Water transparency is an important factor affecting fish availability (underwater visibility) for diving birds. The diet of Great Cormorants Phalacrocorax carbo in relation to water transparency (range 1.4–4.0 m) was studied by pellet analyses at the submontane reservoir Dobczyce, Poland, from June to November. Although water transparency proved to be related to the birds' distribution, in the range of turbidities studied, no relationship was found with either fish species and fish size taken. Of 14 species in the diet, Roach Rutilus rutilus was dominant in all monthly samples (35–91% in 2002, 56–82% in 2004). Numbers of Great Cormorants and water transparency (range 0.4–1.4 m) were studied in the turbid lowland reservoir Goczałkowice during the migration period in autumn (August–November 2011 and 2012). Observations here suggest that the effect of water transparency on food uptake and habitat choice was only apparent below 0.6 m Secchi depth. The number of foraging Great Cormorants was not only affected by Secchi depth, but by a complex of factors (year, month, place, Secchi depth and water depth). We argue that, especially when the number of Great Cormorants is low, only highly detailed measurements of these factors (both spatially and as time series) can show the complex relationship between prey distribution, environmental conditions and the predator's behaviour.
{"title":"Studies of Food Ecology of Great Cormorant Phalacrocorax carbo in Relation to Water Transparency Require System-Adjusted Data: An Example from Two Polish Reservoirs","authors":"R. Gwiazda, A. Flis","doi":"10.5253/arde.v109i2.a21","DOIUrl":"https://doi.org/10.5253/arde.v109i2.a21","url":null,"abstract":"Water transparency is an important factor affecting fish availability (underwater visibility) for diving birds. The diet of Great Cormorants Phalacrocorax carbo in relation to water transparency (range 1.4–4.0 m) was studied by pellet analyses at the submontane reservoir Dobczyce, Poland, from June to November. Although water transparency proved to be related to the birds' distribution, in the range of turbidities studied, no relationship was found with either fish species and fish size taken. Of 14 species in the diet, Roach Rutilus rutilus was dominant in all monthly samples (35–91% in 2002, 56–82% in 2004). Numbers of Great Cormorants and water transparency (range 0.4–1.4 m) were studied in the turbid lowland reservoir Goczałkowice during the migration period in autumn (August–November 2011 and 2012). Observations here suggest that the effect of water transparency on food uptake and habitat choice was only apparent below 0.6 m Secchi depth. The number of foraging Great Cormorants was not only affected by Secchi depth, but by a complex of factors (year, month, place, Secchi depth and water depth). We argue that, especially when the number of Great Cormorants is low, only highly detailed measurements of these factors (both spatially and as time series) can show the complex relationship between prey distribution, environmental conditions and the predator's behaviour.","PeriodicalId":55463,"journal":{"name":"Ardea","volume":"109 1","pages":"529 - 536"},"PeriodicalIF":0.4,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45022014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Monthly aerial bird counts showed a strong increase in the number of wintering Great Cormorants Phalacrocorax carbo sinensis since the late 1990s at Lake IJsselmeer but not at Lake Markermeer-IJmeer. Compared to the 1980–1990s, breeding numbers also increased in this part of the system. The resulting increased exploitation of fish stocks was thought to have been possible because of a long-term increase in the stock of Ruffe Gymnocephalus cernuus, despite a clear overall decline of total estimated fish biomass in the lake during the same period. The most likely cause of these shifts was thought to be the intensive commercial fishing regime, removing the large predatory fish first, followed by a strong reduction of stocks of large Bream Abramis brama, in turn paving the way for increases in the stocks of Ruffe. Increased predation by Cormorants on the enhanced stocks of small fishes was possible because of ameliorated underwater visibility in Lake IJsselmeer. Starting in 2000, there was a strong shift in both temporal habitat use and associated fish consumption by Cormorants towards the winter period. The local breeding birds, exploiting the same age- and size-structured community of fishes in the spring, thus face an already-depleted food resource. Compared to the 1980–1990s, fish consumption by Cormorants in winter increased by a factor of ten, whereas that by breeders did so by a factor of 1.6. Our calculations showed that the actual harvest of available fish stock by wintering and breeding Cormorants together was c. 5% in 1985–2000 and c. 15% in 2001–2015. The disproportionate division of the overall consumption (‘harvest’) of the fish stock towards the wintering birds is a strong argument for direct competition with their conspecifics breeding locally. In conclusion, we calculate that because of the increased winter exploitation initiated by the activities of an intensive commercial fishery, the fish consumption in summer and early autumn by breeding Cormorants and their offspring was suppressed by a factor of six.
{"title":"Time Shift in the Exploitation of Fish Stocks by Great Cormorants Phalacrocorax carbo at Lake IJsselmeer: How Wintering Birds began Competing for Fish with Breeding Conspecifics","authors":"Mennobart R. van Eerden, Stef van Rijn","doi":"10.5253/arde.v109i2.a16","DOIUrl":"https://doi.org/10.5253/arde.v109i2.a16","url":null,"abstract":"Monthly aerial bird counts showed a strong increase in the number of wintering Great Cormorants Phalacrocorax carbo sinensis since the late 1990s at Lake IJsselmeer but not at Lake Markermeer-IJmeer. Compared to the 1980–1990s, breeding numbers also increased in this part of the system. The resulting increased exploitation of fish stocks was thought to have been possible because of a long-term increase in the stock of Ruffe Gymnocephalus cernuus, despite a clear overall decline of total estimated fish biomass in the lake during the same period. The most likely cause of these shifts was thought to be the intensive commercial fishing regime, removing the large predatory fish first, followed by a strong reduction of stocks of large Bream Abramis brama, in turn paving the way for increases in the stocks of Ruffe. Increased predation by Cormorants on the enhanced stocks of small fishes was possible because of ameliorated underwater visibility in Lake IJsselmeer. Starting in 2000, there was a strong shift in both temporal habitat use and associated fish consumption by Cormorants towards the winter period. The local breeding birds, exploiting the same age- and size-structured community of fishes in the spring, thus face an already-depleted food resource. Compared to the 1980–1990s, fish consumption by Cormorants in winter increased by a factor of ten, whereas that by breeders did so by a factor of 1.6. Our calculations showed that the actual harvest of available fish stock by wintering and breeding Cormorants together was c. 5% in 1985–2000 and c. 15% in 2001–2015. The disproportionate division of the overall consumption (‘harvest’) of the fish stock towards the wintering birds is a strong argument for direct competition with their conspecifics breeding locally. In conclusion, we calculate that because of the increased winter exploitation initiated by the activities of an intensive commercial fishery, the fish consumption in summer and early autumn by breeding Cormorants and their offspring was suppressed by a factor of six.","PeriodicalId":55463,"journal":{"name":"Ardea","volume":"109 1","pages":"457 - 470"},"PeriodicalIF":0.4,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45040380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mennobart R. van Eerden, R. Parz-Gollner, L. Marion, T. Bregnballe, J. Paquet, S. Volponi, Stef van Rijn, D. Carss
Great Cormorants were censused on a pan-European level in January 2013. Cormorants were found in an enormous winter range, spanning from the Baltic Sea and Atlantic Ocean in the north to the Mediterranean and coasts of North Africa. This large-scale exercise in which more than 5000 volunteers took part resulted in a total of 641,650 Cormorants counted (630,000–672,000 estimated). Based on the breeding census data of 2012 we estimated a total number of birds in January 2013 of slightly over 1 million, including the birds from the Ukrainian and Russian parts of Black Sea, Sea of Azov and north-western Caspian. Using the summer counts to produce a corrected estimate for the area that was actually covered during the winter count gave an estimated 695,000 individuals for January 2013. Total coverage was considered good and comparison to the previously conducted winter count of 2003 revealed, corrected for coverage, a 15% increase. As both counts were carried out during a period of cold weather, it is unlikely that birds were missed due to movements to the east and north-east of the range, from or into areas that are difficult to assess. Some 33% of all Cormorants were found to occur in areas with a temperature of –5°C or lower, suggesting that many birds can survive under conditions that may be marginal, i.e. at a high risk and/or cost. Compared to the previous count a relatively lower number of Cormorants were found under low temperature conditions, –5 °C down to –10°C, coinciding with the moment of active ice formation of shallow and stagnant freshwaters. It may well be that the actual ice cover in 2013 was such that birds had to leave these areas. In contrast to the opinion that wintering under low temperatures is marginal, it is possible that these northerly wintering grounds are more rewarding in terms of food profitability. This is because cold-blooded fishes congregate at certain spots and are less mobile at low temperatures and thus relatively easy to catch. Given the current and previous work carried out we recommend a long-term monitoring of these processes, which operate at a huge geographic scale. A repeated pan-European count with intervals of about ten years could detect the major patterns, while also providing a useful method of monitoring changes due to the expected further warming of winter conditions.
