Modeling whale entanglement injuries: an experimental study of tissue compliance, line tension, and draw-length

Two test systems were developed to examine fishing line entanglement injuries in large whales. The systems evaluated straight pull abrasion and oscillatory abrasion in relation to tissue compliance. The straight pull abrasion study was used to measure the depth of epidermal penetration after a unidirectional pull of line over a standard draw-length. The oscillatory pull abrasion system measured the tissue compliance limit under a shear load and used a series of upper/lower pulleys to position an abrading line across the leading edge of the test sample. Tissues from the leading edge of a flipper for a right whale calf and leading edge of an adult right whale were used during this study. Line furrow patterns were documented through photographs and tissue abrasion was compared using the 1) maximum depth of epidermal/dermal penetration and 2) length of epidermal removal. For the straight pull abrasion test, an adult right whale fluke required 3.7 times the load and 15 times the draw-length of a right whale calf flipper for epidermal failure to occur. The oscillatory abrasion test indicated that line draw-lengths were more than the tissue compliance limit and resulted in substantial increased tissue abrasion. Increasing the line's ability to stretch in response to a load could minimize sliding of the line and help mitigate entanglement injuries.