PRELIMINARY RESULTS ON THE WINTERING POPULATION AND DIET OF THE GREAT CORMORANT PHALACROCORAX CARBO SINENSIS AT A GREEK COASTAL WETLAND SAVAS KAZANTZIDIS1, MARIA PANAGIOTOPOULOU2, ARIS CHRISTIDIS2, EFTERPI PATETSINI2, STEFAN DONTH2, VASSILIS TERZIS2, ANASTASSIA MICHAILIDOU2, VASSILIS KATSOULIS2, NAPOLEON PIAKIS2, KASSIANI MINASIDOU2 AND EVANTHIA CHARTZOULAKI2 Results
Introduction In Greece, the National Park of Eastern Macedonia and Thrace is one of the most important wetlands
Great Cormorant wintering population
regarding the wintering of Great Cormorants. The National Park has also great importance for fisheries
Great Cormorants numbers ranged from 1550 to 12078 individuals (Fig. 1). The highest numbers were X
recorded in early November 2013 but high numbers (more than 10000) were present in the area up to
X
January 2014. These were the highest numbers of Great Cormorant ever recorded wintering in a Greek
that are developed at the coastal lagoons in a traditional way. The recent growth of the wintering population of the Great Cormorant Phalacrocorax carbo sinensis caused concern among fishermen of the
wetland. Great Cormorants wintering in the National Park roost every night in three sites: a) a rocky islet
X
National Park regarding the impact of this species on fisheries. In response, fishermen placed nets above X
certain fish wintering channels and used several Great Cormorant deterrent methods including gas
(Aghios Christoforos) at the southeastern part of the Park, b) on trees at the estuary of Kompsatos River at the northeastern part of Vistonis Lake (this roosting site was active up to November 2013) and c) on
cannons and shooting (although illegal). Disturbance of protected bird species as the result of shooting against Great Cormorants is considered a problem for the Management authority of the National Park. So,
Map 1. Map of the study area. Night roosting sites
initiated a research project in order to record the potential impact of Great Cormorants to fisheries and to
of Great Cormorants are indicated with X and
suggest the best solution for both, fisheries and wildlife.
their main feeding areas with black bullets.
trees at the Nestos River estuary at the southwestern part of the Park (that was active after December 2013). A smaller roosting site (40-100 individuals) was at Porto Lagos lagoon (Map 1). 14000
The aim of the study is to record: a) the number of the Great Cormorants wintering in the
12078
Number of Great Cormorants
12000
National Park, b) the distribution in the feeding areas, c) the diet of the Great Cormorant. A technique for the protection of fish in the wintering channels from bird predation will be applied experimentally in collaboration with the fishermen associations.
1
Photo 1. Night roosting site of Great Cormorants
Study area The National Park consists of 5 rivers, 17 lagoons and 8 freshwater lakes. That wetland complex is one of
7093
8000
4820
6000 4000 2000
1550
I Oct
I Oct
II Oct
I Nov
II Nov
II Dec
I Jan
2013
scientific and educational value. The wetland is included in the list of the protected wetlands under
Nestos River
Ramsar Convention and the NATURA 2000 network. Fishery is one of the most important human activities
5172
3820
0
3
10340
9350
10000
at Aghios Christoforos rocky islet.
the most important of Greece due to its great extent (930.000 ha) and the great biological, aesthetic,
10780
II Jan
I Feb
II Feb
2014
Porto Lagos lagoon
Kompsatos River estuary
Ag. Christoforos
Figure 1. Number changes of Great Cormorants at the National Park of the eastern Macedonia and Thrace
within the National Park and there are 8 Fishing Associations that employ more than 100 people.
during the winter 2013-2014. The colors in each bar represent the number of Great Cormorants at the
Methods
different night roosting sites. 2
Great Cormorant wintering population The number of wintering Great Cormorants was recorded at their night roosting sites in early morning (before the departure of birds to the feeding grounds) or in the afternoon (from 3 or 4 o’clock until dark)
Photos 2 & 3. Great
Distribution of Great Cormorants to the feeding grounds
Cormorant pellets.
Great Cormorants used the coastal lagoons (including Vistonis Lake) for food in a percentage of 99.5%. They especially exploited Vistonis Lake and Porto Lagos Lagoon (Map 1) where they usually forage in
when birds return from the feeding grounds to overnight. Counts at all (two or three) roosting sites were
collaboration with Dalmatian pelican Pelecanus crispus. A very small number of Great Cormorants
4
carried out simultaneously, once to three times per month from October 2013 until February 2014.
exploited the rest of the coastal lagoons, seacoast and freshwater lakes and only sporadically large
Distribution of Great Cormorants to the feeding grounds
numbers were recorded there.
