Research Associate, Oceans and Coasts
Elrika D'Souza has been working on the ecology and conservation of dugongs in the Andaman and Nicobar Islands for several years. Her recently completed doctoral thesis documented historical declines in dugong populations in the islands and attempted to identify the factors that led to this decline. Her work also explores the relationship between dugongs and the seagrass meadows they depend on. She is currently working on a joint project with NCF and the A&N Forest Department to develop conservation strategies for the dugong within these archipelagos.
- Journal Article2017Latitude and live coral cover independently affect butterflyfish & angelfish community distribution in the Andaman & Nicobar archipelago, IndiaMarine Biodiversity. DOI 10.1007/s12526-017-0790-4Download
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Latitude and live coral cover independently affect Chaetodontid and Pomacanthid fish community distribution in the Andaman and Nicobar archipelago, India
Empirical evidence indicates that for two reef fish groups, chaetodontids and pomacanthids, live coral cover and latitude determine the local abundance and species richness patterns. Most studies have considered the influence of either live coral cover or latitude in isolation, and the interactive effects that are likely to influence the geographical distribution of species richness and diversity has not been explored. In this study we explored the relationship between (1) species richness and latitude, and (2) species richness and benthic variables, (3) species diversity and latitude and (4) species diversity and benthic variables for butterflyfish (Chaetodontidae) and angelfish (Pomacanthidae) at 75 sites across 51 islands in the Andaman and Nicobar (A & N) archipelago. A total of 30 species of chaetodontids belonging to four genera and 13 species of pomacanthids belonging to nine genera were recorded. We found that live coral cover and latitude were the best predictors for explaining variation in the distribution of these fish communities across the A & N archipelago. This is probably because of the high dependence of these two fish groups on the live coral cover and Nicobar’s geographical proximity to the Coral Triangle, which is considered to be the centre of origin of coral reefs and supports high biodiversity. Our results show that de- spite the high dependence of chaetodontids and pomacanthids on live coral cover, reduction of live coral cover due to a series of disturbance events had limited influence on species richness of these two fish groups, indicating that broad geographical trends are important in explaining variation in species richness for chaetodontid and pomacanthid fish groups.
- Journal Article2016For traditional island communities in the Nicobar archipelago, complete no-go areas are the most effective form of marine managementFor traditional island communities, no-go areas are the most effective form of managementOcean & Coastal Management 133, 53-63 http://dx.doi.org/10.1016/j.ocecoaman.2016.09.003Download
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For traditional island communities in the Nicobar archipelago, complete no-go areas are the most effective form of marine management
The ability of local communities to sustainably manage natural resource harvests in coral reefs ecosystem depends heavily on the strength of traditional institutions. Coastal communities have evolved a suite of restrictive practices to control marine offtake and there is considerable recent evidence of their effec- tiveness in protecting and enhancing resource stocks. However, traditionally imposed restrictions can vary considerably in their complexity and in their functional effectiveness. The indigenous communities of the Nicobar Islands are dependent on marine resources for sustenance, managing them with a range of traditionally imposed restrictions. These include limited entry to certain locations, closed seasons and areas, and restrictions on species, size-classes of fish and fishing methods. We tested the relative effectiveness of protection in areas managed under different traditional control regimes by comparing the abundance and biomass of targeted fish groups in managed and unmanaged areas. Our results indicate that reef sites with the strictest form of restriction e essentially no-go areas e had significantly higher abundance and biomass values of most functional groups of fishes compared with partially protected and control locations. In contrast, targeted food fish stocks did not differ from control locations in partially protected sites managed with even complex forms of traditional management. Ensuring that traditional harvest rules are complied is critical to the success of any management system, and our re- sults suggest that they can be most strictly enforced in traditional no-go areas. Our work highlights the importance of critically evaluating the factors influencing traditional management systems to strengthen their ability to protect these reefs from unsustainable overharvest.
- Journal Article2015Seagrass Herbivory Levels Sustain Site-Fidelity in a Remnant Dugong PopulationSeagrass Herbivory Levels Sustain Site- Fidelity in a Remnant Dugong PopulationPLoS ONE 10(10): e0141224. doi:10.1371/journal.pone.0141224Download
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Seagrass Herbivory Levels Sustain Site-Fidelity in a Remnant Dugong Population
Herds of dugong, a largely tropical marine megaherbivore, are known to undertake long-dis- tance movements, sequentially overgrazing seagrass meadows in their path. