the open sea off Costa Rica that led Hughes and Richard (1974) to
discover the huge nesting arribadas of the olive ridley at Nancite
in Guanacaste. During a two-year residence in Costa Rica, I heard
repeated verbal reports from tuna and sailfish fishermen, and from
commercial airline pilots, that thousands of sea turtles traveling
in schools could sometimes be seen off the Pacific coast at points
between Guanacaste and Panama Bay. I long ago suggested the possibility
that a secretion of the unique marginal pores of Lepidochelys might
serve to draw the migrants together (Carr 1963). “This, however, has
little bearing on the question of why and how immature planktonic
migrants of other species aggregate, especially in view of the fact
that they more often appear to travel separately.

Another important unknown in the developmental ecology of sea
turtles is the mechanism that times and guides the shift of the migrants
from passive epipelagic travel to the inshore, bottom-feeding life
and habitat of the adults. Around the little reefs on the southernmost
coast of Costa Rica where there is no nesting by Caretta I have
occasionally seen young loggerheads, under the Indian River average
size (Fig. 9), and have taken these for accidental strays out of the
offshore current. More regularly, immature loggerheads, mostly smaller
than those seen in U.S. waters, appear in driftlines among the smaller
islands of the West Indies, and along the windward coasts of the big
islands (Meylan 1983a, Carr et at. 1982). None within the Azores
size-range have been recorded there, but juveniles smaller than those
of the Florida colony turn up often. In the Bahamas, Cuba, the Windward
Islands, the Cayman Islands, and the San Andres Archipelago local people
say that they occasionally take loggerheads of these sizes, “most often
in weedlines," where mature loggerheads and green turtles also sometimes
forage (Meylan 1983a, Carr et al. 1982, Carr 1986). These loggerheads
are evidently of distant origin and are too big to have come directly
down-current from the Azores. Where they have passed the intervening
time remains unknown. However, by the time young loggerheads arrive
in Florida waters, they regularly have reached shell lengths greater
than 40 cm, they turn up in large numbers, and they have established
themselves as bottom feeders in benthic habitats.

It thus appears that from the time U.S. loggerhead hatchlings
enter the sea, both before and after they join the Azores developmental
colony and until they show up again as members of the subadult group
of the Indian River lagoons and Canaveral Channel, they either are
making repeated transatlantic crossings in the main Gulf Stream system,
or are circling in rings and minor eddies, feeding at and near the
surface along fronts.

Until recently our attention had been so closely fixed on the
search for the early post-hatchlings that even after these began to
turn up in numbers, due attention was not given the significance of the
lack of American records of loggerheads of the 20 to 40 cm size and
the presence of this age class in eastern Atlantic waters (Carr 1985).
The Azores data provide strong evidence that young loggerheads are
oceanic migrants not just as post-hatchlings, but for a protracted
period of their early development. It seems necessary, therefore,
to give serious consideration to the liklihood that the initial develop-

18



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in the Gulf Stream and its eddies in the area between Florida, Little
Bahama Bank, and Bermuda; (3) colonies of subadults in Indian River,
Mosquito Lagoon, and the Canaveral Nuclear Submarine Channel and along
the southeastern Atlantic coast; and (4) major nesting colonies of
adults along the east coast between Cape Canaveral and Cape Florida.
The subadult colonies of the Indian River Lagoons and Canaveral Channel
are the biggest aggregations of subadult Caretta known in American
waters, or anywhere else for that matter (carr, Ogren, and McVea 1980;
Ehrhart 1983).

I have recently called attention to the fact that when size distri-
bution in these groups. is plotted, a conspicuous gap appears between
the largest of the pelagic U.S. juveniles and the smallest subadults
of the Lagoon and Channel colonies (Carr 1986). To bring these two
classes together would clearly require several years’ growth by the
"lost-year” group. Loggerheads of these intermediate sizes (20 cm
to 40 cm, straight carapace length) are virtually never found anywhere
in U.S. waters. It has long been known, however, that juveniles of
these sizes turn up in the eastern Atlantic from time to time. Dr. Leo
Brongersma has assembled the records in his book, European Atlantic
Turtles (1972). It has often been conjectured that the European turtles
jay come from American breeding grounds and Dr. Brongersma has repeatedly
suggested the possibility that those that appear in southern European
coasts come from and might in some cases eventually return to western
Atlantic waters. On the whole, however, little zoogeographic impor tance
has been attached to their occurrence, on the grounds that they are
probably irretrievably lost to their parent population. The most atten-
tion has been given them by scientists and the news media in the United
Kingdom, where the strays that arrive are in the grip of the North
Atlantic Drift, and so are unlikely to survive the next winter. Sir
Alistair Hardy (1958) during a cruise of the RRS Discovery II, observed
a surprising concentration of young turtles in the North Atlantic Drift.
In early September, 1952, when cruising from the Azores to Cornwall,
the ship passed turtles--which Hardy considered to be loggerheads--all
afternoon and evening, at an average rate of 10 per hour. A few days
later Hardy examined a little loggerhead that had stranded at Bude,
North Cornwall, and found the American alga Ectocarpus mitchellae to
be growing on its shell. TT

A western Atlantic derivation has also been logically assumed
for the infrequent green turtles that appear on the European coast;
and for the more frequent arrivals of Kemp's ridleys (Lepidochelys
kempi), which breeds only on a shore of the Gulf of Mexico and clearly
presupposes a transatlantic crossing.

Virtually all of the sea turtles that strand on the European coast,
and those observed at sea in the Gulf Stream circulation from England
to the Canary Islands are immature. In the Azores we have for some
years been collaborating with Dalberto Pombo of Santa Maria in a tagging
project. The turtles that he tags there are loggerheads. They are
consistently smal] but have not been abundant enough to confirm the
presence of a regular itinerant developmental colony in the area.

By coincidence, however, during the winter of 1984, Helen Martins,
Senior Research Officer in Oceanography at the University of the Azores,

12



the flotsam that is drawn in can't sink, it accumulates along the line.
Resources are mobilized along it, and it is a good place to fish.

In their admirable paper on the accumulation of small depth-keeping,
cold-water fishes in warm-core Gulf Stream rings Olson and Backus (1985)
said this:

More sophisticated time/space sampling of both
physical and biological parameters is needed in

the future in order to provide better insight into
the paradigm of increased biotic activity at fronts.

Until that sampling is done we are bound to remain peculiarly
ignorant of the ecologic organization of three-fifths of the surface
of the earth.

ACKNOWLEDGEMENTS

Financial support for this work was provided by the World Wildlife

Fund (Project No. 1800) and the National Marine Fisheries Service.

The program has had long-term background support from the ‘University
of Florida, Department of Zoology and the Caribbean Conservation
Corporation. Dr. Jeanne Mortimer provided invaluable help in the
preparation of the manuscript, and for expert editorial assistance

I am most grateful to Mr. Eugene Nakamura. Mr. Larry Ogren gave
generously of his time and support throughout the project period.

22



Table 1.--Some Records and Reports of Neonate and Juvenile Sea Turtles
Associated with Sargassum or from Pelagic Habitats

. Observer,
Locality & Collector, or
Genus and Stage Circumstances Date Informant
Caretta Edge of Agulhas Current, Various G. Hughes (1978)
Hatchlings, Indian Ocean, regularly re-
marked in covered southward along
Tongal and coast of Natal and
around Cape Peninsula
Caretta Two found in stomach of 27 Aug. 1957 RR. Backus
HatchT ings white tip shark; 135 mi
E of Cumberland Is., GA
Caretta Nine found in sargassum 1965 Fisherman's
HatchTings raft “in Gulf Stream off report; Carr
Florida" (1967)
Caretta Netted in sargassum, 1968 Smith (1968)
Post-hatchling; 90 mi off Savannah
SCL 6.4 cm River Mouth, GA
Two, others together 28 mi 25 July 1967 Same
NE Daytona Beach, FL
Another 18 mi NE Cape 25 Oct. 1967 Same
Canaveral, FL
Caretta Dipnetted 15 mi SE Key 26 July 1957 Caldwell et al.
Neonate Largo, FL (1959)
Caretta Two seen in separate 16 May 1982 (Observer?)
"Apparently sargassum mats, Gulf of R/V Bellows
neonate" Mexico, 27°92'N; 85°22'W Cruise
(about 300 mi WSW of Tampa
Caretta From sargassum mat in 28 July 1981 M. Holman
SCL approx. “eddy at western end of . (W. Valentine
6-7 cm" Santa Rosa Island, FL, Gulf letter)
of Mexico"
Caretta Merritt Is. Refuge, Brevard 24 Oct. 1981 S. Vehrs
Neonate Co., FL, in sargassum,
after east wind
Caretta Northeast Florida, several Oct. 1968 Caldwell (1968)
Neonate washed ashore, encrusted

with sargassum hydrozoans

3



Figure 6. Pelagic stage loqgerheads in the series of 82 represented in
Fig. 5, from Princesse Alice Bank, Azores. (Photograph by
Helen Martins, Department of Oceanography and Fisheries,
University of the Azores.)

