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OCR for page 118
7
Conservation Measures
he endangered or threatened status of sea turtle species in U.S.
waters dictates aggressive and comprehensive management plans to
expedite population recoveries. The immediate goal of any manage-
ment scheme must be to arrest population declines. The ultimate
goal is to establish conditions that permit breeding populations to
increase numbers to some level at which a species is no longer at appre-
ciable risk of extinction. Most strategies for achieving those goals are in
broad, nonexclusive categories: strategies to increase the supply of ani-
mals and strategies to reduce causes of death so that animals in the sys-
tem have a better chance of entering and remaining in the breeding pop-
ulation.
Natural mortality factors, except those affecting eggs and hatchlings on
beaches, typically are difficult, if not impossible, to manipulate; mortality
factors that result from human activities are more amenable to manage
ment. Strategies to increase reproduction and reduce mortality will be
discussed in this section after we describe the general rationale and objec-
tives of recovery plans.
118
OCR for page 119
119
Decline of the Sea Turtles
RATIONALE AND OBJECTIVE OF THE RECOVERY PLAN
The Endangered Species Act of 1973 (Public Law 93-205) provides for
the conservation, protection, and propagation of species of wild fauna
and flora actually or potentially in danger of becoming extinct. All sea
turtles in U.S. waters have been listed as either endangered or threatened.
An endangered species is "any species, subspecies, or distinct popula-
tion of fish, or wildlife, or plant which is in danger of extinction through-
out all or a significant portion of its range." A threatened species is "any
species, subspecies, or distinct population of fish or wildlife, or plant
which is likely to become an endangered species within the foreseeable
future throughout all or a significant portion of its range."
The status of discrete breeding populations of listed species must be
reviewed every 5 years, and recommendations, if warranted by the
biological data, for Relisting or reclassification must be made to the secre-
taries of the Departments of the Interior and Commerce, who jointly
administer jurisdictional responsibilities for sea turtles.
The leatherback and hawksbill were listed as endangered throughout
their ranges on.June 2, 1970. The Kemp's ridley was listed as endangered
on December 2, 1970. The green turtle was listed on July 28, 1978, as
threatened, except for the breeding populations of Florida and the Pacific
coast of Mexico, which were listed as endangered. The loggerhead was
listed on July 28, 1978, as threatened wherever it occurs. Those sea tur-
tles were listed because, to various degrees, their populations had
declined as a result of human activities.
Many of their nesting beaches
had been affected by encroachment of the human population into coastal
habitats. Sea turtle populations had been reduced by uncontrolled har-
vesting for commercial purposes and by deaths incidental to such activi-
ties as commercial fishing. In many cases, regulations did not increase
conservation efforts.
The ESA requires the preparation of a recovery plan for each listed
species, unless the department secretaries find that a recovery plan will
not further the recovery of a particular species. It allows for the forma-
tion of recovery teams responsible for developing recovery plans. The
objective of a plan is the survival and eventual recovery of a listed species
or population, so that it can be removed from the endangered or threat-
ened list.
The recovery plan for sea turtles prepared by the Marine Turtle Recov-
ery Team was approved by NMFS in 1984. The plan, based on the best
available information, recognized the difficulty of managing species that
migrate outside U.S. jurisdiction and are commercially exploited in other
countries. Within U.S. jurisdiction, the plan recommended management
practices to enhance production on nesting beaches and to reduce mor
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120
Conservation Measures
tality at sea and on land. Updated recovery plans for each species will be
released in 1990. In general, recommendations of this committee are
consistent with those of the 1984 recovery plan for marine turtles, but
more recent or continuing declines of some species caused the committee
to enlarge its set of recommendations.
DESCRIPIlON OF CONSERVATION MEASURES
In this and the following sections, the committee relied on draft recov-
ery plans for material on beach management and education.
Increasing or Mainhining the Supply of Sea Turtle Eggs
and Hatchlings
Some approaches are aimed at increasing the supply of sea turtle
hatchlings that enter the ocean system and eventually join the breeding
population. Management measures range from protection of habitats
(particularly critical nesting habitats) to captive breeding and programs of
delayed release of young turtles.
Increasing Protection of Critical Nesting Habihts
Land Use
A joint state, federal, and private effort is under way to provide perma-
nent protection for 15 km of the approximately 34 km of high-density sea
turtle nesting habitat between Melbourne Beach and Wabasso Beach, on
the Atlantic coast of east-central Florida (Possardt and Jackson, 19891. In
that area, loggerhead nesting averages 475 nests/km in Brevard County
and 140 nests/km in Indian River County. About 35-40% of green turtle
nesting and 25% of loggerhead nesting in the southeastern United States
occurs in southern Brevard County and northern Indian River County.
Purchase of undeveloped beach property along that stretch (acquisition
of "in-fee title") is the best way to conserve it. Obtaining conservation
easements on undeveloped beach property will not be sufficient to
ensure long-term protection. Only if the "in-fee titles" are acquired will
the continued protection of this critical nesting beach be ensured,
because only then will full control rest with land management authorities.
If condominiums and other structures are built behind the nesting beach,
the beach will eventually be lost as a result of storms or rising sea levels,
because it will not be able to migrate naturally.
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121
Decline of the Sea Turtles
Erosion
Efforts to mitigate the effects of erosion usually consist of transferring
nests to higher sites on a dune or into a hatchery. Those have now
become common practices on many nesting beaches throughout the nest-
ing range of the loggerhead and other species. Relocation projects are
authorized under state and federal permits.
Beach Armoring
The destructive use of sea walls and other means of beach armoring
(see Chapter 6) continues as a rising sea level erodes private property
and threatens existing homes and other human structures. States have
not taken the drastic action of removing or prohibiting construction of sea
walls, but efforts are under way to adjust zoning so as to avoid the need
for beach armoring on currently undeveloped lands. Most zoning ordi-
nances are at the county level.
