360
The Biology of Sea Turtles, Vol. II
experience the value of sea turtle genes. As yet, no genetic material from sea turtles
has been marketed or has been used with recombinant technology to produce an
economic product. In recent years, however, genetic material from sea turtles has
become an integral part of scientific studies as a nonconsumptive use of sea turtles
(Bowen and Karl, 1997). Much of this noneconomic value comes from genetic tools
that allow a greater understanding of sea turtle populations and their relatedness
(Bowen, 1999) as well as sea turtle mating (FitzSimmons, 1998; Francisco-Pearce,
2001) and migratory behavior (Meylan et al., 1990). Arguably, these genetic tools
also assist in acquiring information valuable from a wider perspective, as information
applied toward understanding the genetic consequences of a wide distribution for a
long-lived animal and applied toward conserving highly migratory international
species (Bowen, 1997). In all animals, this value at the genetic level is reduced by
the loss of diversity and rare genotypes.
Sea turtles are most commonly thought of as having value as individuals, and
most of the consumptive use of sea turtles drives value at this level. An individual
green turtle captured from the water would typically be marketed by weight, or would
be butchered and sold by the component weight of its meat. Some parts of a green
turtle’s anatomy are more valuable than others. For instance, the fatty and gelatinous
tissue lining the interiors of the plastron and carapace (calipee and calipash) is boiled
for green turtle soup stock and has historically brought a greater price by weight than
green turtle meat (Carr, 1967; Parsons, 1962). Anatomical variation in value may be
greatest in the hawksbill, a sea turtle having the majority of its consumptive-use value
in the scutes covering its shell (Meylan and Donnelly, 1999).
Life stage plays a role in the valuing of individual sea turtles. For most species,
the greatest rate of consumptive use of individual sea turtles comes from their harvest
as eggs. It is argued that eggs have a high economic value relative to their reproductive value (reproductive value is the chance of an egg resulting in a turtle that
produces more eggs; Crouse et al., 1987), and eggs are believed by some to have a
higher potential for sustainable harvest than other sea turtle life stages (Mrosovsky,
1983). Consumptive use value of individual sea turtles that are eaten or are sold as
food increases with the weight (and thus, age) of the turtle, but this increase seems
unlikely to keep up with the high reproductive value of maturing turtles. For example,
Frazer (1983) estimated that the reproductive value of an adult female loggerhead
(average straight carapace length = 92 cm, approximately 110 kg) is approximately
twice that of an 85-cm immature female (approximately 85 kg) and 8–10 times that
of a 65-cm immature female (approximately 50 kg).
Much of the consumptive use of individual sea turtles is for subsistence, defining
the ecological value of sea turtles as human prey. Unfortunately, many of the
examples of predator–prey relationships between sea turtles and people are shortlived. There is a clear modern tendency for human beings to overexploit sea turtles
(Parsons, 1962; Thorbjarnarson et al., 2000) — a tendency that underscores the
recent nature of our predatory relationship with sea turtles.
Individual sea turtles also have a nonconsumptive use value that is generally recognized. Watching sea turtles and learning from them involves encounters with individual animals at sea or on nesting beaches. A relatively high existence value for
individual sea turtles is reflected in human behavior, to the extent that people not only
1123 book.book Page 360 Monday, November 11, 2002 11:11 AM
The Biology of Sea Turtles, Vol. II
experience the value of sea turtle genes. As yet, no genetic material from sea turtles
has been marketed or has been used with recombinant technology to produce an
economic product. In recent years, however, genetic material from sea turtles has
become an integral part of scientific studies as a nonconsumptive use of sea turtles
(Bowen and Karl, 1997). Much of this noneconomic value comes from genetic tools
that allow a greater understanding of sea turtle populations and their relatedness
(Bowen, 1999) as well as sea turtle mating (FitzSimmons, 1998; Francisco-Pearce,
2001) and migratory behavior (Meylan et al., 1990). Arguably, these genetic tools
also assist in acquiring information valuable from a wider perspective, as information
applied toward understanding the genetic consequences of a wide distribution for a
long-lived animal and applied toward conserving highly migratory international
species (Bowen, 1997). In all animals, this value at the genetic level is reduced by
the loss of diversity and rare genotypes.
Sea turtles are most commonly thought of as having value as individuals, and
most of the consumptive use of sea turtles drives value at this level. An individual
green turtle captured from the water would typically be marketed by weight, or would
be butchered and sold by the component weight of its meat. Some parts of a green
turtle’s anatomy are more valuable than others. For instance, the fatty and gelatinous
tissue lining the interiors of the plastron and carapace (calipee and calipash) is boiled
for green turtle soup stock and has historically brought a greater price by weight than
green turtle meat (Carr, 1967; Parsons, 1962). Anatomical variation in value may be
greatest in the hawksbill, a sea turtle having the majority of its consumptive-use value
in the scutes covering its shell (Meylan and Donnelly, 1999).
Life stage plays a role in the valuing of individual sea turtles. For most species,
the greatest rate of consumptive use of individual sea turtles comes from their harvest
as eggs. It is argued that eggs have a high economic value relative to their reproductive value (reproductive value is the chance of an egg resulting in a turtle that
produces more eggs; Crouse et al., 1987), and eggs are believed by some to have a
higher potential for sustainable harvest than other sea turtle life stages (Mrosovsky,
1983). Consumptive use value of individual sea turtles that are eaten or are sold as
food increases with the weight (and thus, age) of the turtle, but this increase seems
unlikely to keep up with the high reproductive value of maturing turtles. For example,
Frazer (1983) estimated that the reproductive value of an adult female loggerhead
(average straight carapace length = 92 cm, approximately 110 kg) is approximately
twice that of an 85-cm immature female (approximately 85 kg) and 8–10 times that
of a 65-cm immature female (approximately 50 kg).
Much of the consumptive use of individual sea turtles is for subsistence, defining
the ecological value of sea turtles as human prey. Unfortunately, many of the
examples of predator–prey relationships between sea turtles and people are shortlived. There is a clear modern tendency for human beings to overexploit sea turtles
(Parsons, 1962; Thorbjarnarson et al., 2000) — a tendency that underscores the
recent nature of our predatory relationship with sea turtles.
Individual sea turtles also have a nonconsumptive use value that is generally recognized. Watching sea turtles and learning from them involves encounters with individual animals at sea or on nesting beaches. A relatively high existence value for
individual sea turtles is reflected in human behavior, to the extent that people not only
1123 book.book Page 360 Monday, November 11, 2002 11:11 AM