Horizontal and Vertical Odor Plume Trapping of Red King Crabs Explains the Different Efficiency of Top‐ and Side‐Entrance Pot Designs

Abstract

AbstractInteractions between the food search behavior of the red king crab Paralithodes camtschaticus and pot design and the consequences for entry success were studied in situ with a square pot with two funnels on opposite sides and a conical pot with one vertical funnel at the top. Red king crabs that approached the pots upcurrent were chemically stimulated and appeared to be locked onto the odor plume, whereas those that approached the pots across‐current showed more flexible search behavior. The location of the funnels meant that entry also requireed a vertical search phase. Forty percent of the red king crabs encountering the pots performed vertical searches on each type of pot, but the probability of entry once a vertical search had commenced was 20 times as high for the square pot as for the conical pot. Chemically stimulated red king crabs limited their vertical search to the bait plume. The location of the bait relative to the entrance may have caused chemically stimulated rheotaxis to lead red king crabs all the way into the square pots, in contrast to the conical pots for which the entrance is higher than the extension of the plume. These results demonstrate the importance of including both horizontal and vertical dimensions in behavioral studies of the catch efficiency of crab pots.