Beach Nourishment
Beach nourishment is less destructive of sea turtle nesting habitat than
is beach armoring, but it can cause problems for nesting females and
nests if not done properly. NMFS regulates beach-nourishment projects
in behalf of the sea turtles and requires mitigation measures through the
mechanism of Section 7 ("Consultation") of the ESA. Such regulation is
possible, because nearly all beach-nourishment projects receive federal
aid and therefore require endangered-species consultations. In Florida,
much beach nourishment occurs in the summer, and nests must be
moved from the beach before nourishment (e.g., Wolf, 19891. The quality
of nourishment material must be acceptable to nesting sea turtles (Nelson
and Dickerson, 1989a). The policy of beach nourishment is under contin-
uing review by the Fish and Wildlife Service, Army Corps of Engineers,
and the Florida Department of Natural Resources.
Increasing Protection of Nesting Adults, Eggs, and Hatchlings
Artificial Lighting
Considerable progress has been made in developing artificial lighting
that does not compromise the efforts of nesting turtles or the emergence
of the hatchlings (Dickerson and Nelson, 1988, 1989; Nelson and Dicker-
son, 1989b), particularly low-pressure sodium lights that appear to have a
minimal effect on sea turtle orientation. Low-pressure sodium lights still
prompt some concerns, and research continues.
In the absence of acceptable lighting, many states, counties, and towns
are making progress in mitigating the effects of light (pers. comm., L.
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122
Conservation Measures
Shoup and R. Wolf, Alachua County Department of Environmental Ser-
vices, Gainesville, Florida, 1987; pers. comm., R. Ernest, Applied Biology,
Inc., Jensen Beach, Florida, 19901. In Florida, lighting ordinances have
been passed in several counties and are being considered in others (pers.
comm., I. Huff, Florida Department of Natural Resources, 19891.
Becch Clecning, Pedestrian and
Vehicular Traffic, and Recrec fional Equipment
Beach-cleaning equipment, pedestrian traffic, off-road vehicles, and
other human activities disturb nesting sea turtles considerably and can
destroy eggs and hatchlings. Off-road vehicles are regulated on many
beaches, but are still allowed on the beaches of North Carolina, Georgia,
parts of northern Florida, and Texas. The pedestrian traffic problem is
often solved by moving nests out of the way of beach access ramps or
marking their presence in such a way that beach users will avoid them.
On the beach at Boca Raton, small screen cages are placed over the nests
(pers. comm., R. Wolf, Alachua County Department of Environmental Ser-
vices, Gainesville, Florida, 19871; this practice also protects nests from
beach-cleaning equipment, if the nests are not moved before cleaning.
At night, nesting turtles are easily disturbed by humans on the beach.
Murphy (1985) reported that beach disturbance can cause turtles to shift
their nesting beaches, delay egg-laying, and select poor nesting sites.
Public education is being used to alleviate the problem.
Experimental' Conservation Practices
Hec dstarting
"Headstarting" is the term used to describe an experimental procedure
wherein hatchlings are retained in captivity and reared for at least several
months to increase the juvenile population by reducing hatchling mortali-
ty. Despite several years of the headstart programs and the development
of good husbandry techniques at some facilities, the value of the tech-
nique is still debated. Survival of headstart turtles for several years in the
wild has been documented, but no nesters of headstart origin have been
found. Supporters of headstarting argue that recruits might have been
missed, that tags fall off, that there has not been enough time for them to
reach adulthood, and that the public-awareness component of having
many turtles in tanks for people to see is an important positive result of
headstarting. From the research point of view, headstarting has proved
valuable in increasing understanding about elements of physiology and
behavior of sea turtles (Owens et al., 19821. In 1989, Florida decided to
terminate its 30-year-old green turtle and loggerhead headstart program
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123
Decline of the Sea Turtles
on the grounds that "possible interference with imprinting mechanisms
that guide turtles to the nesting beach, imbalance in sex ratios from artifi-
cial incubation of eggs, nutritional deficiency from confined maintenance
of hatchlings, and behavioral modifications are all potentially serious
problems that are cause for concern" (Huff, 19891. In addition, the prac
. . .
trace Is expensive.
The U.S.-Mexico cooperative headstart program for the Kemp's ridley
has been the responsibility of the NMFS Galveston laboratory since 1978.
Entry of headstarted turtles into the nesting population has not yet been
documented. Wibbels et al. (1989) recommended that headstarting be
continued as a research project but that the effort not be expanded.
They also suggested that increase in public awareness of the sea turtle
situation and the development of strong international collaborative ties
between the United States and Mexico were both worthwhile aspects of
this particular headstart experiment.
We found no adequate sample of natural hatchling survival against
which to judge the success of headstarting. Also, headstarted turtles
might be too naive to survive in the wild, and that could undo any posi-
tive effects of avoiding the high early mortality in nature.
Before evaluating the headstarting experiment and determining
whether the technique should become a conservation practice, one must
consider whether four sequential milestones have been reached. In
order of achievement, they are growth and survival of headstarted turtles
once they are introduced into the wild, nesting of some headstarted tur-
tles on a natural beach, nesting of enough turtles to contribute to the
maintenance or recovery of the population, and demonstration that a
headstarted turtle is more likely to survive and reproduce than one
released as a hatchling. There are still reservations concerning the first
milestone in that some released headstarted turtles appear to show mal-
adaptive behavior patterns, such as swimming up to boats in marinas or
crawling on beaches (pers. comm., K. Bjorndal, University of Florida,
19893; nevertheless, many recaptures indicate that turtles are feeding and
growing in the wild (Manzella et al., 19881. There is no indication of suc-
cess regarding the remaining milestones in any headstart experiment.