33



mental regimen of western Atlantic loggerhead hatchlings is--as Hughes
(1978) suggested for the Natal loggerheads of the colony he worked
with--a period of three years or longer, and that during this time
the Atlantic juveniles drift in the Gulf Stream system and feed on
pelagic forage along the frontal walls of eddies and gyres. Knowing
this indicates that the time has come for the old term “lost year"

to be replaced by the designation "pelagic stage," and for this, in
the case of Atlantic Caretta, at least, to include juveniles of
straight-line carapace Tengths of up to 30 cm and more.

THE PELAGIC STAGE AND PROBLEMS OF CONSERVATION AND MANAGEMENT

The new evidence of complexity in the lost-year ecology of sea
turtles has important implications for their conservation and
management, presenting helpful insights and revealing fundamental
problems for nursery and head starting projects. Also indicated is
a clear need for research in the neglected field of convergence ecology.

It is now obvious that when young cultured sea turtles are released
in so-called head-starting projects, the release sites ought to be
chosen with the greatest care. Shores located at a distance from any
major current or its eddy ought to be avoided, no matter how great
the convenience or public-relations value of other localities may be.
The adaptive utility of the neonatal swimming urge and open-sea guidance
sense of hatchlings is that it takes them out of shelf waters, where
predation is at maximum, and into an offshore convergence habitat.

The farther they swim seaward, the deeper the water becomes and the
less likely they are to be found by aggregated predators, aquatic or
aerial. Once away from longshore waters, however, when the pods have
scattered widely and predation has slackened, the hatchlings face the
problem of finding food. The adaptive response to this need is. to
continue travelling seaward until a rip is intercepted. The neonatal
swimming urge, the residual yolk supply that hatchlings have, and their
remarkable open-sea guidance sense (Frick 1976) are adaptations for
finding a driftline after leaving the shore. It thus stands to reason
that head starting and hatchling relocation should be undertaken only
where a front is likely to be accessable within their travel-range.

It is obviously necessary to avoid release localities where the
convergence, habitat may carry heavy loads of pollutants. There seems
at present to be no way in which the pelagic-stage young can be kept
out of polluted fronts at some stage of their long period of drifting
with currents, but it clearly makes no sense to release them where
longshore petroleum drift is known to occur. At the recent Workshop
on the Fate and Impact of Marine Debris in Honolulu, the impact of
plastic flotsam on marine turtles was exhaustively documented by Balazs
(1985), while Galt (1985) detailed the diversity, origin and unpre-
dictable shiftings of the convergences along which pollutants collect.
Galt's account of the changing positions of the fronts, and thus the
routes of spread of pollutants does not simplify the problem of selecting
appropriate release sites. In a given locality, however, it is usually
possible to know what major current regimen is likely to prevail offshore

19



Frick, J.
1976. Orientation and behavior of hatchling green turtles (Chelonia
mydas) in the sea. Animal Behaviour 24:849-857. 2.

Galt, J.A.
1985. Oceanographic factors affecting the predictability of
drifting objects at sea. NOAA Tech. Memo. NMFS, NOAA
Tech. Memo. NMFS-SEFC-54:497-518.

Hardy, A.
1958. The open sea: its natural history. Part 2: Fish and
Fisheries. Houghton Mifflin Company, Boston. 322 p.

Hillestad, H.O., J.I. Richardson and G. K. Williamson.
1977. Incidental capture of sea turtles by shrimp trawlermen
in Georgia. Report to N.M.F.S. by Southeastern Wildlife
Services Inc. Athens, Georgia. 104 p.

Hughes, D.A. and J.D. Richard.
1974. The nesting of the Pacific Ridley turtle Lepidochelys

otivacea on Playa Nancite, Costa Rica. Mar. Biol. (Berl.)
24(2):97-107.

Hughes, G.
1978. Marine turtles, In A.E.F. Hedorn (editor). Ecology of
the Agulhas Current. Trans. Roy. Soc. S. Afr. 43:151-190.

Kerr, R.A.
1985. Small eddies are mixing the oceans. Science 230:793.

Lamb, K.D.A.
1959-1963. Sea birds at the confluence of the Gulf Stream and
Labrador Current east of New York. Sea Swallow, 12-16, 65.

LaViolette, P.
1986. U.S. Navy western Mediterranean circulation experiment.
Ocean Science, Oct. 7, 1986, p. 3.

Limpus, C.
1985. A study of the loggerhead sea turtle, Caretta caretta,
in eastern Australia. Doctoral Dissertation, University
of Queensland. 481 p.

Maigret, J.
1983. Repartition des tortues de mer sur les cotes ouest
africaines. Bull. Soc. Herp. France 28:22-34.

McDowell, S.E.

1986. On the origin of eddies discovered during the POLYMODE
Local Dyanamics Experiment. J. Phys. Oceanogr. 16:632-652.

25



as an answer to the "lost year" puzzle. What seemed a serious weakness
in that theory was the tendency of the rafts to break up in heavy seas.
The more generalized, mobile inhabitants could simply cruise around

till they came upon another mat; but how about such wholly committed
species as the sargassum fish? Its specialized adaptations would seem
to make life impossible anywhere else. How did any of the adaptively
committed sargassum species ever get back into a reassembled weed habitat
after a storm had churned it up?

To get an answer, three ideas had to be put together, as follows:
(1) the rafts are assembled by advection, caused by sinking, at fronts;
(2) after heavy weather the same force both reassembles the mats and
gathers and reinstalls the dislodged occupants when the sea calms down
again, and (3) fronts, and thus, advection, are not confined to edges
of major currents; they occur as semi-stable or recurrent features
throughout the epipelagic; they are of all kinds and sizes (Uda 1938;
Galt 1985); and they are able to assemble all kinds and sizes of flotsam,
from salps and copepods to drifting trees or ships (Beebe 1926).

For quite a while I remained ignorant of these ideas and as a
result found it impossible to understand how sargassum could ever have
acquired a fauna of evolved, obligate occupants, unable to live else-
where, and incapable of the active, oriented travel necessary for
searching out another mat or driftline.

Then one day I looked out of a little airplane and saw the whole
surface of the sea banded with narrow weedlines, spaced across the
water with unaccountable regularity. When I got home and talked with
an oceanographic colleague I learned that the multiple driftlines were
made by advection between opposing horizontal vortices generated by
steady wind, that they are called Langmuir bands, and that the phenomenon
is common. For me, this eased the way toward understanding how epi-
pelagic life can be lived by an organism unable to photosynthesize,
or to sweep in plankton, or to cruise away to the Gulf of Guinea when
its rip disintegrates.

If you tell a physical oceanographer about that problem, and can
persuade him or her to speak English and to tell you why, and how
regularly, convergent downwelling occurs in the surface water, and
how this assembles flotsam in lanes and bands, you will learn that
the process is common wherever there is differential horizontal movement
in the upper water of the sea.

In a river you see this in miniature wherever the current washes
around a snag or over a submerged boulder and makes a swirl on the
downstream side. A gang of gyrinid beetles will probably be there,
picking up stuff that collects along the edges of the swirl; and a
baited hook cast into the curve of the little rip is likely to be taken
by a fish. At the downstream end of a bar where the separated current
comes together, or in the roil of water over a sunken boulder, it is
the same. Then later on, when the river meets the sea the horizontal
meeting generates vertical response, and because the water can't rise
against gravity the vertical component is only downward; and since

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34



cases, however, loggerheads in the down-current stations have not been
recorded in benthic habitats but in the open sea, where they are
obviously being passively transported by the current.