{"title":"Numbers of Great Cormorants Phalacrocorax carbo Wintering in the Western Palaearctic in January 2013","authors":"Mennobart R. van Eerden, R. Parz-Gollner, L. Marion, T. Bregnballe, J. Paquet, S. Volponi, Stef van Rijn, D. Carss","doi":"10.5253/arde.v109i2.a2","DOIUrl":"https://doi.org/10.5253/arde.v109i2.a2","url":null,"abstract":"Great Cormorants were censused on a pan-European level in January 2013. Cormorants were found in an enormous winter range, spanning from the Baltic Sea and Atlantic Ocean in the north to the Mediterranean and coasts of North Africa. This large-scale exercise in which more than 5000 volunteers took part resulted in a total of 641,650 Cormorants counted (630,000–672,000 estimated). Based on the breeding census data of 2012 we estimated a total number of birds in January 2013 of slightly over 1 million, including the birds from the Ukrainian and Russian parts of Black Sea, Sea of Azov and north-western Caspian. Using the summer counts to produce a corrected estimate for the area that was actually covered during the winter count gave an estimated 695,000 individuals for January 2013. Total coverage was considered good and comparison to the previously conducted winter count of 2003 revealed, corrected for coverage, a 15% increase. As both counts were carried out during a period of cold weather, it is unlikely that birds were missed due to movements to the east and north-east of the range, from or into areas that are difficult to assess. Some 33% of all Cormorants were found to occur in areas with a temperature of –5°C or lower, suggesting that many birds can survive under conditions that may be marginal, i.e. at a high risk and/or cost. Compared to the previous count a relatively lower number of Cormorants were found under low temperature conditions, –5 °C down to –10°C, coinciding with the moment of active ice formation of shallow and stagnant freshwaters. It may well be that the actual ice cover in 2013 was such that birds had to leave these areas. In contrast to the opinion that wintering under low temperatures is marginal, it is possible that these northerly wintering grounds are more rewarding in terms of food profitability. This is because cold-blooded fishes congregate at certain spots and are less mobile at low temperatures and thus relatively easy to catch. Given the current and previous work carried out we recommend a long-term monitoring of these processes, which operate at a huge geographic scale. A repeated pan-European count with intervals of about ten years could detect the major patterns, while also providing a useful method of monitoring changes due to the expected further warming of winter conditions.","PeriodicalId":55463,"journal":{"name":"Ardea","volume":"109 1","pages":"271 - 284"},"PeriodicalIF":0.4,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41390205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study is based on recoveries of c. 86,850 Great Cormorants ringed in the Russian Federation during 1939–2014. Data were obtained from the Bird Ringing Centre of Russia. During 1939 to 2014 a total of 1667 Cormorant recoveries (1.9%) were added to the ringing database. The majority of the recoveries were made in the Caspian Sea, Azov Sea, Black Sea, Baltic Sea and in Kazakhstan inland waterbodies, including the Aral Sea (seven recoveries), Lake Alakol (46), Lake Balkhash (28), Kapchagay Reservoir (10) and Lake Zaysan (5). Non-breeding birds (assuming breeding at age > 3 years) comprised 89% of ring recoveries from 1939 to 1974, 95% from 1975 to 1990 and 100% from 1991 to 2014. This study is the first to describe the migration patterns for this species on a continental scale. From Kaliningrad in the west to Vladivostok in the east seven mega clusters of waterbodies and wetlands exist where Cormorants breed and were ringed. Although showing some overlap, birds belonging to a certain cluster were recovered in distinct wintering areas, often more than 2000 km from the breeding areas and separated by high mountain ranges. The general migration pattern is discussed for four geographic regions. The occurrence of east–west migration patterns is briefly discussed and deserves further study as well as the role of high mountain ridges possibly shaping the movements between summer and winter areas.
