Free-ranging cetaceans present challenges to researchers seeking to better understand their physiology and population dynamics. Given that cetaceans spend most of their time under the sea surface, it may be difficult to obtain tissue samples for analysis. Researchers desiring samples of cetacean tissue have developed a variety of "remote biopsy" techniques since the early 1970s (Winn et al., 1973). Samples obtained from free-ranging cetaceans can offer insights into a suite of biological analyses, including information about genetic relationships, foraging ranges, prey selection, environmental contaminants, stress levels, and reproductive health (Noren & Mocklin, 2012). The information gained can provide a window into the complex social and genetic relationships of marine mammal communities and assist managers with conservation efforts.
Many marine mammal scientists utilize similar remote biopsy sampling devices and techniques. Commonly, a stainless-steel biopsy punch affixed to a dart and fired from a projection device is used to collect a cylindrical plug of skin and blubber from free-ranging marine mammals. The biopsy punch is designed to suit the integument thickness of the target species. Among some dart projectors reported in the literature are recurve crossbows (Lambertsen, 1987; Palsboll et al., 1991; Clapham & Mattila, 1993; Patenaude & White, 1995; Weller et al., 1997; Gauthier & Sears, 1999; Hooker et al., 2001; Gorgone et al., 2008; Kiszka et al., 2010; Kowarski et al., 2014; Reisinger et al., 2014; Sinclair et al., 2015; Fruet et al., 2017), pneumatic (C[O.sub.2]) dart rifles with variable pressure regulation (Bearzi, 2000), a modified powder-actuated 0.22 caliber rifle with variable pressure regulation (Barrett-Lennard et al., 1996; Krutzen et al., 2002; Parsons et al., 2003; Tezanos-Pinto & Baker, 2012; Pagano et al., 2014; Liu et al., 2019), and a modified powder-actuated 0.22 caliber rifle without a pressure adjustment valve (Balmer et al., 2011; Sinclair et al., 2015; see also unpub. marine mammal research cruise reports at https://www.fisheries.noaa.gov/resource/publication-database/cruise-report-database-southeast-fisheries-science-center).
As remote biopsy technology has evolved, researchers should routinely consider the well-being and safety of the target species as they refine methods and research goals. Gales et al. (2009) recommended that remote biopsy device power be evaluated before sampling live animals, and Bearzi (2000) recommended researchers constantly review procedures and equipment out of an abundance of caution. Palsboll et al. (1991) and Patenaude & White (1995) tested the tissue collection efficacy for a range of recurve crossbow power levels with certain biopsy dart designs in development, and Barrett-Lennard et al. (1996) measured the speed and energy of one device/dart combination. However, despite the widespread use of these different tools, there is relatively little detailed information available on the energy transferred to the sample subjects at impact. To assess the energy associated with some remote biopsy device/dart combinations in use and potentially other biopsy systems with similar parameters, the relationship between distance and dart speed/energy for five devices was evaluated using sampling gear and distance ranges reported for small cetaceans--in particular, common bottlenose dolphins (Tursiops truncatus).
Recurve crossbows (hereafter "crossbows") are among the least powerful hunting crossbows and are common among researchers for...