That they are feeding at the surface over deep water is clearly
indicated by the flotsam and pelagic food consistently found in the
stomachs. In the stomachs of three loggerheads from off Madeira,
Brongersma (1968) found salps, the shell of a pteropod, probable medusa
nematocysts, a piece of plastic, and many goose barnacles with wood
attached--evidently having been bitten off floating logs. Brongersma
(1972) listed the following items of pelagic origin from stomachs
examined by Pouchet and de Guerne (1940) taken during a cruise by Albert
I of Monaco: many pteropods, Hyalaea tridentata; pieces of medusae;
amphipods; the pelagic crab Nautilograpsus minutus; bunches of the
goose barnacle Lepas anatifera; a cinder, straw, and wood chips. More
recently van Nierop and den Aartog (1984) examined the gut contents
.of five little loggerheads, also from islands of the Macronesian area,
and found--besides plastic debris--pelagic tunicates, pelagic snails,
gooseneck barnacles--which regularly are found attached to solid flotsam
--and nematocysts of a number of different species of coelenterates.

Results of recent oceanographic research make it somewhat easier
to understand how the long period of time separating the Azores logger-
heads from the age class they will join when they move into benthic
West Atlantic habitats is passed. The report of Scully-Power (1986)
on observations made during space shuttle Challenger Mission 41-G shows
that the oceans of the world teem with fronts of all dimensions and
configurations. Papers in a recent issue of the Journal of Physical
Oceanography (Vol. 16, No. 3, March, 1986) reveal that in the North
Atlantic small eddies, usually less than 50 km across, are far more
numerous and long-lived than has been believed. In the words of McDowell
(1986) "reanalysis has revealed a number of features . . . so anomalous
that a sample or two from a Nansen bottle cast would have been considered
suspect and most likely discarded, because it was presumed that water
properties were smoothly varying on horizontal scales of tens to hundreds
of kilometers." Meaning, as nearly as I can make out, that the numerous
new eddies have been discovered because hydrographic procedures are
more discriminating today than they used to be. In 1978 an intensive
survey was carried out as a part of the POLYMODE Local Dynamics Experi-
ment in the Sargasso Sea southwest of Bermuda (near 31°N, 70°W). Data
from this work clearly have important bearing on the ecology and passive
transport of planktonic animals, including juvenile turtles, in the
North Atlantic. The shallow eddies detected by the survey had different
and in some cases distant origins (Kerr 1985, McDowell 1986). Two
were from the eastern Atlantic, three from the Gulf Stream, two from
the central Sargasso Sea, and two from places not determinable from
the data. A number of deeper (mid- and lower thermocline) eddies had
also originated at long distances from the experimental site. McDowell
concluded from these experiments that "the distinct origins of these
features and their inferred trajectories contribute to our understanding
of the general circulation within the North Atlantic and suggest that
discrete eddies may represent an important mechanism for the large-scale
exchange of properties in the ocean." I would go farther and suggest
that the multiplicity of such features now coming to light helps bring

16



Table 1.--Continued

Observer,
Locality & Collector, or
Genus and Stage Circumstances Date Informant
Chetonia Edge of Gulf Stream off 4 March 1983 Woods Hole
Advanced pelagic Bahama Bank, north of Cruise, R/V Cape
Matanilla Shoal; on Florida, L.
sargassum drift 4' thick Bibko, Informant
Chetonia Banco Colon, 26 mi off Sept. 1977 W. A. Rankin,
Neona te Colon, Panama dolphin
fishermen
Chetonia One taken from stomach Fish caught by
Neona te of dolphin caught beside L. Barker; data
sargassum raft 19 km E- recorded by R.
of St. Lucie Inlet, - Witham
Stuart, FL
Chetonia Vella Gulf; on log in Vaughan (1981)
Two “smal1" driftlines
post-hatchlings
Eretmochelys Bermuda, various local- 1982, 1985, J. Burnett-
Early to Tate ities. Drifting in weeds, and 11 Sept. Herkes
post-hatchlings stranded in beach and ~* 1983 (the
and older washed in over 20' wall hatchling)
5.3 to 20.7 cm by storm waves
Eretmochelys Mustang Island, TX 1983-1984 A. Amos
Advanced to late
stages and just
beyond; shell
lengths: less
than 10 cm, 3;
10-20 cm, 2;
20-30 cm, 7
Eretmochetys Broward Co., FL stranded J. Fletemeyer
Advanced pelagic with tar smeared sargassum
Eretmochetys Hutchison Island, FL R. Witham
Transttiona stranded with tar smeared
stage 20.2 cm sargassum
Eretmochetys Brevard Co., FL; dead, had 6 Feb. 1981 Jd. Fletemeyer
Advanced ingested tar

pelagic; 14.0 cm



Figure 4. Advanced loggerhead post-hatchling, thrown ashore in sargassum
by heavy seas, Flagler County, Florida, and rehabilitated by
Marineland Research Lab.

31



Figure 1. Pelagic stage juvenile loggerhead from edge of Sargasso Sea.
(R/V Geronimo photo.)

28



Table 1.--Continued

Observer,

Locality & Collector, or
Genus and Stage Circumstances Date Informant
Caretta St. Johns Co., FL, washed Late Oct., Fla. State
Advanced hatch- up in sargassum 1968 Museum 27019
ling; SCL 5.2 cm
Caretta Bermuda, outer reef, 17 May 1985 Jd. N. Burnett-
StL 1274 cm in sargassum Herkes
Caretta Gulf of Mexico 200-300 31 Apr. 1982 R. Trok;

Carapace 3.5 cm
wide

Caretta

‘wo, advanced
pelagic stage,
one measured,
carapace 13.5 cm

Caretta
Neonate

Caretta
Neonate and
weeks-old
hatchlings

Caretta
Neona te

Caretta
WNeonate and
slightly ad-
vanced

mi S of Galveston, TX,
26°30'N; 90°50'W

NW sargassum sea, 300 mi
SSE Nantucket, 37°2'N;
66°23'W. Two 5 mi apart

South Melbourne Beach,
Brevard Co., FL.
sargassum wrack after
Huricane Isidore. Four
turtles found in weed in
100 yd walk, "Hundreds more
surely killed."

Flagler Co., FL. Many
washed up with weed-
wrack during Hurricane
Isidore; some dead, some
brought to Marineland

About 30 mi SE Port
Canaveral, many turtles

in numerous short sargassum
lines

24 mi SE Port Canaveral.
Saw “about 20" in one
raft about 75' x 100',
moving south. Much other
sargassum; many jellyfish

Continuous

28 June 1982

30 Sept. 1984

28-30 Sept.
1984

1982

5 Sept. 1984

R/V, MAR Inc.

R/V Geronimo,
St. Georges
School

D. Hopkins,
S. Melbourne
Beach

Rehabilitated by
J. Lowenstein
Marineland
Research Lab.

T. Ferrence gave
A. Carr photo,
taken from boat,
of hatchling
sleeping in
sargassum

J. Dorman



Table 1.--Continued

Observer,

Locality & Collector, or
Genus and Stage Circumstances Date Informant
Caretta Beach at Matanzas Inlet, 7 Sept. 1985 L. Alexander
Post-hatchling St. Johns Co., FL; in
5.7 cm SCL sargassum after strong

northeast. wind

Caretta New Smyrna Beach, FL, 3 Nov. 1983 D. Cring

Advanced post-
hatchling; 6 cm
SCL

Caretta
Advanced post-
hatchling; SCL
approx. 6 cm

Caretta
HatchTings

Caretta
Advanced post-
hatchling

Caretta
~> cm

Caretta
Neona te

Caretta
Advanced post-
hatchling (21 g)

Caretta
hree post-
hatchlings

washed up in NE storm

_Gulf of Mexico, 26°45'N,

84°08'W, just east of
Loop Current, sargassum .
and many Physatia

Fort Pierce, FL. Saw
20-30 in heavy sargassum
1-3 mi off Whistling
Buoy. Picked up one in
sargassum on shore

Gulf Stream, west border
off Miami

Canaveral National
Seashore.. Washed up
in sargassum

Western front of Gulf
Stream, 93 km E of St.
Augustine, FL. At least
20 seen in line of
sargassum patches

John V. Loyd State Park,
Broward Co., FL

Gulf of Mexico, approx.
120 mi WSW of Tampa.
Just west of shelf in
Loop water

4

17 March 1984

10 Oct. 1980

Spring, 1983

10 Oct. 1982

22 Aug. 1981

5 Jan. 1982

25 May 1982

R/V Delaware,
Capt. D. Adams

J. W. Jones

Capt. A. Dillard
of Sea Hawk;
twice saw young
turtles. Said
grouper main
predator there.