During the 11 veers of the experiment. .suh.stantial imorovement.s in
the protocol have been introduced as new technology and experiential
insights have been realized. Specifically, during the early years, male-
skewed sex ratios were produced (Shaver et al., 1988), and suboptimal or
More recently,
improved physical-fitness techniques have been developed, improved
health-care and nutrition practices have been implemented, new tagging
technologies have been adapted to improve the likelihood of identifying
headstart turtles after several years in the wild, and the Padre Island artifi
trawler-occupied release sites occasionally were used.
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124
Conservation Measures
cial imprinting component has been discontinued. In effect, the current
experiments are quite different from the original design and offer clearly
improved chances for success.
The Kemp's ridley headstart program is a continuing research program
that has produced useful information on sea turtle husbandry, behavior,
and physiology. However, it is not yet considered to be a long-term
management tool in the recovery of endangered sea turtles. It is unlikely
that headstarting will ever meet its goal of increased recruitment into the
adult populations without a simultaneous reduction in juvenile mortality
in the wild based on the analysis of reproductive value by Crouse et al.
(19871.
Captive Breeding
Loggerheads, green turtles, and Kemp's ridleys have been raised in
captivity from eggs to adults. The same species have laid fertile eggs in
captivity. The Cayman Turtle Farm, Ltd., on Grand Cayman Island, has
had the most notable success in that regard, rearing both green turtles
and Kemp's ridleys from eggs to reproductive adults (Wood and Wood,
1980, 19841. Of the three "experimental conservation" practices most
commonly attempted with sea turtles (headstarting, artificial imprinting,
and captive breeding), only captive breeding has actually been shown to
be successful. Thus, a worst-case alternative strategy to save the sea tur-
tle species in captivity is available, in case they ever disappear from the
wild (Owens, 1981~. In the case of the Kemp's ridley, retaining captive
individuals could serve as a form of genetic insurance, in case a cata-
strophic event wiped out most of the natural population. The committee
emphasizes that this approach would be a method of last resort, and a
risky one at best, because captive animals in an aquarium or zoo retain
only a portion of the genetic material of their species in the wild.
Artificial Imprinting
Carr (1967) discussed the theory of natal beach olfactory imprinting as
it might apply in marine turtles. An extension of this theory is the experi-
mental application of artificial imprinting, in which it has been assumed
that, if hatchlings do imprint, the imprinting cues can be altered to a new
beach by relocating the eggs to the new beach for their incubation and
hatching, emergence, and movement of hatchlings into the ocean. In this
process, it has been hoped that new nesting sites could be created or old
ones restored. Whereas the entire process is not well understood or
proven, some limited evidence suggests that it does occur (Grassman et
al., 1984) but that it might be more complicated than initially thought
(Owens and Morris, 1985; Grassman and Owens, 19871. Owens et al.
(1982) discuss the implications of artificial imprinting in conservation.
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Decline of the Sea Turtles
REDUCING ADULT AND SUBADULT MORTALITY
ASSOCIATED WITH HUMAN ACTIVITIES
Intentional Harvest of Sea Turtles
The deliberate capture of sea turtles was outlawed in the United States
by the progressive inclusion of the various species on the Department of
the Interior lists of endangered and threatened species. That action pro-
tected domestic populations of sea turtles and their eggs, and also out-
lawed the commercial importation and sale of all sea turtles and their
products.
The extent of breach of the regulations within the United States is
obviously difficult to assess. However, although occasional persons
reportedly are apprehended with a few hundred turtle eggs gathered or
offered for sale, the problem does not appear to be serious, compared
with the loss of eggs through other causes (e.g., beach erosion) or the
loss of immature or mature turtles to incidental capture.
Outside the United States, various laws apply, with various degrees of
success. Most nations of the wider Caribbean basin are now parties to
the Convention on International Trade in Endangered Species (CITES),
which legally bars them from engaging in international commerce in sea
turtles and their products. Moreover, turtle eggs receive legal protection
in many countries, including Mexico, where sea turtle eggs of all kinds
first received legal protection in the Tabla General de Vedas (General
Schedule of Closed Seasons), which has been strengthened and extended
several times by laws that protect turtles or establish closed seasons for
them. A terrestrial reserve and a no-trawling zone have been established
in the area critical for Kemp's ridleys in southern Tamaulipas. It is most
important that compliance with these laws be strictly enforced. Human
harvest of turtle eggs and slaughter of animals continue to be potential
problems in Mexico; at the Rancho Nuevo beach, Kemp's ridley eggs
must be and are removed to a protected hatchery within hours of their
being laid to avoid predation by coyotes or humans.
In the Bahamas, complete protection is given to all life stages of the
hawksbill, and eggs and nesting females of all turtle species are protect-
ed. There is a closed season on the harvest of all turtles from April 1
until July 31, and minimum-size limits are in effect for green turtles (60
cm SCL) and loggerheads (76 cm SCL) for the rest of the year.
Leatherbacks are seen only rarely in the Bahamas and are not taken for
food. Kemp's ridleys have not been reported in the Bahamas. Enforce-
ment of regulations, particularly in the more remote islands, is difficult.
In most of the Caribbean, sea turtles have at least some legal protec-
tion at some times, although enforcement is often lacking. Costa Rica ini
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126
Conservation Measures
tiated a legal quota of 1,800 green turtles per year in 1983, but lowering
of the quota is being considered. Although the committee is concerned
about the effects of intentional harvest outside the United States on sea
turtle populations, it has not been able to quantify the extent of the prob-
lem.
Incidents' Capture of Seo Turtles
Shrimp-Fishing Operations
Various fisheries in U.S. waters have an impact on sea turtles. Deaths
related to some fisheries have been well documented (see Chapter 6), in
particular the bottom-trawl fisheries of the Gulf of Mexico and the south
Atlantic states. Several management tools are available for reducing the
impact and might be used in combination for optimal management.
