Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 April 2021 | 13(5): 18313–18318
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
https://doi.org/10.11609/jott.6302.13.5.18313-18318
#6302 | Received 15 June 2020 | Final
received 12 March 2021 | Finally accepted 20 March 2021
Marine mammal strandings in the northern Palk
Bay from 2009 to 2020
Vedharajan Balaji 1 &
Veeramuthu Sekar 2
1,2 Organization for
Marine Conservation Awareness and Research (OMCAR), OMCAR Palk Bay Centre,
349B, Velivayal, Rajamadam
Post, Thanjavur District, Tamil Nadu 614701, India.
1 director@omcar.org (corresponding
author), 2 sekarveera15@gmail.com
Editor: E. Vivekanandan, Central Marine Fisheries Research Institute,
Chennai, India. Date of publication:
26 April 2021 (online & print)
Citation: Balaji, V. & V. Sekar (2021). Marine mammal strandings
in the northern Palk Bay from 2009 to 2020. Journal of Threatened
Taxa 13(5): 18313–18318. https://doi.org/10.11609/jott.6302.13.5.18313-18318
Copyright: © Balaji & Sekar 2021. Creative Commons Attribution
4.0 International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: Light House Foundation,
Germany; Rufford Foundation, UK.
Competing interests: The authors
declare no competing interests.
Acknowledgements: Our sincere thanks to
Tamil Nadu Forest Department (Thanjavur and Pudukottai districts), Marine Police Department, Light
House Foundation, and Rufford Small Grants Programme.
Abstract: Globally, the marine
mammal population has been under threat due to various human activities. Data on stranding of these animals that are
important for effective conservation planning and management, however, are not
available in most of the developing countries.
This paper presents observations on marine mammal strandings
in northern Palk Bay, the southeastern coast of India over the last
decade. In total, 21 stranding events
consisting of 23 marine mammals were observed from 2009 to 2020. These stranded mammals include a Humpback
Dolphin, a Blue Whale, two Finless Porpoises, and 19 Dugongs. The evident reason for the death of the
dugongs and the porpoise being fishing activities, regulations on fishing
practices, and intensive monitoring of the existing dugong population and their
habitats are necessary. This study
recommends for establishment of conservation reserve, and setting up
district-level marine mammal rescue and release units in Nagapattinam,
Tiruvarur, Thanjavur,
Pudukkottai, and Ramanathapuram districts, comprising
fishers and line departments. These units need to be sufficiently equipped in
terms of equipment and infrastructure, and periodical technical training and
workshops on marine mammal rescue and release procedures to quickly respond and
handle marine mammal strandings in the area.
Keywords: Blue Whale, Dugong,
Finless Porpoises, fishing net, Humpback Dolphin, Palk Bay, OMCAR, seagrass.
A variety of marine
mammals such as dolphins, whales, dugong, and porpoise, are found in the vast
marine habitat along the Indian coast.
There are many incidences of these animals getting stranded and
dying. As per Gopalakrishnan et al.
(2014) ‘stranding’ refers to an animal getting outside its survival envelope,
and so ‘marine mammal stranding’ refers to instances where a group or an animal
is washed ashore and unable to move back to the sea (Aragones
et al. 2010). The Central Marine
Fisheries Research Institute (CMFRI) has been publishing marine mammal
stranding records for more than 60 years (Jeyabaskaran
et al. 2013). The earliest of such
instances reported from India are in 1748 (Sathasivam
2000). A well-maintained marine mammals
stranding database provides vital information about the status of marine
ecosystems (Aragones et al. 2010). This paper is about the marine mammal strandings observed by Organization for Marine
Conservation, Awareness and Research (OMCAR) Foundation in the northern Palk
Bay from 2009 to 2020. The objective of
this long-term monitoring of marine mammal stranding is to highlight their
presence in this locality, and promoting their conservation in Palk Bay. This monitoring is important to not only to
conserve marine mammals but also their habitats and to implement sustainable
fishery activities. The monitoring
creates awareness among the public, and hints to the government to consider for
developing policy and guidelines, which is crucial to protect these taxa as per
Wildlife Protection Act, 1972. This
study is based on the data obtained by working with Tamil Nadu Forest
Department and grassroot conservation volunteer groups in the northern part of
Palk Bay, Tamil Nadu, India.
Materials and Methods
The study area in the
northern part of Palk Bay falls in Thanjavur and
Pudukkottai districts of Tamil Nadu (Figure 1).
We received intimations about marine mammal strandings
from local forest officials, fishermen, and marine police. Upon hearing about such an incident, we
reached the stranding site, marked GPS coordinates of the site using Garmin Etrex GPS, and with due permission from the field-officials
of the forest department measurements of the carcass were taken and the state
of the specimen and other information were collected.
