An overview of electronic tags that can be used in fish research is given, including radio and acoustic transmitters, data storage tags (DST, also termed archival tags), pop-up satellite archival tags (PSAT) and passive integrated transponder tags (PIT-tag). Fish telemetry is a term used to describe the application of these methods. Typically, an electronic tag is attached to a free-swimming fish, and information on position, movements and/or measurements of environmental and physiological parameters can be recorded wirelessly by use of a mobile receiver or stationary loggers. For most methods, the fish need not to be recaptured to achieve data. However, DSTs record and store information on environmental and/or physiological parameters in the tag, and therefore need to be retrieved for downloading data. In the case of PSATs, stored data is transferred to satellites when the tag loosens from the fish and pops up to the surface, and in addition, the pop up position is recorded. The developments of telemetry methods have provided opportunities to reveal previously unknown information on fish behavior, habitat use and migrations in fresh water, estuaries, near-coastal areas and oceans, especially since extensive longterm data can be collected repeatedly from individual fish. Detailed information on fish behaviour and migrations is needed to better understand, protect and manage fishes in freshwater and marine systems. The development of successful management measures depends on knowledge of where fish reside and migrate during the day, season and year. There has been a tremendous increase in the use of electronic tagging methods, especially during the last 10-20 years. In addition to descriptive and ecological studies, the methods have been used to assess effects of for instance hydropower production, other river regulations, migration barriers, protected areas, fishing regulations, catch-and-release angling, hatchery-rearing, fish aggregating devices (FADs), water pollution and aquaculture. The main methods for attaching electronic tags to fish are 1) surgical implantation in the body cavity, 2) external attachment, and 3) gastric insertion via the mouth. Potential negative handling effects are inflammations, infections, tag expulsion, altered behavior, decreased swimming performance, reduced feeding, reduced growth and increased mortality. The catch, handling and tagging procedures should have minimal effects on the fish. If not, an anomalous behaviour caused by the tagging may be recorded instead of the natural behaviour, and the study is a failure from a scientific point of view. Furthermore, optimal anaesthetic and tagging methods are required to meet the ethical standards for use of experimental animals, and to ensure fish survival and welfare.

The European catfish, Silurus glanis, is native to eastern Europe and western Asia and is among the largest freshwater fish in the world. Despite its increasing economic importance and its frequent introductions, the ecology and life-history of this species is poorly known due to the difficulty of sampling such a large species in large rivers and standing waters. Our study provides the first data on age and growth of this species in Turkish waters, where it is native. We report the length-weight relationships and age and size structure of this population, which were significantly different between females and males. A marginal increment analysis indicated that annulus formation occurred between May and June. The estimates of three growth functions (von Bertalanffy, logistic and Gompertz) are reported, with the von Bertalanffy growth providing a better fit and more realistic parameter estimates. Growth rates were significantly higher in males than in females and were overall higher compared to other native populations but similar to introduced populations of similar latitudeEGB was supported by the Spanish Ministry of Science (projects CGL2009-12877-C02-01 and Consolider-Ingenio 2010 CSD2009-00065)

The study describes some key elements of the reproductive biology, including spawning season, age at sexual maturity, fecundity and egg diameter of the native brown trout, Salmo trutta macrostigma, in a tributary of the Ceyhan River. A total of 197 brown trout (118 females and 79 males) were captured in 2000-2001 by electric fishing. In observations on monthly changes, the gonadosomatic index (GSI) and the monthly frequency distribution of egg diameter confirmed that spawning lasted from November to January. Some 27.7% of the females and 62.5% of the males attained sexual maturity in their second year. The smallest fork length (FL) of brown trout attaining sexual maturity was 17.4 cm for males and 17.8 cm for females. Mean fecundity in age groups II, III, IV and V were 360, 452, 693 and 1283 eggs per female, respectively. One 9-year-old female had a unique 3232 egg count. The mean fecundity of the sampled population was 554 eggs per fish, positively correlated with the FL (mm) (R ¼ 0.8227 ) and body weight (R ¼ 0.8130). The diameter of mature eggs in the spawning season ranged from 3.250 to 5.930 mm, with a 4.146 mm average. Mean egg diameter in age groups II, III, IV and V in the spawning season were 0.813, 3.799, 4.663 and 5.243 mm, respectively. Fecundity, egg weight and diameter were statistically different in all age groups.

