142 
Fishery Bulletin 108(2) 
Yellowfin sole 
Northern rock sole 
Elevating disk diameter 
Flathead sole 
Elevating disk diameter 
□ <1000 g 
■ 1000-1500 g 
£1 >1500 g 
Elevating disk diameter Elevating disk diameter 
Figure 7 
Estimates of and 95% confidence intervals for ratios of fish catches during tests with modified trawl sweeps raised to 
three different heights off of the seafloor to catches with conventional sweeps for broad size classes of four principal flat- 
fish species and a principal gadid species taken in Bering Sea trawl fisheries: yellowfin sole ( Liman da aspera); northern 
rock sole (Lepidopsetta polyxystra)\ flathead sole (Hippoglossoides elassodon)\ arrowtooth flounder ( Atheresthes stomias ); 
and Alaska pollock (Tlieragra chcilcogramma) . 
affected behavioral responses to approaching sweeps, 
including tailbeat frequency and swimming endurance. 
Although any of these behaviors could affect herding- 
related capture rates, the current study did not indicate 
behavioral differences between size classes in response 
to the elevated sweeps. 
We followed commercial practices in the gear type 
used, weight-based catch metrics, towing durations, 
catch handling, and round-the-clock operations. This 
procedure was undertaken to increase the relevance of 
our results to those with the greatest stake in deciding 
on the use of these modifications: the fishermen and 
fishing companies. Fishermen actively participated in 
designing the gear modifications and in conducting the 
research. 
To examine consequences of using modified sweeps 
in the fishery and to improve precision, all tows were 
analyzed together, including day and night tows, even 
