Legal Status of the Species

The Olive ridleys are Schedule I species under the Wildlife (Protection) Act, and are listed as 'endangered' in the IUCN Red Data Book, in the 'Appendix-I' of CITES (Convention on International Trade in Endangered species of wild Flora and Fauna), and also listed in the CMS (Convention on Migratory species). India being a signatory nation to all these conventions has the responsibility of protecting this species of sea turtle and its nesting beaches, breeding, feeding and congregation areas, as well as its migratory pathways in the sea.

Nesting Areas and Main Rookeries

Olive Ridley sea turtles come to Orissa coasts for nesting in large numbers. Hence the activity is termed 'mass nesting' or 'arribada'. Worldwide attention is focused on the conservation of Olive Ridley Sea Turtle (Lepidochelys olivacea) in Orissa because about 50% of its world population comes to Orissa coasts for nesting, and this is about 90% of the population of sea turtles along the Indian coast.

During the period from October to early summer, shallow seas near the river mouths become ideal feeding grounds for the Olive Ridley Sea turtles. At these places they also breed and look for undisturbed beaches for nesting.

The known major breeding grounds in Orissa where such congregation takes place are located near the river mouths off Dhamra, Devi, and Rushikulya, although there are also minor breeding grounds near other river mouths such as the Mahanadi, Subarnarekha, Budhabalanga, Keluni and Bahuda.

The famous mass nesting site of Olive Ridleys close to the mouth of Brahmani-Baitarani (Dhamara), received worldwide recognition in 1975-76 as one of the largest rookeries of the Ridleys.

Threats

The sea fishing activities have direct adverse impact on the adult sea turtles and their hatchlings. Olive ridleys usually mate between October to February, when they congregate in the shallow coastal waters for prolonged periods, making them vulnerable to the fishing nets and propellers of the trawlers.

The other threats to sea turtles include:

1. Loss or modification of the nesting beaches due to Casuarina plantation:
2. Fishing by gill nets; and development of fishing bases at the potential nesting sites and breeding areas;
3. Strong illumination around nesting beaches which greatly disorients the adult turtles as well as the hatchlings;
4. Large scale vessel movement in congregation zones severely disturb mating and breeding;
5. Nests and eggs are destroyed by predators like dogs, jackals, hyenas, etc., and by beach erosion.

The most significant of these threats is 'incidental catch' in marine fisheries (where a few thousand turtles are killed in trawl and gill nets every year), as well as depredation of turtles eggs by feral and wild predators.

Population Estimate of Nesting Sea Turtles

Recorded figures of the number of turtles which laid eggs in different rookeries and the number of turtle casualties detected in different years are as follows:

Year	No. of Nesting Turtles at Rookeries (in lakhs)			No of turtle casualties detected along the Orissa coast during the year	Fishing vessels seized in Gahirmatha Marine sanctuary
	Gahirmatha	Devi	Rushikulya
1998-99	2.98	not counted	No mass nesting	13,671	50
1999-00	7.11	25,000	No mass nesting	15,732	18
2000-01	7.41	No mass nesting	1.59	5,483	37
2001-02	No mass nesting	No mass nesting	0.35	12,977	135
2002-03	0.73	No mass nesting	2.08	10,086	63
2003-04	2.43	No mass nesting	2.01	4,981	37
• Gahirmatha: (Dhamra river mouth to Mahanadi river mouth)
Source: Wild Orissa 2004 (Forest Department, Government of Orissa)

 

Estimate of Nesting = [Total Area available for nesting (m2) X Duration of Arribada (min) X Sum total of egg laying turtles counted]

[Width of each strip or transect (m) X Number of sampling periods X {Sum of the lengths of all strips or transects (m)} X Average duration of oviposition (min.)]

OR

102460 X 1020 X 1221   = 127605733200 = 23104 20 X 17 X 1048 X 15.5   = 5522960

Estimate of Nesting can also be calculated as follows:

Estimate of Nesting = [Sum total of egg laying turtles counted X Beach segments to transect ratio X Duration of each sampling interval]

[Average duration of Oviposition of nesting turtles (Min.)]

Where, Proportional area of nesting beach segment to transect = 100 meters/ 20 meters = 5 Duration of each sampling interval = 1 hour = 60 minutes. Hence, Estimate of Nesting = Sum total of egg layingturtles counted X 300 Average duration of oviposition (Min.) There may be negligible variations in the results obtained from both calculations. Estimated numbers of Olive ridley sea turtles during mass nesting in different mass nesting beaches of Orissa coast during last five years (2003-04 to 2007-08) Season No. of nesting turtles (in lakhs) Total (in lakhs) Gahirmatha Rushikulya 2003-2004 2.43 2.01 4.44 2004-2005 2.34 0.89 3.23 2005-2006 2.67 1.98 4.65 2006-2007 1.46 - 1.46 2007-2008 - 1.80 1.80 Source: Wild Life Census in Orissa (Forest & Environment Department, Government of Orissa)

Table 1. Consensus estimates for nesting population size in Gahirmatha derived from multiple sources; the estimate refers to the largest arribada during aseason, usually the first. No estimates are available for arribadas at the Devi river mouth and Rushikulya. The estimates marked in bold are considered as particularly reliable. Dates ofmass nesting at the three rookeries in Orissa from Shanker et al (2004).

Year	Consensus estimate	Gahirmatha	Date of Arribada
			2nd arribada	Devi	Rushikulya
1975-76	158,000	?	No data	No data
1976-77	150,000	?	No data	No data
1977-78	150,000	Dec 28 -Jan 2		No data	No data
1978--79	133,000	Feb 3-9		No data	No data
1979-80	218,000	Feb 9-11		No data	No data
1980-81	191,000	Jan 12-19		Date unknown	No data
1981-82	0	No arribada		No data	No data
1982-83	200,000	Feb 3-6	Apr 4-9	No data	No data
1983-84	300,000	Jan 25-Feb 5	Mar 25-29	No data	No data
1984-85	280,000	Jan 14-30	Mar 16-19	May 26-29	No data
1985-86	50,000	Mar 31-Apr 6		No data	No data
1986-87	386,000	Jan 5-14	Mar 8--14	No data	No data
1987-88	0	No arribada		No data	No data
1988-89	300,000	Jan 25	No data	No data
1989-90	200,000	Mar 4-14		No data	No data
1990-91	350,000	Mar 6-14	Apr 28	No data	No data
1991-92	320,000	Jan 23-Feb 1	Mar 21	No data	No data
1992-93	350,000	?	No data	No data
1993-94	350,000	Feb 2-13		No arribada	Mar 1-8
1994-95	340,000	?	No arribada	Mar 14-16
1995-96	200,000	Jan 1-16		No arribada	Mar 6-8
1996-97	0	No arribada		Mar 14-17	Jan 31-Feb 3
1997-98	0	No arribada		No arribada	Mar 20-23
1998-99	180,000	Mar 26-30		Feb 22-23	No arribada
1999--00	?	Mar 13-19		No arribada	No arribada
2000--01	?	Feb 2-?		No arribada	Feb 26-Mar
2001--02	0	No arribada		No arribada	No arribada
(Reprinted with permission from Shanker et al 2004.)

Source - Marine Turtles of the Indian Subcontinent editedby Mr. Kartik Shankear & Mr. B C Chowdhury
(UNDP - Wild Life Institute of India.)