With its original geomorphological features and three (Caucasus, Irano-Anatolian and Mediterranean) of the 34 hot spots on Earth, Turkey is considered a unique country on the international scene (Şekercioğlu et al. 2011). In addition, this geographical area provides a natural passage for species to spread (Özuluğ et al. 2013), with very rich freshwater fauna in terms of diversity and endemism. There are 368 fish species in freshwaters of the country, 153 (41.8%) of which are known as endemic (Çiçek et al. 2015). A total of 25 invasive and potentially invasive freshwater species have been reported there, including
Lake Marmara is one of the very important natural lakes in Turkey with fishing activities and richness of endemic species. A total of 20 fish species occur in Lake Marmara (İlhan & Sarı 2013), most of which are cyprinid species; five of them are known as endemic species in Turkish freshwaters (İzmir minnow
Lake Marmara is a habitat for approximately 144 different bird species (Gül 2008), which makes it a matchless wetland. The lake has been hypertrophied as a result of eutrophication caused by the accumulation of agricultural fertilizers and pesticides (Gülersoy 2013).
Gibel carp
The species was first recorded in the Thrace region of Turkey in 1988 (Baran & Ongan 1988) and in Anatolian freshwaters (Lake Marmara) in 1991 by Balık et al. (İlhan et al. 2005). At present,
Known globally as a highly invasive species,
The main reason for such an increase in the spread of the carp is that it has been introduced into water resources for various purposes. It is difficult to distinguish fingerlings of the species from those of others, because they are so similar to each other that they can easily be confused with
Several aspects of the species
Length–weight relationships are crucial for a wide range of studies, such as presenting growth rates and establishing the age structure and many other population parameters. Moreover, length–weight relationships help compare populations of the same species living in different habitats (Sangun et al. 2007). The results of applying Fulton’s condition factor for species would enable the standard of research to be established and would also contribute to the management of invasive fish stocks. Populations of invasive species inhabiting important fishing areas should be regularly monitored based on the above mentioned studies.
Lake Marmara, 12 km long and 6 km wide, is located 75 m above sea level. The area of the lake is 4500 ha and the average depth is approximately 5 m (Ustaoğlu 1993). This alluvial lake is an extension of the Gediz River between the towns of Gölmarmara and Salihli in the Manisa province in West Anatolia (Fig. 1). According to the Köppen–Geiger climate classification system, continental climate prevails in the lake area and the area is rarely affected by the Mediterranean climate (Kottek et al. 2006). As mentioned above, the lake plays an important role in fisheries and irrigation of the region and Turkey as a whole.
All samples were collected monthly between March 2012 and February 2013 using 10–50 mm mesh trammel nets, gillnets and seines. A total of 1058 specimens (809 females and 249 males) of
Fish specimens were preserved in 4% formaldehyde solution and transported to the Limnology Laboratory, Faculty of Fisheries, Ege University. The length of all specimens was measured on a fish measuring board to the nearest millimeter and weighed using a digital scale with an accuracy of 0.001 g. The following biological parameters were analyzed: sex, total length (
LWR was determined using the formula
The von Bertalanffy growth model (Sparre et al. 1989) was calculated using the following formulas:
The age was estimated for each sample from fish scales. Scales for the analysis were removed from the lateral side, above the lateral line, near the dorsal fin of each specimen (Baglinière & Le Louarn 1987). Scales were preserved in 3% sodium hydroxide (Agger et al. 1974; Bagenal 1978) and alcohol (70–90%) to clean them before the reading process. Scales were examined under a binocular microscope for age determination using a 10× stereomicroscope. Age readings were performed according to Chugunova (1959) and Lagler (1966). Scale readings were taken twice by two independent readers (Avşar 2005). The data were tested by Student’s t-test and the growth types were determined. Fulton’s condition factor (
In this study, n = 809 females and n = 249 males were examined. The maximum age was estimated as VI and V for females and males, respectively. In the case of females, the maximum number of specimens was found in age II (28.92%) and in the case of males – in age I (18.43%). The samples did not include juveniles or small individuals. The total male rate was 0.30 (Table 1).