D. Whitman

P. McGillivary,
Cruise of R/V
Cape FL for
Skidaway Oceano-
graphic Inst.

J. Fletemeyer

S. Collard, R/V
Bellows cruise



new understanding of the ecology of epipelagic organisms and of the
food resources and transport facilities available to them.

The eddies are not only rings derived from Gulf Stream meanders.
They are itinerant vortices of varied origins and are not just surficial
features but are cylinders, some of which extend down to or even below
the thermocline. The rotation of those that reach the surface must
generate downwelling, and this is bound to mobilize both flotsam and
depth-keeping macroplankton. Thus their contribution goes far beyond
the mixing of water properties. These small travelling eddies become
both habitat and transport medium for any pelagic plankton grazer,
planktonic or cursorial.

It must be somehow significant that the juvenile sea turtles that
have been observed at sea have often been associated in groups. Obser-
vations of turtles are most often reported from just west of the Azores
(Fig. 8), and from there southwestward to Gibraltar and Madeira
(Brongersma 1972). They are often described by voyagers in terms
of numbers seen in given periods of travel along a course. Thus, there
is a question whether the groups are social aggregations or migrants
aligned passively along a convergence. Linear grouping of loggerheads
observed in the North Atlantic Drift (Hardy 1958) and by Richard Backus
(in litt.) suggest the latter. However, other reports of "small, brown
turtTes” seen in "patches" or schoots, suggest overt, social aggregation.

A recent example of such a sighting was recorded by Maigret (1983)
who reported that in May, 1982 thousands of turtles, 30 cm or so in
shell length, had been observed by a lobster boat at 33°N, 74°W --
coordinates corresponding to a point in the western Atlantic between
Bermuda and North Carolina. Seventy-five of the turtles were captured,
and the species was later identified as Lepidochelys kempi. When the
basis for this astounding record was investigated by Peter Pritchard
(in press) it was found that the western Atlantic position given was
a typographic error, longitude 74°W having been a misprint for longitude
14°W. The locality was thus not off America but in the eastern Atlantic,
near the island of Madeira. In continuing his investigation of this
arresting record Dr. Pritchard asked and received permission to look
at photographs of one of the specimens involved and found it to be
a young loggerhead.

This, then, would appear to represent the largest travel aggregation
of Caretta ever reported anywhere. Even more recently, a less well-
documented case has been reported to me by Sam Sadove of OKEANOS (Ocean
Research Foundation), in which a big school of young "brown sea turtles
the size of basketballs" was seen by people on a yacht cruising off
Madeira. Still another apparently reliable recent report tells of
the sighting of "a whole bunch of little turtles" by the crew of a
sailboat just south of Bermuda (Allan Meyer pers. comm.).

How frequent such seeming aggregations are, and what the adaptive
utility of the association may be, deserves more attention. The only
species in which migratory aggregation is known to be a regularly
occurring trait is the olive ridley Lepidochelys olivacea. It was
the sighting of a flotilla of massed olive ridleys trom the air in

7



Table 1.--Continued

Observer,
Locality & Collector, or

Genus and Stage Circumstances Date Informant
Probably Volusia Co., FL 24 May 1986 Fishermen in Daytona
Caretta off Ponce de Leon Inlet Striking Fish
Hand-size, in Tournament
sargassum patch fide J. B. Miller
about 125 ft
long over 1900
ft depth
Probably Volusia Co., FL 24 May 1986 Fishermen in Daytona
Caretta off Ponce de Leon Inlet Striking Fish
Hand-size in Tournament
sargassum over fide J. B. Miller
1500 ft depth
Probably Volusia Co., FL 25 May 1986 Fishermen in Daytona
Caretta ESE of Ponce de Leon Striking Fish
wo “small brown Inlet Tournament
sea turtles" in fide J. B. Miller
weed line just
south of "The
Steeples" over
1000 ft depth
Probably Off St. Augustine, FL 25 May 1986 Fishermen in Daytona
Caretta over 1000 ft of water Striking Fish
One saucer-sized Tournament
brown turtle in fide J. B. Miller
driftline
Chetonia Many netted by G. Furuya Various Caldwell (1969)
HatchTings 50 mi SE Manzanillo, dates

Michoacan, Pacific coast

of Mexico. "There regularly.”
Chetonia At sea near Revillagigedo June 1963 Caldwell (1969)
HatchTings Islands
Chelonia 8 mi east of Marquesas Aug. 1983 T. and N. Carr
wo, 10-15 cm Keys, FL; moving among

sargassum rafts
Chetonia Mustang Island, TX; Various dates A. Amos
Five, 10-20 cm stranded 1984
Chetonia 22 mi off Colon, Panama, Sept. 1979 R/V Alpha Helix
Neonate and in driftline of sargassum Carr and Meylan

early advanced

(1980)



LITERATURE CITED

Ashmole, N.P.
1971. Sea bird ecology and the marine environment. In D.S.
Farner and J.R. King (editors). Avian Biology.
Pp. 223-286. Vol. 1. Academic Press, New York.

Ashmole, N.P. and M.J. Ashmole.
1967. Comparative feeding ecology of sea birds of a tropical
island. Peabody Museum of Natural History, Yale University
Bulletin 24:1-131.

Balazs, G.
1982. Growth rates of immature green turtles in the Hawaiian
Archipelago. Pp. 117-125. In K.A. Bjorndal (editor).
Biology and Conservation of Sea Turtles. Smithsonian
Institute Press, Washington, D.C.

Balazs, G.
1985. Impact of ocean debris on marine turtles: entanglement
and ingestion. In R.S. Shomura and H.0. Yoshida (editors).
Proceedings of the Workshop on the Fate and Impact of
Marine Debris 27-29 November 1984, Honolulu, Hawaii,
Pp. 387-429. U.S. Dept. Commerce, NOAA Tech Memo NMFS,
NOAA-TM-NMFS-SWFS-54.

Beebe, W.

1926. The Arcturus Adventure. G. P. Putnam's Sons, New York.
439 p.

Brongersma, L.D.
1968. Notes upon same turtles from the Canary Islands and from
Madeira. Proc. Kon. Ned. Acad. Wet., Ser. C71 (2):128-136.

Brongersma, L.D.
1972. European Atlantic turtles. Zool. Verhand., Leiden. 121:1-318.

Brongersma, L.D.
1982. Marine turtles in the eastern Atlantic Ocean. Pp. 407-416.
In K.A. Bjorndal (editor). Biology and Conservation of Sea
Turtles. Smithsonian Institution Press, Washington, D.C.

Bullis, H.R. and R. Cummins.
1961. An interim report on the Cape Canaveral calico scallop
bed. Comm. Fish. Rev. 23:1-8.

Caldwell, D.K.
1968. Baby loggerhead turtles associated with sargassum weed.
Quart. Fla. Acad. Sci. 31:271-272.

