Influence of the Twilight Period and Different Sampling Methods on Catch of Gobiids (Gobiidae) at Four Locations in the Inshore Parts of the Danube River

Abstract

The aim of this work was to compare the efficiency of two different methods for fish sampling and to assess the influence of the twilight period on the catch of gobiids along the Danube River in Serbia. The samplings were performed by electrofishing and beach seining in inshore parts of the Danube River with water depth up to 120 cm at four locations: Novi Sad, Belgrade, Tekija, and Prahovo, in October 2012 and September 2013. At each location, the samplings were performed at 17:30, 18:30, 19:30 and 20:30. Totally, 539 gobiids were caught. The highest number of specimens (218) was registered at Tekija, while lower numbers were registered at Belgrade (192) and Prahovo (117), and only 12 specimens were caught at Novi Sad. The catch of the round goby Neogobius melanostomus and monkey goby Neogobius Aviatilis was more efficient by beach seining than by electrofishing, whereas the catch of the tubenose goby Proterorhinus semilunaris was more efficient by electrofishing. Both methods had similar efficiency in catching the bighead goby Ponticola kessleri and racer goby Babka gymnotrachelus. The species diversity and number of the caught specimens were the highest at 18:30. All five species were recorded at Belgrade, Tekija and Prahovo, while only the monkey goby and racer goby were caught at Novi Sad. The methods used in this study showed good efficiency in catching gobiids, especially at dusk. Even though these methods are difficult to apply in certain habitats, they could be highly relevant in the regular monitoring of gobiids along the inshore parts of rivers.