Regulation of fisheries typically uses one or more of the following
approaches: limiting the number of individuals that may be captured
(zero, in the case of endangered species), limiting the amount of fishing
effort with a particular gear type, and controlling the efficiency of a par-
ticular gear type. Effort is the amount of time a particular gear type is
used; efficiency can be thought of as a measure of a particular gear type's
tendency to capture or kill organisms of a target species.
Controlling Trawling Effort
Limitations on trawl-fishing effort can span a continuum from sweep-
ing bans on the use of trawl gear to focused time and area closures.
Legal authority for any of those measures can be found in the Endan-
gered Species Act.
An absolute ban on trawling in waters where encounters with sea tur-
tles occur has advantages for eliminating trawl-related turtle deaths and
for ease of enforcement. But its socioeconomic impacts are equally clear,
constituting an impressive array of disadvantages.
A less extreme approach is to implement time and area closures to
reduce the impact of trawling as turtles occupy an area or are especially
vulnerable to trawl-related death; this approach has already been used off
Rancho Nuevo in Mexico during the nesting season of Kemp's ridleys.
"Area" could be defined to include depth zones, as well as more conven
The greatest disadvantage of time and area
closures is that their broad application on fine time/space scales might
require more and better information than is available on the distribution
of sea turtles (see Chapter 41. If such information became available,
enforcing such closures might still be challenging, given the difficulties of
tional geographic regions.
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127
Decline of the Sea Turtles
tracking numerous fishing vessels and monitoring their activities. Another
problem might arise if the times and areas closed were so great or coin-
cided so closely with optimal fishing patterns as to make fishing uneco-
nomical.
In several areas and times of the year, turtles might be sufficiently low
in abundance that shrimp fishing could be conducted without the use of
tow-time restrictions or turtle excluder devices. One area that should be
considered is water deeper than about 27 m in the Gulf of Mexico, where
juvenile and adult turtles apparently are only about one-tenth as abun-
dant as in shallower waters (see Chapter 41. Some shrimp fishing occurs
at that and greater depths in the gulf. It would be necessary to reevaluate
the practice after sea turtle populations began to recover and turtle abun-
dance increased in the gulf, to be certain that any turtles on or near the
surface were not captured.
The potential of shrimping in fishing zones and times of the year
where damage to turtle populations would be minimal without turtle
excluder devices or tow-time restrictions should be examined in detail,
initially from existing data bases. Some of the difficulties in devising such
a management scheme on a large scale become apparent when one
examines the material in Chapter 4 on distribution and Chapter 6 on
sources of mortality associated with human activities. First, there is a
great deal of overlap in the distribution of sea turtles and fishing effort
throughout the year. Second, most measures of turtle abundance are not
independent of fishing effort; for example, sea turtle strandings are the
result of a complex interaction between sea turtle abundance and shrimp
trawling (Chapter 61. Third, aerial surveys, although independent of fish-
ing effort, do not detect the smaller turtles such as Kemp's ridleys and
juvenile loggerheads, both of which require protection. Fourth, areas in
which turtles are now rare enough at some times of the year not to be
caught in trawls might be that way only because populations are severely
depleted.
Manipulating Trawl Selectivity and Efficiency
Negative effects of trawling can be reduced by modifying the gear so
that it will not capture sea turtles or so that captured turtles can escape
from the trawl gear without harm. Such modifications can be used in
conjunction with effort limitations, as is called for in existing regulations.
The various TEDs approved by NMFS are all designed to be installed
in shrimp-trawl gear with the purpose of releasing sea turtles and other
large objects from the net without releasing shrimp. Such a separation is
mechanically feasible, because turtles are so much larger than shrimp. To
some degree, the effectiveness of separation also relies on differences in
behavior of various species trapped in a trawl.
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128
Conservation Measures
Because of the relatively high concentrations of sea turtles in the ocean
waters offshore of the Cape Canaveral region of Florida's east coast,
NMFS has used this area to assess the effectiveness of alternatively
designed TEDs. If a particular TED can be shown to exclude at least 97%
of the sea turtles otherwise captured and retained in a control trawl with-
out a TED, that TED is certified by NMFS as an approved TED that meets
the requirements of the regulation.
By November 1989, six different
TEDs had met the minimal criterion for excluding sea turtles and have
been approved: the NMFS TED, the Georgia jumper TED, the Cameron
TED, the Matagorda TED, the Morrison soft TED, and the Parrish soft
TED. (See Appendix C for diagrams of approved TEDs.)
Although each approved TED effectively excludes sea turtles, a TED
need not be effective in retaining shrimp to be approved. Furthermore,
NMFS is under no legal obligation to assess the effectiveness of each
approved TED in retaining shrimp. Nevertheless, a TED is of no value to
. , _
. ~ ~ · it- 1 ~ ~ ·. 1 1 ~ 1 · _1 ~ ~ ~c ~ ~ ~ :_ +~+
the shrimp fishery it it excludes too n1gn a percemage or me snr1mp anal
would otherwise have been caught. In announcing the June 27, 1987,
regulation that required use of TEDs by shrimp trawlers in most shrimp-
ing grounds during most of the shrimping season in the Southeast, NMFS
referred to its own test data on the effectiveness of the NMFS TED in
excluding sea turtles in offshore waters around Cape Canaveral and
v ~ ~ , l ~ _ _ ~ 1 _ ~
retaining shrimp under commercial shrimp trawling In most sournea~ern
states (Federal Register, Vol. 52, No. 124, pp. 24244-242621. During TED
tests for excluding turtles at Canaveral, low concentrations of algae,
debris, and shrimp were encountered. Shrimp loss was very low, averag-
ing a statistically nonsignificant 4% of total numbers and total poundage.
Other TEDs might be less effective in retaining shrimp under the same
conditions; the (modified) Parrish soft TED, for example, was approved,
because it met the minimal standards for excluding sea turtles, but it lost
80% of the shrimp catch as compared with the control (Federal Register,
Vol. 53, No. 170, pp. 33820-338211.
