It is believed that historically seatrout spawned in all the larger streams and rivers between the town of Giresun and the Soviet border, i.e., those waters flowing into the eastern part of the Turkish Black Sea coast. All the major rivers in this area were therefore visited and examined with a view to assessing their suitability both for natural reproduction of fish and for siting seatrout hatcheries.
Physically, most of the rivers in this region are similar in that they are short (50 km or less) and can be divided into two distinct zones:
A relatively short, low-lying section adjacent to the river mouth. In this coastal strip the slope of land is less steep than further upstream. Those rivers which have been left unmodified or little modified in this zone show signs of periodic changes in their course, and spread to cover a much wider bed at times of flood. However, in most cases the General Directorate for Water (DSI) has carried out engineering work in this zone to confine the flow to a deepened, straightened channel and thus avoid flooding of adjacent agricultural land.
Upstream of the above zone, the river gradient quickly becomes steeper as the land rises into the mountains. In this second zone the valley is typically narrow and steep-sided, leaving little space alongside the river for construction of roads, houses or fish farms. Dwellings are frequently built either on top of the hills or clinging precariously to steep hillsides. Where roadbuilding or other engineering work has been done, or where natural forest has been removed to make way for agricultural use, land slips and erosion are common. These greatly increase the turbidity of the river water at times of rain and during snow-melt, and this is probably a significant factor in reducing the survival of seatrout eggs and fry.
The substrates in most rivers are composed of stones and gravels of various sizes. However, the trend towards straightening and channelization of river-beds has tended to reduce the availability of pools and other quiet areas where gravel substrates are suitable for trout spawning, and increase the proportion of river area in which flows are torrential and substrates of large rocks and boulders.
It was the consultant's strong impression that the rivers to the east of the Firtina (see Fig. 2) suffer much less from erosion and consequently higher water turbidity than those further west, and this observation is confirmed by the long-term measurements taken by the DSI.
The following observations were made on specific rivers, working westward from the Soviet border:
Kapistre River. Every time this river was visited the water was good, clear and clean right down to the sea. The lower reaches have been channelized for a distance of 4–5 km for flood prevention. Above this is a zone cultivated predominantly for tea production. In this zone one small site potentially suitable for a trout hatchery was found (see below). Above the tea zone the sides of the valley become very steep, and the road is reduced to a track passable by a 4-wheel-drive vehicle in most seasons. No further possible building sites were found on the main river. However, on a small side branch which joins the main river close to the sea, there is one very small private fish farm reproducing less than 1 t/year of rainbow seatrout for local sale. Due to the limited water supply and shortage of building space there is little scope for significant expansion.
The substrate in much of the river is composed of stones and gravel of various sizes in many places suitable for spawning of salmonid fishes. Local commercial and sport fishermen confirmed that seatrout definitely use the river for spawning in significant numbers. Members of the fishermen's cooperative at Arhavi admitted to catching about 50 fish per year in the river or close to its mouth.
Çağlayan River. This river has a good, clear and clean flow of water at most times. A little channelization work has been done near the sea, and above this is a flattish zone in which the course of the river is subject to change during floods. In this area tea and nuts are cultivated. Approximately 8 km from the sea is a commercial seatrout farm producing about 10 t/year of rainbow trout. At this farm and nearby are excellent sites suitable for development to produce seatrout smolts (see below). Above the fish farm and Çaglayan village the valley becomes steep-sided, there is no room for fish-farm building and the road is reduced to a 4-wheel-drive track. Compared with other rivers in the region there is little agricultural development in the Çağlayan catchment, most of the steep hillsides being covered with native bush. Consequently, there is little sign of erosion, and the river is less prone to increases in turbidity than most others. There are no significant side branches, and the river bed is suitable for salmonid spawning in many places, especially in the numerous pools of various sizes upstream of Çaglayan village.
Local fishermen confirm that seatrout use the river in significant numbers, and many believe the Çağlayan is the most important spawning area for this species in Turkey (others place it second to the Firtina - see below). Local fishermen claim at least 100 adult fish are caught by nets in the approaches to the river during the spawning migration, and other fish are taken in the river by rods, nets and explosives.
