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Mitochondrial haplotype diversity in sympatric populations of Ohrid trout, Salmo letnica was investigated by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the mtDNA control region and ND1, ND3/4, ND5/6 segments. A 310 bp fragment at the 5' end, and a 340-572 bp fragment at the 3' end of the control region were sequenced from representatives of the populations studied. Based on pairwise comparison of the sequences, five new haplotypes were identified plus one identical with the brown trout Andalusian haplotype from the southern Iberian Peninsula. The combination of both RFLP and sequence data sets yielded a total of 10 composite haplotypes. A high degree of genetic subdivision between S. letnica typicus and S. letnica aestivalis populations was observed. The notion of a sympatric origin for the two morphs is discussed. Length variation of the mtDNA control region due to the presence of an 82 bp unit, tandemly repeated one to four times, in the region between the conserved sequence block-3 (CSB-3) and the gene for phenylalanine tRNA is reported. Further, we demonstrate that a single duplication of the approximately 82 bp repeat unit is a common element of the salmonid mitochondrial control region. The unique genetic structure of Ohrid trout represents a highly valuable genetic resource that deserves appropriate management and conservation.

Lake Ohrid is the oldest lake in Europe and one of the oldest lakes in the world, formed 4–10 million years ago. Lake Ohrid serves as a refuge for numerous freshwater organisms from the tertiary period, whose close relatives can be found only as fossils. A breeding programme that artificially hatches the native and endemic trout supports the natural recruitment of lake Ohrid trout and since 1935 the lake has been stocked with more than 600 million young trout. The critical transboundary issue for Lake Ohrid water quality is phosphorus pollution. The current phosphorus load of the lake is estimated at 150 ton per year and needs to be reduced to 50 ton per year to keep the mean concentration of phosphorus below 7 mg m–3 in the lake water. In 1996, a Memorandum of Understanding between the Macedonian and Albanian governments was signed and a binational Lake Ohrid Management Board was established, with substantial funding by the Global Environmental Facility. Both governments agreed to undertake appropriate legal, institutional, investment and technical measures to protect Lake Ohrid. The Lake Ohrid Conservation Project has four main goals: (i) to develop the institutional legal and regulatory framework for environmental management in the Lake Ohrid watershed; (ii) to establish a comprehensive binational monitoring programme, (iii) to mobilize and secure commitments from all the stakeholders in the watershed who will need to take measures to prevent degradation of the lake; and (iv) to increase public awareness and participation. Harmonizing Albanian and Macedonian laws and regulations may be the Lake Ohrid Conservation Project’s greatest challenge, particularly on fisheries and wastewater treatment issues.

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