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Fish assemblage and diversity in lakes of western and central Turkey: role of geo-climatic and other environmental variables
Abstract
We conducted a fish survey in 40 lakes in western and central Turkey. Fifty species (one to eleven per lake) were recorded, including eighteen endemic and seven alien species. We investigated which local geo-climatic and other environmental variables shaped the fish assemblages. Altitude and temperature turned out to be the most important factors for total species richness as well as richness of omnivorous and zooplanktivorous species and the Shannon–Wiener diversity index, with more species and higher diversity occurring in the warmer lowland lakes. Altitude may affect the fish assemblage directly through dispersal limitation or indirectly by creating a gradient in temperature with which it was strongly correlated. Cyprinidae was the most species-rich and widespread family. Atherinidae, Gobiidae, and Mugilidae (families of marine origin) were mainly found in the lowland regions, while Salmonidae exclusively appeared in the high-altitude lakes. The presence of widely distributed translocated native and alien species revealed a large human impact on the fish assemblages, potentially threatening the rich endemic fish fauna in lakes in this region.
... Although small-sized zooplankton groups, like rotifers, small-sized cladocerans and nauplii are capable of grazing on small phytoplankton species, large cladocerans and calanoid copepods usually prefer intermediate-and large-sized phytoplankton (Lampert and Sommer, 2007;Colina et al., 2016). In eutrophic, warm temperate and subtropical lakes (hereafter referred as warm lakes), the zooplankton community is usually dominated by small-sized zooplankton species due to predation pressure on the zooplankton by fish (Jeppesen et al., 1997;Vadadi-Fülöp et al., 2012;Tavşanoglu et al., 2015), which are predominately small, omnivorous and found in high density (Meerhoff et al., 2012;Frau et al., 2015;Boll et al., 2016). Consequently, grazing pressure by small-sized grazers on small phytoplankton is expected to be more intense in warm or eutrophic lakes (Matsuzaki et al., 2018). ...
... Fish community structure and abundance (catch per numbers unit effort, CPUE, number net −1 ) were determined using Lundgren multi-mesh gillnets, covering 12 mesh sizes (5, 6.5, 8, 10, 12.5, 15.5, 19.5, 24.5, 29, 35, 43 and 55 mm; see Boll et al., 2016 for details). The number of gillnets for each lake was determined based on the lake area (0-2 ha: 2 sets of nets, 2-20 ha: 4 sets nets, 20-100 ha: 6 sets nets and > 100 ha: 8 sets nets). ...
... The gillnets were deployed parallel to the shore, to both littoral and pelagic zones for 12 h. Detailed information can be found in Boll et al. (2016). Zooplanktivorous fish density (number of fish net −1 night −1 ), and the total fish to zooplanktivorous fish ratio were calculated. ...
Body size is an important trait of any organism, including phytoplankton, because it affects physiological and morphological performance, reproduction, population growth rate and competitive interactions. Understanding how interacting top-down and bottom-up factors influence phytoplankton cell size in different aquatic environments is still a challenge. Structural equation modeling (SEM) is a comprehensive multivariate statistical tool for detecting cause–effect relationship among different variables and their hierarchical structure in complex networks (e.g. trophic interactions in ecosystems). Here, several SEM models were employed to investigate the direct and indirect interaction pathways affecting the phytoplankton size structure in 44 mostly eutrophic and hypereutrophic permanent lakes in western Turkey. Among the 15 environmental variables tested, only rotifers and Carlson’s Trophic Index (TSI) had significant direct positive effect on the mean phytoplankton size and size variance, respectively. The results indicate that both bottom-up and top-down factors significantly affect phytoplankton community size structure in eutrophic and hypereutrophic lakes in warm climates. Rotifer grazing increased the abundance of large-sized phytoplankton species, such as filamentous and colonial cyanobacteria and TSI affected phytoplankton size variance, with a higher size variance in hypereutrophic lakes.
... Increased temperatures, salinity, and eutrophication substantially influence lake food web structure and community composition (Carpenter et al. 2001, Meerhoff et al. 2007, Moss 2010, Gutierrez et al. 2018. Warmer lakes tend to have higher densities of small fish (Blanck and Lamouroux 2007, Meerhoff et al. 2007, Brucet et al. 2013, Boll et al. 2016) and small-sized zooplankton (e.g., Gyllström et al. 2005, Tavşanoğlu et al. 2015 and are thus more sensitive to nutrient addition because grazer control of phytoplankton is weaker (Meerhoff et al. 2007, Lemmens et al. 2018. Consequently, higher frequency and longer duration of cyanobacteria blooms have been observed (Havens et al. 2019). ...
... The composition and relative abundance of fish were determined using multiple mesh-sized Lundgren gill nets (mesh sizes 5-55 mm, randomly lined). The number of nets used per lake increased with lake area, with a maximum of 8 (Moss et al. 2003, Boll et al. 2016. We used average catch per unit effort (CPUE), number per unit effort (NPUE), or biomass per unit effort (BPUE), and the ratio of fish <10 cm to total fish numbers as an indicator of the proportion of small fish. ...
... Low abundance of piscivores with increasing temperature may reflect that consumption of animals is less appealing at higher temperatures (Moss 2010. A more detailed study on fish abundance and community structure undertaken in the same study lakes as those used in our investigation suggested that temperature was among the most important factors contributing to fish species richness, especially the proportions of small omnivorous and zooplanktivorous fish (Boll et al. 2016). Similarly, the impact of temperature on fish richness has been evidenced in large-scale comparative cross-latitudinal studies on shallow and deep lakes, where higher contributions of small, fast-growing species were recorded in subtropical and Mediterranean regions than in cold temperate areas (Blanco et al. 2003, Blanck and Lamouroux 2007, Brucet et al. 2013, Emmrich et al. 2014. ...
Climate warming threatens the structure and function of shallow lakes, not least those in the Mediterranean climate. We used a space-for-time substitution approach to assess the response of trophic and community structures as well as the richness and evenness of multiple trophic levels to temperature, hydrological, and nutrient constraints. We selected 41 lakes covering wide climatic, hydrological, and nutrient gradients within a short distance for reducing the effect of biogeographical factors in the western Anatolian plateau of Turkey. Generalized linear model analyses revealed that temperature was overall the most important driving variable, followed by total nitrogen (TN) and salinity. The chlorophyll a:total phosphorus ratio, the cyanobacteria:total phytoplankton biovolume ratio, the fish:zooplankton biomass ratio, the proportion of small fish, and fish richness increased with increasing temperature, whereas macrophyte plant volume inhabited (PVI, %), richness, and evenness decreased. Grazing pressure, macrophyte coverage, piscivore biomass, phytoplankton richness, and evenness decreased significantly with both increasing TN and temperature. Temperature and nutrients also separated the northern highland lakes from other lakes in a non-metric multidimensional scaling analysis. Additionally, salinity reduced richness and evenness of phytoplankton and zooplankton. Our results indicate major changes in lake structure and functioning with warming and eutrophication, and highlight the need for strict control of nutrients and water use.
... Captured fish were identified to species level and measured (total length rounded to the nearest cm). For more details on the samplings and lake environmental characteristics, see Brucet et al. (2013), Emmrich et al. (2014), Boll et al. (2016) and Mehner et al. (2017). ...
... The native/translocated/introduced status of each fish species was defined to at least a lake basin-specific level according to the literature (Filipsson 1994, Tammi et al. 2003, Kottelat & Freyhof 2007, Brosse et al. 2013, Dias et al. 2014, Tarkan et al. 2015, Boll et al. 2016, Trochine et al. 2017. For some ecoregions (Northern and Western Anatolia and Northern Baltic Drainages) information was available for each individual study lake. ...
... All rights reserved.' m with mountains forming barriers between the river basins, may also have promoted speciation in Anatolian lakes along with a lack of major glaciation (Kosswig 1955, Boll et al. 2016. In contrast, in central and northern European ecoregions, the fish fauna is impoverished as a result of climatic changes caused by periods of glaciations (Dynesius and Jansson 2000, Griffiths 2006, Lévêque et al. 2008). ...
Body size, coupled with abundance and taxonomy, may help to understand the mechanisms shaping community structure. Since the body size of fish is closely related to their trophic niche, size diversity (based on individual body size) of fish communities may capture intraspecific variations in fish trophic niches that are not detected by species diversity. Thus, the relationship between size diversity and species diversity may help to integrate variation at both intraspecific and interspecific levels. We studied the relationship between species diversity and size diversity as a measure of the degree of overlap in size among species and thereby the potential overlap in niches in a community. We hypothesized that the relationship between size diversity and species would be different across the European continent due to different levels of size overlap in fish communities. The data were derived from samplings of fish communities using standardised benthic gill nets in 363 lakes. At the continental scale, size diversity increased with species diversity; at the ecoregion scale, the slope of the relation changed across the continent, with the greatest mismatch occurring in northern Europe where communities comprised only one or a few species, but each of which exhibited a great range in size. There was an increase in slope towards the south with significant relations for four out of six ecoregions. The steeper size diversity-species diversity slope at lower latitudes is attributable to a lower overlap in fish size and thus likely to finer niche separation. Our results also suggest that size diversity is not a strong surrogate for species diversity in European lake fish communities. Thus, particularly in fish communities composed of few species, measuring size diversity may help to detect potential functional variation which may be neglected by measuring species diversity alone.
... Previous work on freshwater fish has shown that total species richness was also influenced by factors related to energy availability (i.e. net primary productivity) and climatic parameters (annual rainfall and average annual temperature) (Oberdorff et al. 1999(Oberdorff et al. , 2011Tedesco et al. 2005;Tisseuil et al. 2013;Griffiths et al. 2014;Pelayo-Villamil et al. 2015;Boll et al. 2016). Moreover, water depth, altitude, pH and total phosphorus concentration determine fish richness (Allen et al. 1999;Helminen et al. 2000;Zhao et al. 2006;Brucet et al. 2013;Boll et al. 2016;Oikonomou and Stefanidis, 2020). ...
