Design for a Multiple-Method Approach to Determine Stock Structure of BottlenoseDolphins in the Mid-Atlantic. Report of a Workshop. Held in Beaufort, North Carolina on February 11-12, 1997

摘要

Relatively new information has provided the basis for designing a series of fieldstudies that will allow determination of whether the coastal migratory stock of bottlenose dolphins, as currently defined, is actually more than one stock. To date, the methods that have contributed to the understanding include photo-identification, analysis of isotope ratios, morphometric characteristics, feeding habits, genetics, and breeze brands applied during live captures. One critical aspect contributing to success will be the analysis of matched samples (various tissues from an individual analyzed across the various methods) and the subsequent merging of the disassociated results. Existing information is sufficient to suggest an efficient geographic approach for collecting and analyzing samples: beginning at the north and south ends of the distribution of the coastal migratory population, including some of the estuaries in the south that contain year-round residents, then moving toward the center of the distribution. Results are sufficiently preliminary for many of the methods that estimating samples size, a priori, required to detect differences (at alpha=0.05 and beta=0.20) is not feasible. Hence, adaptive sampling will be adopted. Each year sample will be analyzed from each of the geographic sites chosen with each of the appropriate methods, and those results used to determine the optimal way to proceed. Samples and data are available from various sources. Matched samples will be collected from live-captures and specimens killed in fishery interactions. Additional samples will be collected through biopsy sampling. Photo-identification based at five core sites along the coast and satellite transmitters deployed on animals caught during live-captures will provide critical movement data. A central photo-identification catalogue for the entire coast is being developed for use in matching between sites and identification of known individuals for biopsy sampling. The scope of the question will require a multi-year effort; a 3-yr field plan has been developed.