Caldwell, D.K.
1969. Hatchling green sea turtles, Chelonia mydas, at sea in
northeastern Pacific Ocean. Bul. So. Calif. Acad. Sci.
68:113-114.
23



NOAA Technical Memorandum NMFS-SEFC-190

Technical Memorandums are used for documentation
and timely communication of preliminary results,
interim reports, or spectal-purpose information,
and have not received complete formal review,
editorial control, or detailed editing.

wr

New Perspectives on the Pelagic Stage of Sea

2

S

%
z

Turtle Development

> <
*Rrment of &

Archie Carr

Caribbean Conservation Corporation

July 1986

U.S. DEPARTMENT OF COMMERCE

Malcolm Baldrige, Secretary
NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

Anthony J. Calio, Administrator
NATIONAL MARINE FISHERIES SERVICE
William G. Gordon, Assistant Administrator for

Fisheries



THE ROLE OF FRONTS

An original difficulty in accepting the idea of a pelagic develop-
mental period for sea turtles was to explain how food could be found
in reliable supply in the open ocean (Carr 1967). Once a little air-
breathing carnivore had moved out of the productive waters of the conti-
nental shelf how could it possibly support itself? A partial answer
emerged when post-hatchlings were found in rafts of sargassum. The
mats have a diverse biota of adapted inquilines and could provide food
as well as shelter, so this seemed an attractive solution to the puzzle
of the disappearing turtles. Although the sargassum refuge is now
proven reality, it cannot account for the missing interlude in the
ecology of all populations of marine turtles because many of them breed
where no sargassum is present. So, as important as sargassum is as
refuge and feeding habitat, it is clearly not indispensible.

The uncertainty that this introduced was removed when I belatedly
came-to appreciate the prevalence and diversity of convergences where
downwelling- gathers and aligns buoyant material, including the dispersed
food resources of the surface waters. Galt (1985) enumerated the many
ways in which fronts of all dimensions and configurations may originate.
They range in magnitude from driftlines along the walls of major border
currents down to local rips over reefs and sea mounts, off capes and
river mouths, and at the downcurrent ends of bars. The sinking and
advection that they generate also occurs at the borders of the warm-
and cold-core Gulf Stream rings, and it builds the fields of raggedly
parallel multiple bands generated by wind-action in Langmuir circu-
lation. In all these and many other kinds and sizes of fronts, the
mobilization of flotsam by the vertical component generated by the
horizontal collision of water bodies gathers in both the hatchlings
and the resources that they require. If sargassum occurs in the region
the same process builds the mats into rafts, rebuilds them when storms
break them up, and strings them out in the driftlines that ease the
hatchlings’ problem of locating their pelagic frontal habitat. If
no brown algae are present, offshore fronts nevertheless sustain the
hatchlings by concentrating food resources, and by aligning debris
that provides concealment.

Thus, it now seems clear that an essential factor in the survival
of young sea turtles--and of other elements of the epipelagic, open-ocean
fauna as well--is the accessibility of a front, where inanimate debris
and any floating animal or plant--or any planktonic organism able to
hold to a preferred depth either by its locomotion or by buoyancy control-
--will be gathered in. The marked increase. in biological activity
along rips, or Siome, as the Japanese call them, is widely recognized
by sea-faring people; and the dynamics and surface manifestations of
advection.:along the line between two water bodies in opposing motion
has long been a familiar concept to oceanographers (Uda, 1938). The
idea is a lot less familiar to other people, however; and this has
held back understanding of the ecological organization of the marine
environment.

Sea turtles share their ecologic dependence on fronts not just
with holopelagic species, but also with littoral fishes and benthic

10



Table 1.--Continued

Observer,
Locality & Collector, or
Genus and Stage Circumstances Date Informant
Eretmochelys Jupiter Is., Palm Beach 16 Jan. 1981 Fla. State
23.1 cm SCL Co., FL Museum 50028.
Collector
Unknown
Eretmochelys Jensen Beach, Martin Co., 16 Feb. 1981 J. Dietjen, Fla.
4.0 cm SCL FL State Museum
50027
Eretmochelys Gulf of Siam, Thailand, 9 Aug. 1980 Dipnetted,
Advanced pelagic 07°22'N; 100°43.5'E Scripps NAGA
15.1 cm Expedition,
: T. Matsui,
collector
Eretmochelys Various localities; both Various dates Vaughan (1981)
HatchTing and coasts of Choiseul, in
slightly larger" sargassum driftlines,
singly and in groups
Eretmochelys Mustang I. (NE end of Sept. 15 - A. Amos
20 hatchTings Padre I.) Texas Oct 5, 1986 Strong SE (offshore)
and post hatch- (ten in one wind for several
lings SCL 5-8 cm day) days, with surf up

onto berm and
storm pools formed.

Lepidochelys 30 mi E. of St. Augustine, 1 March 1961 Collector for Fla.
20.9 cm FL, with another same size. State Museum
Taken with cast net. This 57983

ridley is apparently the
smallest ever recorded from
FL

Not Identified W. Pacific; around Various Miller (1978)
Sima urtTes" barnacle-covered drift
logs in open ocean

Not Identified 19 mi SE St. Lucie Inlet, 9 Sept. 1972 Observed by

Stuart, FL, two hatchlings L. Barkes
on floating board near (reported in
sargassum raft Witham 1974)



Figure 3. Pelagic stage green turtle, possibly the same as in Fig. 2
moving across sargassum raft off tip of Little Bahama Bank.
(Lisa Bibko photo, R/V Cape Florida cruise.)

30



Figure 2. Pelagic stage green turtle in exceptionally dense sargassum
driftline off the tip of Little Bahama Bank. (Lisa Bibko photo,
R/V Cape Florida cruise. )

29



Table 1.--Continued

Observer,
Locality & Collector, or
Genus and Stage Circumstances Date Informant
Caretta Brevard Co., FL, Cocoa 5 Sept. 1979 One hundred col-
Neonate, in Beach, between lst St. and lected dead or
sargassum after Patrick Air Force Base moribund by B.
storm Schroeder; sent
by L. Ehrhart
Caretta Gulf of Mexico, off mouth 22 Feb. 1965 J. Miller
Several wks old; of Homossassa River
SCL 7.9 cm
Caretta Eight taken from stomach 9 Sept. 1972 Fish caught by
Neona te of dolphin caught beside L. Barker; data
sargassum raft, off St. . recorded by R.
Lucie Inlet, 19 km E of Witham (1974)
Stuart, FL
Caretta Bermuda, various locali- Various J. Burnett-
Advanced ties; stranded or drifting 1980-1985 Herkes
pelagic with sargassum
post-hatchlings
Caretta Mustang Island, TX; 1984 A. Amos
Advanced pelagic stranded
stage, 18 cm
Caretta 26 mi ENE of Sebastian 8 Aug. 1966 E. M. Coon
One neonate, Inlet, FL
another weeks
old
Caretta Mustang I. (NE end of Late Sept., A. Amos
7 hatchlings Padre I.) Texas 1986 Strong offshore
(NE) wind for
several days surf
up to bern, with
storm pools.
"Probably Edge of Little Bahama Feb. - Apr. Capt. G.
Caretta"; Bank N of Matanilla; various yrs Buffkin, sword-
Rand-stze Light at edge of E-W prior to 1981 fish longliner

pelagic stage

current. Advanced pelagic
turtles "usually seen in
weed line there in February
and March" while working
long-line for swordfish
along weed lines

(Same report

from numerous
swordfishermen
in Fort Pierce
and elsewhere
along E coast)



at a given time, and to avoid releases at beaches where the probability
of encountering heavy pollution is high.

In Florida, where the heaviest loggerhead nesting in the Atlantic
system occurs, the adjacent sections of the Gulf Stream at times carry
oil from both European sources and the heavily burdened Gulf of Mexico.
Petroleum in one form or another has been found there in the guts of
numerous hatchlings and juvenile sea turtles--usually loggerheads,
but also hawksbills and green turtles--that have washed ashore in
sargassum. On the Caribbean coast of Costa Rica, advanced juveniles
that had ingested oi] or tar have washed in on Tortuguero beach, evi-
dently after one or more circuits in the West Caribbean Gyre (Carr
and Meylan 1980, and verbal reports to Carr). In the guts of young
loggerheads of the pelagic stage from around San Miguel (Azores),
Madeira, and the Selvagens Islands, Brongersma (1968) and van Nierop
and den Hartog (1984) found polyethylene sheet plastic, bits of solid
plastic, pieces of paper, and nylon line; and all the stomachs contained
semi-solid clots of oil. In 1983, after the 1982 year-class of head-
start Kemp's ridleys were released off Mustang and Padre Islands, Texas,
91 of these were later found stranded. All had ingested oi] or tar
pellets, which had been picked up when the turtles went into offshore
sargassum mats. The beaches of Bermuda and the sargassum rafts that
drift by them are frequently smeared with tar. Meylan (1983b) called
attention to the threat to the ecology of the southwest Caribbean gyre
and South Equatorial Current, which receive the entire output of hatch-
lings from the Tortuguero nesting ground of Chelonia, from the pipeline
and oi] port being constructed at Chiriqui Grande on the shore of
Chiriqui Lagoon.