... net primary productivity) and climatic parameters (annual rainfall and average annual temperature) (Oberdorff et al. 1999(Oberdorff et al. , 2011Tedesco et al. 2005;Tisseuil et al. 2013;Griffiths et al. 2014;Pelayo-Villamil et al. 2015;Boll et al. 2016). Moreover, water depth, altitude, pH and total phosphorus concentration determine fish richness (Allen et al. 1999;Helminen et al. 2000;Zhao et al. 2006;Brucet et al. 2013;Boll et al. 2016;Oikonomou and Stefanidis, 2020). Phytoplankton species richness was associated to lake chlorophyll concentration and water temperature, resembling the effects of productivity, habitat area and temperature on diversity patterns (Stomp et al. 2011). ...
Freshwater ecosystems occupy only 2.3% of Earth's surface, yet they support an excessive portion of the world's most speciose and endemic taxa. They are estimated to harbor 12% of the world's fauna and one third (18,000 species) of the global vertebrate species richness. In this chapter, the author draws together threads of recent theoretical and empirical results and patterns at multiple scales; both may offer a useful roadmap of theoretical background for identifying new paths of investigation and future challenges into the field of freshwater biogeography, which needs to be considered to safeguard the status of aquatic ecosystems. Neotropics and Afrotropics are among the global hotspots of freshwater fish endemism. Recent findings in freshwaters underscore the importance of studying simultaneously historical processes, drainage basin characteristics and local environmental conditions to understand variation in species richness. Freshwater species richness and endemism patterns are the result of climate, productivity and biogeographical history.
... The study lakes have Mediterranean hot (Csa) and warm (Csb) summer climates according to the Köppen classification system (Peel et al., 2007). Detailed information on methods can be found in Ç akıroglu et al. (2014), Levi et al. (2014), Tavşanoglu et al. (2015) and Boll et al. (2016). Briefly, lake water temperature (°C), dissolved oxygen (ml l -1 ), conductivity (±1 lS cm -1 ), salinity (%) and pH were determined in situ using a multi-probe meter (YSI 556 MPS, Ohio, USA). ...
... -1 ) were determined for the pelagic part of each lake by overnight (12 h) fishing with multiple mesh size Lundgren gill nets (from 5 to 55 mm, randomly lined). The number of nets used depended on the size of the lake (Moss et al., 2003, Jeppesen et al., 2010; details can be found in Boll et al. (2016). ...
To elucidate the specific and combined effects of bottom-up and top-down control on the microbial community in warm lakes, we sampled microbial community along with physical–chemical and biological variables and performed in situ food web experiments, in 14 Turkish shallow lakes with contrasting nutrient levels and predation pressures. Our field results revealed that differences in microbial communities correlated with differences in zooplankton community structure, temperature (increasing nutrient concentrations, change in zooplankton composition), nutrient concentrations (increasing bacteria and heterotrophic nanoflagellate abundances with increasing nitrogen concentrations and temperature) and macrophyte coverage (ciliates as potential consumers of bacteria and HNF was strongest in macrophyte-dominated lakes). Our in situ experimental study revealed that the zooplankton not only affect the biomass and composition of microbial communities but also alter the microbial structure and trophic relationships. Our results therefore indicate that both bottom-up factors and top-down effects were important for the efficiency of the carbon transfer from bacteria to higher trophic levels in the study lakes. Due to an anticipated increase in eutrophication, temperature and alteration of the classical food web with climate warming, major changes in the microbial community of lakes are, therefore, expected in a warmer future in semi-arid Mediterranean climatic regions.
... Fish database and sampling We used the dataset from the EU project WISER (Water bodies in Europe: Integrative Systems to assess Ecological status and Recovery) created during a European Water Framework Directive intercalibration process, encompassing 1922 lakes ( Argillier et al. 2013;Brucet et al. 2013;Mehner et al. 2017), and data from 57 lakes located in Western and Central Turkey ( Boll et al. 2016). Among these lakes, Chl a concentrations and fish size distributions were available only for 227 lakes located in 10 countries (Czech Republic, Estonia, France, Germany, Italy, Norway, Slovenia, Sweden, Turkey, and United Kingdom) along a latitudinal gradient between 36.7 N and 67.1 N and a longitudinal gradient between 4.2 W and 36.2 ...
Fish community feeding and production rates may differ between lakes despite similar fish biomass levels because of differences in size structure and local temperature. Therefore, across-lake comparisons of the strength and direction of top-down and bottom-up fish–phytoplankton relationships should consider these factors. We used the metabolic theory of ecology to calculate size- and temperature-corrected community energy demand (CEDom) and
community production (CP) of omnivorous fishes in 227 European lakes from major habitat types (MHTs) of polar freshwaters, temperate floodplain rivers and wetlands, and temperate coastal rivers. We related CEDom with total phosphorus (TP)-corrected chlorophyll a (Chl a) concentrations to evaluate a potential top-down directed trophic cascade from fish to phytoplankton. Furthermore, we related Chl a with CP to demonstrate potential bottom-up effects of phytoplankton on fish. For both analyses, we added the CED of piscivorous fishes (CEDpi) as a predictor to account for potential predation effects on the omnivorous fish community. CEDom was weakly positively related with TP-corrected Chl a, but the strength of the relationship differed between MHTs. In contrast, CP was consistently positively related with Chl a in the entire dataset. CEDpi did not contribute to top-down or bottom-up relationships. The
application of metabolic variables characterizing fish community feeding and production rates makes these results robust because the approach accounted for the usually neglected effects of fish size and temperature in across-lake comparisons. Our results suggest that bottom-up effects from phytoplankton on fish secondary production in lakes are substantially stronger than top-down effects from fish on phytoplankton biomass
... More species are required to insure a constant supply of healthy ecosystem and best services as spatial and temporal variability increases, which typically occurs as longer era periods and larger regions (e.g. complete basins with large and small tributaries) are considered (Hooper et al, 2005;Dwivedi and Nautiyal, 2010;Boll et al, 2016). Depth of the river, quality of water and water temperature are most important factors for healthy fish landing and species richness (Pathak et al, 2015;Dwivedi et al, 2016a). ...
Fisheries are a major source of food, leisure and income for humanity and fishers community globally. The Ganga river fauna and flora is threatened by anthropogenic activities and resulting water pollution, accumulation of heavy metals, eutrophication, damming, alteration of hydrology and introduction of exotic species. Current work was assumed to study the fish catch from the Ganga river at Allahabad during the period July 2015 to June 2016. The 89 fish species were recorded from the Ganga river at Allahabad. The examination of annual data on fish landing showed that the estimated annual
catch was dominated by miscellaneous group followed by Cyprinus carpio and Oreochromis niloticus. They accounted for 19.09%, 15.50% and 14.56%, respectively. In case of Indian major carps, Cirrhinus mrigala shared maximum contribution. In the summer and monsoon seasons miscellaneous groups were dominating while in winter season, O. niloticus in the Ganga river. The fish O. niloticus is an exotic species which is known to invade the river. The catch data indicated towards a significant decline in Indigenous species and immediate need to address the restoration and conservation for stock of Indian major carps.
... More species are required to insure a constant supply of healthy ecosystem and best services as spatial and temporal variability increases, which typically occurs as longer era periods and larger regions (e.g. complete basins with large and small tributaries) are considered (Hooper et al, 2005;Dwivedi and Nautiyal, 2010;Boll et al, 2016). Depth of the river, quality of water and water temperature are most important factors for healthy fish landing and species richness (Pathak et al, 2015;Dwivedi et al, 2016a). ...
Fisheries are a major source of food, leisure and income for humanity and fishers community globally. The
Ganga river fauna and flora is threatened by anthropogenic activities and resulting water pollution, accumulation of heavy metals, eutrophication, damming, alteration of hydrology and introduction of exotic species. Current work was assumed to study the fish catch from the Ganga river at Allahabad during the period July 2015 to June 2016. The 89 fish species were recorded from the Ganga river at Allahabad. The examination of annual data on fish landing showed that the estimated annual catch was dominated by miscellaneous group followed by Cyprinus carpio and Oreochromis niloticus. They accounted for 19.09%, 15.50% and 14.56%, respectively. In case of Indian major carps, Cirrhinus mrigala shared maximum contribution. In the summer and monsoon seasons miscellaneous groups were dominating while in winter season, O. niloticus in the Ganga
river. The fish O. niloticus is an exotic species which is known to invade the river. The catch data indicated towards a significant decline in Indigenous species and immediate need to address the restoration and conservation for stock of Indian major carps.
... Non-native fishes are also changed selectivity of gear due to nature, dwelling behaviour and ecological condition [53][54][55]. Non-native fishes are helping for homogenization of faunas, increasing of diversity [56,57] and create pressure for native species [58][59][60]. ...
Good knowledge of netting approach is essential for scientific and sustainable based fisheries management in
lotic water bodies. The large sizes of fishes are more attract to fishers compared to small fishes. This type of fishing is very harmful for future stock and recruitment. 1.5 inch to 3.5 inch mesh size cast net was used in the Ganga River at Allahabad. Cirrhinus mrigala is mainly captured by drag net from the Ganga River, India. Studies were undertaken during March 2014 to February 2015 from the middle stretch of the Ganga River, India. 423 fish specimens (206 males and 217 females) were examined of Cirrhinus mrigala. An over-all picture of age, growth increment and age composition of C. mrigala has been obtained by the study of its scales. The age composition of C. mrigala varied from 0+ to 10+. On the basis of pooled sampled specimen in the total length ranges varied from 16.8 cm to 92.4 cm showed that the fish attained the mean length 30.24 cm, 48.02 cm, 61.50 cm, 70.31, 77.63, 81.84 cm, 85.30 cm, 88.57 cm, 90.15 cm, 91.8 cm in 1+, 2+, 3+, 4+, 5+, 6+, 7+, 8+, 9+ and 10+ age groups respectively. The growth increments in C. mrigala was recorded as 30.24 cm, 17.78 cm, 13.48 cm, 8.81 cm, 7.32 cm, 4.21 cm, 3.46 cm, 3.27 cm, 1.58 cm and 1.65 cm for 1+ to 10+ age groups, respectively. The maximum growth increment was recorded in 1st year and minimum in 9th year of life. The slow growth increment observed after third year may be attributed to the maturity attained after second year of life. It is well known that the growth potential is used for the gonad development. Drag netting is reducing the size of C. mrigala in the Ganga River.
