ML20003G368

Successful Relocation of Sea Turtle Nests Near St Lucie Plant,Hutchinson Island,Fl.

ML20003G368
Person / Time
Site:	Saint Lucie
Issue date:	01/31/1981
From:	APPLIED BIOLOGY, INC.
To:
Shared Package
ML17266A448	List: ML17266A447 ML20003G368
References
ABI-317, NUDOCS 8104290241
Download: ML20003G368 (22)

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! SUCCESSFUL RELOCATION OF SEA TURTLE f4ESTS

! fiEAR THE ST. LUCIE PLAfiT

! HUTCHINSON ISLAND, FLORIDA I .

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SUCCESSFUL RELOCATI0fl 0F SEA TURTLE NESTS .

NEAR THE ST. LUCIE PLANT I HUTCHIfiSON ISLAND, FLORIDA JANUARY 1981 I

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APPLIED BIOLOGY, INC.

ATLANTA, GEORGIA l

I CONTENTS Page I INTRODUCTION ...................................................... 1 O

MATERIALS AND METHODS ............................................. 2 RESULTS AND DISCUSSION ............................................ 4 Nesting Density .............................................. 4 I Nesting Success ..............................................

T u rtl e Ne s t Rel oc a t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Green and Leatherback Turtles ................................

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SUMMARY

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LITERATURE CITED .................................................. 12 FIGURES ........................................................... 13 t

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If4TRODUCT10f4 Every year, from May to September, many Atlantic loggerhead turtles (Caretta caretta) use Hutchinson Island, Florida as a major nesting area .

(Gallagher et al.,1972). In addition, a small number of nests are made by Atlantic green turtles (Chelonia mydas) and leatherback turtles (Dermochelys coriacea). The extent and distribution of turtle nesting on the island has been monitored in alternate years since 1971 by Florida Power & Light Company to evaluate any potential influences from the construction and operation of the St. Lucie Plant. Maintaining the vi-tality of the Hutchinson Island rookery is important in view of the declining world populations of marine turtles (IUCii, 1969, 1971; fiMFS, 1978).

The Florida Power & Light Company began construction of the cooling water discharge system for the St. Lucie Plant Unit 2 in 1980. This system utilizes a 5-meter diameter pipe buried under the beach and nearshore areas to carry the heated water to an offshore discharge. The installation of this pipe involves construction of a trench through the barrier dune and beach and the installation of a cofferdam from the beach to the end of the pipe. This construction is similar to that used in 1975 when the Unit 1 discharge pipe was installed.

The 1975 construction was shown to reduce nesting by sea turtles in the area of construction activity (ABI,1977). After the construction was completed, sea turtle nesting returned to normal.

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Florida Power & Light Company was concerned for the well being of the turtles and asked Applied Biology, Inc. (ABI), to monitor turtle nesting activity during the discharge pipe construction period. Additionally, to c protect eggs incubating in nests in the construction area from possible destruction, a nest relocation program was implemented. Because the Atlantic loggerhead turtle has been the dominant species nesting on the island, discussions are based on this species unless otherwise noted.

MATERIALS AND METHODS Four of the nine 1.25-kilometer-long segments of beach established as sample areas by Gallagher et al. (1972) were used for the nesting survey (Figure 1). These areas are located from 3 kilometers north of the power plant to 8 kilometers south of the plant and are numbered Area 3 through Area 6. The sample areas are approximately equidistant from each other along the island and are typical of nearby beach habitats. It was assumed that the distribution of turtle activity in the sample areas would be comparable to previous studies and, therefore, representative of nesting patterns established for Hutchinson Island (ABI, 1979). Any l change in nesting trends observed in Sample Area 4 (the plant site) would be considered to be due to construction activity.

I The four sample areas were surveyed each morning from 1 May through 15 Septemter using small off-road motorcycles to locate and mark each new nest. Nests were marked with a stake, numbered, and dated to maintain accurata counts of the number and distribution of nests. Records were kept of raccoon nest predation and unsuccessful nesting attempts (false

.rawls) by turtles.