Numerous tests of the effectiveness of different TEDs in retaining
shrimp and of modifications of TED assembly and installation have now
been conducted by NMFS, Sea Grant researchers, and state fisheries a.~en
cies. It is clear that shrimping efficiency or trawls equipped with TEDs is
highly variable based on differences in the specific TED, location, and
shrimping conditions. For example, Report No. 7 of the NMFS Observer
Program for TEDs documents a range of effects of TED use on shrimp
catch of ~5% to +380/0 by weight. The average effect of TED use varied
across test regions from-2% to -27%, with most region-specific means
. , , . A, ,
between At% and -150/0 (pers. comm., E. Klima, NMFS, 1989).
Understanding the variation in shrimping efficiency of TED-equipped
trawls is necessary for an evaluation of whether TEDs constitute a solu
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133
Decline of the Sea Turtles
FIGURE 7-1 Relation between percentage of dead and comatose sea tur-
tles (mostly loggerheads) in summer versus winter as a function of tow
time of trawls (data from Figure 6-3, broken down by season). Top:
dead turtles; bottom: dead plus comatose turtles. Total numbers of tur-
tles captured: winter 2,490; summer 1,907. Compiled by the commit-
tee from raw data provided by NMFS, which were the basis for Hen-
wood and Stuntz's (1987) calculations.
100
75
~ WINTER
-SUMMER
o WINTER
-SUMMER
PERCENT
DEAD 50
25
O
100
75- .
PERCENT
DEAD + 50
COMATOSE
2S
."
! n n . ~
O 60 120 180 240
TOW TIME (MIN)
it,
of o
o60 120 160 240
TOW TIME (MIN)
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134
Conservation Measures
comatose turtles vary with tow time as an upper limit on mortality. Those
numbers are far larger than the numbers of dead alone and, if they
reflected true mortality of sea turtles, would suggest a need for further
reduction in tow times to protect sea turtles from drowning. Specifically,
winter tows might need to be restricted to 60 minutes or less, instead of
less than 90 minutes, whereas the 40-minute restriction in the summer
seems sufficient.
Tow-time limitation could be as effective as TEDs in reducing the mor-
tality of sea turtles in shrimp trawls, but might be extremely complex as a
management option, because of differences in seasons and locations.
The regulations would need to vary with season, to allow the most effi-
cient shrimping while still protecting the turtles. However, the brevity of
acceptable tow times results in a cost to shrimpers, because their nets are
fishing for a smaller fraction of the day. Given the relatively small shrimp
losses demonstrated in offshore shrimping with the most efficient TED
(e.g., Holland, 1989; pers. comm., E. Klima, NMFS, 1989), it seems likely
that shrimpers fishing in the offshore waters would catch more shrimp by
using a TED than by restricting tow times to 40 minutes in the summer
and 60 minutes in the winter. In inshore waters and in other situations
with concentrated plant and other debris, trawl times are necessarily limit-
ed, usually to less than 90 min. by the accumulated weight of debris
(including finfish bycatch) in the trawl. Under those conditions, imposi-
tion of a tow-time restriction adds little cost to what nature imposes.
Those are also conditions under which TEDs fail to retain a high fraction
of the shrimp entering a trawl and, more important, under which the
effectiveness of many TED designs in releasing turtles might be compro-
mised. Thus, tow-time limitation in coastal waters of estuaries, sounds,
lagoons, and embayments constitutes a sensible management tool in
some areas. The 1987 NMFS regulation recognized a 90-minute tow time
as an alternate to TED use in inshore waters only.
A major concern regarding the use of tow-time limitation as a manage-
ment tool is how it can be enforced. The problem has not been solved,
but new technology could be directed toward engineering a device to
record submergence time. Enforcing proper use of TEDs is also a major
concern, because TEDs can be readily disabled by altering the tension of
spring cords or tying them in a fashion virtually undetectable by inspec-
tors. All this suggests a need for evaluation of the effectiveness of regula-
tions of the shrimp-trawl fishery.
The physiology of prolonged forced submergence needs further study,
to allow for the complete evaluation of the use of tow-time limits in trawl
fisheries. Even a "normal" appearing turtle that has survived 60 minutes
of compression and forced submergence might have lung, heart, or other
vital organ damage (Manzella et al., 19881. How enforced submergence
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Decline of the Sea Turtles
affects sea turtle physiology as a function of season, water temperature,
turtle species and size, time of day, and history of previous enforced sub-
mergence is not well known. For example, is recapture more likely in
turtles that have just been released from another trawl? The impact of
multiple recaptures on sea turtle survival might lessen the effectiveness of
reduced tow-time regulations in saving turtles.
Finally, there is the persistent question of multiple physiological stress-
es that might act on one another. The potential needs further evaluation,
although we do not believe that a shortage of knowledge affects the rec-
ommended conservation measures identified in this report. Wolke (1989)
believed that the health of many of the dead sea turtles that he necrop-
sied might have been compromised by parasites. After a decade of
observer programs in which fresh carcasses have been available from
trawls, it is surprising that so few necropsies have been done on fresh
wild carcasses. Much more could be learned about the physiological con-
dition of sea turtle populations and the possible interactive effects of mul-
tiple stresses, if more professional necropsies are performed on fresh car
casses.
Other Commercial Fishing Activities
Various commercial fishing activities besides shrimp trawling kill sea
turtles. In some cases, turtle deaths have been observed (Chapter 6~; in
other cases, no observations were made, but the nature of the fishery or
other considerations suggested at least a potential for harmful encounters.
Some closures have been implemented for fisheries other than shrimp
fisheries. Ocean gill nets set to capture .stllr~on aria nm~xl r~rmLihit~rl her
rat in 1 .
~e snores regu~anons in both North Carolina and South Carolina,
reducing the incidence of sea turtle mortality apparently associated with
this activity (Murphy and Hopkins-Murphy, 19899.
change in mesh size could reduce entanglement of sea turtles.
