identification approach used. In the present study, morphological and molecular analyses were, for the first time, combined to maximize the dietary information retrievable from the complete digestive tract of Great Cormorants Phalacrocorax carbo sinensis. Moreover, a novel approach based on predator–prey size ratios was applied to these piscivorous birds to minimize the number of samples that might contain secondarily predated prey. The stomach contents of the examined birds were found to provide the most dietary information when morphological and molecular analyses were used in combination. However, compared with the morphological approach, the molecular analysis increased the number of fish species detected by 39%. The molecular approach also permitted the identification of fish DNA in the Cormorant guts. Predator–prey size ratios derived from morphological analysis of fish hard parts can reduce the incidence of potential confounding influence of secondarily predated prey by 80%. Our findings demonstrate that a combination of morphological and molecular approaches maximizes the trophic information retrievable from bird carcasses.

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The great Cormorant (Phalacrocorax carbo) at lower lake Constance/Germany: dietary composition and impact on commercial fisheries

Cited by 7 publications

References 15 publications

Great cormorant (Phalacrocorax carbo) predation on pikeperch (Sander lucioperca L.) in shallow eutrophic lakes in Poland

Great cormorant (Phalacrocorax carbo) predation on pikeperch (Sander lucioperca L.) in shallow eutrophic lakes in Poland

Diet analysis in piscivorous birds: What can the addition of molecular tools offer?

Maximizing dietary information retrievable from carcasses of Great Cormorants Phalacrocorax carbo using a combined morphological and molecular analytical approach

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