Age and sex ratio of
Females | Males | Combined Sex | F:M | ||||
---|---|---|---|---|---|---|---|
Age | n | % | n | % | n | % | |
I | 216 | 20.42 | 195 | 18.43 | 411 | 38.85 | 1:0.90 |
II | 306 | 28.92 | 36 | 3.40 | 342 | 32.33 | 1:0.11 |
III | 235 | 22.21 | 14 | 1.32 | 249 | 23.53 | 1:0.05 |
IV | 32 | 3.02 | 3 | 0.28 | 35 | 3.31 | 1:0.09 |
V | 7 | 0.66 | 1 | 0.09 | 8 | 0.76 | 1:0.14 |
VI | 13 | 1.23 | --- | --- | 13 | 1.23 | --- |
Total | 809 | 76.47 | 249 | 23.53 | 1058 | 100.00 | 1:0.30 |
Previous research on other lakes and reservoirs showed that the maximum age of
The total length of females and males ranged from 10.0 to 27.5 cm and from 10.2 to 24.0 cm; their weight varied from 17.1 to 378.4 g and from 17.7 to 2449.1 g, respectively. Table 2 presents the age–length relationship in the
Age–length relationship of
Age | n | Length (cm) | ||||
---|---|---|---|---|---|---|
Min. | Max | Mean ± CI | SD | |||
Female | I | 216 | 10.0 | 14.8 | 12.62 ± 0.117 | 0.979 |
II | 306 | 14.2 | 18.5 | 16.79 ± 0.108 | 0.958 | |
III | 235 | 16.8 | 23.5 | 19.43 ± 0.197 | 1.531 | |
IV | 32 | 18.2 | 24.8 | 22.23 ± 0.716 | 1.986 | |
V | 7 | 24.0 | 25.8 | 25.11 ± 0.529 | 0.572 | |
VI | 13 | 26.0 | 27.5 | 26.77 ± 0.245 | 0.405 | |
Male | I | 195 | 10.2 | 14.0 | 12.04 ± 0.102 | 0.718 |
II | 36 | 13.0 | 18.7 | 16.11 ± 0.408 | 1.205 | |
III | 14 | 17.0 | 21.5 | 19.00 ± 0.077 | 1.650 | |
IV | 3 | 18.8 | 23.5 | 21.23 ± 4.773 | 1.922 | |
V | 1 | 24.0 | 24.0 | 24.00 | - | |
Combined sex | I | 411 | 10.0 | 14.8 | 12.34 ± 0.089 | 0.911 |
II | 342 | 13.0 | 18.7 | 16.72 ± 0.107 | 1.009 | |
III | 249 | 16.8 | 23.5 | 19.40 ± 0.192 | 1.541 | |
IV | 35 | 18.2 | 24.8 | 22.25 ± 0.686 | 1.989 | |
V | 8 | 24.0 | 25.8 | 24.98 ± 0.542 | 0.650 | |
VI | 13 | 26.0 | 27.5 | 26.77 ± 0.245 | 0.405 |
LWR parameters were determined for females, males and for all specimens. Values for
LWR parameters of
Female | Male | Combined sex | |
---|---|---|---|
n | 809 | 249 | 1058 |
0.985 | 0.985 | 0.986 | |
0.014 | 0.015 | 0.018 | |
3.039 | 3.038 | 2.965 | |
0.018 | 0.033 | 0.014 | |
2.196 | 1.166 | −2.342 |
Von Bertalanffy growth parameters of the
Von Bertalanffy growth parameters of
n | K (year−1) | t0 (year) | L∞ (cm) | |
---|---|---|---|---|
Female | 809 | 0.177 | −1.382 | 36.68 |
Male | 249 | 0.178 | −1.573 | 35.40 |
Combined sex | 1058 | 0.189 | −1.238 | 35.86 |
Previous studies focused on the length distribution, age,
Length distributions,
Localities | Author | Length (cm) | L |
Max age | |||
---|---|---|---|---|---|---|---|
Lake Eğirdir | Balık et al., 2004FL | 9.0–33.0 | 33.30 | VI | 0.016 | 3.15 | 0.99 |
Bostancı et al. 2007b İzci 2004CA | 8.2–28.1 - | - - | - VI | 0.015 0.021 | 3.17 3.05 | 0.98 - | |
Özkök et al. 2007 | - | 38.90 | - | 0.016 | 3.12 | - | |
