[OANNES Foro] The sampling efficiency of electrofishing swimbladder-lacking benthic fishes

[Mario Cabrejos]

Journal of Applied Ichthyology
Volume 24 Issue 5, Pages 601 - 604
Published Online: 28 Jun 2008

The sampling efficiency of electrofishing for Neogobius species in a riprap habitat: a field experiment
M. Polacik 1,2 polacik en ivb.cz , M. Janác 1,2 , P. Jurajda 1 , M. Vassilev 3 and T. Trichkova 3 
 1 Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Kvetná 8, CZ-603 65 Brno, Czech Republic ;   2 Institute of Botany and Zoology, Masaryk University, Brno, Czech Republic ;   3 Institute of Zoology BAS, Sofia, Bulgaria 

ABSTRACT

Even though electrofishing is commonly used to sample Neogobius spp. and other swimbladder-lacking benthic fishes, its efficiency is considered poor especially in habitats with abundant interstitial spaces. To determine the efficiency of electrofishing Neogobius spp. and quantitatively estimate sampling bias in a riprap (shot rock used to armor shorelines against water erosion) mesohabitat, riprap fragments were set up in a natural riverine environment. 

The experimental setting enabled us to collect all fish remaining in the riprap fragments after these areas had been electrofished. The sampling efficiency of electrofishing Neogobius spp. (dominated by Neogobius melanostomus) varied between 17.6 and 47.4% (mean 29.7%), while percids (possessing a well-developed swim bladder) were collected with 74.6% efficiency. 

Fish size had no effect on the probability of capturing Neogobius spp. by electrofishing. 

Within Neogobius spp., N. melanostomus was less susceptible to electrofishing than Neogobius gymnotrachelus (23.7% and 50.1%, respectively). Decreased electrofishing efficiency in areas of rocky substrate should be considered in estimates of total abundance of Neogobius spp., especially if they are to be compared with catches of other species possessing swim bladders.