Dungeness Crab Trap Catch Efficiency Related to Escape Ring Location and Size

Abstract

The Dungeness crab Metacarcinus magister (Cancer magister) supports a commercially important fishery along the West Coast of the United States. Only male crabs above a certain size limit may be retained (i.e., legal-size males). Escape rings are used in traps to create circular holes that facilitate the release of both females and undersized males (sublegal crabs). Sublegal crabs that are retained in a trap can suffer stress, injury, and mortality. In this experiment, both the location and size of the escape ring were modified in an effort to reduce retention rates of sublegal crabs. Four different trap configurations were used: (1) a standard trap without escape rings (control configuration); (2) an unmodified trap with two 4.25-in-diameter escape rings on top (standard configuration); (3) a standard trap with one 4.25-in-diameter escape ring placed in each corner adjacent with the bottom (modified 4.25-in configuration); and (4) a trap with two 4.5-in-diameter escape rings on top and one 4.5-in-diameter escape ring placed in each corner adjacent with the bottom (modified 4.5-in configuration). Two different catch statistics were compared among trap configurations: catch of legal-size males and catch of sublegal crabs. No statistical difference was observed in the catch of legal-sized males in any trap configuration. Compared with the standard configuration, the two modified configurations caught significantly fewer sublegal crabs. Catches of sublegal crabs were not statistically different between the modified 4.25-in and modified 4.5-in configurations.

Received December 6, 2016; accepted June 13, 2017 Published online August 22, 2017

ACKNOWLEDGMENTS

We are grateful to Noelle Yochum for providing valuable editorial feedback. This work was made possible by the Puyallup Tribe of Indians and the Northwest Indian Fisheries Commission.