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Sample Area 4 is adjacent to the power plant where construction was planned. Any nests made in the southern 0.8 kilometer of this area were considered to be potentially affected by construction activity and were o relocated to a beach area 4.4 kilometers south of the power plant (Figure 1).

Limpus et al. (1979) found a significant decrease in hatching rates of loggerhead eggs that had been moved and inverted between 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and 14 days after laying. To avoid this mortality, all eggs to be moved from the construction site vicinity were relocated within 12 hours of deposition. The eggs were counted, reburied and allowed to hatch under natural conditions.

At certain times, raccoon predation on the relocated nests required the setting of live traps to remove the predators. Additionally, some relocated nests were covered with poultry wire to prevent predation. All relocated loggerhead nests and a comparable number of undisturbed nests from Areas 3, 5 and 6 were examined after signs of hatchling energence to determine hatch success. Records were kept of the incubation period, number of hatched and unhatched eggs, and live or dead hatchlings remaining in the nest. The hatching success of undisturbed nests was compared to relocated nests to detect any adverse effects from handling the eggs.

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RESULTS AND DISCUSSION Nesting Density The total of 528 loggerhead nests observed within the four survey -

areas during 1980 is consistent with nest production in these areas during the five previous survey years (Figure 2). Maximum nesting occurred in June as it has in most previous years (Figure 3).

Additionally, the percentage of nests deposited in Area 4 in 1980 was 25 percent of the total nests observed in Areas 3 through 6. This is con-sistent with previous surveys in which the Area 4 percentage of the total nest production in Areas 3 through 6 ranged from 21 to 27 percent. The one exception occurred in 1975 when construction activity and lights on the beach at night reduced the nesting in Area 4 to 11 percent of the total production in Areas 3 through 6.

In each survey since 1971, a gradient of nest density has been observed with the lowest densities being found on the northern portion of the island. Linear regression analysis of variance of nest density with respect to distance from the Ft. Pierce Inlet has been used to describe the gradient of nesting during previous surveys (ABI,1979). The linear regression equation expressing nest density along the island in 1980 is Y = 51. 57 + 4. 92X ; r2 = 0. 68 ;

where: Y = a + bX, Y = Number of nests, a = Y intercept, b = Slope of the regression line, X = Kilometers from Ft. Pierce Inlet.

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While the regression equation for 1980 is based on val ues from four sample areas and past studies were based on nine areas, the slope of 4.92 is consistent with the values (range 1.57 to 7.71) representing the spa- .

tial distribution of turtle nests observed during previous surveys.

The total number of nests deposited on Hutchinson Island during each of the five previous survey years has been calculated using the area under the regression line that best describes nest density distribution along the island (Gallagher et al., manuscript in preparation). An esti-mate of 4168 loggerhead nests on the island was calculated for 1980 using the regression line calculated from the four areas. This number is within the range of 4000 to 5400 nests estimated on the island each sur-vey year since 1971.

l Previous turtle tagging studies suggest that it is reasonable to estimate that one turtle utilizes the Hutchinson Island survey beach for every two nests produced (ABI,1979; Ehrhart,1979). Using this estimate of two nests per female , a nesting population of 2084 turtles was I calculated for the 1980 season. Population estimates from surveys since 1971 indicate the female population nesting on Hutchinson Island is fairly stable at over 2000 individuals.

I Nesting Success i

Turtles may crawl up on the beach and even begin nest excavation only to return to the sea without depositing eggs. The cause of these unsuc-l cessful nesting attempts (false crawls) is not understood, but their fre-9

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quency may reflect the overall suitability of a beach for nesting. The index derived from false crawl data used in this and previous reports has been termed " nesting success" and is defined as: e I S

, N N+F x 100 where: S = Percent nesting success, N = Number of nests, F = Number of false crawls.