... Omnivorous Carassius gibelio and benthivorous species Tinca tinca (from 1990s onwards) and Atherina boyeri (in 2002) have also been introduced to the lake (Innal and Erk'akan 2006; Yeğen et al., 2006). Carassius gibelio has been considered as invasive in Turkey (Aydın et al., 2011 ), and unfortunately is a widespread species recorded in many lakes (Boll et al., 2016). Futhermore, Beklioğlu et al. (2014) found that the invasive benthivorous Pseudorasbora parva was the dominant fish species in Lake Beyşehir in 2010 and 2011. ...
The primary objective of this study was to determine the relative roles of local environmental (Local), geo-climatic (Geo), and spatial (Spatial) factors to taxonomic, functional , and phylogenetic β-diversity of stream fish in a large basin in Northeast China. We quantified the current biodiversity patterns of fish communities in the Hun-Tai River using β-diversity. We assessed (i) corresponding contributions of turnover and nestedness within the taxonomic, functional, and phylogenetic β-diversity of fishes; (ii) correlations among β-diversity facets (i.e., taxonomic, functional, and phylogenetic facets); (iii) relative contributions of Local, Geo, and Spatial factors to β-diversity. We collected fish communities from 171 sampling sites. Mantel tests were used to examine the correlation of three facets of β-diversity and their components (i.e., total, nest-edness, and turnover). Distance-based redundancy analysis and variation partitioning assess the relative contributions of Local, Geo, and Spatial factors to β-diversity. We found that turnover is the main driving mechanism for β-diversity in fish. Among the facets of β-diversity, taxonomic and phylogenetic facets have strong ecological information association. Spatial factors have a general contribution to various facets of β-diversity and its components. From aspects of fish β-diversity conservation, connectivity and habitat heterogeneity need to be maintained in the entire aquatic environment. In addition, protecting taxonomic β-diversity is helpful for maintaining phylogenetic β-diversity. K E Y W O R D S biodiversity protection, ecosystem, metacommunity, nestedness, turnover, β-diversity
Invasion of non-native species is considered a major threat to global biodiversity. Here we present a
comprehensive overview of the occurrence, richness and biomass contribution of non-native fish
species in 1943 standing water bodies from 14 countries of the Western Palearctic, based on
standardised fish catches by multi-mesh gillnetting. We expected strong geographical gradients to
emerge in the occurrence of non-natives. We further hypothesised that the contribution by nonnatives
to the local fish community biomass was correlated with local richness and the trophic level
of native and non-native species. Non-native fish species occurred in 304 of 1943 water bodies
(16%). If the average number of occupied water bodies per country was weighted by number of
water bodies per country, the grand mean occurrence of non-natives in Western Palearctic water
bodies was 10%. Exotic (non-native to the Palearctic) and translocated (non-native only to
parts of the Palearctic) species were found in 164 (8.4%) or 235 (12.1%) of the water bodies,
respectively. The occurrence and local richness of non-native fish species increased with temperature,
precipitation and lake area and were substantially higher in reservoirs than in natural lakes. High
local biomass contributions of non-native species were strongly correlated with low richness of native
species and high richness of non-native species, whereas the trophic level of the fish species
had only a weak effect. Single non-native species rarely dominated community biomass, but high
biomass contributions and thus strong community and ecosystem impacts can be expected if several
non-native species accumulate in a water body.
1. Aphanius anatoliae (Leidenfrost, 1912) and Pseudophoxinus ninae (Freyhof and Özulug, 2006) are two fish species endemic to Anatolia. 2. In this study, population structures, length-weight relationships and condition were calculated for A. anatoliae and P. ninae living in Karaevli Lake (Burdur, Turkey). 3. A total of 107 individuals of A. anatoliae and 42 individuals of P. ninae were examined. 4. The population of A. anatoliae ranged in size between 2 cm and 5.3 cm and showed an overall good condition for the whole sample and for both sexes. The length and weight relationships for this species were calculated as: W = 0.0094 TL 3.256 ; W = 0.0095 TL 3.239 ; W = 0.0086 TL 3.349 for total sample, females and males respectively. 5. The sample of P. ninae (ranging in size from 2.6 cm to 9.3 cm) also resulted to be in good condition and the length and weight relationships for the population were as follows: W = 0.0075 TL 3.475 for the total sample, W = 0.0072 TL 3.495 for females and W = 0.0066 TL 3.486 for males. 6. This study represented the length-weight relationship for P. ninae for the first time. ÖZ 1. Aphanius anatoliae (Leidenfrost, 1912) ve Pseudophoxinus ninae (Freyhof and Özulug, 2006) Anadolu'ya endemik iki balık türüdür. 2. Bu çalışmada Karaevli Gölü (Burdur – Türkiye)'nde yaşayan A. anatoliae ve P. ninae popülasyonlarının kondisyonları, populasyon yapıları ve boy-ağırlık ilişkileri hesaplanmıştır. 3. 107 birey A. anatoliae ve 42 birey P. ninae incelenmiştir. 4. A. anatoliae popülasyonu 2 ile 5,3 cm boy aralığındadır. Her iki eşey ve tüm örnekler açısından iyi kondisyon göstermektedir. Boy-ağırlık ilişkisi tüm örnekler, dişiler ve erkekler için sırasıyla W = 0.0094 TL 3.256 ; W = 0.0095 TL 3.239 ; W = 0.0086 TL 3.349 olarak hesaplanmıştır. 5. P. ninae örnekleri de (2.6-9.3 cm boy dağılımında) iyi kondisyon göstermektedir. Boy-ağırlık ilişkileri sırası ile tüm örnekler için W = 0.0075 TL 3.475 , dişiler için W = 0.0072 TL 3.495 ; erkekler için W = 0.0066 TL 3.486 'dır. 6. Bu çalışma, P. ninae için ilk boy –ağırlık ilişkisi çalışmasıdır. ANAHTAR KELİMELER: Anadolu, Cyprinidae, Cyprinodontidae, endemik, tatlısu balıkları. L-W relationships, population structure and body condition of A. anatoliae and P. ninae living in Karaevli Lake 75
Cladocerans are increasingly used in palaeolimnological studies as their community composition is sensitive to both anthropogenic and natural forces in lakes. We present the results of a palaeolimnological investigation of three Turkish shallow lakes located in cold dry steppe and semi-dry Mediterranean climatic regions. The aim was to elucidate historical changes in environmental conditions by analysing sub-fossil cladocerans in 210Pb-dated sediment cores. Sub-fossil cladoceran remains from the surface sediment of 40 Turkish lakes were analysed to examine the environmental factors that most correlated with variation in the cladoceran assemblage. Redundancy analysis showed that salinity, macrophyte abundance, fish density, depth and total phosphorus were the most correlated with change in cladoceran assemblage composition with eigenvalues for the first and the second axes being λ
1 = 0.312 and λ
2 = 0.061, respectively. Sedimentary cladoceran assemblages from three cores were placed passively within the framework of the surface sediment ordination. The results reveal a prevalent impact of salinity, fish abundance and water level changes from the past to present. Thus, using cladoceran-based inferences, we traced key environmental changes related to variation in climate change, restoration and water level regulation over the last century.
The ichthyofaunal changes in Lake Eǧirdir between 1915 and 2007 were reviewed. It was understood that the most drastic change in the ichthyofauna of Lake Eǧirdir occurred in 1955 with the introduction of pike-perch (Sander lucioperca), and that the process of change continued with the addition of Prussian carp (Carassius gibelio) in 1996 and big scale sand smelt (Atherina boyeri) in 2003. Today, there are 15 fish taxa (10 native, 5 non-native) in Lake Eǧirdir. It was determined that, among the endemic species of Lake Eǧirdir, Handlirsch's minnow (Pseudophoxinus handlirschi) is extinct (EX), Ereǧli minnow (Hemigrammocapoeta kemali) disappeared, and Eǧirdir minnow (Pseudophoxinus egridiri) and Eǧirdir barb (Capoeta pestai) are critically endangered (CR).
The aim of this study was to learn the invasion speed and sex ratio, which would be indicative of invasive character, of a nonnative fish species, gibel carp, by reporting its new localities in the Marmara region of northwestern Turkey. Whether the occurrence of gibel carp in freshwater bodies of the Marmara region was random (i.e. chance element) was tested. The question of population increase since first introduction was also examined. Among 14 new locations for gibel carp found during this study, the majority were in mostly lentic ecosystems. The invasion rate of gibel carp in the Marmara region, since its first introduction in the early 1980s, is approximately 1 new water body per year (1.17; number of sites invaded by gibel carp = 35). Females significantly outnumbered males in 10 out of the 12 populations studied, with the sex ratio deviating from unity (1:1) in all populations except 2. The regional extent of gibel carp occurrence increased with the number of years since first introduction (y = 1.34x - 2651.1, F = 47.41, P < 0.001, = 0.95). The implications for conservation of native fishes are discussed.
Turkey's natural river systems have been anthropogenically altered in the past century. Native fish communities of river systems have come under increasing pressure from water engineering projects, pollution, overfishing and the movements of alien fish species. Introduction of alien fishes is one of the main threats to the survival and genetic integrity of native fishes around the world. In Turkey, alien freshwater fish are continuing to increase in number of species, abundance, and distribution. The present paper reviews fish stocking studies in Turkey's reservoirs.
