%0 Journal Article %T Trap Happiness and Catch Bias in Sea Lamprey Traps %J Fishes | An Open Access Journal from MDPI %D 2019 %R https://doi.org/10.3390/fishes4020034 %X Sampling fish by trapping can lead to biased conclusions about a population. We used catch data to assess differences between two types of traps for adult sea lamprey ( Petromyzon marinus), submerged-funnel traps and studded-tile traps, which are angled ramps with trickle flow leading out of the water. The studded-tile trap at one river caught about 50% more females than the funnel trap. It caught males that had a smaller body size and females with a lower gonado-somatic index (GSI). The likelihood of catching lamprey in the studded-tile trap increased after they had been caught once. This was not the case for the funnel traps, which are used for mark¨Crecapture-based population assessment of invasive sea lamprey in the Great Lakes. The apparent trap response caused by studded-tile traps may have been caused by a behavioral bias, i.e., the traps consistently attracting a subset of the population. Use of the studded-tile trap for population assessment should only be considered after more is known about its recapture bias. The differences between lamprey caught in the two trap types suggests that a variety of trapping methods needs to be employed in order to get a representative sample from a fish population. View Full-Tex %U https://www.mdpi.com/2410-3888/4/2/34