Research Article
Abundance and Ecology of the Freshwater Fish in Trabzon Region
Karadeniz Technical University, Faculty of Art and Sciences, Department of Biology 61080 Trabzon, Turkey
Investigations of the fresh water fish of the East Black Sea region are rather limited. The first study was done by Abbolt in 1835. In that study, he mentioned some sea fish and Salmo trutta labrax which were collected from Trabzon region. From 1835 to 1943 the fresh water fish of the East Black Sea region were not investigated in detail. From 1943 to 1987 foreign and Turkish researchers visited this region. A few fish were collected from the country side by the researchers. So, they have published scientific articles about the freshwater fish of Trabzon region (Berg, 1949, Koswing, 1954; Slastenenko, 1956; Ladiges, 1969; Kux and Steiner, 1972; Elvira, 1987; Kuru, 1971a,b, 1975, 1980, 1981). Until now there has not been any study about environmental parameters for the research area.
The work is planned to have a broad perspective including the freshwater fish, their abundance and certain environmental parameters in the research area. In addition, the migration of Salmo trutta labrax, which is very important of food source for local people, was examined. As we know, the population of Salmo trutta labrax in this region is decreasing continuously (Kutrup, 1993). Lelek (1988), has examined the migration of Salmo trutta labrax from Trabzon and Rize, but he did not catch any roving Salmo trutta labrax. He caught only the stream form of Salmo trutta labrax.
Samples were collected between March and August in 1996 from the stations, which were different as regard to the point of biological features in Trabzon (Fig. 1). Stations were determined by taking the low, middle and upper parts of streams into consideration. Samples were collected from approximately 500 m2 for every steation. The number and weight of the species caught from stations were determined and than %n and %g were calculated. Finally, the abundance of the species for every station was determined.
Electric shocker was used to collected fish materials. The energy of electric shocker was adjusted to 600 V. Because of the low conductivity, we had to enlarge cathode.
First, collected fish were fixed at 5% formaldehyde, and than preserved in 70% alcohol.
YSI 600 was used to determine dissolved O2, pH, temperature and conductivity. Suitable props were changed for every physical parameters. Three values of these parameters were taken into consideration to find average value for each station.
Fig. 1: | Sampling Stations in the Research Area (1: Derekoy, 2: Kalkan, 3: Dumlusu, 4: Camlibel, 5: Haskoy, 6: Pervane, 7: Dagbasi, 8: Findikli, 9: Catak, 10: Ikisu, 11: Incesu, 12: Macka, 13: Akarsu, 14: Derecik 15: Dogankoy, 16: Guneysu, S: Stream |
The bottom and the flow of streams were observed and tata were recorded. Altimeter was used to measure the altitude.
A total of twenty species were collected from the research area. From these eleven species were directly from freshwater origin and nine species were from sea origin.
According to species density and number, Cyprinidae, known as white fish, are dominant in either low or middle parts of the area of the streams.
In addition to sea origin fish, Chaslcalburnus chalcoides was caught from place close to the joining point to the sea water of Iyi and Sogutlu streams.
Table 1: | Some environmental parameters in the research area (D.O2 Dissolved oxygen, Cond. Conductivity) |
Table 2: | The biometrical values belong to the fish species in the research area (n: Number of samples, g: Mean weight of species, Min. And Max; Minimum and Maximum values, X: Mean, SD: Standard Deviation, SE: Standard Error of the Mean) |
The specimens of Leuciscus cephalus were only caught from the lower parts of streams, which had sandy bottom and medium flow water. Capoeta tinca and Alburnoides bipunctatus fasciatus had high population density at the middle parts of the streams. Especially Capoeta tinca had the highest population at the middle part of Kara stream. Barbus plebejus escherichi and Capoeta tinca were rarely caught from the upper parts of the streams. These species prefer medium flow water. Salmo trutta labrax, prefering rapid flow water, was only caught from the upper parts of the stream. Gobiuseurycephalarges was collected from all parts of the streams, Eudontomyzon mariae was collected from Kara and Iyi streams. It preferred shallow streams with muddy-sandy bottoms (Kutrup, 1993). However, Chondrostoma colcicum and Cobitis taenia were only collected from Iyi stream.