Dredging, Boat Collisions, and Oil-Rig Removal
For set net fisheries.
Dredging, boat collisions, and oil-rig removal were each estimated to
kill from 50 to 500 loggerheads and five to 50 Kemp's ridleys a year, if
mitigation or conservation measures were not in place.
Dredging
When it was first noted that large numbers of turtles were being taken
by dredging within the Canaveral Channel Joyce, 1982), NMFS and the
Jacksonville District of the U.S. Army Corps of Engineers took immediate
action to reduce the problem, including the relocation of 1,250 logger
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Conservation Measures
heads from the Canaveral Entrance Channel to areas offshore for the
remainder of the dredging operation Joyce, 19821. The relocation effort
proved to be less than successful: many of the displaced animals
returned to the channel in an unacceptably short period. However,
another relocation effort in December 1989 and January 1990 in the Cape
Canaveral Channel was successful; no relocated animal was recaptured in
the channel (pers. comm., A. Bolten, University of Florida, 19891.
Through the mechanism of Section 7 consultations provided by the
Endangered Species Act of 1973, a Sea Turtle Dredging Task Force was
created in 1981 to respond to concerns by NMFS about the unacceptably
large numbers of sea turtles taken during 1980. Members of the task
force included representatives of the Army Corps of Engineers, NMFS, the
_ . · .. ... ~ ~ -
U.S. Fish and w~e Service, the Florida Department of National
Resources, and the Navy (Studs, 19871. A number of continuing actions
have been initiated by the task force to document and mitigate sea turtle
losses:
· Initiation of an observer program with on-board biologists to doc?~-
ment the take of sea turtles by dredges, including the modification of
gear to screen discharge ports for the presence of sea turtle parts. The
observer Program w. as initiated at the Port Canaveral Entrance Chan
~ % ~ 1 . . 1 ~ . ~ ~ ~ ~ ~ . ~ ~ ~ 1 : ~
net in 198() (Joyce, 196;~) ana at me ~I. 1vlaryS nIlLraIl~e ~llullllC1111
1987 (Slay and Richardson, 1988; Richardson, 19901. The observer
program will be expanded to additional harbor-entrance dredging
operations along the Eastern Seaboard, the Gulf of Mexico, and
Puerto Rico, wherever sea turtles are known to occur and as oppor-
tunity permits (pers. comm., T. Henwood, NMFS, 19891.
· Investigation of the configuration and relative threat to sea turtles of
various types of dredges and dredge dragheads. Sea turtle take has
been associated primarily with hopper dredges used for offshore
channel dredging. Hydraulic cutterhead dredges and bucket
dredges, used primarily for inshore work do not appear to affect
sea turtles to a significant degree.
A ~ ~
1 A
Relative to hopper dredges,
investigations in 1981 and 1982 identified the California type of
draghead as the least damaging (Joyce, 1982) and the gear of choice
for Port Canaveral. However, the take of sea turtles with the Califor-
nia draghead in the Port Canaveral Entrance Channel since 1980 has
been found unacceptable by NMFS (pers. comm., T. Henwood,
NMFS, 1989), so alternative dredging methods and gear types are
now being sought for this channel.
· Design and test modifications of hopper-dredge dragheads. Various
deflector systems have been tested, with minimal success because of
the powerful suction force of the intake water and because of the
destructive mechanical forces applied to the deflector apparatus on
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Decline of the Sea Turtles
the channel bottom (Studs, 19871. Efforts continue to develop a
functional deflector for dragheads used in the Port Canaveral
Entrance Channel during maintenance dredging (pers. comm., T.
Henwood, NMFS, 19891.
· Investigation of various sensory stimuli to repel turtles from the
channel to be dredged orfrom the vicinity of the dredge. Investiga-
tions have not had results that can be applied to mitigation of turtle
take by hopper dredges (Studs, 19871. Air guns used in seismic
exploration did not deter sea turtles at the Turkey Point, Florida,
power plant (pers. comm., I. O'Hara, Environmental and Chemical
Sciences, 19891. It is unknown what further research efforts might
be attempted in this area.
· Radio-tracking studies of sea turtles in the navigation channels.
Nineteen loggerheads were tracked in the Port Canaveral Entrance
Channel in 1982 (Nelson et al., 19871. Valuable behavioral informa-
tion was obtained that could be used for censuses, such as the pro-
portion of time spent on the surface and the number of surfacings
per hour by an average turtle. Movements of the turtles in the chan-
nel and between adjacent habitats proved unpredictable and did not
lead to suggestions for mitigation.
· Determination of the frequency and distribution of sea turtles in key
navigation channels of Flor~da's coast and elsewhere. Several cen-
suses of sea turtle populations in the Port Canaveral Entrance Chan-
nel have been conducted since 1980 (Henwood, 1987) and are con-
tinuing. Early results indicated that sea turtles were present in
considerable numbers at all times of the year, but in the lowest
numbers during September, October, and November (Studs, 19871.
Dredging at Canaveral was then restricted to that 3-month period.
Seasonal dredging is considered the most important available miti-
gation measure.
The committee did not have time to analyze the recent Army Corps of
Engineers report (Dickerson and Nelson, 1990), but we note that many of
its suggested studies are similar to those in the present report.
Collisions with Boats
Estimates of mortality from collisions with boats are uncertain, because
the assessment of wounds on stranded animals usually cannot determine
whether the turtles were hit before or after they were dead and floating
in the ocean. Wounds should be photographed and measured to be cer-
tain of their origin. In addition, there are no estimates of collisions in
inside waters.