Results
In
total, 21 marine mammal stranding events consisting of 23 animals were recorded
between 2009 and 2020 (Figure 1). The
stranded animals included two Finless Porpoises (Image 1 & 12), a Humpback
Dolphin (Image 3), a Blue Whale (Image 4), and 19 Dugongs (Image 2, and 5–11). Other than the 14 dead Dugongs, five Dugongs
were rescued from shore seine nets and released back into the sea during the
four years from 2016 to 2019 jointly by Thanjavur and
Pudukkottai divisions of Tamil Nadu Forest Department, Wildlife Institute of
India, Coastal Security Group of Tamil Nadu Police Department, OMCAR Foundation
and volunteers from the local community.
Discussion
The
12-year observations of this study were made through participatory conservation
efforts by Tamil Nadu forest Department along with other inline departments and
Friends of Dugongs in Thanjavur and Pudukkottai
districts.
Online
database of Marine Mammal Research and Conservation Network of India (MMRCNI)
listed 30 marine mammal stranding records in 120 years from Palk Bay between
1888 to 2009. Most of the records were
from southern Palk Bay, listed for more than a century. This study focused only on a small part of
Palk Bay, which documented a total number 21 observations in 12 years.
Monitoring of marine
mammal stranding is one of the building blocks of 15 years of rapport building
with local stakeholders by OMCAR, through participatory conservation
approach. This is achieved by serving
the basic needs of local stakeholders including conservation-oriented
livelihood support to fishing communities, and integration of management-oriented
restoration and baseline research in coastal habitats to support government
conservation policy. As marine mammals
are scheduled species in the Wildlife Protection Act, 1972, no parts of the
specimen were collected during this study.
Poaching, entanglement in fishing gear, boat accidents, and habitat
destruction are the key factors that threaten the marine mammals of Palk
Bay. The Finless Porpoises, recorded in
2010 and 2020, washed ashore in Mallipattinam (Image
2 and 13). This record shows the
vulnerability of such animals in the fishing grounds of Palk Bay. Out of the 23 marine mammals reported in this
study, only one animal, the Humpback Dolphin, had died due to natural
causes. Veterinary doctors reported that
a catfish spine had penetrated the oesophagus of the
dolphin when the fish was being swallowed.
The Blue Whale that washed ashore in 2015 might have drifted from the
Bay of Bengal through the Palk Strait.
It might have died due to collision with ships in Bay of Bengal, as such
large marine mammals may not prefer to swim into the shallow Palk Bay away from
their migration route (Randage et al. 2014). Most dugong strandings
occurred in summer (Table 1), which may be due to high seagrass growth in
summer. Dugongs graze on seagrass (Heinsohn & Birch 1972; Marsh et al. 1982) and Thanjavur District coast of Palk Bay has 12,243ha of
seagrass beds as determined through an acoustic survey (Balaji 2018). Fourteen
species of seagrass have been reported in this region (Kannan et al.
1999). The biggest threats to the
Dugongs and seagrasses are from unsustainable fishing methods, eutrophication,
and poor waste management. The seagrass ecosystem does not recover fast once
destroyed (Kirkman 1997). It is
estimated that about 75 to 100 Dugongs occur in Palk Bay based on the
interviews of fishers (Yashpal et al. 2015).
This study observed 19 dead Dugongs in 12 years along the coast of Thanjavur and Pudukkottai districts, which covers only 20%
of total length of Palk Bay coast. Of
the 19 dead Dugongs recorded during this study, 17 animals were recorded only
after 2015. By comparing the Dugong
population reported by Yashpal et al. (2015) with the observations made during
this study, it is assumed that atleast 22 percentage
of Dugongs in Palk Bay might have died in 12 years between 2009–2020. The percentage may increase if the total
number of Dugong deaths are counted in remaining coastal areas of Palk Bay, or
it may decrease if the total number of dugongs in Palk Bay is more than the
estimated population by Yashpal et al. (2015).
The number of marine
mammals stranded in the area recommends establishing Dugong habitat protected
sites as conservation reserve in Palk Bay and marine mammal stranding response
units in each district, namely Nagapattinam, Tiruvarur, Thanjavur,
Pudukkottai, and Ramanathapuram. These grassroots-level units need to include
fishers and line department personnel and have to be provided with appropriate
technical training through periodical workshops on marine mammal rescue and
release and also collection of data from carcasses. The units also need to be
provided with the required equipment and infrastructure to respond to marine
mammal strandings.