{"title":"Analysis of the Recovery Data of the Great Cormorant Phalacrocorax carbo Ringed in the Russian Federation and on the Territory of Former Soviet States in 1939–2014","authors":"Ch. Chaika","doi":"10.5253/arde.v109i2.a3","DOIUrl":"https://doi.org/10.5253/arde.v109i2.a3","url":null,"abstract":"This study is based on recoveries of c. 86,850 Great Cormorants ringed in the Russian Federation during 1939–2014. Data were obtained from the Bird Ringing Centre of Russia. During 1939 to 2014 a total of 1667 Cormorant recoveries (1.9%) were added to the ringing database. The majority of the recoveries were made in the Caspian Sea, Azov Sea, Black Sea, Baltic Sea and in Kazakhstan inland waterbodies, including the Aral Sea (seven recoveries), Lake Alakol (46), Lake Balkhash (28), Kapchagay Reservoir (10) and Lake Zaysan (5). Non-breeding birds (assuming breeding at age > 3 years) comprised 89% of ring recoveries from 1939 to 1974, 95% from 1975 to 1990 and 100% from 1991 to 2014. This study is the first to describe the migration patterns for this species on a continental scale. From Kaliningrad in the west to Vladivostok in the east seven mega clusters of waterbodies and wetlands exist where Cormorants breed and were ringed. Although showing some overlap, birds belonging to a certain cluster were recovered in distinct wintering areas, often more than 2000 km from the breeding areas and separated by high mountain ranges. The general migration pattern is discussed for four geographic regions. The occurrence of east–west migration patterns is briefly discussed and deserves further study as well as the role of high mountain ridges possibly shaping the movements between summer and winter areas.","PeriodicalId":55463,"journal":{"name":"Ardea","volume":"109 1","pages":"285 - 297"},"PeriodicalIF":0.4,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49149103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Great Cormorant Phalacrocorax carbo is a widespread piscivorous waterbird. The competition for resources between recreational anglers and Cormorants has been causing serious conflicts between sport fisheries and environmentalists. This study aimed to compare fish catches by Cormorants and by recreational anglers in the upper Elbe River in Central Europe (Czech Republic). Cormorant diet was studied using regurgitated pellets, and catches of anglers were obtained from annual angling reports. Altogether 1478 Cormorant pellets were collected from which 6903 fish were measured and identified to species level. A total of 93,413 fish caught by anglers were identified to species level. Cormorant diet consisted of 24 fish species in six fish families. Cormorants caught smaller-sized fish (median mass 90 g) compared to fish caught by anglers (median mass 1700 g). The majority of fish caught by Cormorants were under the minimum legal catchable size for anglers. Species of moderate interest to anglers (mainly Roach Rutilus rutilus) dominated in Cormorant diets while Common Carp Cyprinus carpio dominated in catches of anglers. In conclusion, the direct competition for fish between anglers and Cormorants appeared low. However, as Cormorants consumed small fish that serve as prey for piscivorous fish species and that could potentially grow into legally sized fish for angling purposes, this still allows for indirect competition between Cormorants and sport fisheries.
{"title":"Do Cormorants and Recreational Anglers Take Fish of the Same Species and Sizes?","authors":"Roman Lyach","doi":"10.5253/arde.v109i2.a28","DOIUrl":"https://doi.org/10.5253/arde.v109i2.a28","url":null,"abstract":"The Great Cormorant Phalacrocorax carbo is a widespread piscivorous waterbird. The competition for resources between recreational anglers and Cormorants has been causing serious conflicts between sport fisheries and environmentalists. This study aimed to compare fish catches by Cormorants and by recreational anglers in the upper Elbe River in Central Europe (Czech Republic). Cormorant diet was studied using regurgitated pellets, and catches of anglers were obtained from annual angling reports. Altogether 1478 Cormorant pellets were collected from which 6903 fish were measured and identified to species level. A total of 93,413 fish caught by anglers were identified to species level. Cormorant diet consisted of 24 fish species in six fish families. Cormorants caught smaller-sized fish (median mass 90 g) compared to fish caught by anglers (median mass 1700 g). The majority of fish caught by Cormorants were under the minimum legal catchable size for anglers. Species of moderate interest to anglers (mainly Roach Rutilus rutilus) dominated in Cormorant diets while Common Carp Cyprinus carpio dominated in catches of anglers. In conclusion, the direct competition for fish between anglers and Cormorants appeared low. However, as Cormorants consumed small fish that serve as prey for piscivorous fish species and that could potentially grow into legally sized fish for angling purposes, this still allows for indirect competition between Cormorants and sport fisheries.","PeriodicalId":55463,"journal":{"name":"Ardea","volume":"109 1","pages":"629 - 638"},"PeriodicalIF":0.4,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44375626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Kazantzidis, T. Naziridis, G. Catsadorakis, Haris Nikolaou, E. Makrigianni
