Catch of Japanese crab traps in relation to bait quantity and shielding

Abstract

Experiments were conducted at infralittoral sites in the northern Gulf of Saint Lawrence, eastern Canada, to measure the effects of quantity and shielding of bait on numerical yield of Japanese crab traps. The most abundant species in traps were the crabs Hyas araneus and Cancer irroratus, and the gastropod Buccinum undatum. Catch of each of H. araneus and C. irroratus was positively correlated with bait weight, but relative catch increments decreased as bait weight increased because of trap saturation. For a constant bait weight, traps with unshielded bait yielded as many, or more, crabs and gastropods than traps with shielded bait. This was probably due to reduced entry caused by lesser attractiveness of shielded bait and/or greater aggressiveness of hungry animals in traps with shielded bait. Bait quantity is an important, but often neglected and uncontrolled, variable in trap yield.