. "6 Integrating Demographic Information with Abundance Estimates." Assessment of Sea-Turtle Status and Trends: Integrating Demography and Abundance. Washington, DC: The National Academies Press, 2010.
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Assessment of Sea-Turtle Status and Trends: Integrating Demography and Abundance
to determine the likely causes of observed trends. There are a number of modeling approaches of varied complexity and precision that can address management questions, but they all need accurate data at the population level. Vital-rate estimation is essential for these slow-growing species, as trends in nesting-beach abundance provide information about only a tiny fraction of a sea-turtle population. Some data that can be used to determine changes in vital rates already exist, including time series of juvenile abundance (or indexes of abundance) and size distributions.
Assessments of managed fish populations include gathering and reviewing biological information and catch data, a variety of modeling workshops to determine the most appropriate tools for assessment and reference points for status determination, and extensive external peer review. Marine-mammal assessments also follow a prescribed path for evaluation. Sea-turtle assessments have included many of the elements required for those species but are not done in a set procedural framework that ensures consistency, transparency, and thorough evaluation.
There has been no thorough attempt to assess sea-turtle status with population models that are fitted by using available data on bycatch, size distributions, and productivity. That is because of the following three primary factors that can be addressed by the agency:
Critical vital rates have not been monitored so there is high uncertainty in estimates of parameter values and in interpretation of trends.
Data are scattered and require a thorough evaluation to determine their quality and their applicability to population assessment.
Sea-turtle assessment efforts have not been isolated from broader evaluations of status and threats and have rarely included scientists in other quantitative modeling fields, such as fishery scientists.
NMFS and USFWS should develop a general framework for a sea-turtle assessment procedure, including data evaluation, model review, and MSE.
NMFS and USFWS should conduct data-evaluation workshops, starting with Atlantic loggerheads, focused specifically on the evaluation of time series information that can contribute to setting values of parameters for demographic models. Data for evaluation include, but are not limited to, nesting abundance, in-water abundance, hatchling-cohort production, length distributions, and reproductive frequency. All sources of data should be evaluated for quality, consistency and spatial or temporal heterogeneity, and gaps.
Researchers should work with modelers in different fields to