Turkey is a hotspot of freshwater fish diversity and endemism, holding a unique ichthyofauna containing distinct European and Asian elements. Currently, 78 en-demic species are recognised from Turkey, 65 of which are classified as Critically Endangered or Endangered. Habitat degradation, pollution, and the introduction of non-native fishes are the greatest threats to this unique ichthyofauna. We compiled data on the introduction and distribution of freshwater fishes in Turkey, both non-native and translocated, based on historical accounts and recent surveys. Thirty fish species have been introduced, 11 of which are translocations within Turkey. The overall establishment success was 64% (44% for non-natives and 100% for translo-cated species). New species continue to be introduced at a rate of 4.8 species per decade , of which 3.1 species establish per decade. Fisheries and aquaculture are two main vectors of deliberate introduction, but the contaminant of stockings is the primary pathway for secondary spread, in particular for Carassius gibelio, Pseu-dorasbora parva and Lepomis gibbosus. Natural dispersion of species introduced into neighbouring countries through trans-boundary river systems is highlighted as the most likely pathway for future species introductions. We discuss the management options available and outline how these can be incorporated into freshwater fish conservation and non-native fish management programmes. Education, public awareness and information are central components to reduce current rate of fish introductions in Turkey.
Delineating biogeographical regions is a critical step towards the establishment and evaluation of conservation priorities. In the present study, we analysed the distribution patterns of the freshwater fish of an understudied European biodiversity hotspot, the Balkan Peninsula. Based on the most extensive available database of native freshwater fish species distributions, we performed a hierarchical clustering analysis to identify the major biogeographical regions of the Balkan Peninsula. We also highlighted the ‘hottest hotspots’ of freshwater fish diversity across the delimited biogeographical regions by describing the patterns of species richness, endemic and vulnerable species; indicator species were also determined. The bioregionalisation scheme consisted of eight groups of drainage basins that correspond to distinct regions of the Balkan Peninsula. Overall, the delineated biogeographical regions varied in terms of species richness, endemism, vulnerability (i.e. extinction threats) and indicator species composition. From a conservation perspective, this study emphasises the prioritisation of areas characterised by high levels of irreplaceability (endemism) and vulnerability (i.e. the Attikobeotia region, Ionian Sea and Prespa Lakes) and stresses the necessity of implementing a network of protected freshwater areas across the Balkan Peninsula.
The Turkish species of the Cyprinodontiform genus Aphanius Nardo 1827 are described. The naming used follows Wildekamp (1993) (1) as the latest available revision. Information is given on morphology, sexual dimorphism, colouration and distribution, as well as remarks on taxonomy, nomenclature, distribution, variability and conservation. Comments are given on the Lazara (1995) (2) revalidation of Lebias as a distinct genus. It is shown that Valenciennes (1846) (3) is the first revisor of Lebias, and not Lazara, and that Aphanius should be maintained as a genus. The taxon Aphanius chantrei (Galliard 1895) is regarded as a junior synonym of Aphanius danfordii (Boulenger 1890), a lectotype for A. danfordii is designated and amore detailed type locality is given.
Invasive common carp Cyprinus carpio has long been identified as a contributor to water quality deterioration, disrupted ecosystem processes, and shifts in biological assemblage structure. In contrast, little information is available regarding the effects of native benthivorous species on aquatic systems despite their functional similarity to common carp. Effects of common carp and the native black bullhead Ameiurus melas on sediment resuspension, nutrient concentrations, macrophytes, and assemblage structure of zooplankton and macroinvertebrates, were experimentally evaluated. We observed decreased water clarity, increased nutrient concentrations, decreased macrophyte biomass, and decreased benthic macroinvertebrate abundance and biomass associated with common carp, regardless of the presence of black bullhead. In contrast, black bullhead increased total phosphorus, and chlorophyll a concentrations and copepod abundance, but had little or no effect on other measured water quality and biological variables when compared to control conditions. Overall, experimental results suggest that although black bullhead tend to be tolerant of degraded ecosystems, they are not a source of physical changes to the environment known to be responsible for perpetuating degraded water quality (e.g., stable state shifts). Therefore, increased abundance of native species, such as black bullhead, following the invasion of common carp, may serve as an indicator of ecological conditions and should not to be assumed as causative.
Chondrostoma meandrense is an endangered freshwater fish species in Anatolia (Turkey). Its population has declined and should be strictly protected.
In this study, the hierarchical clustering technique, called Ward method, was applied for grouping common features of air temperature series, precipitation total and relative humidity series of 244 stations in Turkey. Results of clustering exhibited the impact of physical geographical features of Turkey, such as topography, orography, land–sea distribution and the high Anatolian peninsula on the geographical variability. Based on the monthly series of nine climatological observations recorded for the period of 1970–2010, 12 and 14 clusters of climate zones are determined. However, from the comparative analyses, it is decided that 14 clusters represent the climate of Turkey more realistically. These clusters are named as (1) Dry Summer Subtropical Semihumid Coastal Aegean Region; (2) Dry-Subhumid Mid-Western Anatolia Region; (3 and 4) Dry Summer Subtropical Humid Coastal Mediterranean region [(3) West coast Mediterranean and (4) Eastern Mediterranean sub-regions]; (5) Semihumid Eastern Marmara Transition Sub-region; (6) Dry Summer Subtropical Semihumid/Semiarid Continental Mediterranean region; (7) Semihumid Cold Continental Eastern Anatolia region; (8) Dry-subhumid/Semiarid Continental Central Anatolia Region; (9 and 10) Mid-latitude Humid Temperate Coastal Black Sea Region [(9) West Coast Black Sea and (10) East Coast Black Sea sub-regions]; (11) Semihumid Western Marmara Transition Sub-region; (12) Semihumid Continental Central to Eastern Anatolia Sub-region; (13) Rainy Summer Semihumid Cold Continental Northeastern Anatolia Sub-region; and (14) Semihumid Continental Mediterranean to Eastern Anatolia Transition Sub-region. We believe that this study can be considered as a reference for the other climate-related researches of Turkey, and can be useful for the detection of Turkish climate regions, which are obtained by a long-term time course dataset having many meteorological variables.
The distribution of freshwater fish is influ-enced by food availability, habitat heterogeneity, competition, predation, trophic state, and presence/ absence of macrophytes. This poses a challenge to monitoring, and researchers have been struggling to develop accurate sampling methods for obtaining a better understanding of fish communities. We compare fish community composition, richness, and diversity in 56 Danish lakes using data obtained by gillnetting in different lake zones and near-shore electrofishing, respectively. On average, electrofishing captured more species than offshore gillnets, but not more than littoral gillnets. Overall, the different fish sampling methods showed consistency as to fish community structure, but noticeable differences in community–environment relationships. Lake area was the best predictor for fish species richness in the littoral samplings, while it was poor for offshore samplings. Electrofishing was more efficient than gillnets at catching pike (Esox lucius), eel (Anguilla anguilla), and tench (Tinca tinca), whereas pelagic gillnets were better for catching pikeperch (Sander lucioperca) and perch (Perca fluviatilis). Independently of methods, the total number per unit of effort and weight per unit of effort were generally positively related to summer chlorophyll a, and, for offshore nets, negatively related to average depth. Our results show that sampling restricted to specific habitats within the lakes does not provide a representative of the whole-lake fish community, as all methods miss some important species that other methods capture. How-ever, electrofishing seems to be a fast alternative to gillnets for monitoring fish species richness and composition in littoral habitats of Danish lakes.
Pseudorasbora parva is a small cyprinid fish native to East Asia. In 1982, the occurrence of this species was first recorded from the Thrace region of Turkey and in 1996, from Aksu Stream. In this study, specimens collected from various localities in central and west Anatolia, such as the Sakarya River Basin, Kιzιlιrmak River Basin, and Bakιrçay River Basin, between 1999 and 2004, were used to show the rapid invasion of P. parva in Turkish freshwater systems. This species is regarded as a pest and the rapid P. parva invasion throughout Anatolia could pose a threat to the diversity of the ichthyofauna in Anatolia.
Non-native fishes are often blamed for exerting adverse ecological impacts on native fishes, but the evidence is circumstantial and the true impacts remain largely unknown. This dilemma is particularly acute for freshwater ecosystems of the Mediterranean Region, where a high level of endemism (a biodiversity hotspot) makes native fish extinctions much more likely because of their small natural ranges. The aim of this paper is to review non-native fish impacts, from genes to ecosystem level, in the fresh waters of the Mediterranean Region and identify gaps in knowledge that currently hamper effective conservation and management of native species and ecosystems. Most studies reviewed reported potential impacts rather than realised impact mechanisms, and these were conducted predominantly in the European part of the Mediterranean Region. No studies of realised impacts were found for three of the 15 most introduced fishes, which emphasises the need for evidence-based studies of non-native species impacts.
Salmo rizeensis, new species, is described from the upper part of streams and rivers draining to the south and southeastern Black Sea, and S. coruhensis, new species, from the lower and the middle part of the streams and rivers of the same area. Salmo rizeensis is distinguished by a small size (maximum known size 250 mm SL); a single conspicuous black spot behind eye; black spots on the back and upper part of flank; no black spot on the middle part of body in specimens larger than 200 mm SL; red spots few, organised in three or four irregular rows on middle part of body, distinctly ocellated; maxilla long and narrow. Salmo coruhensis is distinguished by a large size (maximum size up to at least 800 mm SL); 4-17 black spots behind eye (cheek and preopercle) in large adult males; black spots on back, flank and middle part of body in males larger than 200 mm, very few in females smaller than 300 mm SL; number of black and red spots increasing with increasing size (not increasing in S. rizeen-sis); red spots in median part of body, surrounded by irregularly shaped white ring; maxilla short and narrow. The two species occur in sympatry in several streams, and occasionally in syntopy. Molecular analyses (nuclear [ITS1] and mitochondrial genes [cytochrome b]) show that they belong to distinct lineages and support their specific distinctness. In our study, the resident trouts of different drainages are more closely related to each other than to the migratory ones in the same drainages, and vice versa. This contradicts the credo that resident and migratory trouts in a given stream are only 'forms' of the same species with different life histories. We do not extrapolate this to be the case in other drainages and for other species, but this calls for a more cautious treat-ment of the taxonomy, diversity and conservation of trouts at a local level.
Shallow lakes, the most abundant lake type in the world, are very sensitive to climatic changes. The structure and functioning of shallow lakes are greatly impacted by submerged plants, and these may be affected by climate warming in various, contrasting, ways.
Following a space-for-time substitution approach, we aimed to analyse the role of aquatic (submerged and free-floating) plants in shallow lakes under warm climates. We introduced artificial submerged and free-floating plant beds in five comparable lakes located in the temperate zone (Denmark, 55–57 °N) and in the subtropical zone (Uruguay, 30–35 °S), with the aim to study the structure and dynamics of the main associated communities.
Regardless of differences in environmental variables, such as area, water transparency and nutrient status, we found consistent patterns in littoral community dynamics and structure (i.e. densities and composition of fish, zooplankton, macroinvertebrates, and periphyton) within, but substantial differences between, the two regions. Subtropical fish communities within the macrophyte beds exhibited higher diversity, higher density, smaller size, lower relative abundance of potentially piscivores, and a preference for submerged plants, compared with otherwise similar temperate lakes. By contrast, macroinvertebrates and cladocerans had higher taxon richness and densities, and periphyton higher biomass, in the temperate lakes. Several indicators suggest that the fish predation pressure was much stronger among the plants in the subtropical lakes. The antipredator behaviour of cladocerans also differed significantly between climate zones. Submerged and free-floating plants exerted different effects on the spatial distribution of the main communities, the effects differing between the climate zones. In the temperate lakes, submerged plants promoted trophic interactions with potentially positive cascading effects on water transparency, in contrast to the free-floating plants, and in strong contrast to the findings in the subtropical lakes.
The higher impact of fish may result in higher sensitivity of warm lakes to external changes (e.g. increase in nutrient loading or water level changes). The current process of warming, particularly in temperate lakes, may entail an increased sensitivity to eutrophication, and a threat to the high diversity, clear water state.
Throughout the world a number of problems have arisen following the introduction of new fish species; impacts of introductions are not limited to biological and ecological effects but may also have socioeconomic implications. Exotic and translocated fish species have become established in various parts of the inland waters of Turkey since the 1950s. The present paper reviewed ecological and economical effects of introduced freshwater fish of Turkey.
There is a growing recognition of the need to conserve biodiversity that has been conceptualised in the Convention of Biological Diversity. Maintenance of fish species richness is particularly important, because habitat degradation in inland waters continues to accelerate on a global scale. Here we develop empirical models for predicting fish species richness in natural lakes in various geographical regions of the world. In tropical lakes where fish biodiversity is richer than in temperate lakes, fish species richness can be predicted by a few variables such as lake area and altitude. Low fish species richness in most temperate lakes might be due to the effect of glaciation on colonisation and speciation of fishes. In US, Canadian and northern European lakes, lake acidification is one of the important factors influencing fish species richness. Although limnological characteristics influence fish species richness in temperate lakes, lake area and altitude have greater predictive power. This is in contrast to fish species richness in rivers, which can be reliably predicted by basin area. In the power curves, which describe the relationship between fish species richness and habitat size in lakes and rivers, the exponent is always greater in tropical regions than in temperate regions. Because fish biodiversity is greater in the tropics threats to fish biodiversity through habitat degradation are greater than those in temperate inland waters.
This review provides a contemporary account of knowledge on aspects of introductions of non-native fish species and includes issues associated with introduction pathways, ecological and economic impacts, risk assessments, management options and impact of climate change. It offers guidance to reconcile the increasing demands of certain stakeholders to diversify their activities using non-native fishes with the long-term sustainability of native aquatic biodiversity. The rate at which non-native freshwater fishes have been introduced worldwide has doubled in the space of 30 years, with the principal motives being aquaculture (39%) and improvement of wild stocks (17%). Economic activity is the principal driver of human-mediated non-native fish introductions, including the globalization of fish culture, whereby the production of the African cichlid tilapia is seven times higher in Asia than in most areas of Africa, and Chile is responsible for c. 30% of the world's farmed salmon, all based on introduced species. Consequently, these economic benefits need balancing against the detrimental environmental, social and economic effects of introduced non-native fishes. There are several major ecological effects associated with non-native fish introductions, including predation, habitat degradation, increased competition for resources, hybridization and disease transmission. Consideration of these aspects in isolation, however, is rarely sufficient to adequately characterize the overall ecological effect of an introduced species. Regarding the management of introduced non-native fish, pre-introduction screening tools, such as the fish invasiveness scoring kit (FISK), can be used to ensure that species are not introduced, which may develop invasive populations. Following the introduction of non-native fish that do develop invasive populations, management responses are typified by either a remediation or a mitigation response, although these are often difficult and expensive to implement, and may have limited effectiveness.
Turkey (Turkiye) lies at the nexus of Europe, the Middle East, Central Asia and Africa. Turkey's location, mountains, and its encirclement by three seas have resulted in high terrestrial, fresh water, and marine biodiversity. Most of Turkey's land area is covered by one of three biodiversity hotspots (Caucasus, Irano-Anatolian, and Mediterranean). Of over 9000 known native vascular plant species, one third are endemic. Turkey faces a significant challenge with regard to biodiversity and associated conservation challenges due to limited research and lack of translation into other languages of existing material. Addressing this gap is increasingly relevant as Turkey's biodiversity faces severe and growing threats, especially from government and business interests. Turkey ranks 140th out of 163 countries in biodiversity and habitat conservation. Millennia of human activities have dramatically changed the original land and sea ecosystems of Anatolia, one of the earliest loci of human civilization. Nevertheless, the greatest threats to biodiversity have occurred since 1950, particularly in the past decade. Although Turkey's total forest area increased by 5.9% since 1973, endemic-rich Mediterranean maquis, grasslands, coastal areas, wetlands, and rivers are disappearing, while overgrazing and rampant erosion degrade steppes and rangelands. The current "developmentalist obsession", particularly regarding water use, threatens to eliminate much of what remains, while forcing large-scale migration from rural areas to the cities. According to current plans, Turkey's rivers and streams will be dammed with almost 4000 dams, diversions, and hydroelectric power plants for power, irrigation, and drinking water by 2023. Unchecked urbanization, dam construction, draining of wetlands, poaching, and excessive irrigation are the most widespread threats to biodiversity. This paper aims to survey what is known about Turkey's biodiversity, to identify the areas where research is needed, and to identify and address the conservation challenges that Turkey faces today. Preserving Turkey's remaining biodiversity will necessitate immediate action, international attention, greater support for Turkey's developing conservation capacity, and the expansion of a nascent Turkish conservation ethic. (C) 2011 Published by Elsevier Ltd.
This book had its origin when, about five years ago, an ecologist (MacArthur) and a taxonomist and zoogeographer (Wilson) began a dialogue about common interests in biogeography. The ideas and the language of the two specialties seemed initially so different as to cast doubt on the usefulness of the endeavor. But we had faith in the ultimate unity of population biology, and this book is the result. Now we both call ourselves biogeographers and are unable to see any real distinction between biogeography and ecology.
The extinction process of the endemic inland fishes of Turkey, Alburnus akili (gövce) and Pseudophoxinus handlirschi (kavinne) is studied. The assessment is based on the field studies and observations during the last two decades (1990-2010), along with a survey of the literature. The piscivorous effect of Sander lucioperca introduced into lakes Eǧirdir and Beyşehir has been concluded to be the major factor in the disappearance of Pseudophoxinus handlirschi in the early 1970s and of Alburnus akili after 1985.
Cladocerans are valuable indicators of
environmental change in lakes. Their fossils provide
information on past changes in lake environments.
However, few studies have quantitatively examined
the relationships between contemporary and sub-fossil
cladoceran assemblages and no investigations are
available from Mediterranean lakes where salinity,
eutrophication and top-down control of large-bodied
cladocerans are known to be important. Here we
compared contemporary Cladocera assemblages, sampled
in summer, from both littoral and pelagic zones,
with their sub-fossil remains from surface sediment
samples from 40 Turkish, mainly shallow, lakes. A
total of 20 and 27 taxa were recorded in the
contemporary and surface sediment samples, respectively.
Procrustes rotation was applied to both the
principal components analysis (PCA) and redundancy
analysis (RDA) ordinations in order to explore the
relationship between the cladoceran community and
the environmental variables. Procrustes rotation analysis
based on PCA showed a significant accord
between both littoral and combined pelagic–littoral
contemporary and sedimentary assemblages. RDA
ordinations indicated that a similar proportion of
variance was explained by environmental variation for
the contemporary and fossil Cladocera data. Total
phosphorus and salinity were significant explanatory
variables for the contemporary assemblage, whereas
salinity emerged as the only significant variable for the
sedimentary assemblage. The residuals from the
Procrustes rotation identified a number of lakes with
a high degree of dissimilarity between modern and
sub-fossil assemblages. Analysis showed that high
salinity, deep water and high macrophyte abundance
were linked to a lower accord between contemporary
and sedimentary assemblages. This low accord was,
generally the result of poor representation of some
salinity tolerant, pelagic and macrophyte-associated
taxa in the contemporary samples. This study provides
further confirmation that there is a robust relationship
between samples of modern cladoceran assemblages
and their sedimentary remains. Thus, sub-fossil
cladoceran assemblages from sediment cores can be
used with confidence to track long-term changes in
this environmentally sensitive group and in Mediterranean
lakes, subjected to large inter-annual variation
in water level, salinity and nutrients.
Aquatic macrophytes are commonly used to assess the ecological condition of lakes. Little is known, however, about long‐term macrophyte dynamics in shallow lakes. In the absence of historical data, the remains of macrophytes (fruits, seeds and vegetative fragments) found in lake sediments may provide just such information. In order to interpret confidently past change in aquatic plant communities from their sedimentary remains, it is vital to establish the similarity between the contemporary and fossil assemblages.
We investigated the relationship between present lake vegetation and plant macrophyte remains in surface sediments. Thirty‐five shallow lakes, spanning around six degrees of latitude and mostly located in the semi‐arid M editerranean climatic zone of T urkey, were sampled for aquatic plants, surface sediment plant remains and a range of other key environmental variables.
