Abstract
Accurate measurements are critical data for wildlife managers. Measuring animals such as marine megafauna in the wild can be uniquely challenging, especially for species that cannot be directly physically measured without the use of invasive capture techniques. This includes manta rays (Mobula spp.). The Florida Manta Project aims to collect a robust dataset that includes size information. This internship project aimed to assess and compare different measurement methods for mantas: 1) underwater laser photogrammetry, 2) aerial photogrammetry, and 3) visual estimation by trained researchers. This study analyzed size data collected from comparative data on 26 mantas measured by laser, drone, and visual approximation during small boat surveys. The primary objective of this project was to assess the precision and consistency between methods, identify any significant trends, biases, or limitations, and strengthen the current methodology. Ensuring the precision of size measurements enhances understanding of life history traits, such as size at maturity, and supports more effective population models and conservation strategies. The results show the reliability of laser and aerial photogrammetry, with the laser method being slightly more precise but the two providing largely interchangeable results. Though visual estimations offer a technology-free way to estimate the size of an individual, they tend to overestimate size and are susceptible to bias. Additionally, all three current protocols proved to be consistently replicable between trained researchers.