Diet composition and prey selection of pike (Esox lucius) were studied in Ç ivril Lake, Turkey. The lake is eutrophic in character with a surface area of ca. 64 km )2 and mean depth of 3 m. Stomach contents of 409 specimens were collected between October 2003 and April 2005. Pike diet included 10 prey fish species, two Crustaceae, four Insecta, one Hirudinae and one Amphibia. Feeding was homogeneous, with most pike specializing in prey fish and a few pike specializing on miscellaneous items. Feeding activity varied by season and ontogeny. Stomach fullness and the percentage of fish with prey were highest in spring and in small pike, while feeding intensity was lowest in winter and in large sized pike. Diet composition was dominated by fish, including Carasius gibelio, Chondrostoma meandrense, Esox lucius, Gambusia affinis, Gobio gobio, Hemigrammocapoeta kemali, Leuciscus cephalus, and Tinca tinca. Crustacea were also a significant component in spring and in small sized pike. The most important prey items were C. meandrense, Gammarus sp., H. kemali, and L. cephalus. Pike feeding in winter and summer was homogeneous, specializing mainly on fish as prey, while the diet in spring and autumn was heterogeneous with some pike specializing on Gammarus sp. Cannibalism at 8.7% was observed only in the large sized pike (>40 cm). Pike strongly preferred C. meandrense (Selectivity index V = 0.372; v 2 = 27.739; P < 0.01), G. gobio (V = 0.192; v 2 = 7.350; P < 0.01) and T. tinca (V = 0.146; v 2 = 4.257; P < 0.05) despite their low abundance in the lake. Hemigrammocapoeta kemali was the most abundant prey fish in the environment; however, it was a negatively selected food item (V = )0.358; v 2 = 25.642; P < 0.01). Cyprinus carpio also inhabits the lake, but was not preferred by pike (V = )0.056; v 2 = 0.625; P > 0.05). Accordingly, the aims of the study were to (i) describe pike diet composition; (ii) determine seasonal changes in different size groups; (iii) investigate prey selection by pike in Ç ivril Lake; and (iv) compare the results with data from other lakes. Materials and methodsÇ ivril Lake is a large wetland lake (area: 64 km )2 , mean depth: 3 m) located in the Bu¨yu¨kmenderes River basin in western Turkey and also known as Is¸ıklı Lake (Fig. 1).

Fish fauna in the upper and middle Ceyhan River basin were investigated with the distribution and systematical determination from May 2001 to April 2004. The fish specimens were obtained by electro fishing and gill nets from two lakes, two reservoirs and 18 streams. A total of 2,414 specimens were collected and 1,156 of these were investigated diagnostic characteristics. Twenty species belong to 10 families were determined. Salaria fluviatilis present stations which under 750 m altitudes while Anguilla anguilla was not present in the upper Ceyhan River basin. S. t. macrostigma was also determined in the streams and river located between 720-1,474 m altitudes. Capoeta angorae, Garra rufa and Alburnus orontis were showed a large distribution in the Ceyhan River system. Gambusia affinis and Clarias gariepinus were determined only in Gavur Lake canals and Kumaşır Lake. Acanthobrama sp. only presented in Sır Reservoir, Silurus glanis and Squalius kottelati presented in Sır lake canals and Menzelet lake reservoir, Cobitis evreni and Aphanius mento were determined in the vegetative areas. Anguilla anguilla bireyleri yukarı Ceyhan havzasında bulunmaz iken Salaria fluviatilis bireyleri 750 m rakımı altındaki istasyonlarda mevcuttur. S. t. macrostigma bireyleri ise 720 ile 1.474 m rakımdaki akarsu ve çaylarda bulunmaktadır. Capoeta angorae, Garra rufa ve Alburnus orontis Ceyhan nehir sisteminde çok geniş bir dağılım göstermiştir. Gambusia affinis ve Clarias gariepinus sadece Gavur Gölü kanalları ve Kumaşır Gölü'nde belirlenmiştir. Acanthobrama sp. sadece Sır Baraj Gölü'nde; Silurus glanis ve Squalius kottelati Sır Baraj gölü kanallarında ve Menzelet Baraj gölünde, Cobitis evreni ve Aphanius mento ise bitikisel floranın olduğu lokalitelerde belirlenmiştir.Anahtar Kelimeler: Ceyhan Nehir havzası, balık faunası, dağılım.