Lake Bafra | Bostancı et al. 2007a | 16.9–30.0 | - | VII | 0.026 | 2.97 | 0.97 |
Lake Beyşehir | Çınar et al. 2007FL | 7.1–27.4 | 36.20 | V | 0.013 | 3.18 | 0.94 |
Lake Uluabat | Emiroğlu 2008* | 8.5–33.3 | 36.44 | VII | 0.016 | 3.03 | 0.85 |
Lake İznik | Uysal et al. 2015FL | 7.8–32.2 | 40.00 | VI | 0.015 | 3.12 | 0.99 |
Lake Ladik | Yazıcıoğlu 2013 | 13.4–26.5 | - | - | 0.016 | 3.14 | 0.99 |
Buldan Reservoir | Sarı et al. 2008 | 9.7–25.5 | 31.60 | VI | 0.031 | 2.87 | 0.98 |
Seyitler Reservoir | Bulut et al. 2013*FL | 14.8–32.5 | 48.09 | VII | 0.027 | 2.93 | 0.81 |
Topçam Reservoir | Şaşı 2015FL | 23.8–29.5 | 41.46 | VI | 0.036 | 2.88 | 0.99 |
Lake Vegoritis (Greece) | Tsoumani et al. 2006 | 16.2–33.2 | - | - | 0.009 | 3.25 | 0.98 |
Lake Trichonis (Greece) | Tsoumani et al. 2006 | 28.0–37.7 | - | - | 0.004 | 3.38 | 0.97 |
Danube River | Gheorghe et al. 2012 | 15.0–35.0 | 39.38 | - | 0.029 | 2.84 | 0.95 |
İlhan et al. 2014 | 10.0–27.5 | - | - | - | - | - | |
Lake Marmara | İlhan & Sarı 2015* Balık et al. 1991CA | 6.8–27.5 - | - 36.05 | - VI | 0.017 0.054 | 2.97 2.80 | 0.99 0.93 |
This study* | 10.2–27.5 | 35.86 | VI | 0.018 | 2.95 | 0.99 |
*CA:
The studies determined the maximum length distributions in Lake Uluabat (total length) as 8.5–33.3 cm in Bursa (Emiroğlu 2008) and 9.0–33.0 cm in Lake Eğirdir (fork length) in Isparta (Balık et al. 2004). The maximum total length was 37.3 cm in Lake Trichonis; the maximum fork length was determined as 32.5 cm in Lake İznik (Tsoumani et al. 2006). The minimum total length was 6.8 cm in Lake Marmara (İlhan & Sarı 2013) and the minimum fork length was 7.1 cm in Lake Beyşehir (Çınar et al. 2007). In Lake Trichonis, Lake Vegoritis, the Danube River and many other populations, the maximum total length of members proved to be greater than in this study (Table 5). Many biotic and abiotic factors (e.g. sex, temperature, gonad maturity, size range, health, and condition of fish) can directly affect the LWR (Tesch 1971).
The maximum asymptotic length was 48.09 cm (fork length) in the Seyitler Reservoir (Bulut et al. 2013) and the minimum asymptotic length was 31.60 cm in the Buldan Reservoir (Sarı et al. 2008). Values from some other studies were:
Two studies on
LWRs were highly significant, with most
One of the LWR parameters,
The condition factors for
Since its introduction into natural lakes and reservoirs,
There are growing concerns about the distribution and impact of
Furthermore, biological invasion is a major threat to endemic species. It is critically important that further studies should focus on negative impacts of invasive species on native species. The well-being of ecosystems could only be maintained by increasing the number of such studies, otherwise it is impossible to properly manage fishery activities in regions with unknown ecology.