Table 1. Marine mammal strandings in the northern Palk Bay from 2009 to 2020.
|
|
Date |
Common name |
Condition |
Sex |
Total length (feet) |
Season |
Nos. |
Reason for Stranding |
Place |
|
1 |
23.v.2009 |
Dugong (Dugong dugon) |
Dead |
Unknown |
9.7 |
Summer |
1 |
Highly decomposed body, reason not known |
Pudupattinam, Thanjavur
District, |
|
2 |
11.vi.2011 |
Dugong (Dugong dugon) |
Dead |
Female |
12.2 |
Pre-monsoon |
1 |
Drowning in a fishing net |
Keezhathottam, Thanjavur
District, |
|
3 |
17.iv.2010 |
Finless Porpoise (Neophocaena phocaenoides) |
Dead |
Unknown |
3.9 |
Summer |
1 |
Accidental capture in a trawl net |
Mallipattinam, Thanjavur
District |
|
4 |
22.iv.2013 |
Humpback Dolphin (Sousa chinensis) |
Dead |
Unknown |
8.4 |
Summer |
1 |
Oesophagus punctured by catfish spine |
Velivayal, Thanjavur District |
|
5 |
23.x.2015 |
Blue Whale (Balaenoptera
musculus) |
Dead |
Unknown |
45 |
Monsoon |
1 |
Unknown |
Kattumavadi, Pudukkottai District |
|
6 |
05.iv.2016 |
Dugong (Dugong
dugon) |
Dead |
Unknown |
4 |
Summer |
1 |
Drowning in a fishing net |
Ponnagaram, Pudukottai
District |
|
7 |
15.ix.2017 |
Dugong (Dugong dugon) |
Dead |
Unknown |
11 |
Monsoon |
1 |
Drowning in a fishing net |
Sethubhavachatram, Thanjavur
District |
|
8 |
01.vi.2017 |
Dugong (Dugong dugon) |
Dead |
Unknown |
- |
Pre-monsoon |
1 |
Unknown |
Velivayal |
|
9 |
21.iv.2017 |
Dugong (Dugong dugon) |
Dead |
Unknown |
10.5 |
Summer |
1 |
Drowning in gill net (kattavalai) |
Therku Pudukkudi, Pudukkotai District |
|
10 |
02.iv.2017 |
Dugong (Dugong dugon) |
Dead |
Male |
10 |
Summer |
1 |
Drowning in a fishing net |
Adaikalathevan, Thanjavur
District |
|
11 |
30.i.2017 |
Dugong (Dugong dugon) |
Live |
Female and calf |
11.5 |
Post
monsoon |
2 |
Rescued and released from Shore seine net |
Kattumavadi |
|
12 |
29.iv.2018 |
Dugong (Dugong dugon) |
Dead |
Calf |
4 |
Summer |
1 |
Without head washed ashore |
Vadakku Ammapattinam, Thanjavur District |
|
13 |
05.iv.2018 |
Dugong (Dugong dugon) |
Dead |
Female |
9.7 |
Summer |
1 |
Unknown |
Vadakku Ammapattinam |
|
14 |
06.vii.2018 |
Dugong (Dugong dugon) |
Live |
Female |
12 |
Pre-monsoon |
1 |
Rescued and released from the shore seine net |
Keezhathoddam, Thanjavur
District |
|
15 |
12.xi.2018 |
Dugong (Dugong dugon) |
Live |
Male |
9.5 |
Monsoon |
1 |
Rescued and released from the shore seine net |
Keezhathoddam, Thanjavur
District |
|
16 |
07.ii.2019 |
Dugong (Dugong dugon) |
Dead |
Male |
11 |
Post
monsoon |
1 |
Animal cut into two pieces due to unknown reasons. |
Kodimunai, Manalmelkudi, Pudukottai District |
|
17 |
02.iii.2019 |
Dugong (Dugong dugon) |
Dead |
- |
- |
Summer |
1 |
Decayed dugong body washed ashore |
Ammapattinam, Pudukkottai District |
|
18 |
03.iii.2019 |
Dugong (Dugong dugon) |
Dead |
- |
5 |
Summer |
1 |
Head was damaged by boat accident |
Ayyanpattinam, Pudukkottai District |
|
19 |
02.iv.2019 |
Dugong (Dugong dugon) |
Live |
Male and female |
10 |
Summer |
2 |
The male was rescued, and the female died while
rescue operation from the shore seine net |
Ammapattinam, Pudukottai
District |
|
20 |
16.ii.2020 |
Dugong (Dugong dugon) |
Dead |
Female |
12.8 |
Summer |
1 |
Drowning in a fishing net |
Sethubavachatthiram, Thanjavur
District |
|
21 |
16.x.2020 |
Finless Porpoise (Neophocaena phocaenoides) |
Dead |
- |
4 |
Monsoon |
1 |
Accidental capture in fishing net. |
Mallipattinam, Thanjavur
District |
For
figure & images - - click here
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