It could be argued that humans have collected marine turtle eggs and killed nesting females for food, since the first ancestors of humans reached beaches at which turtles nested. So, in any long-term view, the consumptive use of marine turtles by people may well have existed - been sustained - for tens of thousands, if not hundreds of thousands of years. It is thus not surprising that the consumptive use of sea turtles is culturally and traditionally significant in many, if not most, coastal communities. 

Most concerns about the use of marine turtles today reflect the extent to which vastly increased use, for subsistence or trade, can be sustained indefinitely into the future. Added to the impact of harvesting are other threats (eg alienation of nesting habitat, pollution, incidental catch) which proceed continually, even if harvesting is controlled or prevented. 
 

Superficially it may seem that scientists can or should be able to answer these questions for us. But it is not so simple. The biology of marine turtles is imprecisely known because of the difficulties of studying them in the marine environment. There is considerable information on nesting females, nests, eggs and hatchlings, but these relate only to the brief period where one sex crawls up on the land to nest (perhaps an hour each few years), and the brief time over which eggs incubate in the nest (2 months). To understand the way in which populations operate, we need reasonably precise estimates of mortality rates at different stages between hatching and maturity. These stages occur at sea, when the animals may be widely dispersed. and so precise mortality rates may (and perhaps always will) be largely impossible to obtain. 

The other approach to sustainably using marine turtles is to monitor populations or indices of populations. For example, if the numbers of nesting females are steadily increasing, then there's a reasonable chance that the wild population is steadily increasing. In reverse, if it is steadily decreasing, there's a reasonable chance that the population is decreasing. There are other factors that can shed light on this, such as the age, size or reproductive status (first-nesters or old established nesters), the extent of movement of individuals involved in the harvest, trends in the size of animal caught, etc.

Perhaps the best example of sustainable use based on a wild population is the harvest of Hawksbill Turtles in Cuba. Hawksbills have been harvested in Cuba since the Spanish first arrived there. From the 1960's onward, a harvest of some 5000 per year was undertaken under controlled conditions. It was not an economically lucrative harvest, but it provided food, shell for export and employment for people. In the early 1990's, Cuba concentrated its fishing effort on more valuable resources, and despite sustainability to date, voluntarily reduced the harvest to about 500 per year. The harvest was also restricted to two traditional harvest sites. 

The harvested population is now monitored very closely. The size and an age estimate are made on each individual caught, and to date the results indicate the mean animal caught is getting larger and older. That is, that the population is expanding rather than contracting. A very significant research effort accompanies the program, which involves sophisticated DNA analyses and satellite tracking studies. There is no chance of extinction or even a significant population decline that would not be detected. And as the program proceeds, so a great deal of information on harvesting is gathered that has application to other populations in other parts of the world. 

On the Cayman Islands, a different approach is underway. Here thousands of Green Sea Turtles are produced by captive breeding each year, and these are raised in captivity to provide meat. This program has been operating for over 30 years. 
 

For a variety of reasons, those opposed to "using" marine turtles for any reason have labeled all marine turtles as endangered species. However, when compared to real endangered species ... where a minor management decision could result in extinction ... many sea turtle species could not be considered as endangered. The populations of some species are in the tens of millions, and other, such as Hawksbills, are distributed around the world, are totally protected, and are thriving in many locations despite various levels of use within their range. There was a time when having a species listed as "endangered" was perhaps important to draw public attention to the need to invest resources in its conservation and management. Today, the public expect and are entitled to more honesty. Indeed, many countries and Governments are finding it increasingly difficult to justify the allocation of resources to wildlife species that are neither used nor have value. Programs that provide for the sustainable use of marine turtles can contribute very significantly to conservation.