Around 50% of the taxa recorded in the modern vegetation were represented in the sediment. Sedimentary macrofossils of some taxa were under‐ or over‐represented relative to their frequency in the modern vegetation, for example P otamogeton spp. and C haraceae, respectively. Despite this disparity, there was good agreement between the assemblage composition of the modern and sedimentary samples. Furthermore, conductivity and trophic state (as indicated by total nitrogen, total phosphorus and chlorophyll‐ a ) were the environmental variables most clearly correlated with both the contemporary and macrofossil assemblages in these lakes.
We conclude that aquatic macrophyte macrofossils can be used as reliable indicators of ecological status and to determine qualitative changes in assemblages of aquatic plants consequent to environmental change (e.g. in lake trophic status and/or salinity). This may be especially useful for lakes in arid and semi‐arid M editerranean regions, which are particularly vulnerable to hydrological constraints under climate change.
In size-structured populations, interactions are strongly dependent on size-specific foraging and anti-predator capacities of the organism. Conflicting size-specific selection pressures over the ontogeny often have different effects on different species leading to asymmetries in competitive and predator-prey interactions. Habitat complexity is likely to affect such asymmetric interactions due to species/size-specific competitive abilities in different habitats and due to the fact that habitat structural complexity may act differently as a prey refuge for different species. We experimentally analyzed the impact of a piscivorous predator (adult perch, Perca fluviatilis) on performance of juvenile perch and roach (rutilus rutilus) at different levels of structural complexity (no structure, structure forming a partial refuge, and structure forming a complete refuge) in enclosures in an experimental pond. We measured predator diet and growth, prey fish habitat use, survival, diet and growth, and prey resource levels in different habitats.
Prey fish (perch and roach) were found in the diet of piscivorous perch in no refuge and partial refuge treatments. Growth rate of the piscivorous perch decreased with increased refuge efficiency. Juvenile perch increased their proportional use of the structurally complex refuges in the presence of piscivorous perch and the survival increased with increased refuge efficiency (from partial to complete refuge). The diet of juvenile perch changed from predominantly cyclopoid copepods in the absence of predators to predominantly macroinvertebrates in the presence of predators. There was no effect of predator-induced habitat restriction on growth of juvenile perch. Roach survival also increased with increased refuge efficiency in the presence of predators, and roach survival in the refuge treatments did not differ from each other or from the treatments with predators absent. Predator-induced habitat restriction in roach was associated with a decreased growth of roach.
Our results suggest that, compared to juvenile roach, juvenile perch may compensate more for lost foraging opportunity in the open water via increased exploitation of structure-associated prey in refuges. As a result, predator-induced habitat shifts by juvenile perch and roach may alter competitive interactions between the species. On the other hand, structural complexity may form an almost complete refuge for juvenile roach from predators and thereby affect the predator-prey relationships between piscivorous perch and juvenile perch and roach to the advantage of juvenile roach. The demonstrated effects of structural complexity on competitive and predator-prey interactions between perch and roach can be related to the two species' distributions in lakes with different degrees of structural complexity.
Aim To analyse the patterns in species richness and endemism of the native European riverine fish fauna, in the light of the Messinian salinity crisis and the Last Glacial Maximum (LGM). Location European continent. Methods After gathering native fish faunistic lists of 406 hydrographical networks, we defined large biogeographical regions with homogenous fish fauna, based on a hierarchical cluster analysis. Then we analysed and compared the patterns in species richness and endemism among these regions, as well as species-area relationships. Results Among the 233 native species present in the data set, the Cyprinidae family was strongly dominant (> 50% of the total number of species). Seven biogeographical regions were defined: Western Peri-Mediterranea, Central Peri-Mediterranea, Eastern Peri-Mediterranea, Ponto-Caspian Europe, Northern Europe, Central Europe and Western Europe. The highest regional species richness was observed for Central Peri-Mediterranea and Ponto-Caspian Europe. The highest endemic richness was found in Central Peri-Mediterranea. Species-area relationships were characterized by high slope values for Peri-Mediterranean Europe and low values for Central and Western Europe. Main Conclusion The results were in agreement with the 'Lago Mare' hypothesis explaining the specificity of Peri-Mediterranean fish fauna, as well as with the history of recolonization of Central and Western Europe from Ponto-Caspian Europe following the LGM. The results also agreed with the mechanisms of speciation and extinction influencing fish diversity in hydrographical networks. We advise the use of the seven biogeographical regions for further studies, and suggest considering Peri-Mediterranean Europe and Ponto-Caspian Europe as 'biodiversity hotspots' for European riverine fish.
In the past, the genetics of common carp populations has mainly been studied on regional levels using traditional protein markers. We analysed four microsatellite loci of 577 individuals from 22 domesticated, wild and feral populations spanning a geographical area as wide as from Europe through Central Asia to East and South-East Asia. The variability of these loci was much higher than that of the allozyme loci examined in our previous studies. A total number of 143 alleles were recorded across loci ranging from 27 at MFW28 to 47 at MFW7. However, the mean number of alleles per locus was remarkably lower: from 2.50 in a captive stock of River Amur wild carp to 14.25 in a wild population from Lake Arnasaiskie, Uzbekistan, and domesticated Chinese carp from Wuhan. The variability of populations did not show a clear geographical pattern but a highly significant difference was found in allelic richness between the 13 domesticated/captive stocks (average Ar = 4.436) and the nine wild−caught populations (average Ar = 8.221). The prevalence of different alleles in different populations resulted in a high degree of population differentiation: the FST values for all but four pairwise comparisons of Central Asian wild populations were significant. Within geographical regions the DA distances between populations were smallest in Central Asia (average DA = 0.139), intermediate in Europe (average DA = 0.434) and largest in East/South-East Asia (average DA = 0.833). Between geographical regions the European and Central Asian populations showed the smallest distances (average DA = 0.484) whereas the distances of these two regions and East/South-East Asia were almost identical but substantially larger (Europe vs. East/South-East Asia: average DA = 0.801, and Central Asia vs. East/South-East Asia: average DA = 0.806). All populations clustered into only two highly divergent major groups with 91% bootstrap support: Europe/Central Asia and East/South-East Asia. Thus, the microsatellite data also suggest an ancient separation of European/Central Asian from East/South-East Asian carp and a single origin of European carp in Central Asia as already inferred from our previous allozyme and mtDNA RFLP studies. The taxonomic status of subspecies assigned to European (C. c. carpio) and East Asian carp (C. c. haematopterus) is supported. However, because of their close relationship to European carp the Central Asian carp do not deserve a separate subspecies status (C. c. aralensis).
Stepwise multiple regression was used to obtain preliminary insights into the environmental parameters which influence the number of fish species occurring in lakes. Results are summarized as follows: 1. For a sample of 70 lakes and inland seas from throughout the world, surface area and latitude account for about one-third of the variability in fish species diversity. 2. For a subsample of 14 North American lakes, latitude and surface area account for about 90% of the variability in species numbers. The large effect of latitude can be explained in terms of climatic severity and isolation from sources of colonization. 3. For a subsample of 14 African lakes, surface area, depth, and conductivity were primary variables affecting species diversity. 4. For 70 lakes of the world and 14 North American lakes, the slope of the species-area curve was low (z = 0.15-0.16). Apparently this reflects the fact that, whereas a relatively large number of species are available to colonize small lakes, larger ones are impoverished. Most of the latter are recent enough that there has not been time for endemic speciation to reach an equilibrium with extinction. We expect the large lakes of tropical Africa to be the closest to such an equilibrium, and it is encouraging that the slope of the species-area curve for the sample including these bodies of water is quite steep (z = 0.35). 5. On the basis of our data and analyses of species distribution in other insular habitats, four patterns of species diversity are distinguished.
In this study, a great number of works about the systematic of Turkish inland water fishes published since 1856 are reviewed. Besides, the developments and changes that have occured in this field are put forward in the historical process. Based on the results obtained, it has been specified that 236 species and subspecies which belong to 26 families live in Turkish inland waters, and their names appeared in recent publications were listed.
1. We aimed to distinguish the relative contributions of natural and anthropogenic local factors on
patterns of fish diversity in European lakes at different geographical scales.
2. We compiled data from standardised fish monitoring using multimesh benthic gill nets, information
on lake morphometry and on geographical, climatic and anthropogenic pressure variables from
1632 lakes in 11 European countries. By means of regression trees, we determined those natural and
anthropogenic factors and their thresholds that best predicted local fish diversity, density and mean
size. Generalised linear models were used to assess the influence of anthropogenic factors at smaller
geographical and morphometric scales.
3. Local fish species richness and diversity were related mainly to morphometric and (bio)geographical/
climatic variables. Larger and deeper lakes in warm areas tended to be the most species
rich and diverse. Fish density was related mainly to anthropogenically driven productivity but
also was sensitive to geographical/climatic factors. Thus, warmer and shallower lower-altitude
European lakes, which are usually more eutrophic, had higher fish densities than cold and deeper
higher-altitude lakes. Fish size increased with altitude and declined with increasing seasonality and
temperature.
4. After controlling for the natural factors, productivity had a positive effect on fish species richness
and diversity, whereas it negatively influenced fish size.
5. Our results suggest that macroecological patterns of lake fish diversity across Europe are best predicted
by natural factors. The contribution of anthropogenic factors to fish diversity was evident only
via the effect of eutrophication at smaller geographical scales, whereas no effect could be found from
hydromorphological pressures. From an applied perspective, these results suggest that bioassessment
and biodiversity evaluation might be most effectively conducted and interpreted locally, where anthropogenic effects on biodiversity become more apparent. At a macroecological scale, the strong
effect of environmental temperature on most components of fish diversity suggests future changes in
fish diversity as a consequence of climate change.
Pseudophoxinus evliyae, new species, from a small stream near Sogut, Western Anatolia, is distinguished from other Anatolian Pseudophoxinus by an incomplete lateral line, 54-64+2-3 scales in lateral series, 131/2-161/2 scales between lateral line and dorsal-fin origin, a prominent black stripe and a rounded snout and short head. This species vas previously identified as P. fahirae. Pseudophoxinus fahirae is tentatively placed in the genus Chondrostoma. Pseudophoxinus from Lake Burdur and Salda basins are re-examined and identified as P. ninae.