For the present the problem of the coming together of hatchlings
and pollutants in fronts is without a solution. One important tactical
rule-of-thumb, however, is to refrain from releasing hatchlings or
head-start turtles on any shore off which no convergence is available,
where an onshore drift prevails in the season of release, or where
a longshore driftline is likely to be loaded with pollution.

EPILOGUE

Results of the present work reveal an urgent need for further
study of sea turtle life cycles, with special attention to their
developmental ecology. The growing evidence for a more protracted
pelagic stage, during which the juvenile turtles are passive migrants
in fronts that are increasingly invaded by debris and toxic wastes,
emphasizes the need for a better understanding, by marine biologists,
of the organization of the driftline habitat and the behavioral ecology
of its occupants. In the case of sea turtles our faulty understanding
of the sites and schedules of transition from the pelagic stage to
life on the continental shelf is a further fundamental obstacle to
conservation and management.

Why the concentrated biological activity at fronts has had so
little impact on the thinking of marine ecologists is an abiding puzzle.
I became aware of it only when I began to consider the sargassum refuge

20



Mendonca, M.T.
1981. Comparative growth rates of wild, immature Chetonia mydas
and Caretta caretta in Florida. Jour. Herp. 15:447-451.

Mendonca, M.T. and L.M. Ehrhart
1982. Activity, population size and structure of immature Chelonia

mydas and Caretta caretta in Mosquito Lagoon, Florida.
Copeta 1:161-167-

Meylan, A.B.
1983a. Marine turtles of the Leeward Islands, Lesser Antilles.
Atoll Res. Bul. No. 278. 24 p.

Meylan, A.B.
1983b. Oi] terminal puts Caribbean Hawksbill] at risk. World Wildlife
Fund Monthly Report. October 1983, Project 1499. 3 p.

Miller, W.C..

1978. Best chance for U.S. tuna fleet may be found in Western
Pacific. National Fishermen 58:36-37. :

Murphy, G.I. and R.S. Shomura.
1972. Pre-exploitation abundance of tunas in the equatorial
central Pacific. Fishery Bull. 70:875-910.

van Nierop, M.M. and J.C. den Hartog.

1984. A study on the gut contents of five juvenile loggerhead
turtles, Caretta caretta (Linnaeus) (Reptilia, Cheloniidae),
from the south-eastern part of the North Atlantic Ocean,
with emphasis on coelenterate identification. Zoologische
Mededelingen 1:35-54.

Ogren, L. and C. McVea.

1982. Apparent hibernation by sea turtles in North American
waters. Pp. 127-132. In K.A. Bjorndal (editor). Biology
and Conservation of Sea Turtles. Smithsonian Institution
Press, Washington, D.C.

Olson, D. and R. Backus.
1985. The concentrating of organisms at fronts: a cold-water
fish and a warm-core Gulf Stream ring. Journal Marine
Research 43:113-137.

Pouchet, G. and J. de Guerne.
1940. Sur l'alimentacion des Tortues marines. Res. Camp. Sci.
Albert Ier Monaco 103:241-242.

Pritchard, P.C.H.
[In press] Evolutionary relationships, osteology, morphology,
and zoogeography of Kemp's ridley sea turtle. Proceedings
Kemp's ridley symposium, Galveston, Texas.

26



several views, and her pictures (Figs. 2 and 3) clearly show it to
be a green turtle, probably five to eight months old.

The site of the latter observation is near a place at which well-
grown post-hatchlings have consistently been reported by swordfishermen.
Before the recent failure of the swordfish fishery, long-liners in
Fort Pierce and Fort Lauderdale repeatedly told us that in the area
northwest of Little Bahama Bank, "where the current flows east and
west instead of north and south," massive driftlines of sargassum form,
especially in February and March. When this occurs, the fishermen
say, little turtles "the size of your hand" can often be seen on and
among the mats in the weedline along which the swordfish long-lines
are set. On three occasions we visited this locality, and each time
we found the driftline broken up by wave action. Nevertheless, the
many independent reports from Gulf Stream fishermen based between Palm
Beach and Port Canaveral indicate that an important station in the
passive migration of Chelonia--and perhaps of Caretta also--is located
just north of MatanilTa Reef; and that whenever massive driftlines
form in the area, months-old young turtles are likely to be found in
them.

Not many such stations, where young turtles can predictably be
found at great distances from their places of origin and long after
hatching, are known; and it is not logistically feasible to make special
cruises looking for them. Nevertheless, the reports that have accum-
ulated clearly indicate that hatchlings not only go into sargassum
rafts but remain in them for long periods of time. This is circum-
stantially corroborated by the repeated instances in which advanced
post-hatchlings have washed up in storm-driven sargassum wrack on the
same nesting beach on which they might have hatched several weeks or
even months before (Fig. 4). In these cases the turtles must have
passed the time since they hatched drifting in local eddies of the
offshore currents (Carr and Meylan 1980, Carr 1986). Like the larvae
of benthic invertebrates and some inshore fishes, the hatchlings are
planktonic, with no control over their geographic displacement. After
their brief initial swim away from land, off most nesting shores they
are picked up and carried away by a current. If this is a major border
current it may take them.straightaway on a global circuit. When the
current adjacent to the nesting beach is a local gyre, however, the
migration of the hatchlings may, for a time, be confined to the vicinity
of the hatching site (Carr and Meylan 1980, Carr 1986). Such short-
-circuiting has been suggested for the larvae of the calico scallop
of Cape Canaveral, Florida (Bullis and Cummins 1961), which might simply
circulate indefinitely in the eddy between Cape Canaveral and Cape
Florida. This must be of frequent occurrence in the development of
other sessile benthic organisms. Ample evidence that some post-hatchling
sea turtles spend time in home- shore eddies is the repeated stranding
of post-hatchlings a few weeks old on rookery beaches in Florida and
Costa Rica, long after hatching. Such local eddies are usually shifting
or ephemeral, however, and it is obviously unlikely that hatchlings
ever pass their entire developmental periods in them. Most are evidently
taken away on high-ocean journeys, and the difficulty of tracing these
routes complicates the study of post-hatchling ecology.

2



wrote me that little loggerheads were being caught regularly by tuna
fishermen on Princesse Alice Bank, an important fishing ground near
Faial. She said that the fishermen were in the habit of making soup

of the turtles, and suggested that we organize a tagging project, buying
the turtles, tagging them and letting them go.

We accordingly embarked on a collaborative tagging program, and
even before any tag-return data have come in, results of the project
have been very interesting. When shell-length data for the 82 turtles
tagged during the first two seasons (1984 and 1985) were received they
represented a size class never seen in Eastern Atlantic waters (Table
2) and the measurements fit neatly into the space in our western Atlantic
histogram (Fig. 5). Inasmuch as Princesse Alice Bank is located where
the main flow of the Gulf Stream system begins its southward swing,
the Faial loggerheads are well placed for eventual transportation back
to American waters. Moreover, they are in sound physical condition,
still pelagic, and feeding on pelagic forage (Fig. 6).

TABLE 2.--Straight carapace length (cm) in juvenile pelagic loggerheads
taken by tuna fishermen on and near Princesse Alice Bank, The
Azores, during summer months of 1984 and 1985.

1984 1985 1984 + 1985
Number : 40 Number: 42 Number: 82
Average: 20.6 Average: 25.2 Average: 22.9
Median: 19.4 Median: 24.5 Median: 21.7
Range: 15.2-38.0 Range: 11.0-38.0 Range: 11.0-38.0

Assessment of the possibility that the developmental migrations
of American loggerheads regularly involve transatlantic travel in the
Gulf Stream system has- until now been hindered by two factors. One
has been our failure to appreciate the significance of the absence
of the 20-40 cm age group in U.S. waters. The other has been the preva-
lent tendency to dismiss as non-viable derelicts the members of that
size class when they turn up in the eastern Atlantic--especially in
the United Kingdom, where the usual fate of flotsam is to drift on
toward the Arctic into water of lethal temperature. Much less attention
has been given the more numerous turtles that reach the eastern Atlantic
in the southerly branch of the Gulf Stream system, which is both warm
and likely to transport flotsam eventually back to America.

