41 



communication with other fisheries Biologists, this method might produce reliable sculpin 

 population estimates if the number of passes are increased. As already noted, sculpins 

 were capable of eluding the electrical field. Those individuals that escaped were often 

 hunted for while passing back through the same section of a stream. The escapee was 

 often caught with greater ease on the second pass. At sites where a large number of 

 sculpins were necessary for electrophoresis analysis, the electroshocker was worked back 

 and forth through a particular section of stream making three and four passes over the same 

 spot. Sculpins continued to be netted at points along the segment even on the fourth pass. 

 These individuals caught on the fourth pass seemed easier to net suggesting that repeated 

 passes of die electrical field have a cumulative effect on sculpins. Doug Perkinson 

 observed an increase in sculpin numbers with each pass of the elctroshocker while doing 

 population estimates on salmonids in the Kootenai National Forest. This evidence suggests 

 that methods applied for salmonid population estimates will yield reliable sculpin 

 population estimates provided a sufficient number of passes are taken. 



In addition to the higher yield of sculpins per sampling effort, the electroshocker was 

 also a more versatile tool for sampling a variety of habitats which sculpins occupy. 

 Diagonal transects with D-nets and kick-screen techniques are limited to habitats with 

 adequate current velocity, thus, limiting sampling sites. It is evident from this study that 

 sculpins occupy a variety of habitats with varying current velocities. The electroshocker 

 enables one to sample all likely sculpin habitat on streams up to fourth order. The 

 backpack model was limited on larger streams due to the dissipation of the electrical field, 

 ability of the sculpins to escape, as well as water depth for samplers. 



Diagonal transects using D-nets were an effective sampling method in riffles containing 

 small rubble and relatively high sculpin densities. However, this method was limited to 

 areas of higher current velocity which biased sampling results. Young of the year sculpins 