Pseudophoxinus fahrettini, new species, from upper Kopru River drainage, Central Anatolia, is distinguished from other Anatolian Pseudophoxinus by a complete lateral line with 74-85+3-4 scales, the upper lip projecting beyond tip of lower lip, a prominent black stripe and a long snout and pointed head.
Pseudophoxinus hittitorum, new species, is described from Lake Beysehir basin, Central Anatolia. It is distinguished from other Anatolian Pseudophoxinus by a complete lateral line with 84-94 + 1-2 scales, the absence of an epidermal lateral stripe, the dorsal-fin origin behind vertical through the pelvic-fin origin and a flexible last simple dorsal-fin ray.
The southern, western and north-western regions of Anatolia have abundant freshwater resources in the form of rivers, lakes and lagoons. In the past, these aquatic habitats were unpolluted and had very rich fish populations, but some water courses have started to become polluted in the last 20 years. This is because Turkey is a country that is developing very fast, both industrially and in agricultural terms. As a result of the large numbers of major towns and various types of factory, some species have been particularly affected by industrial pollution and generally the populations of fish living in these habitats have greatly diminished in recent years. The waste waters from these sites are discharged via rivers and lakes into the Sea of Marmara, the Aegean and the Mediterranean Seas. Some factories are equipped with filtration systems or purification plants, but at present most have no form of effluent treatment. Twenty species and ten subspecies of fish are described that are endemic to Turkey and neighbouring countries. One endemic species (Tor canis) is now extinct in Turkish waters, and three species (Alosa fallax nilotica, Aphanius fasciatus and Blennius fluviatilis) are endemic to the northern Mediterranean. It is essential as a first priority that conservation measures are taken to protect certain species and subspecies.
1. Fish play a key role in the functioning of temperate shallow lakes by affecting nutrient exchange among habitats as well as lake trophic structure and dynamics. These processes are, in turn, strongly influenced by the abundance of submerged macrophytes, because piscivorous fish are often abundant at high macrophyte density. Whether this applies to warmer climates as well is virtually unknown.
2. To compare fish community structure and dynamics in plant beds between subtropical and temperate shallow lakes we conducted experiments with artificial submerged and free‐floating plant beds in a set of 10 shallow lakes in Uruguay (30°–35°S) and Denmark (55°–57°N), paired along a gradient of limnological characteristics.
3. The differences between regions were more pronounced than differences attributable to trophic state. The subtropical littoral fish communities were characterised by higher species richness, higher densities, higher biomass, higher trophic diversity (with predominance of omnivores and lack of true piscivores) and smaller body size than in the comparable temperate lakes. On average, fish densities were 93 ind. m ⁻² (±10 SE) in the subtropical and 10 ind. m ⁻² (±2 SE) in the temperate lakes. We found a twofold higher total fish biomass per unit of total phosphorus in the subtropical than in the temperate lakes, and as fish size is smaller in the former, the implication is that more energy reaches the littoral zone fish community of the warmer lakes.
4. Plant architecture affected the spatial distribution of fish within each climate zone. Thus, in the temperate zone fish exhibited higher densities among the artificial free‐floating plants while subtropical fish were denser in the artificial submerged plant beds. These patterns appeared in most lakes, regardless of water turbidity or trophic state.
5. The subtropical littoral fish communities resembled the fish communities typically occurring in temperate eutrophic and hypertrophic lakes. Our results add to the growing evidence that climate warming may lead to more complex and omnivory‐dominated food webs and higher density and dominance of smaller‐sized fish. This type of community structure may lead to a weakening of the trophic cascading effects commonly observed in temperate shallow lakes and a higher risk of eutrophication.
Wild common carp from three lakes in Turkey were genetically characterized by examining the variability of four microsatellite loci and the restriction fragment length polymorphisms (RFLPs) of the mitochondrial ND-3/4 and ND-5/6 gene regions. Microsatellite variability did not differ significantly among the three populations and was only slightly lower than that of other wild-caught populations but remarkably higher than that of domesticated/captive stocks found in preceding studies. On the other hand, genetic differentiation between Turkish wild carp was significant and high (FST values ranged from 0.21 to 0.27). PCR-RFLP analysis revealed a total of five composite haplotypes. One of them was the typical European/Central Asian haplotype H1 shared by two of the Turkish populations from Sapanca and Iznik Lakes, respectively. The remaining four haplotypes were very similar to H1 differing in fragment patterns of only one or two restriction enzymes. Thus, present data further support the hypothesis of a single origin of present day European domesticated and wild/feral carp from a common ancestor with Central Asian carp. Considering that wild common carp are extremely endangered or already extinct in many areas of their natural distribution range, the examined Turkish populations represent valuable genetic resources of European carp that should be protected.
Several studies have demonstrated a latitudinal gradient in the proportion of omnivorous fish species (that is, consumers of both vegetal and animal material) in marine ecosystems. To establish if this global macroecological pattern also exists in fresh and brackish waters, we compared the relative richness of omnivorous fish in freshwater, estuarine, and marine ecosystems at contrasting latitudes. Furthermore, we sought to determine the main environmental correlates of change in fish omnivory. We conducted a meta-analysis of published data focusing on change in the relative richness of omnivorous fishes in native fish communities along a broad global latitudinal gradient, ranging from 41°S to 81.5 N° including all continents except for Antarctica. Data from streams, rivers, lakes, reservoirs, estuaries, and open marine waters (ca. 90 papers covering 269 systems) were analyzed. Additionally, the relationship between the observed richness in omnivory and key factors influencing trophic structure were explored. For all ecosystems, we found a consistent increasing trend in the relative richness of omnivores with decreasing latitude. Furthermore, omnivore richness was higher in freshwaters than in marine ecosystems. Our results suggest that the observed latitudinal gradient in fish omnivory is a global ecological pattern occurring in both freshwater and marine ecosystems. We hypothesize that this macroecological pattern in fish trophic structure is, in part, explained by the higher total fish diversity at lower latitudes and by the effect of temperature on individual food intake rates; both factors ultimately increasing animal food limitation as the systems get warmer.
Aim To document the patterns of fish species richness and their possible causes in China's lakes at regional and national scales.
Location Lakes across China.
Methods We compiled data of fish species richness, limnological characteristics and climatic variables for 109 lakes across five regions of China: East region, Northeast region, Southwest region, North-Northwest region, and the Tibetan Plateau. Correlation analyses, regression models and a general linear model were used to explore the patterns of fish species richness.
Results At the national scale, lake altitude, energy availability (potential evapotranspiration, PET) and lake area explained 79.6% of the total variation of the lake fish species richness. The determinants of the fish richness pattern varied among physiographic regions. Lake area was the strongest predictor of fish species richness in the East and Southwest lakes, accounting for 22.2% and 82.9% of the variation, respectively. Annual PET explained 68.7% of the variation of fish richness in the Northeast lakes. Maximum depth, mineralization degree, and lake area explained 45.5% of the fish variation in the lakes of the North-Northwest region. On the Tibetan Plateau, lake altitude was the first predictor variable, interpreting 32.2% of the variation.
Main conclusions Lake altitude was the most important factor explaining the variation of fish species richness across China's lakes, and accounted for 74.5% of the variation. This may stem in part from the fact that the lakes investigated in our study span the largest altitudinal range anywhere in the world. The effects of the lake altitude on fish species richness can be separated into direct and indirect aspects due to its collinearity with PET. We also found that the fish diversity and its determinants were scale-dependent. Fish species richness was probably energy-determined in the cold region, while it was best predicted by the lake area in the relatively geologically old region. The independent variables we used only explained a small fraction of the variations in the lake fish species richness in East China and the Tibetan Plateau, which may be due to the effects of human activity and historical events, respectively.
The information extracted from IMPASSE, DAISIE, FishBase, and FAO-DIAS inventories of alien species were used to draw a list of the 27 most utilized animal alien species for aquaculture and related activities (e.g. stocking, sport fishing, ornamental purposes) in Europe. Three variables have been considered to assess their negative ecological impacts when these species escape from aquaculture facilities: (i) their distribution across Europe (including non-EU Member States); (ii) evidence of their environmental impact in the wild; and (iii) evidence of their being vectors of non-target alien species and other hitchhikers (e.g. pathogens). Drivers of use and mechanisms of dispersal in the wild have been also considered and reviewed. Twenty of the species are freshwater fishes: alien cyprinids and salmonids have been introduced into Europe mainly for food production, sport fishing and ornamental purposes. The most widespread species are the goldfish Carassius auratus and the rainbow trout Oncorhynchus mykiss, established in 29 and 28 European countries, respectively. Notwithstanding their successful distribution in Europe, only the Gibel carp Carassius gibelio and the peneid shrimp Marsupenaeus japonicus were found to have environmental impact in all the countries of establishment. Crayfish and predatory fishes (e.g. catfishes and salmonids) cause major environmental impacts in Europe by outcompeting native species and altering habitat structure. Alien crayfish, Procambarus clarkii and Pacifastacus leniusculus, are responsible for the largest range of impacts (i.e. crayfish plague dissemination, bioaccumulation of pollutants, community dominance, competition and predation on native species, habitat modifications, food web impairment, herbivory and macrophytes removal). Cyprinids (e.g. herbivorous carps) are vectors of diseases and parasites, while salmonids (e.g. Salvelinus fontinalis) often cause genetic impairment of native stocks by hybridization. The importation of alien farmed (target) species frequently leads to the introduction of associated non-target species. The cultures of the Pacific cupped oyster Crassostrea gigas and Manila clam Ruditapes philippinarum were responsible for the introduction of the largest number (60) of non-native invertebrates and algae, often attached to packaging material, fouling the shell or parasitizing bivalve tissues.
1. Using data from 71, mainly shallow (an average mean depth of 3 m), Danish lakes with contrasting total phosphorus concentrations (summer mean 0.02–1.0 mg P L−l), we describe how species richness, biodiversity and trophic structure change along a total phosphorus (TP) gradient divided into five TP classes (class 1–5: <0.05, 0.05–0.1, 0.1–0.2, 0.2–0.4,> 0.4 mg P L−1).
