Pilot acoustic tracking study on young of the year scalloped hammerhead sharks, Sphyrna lewini, within a coastal nursery area in Jalisco, Mexico
A preliminary experience to study, on a small scale, the movements of the young of the year (YOY) Sphyrna lewini (Griffith & Smith, 1834), in the Mexican Central Pacific, using acoustic telemetry within a nursery area. From October to December 2014 seven sharks were tagged with ultrasonic transmitters and tracked for 68 days within a 14 km2 area associated to a river mouth. The quick shark handling allowed their release in less than two minutes and excellent health condition. Although recaptured sharks up to 105 days after tagging did not show symptoms of scar infection, a slight abrasion in the shark skin was observed after 51 days. The ultrasonic transmitter retention was 75%, and the site fidelity was complete (F = 1) during the first ninety days. For the 135-day period, fidelity was 0.63 (0.40-0.80), and the estimated attrition rate was 0.73 (0.34-1). Ninety-seven percent of detections occurred on soft bottoms and less than 30 m depth. The YOY S. lewini stayed active 24 h a day and performed estimated movements of 11.96 km during that time. The home range for all tagged sharks was estimated to be 4.82 km2 using the minimum convex polygon method (MCP) and 4.89 km2 using the kernel utilization distribution method (95% KUD). The KUD estimation showed two core areas within the study area, is the one located in front of the river mouth the most used.