Effects of Human Traffic on the Movement Patterns of Hawaiian Spinner Dolphins (<I>Stenella longirostris</I>) in Kealakekua Bay, Hawaii

Abstract

Kealakekua Bay is an important resting site for Hawaiian spinner dolphins (Stenella longirostris) and is popular with both local residents and tourists. Human activities occurring here include swimming, snorkeling, kayaking, and motor-boating. The objectives of this study were to document movement patterns of dolphin groups in Kealakekua Bay, to determine if different types and levels of human activity within the bay result in quantifiable changes in dolphin group movement patterns, and to provide baseline data for future studies. Theodolite tracking was used to assess responses of dolphin groups to human traffic. Variables examined included group mean leg speed (leg speed: the distance between two consecutive theodolite fixes of a dolphin group divided by time; mean leg speed: the average of all leg speeds comprising a track) and group reorientation rate. Swimmers and/or vessels were present within 100 m of all dolphin groups tracked during all surveys. Regression analyses were used to examine potential relationships between dolphin group related variables (e.g., reorientation rate, mean leg speed) and variables related to human activities (e.g., swimming, kayaking, motor-boating). Increasing levels of human activity had a limited but measurable effect on the movement patterns of Hawaiian spinner dolphin groups at this site.