We analysed trends in the breeding population of Great Cormorants in Greece during the period 1988–2014 when at least 20 colonies were recorded. The number of colonies doubled over the study period reaching 14 in 2014 from seven in 1988. There was also a continuous increase in the number of nests: from 952 in 1988 to 9256 in 2014, presenting an annual change of +26.5% ± 0.05 (SD). Most of the colonies were situated in freshwater lakes, three in deltas and one on the seacoast. Nine colonies were mixed with other colonially nesting species (mostly from the Ardeidae family). Of the 14 colonies 11 were found in trees. Two colonies were situated on the ground, four in bushes, two on reed rhizome islets and one on cliff ledges. Five out of the 14 active colonies in 2014, comprising 87% of the total recorded nests, were in wetlands of low altitude (0–45 m a.s.l.). The rest were situated in mountainous wetlands at altitudes ranging from 235 to 853 m a.s.l. One colony, at Lake Kerkini, contained the majority of nests in Greece (6650, being 72% in 2014). The second largest colony, at Lake Volvi, had 900 nests, followed by the Greek part of Prespa with 625 nests (in three colonies) in 2014. The percentage of nests in newly established colonies increased after 2003, reaching its highest value (14%) in 2009. The reason for the growth in both colonies and nests over the years is attributed to the increasing availability of fish, the protection status of wetlands and the absence of disturbance. Particularly after 2002 the species increased in numbers and established colonies in new areas, which is probably related to the expanding breeding populations of the species in north-eastern European countries and a corresponding increase in wintering numbers in Greece. This needs further attention by monitoring and research.
{"title":"Status and Population Trends of Great Cormorant Phalacrocorax carbo sinensis Breeding in Greece","authors":"S. Kazantzidis, T. Naziridis, G. Catsadorakis, Haris Nikolaou, E. Makrigianni","doi":"10.5253/arde.v109i2.a9","DOIUrl":"https://doi.org/10.5253/arde.v109i2.a9","url":null,"abstract":"We analysed trends in the breeding population of Great Cormorants in Greece during the period 1988–2014 when at least 20 colonies were recorded. The number of colonies doubled over the study period reaching 14 in 2014 from seven in 1988. There was also a continuous increase in the number of nests: from 952 in 1988 to 9256 in 2014, presenting an annual change of +26.5% ± 0.05 (SD). Most of the colonies were situated in freshwater lakes, three in deltas and one on the seacoast. Nine colonies were mixed with other colonially nesting species (mostly from the Ardeidae family). Of the 14 colonies 11 were found in trees. Two colonies were situated on the ground, four in bushes, two on reed rhizome islets and one on cliff ledges. Five out of the 14 active colonies in 2014, comprising 87% of the total recorded nests, were in wetlands of low altitude (0–45 m a.s.l.). The rest were situated in mountainous wetlands at altitudes ranging from 235 to 853 m a.s.l. One colony, at Lake Kerkini, contained the majority of nests in Greece (6650, being 72% in 2014). The second largest colony, at Lake Volvi, had 900 nests, followed by the Greek part of Prespa with 625 nests (in three colonies) in 2014. The percentage of nests in newly established colonies increased after 2003, reaching its highest value (14%) in 2009. The reason for the growth in both colonies and nests over the years is attributed to the increasing availability of fish, the protection status of wetlands and the absence of disturbance. Particularly after 2002 the species increased in numbers and established colonies in new areas, which is probably related to the expanding breeding populations of the species in north-eastern European countries and a corresponding increase in wintering numbers in Greece. This needs further attention by monitoring and research.","PeriodicalId":55463,"journal":{"name":"Ardea","volume":"109 1","pages":"367 - 380"},"PeriodicalIF":0.4,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46236253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The feeding ecology of the Great Cormorant Phalacrocorax carbo has been the subject of many studies in which the hard parts of fish, contained in dietary samples such as regurgitated pellets, were identified using morphological characteristics. However, morphological prey identification does not necessarily permit the reliable identification of all fish species due to digestion eroding diagnostic characters and/or morphologically indiscernible hard parts in a range of fish species. Molecular methods have the potential to overcome these obstacles by allowing the detection and identification of minute quantities of prey DNA present in pellets, faeces, and