According to speciess density, Kara stream has the highest species number, with fourteen species. Kara stream has a puddle of is 200 meter length and joins directly to the sea. This characteristic Puddle does not appear in the other streams. As a result of this, half of species collected from this stream are sea origin. These fish enter this area either for feeding or reproduction. Eudontomyzon mariae and Atherina boyeri enter this area for reproduction, Mugil and Gobius species for feeding (Kutrup, 1993). Many young Mugil cephalus, Mugil auratus and Atherina boyeri samples were caught from this region. Gambusia affinis, introduced to marches near Kara stream in 1961 in order to fight mosquita, was collected from these places later.
The number of species and average weight of each individuals in every station were shown in Table 2. As it was seen in Table 2, Barbus plebejus escherichi has the highest average number of individuals that is 20.50. Capoeta tinca and Salmo trutta labrax came after this species. Chaslcalburnus chalcoides and Leuciscus cephalus have the same average value of n (15.63). The lowest aveage value of individual number was 2.50 and seen in Gobius fluviatilis. When we compare the %n values, Salmo trutta labrax has the highest value that is 44.47. The reason of this situation the stations that Salmo truatta labrax were found. The other species were rarely found in this station. This state is also seen in %g values. Just as Salmo trutta labrax has a very highest value of %g values (81.83). The lowest values of %g was seen in Gobius fluviatilis (1.25). Gobius eurycephalarges was seen mostly among the other Gobius species. Two Mugil species, Mugil cephalus ad Mugil auratus that enter freshwater from sea, have similar %n and %g values.
As it was seen in Table 2, Cyprinidae species were mostly dominant and only Salmo truatta labrax-from Salmonidae can live among these fish. Eudontomyzon mariae, Chondrostomata colhicum, Cobitis taenia, Gambusia affinis and Gobius batrachocephalus that was only caught in 1-2 stations was out of this biometrical analysis.
Environmental parameters were found optimal for all fish but only the dissolved O2 from the Haskoy was a critical value. Salmo trutta labrax appears to have the capacity of living under these conditions for a long time. Dissolved O2 was found rather low at the lower regions of Kara, Solakli, Sana, Degirmen and Fol streams compared to the other stations. These regions were not suitable for Salmo trutta labrax, because the speed of the water at these area was decreasing. It was also observed that the amount of dissolved O2 of the upper and lower parts of Yanbolu and Sogutlu is similar to each other (Table 1). That is why these streams are suitable for Salmo trutta labrax. Until May, Salmo trutta labrax was caught from the main branches of certain streas. After May it was only caught from the side branches of the streams, due to the current which is due to the smelting of snow and the increase of rain in May. At this time Salmo trutta labrax were collected from the lower parts of Yanbolu, Iyi and Sogutlu streams.
Because of low dissolved material the electrical conductivity of the streams was found to be low (Table 1). For this reason the cathode was enlarged. These streams with this property may be compared with the Alps rivers (Lelek, 1988). The conductivity obtained in this study was found lower than the conductivity found in Sakarya basin by Erkakan in 1979. Only the conductivity in Hamam stream is near to our conductivity value. This shows that streams in Trabzon has relatively low dissolved material. For this reason the cathode was enlarged. In addition, Erkakan stated that Barbus plebejus prefer 400-500 MHOS/cm., but, conductivity found in this study has no effect on this species. In addition to Barbus plebejus, Capoeta tinca has also the capacity of living under different conductivity values as the samples of this species in Sakarya basin. Salmo trutta labrax, a valuable fresh water fish for local people, prefers low conductivity (106-130 MHOS/cm.) and medium pH values (7-7.9). Leuciscus cephalus prefer generally low conductivity (97-98 MHOS/cm.) and low oxygen level (6.3-7.3 mg/l). The pH values determined in this study have no effect on this species. Alburnoides bipunctatus fasciatus prefers high conductivity (97-98 MHOS/cm.) and low oxygen level (6.3-7.3 mg/l). The pH values determined in this study have no effect on this species. Alburnoides bipunctatus fasciatus prefers high conductivity (142 MHOS/cm.) and pH values (7.3-8.6) and medium oxygen level (8.4-9.8 mg/l) (Table 1).
