Abundance and night-time habitat use patterns of Ponto-Caspian gobiid species (Pisces, Gobiidae) in the littoral zone of the River Danube, Hungary

We examined the abundance and meso‐habitat use of gobiid species during both day and night along 43 stretches (500‐m long) of the littoral zone at five locations of the Middle Danube, Hungary, in spring and in summer 2004. Electro‐fishing catch per unit effort sampling revealed significantly higher relative densities at night than during the day. Gobiids occupied all the available habitats encountered during sampling. Habitat‐abundance relationships from night‐time samples revealed that the two most abundant species, round goby Neogobius melanostomus and bighead goby Neogobius kessleri, were found in highest relative density along gravel beach and artificial rip‐rap habitats; these species were in relatively low density in sandy areas. Monkey goby Neogobius fluviatilis was more abundant in natural shorelines than in rip‐rap habitats and dispersed more consistently between sandy and gravel beaches. Tubenose goby Proterorhinus marmoratus demonstrated great plasticity in meso‐habitat use. In conclusion, Ponto‐Caspian gobies occurred rather consistently along the Hungarian section of the Danube, occupying all available habitats examined. Abundance‐habitat relations suggest plasticity in meso‐habitat use but partial segregation between species. Further studies are required at multiple spatial scales to assess how micro‐ and meso‐habitat use varies with fluctuating population densities.