732, males r2= 0.678) than fin height. Gompertz age/length growth curves were fitted to these individuals. Linear regressions were used to estimate total length for 34 individuals from laser-metrically estimated fin base length. Individuals were then assigned
one of three age categories. This system shows promise as a noninvasive way of measuring individuals, while allowing simultaneous photographic identification. The ability to age and measure individuals within a population is useful for a variety of reasons. Length estimation is important for examining growth (Clark et al. 2000), determining size class (Cubbage and Calambokidis 1987), subspecific status (Baker et al. 2002), different geographic forms (Perryman and Lynn 1993, Perryman and Westlake 1998, Jaquet 2006) and the extent of sexual size dimorphism (Ramos et al. 2002, Martin and Da Silva 2006). Age estimates are required for age-structured population models (Slooten and selleck Lad 1991, Cameron et al. 1999).
Age and size also determine maturity and influence reproductive success (Martin and Rothery 1993). It is difficult to calculate exact ages for marine mammals; however, a number of techniques are commonly used to provide an estimate of age. The standard procedure for estimating age in odontocetes and pinnipeds involves counting the incremental growth layers in tooth sections (Perrin and Myrick 1980, Myrick et al. 1984). This technique has been used on live animals but is highly invasive as it involves capture of the check details animal and extraction of a tooth (Arnbom et al. 1992, Childerhouse et al. 2004, Bell et al. 2005). Long-term photo-ID studies can also provide age data (Hamilton et al. 1998), but this requires intensive fieldwork over the study species’ lifetime and typically obtains a minimum age, unless the individual is marked as a calf (e.g., Kraus et al. 1986). Photogrammetry
is a well-established, noninvasive method for measuring individuals, both in terrestrial and marine environments (e.g., elephants, Loxondonta africana, Schrader et al. 2006; gorillas, Gorilla MCE公司 gorilla, Breuer et al. 2006; and northern bluefin tuna, Thunnus thynnus thynnus, Costa et al. 2006). Photogrammetric techniques are particularly useful as noninvasive field methods for marine mammals, as they do not require capture. There are two general approaches to photogrammetry, either stereo-photography or single camera photography. Stereo-photogrammetry uses a pair of overlapping images to create a 3-D optical model, in which scale is provided by the known distance between the cameras and the lens magnification (e.g., Ratnaswamy and Winn 1993, Dawson et al. 1995, Bräger and Chong 1999, Waite et al. 2007). Single camera photogrammetry requires either a known object in the image for scale (e.g., Best and Rüther 1992, Flamm et al. 2000) or a measurement of the range to the individual (e.g., Gordon 1991, Spitz et al. 2000, Jaquet 2006).