Findikli (or Arili) River. This is another river in which the water is normally of good quality, and clear, but the flow is less than in the Çağlayan. The stretch near the sea is now channelized, but previously contained several natural lakes in which local people fished seatrout. Above the straight, artificial channel is a natural, winding section of river in which one potential fish farm site was identified (see below). Tea and nuts are cultivated in this area. The river has two main branches, the eastern one being served by an unsealed road. Upstream the valley becomes steep, with no further suitable building sites. Again, a significant part of the river substrate is of gravel suitable for salmonid spawning, and local fishermen reported that seatrout do use the river. Occasional catches are made, but quantities could not be estimated.
Firtina River. Though thought by many people to be the most important Turkish river for seatrout spawning, the water of the Firtina is now often quite turbid for many kilometres upstream. This is said to be mainly due to road-building projects, but there is also evidence of frequent land slips and erosion due to agricultural activity following the clearing of forest up to the town of Çamlehensin. Two main branches join near the sea, of which only the western branch is accessible by road for a significant distance. Again, some DSI work has been done near the sea, but in the lowland zone the river is still subject to minor changes in course during floods. For most of its length, the river valley is steep-sided, with few potential building places. However, a few kilometres upstream of Çamlehens in the Forestry Department is building a rainbow trout hatchery, using water from two small streams which flow into the main river. About 8 km upstream of this unit a very good potential hatchery site was located (see below). Above this again the road becomes difficult, sometimes impassable, and the valley too steep for development.
The substrate is suitable for salmonid spawning in parts of the river, but channelization, straightening and road-building work has reduced the number of pools, and high water turbidity in the lower reaches may be dangerous to eggs and young fish especially in spring. Seatrout certainly go up the river as far as Çamlehensin (which they are said to reach by mid-May), and probably up to Meydan Village, but the precise limit of their migration is not known. There is much illegal fishing during both up and downstream migration by a variety of methods, including both fixed and mobile traps, rods, harpoons and cast nets. In the sea near the river mouth gill and trammel nets are used, but the number of fish taken annually is unknown. It is possible that the smaller but inaccessible eastern branch of the Firtina may now be the most important for seatrout reproduction.
Hemsindere (Pazar) River. There is commercial extraction of gravel from the river bed in the lower reaches. The valley quickly becomes steep-sided, and there is a steep fall between the road and the river, leaving no space for building. The water is frequently muddy up to the town of Hemsin due to landslides and erosion. There is a small private fish farm, producing 6–7 t/year of rainbow trout, on the small western branch of the river. The water used for raceways is often extremely muddy, but the hatchery is supplied with water piped from a small spring. However, there is little room for expansion at this site.
Seatrout have not been seen in this river in recent years. The Hemsindere is not thought favourable for hatchery building due to the poor water quality and lack of building sites.
Büyükdere River. The lower reaches are channelized and contain gravel workings. There is also a copper mine a few kilometres upstream on the western bank. The water turbidity is bad and becoming worse each year, especially during snow-melt. The river was rejected as a potential hatchery site on the grounds of water quality and absence of suitable building places.
Taslidere River. The catchment is extensively developed for tea culture, and there is some pollution of the river from tea-processing factories. The lower reaches are flat, very stony, and subject to changes of course. Above this the valley becomes very steep-sided. Both main arms of the river were examined as far as the roads allowed, but no suitable hatchery sites were identified. The water quality is often poor and muddy. Seatrout have been reported a few kilometres inside the river, but this area is not thought to be important for their reproduction. The river was rejected as a potential hatchery location on the grounds of water turbidity and lack of suitable sites.
Iyidere (or Ikizdere) River. The river has two branches: the main one and an eastern tributary called the Kalkandere. The latter seasonally suffers low flows, and seatrout are not thought to enter it. The main branch is frequently very muddy. There is a power station at the town of Ikizdere, which is supplied with water diverted from higher upstream through tunnels. Consequently, between the power station and the entrance to the tunnel flows are often very low (and the water even more muddy than downstream). The entrance structure to the tunnel also presents an impassable barrier to migrating fish at most seasons, and any fish entering the tunnel will be killed. Seatrout are occasionally seen as far upstream as the power station, but not beyond, and it is believed the river had some importance for spawning before the power scheme was built. Currently there is much erosion and slippage of land in the catchment, contributing to poor water quality, and no good hatchery sites were found.
