Monster Seminar JAM - Ontogeny of Swimming in Dolphins: Implications for Interactions with the ETP Tuna-purse Seine Fishery
Dr. Shawn Noren, University of California - Santa Cruz
This is the first empirical examination of cetacean calf swim performance. My investigation of the ontogeny of swim performance (average and maximum swim speed) and swim effort (stroke amplitude and tailbeat frequency) of bottlenose dolphins (Tursiops truncatus) demonstrated that swimming capabilities are extremely limited in independently swimming calves. Average and maximum swim speeds of 0-1 month-old calves were only 37% and 52% of that for adults, respectively. Utilization of a specialized swim behavior called echelon (calf positioned near mothers dorsal fin region) granted 0-1 month-old calves a 28% increase in average swim speed and 19% increase in distance per stroke with a concurrent 22% reduction in stroke amplitude compared to independent swimming. Ultimately, adult swim performance was not achieved by independently swimming calves until one year postpartum. Ontogenetic limitations in swim speed were associated with an inability to achieve mature thrusting capabilities, as stroke amplitude and distance covered per stroke remained significantly lower than adult levels during the first year postpartum. Interestingly, dolphins elevate speeds to 1.3-1.9 times adult routine speeds during dolphin chase associated with the tuna-purse seine fishery in the Eastern Tropical Pacific. Because independently swimming calves < 1 year-old are unable to achieve these speeds, maintenance of echelon position is vital for calves to maintain proximity to their mothers during chase. However, the high speeds and erratic movements encountered during dolphin chase may compromise this position such that calves could fall behind. This may explain the lack of recovery of these dolphin populations and the observation that fewer 0-1 year-old spinners and fewer 0-3 year-old spotted dolphins are caught in the tuna purse-seine nets than expected.
University of Washington
The Old Fisheries Center Auditorium (rm 201)
Date and Time:
February 22, 2007,
11:00 am - 12:30 pm