There are no scientific data available which would allow reliable estimates of population size to be made for Turkish Black Sea seatrout or any of the sturgeon species occurring in the region. No historical records of seatrout catches were kept, but the State Institute of Statistics in Ankara did publish catch data for sturgeons annually for the years 1968–79 (Fig. 1). The data, collected mainly from the Istanbul fish market, are considered incomplete, and the species composition of the catch is unknown. Nevertheless, from the published data it appears that annual landings fell rapidly from over 300 t during the late 1960s to around 30 t in 1970. There then followed a brief period of recovery, possibly as a result of recruitment into the fishery of juveniles released from Soviet hatcheries, and the 1974 catch again exceeded 300 t. However, subsequently the fishery rapidly collapsed, with annual landings of 10 t or less being recorded after 1975.
With the exception of beluga (Huso huso) more than 140 cm long, the fishery for sturgeons has been prohibited since 1979, and landings of seatrout are also legally banned. However, enforcement of the law is at best poor when not altogether absent. Consequently, fish are still being taken both deliberately and as an accidental by-catch during fishing operations aimed at other species.
The major fishing pressure on sturgeons is currently exerted by trawlers, which operate legally at a distance greater than 3 mi from the shore along the Turkish coast west of Giresun. The same boats are also said to fish freely illegally within the 3-mi limit. Trawlers land sturgeons at all the major fishing ports on this part of the coast, but especially at Samsun, where the authors witnessed sales of these fishes daily during their visit in April. The species seen were beluga (Huso huso, common local name morina), Atlantic sturgeon (Acipenser sturio, local name mersin), Russian sturgeon (Acipenser güldenstädti, locally Rus mersin), and sevruga (Acipenser stellatus, or sevriska). In addition, it was reported that a fifth species, Acipenser nudiventris (local name sip), is also landed at Samsun.
The consultants also saw two of these species, A. sturio and A. stellatus, offered for sale at Trabzon fish market. Additional fishing pressure is exerted by small-scale gillnetting activities along the shore in the approaches to rivers, and in the mouths of the major rivers themselves, by the setting of fixed line of hooks. These lines, sometimes consisting of thousands of large unbaited hooks, are designed to foul-hook fish when they enter the rivers during their spawning migration. The use of such equipment was formerly common, but is now rare due to the present scarcity of sturgeons in the rivers (see below).
Seatrout are taken illegally both in the sea and in rivers along the Turkish coast approximately from the town of Giresun eastwards to the Soviet border. In this area trawling is illegal, but trout are occasionally caught accidentally in purse-seines. The major method of capture for this species in the sea is now probably small-scale gillnetting. Nets set at right angles to the shore to catch mullets, flatfish, etc., also take seatrout; and fishermen deliberately set their nets in the approaches to rivermouths during the trout's spawning migration. Other part-time fishermen use trammel nets at night to capture individual seatrout. Using a small boat equipped with a light, the fisherman locates a fish visually in shallow water. He then surrounds the quarry with a trammel net, and finally frightens the fish into the net by splashing the water and banging on the boat. In past years harpoons were used instead of nets to capture fish located in the same way.
When the adult seatrout enter the rivers, they are subject to fishing by sport anglers using lures, baits, etc. In addition, part-time fishermen take seatrout using cast nets, harpoons, and explosives. These methods are often used on the spawning beds themselves, where fish betray their presence by the cloud of turbidity resulting from excavation of the redds. During their downstream migration after spawning, spent fish are subject to further danger from specially constructed traps. Some of these traps are quite elaborate fixed structures. Stone walls act as “wings” to lead the fish into the trap itself, which is an artificial weir supporting a wooden grid. The grid allows water to pass, but retains fish, which are removed by hand.
Evidence of fish numbers collected during interviews with illegal fishermen is inevitably anecdotal, and might be expected to underestimate the true level of catches. Nevertheless, it is believed that the large number of illegal fishermen still active is in itself evidence that substantial numbers of fish are being taken, at least in the case of seatrout. One fishermen's cooperative in the eastern Black Sea area (Rize) alone estimated that its 80 members sold a total of almost 1 000 seatrout (averaging 3–5 kg), through the organization during 1988. However, the majority of these fish were said to be taken from the sea in the extreme east of Turkey (Hopa area). It is possible, therefore, that many of them are fish returning to rivers on the Soviet side of the border, and therefore not belonging to the Turkish stocks. It is known that a re-stocking programme for this species is functioning in the nearby Soviet Republic of Georgia (see below). However, all sources (government, professional and sport fishermen) were in agreement that seatrout catches have declined dramatically during recent decades. Seatrout are now rarely seen in local Black Sea fish markets. As soon as they are landed, fish are sent by bus to Istanbul, Ankara or other big cities, where they are reported to find a ready market in luxury hotels and restaurants.
In the case of sturgeons, some illegal fishermen stated that they no longer set hooks or nets in the major rivers, because the fish are so rare. Similarly, the biggest caviar dealer in Samsun, who claims to handle around 90% of the total Turkish Black Sea production, reported a decline in his family business from over 8 t/year of caviar during 1940–1970 down to little more than 200 kg in 1988. By weight, the major species now landed by tralwers is probably Huso huso, of which the caviar dealer cited above estimated that about 100 specimens pass through Samsun per year. Despite the large size of some individuals (the consultants saw several fish between 250 and 400 kg), this species very rarely contains caviar when caught in Turkish waters. Instead, large female fish are almost always spent. It is believed, therefore, that Huso huso does not now spawn in Turkish rivers.
Individuals captured by Turkish vessels are therefore thought to belong to stocks which reproduce in the larger, Soviet rivers, or result from releases of hatchery-reared juveniles in the USSR. The same may be true of Acipenser güldenstädti, which local fishermen believe never enter Turkish rivers. Acipenser sturio is perhaps the predominant “native” species in Turkey at present and is the most numerous in the catch. A. stellatus and A. nudiventris probably also enter Turkish rivers, but in very small numbers. All these native stocks are feared to be close to extinction.
No significant scientific studies have been made on seatrout or sturgeon in Turkish coastal areas or rivers. Consequently, precise basic biological information is lacking, i.e., age and size at first maturation and at the time of migration to the sea, degree of spawning success and survival rates of juveniles in the various rivers, the timing of seaward and spawning migrations, location of feeding grounds in the sea, percentage returns of adult fish, etc. Most of these parameters can only be estimated from overseas experience pending collection of local data (see suggestions below). However, the fishermen report that adult seatrout can be caught in the coastal approaches to rivers from late February until May, and in the rivers themselves until October-November. Spawning takes place in autumn, predominantly September and October. Similarly the season for sturgeon catches close to or in the river mouths is early February to the end of May, but fish are also landed from the sea at other times.
As an aid to hatchery planning, the mission initiated collection of data on age of seatrout at smoltification and maturation. Juveniles were caught in the rivers by electric fishing in early May. At that time all fish obtained were part between 8.5 and 13 cm long approaching one-year-old. No smolts were captured, perhaps because fishing was done too early in the season and perhaps because electric fishing was rendered impossible in most places by torrential flows caused by melting snow.
Routine collection of catch data and scale samples from Rize fishermen's cooperative and from private fishermen was also started. All adult fish from which scales were examined were either 3 or 4 years old (fish between 2.5 and about 4 kg body weight normally 3 years and fish 4.5–6 kg 4 years). These limited data will be supplemented by continuing observations (see below) but suffice to suggest that smoltification normally occurs at age 1+, and first maturation at 3 and perhaps sometimes 4 years old.
