Mgr. Juraj HajdúUniversity of Prešov in PrešovFaculty of Humaities and Natural Sciences e-mail: hajdu.juraj@gmail.com

V International ichthyological scientific-practical conference

«CURRENT PROBLEMS OF THEORETICAL AND PRACTICAL Ichthyology»

devoted to memory of Ivan Shnarevich

13-16 September 2012, Chernivtsi, Ukraine

Initial experience with threatened limnophilous fish protection in the Danubian

lowland (SW Slovakia)

Study area

The Danube Lowland

Location of the study area

Study area:

SK

HU

former floodplain of Danube, separated from active inundation with dikes

natural aquatic habitats: backwaters - oxbow lakes, remnants of side arms, abandoned meanders;

Study sites:

seminatural habitats: old material pits after excavation of gravel, clay and peat or melioration channels used to control water discharges from the area or for irrigation of fields.

Study sites:

Misgurnus fossilis - NT

Carassius carassius – VUUmbra krameri – EN

Target species:

The main objectives

• ensuring the protection of targeted threatened limnophilous fish species in the study area of the former Danube floodplain in SW Slovakia,

• selection of suitable sites in the area studied demanding habitat restoration by reason of the target species restitution/reintroduction,

• selection of sites in the area studied suitable for the target species restitution/reintroduction,

• re-establishment of artificial reproduction and gaining a sufficient amount of the target species fish fry for its restitution into suitable replacement water habitats,

• maintenance of the target fish species populations in study area (mangement, monitoring).

• The target species are typical representatives of stagnant and slowly flowing waters, such as oxbow lakes, swamps, dead arms.

• Small melioration cannals, with dense aquatic vegetation fulfil the function of suitable replacement habitats.

The target species habitats

population decline = genetic erosion =

raising probability of extinction !

loss of natural habitats

drainage of area/groundwater level decline

+ climate change (dry seasons) =

drying of swamps, oxbow lakes, backwaters

succession

habitat fragmentation and isolation of populations

increase of vulnerability, pressure of predators, competitors and other natural enemies (alien species), water pollution

Main threats of target species

Black bullhead (Ameiurus melas)

Threespine stickleback (Gasterosteus aculeatus)

Pseudorasbora (Pseudorasbora parva)

Prussian carp (Carassius gibelio)

Pumpkinseed (Lepomis gibbosus)

Alochthonous species

Projects/plans/studies

The Conservation Program/Plan of the European

mudminnow (Umbra krameri Walbaum, 1792) –

(Hajdú, J. & Májsky, J., 2004). The study determines

the principles and modes of management measures

for particular sites with the species historical and

recent occurence in Slovakia.

• The Proposal of management measures of selected sites of occurence of the European mudminnow (Umbra krameri) in the Danube lowland with regard to the optimization of habitat conditions (Hajdú, J., 2007). The study provides detailed description of restoration/revitalization measures for individual sites with the occurrence of E. mudminnow in the Danube Lowland.

The main activities - implemented

preparatory research of the study area by reason of selection of suitable sites for implementation of revitalisation/restoration measures, or restitution/reintroduction of target species (determination of the species composition, measuring of basic environmental parameters (O2, pH, cond., sal., turb., water velocity, substratum, macrophytes cover);

revitalisation of selected sites - local excavation of sediment deposits within selected sections of 3 small lateral melioration cannals (blocking of succesion processes);

restoration measures - creation of new seminatural habitats - small artificial lakes serving as replacement habitats for the target fish species (potential neorefugia);

partial monitoring of the sites where the revitalisation measures were executed.

partial deepening/excavation of selected sections of melioration canals filled up with deposits of organic mud (length of excavated section = < 50 m), local removal of bushy vegetation, illegal waste deposits.

Revitalisation measures - PROPOSAL

Revitalisation measures - IMPLEMENTATION

Restoration/renaturation measures

creating of new replacement habitats/microhabitats – excavation of small ponds (50 –100m2), depth about 1 to 1.2 m, at convenient sites,

Monitoring of the target fish species

Up to now only partial monitoring of 10 sites was executed. Based on data from 2011 can be concluded:

• all 3 target species populations showed significant decrease at least at 6 from 10 monitored sites,

• population of European mudminnow disappeared from 6 sites and its abundance decreased markedly at two sites,

• due to dry period during the summer and autumn 2011 - two sites completely dried up and water level at 4 sites decreased significantly,

• high presure of non-native species might have negative effect on the populations of target species,

• the long dry periods seems to have the most significant effect on the populations of target species

Planned activities needed for following period

artificial reproduction of the target species under controlled conditions;

restitution/reintroduction of target species fish fry obtained by artificial reproduction to suitable natural and seminatural habitats;

more complex and simultaneous monitoring of target species populations and habitats is requred;

extension of international communication and information exchange between the experts is requred, as well as cooperation with local representatives of water management and nature conservation is required.

Thank You for Your attention