In order to record the main feeding areas of Great Cormorants, surveys were carried out in all lakes and
Diet
lagoons once or twice per month during the wintering period (October 2013 – Marsh 2014). As main
In 72 pellets collected from two different sites, 547 remains of fish (mostly otoliths) were recorded
feeding areas were considered those used by Great Cormorants directly after their departure from the
belonging to at least 303 fish of at least 13 species (Figure 2). The most abundant species was Boyer’s
night roosting sites. The diet Was studied by analyzing pellets collected once a month (from November 2013 to January 2014) from day roosting sites.
Photos 4 & 5. The main feeding area of Great
Sand Smelt Atherina boyeri (22.1% by number) followed by Golden Grey Mullet Liza aurata (19.8%) and
Cormorants at the Eastern Macedonia and Thrace
unidentified species of Mugilidae family (14.5%). Golden Grey Mullet dominated in pellets by frequency
National Park, Vistonis Lake (4) and Porto Lagos
of occurrence (present in 32 pellets or in 44.4% of pellets) followed by Thin-lipped Grey Mullet Liza
lagoon (5).
ramada (40.3%). Great Cormorants consumed low percentage (8.6%) of high commercial value fish
5
(European Seabass Dicentrarchus labrax, Flathead Grey Mullet Mugil cephalus and Sharpsnout Seabream Diplodus puntazzo) while they consumed high percentage (54.5%) of medium commercial value fish (Mugilidae and Liza sp.). The number of fish in each pellet ranged from 1 to 36 (mean number of fish: 4.0±5.0). The number of fish species in each pellet ranged from 1 to 6 (mean number of fish species: 2.3 ± 1.3).
7
6
Photos 6, 7 & 8. Scarecrows and nets placed above fish wintering channels are the main methods used by fishermen at the Eastern Macedonia and Thrace National Park to protect their fish yield by Great Cormorants predation.
Syngnathus sp. 0.7%
8
Engraulis encrasicholus 1.0%
Gobiidae sp. 2.3%
Gobio niger 5.9%
Dicentrarchus labrax 1,6%
Discussion The number of wintering Great Cormorants in the National Park in 2013-2014 increased considerably in relation to previous years.
Mugil cephalus 4.6%
During the last 10 years their number varied from 1000 to 5000 individuals while in January 2013 at least 2430 birds in two roosting sites were recorded. However, the distribution of Great Cormorants was not uniform in the National Park as they were feeding mostly in two sites. The diet of Great Cormorants was based upon fish species of low or medium economic importance.
Atherina boyerii 22.1%
Figure 2. Diet composition (by numbers of fish, in %) of Great
The high commercial value fish represented a small amount in the diet. Further research on the diet of Great Cormorant including
Cormorants wintering at the
larger pellet sample and stomach analysis is required, as well as, data on fish stock and yield, in order to estimate the impact of
National
Great Cormorants to fisheries. However, due to unexpected high numbers of Great Cormorants during the wintering period 2013-
Macedonia and Thrace in 2013-
2014 the impact to fisheries may be locally serious. Although the cover of the main fish wintering channels with nets is considered
2014 based on the content of 72
a successful method to keep Great Cormorants away, an additional fish protection technique might be helpful to fishermen in
pellets collected in day roosting
sites with high numbers of Great Cormorants where nets is impossible to be placed.
Diplodus puntazzo 2.3%
Park
of
Eastern
sites. The total number of fish recorded in pellets was 303.
Chelon labrosus 5.6% Liza ramada 11.9%
.Mugilidae sp. 14.5% Liza aurata 19.8%
Liza saliens 7.7%
Acknowledgements We would like to acknowledge the staff of the Management Authority of the National Park (Despina Michailidou, Theodoros Berberidis, Pashalio Zlatini, Konstantina Katsouli and Georgia Chatziefraimidou) for providing us various field facilities. We would also like to thank the fishermen of the National Park and especially these of Porto Lagos Association for the information on fish and fishery in the lagoons of the Park and the help in the field. The research was funded by the Management Authority of the Eastern Macedonia and Thrace National Park.
MANAGEMENT AUTHORITY OF EASTERN MACEDONIA AND THRACE NATIONAL PARK
FOREST RESEARCH INSTITUTE 1 Forest Research Institute, GR 57 006 Vassilika, Greece, E-mail:
[email protected], 2 Management authority of the Eastern Macedonia and Thrace National Park, GR 67063 Porto Lagos, Xanthi, Greece
