Survival from egg to maturity in a declining population of loggerhead sea turtles, Caretta caretta

Previous estimates of survival rates of sea turtle eggs or hatchlings to adulthood depend upon the assumption that their populations are neither increasing nor decreasing in numbers. The assumption is made in spite of the fact that recent interest in sea turtle demography stems from the belief that populations are in decline. This paper presents estimates of the survival rate from egg to maturity necessary to maintain a population of loggerhead turtles, Caretta caretta, at its present observed rate of decline. Conventional demographic equations were used along with values of adult survivorship, fecundity and alternative estimates of age at maturity from the literature. Results indicate that the proportion of eggs surviving to adulthood lies between 0.0009 and 0.0018 in this declining population, as opposed to an estimated value of 0.0025 in the unlikely event that the population is stationary. These results suggest that previous studies have overestimated survival of eggs or hatchlings to maturity in sea turtle populations. The methodology may be used to assess gross survivorship from egg to adulthood in increasing or decreasing populations of any species in which adults and eggs are more easily studied than are juveniles

Concerning Those Things Which We Ought to Have Done: Reflections on the Future of Sea Turtle Research

Since beginning my study of comparative world religion at 12 years of age, I occasionally seek new insights by returning to my native sect, closely akin to the Church of England. A passage in the General Confession has haunted me since childhood: We have left undone those things which we ought to have done (Church of England 1992, emphasis mine). And so I found myself contemplating those things which we ought to have done concerning sea turtle research

Sea turtle conservation and halfway technology

How we define a problem often determines what we are willing to consider as a solution. When we define the impending extinction of a sea turtle species solely in terms of there being too few turtles, we are tempted to think of solutions solely in terms of increasing the numbers of turtles. Hence, some of our attempts to conserve sea turtles involve halfway technology, which does not address the causes of or provide amelioration for the actual threats turtles face. Programs such as headstarting, captive breeding and hatcheries may serve only to release more turtles into a degraded environment in which their parents have already demonstrated that they cannot flourish. Furthermore, captive programs may keep turtles from serving important ecological functions in the natural environment, or place them at some disadvantage relative to their natural counterparts once released. Such programs can be contrasted with more appropriate technologies that directly address and correct particular problems encountered by sea turtles without removing them from their natural habitat. For example, installing turtle excluder devices in shrimp trawl nets will reduce mortality of adults and larger juvenile sea turtles, and using low pressure sodium lighting on beaches may prevent hatchlings and nesting females from becoming disoriented. In the final analysis, we need clean and productive marine and coastal environments. Without a commitment to such long term goals, efforts to protect sea turtles will be futile

Sea turtle headstarting and hatchery programs

Recent declines in sea turtle populations are largely date to coastal development, which destroys nest sites, and adult mortality in fishing and shrimping nets. Recovery of sea turtles requires protection of juveniles through captive-release programs as well as preservation of beach habitat by limiting development. It also requires protecting adults at sea by decreasing mortality from fishing and shrimping

Kemp\u27s decline: special alarm or general concern?

Woody (1986) called attention to the fact that the number of female Kemp\u27s ridleys, Lepidochelys kempi, nesting at Rancho Nuevo has continued to decline in recent years. Aside from stating that the US Fish & Wildlife Service estimated a decline of approximately 30% between 1978 and 1985, no indication was given of the rate of decline or of the time remaining until extinction of the nesting population. The present work is intended to provide such estimates and to compare the rate of decline of Kemp\u27s ridley with that of a threatened population of loggerhead sea turtles, Caretta caretta