Because of the narrow valley in the research area, roads can be done by filling the shore of the streams. As a result of this, the shore of the streams are filled with the reef of rock. So, streams get narrow and deeper. That is why the speed of water increases and flora of the shore of the streas are damaged. The water is also become rough because of continually filling work. Consequently, natural food sources such as benthic invertebrates are damaged. For this reason this area is not convenient for breeding. If they lay at this regions, eggs are damaged or vanished.
During the study period two sea trouts were caught by chance. One of them was collected from Yanbolu, the other from Sogutlu stream. These streams were observed to be significant as regard to high dissolved O2 (13.1 and 14.1 mg/l.) and shore vegetation was not damaged. Although Kara and Iyi streams was joined to the sea water, the sea trouts were not collected in these streams, because Kara stream had a puddle. So, at this area Kara stream has not a rapid current and the amount of dissolved O2 (6.3 mg/l.) was less than the other streams. But Iyi stream was suitable for sea trout to enter.
Sea trout was caught from the mouth of Iyi, Yanbolu, Solali and Sogutlu streams between March and May. Two of them were caught from Yanbolu and Sogutlu in June. Unfortunately not any sea trout caught after June from the streams.
The area of Trabzon is usually wet in all seasons where the average number of rainy days per months is 14. Due to the mountains nature of the Black Sea Region streams are short and flowing like cascate in their deep beds. Close to the sea they flow through a low land where the stream beds are rather shallow and the slopes are plain. The fish species prefer such water are dominant in this area. Eudontomyzon mariae, Cyprinus carpio and Cobitis taenia which do not prefer current water are only caught from the pond which is located at sides of the streams. Due to high current the bottom of the streams are stony or gravelly, but close to the sea water beds are relatively sandy. Only Capoeta tinca, Leuciscus cephalus and Eudontomyzon mariae were caught in the sandy area of the streams but the other species were caught in stony or gravelly parts.
Kara stream is the only streams where the water in the stream mingles with the sea water, but other streams mix only in the sea. Depending on the Colchin species, Eudontomyuzon mariae and Condrostomata colhicum, the number of the species in the east region are high than the west parts (Elvira, 1987).
The number and amount of the fish caught from caught from each station do not bring up the real quantity in the streams. Because samples were collected from a region of 500 m2 for every station. When comparing the fishes collected from each station some species had the highest population density. It shows that these species can be sufficiently produce and the rate of the hunting population density. It shows that these species can be sufficiently produce and the rate of the hunting are respectively low, and the rate of the young fishes are dominant as normal populations. Haskoy station has the lowest pH ad dissolved O2 value. At this area the water is hardly moving due to domestic pollution and also the slope is almost plain. This station is not suitable for all species living in Trabzon. Dagbasi station has the lowest temperature (8.4 C) and respectively high dissolve O2 (13.5 mg/l.). Thats why this station are rather suitable for Salmo turutta labrax.
Due to decreasing of hunted fish from the Black Sea in the recent years, the freshwater fish get more important. This study will be a written source for people that have been producing Salmo trutta labrax. Also it will be a source about fish that can be produced later.
I would like to express my sincere thanks to Karadeniz Technical University for funded this research. I wish also thank to fishermen, Adil Ucar for his help during investigation.