stomach samples. Moreover, DNA of the consumer (i.e. the Cormorant) is also present in dietary samples and can thus be employed for ecological studies too. Here, we present a methodological overview of two molecular approaches commonly used to study trophic interactions, namely diagnostic PCR and next generation sequencing, along with their main advantages and disadvantages. Regarding the use of consumer DNA contained in dietary samples, molecular sexing, i.e. the non-invasive sex determination of the sample-producing bird, is presented. We exemplify the potential of DNA-based methods for future research via a case study on pellets collected at Chiemsee (Germany), which were subjected to molecular and morphological prey identification as well as to molecular sexing. Compared to morphological prey identification, molecular analysis led to a 53% increase in prey species and genera, mainly caused by eight additionally detected cyprinid taxa. For 79% of the pellets, the sex of the pellet-producing Cormorant could be successfully determined via molecular sexing. Our findings highlight the exciting possibilities molecular methods offer for future studies on Cormorant feeding ecology, especially regarding evaluations of prey spectra and the non-invasive assessment of sex-specific differences.
{"title":"Molecular Methods to Study Great Cormorant Feeding Ecology","authors":"B. Thalinger, Johannes Oehm, M. Traugott","doi":"10.5253/arde.v109i2.a22","DOIUrl":"https://doi.org/10.5253/arde.v109i2.a22","url":null,"abstract":"The feeding ecology of the Great Cormorant Phalacrocorax carbo has been the subject of many studies in which the hard parts of fish, contained in dietary samples such as regurgitated pellets, were identified using morphological characteristics. However, morphological prey identification does not necessarily permit the reliable identification of all fish species due to digestion eroding diagnostic characters and/or morphologically indiscernible hard parts in a range of fish species. Molecular methods have the potential to overcome these obstacles by allowing the detection and identification of minute quantities of prey DNA present in pellets, faeces, and stomach samples. Moreover, DNA of the consumer (i.e. the Cormorant) is also present in dietary samples and can thus be employed for ecological studies too. Here, we present a methodological overview of two molecular approaches commonly used to study trophic interactions, namely diagnostic PCR and next generation sequencing, along with their main advantages and disadvantages. Regarding the use of consumer DNA contained in dietary samples, molecular sexing, i.e. the non-invasive sex determination of the sample-producing bird, is presented. We exemplify the potential of DNA-based methods for future research via a case study on pellets collected at Chiemsee (Germany), which were subjected to molecular and morphological prey identification as well as to molecular sexing. Compared to morphological prey identification, molecular analysis led to a 53% increase in prey species and genera, mainly caused by eight additionally detected cyprinid taxa. For 79% of the pellets, the sex of the pellet-producing Cormorant could be successfully determined via molecular sexing. Our findings highlight the exciting possibilities molecular methods offer for future studies on Cormorant feeding ecology, especially regarding evaluations of prey spectra and the non-invasive assessment of sex-specific differences.","PeriodicalId":55463,"journal":{"name":"Ardea","volume":"109 1","pages":"537 - 547"},"PeriodicalIF":0.4,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46843217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
bution, numbers and foraging activities, this special issue of Ardea highlights some of the latest research findings, but also reflects on the ongoing debate about how we need to see the perceived conflict with fisheries and angling interests that has kept us busy for so long. By bringing together this diverse collection of papers from all over Europe and Israel we are convinced that this will not only lead to a better understanding of the species but will also be of help in addressing the questions around this conflict that still remain. The species is fascinating in its flexibility to respond to changes in environmental conditions. It is perhaps that flexibility, that ever-existing power of Cormorants to find a way out when conditions change, that has attracted the attention of researchers for so many years and, at the same time, has made the birds so thoroughly hated by many who have vested interests in fisheries. Interest ingly, during the same period the Double-crested Cormorant Phalacrocorax auritus has raised the same questions in the United States and Canada and has been subject to rigorous control measures (e.g. Wires 2014). Rather than demonising Cormorants for their predation on fishes, perhaps we can learn a lot from their way of fishing, from the way that they, unlike many human users in the same habitats, have never been shown to over-exploit healthy, natural systems.