Nesting success has generally declined in each of the four survey areas since 1975 (Figure 4). The overall nesting success for the. four areas has declined each year from a maximum of 54 in 1975 to a minimum of 45 in 1980. This is a continuation of the slight long-term decline in I overall nesting success' observed on Hutchinson Island since 1975 (ABI, 1979). The cause of this decline in nesting success is not known.

i Turtle Nest Relocation In all, 89 loggerhead turtle nests containing a total of 9948 eggs I were removed from Area 4. In addition, one green turtle nest was removed and turned over to Mr. Ross Witham of the Florida DNR for the Head-Start Program.

The mean clutch size was 111 eggs with a range of 50 to 158 eggs per I nest. Caldwell et al. (1959) reported a somewhat larger average clutch size of 126 eggs (range 64 to 198) for 71 nests on Cape Romain, South Carolina. He further observed that the number of eggs per cl utch decreased as the nesting season progressed. For Hutchinson Island, a fl 6 J

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linear regression analysis of clutch size in relation to time in the nesting season showed a relationship described by the equation:

Y = 124.4 - 3.0X; r2 = 0.70; o where: Y = a + bX, a = Y intercept, X = Time of nesting season, b = Slope.

The regression equation predicts a 17.3 percent reduction in clutch size of those nests deposited the last two weeks of the season compared to those deposited during the first two-week period (Figure 5).

Incubation Period Hirth (1971) has defined incubation period as the period between ovi-position and emergence of the largest number of hatchlings on the surface. This qualification is necessary as emergence from a single nest I may occur over several days. The incubation period for Hutchinscn Island l nests ranged from 46 to 60 days with a mean of 50.5 days for the relo-cated nests and from 46 to 61 days with a mean of 50.1 days for undisturbed nests. A t-test evaluation showed no significant difference I (P10.05) in incubation periods for the two groups. A delay in the hatching of eggs from relocated green turtle nests reported by Prichard (1967) was not observed in the loggerhead nests relocated during this study.

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Incubation periods for eggs deposited during the beginning of the nesting season and those deposited late in the nesting season were longer than the incubation periods for eggs deposited during mid-season (Figure .

6). Caldwell et al. (1959) found a similar temporal pattern of incuba-tion periods among loggerhead nests in South Carolina. He concluded that incubation periods shortened as the seasonally increasing temperature and amount of sunlight increased the total amount of heat received by the nests. .

Hatch Success Hatch success was determined by digging up nests after hatchling emergence and counting the number of hatched eggs, unhatched eggs and live or dead hatchlings still in the nest. Hatch success, the number of viable hatchlings reaching the surface, was calculated using the formula:

S= N-(U + D) x 100 E

where: S = Hatch success, N = Number of hatched eggs, U = Number of unhatched eggs, D = Number of dead hatchlings, E = Total number of eggs.

l Counting hatched eggs may introduce a source of counting error into this equation if the total number of eggs in the clutch is not known because l many shells are reduced to fragments. For this study, the counting error in the field effort was determined by comparing the field count of hatched eggs with the actual clutch size. The mean counting error for 3

I eggs in all relocated nests was 5.3 percent or only a 1 percent error in hatch success.

9 Hatch success of relocated nests averaged 80.9 percent while the hatch success of undisturbed nests averaged 84.5 percent. The mean hatch success for undisturbed nests may be artificially high because of the diffit.ulty in locating unsuccessful and infertile nests after the normal incubation period. However, because hatch success rates for the two groups are not significantly different (P(0.05), handling of the eggs during the relocation process did not reduce nest viability.

I Green and Leatherback Turtles Green and leatherback turtles nest on Hutchinson Island, but less comonly than the loggerhead. Since 1971, the number of green turtle nests has ranged between 5 and 37 per year, while leatherback nest num-bers were between 1 and 7 (ABI,1979). Although an entire island count is not available for 1980, the beach bounded by Areas 3 and 6 inclusive contained 14 green turtle nests and 4 leatherback nests. The majority of l green turtle nests were observed between Areas 5 and 6, and for the first l

time, green turtle nests were observed adjacent to the St. Lucie Plant.

This may be a continuation of the gradual northward shift in the pre-ferred nesting location observed for green turtles since 1971 (ABI, 1979).