Baltaci River. Two main branches diverge about 5 km from the sea. The west branch is not accessible by road, and on the east side the road does not follow the river at all points. There is some channelization close to the sea, but above this, the Baltaci is unusual for rivers in this area in having significant areas of flattish, gently-sloping land around it. This land is used for growing nuts, tea, timber and grass, but is potentially suitable for siting fish farms. One potential site is described below. However, the river water is sometimes turbid, making the river less suitable for seatrout hatcheries than those east of the Firtina. Local contacts believe seatrout enter and spawn in the river, but in lower numbers than in the past.
Solakli River. The river has only one major channel, with small side branches feeding into it at intervals. The catchment is very steep, and there is much evidence of serious erosion and land slippage. The water is frequently very muddy almost to the village of Uzungöl, about 30 km from the sea. Above this village the land becomes flatter, and there is a lake which gives the village its name. The lake is fed by small streams originating in springs. The streams are clear, and two small private trout farms are located on them. However, there are no spare sites of any size here, and further downstream the river was rejected as a potential hatchery site on the grounds of poor water quality and shortage of building space.
Seatrout are known to enter the river in small numbers, and may migrate upstream almost to the lake, but the very high silt content of the water must represent a danger to eggs and fry.
The Sürmene, Kara and Yanbolu Rivers (streams) were examined but discounted as potential hatchery sites because of their small size, irregular flow of water, and high water turbidity.
The Değirmendere River, which flows through Trabzon City, was discounted due to industrial pollution and high water turbidity.
West of Trabzon, most streams are small, and their water is dirty. The larger Aksu and Yağlidere were discounted as they have no historical record of seatrout runs, in common with all the rivers to the west of Giresun City.
Occasional seatrout are caught in the mouth of the Görele River (reportedly 6 or 7 fish per year), but the river is small and its water sometimes dirty. It was therefore rejected as a potential hatchery site.
The Harskit River is big, but its water often extremely muddy. The river is already used for electricity production, and further major developments are planned (see Fig. 2). Occasional seatrout are taken up to the power station at Dogankent, about 25 km upstream, but the river was rejected for hatchery purposes on water quality grounds.
Spawning grounds for seatrout
As can be seen from the above paragraphs, it is believed that Black Sea seatrout are still reproducing in significant numbers in the most easterly rivers, i.e., Kapistre, Çağlayan, Findikli, and Firtina (the Çağlayan and Firtina being the most important), and in small numbers possibly in the Taslidere, Iyidere, Baltaci, Solakli and Harskit. The substrate in parts of all these rivers is suitable for salmonid spawning, but in this second group of rivers water turbidity probably becomes high enough to cause mortalities of eggs and early fry. The areas of available substrate suitable for trout reproduction have been greatly reduced in recent years by engineering and agricultural developments.
The above outlines the current position. If the remaining natural spawning beds could be protected, and illegal fishing prevented or at least drastically reduced especially in the region of the four easterly rivers which are most valuable for spawning, the seatrout stock might still be able to recover naturally. However, worse is to come for the fish stock when DSI plans for hydro-electric developments in the region are implemented. Details of current operations, projects under construction, and planned future developments are shown in Figure 3. It can be seen that virtually all significant water-courses are earmarked for power production, including the Firtina, Çağlayan and Kapistre. Hydro dams in Turkey are generally not provided with fish ladders (at least not in the Black Sea region), thus denying access to all spawning grounds upstream. Even where tunnel diversions rather than dams are envisaged, observations of existing projects lead the consultant to the conclusions that these, too, constitute both barriers to upstream migration and lethal traps to downstream-moving fish. Also the building operations themselves, including associated road construction, result in increased water turbidity not only for the period of building but for many years afterwards due to destabilization of the steep hillsides around the rivers. Water flows downstream of tunnel inlets are greatly reduced, sometimes becoming almost dry. It is questionable whether the Turkish Black Sea seatrout stock can survive this additional human pressure.
