River channelization effects on fish population structure in the Larraun river (Northern Spain)

Abstract

As a consequence of the construction of the A-15 highway between 1991 and 1995, some modifications affecting the Larraun River (Navarra, North of Spain) were made. One of the most important effects was the channelization of a section of the river in the middle zone. Fish were caught by electrofishing in August of 1996 in the channelized reach, as well as in non-modified stretches upstream and downstream. Physical and chemical variables and shelter availability were also analyzed. The captured fish were measured (total length) and released into the river. We calculated the density, biomass, length distribution and diversity, comparing the obtained results from the different stretches. The number of species was higher in the lower zones of the river and diversity increased progressively downstream. The fish density in the channelized section was slightly lower than in the other two points. Also biomass in the channelized section was about a factor of 10 smaller than the calculated biomass in unaltered points. Moreover, in comparison with the unaltered sections of the river, in the channelized area a major decrease in the presence of fish larger than 150 mm was detected. The low shelter availability in the channelized section, lack of bank vegetation and alterations in the substratum could explain the observed variations in the length distribution, biomass and the lower value of the density of European minnow, Phoxinus phoxinus (Linnaeus, 1758).

The impact of wildfire on stream fishes in an Atlantic-Mediterranean climate: evidence from an 18-year chronosequence

“…It is, however, notable that the apparent ecological impact was significantly related to the degree of management intervention, increasing with the incidence of bank management and associated channelization. Again, the likely mechanistic process, increased erosive power, has been well-documented in geomorphological studies (Barker et al, 2009) and corroborates with evidence from previous ecological studies (Oscoz et al, 2005;Wyzga et al, 2009). By exacerbating ecological disturbance and impeding recovery, the combined stress of habitat modification and wildfire can provoke a synergistic disturbance interaction.…”

Ecological Consequences of River Channel Management

“…Studies have shown that fi sh density and biomass can be negatively impacted by channelization (Hermansen and Krog 1984 ;Oscoz et al . 2005 ), whereas impacts on species richness appear less strong, at least on the reach scale (Steinberger and Wohl 2003 ;Oscoz et al .…”

Spatially Dependent Responses of a Large‐River Fish Assemblage to Bank Stabilization and Side Channels

“…Bank stabilization has been associated with decreases in fish abundances in some rivers (e.g., Knudsen and Dilley 1987;Peters et al 1998;Oscoz et al 2005) but increases in others (e.g., Knudsen and Dilley 1987;Binns 1994;White et al 2010) and has had no effect in still others (e.g., McClure 1991;Madejczyk et al 1998). Similarly, fish species richness has been found to decrease (Oscoz et al 2005), increase (White et al 2010), or remain unchanged (Madejczyk et al 1998) in stabilized reaches. Changes in fish assemblage structure (Madejczyk et al 1998;Eros et al 2008) and size-class distributions (Eros et al 2008) have occurred in bank-stabilized reaches.…”