{"title":"Sailing Down-Wind, a Breakwaters' Perspective on the Great Cormorant","authors":"","doi":"10.5253/arde.v109i2.a1","DOIUrl":"https://doi.org/10.5253/arde.v109i2.a1","url":null,"abstract":"bution, numbers and foraging activities, this special issue of Ardea highlights some of the latest research findings, but also reflects on the ongoing debate about how we need to see the perceived conflict with fisheries and angling interests that has kept us busy for so long. By bringing together this diverse collection of papers from all over Europe and Israel we are convinced that this will not only lead to a better understanding of the species but will also be of help in addressing the questions around this conflict that still remain. The species is fascinating in its flexibility to respond to changes in environmental conditions. It is perhaps that flexibility, that ever-existing power of Cormorants to find a way out when conditions change, that has attracted the attention of researchers for so many years and, at the same time, has made the birds so thoroughly hated by many who have vested interests in fisheries. Interest ingly, during the same period the Double-crested Cormorant Phalacrocorax auritus has raised the same questions in the United States and Canada and has been subject to rigorous control measures (e.g. Wires 2014). Rather than demonising Cormorants for their predation on fishes, perhaps we can learn a lot from their way of fishing, from the way that they, unlike many human users in the same habitats, have never been shown to over-exploit healthy, natural systems.","PeriodicalId":55463,"journal":{"name":"Ardea","volume":"109 1","pages":"265 - 269"},"PeriodicalIF":0.4,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49385882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Fijn, Job W. de Jong, J. Adema, P. V. van Horssen, M. Poot, Stef van Rijn, Mennobart R. van Eerden, T. Boudewijn
Great Cormorants Phalacrocorax carbo sinensis are considered generalist predators feeding in a variety of marine and freshwater habitats on many different prey species. Recently however, there is increasing evidence that even seemingly generalist species can often be regarded as a diverse group of individual specialists sometimes induced by sex-specific foraging behaviour. To test whether this also holds true for Great Cormorants, the present study characterised the at-sea distribution and examined the time budgets of provisioning Great Cormorants by deploying GPS-loggers on 11 nesting males and females during the breeding season of 2012. Additionally, pellets were collected from underneath the nests of these tagged birds for detailed diet analysis, based on the otoliths and fish bones recorded within them. Diverse foraging patterns were recorded, ranging from exclusively freshwater feeding, to offshore foraging, with the furthest recorded distance from the colony being 28 km at sea. Time budgets during foraging trips revealed relatively long periods of resting ashore (55% of the trip ± 23%), followed by foraging (31 ± 18%), and time spent in flight (15 ± 11%). Flatfishes dominated in the diets of these Great Cormorants, indicating benthic-foraging strategies when foraging in saltwater (feeding on discards could be ruled out). The males in this study avoided freshwater foraging habitat and preferred offshore waters with a sandy bottom or nearshore waters alongside rocky breakwaters and within harbours. Females foraged in all habitat types, but proportionally more in inland freshwater bodies. Females spent more time on foraging than did males, particularly in marine habitats, whilst males rested more. It is proposed that these differences might have been caused by sex-specific foraging strategies, possibly resulting from competition at foraging sites.
