Elevations of lobster fishery groundlines in relation to their potential to entangle endangered North Atlantic right whales in the Bay of Fundy, Canada

Abstract

Abstract Brillant, S. W., and Trippel, E. A. 2010. Elevations of lobster fishery groundlines in relation to their potential to entangle endangered North Atlantic right whales in the Bay of Fundy, Canada. – ICES Journal of Marine Science, 67: 355–364. Fishing gear is known to be a threat to North Atlantic right whales (Eubalaena glacialis), and groundlines used in the American lobster (Homarus americanus) trap fishery are hypothesized to be an integral component of entanglements that may, in some incidents, lead to mortality. This research measured the elevations above the seabed of 17 regular groundlines on commercially active lobster gear in the Bay of Fundy and evaluated several factors governing rope elevation profiles. Mean elevation was 1.6 m (s.d. = 0.9, n = 5968, range = 0.0–7.0 m). The hypothesis that groundline elevations were ≤1.0 m (predicted height of taut groundlines) was rejected (Fisher's C = 66.9, p < 0.01), as was the hypothesis that elevations were >3.0 m (approximate body height of a right whale; Fisher's C = 129.5, p < 0.01). The proportion of groundline elevations ≤1.0 m was 0.32, and that <3.0 m was 0.92. Groundline elevations were negatively related to tidal current velocity at the time of setting (p < 0.001, r2 = 0.33) and were closer to the seabed in deep than in shallow water (p < 0.05, r2 = 0.07). It is suggested that groundlines in the Bay of Fundy may not constitute a large part of the risk associated with the entanglement of right whales, because most lines remained below the elevation hypothesized to be a threat (3 m). We also identified factors within the control of fishers setting trawls that minimize groundline elevations.