Abstract
Conservation planning for protected species often relies on estimates of life‐history parameters. A commonly used parameter is the instantaneous maximum population growth rate (r max) that can be used to limit removals and design recovery targets. Estimation of r max can be challenging because of limited availability of species‐ and population‐specific data and life‐history information. We applied a method proposed by Neil and Lebreton, originally developed for birds, to loggerhead turtles. The method uses age‐at‐first‐reproduction and adult survival to estimate r max. We used a variety of datasets and matrix population models to confirm an allometric assumption required by the method, and to generate estimates of age‐at‐first‐reproduction and adult survival. A meta‐analysis was applied to parameters from reported growth curves, which were then combined with the size distribution of neophyte nesters to derive estimates of age‐at‐first‐reproduction. Adult survival rates were obtained from an existing matrix population model. Monte Carlo simulation was then used to combine the estimates of the allometric coefficients, age‐at‐first‐reproduction, and adult survival to obtain a probability distribution of approximate r max values. Estimated annual maximum population growth rates averaged 0.024, with a mode of 0.017 and a 95% highest density interval of 0.006–0.047. These estimates were similar to values reported by others using different methods and captured the variability in positive, annual change estimates across nesting beach sites for the northwest Atlantic loggerhead population. The use of life‐history parameters has a long history in wildlife and fisheries management and conservation planning. Our estimates of r max, while having some biases and uncertainty, encompassed values presently used in recovery planning for loggerhead turtles and offer additional information for the management of endangered and threatened species.
Highlights
IntroductionThe maximum rate of population growth, be it instantaneous (rmax) or finite ( max), is an important demographic parameter for the con‐ servation and management of marine wildlife (e.g., marine mammals, sea turtles, sharks, and seabirds)
The maximum rate of population growth, be it instantaneous or finite, is an important demographic parameter for the con‐ servation and management of marine wildlife
We develop a plausible distribution of maximum population growth rates for the northwest Atlantic (NWA) popu‐ lation of loggerhead turtles using the method outlined in Niel and Lebreton (2005)
Summary
The maximum rate of population growth, be it instantaneous (rmax) or finite ( max), is an important demographic parameter for the con‐ servation and management of marine wildlife (e.g., marine mammals, sea turtles, sharks, and seabirds). The maximum rate of population growth can be used to define management objectives that include setting recov‐ ery criteria or limiting removals from threatened populations (Curtis & Moore, 2013; NMFS and USFWS, 2008; Wade, 1998). A general approach for setting conditions on removals from threatened pop‐ ulations uses limit reference points (LRPs; Curtis, Moore, & Benson, 2015), such that removal estimates that exceed an LRP trigger subse‐ quent management action. Examples of LRPs for protected species include the Potential Biological Removal (PBR, Wade, 1998) and the Reproductive Value Loss Limit (RVLL, Curtis & Moore, 2013); both are functions of the maximum population growth rate. Other as‐ sessment approaches, often used for loggerhead sea turtles (Caretta caretta; see Figure 1), that could benefit from estimates of maximum population growth include qualitative evaluations of jeopardy Other as‐ sessment approaches, often used for loggerhead sea turtles (Caretta caretta; see Figure 1), that could benefit from estimates of maximum population growth include qualitative evaluations of jeopardy (U.S Dept. of Commerce 2001) and population viability analyses (Merrick & Haas, 2008; Snover & Heppell, 2009)
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