Historically, A. sturio and Huso huso spawned in the two major rivers located each side of the city of Samsun: the Kizilirmak about 40 km to the west, and Yesilirmak some 30 km east. Lesser runs of unknown species composition were reported in the small Mert River, which enters the sea at Samsun, and in the Sakarya River, situated in the western part of the Turkish Black Sea coast, about 130 km east of Istanbul. In addition the Coruh River, which has its estuary in the USSR but for much of its length flows through Turkish territory, supported spawning of A. stellatus and A. güldenstädti.
The Yesilirmak River (Fig. 3) has changed dramatically in recent years as a result of construction of hydro-electric power schemes. There are currently two dams in operation, both commissioned in 1979. The lowest (Suat Ugurlu dam) is about 40 km from the sea. It is not equipped with a fish pass, and therefore imposes the upstream limit on migration of sturgeons. (In any case, experience in other countries has shown that sturgeons are much less successful at utilizing fish ladders than are salmonids.) Between the dam and the sea, the Yesilirmak has so far not suffered the same degree of engineering development and channelization as the Kizilirmak (see below), and it is understood that flood prevention work will in future be confined to deepening the natural river bed. However, it is suspected that this part of the river receives significant municipal and agricultural pollution. There are also plans to divert much of the water below the Suat Ugurlu dam into canals for irrigation of farm land. This will of course reduce the quantity of water in the main channel.
The Kizilirmak River (Fig. 3) has also been developed for power production, though at a later date than the Yeşilirmak. Only one dam is currently operating, at Altinkaya, about 50 km from the sea. This dam was commissioned only in early 1988. A second, smaller dam is under construction further downstream at Derbent, about 30 km from the river mouth. During the current stage of construction it is understood that discharges from both the dams are routinely stopped completely for periods of several hours each day, leaving parts of the river bed dry below Derbent. Engineering work is being carried out between this dam and the sea for flood prevention purposes. Already the river has been straightened, the sides built up, and the bed deepened, from Derbent to a point about 10 km from the sea, and this work will be continued to the coast. As a result, the river is converted into an artificial canal. As on the Yesilirmak, the next proposed phase of development will divert water from the main channel into smaller, irrigation canals.
Details of water flow rates in the lower reaches off the Kizilimak and Yeşilirmak were extracted from data collected by the DSI for years both before and after dam construction. They are filed at the Fisheries Research Institute in Trabzon. A summary is given in Table 1.
The Sakarya River was not visited by the authors, but it is understood that hydro-power and channelization projects similar to those on the Yeşilirmak and Kizilirmak have also been developed there.
The Mert River now has a very low flow at its mouth, much of its water being diverted at a weir upstream of Samsun city for municipal use. Sand and gravel are also extracted commercially from the river bed. Sturgeons are not thought to use the river nowadays.
Spawning grounds for sturgeons
The spawning grounds available to sturgeons have obviously been drastically reduced recently by the construction of dams on the major rivers. However, since all the dams have been completed only within the last 10 years, and the young of the important sturgeon species require longer than this before they are recruited into the fishery, the reduction of upstream spawning areas cannot in itself be blamed for falling catch rates which have been evident for many years. The changing levels of discharge, changes in water temperature and turbidity, following regulation of these rivers may make them less attractive to sturgeon spawners, and currently the periodic complete stoppage of flow at the Derbent dam on the Kizilirmak clearly renders the spawning migration impossible. The channelization work on the same river will also have reduced the areas of substrate suitable for spawning downstream of the dam. Even the limited areas potentially suitable for spawning which remain will be further reduced by the planned diversion of water into irrigation canals.
Local fishermen believe that few sturgeons now enter Turkish rivers to spawn. When asked how many gravid females they considered could be obtained to supply a hatchery, the concensus was of only 5 or 6 fish from Yeşilirmak, and perhaps up to 20 from the Kizilirmak.
