Draft Manuscript: Age, Growth, and Population Dynamics [of Sea Turtles]

Chaloupka, M; Musick, J

Prepared for The Biology of Sea Turtles & CRC Marine Sciences Series. INTRODUCTION: Many sea turtle stocks are in decline worldwide due to excessive harvesting and destruction of nesting and foraging habitats (National Research Council 1990, Bjorndal et al. 1993, Limpus 1993, Horikoshi et al. 1994). Yet population abundance for many stocks can display stochastic fluctuations with no apparent long term trend (National Research Council 1990, Limpus and Nicholls 1994). How are we to know then whether a stock is really at risk and what risk management strategies might be appropriate for protection of the stock. These are challenging questions that cannot be resolved without a thorough understanding of sea turtle growth and population dynamics. Age and size are related components of somatic growth, which itself is a major determinant of population dynamics and macroevolutionary change. Therefore, we review in broad terms a wide range of studies on age, somatic growth and the population dynamics of sea turtle stocks. Firstly, we present an overview of some of the major methodological issues relevant to understanding sea turtle growth and population modelling. This section is essential to appreciate the methodological themes apparent in the remaining sections. Many of the methods used need careful scrutiny of the underlying statistical properties and assumptions. Therefore the main emphasis in this review is on methodological issues. Then we review critically a compilation of sea turtle growth studies arranged in a classification table providing a framework for grouping similar approaches. Next we discuss the complementary approaches of comparative life history analysis and comparative demography as a precursor to population dynamics. In the last section we review critically all known studies on sea turtle population dynamics also arranged in a classification table. We conclude with a brief overview of the review focusing on recurrent methodological issues.