2. With increasing TP, a significant decline was observed in the species richness of zooplankton and submerged macrophytes, while for fish, phytoplankton and floating‐leaved macrophytes, species richness was unimodally related to TP, all peaking at 0.1–0.4 mg P L−1. The Shannon–Wiener and the Hurlbert probability of inter‐specific encounter (PIE) diversity indices showed significant unimodal relationships to TP for zooplankton, phytoplankton and fish. Mean depth also contributed positively to the relationship for rotifers, phytoplankton and fish.
3. At low nutrient concentrations, piscivorous fish (particularly perch, Perca fluviatilis ) were abundant and the biomass ratio of piscivores to plankti‐benthivorous cyprinids was high and the density of cyprinids low. Concurrently, the zooplankton was dominated by large‐bodied forms and the biomass ratio of zooplankton to phytoplankton and the calculated grazing pressure on phytoplankton were high. Phytoplankton biomass was low and submerged macrophyte abundance high.
4. With increasing TP, a major shift occurred in trophic structure. Catches of cyprinids in multiple mesh size gill nets increased 10‐fold from class 1 to class 5 and the weight ratio of piscivores to planktivores decreased from 0.6 in class 1 to 0.10–0.15 in classes 3–5. In addition, the mean body weight of dominant cyprinids (roach, Rutilus rutilus , and bream, Abramis brama ) decreased two–threefold. Simultaneously, small cladocerans gradually became more important, and among copepods, a shift occurred from calanoid to cyclopoids. Mean body weight of cladocerans decreased from 5.1 μg in class 1 to 1.5 μg in class 5, and the biomass ratio of zooplankton to phytoplankton from 0.46 in class 1 to 0.08–0.15 in classes 3–5. Conversely, phytoplankton biomass and chlorophyll a increased 15‐fold from class 1 to 5 and submerged macrophytes disappeared from most lakes.
5. The suggestion that fish have a significant structuring role in eutrophic lakes is supported by data from three lakes in which major changes in the abundance of planktivorous fish occurred following fish kill or fish manipulation. In these lakes, studied for 8 years, a reduction in planktivores resulted in a major increase in cladoceran mean size and in the biomass ratio of zooplankton to phytoplankton, while chlorophyll a declined substantially. In comparison, no significant changes were observed in 33 ‘control’ lakes studied during the same period.
1. We performed two field experiments using different cage sizes to determine the direct and indirect effects of carp on macrophytes and invertebrate community composition in a shallow lake.
2. The presence of carp produced a significant decrease in macrophyte abundance, changes in species composition and decreased abundance and diversity of invertebrates in small (2.5 × 2.5 × 2.0 m) cages. In large exclosures (15 × 5 m), only macrophyte stem length was significantly affected by carp.
3. There was considerable variation in the macrophyte and invertebrate responses to carp on different sides of the lake in the large exclosures, suggesting that wind and wave action are also important variables affecting macrophyte growth and persistence.
4. The data suggest that carp can significantly affect species abundance and diversity of macrophytes and some macroinvertebrates.
In order to establish a fish-based typology of Italian lakes and identify possible reference and indicator fish species for
each lake type, we analysed historical data on fish assemblages of all Italian natural lakes >0.5km2 from the period prior to the major decline in water quality in the 1950s. General linear regression models showed the ecoregion
and lake altitude being the best predictors of fish species richness. The number of species was significantly higher in the
Alpine than in the Mediterranean ecoregion. Among Alpine lakes, the number of fish species increased significantly with lake
volume whilst decreased with altitude. In the Mediterranean lakes, none of the selected parameters was significant. Cluster
analysis of fish assemblages (presence/absence) divided the lakes of the Alpine and Mediterranean ecoregions into four and
two types, respectively. Pike (Esox lucius), rudd (Scardinius erythrophthalmus) and tench (Tinca tinca) were the main indicator species for the small and mostly shallow lakes in both the Alpine (Type 1) and Mediterranean (Type
6) ecoregions, minnow (Phoxinus phoxinus) for the alpine high altitude lakes (Type 2) and landlocked shad (Alosa fallax lacustris), European whitefish (Coregonus lavaretus) and burbot (Lota lota) for the large and very deep alpine lakes (Type 4). The European whitefish was the only indicator species for the deep Mediterranean
lakes (Type 5). These species and associated fish assemblages may be useful indicators in future assessments of the ecological
status of Italian lakes according to the European Directives (2000/60/EC and 2008/105/EC).
KeywordsFish fauna–Biodiversity–Bioindicators–Reference conditions–Biomonitoring–Pollutants
The aim of this study is to examine the impact of man’s interventions on the present day distribution of fish in a mountain area in southern Norway, the Atna river system. River Atna originates in the Rondane mountains at altitudes of nearly 1600 m a.s.l., and joins River Glomma at 300 m a.s.l. There are 98 lakes in the watercourse (701–1565 m a.s.l.). Lake Atnsjøen is the largest lake (5.0 km2). Data on the occurrence, origin and status of fish in lakes were obtained by means of interviews, questionnaires and written sources. Occurrence in rivers and streams was surveyed by electrofishing. While the lower reaches of River Glomma contain most of the freshwater fish species found in Norway, the Atna watercourse has a poor fish fauna. Physical conditions, e.g. steep river gradients and several impassable waterfalls have prevented fish from reaching most lakes and river stretches after the deglaciation some 6000 years ago. Five species of fish are regarded as native to the area; brown trout (Salmo trutta), Arctic charr (Salvelinus alpinus), grayling (Thymallus thymallus), Siberian sculpin (Cottus poecilopus) and European minnow (Phoxinus phoxinus). Although only native species are found in the area, the present distribution of these species within the watercourse is to a very large extent a result of human interventions during the past 100–130 years. Brown trout were originally found in the main branch of the river, including Lake Atnsjøen and a few small lakes (n
Turkey’s natural and ecological situations are very suitable for aquaculture. Turkey also has a wide variety of freshwater and marine species comprising trout, carp, sea bass, sea bream, turbot, mussel, crayfish, etc. The total production of fish and shellfish was 646,310 tons in 2008. The contribution of freshwater catch to total fishery production is relatively small. Capture fisheries production amounted to 494,124 tons whilst aquaculture production was 152,186 tons in the same year. In Turkey, Engraulis encrasicholus (anchovy) is the main caught sea fish species. Fisheries in the Black Sea are the most important fishery by far and show the greatest variations in total catch. Alburnus
tarichii (a local species belonging to Cyprinidae) and Cyprinus carpio (the common carp) are the most important species caught from freshwaters. Aquaculture is going to play an increasingly important role in the Turkish economy, as fishery products are the only products of animal origin that can be exported to the EU. There has been a fast increase in the aquaculture production in Turkey with the implementation of scientific and technological modernization. For example, total aquaculture production for 1986 and 2008 was 3,075 and 152,186 tons, respectively. The percentage of aquaculture in total fish production has been rising every year. The ratio of cultured fish production to total fish production was 1.5% in 1990 s, 13.57% in 2000 and more than 20% in 2005. It was 23.55% in 2008. Trouts are the main cultured freshwater fish species. Raceways and floating cages are employed in culture of trout. Carps are also important cultured freshwater fish species. Sea bass and gilthead sea bream are grown marine fish species. Floating cages, off-shore and earthen ponds are used for marine fish species culture. There has been an increase in fishery exports and imports in recent years. It was more than US 233 million. However, aquaculture production is still far away from the production targets and fisheries sector is not an important part of the economy at present.
Seventy species of exotic or transplanted fish species have been introduced into this region, 60% of them in the last 40 years. The effects of these introductions on endemic species have rarely been described. The few exceptions are: hybridization of Salmo marmoratus with Salmo trutta; the extinction of three endemic species of Phoxinellus in a Turkish lake owing to the introduction of Stizostedion lucioperca; and the spatial displacement of Aphanius in sites where Gambusia affinis occurs. A further phenomenon possibly attributable to the introduction of exotic fish is the increased turbidity in Lake Mikri Prespa following the introduction of Carassius auratus. Because of the paucity of information, the effects of introductions on endemic species remain controversial. It is therefore essential to initiate conservation action plans, for each catchment in wetland areas rich in endemic fish. An awareness campaign directed at land managers and decision-makers on the role and importance of fish in the functioning of aquatic ecosystems must also be undertaken very soon.
The Poisson regression model is frequently used to analyze count data. Pseudo R-squared measures for Poisson regression models have recently been proposed and bias adjustments recommended in the presence of small samples and/or a large number of covariates. In practice, however, data are often over- or sometimes even underdispersed as compared to the standard Poisson model. The definition of Poisson R-squared measures can be applied in these situations as well, albeit with bias adjustments accordingly adapted. These adjustments are motivated by arguments of quasi-likelihood theory. Properties of unadjusted and adjusted R-squared measures are studied by simulation under standard Poisson; over- and underdispersed Poisson regression models and their use is exemplified and discussed with popcorn data.
Abstract – We examined the relative contribution of environmental heterogeneity and dispersal limitation on freshwater fish community composition in 18 Greek protected lakes and reservoirs. Environmental heterogeneity was measured by spatial pattern metrics (calculated by digital map processing, e.g., patch richness density, area-weighted mean patch area), altitude, maximum lake depth and trophic status. Dispersal limitation was measured by straight-line distances among lake centres. Ecosystems were clustered according to species composition. We examined the correlation of similarity in species composition among ecosystems with that of environmental heterogeneity and with straight-line distances, for the entire dataset, as well as for the occurring clusters. Fish species richness increased with ecosystem area and decreased with altitude. The clusters identified (aquatic ecosystems of Northern vs. ecosystems of Western Greece), implied an underlying biogeographical pattern as defined, with Pindus range acting as a natural barrier. Between ecosystems similarity, based on fish species composition, showed a weak to insignificant correlation with environmental heterogeneity, but was significantly correlated to dispersal limitation for the entire dataset as well as within each occurring cluster. Thus, natural barriers, species biogeography and dispersal limitation played a more significant role in shaping freshwater fish communities than environmental heterogeneity.