It seems reasonable to discard the occasionally mentioned possi-
bility that the Mediterranean might be the source of the juvenile sea
turtles of eastern Atlantic waters. Although Caretta nests in several
parts of the eastern Mediterranean, the colonies there are not large,
and the possibility that the Azores juveniles might be derived from
them would seem to be precluded by a strong current, around 200 meters

13



On Princesse Alice Bank they are obviously at a station where
currents can take them home, but a problem with the timing of the return
arises. As Figure 8 shows, by any bifurcation of the direct, main-axis
Gulf Stream route they would get back too soon, arriving in Florida
long before they had reached shell-lengths of even the smallest of
the Canaveral Channel and Indian River population or any other subadult
colony of American Caretta. By rough calculation, if they drifted
in the main Gulf Stream system--the Canary Current, South Equatorial
Current and Florida Current--the trip from Princesse Alice Bank to
Canaveral would require only around a year or less--whether the final
stage of the trip went through the Gulf of Mexico, or went directly
to Florida through the Antilles. This is obviously not long enough
to allow the growth necessary to fill out the graph in Figure 5.

The time required for Caretta to reach sexual maturity has been
calculated by several different methods and has ranged from 10 to 50
years. Limpus (1985), who has measurements from a broad range of develop-
mental stages of Queensland loggerheads, calculated the mean time
required to grow from 75 cm curved carapace length to breeding maturity
as 27 years, and the overall maturation time to be about 50 years.

With measurements from the loggerhead colony of the Indian River lagoons,
Mendonca (1981) derived a maturation age of 10-15 years. Bjorndal

and Bolten (in prep) found that juvenile loggerheads on their natural
foraging grounds in the southern Bahamas take three to four years to
grow from a straight line carapace length of 25 cm to one of 75 cm.

Other estimates based on data from naturally developing populations

are 26 years (Henwood unpublished data), and 14.3-19.3 years (Zug et

al. 1983). The period calculated with data from captive turtles by
Frazer and Schwartz (1984) was 19-20 years.

Limpus (1985) pointed out that the rate of development very likely
varies widely from one population of Caretta to another, and Balazs
(1982) found this to be the case with CheTonia in the Hawaiian
Archipelago. In any case, to date nobody appears to have estimated
a developmental rate fast enough to allow the Azores loggerheads to
reach the 40-cm straight-carapace-length of the Florida subadult colony
within the travel time of the main-stream, direct drift-bottle routes
available. By any of these they would arrive in America too small
to join any known western Atlantic size class. Where they pass the
time required for the necessary growth is not clear.

What appears to be significant evidence of continued post-Azores
travel in the Gulf Stream system is the fact that wherever loggerheads
turn up in the Macronesian area or in the Spanish Mediterranean (Fig. 7)
they are usually small. Brongersma (1982) found shell lengths of logger-
heads from Macronesian waters (the Azores, Madeira, Canary Islands,
Selvagens Islands) to range from about 25 cm to about 50 cm. Five
young loggerheads (approximately 26 cm SCL) were recently sighted by
Ron Gilmer on a Woods Hole Cruise (Oceanus 176) between Cadiz and the
Canary Islands (33°12'N 15°00'W; 30°01'N 14°21'W; 30°O1'N 13°43'Ws
29°15'N 12°56'W; 27°41'N 15°46'W). The juveniles taken on Princesse
Alice Bank colony, however, are consistently the smallest of the lot.
It might be assumed that their somewhat larger sizes in downstream
localities reflect periods of stop-over in those localities. In most

15



INTRODUCTION

Thirty years ago when interest in sea turtles was beginning to
spread, the habitat of the post-hatchlings for all the species was
unknown. After they left the nest and made their way through the surf,
they simply disappeared. Very slowly, data to suggest a pelagic life -
in a sargassum weed habitat accumulated, and eventually I received
support to investigate that idea intensively. By the end of that
research period it was clear that when sargassum rafts are present
in longshore arrays within the swimming range of the hatchlings, they
do in fact enter them (Carr 1982). It followed that the early develop-
mental stages are pelagic, with the corollary that, because sargassum
accumulates along convergences, the adjacent currents may carry the
rafts and their occupants on journeys of either local or oceanic extent
or both.

Until lately the so-called lost-year puzzle has seemed mainly
an academic concern. It has now become clear, however, that the missing
pelagic stage is more protracted than was initially believed, and that
during this time the turtles are brought into intimate contact with
concentrated marine pollution. Growing awareness of the steady spread
of marine debris and pollutants, of the tendency of these to collect
along frontal driftlines, and of the habit of hatchlings to eat virtually
any smal] object within reach, made closer investigation of this phase
of sea turtle life seem urgent. Cruises and aerial searches for sar-
gassum lines were made, and hundreds of interviews with seamen and
commercial and sports fishermen were carried out. As understanding
of the aims of the investigation spread, reports from sea-going people
and volunteer collaborators began to lend substance to the sargassum
theory of hatchling ecology. Besides the numerous specific records
obtained, there were many other occasions when, in casual or group
conversations, it was heard that "at some times of the year you see
little turtles in the berry grass." Table 1 provides substantial (though
partial) documentation of the case for a pelagic and driftline habitat
for young sea turtles.

Thus, it is now well established that hatchling sea turtles go
into sargassum driftlines if there are any within their initial locomotor
reach (Carr 1985). Proof that they remain in the rafts has come more
slowly, but juveniles showing weeks or months of growth have been re-
corded from many localities (Table 1). It is to be expected that the
recovery sites for advanced post-hatchlings may be far from any known
breeding grounds. Because sargassum lines regularly form at the shore-
ward walls of major currents, young turtles that enter them are likely
to be quickly taken away from their place of origin. The advanced
juvenile loggerhead found by R/V Geronimo in the edge of the Sargasso
Sea (Fig. 1) very likely came from a Florida breeding beach, where
the Gulf Stream comes close to shores on which heavy nesting occurs.
vAs’another example, during a Woods Hole cruise of R/V Cape Florida,
Lisa -Bibko photographed a saucer-size green turtle resting on top of
rafts of dense sargassum up to four feet thick off Matanilla Reef at
the northern tip of Little Bahama Bank. The turtle was one of two
seen there. It was not taken aboard, but Bibko photographed it from

1



Figure 9. Subadult loggerheads of the size group in the Indian River Lagoon
System. (Lew Ehrhart photo. )

36



Caldwell, D.K., A. Carr and L.H. Ogren.

1959.

Carr, A.
1963.

Carr, A.
1967.

Carr, A.
1982.

Carr, A.
1985.

Carr, A.
1986.

Carr, A. and
1980.

The Atlantic loggerhead sea turtle, Caretta caretta caretta
(L.) in America. I. Nesting and migration of the Atlantic
loggerhead turtle. Bull. Fla. State Mus., Biol. Sci.
4(10)295-308.

Panspecific reproductive convergence in Lepidochelys kempi.
In Animal Orientation, Ergebn. der BiologTe 26 :298-303.

So Excellent a Fishe: A Natural History of Sea Turtles.
Natural History Press, Garden City, N.Y. 249 p.

Final Report, World Wildlife Fund Project 1800. 15 p.

Surveys of sea turtle populations and habitats in the
western Atlantic. Final report, Contract No. NA80 6A-C-0071,
NOAA-NMFS, Panama City, Florida. 44 p. and 19 appendices.

Rips, fads and little loggerheads. BioScience 36:92-100.
A.B. Meylan

Evidence of passive migration of green turtle hatchlings
in sargassum. Copeia 2:366-368.

Carr, A., A.B. Meylan, J. Mortimer, K. Bjorndal and T. Carr.

1982.

Carr, A., L.
1980.

Ehrhart, L.M.
1980.

Ehrhart, L.M.
1983.

Frazer, N.B.
1984.