{"title":"GPS-Tracking of Great Cormorants Phalacrocorax carbo sinensis Reveals Sex-Specific Differences in Foraging Behaviour","authors":"R. Fijn, Job W. de Jong, J. Adema, P. V. van Horssen, M. Poot, Stef van Rijn, Mennobart R. van Eerden, T. Boudewijn","doi":"10.5253/arde.v109i2.a19","DOIUrl":"https://doi.org/10.5253/arde.v109i2.a19","url":null,"abstract":"Great Cormorants Phalacrocorax carbo sinensis are considered generalist predators feeding in a variety of marine and freshwater habitats on many different prey species. Recently however, there is increasing evidence that even seemingly generalist species can often be regarded as a diverse group of individual specialists sometimes induced by sex-specific foraging behaviour. To test whether this also holds true for Great Cormorants, the present study characterised the at-sea distribution and examined the time budgets of provisioning Great Cormorants by deploying GPS-loggers on 11 nesting males and females during the breeding season of 2012. Additionally, pellets were collected from underneath the nests of these tagged birds for detailed diet analysis, based on the otoliths and fish bones recorded within them. Diverse foraging patterns were recorded, ranging from exclusively freshwater feeding, to offshore foraging, with the furthest recorded distance from the colony being 28 km at sea. Time budgets during foraging trips revealed relatively long periods of resting ashore (55% of the trip ± 23%), followed by foraging (31 ± 18%), and time spent in flight (15 ± 11%). Flatfishes dominated in the diets of these Great Cormorants, indicating benthic-foraging strategies when foraging in saltwater (feeding on discards could be ruled out). The males in this study avoided freshwater foraging habitat and preferred offshore waters with a sandy bottom or nearshore waters alongside rocky breakwaters and within harbours. Females foraged in all habitat types, but proportionally more in inland freshwater bodies. Females spent more time on foraging than did males, particularly in marine habitats, whilst males rested more. It is proposed that these differences might have been caused by sex-specific foraging strategies, possibly resulting from competition at foraging sites.","PeriodicalId":55463,"journal":{"name":"Ardea","volume":"919 ","pages":"491 - 505"},"PeriodicalIF":0.4,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41271747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The necessity of balancing conservation issues with the protection of aquaculture activities drives research to quantify the impact of the Great Cormorant Phalacrocorax carbo and to identify the best mitigation strategies. This study aims to characterise the diet in relation to the possible impact of the Great Cormorant on the extensive aquaculture farms in Friuli Venezia Giulia region in the upper Adriatic Sea. The diet of the species was investigated by analysing 459 pellets, collected monthly during the winter 2006/2007 in the three most important roosts of the Friuli Venezia Giulia coastline. Cormorants proved to feed mainly on typical fish species of lagoon and coastal waters. By frequency, Sand Smelts Atherina boyeri (54%) and Flounders Platichthys flesus (26%) were the main prey. Flounders played an important role also in terms of biomass (35%), together with mullets (Mugilidae, 28%). Commercially-important aquaculture species (European Seabass Dicentrarchus labrax and Gilthead Bream Sparus aurata) represented only 2% and 14% by frequency and biomass. The diet analysis supports our previous studies, carried out by behavioural observations on Cormorants foraging at different depths, on interactions with the main prey and strategies of exploitation of the fish farms. Our data imply that the Great Cormorant does not have a large effect on aquaculture yield in the north Adriatic Sea.
{"title":"Diet of Great Cormorants Phalacrocorax carbo in Relation to Fish Resources in the Upper Adriatic Sea","authors":"M. Cosolo, N. Privileggi, S. Sponza","doi":"10.5253/arde.v109i2.a18","DOIUrl":"https://doi.org/10.5253/arde.v109i2.a18","url":null,"abstract":"The necessity of balancing conservation issues with the protection of aquaculture activities drives research to quantify the impact of the Great Cormorant Phalacrocorax carbo and to identify the best mitigation strategies. This study aims to characterise the diet in relation to the possible impact of the Great Cormorant on the extensive aquaculture farms in Friuli Venezia Giulia region in the upper Adriatic Sea. The diet of the species was investigated by analysing 459 pellets, collected monthly during the winter 2006/2007 in the three most important roosts of the Friuli Venezia Giulia coastline. Cormorants proved to feed mainly on typical fish species of lagoon and coastal waters. By frequency, Sand Smelts Atherina boyeri (54%) and Flounders Platichthys flesus (26%) were the main prey. Flounders played an important role also in terms of biomass (35%), together with mullets (Mugilidae, 28%). Commercially-important aquaculture species (European Seabass Dicentrarchus labrax and Gilthead Bream Sparus aurata) represented only 2% and 14% by frequency and biomass. The diet analysis supports our previous studies, carried out by behavioural observations on Cormorants foraging at different depths, on interactions with the main prey and strategies of exploitation of the fish farms. Our data imply that the Great Cormorant does not have a large effect on aquaculture yield in the north Adriatic Sea.","PeriodicalId":55463,"journal":{"name":"Ardea","volume":"109 1","pages":"481 - 490"},"PeriodicalIF":0.4,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45816222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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