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Conservation Measures
Because 50-500 loggerheads and 5-50 Kemp's ridleys might be killed
each year (Table 6-2), judging by the incidence of wounds on stranded
animals, a better assessment is needed than is provided by the stranding
network. If geographic areas of critical concern are found, methods like
those imposed for protection of manatees from boat collisions should be
implemented in selected waters off nesting beaches. Distributing infor-
mation on the problem to boat owners could be helpful, but, because
human-turtle interactions are so widely dispersed, substantial reductions
in mortality are unlikely.
Oil-Rig Removal
Sea turtle species and turtles in different life stages within species often
segregate by habitat preference. The deployment of underwater struc-
tures (oil-platform tripods, towers, anchors, sediment-control devices,
ocean cables, and the like) and other marine activities (mining and
drilling) might promote formation of local concentrations of sea turtles in
unpredictable ways. The feasibility of removing turtles from the vicinity
of all planned explosive detonations must be investigated.
Power Plant Entrainment
Power plants have minimal influence on sea turtles, killing perhaps 5-
50 loggerheads and Kemp's ridleys each year. The measures described in
Chapter 6 that are now in place for the St. Lucie No. 2 plant seem ade-
quate and should be continued. Further evaluation and intake system
modifications might eventually be necessary at other plants, where larger
numbers of turtles could be entrained and killed as populations increase
in the future.
Ingestion of Plastics, Debris, and Toxic Substances
There is ample evidence that sea turtles ingest plastics and other indi-
gestible materials of human origin (see Chapter 61. For example, Plotkin
and Amos (1988) found plastics and other debris of human origin in 46%
of 76 carcasses necropsied on the Texas coast. Further documentation is
needed of the extent of the problem, particularly the mortality rate associ-
ated with ingestion, the physiological response of the animal to ingested
materials of different types and particle sizes, and the behavioral response
of turtles to oceanic debris.
All carcasses should be checked for the presence of ingested plastics.
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Decline of the Sea Turtles
Drift lines of sargassum and other materials at sea should be checked for
the presence and characteristics of plastics and for the occurrence of tur-
tles ingesting plastics. Materials found at sea and on beaches should be
checked for evidence of feeding by turtles. The tendencies of turtles to
ingest plastic debris of various types, particle sizes, and colors should be
checked under controlled conditions. The ability of selected research ani-
mals to pass ingested plastics of particular types and particle sizes without
physiological damage should be determined. The wording of MARPOL
and other ocean and coastline dumping regulations should be examined
for applicability to the problem of plastics ingestion by sea turtles, partic-
ularly statements related to maximal allowable particle size of shredded
materials discarded overboard, and the implementation effectiveness of
dumping regulations should be investigated.
Additional information is needed on the reaction of sea turtles to
petroleum ingestion, fouling, and toxicity. Fritts and McGehee (1981)
found that sea turtle eggs contaminated with fresh crude oil, as might
occur after an oil spill, yielded a lower hatch rate and a higher percentage
of deformities. They did not, however, investigate the effects of floating
oil on the behavior of animals in the water-courting, mating, feeding,
and the like. Lutz and Lutcavage (1989) exposed young loggerheads to
very brief contact with crude oil and found reduced hematocrit measure-
ments, modified behavior, and alterations in skin epithelium. They felt
that more work was required to document fully the impacts of crude oil.
Sea turtles ingest tar (which is chemically passive) and oil droplets (chem-
ically active) that they appear to mistake for food particles (Witham, 1978;
Lutz and Lutcavage, 19891. Such materials are abundant in the pelagic
environment, particularly in drift lines, so a better understanding of the
physiology of ingestion of these materials as they pass through the intes
-
tine is needed.
Drift lines and samples of plankton and ocean-surface particles should
be checked for the presence and characteristics of crude-oil derivatives.
The presence and effect of tar should be documented at all necropsy
opportunities, including correlation of particle size and abundance with
size and condition of turtle by species. Moribund animals should be
looked for in the vicinity of oil spills and concentrations of petroleum par-
ticles, especially in the Gulf of Mexico where Kemp's ridleys are found.
The physiological response of selected animals of different sizes and
species to ingestion of floating tar particles passing through the intestine
of the research animals should be investigated. And the wording, imple-
mentation, and enforcement of national oil-spill regulations and interna-
tional protocol should be checked for responsiveness to the needs of sea
turtle conservation.
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Conservation Measures
EDUCATION AND TECHNOLOGY TRANSFER
Education with respect to beach management, reduction of human-
associated mortality of eggs and hatchlings, and the implementation of
technology is important for the conservation of sea turtles. We present
here some information on education with respect to beach management,
but also focus attention on the implementation of TED technology in the
shrimping industry. It will always be difficult to implement an important
conservation measure if it is viewed as an economic liability to the user;
education should promote the implementation of new useful measures.
Education
One of the easiest ways to implement good beach management is to
inform and educate the public. Beach residents conducting turtle projects
often advise tourists on what they can do to minimize disturbance to nest-
ing turtles, protect nests, and rescue disoriented hatchlings. Similarly,
state, federal, and local parks that conduct beach walks provide informa-
tion to visitors. Beaches are also posted with signs informing people of
the laws that protect sea turtles and providing a local or hotline number
for reporting violations.
A wide variety of materials are available (e.g., children's coloring
books, posters, slide-tape programs, brochures, and fact sheets) from the
Center for Marine Conservation, Florida Power and Light Co., NMFS, FWS,
and environmental groups.
TED Technology Transfer
One of the responsibilities of NMFS is to monitor and enforce provi-
sions of the Endangered Species Act. NMFS Southeast Regional Office
programs include regulation development, recovery planning and imple-
mentation, information dissemination, TED certification, and permit
administration. Research activities involve TED technology transfer (pro-
viding assistance to industry and evaluating TEDs for certification), TED
economic evaluation (tow-time observer program), TED-regulation evalu-
ation (systematic strandings), sea turtle biology and ecology, and Kemp's
ridley headstarting (Oravetz, 19891.