Surveys of the sea turtle populations and habitats in
the Western Atlantic. NOAA Tech. Memo. NMFS-SEFC-91:1-91.

Ogren, and C. McVea.
Apparent hibernation by the Atlantic loggerhead turtle
Caretta caretta off Cape Canaveral, Florida. Biol. Conserv.

Threatened and endangered species of the Kennedy Space
Center: marine turtle studies. NASA Contract Report
163122. KSC TR 51-2, Vol. IV, Part 1. 407 p.

Marine turtles of the Indian River lagoon system. Fla.
Scientist 46:337-346.
and F.J. Schwartz.

Growth curves for captive loggerhead turtles, Caretta caretta,
in North Carolina, U.S.A. Bull. Mar. Sci. 34:485-489.

24



Archie Fairly Carr, Jr.

1909-1987



60 |
“LOST YEAR” TURTLES n +134
WE oazores n+ 82
50> (CO Mosouito LAGOON, GEORGIA TRAWLER
CAPTURES, CANAVERAL SHIP CHANNEL
Y n+ 569

ao 4 8 CAPE CANAVERAL NESTING FEMALES
w n= 80
a
a
=
<
@ 304
wu
°
R

20-4

ie

° + +

10 20 30 40 50 60 70 80 90 100 Ho
STRAIGHT LINE CARAPACE LENGTH (cm)
Figure 5. Comparative size distribution in three age groups of Caretta

from the western Atlantic (Hillestad et al. 1977, Ehrhart 1980,
Mendonca and Ehrhart 1982, Ogren and McVea 1982) and one from
the Azores, (Unnublished data from the Department of Oceanography
and Fisheries, University of the Azores, )

32



Scully-Power ,

1986.

Smith, W.G.
1968.

Uda, M.
1938.

Vaughan, P.
1981.

Witham, R.
1974.

Zug, G.R., A.

1983.

P.
Navy Oceanographer Shuttle Observations STS 41-G. Mission
Report. NUSC Technical Document 7611. 146 p.

A neonate Atlantic loggerhead, Caretta caretta caretta,
captured at sea. Copeia 4:880-881.

Researches on Siome or current rip in the seas and ocedns.
Geophysical Magazine 11:307-372.

Marine turtles: a review of their status and management
in the Solomon Islands. Report to World Wildlife Fund:
Project No. 1452, 70 p.

Neonate sea turtles from the stomach of a pelagic fish.
Copeia 2:548.
Wynn and C. Ruckdeschel.

Age estimate of Cumberland Island loggerhead sea turtles.
Mar. Turtle Newslet. 25:9-11.

27



invertebrates that release eggs or larvae to be carried by currents

on planktonic developmental journeys--and so, are drawn into the drift-
lines. Although it is the overt swimming of these animals that takes
them away from shore and out to the weedlines, it is downwelling that
keeps them in the fronts--and these gather flotsam of any size, from
pollen grains to drifting wrecks.

This effect is not restricted to material that floats on the sur-
face. When plankton or nekton which by any mechanism are able to control
their buoyancy and maintain a preferred depth are drawn in, they resist
the sinking action, accumulate at their preferred depth, and give to
the ecologic organization at the front a vertical dimension (Olson
and Backus 1985).

In The Arcturus Adventure, William Beebe (1926) described the
spectacular biological diversity in an oceanic rip between Easter Island
and the Galapagos without mentioning the role of downwelling in creating
the imposing factor. Lamb (1959-63) recorded a biologically rich front
on May, 1963, in the open ocean 340 miles east of New York (41°N
66.30°W), at the convergence of the Gulf Stream and Labrador Current.

No mention of the role of downwelling and advection was made. The
confluence was marked by a wall of "sea smoke" up to 150 feet high.
There was a profusion of marine life at the surface which the observer
attributed to upwelling, and great numbers of sea birds of twelve
different species and various stages of maturity were diving and feeding
along the line. An unusual feature of the gathering were numerous

flocks of grey phalaropes, each consisting of hundreds of birds, wheeling
over the dense lane of sea life. The phalaropes seen were probably

en route to Great Lakes and Canadian breeding grounds, and their presence
Suggests the possible importance of high-seas rips in the oceanic
migrations of birds other than the dedicated divers. A few animal-
oriented zoologists--notably sea-bird ecologists (Ashmole and Ashmole
1967, Ashmole 1971) and tuna and billfish specialists (Murphy and Shomura
1972)--have understood the bearing of downwelling on animal ecology.

In most discussions of marine productivity and faunal abundance, however,
upwelling (divergence) is stressed, and the role of convergence--the
more immediate agent in concentrating biological activity--is not

given due emphasis. Its action is fundamentally important to the
ecologic organization of the epipelagic. I have elsewhere suggested

(Carr 1986) that there would be no sea turtles of the kinds we know

if there were no fronts.

THE DEVELOPMENTAL TRAVEL OF ATLANTIC CARETTA

After a period of pelagic developmental migration had been shown
to be a stage in the sea turtle life cycle, an assessment was made
of our ability to piece together the overall developmental habitat-shifts
of any of the species. Little or nothing could be done with the Pacific
turtles, because of the almost total lack of information on the immature
stages. In the Atlantic the most inviting species seemed to be Caretta.
It has major nesting grounds in U.S. waters, and is represented on
the east coast of Florida by four different age classes as follows:
(1) newly emerged hatchlings; (2) advanced hatchlings and juveniles

ll



deep, that moves over the sill into the Mediterranean at the Straits

of Gibraltar. To suppose that the many young loggerheads reported

from the eastern Atlantic have travelled upstream and out of the Mediter-
ranean goes against what is known of post-hatchling movements elsewhere.

Instead of contributing turtles to the Atlantic population, the
Mediterranean more probably receives strays from the trans-Atlantic
migrations of American turtles. Recent interviews along the coast
of the Spanish Mediterranean suggest that some of the Azores loggerheads
may drift out of the main Canary Current and into the branch that moves
across the Gibraltar sill, where adult loggerheads occasionally appear
to move through in both directions. This possibility is supported
by conversations with fishermen along the coast of the Spanish Mediter-
ranean, and with Joan Mayol of the Balearic Islands. Mayol's data
(Fig. 7) indicate the presence of numerous immature loggerheads in
Spanish Mediterranean waters that are consistently a little larger
than those of the Azores size class. This assemblage of juvenile logger-
heads may reflect the abundance of food resources along a recently
discovered permanent front, extending across the western Mediterranean
from Almeria, Spain to Oran, Morocco and through the Baleares
(LaViolette i986).

Mayol has reported heavy mortality of these turtles, which are
taken incidentally by shark fishermen. According to his estimate,
around 16,000 a year are caught on 4-inch hooks baited with squid.

He believes that most of these die of injuries incurred in the process
of release. Mayol is trying to devise a hook that will catch sharks
but do less damage to the turtles and he is sending an observer aboard
some of the boats to work out ways to minimize the effects of the sur-
gery. I have arranged with his office to carry out a collaborative
tagging project, with the aim of learning whether any of the Baleares
loggerheads do emerge from the Mediterranean, and whether any of those
tagged at Faial arrive there.

Although consanguinity of the young loggerheads of the eastern
and western Atlantic now seems probable, much remains to be learned
about the ecology and developmental travel of the migrants before they
leave their pelagic stage and take up adult life along the American
continental shelf. As any generalized chart of. the surface currents
of the Atlantic shows, a drift bottle released on Princesse Alice Bank
and washed up on a Florida beach may have travelled by any of several
downstream paths. If the Azores population does indeed come from
America, and does eventually return there--and both now seem probable--
the turtles have made both crossings of the Atlantic as passive Gulf
Stream migrants. Whether adult Caretta has a capacity for long range,
open-sea navigation, and if so, at what ontogenetic stage this appears,
are unknown, Because mature loggerheads show breeding site fidelity,
after ranging widely between nesting seasons (Limpus 1985, Ehrhart
1983), the adults must share at least some of the bi-coordinate open-sea
travel-guidance sense that Chelonia evidently employs in commuting
between its feeding pastures and nesting shores. It seems likely,
however, that when the young pelagic loggerheads leave European waters
they still travel as passive migrants in currents.

14