Stara Tisa kod Bisernog Ostrva

Stara Tisa kod Bisernog Ostrva (Old Tisza at Biserno Ostrvo) is a Nature Park in Vojvodina's South Bačka District, protecting a scenic oxbow formed when the Tisza River was straightened during 19th-century regulation works. The park covers approximately 391 hectares of the former river channel, which has evolved into a rich wetland ecosystem of open water, reedbeds, and floodplain forest. ^[1] The abandoned meander is the longest preserved dead arm of the Tisza in Vojvodina, approximately 24.5 kilometres in length, and supports 166 recorded bird species, making it one of the most ornithologically significant wetland sites in the region. ^[1]

The oxbow lake supports 166 recorded bird species, including grey herons, great egrets, and various duck species that breed in the reedbeds and feed on the productive shallow waters. ^[1] White-tailed eagles, saker falcons, and pygmy cormorants — some of the most endangered species in Europe — are recorded as visitors or rare guests, with 87 species under formal protection. The water body harbours fish populations including pike, tench, and carp that attract fish-eating birds, while the amphibian community includes several frog species and European pond turtles in the warm, vegetated shallows.

The vegetation transitions from submerged and floating aquatic plants in the open water through extensive reedbeds to willow and poplar gallery forest on the higher banks of the former river channel. White water lilies, listed among the natural rarities of Serbia, create spectacular floating displays during summer, and the reedbeds provide dense cover for nesting birds. ^[1] The floodplain forest contains mature willow and poplar specimens that provide structural diversity and cavity nesting habitat, while the ground layer supports shade-tolerant wetland herbs and moisture-loving ferns.

The park occupies a meander loop cut off from the main Tisza River during the massive 19th-century regulation programme that shortened the river by approximately one-third through artificial straightening channels. ^[1] The abandoned meander has since functioned as an oxbow lake, gradually evolving through natural succession as sediment accumulates and vegetation encroaches from the margins. The underlying geology consists of river-deposited sands and gravels typical of the Tisza's alluvial plain, with finer silts now accumulating in the quieter waters of the abandoned channel.

The reserve experiences the continental climate of the Vojvodina lowlands with warm summers and cold winters, with the water body providing local microclimate modification through increased humidity and temperature moderation. The oxbow lake's relatively small size means it is significantly influenced by local weather conditions, freezing completely during cold winters and warming rapidly in spring. Summer water temperatures can exceed 25 degrees Celsius in the shallows, creating productive conditions for aquatic vegetation and invertebrates but also risking algal blooms during very warm periods.

The original Tisza River has been a major waterway since prehistoric times, with the section that became this oxbow forming part of the navigable route through the Pannonian Basin. The 19th-century regulation of the Tisza, one of Europe's largest river engineering projects, created numerous oxbow lakes throughout Vojvodina when meandering sections were bypassed by straight channels cut to improve navigation and reduce flooding. ^[1] The abandoned meanders gradually transitioned from active river sections to calm, enclosed water bodies, developing the wetland character that now defines them ecologically.

The site was designated as a Nature Park to protect the ecological values that have developed in this abandoned river channel over the approximately 150 years since it was cut off from the main Tisza. The designation recognises that these artificial oxbow lakes, though created by human intervention, have evolved into functioning wetland ecosystems of genuine conservation importance in a landscape where natural wetlands have been largely eliminated. Management aims to maintain the water quality and ecological integrity of the oxbow while allowing natural succession to proceed at a rate compatible with maintaining habitat diversity.

The park offers quiet boat access to the oxbow lake where visitors can explore the calm waters surrounded by overhanging willows and observe waterbirds at close range without the disturbance of a flowing river. Walking paths along the former river banks provide access to the surrounding gallery forest and views over the lake from elevated positions. The tranquil, enclosed character of the oxbow lake creates an intimate wetland experience quite different from the larger open wetland reserves in the region.

The park is located near the town of Bečej in Vojvodina's South Bačka District, encompassing the territories of three municipalities: Bečej, Novi Bečej, and Žabalj. ^[1] Visitor facilities include basic access paths and a boat launch point for non-motorised watercraft, with the intimate scale of the site making it suitable for quiet nature observation. The site can be combined with visits to other Vojvodina wetland reserves for a comprehensive experience of the region's diverse aquatic landscapes.

The primary conservation challenge is managing the natural process of eutrophication and sedimentation that gradually fills oxbow lakes, eventually converting them from open water through marsh to terrestrial habitat. Maintaining water quality against the pressures of agricultural runoff from surrounding farmland is critical, as nutrient loading accelerates the natural ageing process and can cause damaging algal blooms. The long-term management question is whether to allow natural succession to proceed or to intervene through sediment removal and water management to maintain the current open water habitat indefinitely.