NMFS sea turtle program funding since 1977 has averaged $890,400 a
year, starting at $250,000 in 1977 and with a high of $1,150,000 in 1982.
Sources of additional funding have been Marine Fisheries Initiatives
(MARFIN), the Entanglement Network, the Army Corps of Engineers, the
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Decline of the Sea Turtles
Minerals Management Service, the shrimp industry, the National Sea Grant
College Program, FWS, various regional power plants, and Saltonstall-
Kennedy (S-K) funds. Current contracts with the Gulf and South Atlantic
Fisheries Development Foundation (GSAFDF) total $862,000 (MARFIN and
S-K) and are being used to coordinate industry and Sea Grant efforts in
TED testing, development, and technology transfer.
The responsibilities of at least 21 NMFS employees include some
aspect of TEDs or educating the public about sea turtle conservation. The
NMFS laboratory at Pascagoula, Mississippi, maintains three full-time TED-
gear specialists employed to help fishermen and net shops build and use
TEDs correctly. Four additional gear specialists at the same laboratory
have conducted at-sea TED demonstrations and given many presentations
(pers. comm., C. Oravetz, NMFS, 19891.
Between 1981 and 1986, NMFS conducted programs to encourage the
voluntary use of TEDs by shrimp fishermen. The program involved
workshops and TED demonstrations for shrimp fishermen; commercial
fisheries associations; reporters; and Sea Grant, state and university per-
sonnel. Numerous presentations of TEDs were given at commercial fish-
eries association meetings and conventions and on the docks and on
decks of shrimp trawlers. NMFS has provided 300-400 free TEDs to fish-
ermen to test and use. Slide programs, video tapes, brochures, and
instructional materials on TEDs and on sea turtles and their conservation
and management were also developed and made available (pers. comm.,
C. Oravetz, NMFS, 19891. NMFS changed the meaning of "TED" to "trawl-
ing efficiency device" in 1983, in hopes of making the gear more palat-
able to shrimp fishermen. Few fishermen responded; by 1986, less than
3% of active trawlers had used TEDs (Federal Register, Vol. 52, No. 124,
pp. 24244-242621.
In addition to its inhouse efforts, NMFS cooperates regularly with fish-
ing industry associations and with Sea Grant, state agency, and environ-
mental groups. Sea Grant has been called on to play a major role in edu-
cation, particularly in TED-technology transfer (pers. comm., C. Oravetz,
NMFS, 19891. NMFS contracted with all Sea Grant Marine Advisory and
Extension programs in the Southeast to distribute TEDs to fishermen,
experiment with TEDs, train fishermen to use TEDS, and generally keep
fishermen informed of the ever-changing status of TED regulations.
Sea Grant Marine Advisory and Extension Service personnel throughout
the Southeast were asked to play an integral part in assisting NMFS with
TED testing and technology in their own states. Since 1981, numerous
workshops and demonstrations have been conducted for fishermen and
net-makers. Newsletters continually apprise fishermen of planned work-
shops, demonstrations, and public hearings and of the latest updates of
TED regulations. Educational materials have been developed and dis
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Decline of the Sea Turtles
tributed for some of the certified TEDs, providing diagrams and detailed
instructions for proper placement and use of the TEDs in a trawl. The
R/V Bulldog of the University of Georgia is often used to test and com-
pare TEDs against standard (non-TED) nets and other TED models near
Cape Canaveral, as a precursor to certification. The cruises often include
industry representatives, as well as university, Sea Grant, and NMFS per-
sonnel. Sea Grant personnel have distributed free TEDs, provided lists of
TED manufacturers, and informed fishermen on how to get reimburse-
ment for purchased TEDS from state assistance programs. Some of the
Sea Grant personnel have worked closely with net-makers and commer-
cial fishermen to design new TEDs that will reduce shrimp loss, but still
allowing turtles to escape.
An annotated chronological list of NMFS education efforts centering on
shrimp fishermen and TEDS is found in Appendix G. and documentation
of similar efforts by Sea Grant personnel is listed in Appendix H. Those
appendices provide a detailed overview of the educational programs and
endeavors of the agencies by region and year. A list of educational mate-
rials on TEDs is found in Appendix I.
CONSERVATION EFFORTS IN OTHER JURISDICTIONS
Mexico
Measures taken by Mexico to conserve sea turtles have involved aca-
demics, nongovernmental private groups, and governmental agencies.
Since 1966, government turtle biologists, fisheries inspectors, and armed
Mexican marines have maintained a presence at Rancho Nuevo to protect
nesting Kemp's ridleys, their nests, and eggs. Shrimp trawling offshore of
Rancho Nuevo is restricted. Beach patrols on the gulf and Pacific coasts,
although somewhat spotty, provide some protection against poaching of
adults and eggs for all sea turtles.
The Instituto Nacional de Pesca, in consultation with FWS, has experi-
mented with TEDs, but to date, TEDs have not been adopted as a Mexi-
can governmental regulation in shrimp trawling.
Olive ridleys are legally harvested under a quota arrangement on the
Mexican Pacific coast. By restricting harvest until after the turtles have
nested, the government has afforded some protection to these turtles, but
a drastic lowering of the quota or cessation of harvest should be seriously
considered. Protection of all sea turtle adults and eggs, whether for food,
export, or crafts, should be a prime action by the Mexican government.
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Conservation Measures
Other International Concerns
Worldwide efforts to conserve sea turtles have been identified by
Bjorndal (1981) and Groombridge (19821. Throughout most of their
ranges, sea turtles continue to be under threats of decline from human
activities, and are the continuing subject of intense study, regulation, and
international action and concern. This is well demonstrated by recent
statements and action at the World Herpetological Congress in Canter-
bury, England (September 1989), the Convention on International Trade
in Endangered Species (November 1989), and the International Union for
the Conservation of Nature Marine Turtle Specialist Group.
Representative terms from entire chapter:
sea turtle