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SUMMARY

Limited construction activity associated with installation of the Unit 2 discharge system during the sunmer of 1980 had no apparent adverse o effect on marine turtles nesting on Hutchinson Island. Nest densities I within the construction site and nearby areas were consistent with den-sities observed during previous surveys. Based on the 528 loggerhead nests observed in survey Areas 3 through 6, an estimate of 4168 nests was made for the island. This is consistent with the number of nests occurring on the island each year since 1971. The gradual decrease in nesting success observed since 1975 continued. Nesting success in the four survey areas combined was 45 percent in 1980.

In all, 89 loggerhead nests were relocated from the proposed construction site. Mean clutch size was 111 eggs. Relocating the nests did not significantly alter the hi.tch success as compared to undisturbed nests, nor did relocation affect the incubation period. In general, nests deposited early in the season contained more eggs than nests laid later in the season. The incubation period, however, was longer for eggs deposited either early or late in the season than eggs laid during mid-season.

I The rate of raccoon predation on nests varied between areas but was similar to 1979 levels. Predation in the relocation area was reduced by trapping raccoons and covering nests with poultry wire.

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I The number and distribution of green and leatherback nests was simi-lar to previous surveys, but for the first time since the surveys began green turtles nested adjacent to the power plant. -

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LITERATURE CITED ABI. 1977. Ecological monitoring at the Florida Power & Light Co. St.

Lucie P1 ant, annual report 1976. Vol . 1 and 2 AB-44. Prepared by I Applied Biology, Inc., for Florida Power & Light Co., Miami, Fla.

. 1979. Annual non-radiological environmental monitoring report, St. Lucie Plant, Vol. III biotic monitoring, 1978. AB-177.

Prepared by Applied Biology, Inc., for Florida Power & Light Co.,

Miami, Fla.

Caldwell , D.K. , F. H. Berry, A. Carr, and R. A. Ragotzkie. 1959. The Atlantic loggerhead sea turtle, Caretta caretta caretta (L. ) , in America. Bull. Fla. State Mus. Biol. Sci. 4:293-348.

Ehrhart, L.M. 1979. Threatened and endangered species of the Kennedy Space Center: Marine turtle studies i_n,n A continuation of baseline studies for environmentally monitoring space transportation systems (STS) at John F. Kennedy Space Center. Contract No. fas 10-8986.

Vol. IV fMSA Rept. 163122 Sept. 1980.

Gallagher, R.M., M.C. Hollinger, R.M. Ingle, and C.R. Futch. 1972.

Marine turtle nesting on Hutchinson Island, Florida in 1971. Spec.

Sci. Report No. 37, Fla. Dept. Nat. Res. Mar. Res. Lab. Pub.11 pp.

Gallagher, R.M. , J. O'Hara, and P f. Worth. In preparation. Character-istics of loggerhead turtles nesting on Hutchinson Island, Florida.

I Hirth, H.F. 1971. Synopsis of biological data on the green turtle Chelonia mydas (Linnaeus) 1758. FAO Fisheries Synopsis, No. 58 IUCN. 1969. Marine turtles - proceedings of working meetings, marine turtle specialists. IUCN Publ . News Ser. , Suppl. Pap. 20. 100 pp.

. 1971. Marine turtles - proceedings of 2nd working meeting, marine turtle specialists. IlcN Publ. News Ser. Suppl. Pap. 31. 109 pp.

Limpus , C.J. , V. Baker, and J.D. Miller. 1979. Movement induced mor-tality of loggerhead eggs. Herpetologica 35(4):335-338.

Final EIS listing and protecting the green sea turtle I NMFS. 1978.

(Chelonia mydas), loggerhead sea turtle (Caretta caretta) and the Pacific Ridley sea turtle (Lepidochelys olivacea) under the Endangered Species Act of 1973. National Marine Fisheries Service, I Dept. of Commerce, Washington, D.C.

Jersey City, Pritchard, P.C. H. 1967. Livin; turtles of the world.

New Jersey T.F.H. Publications, Inc. 288 pp.

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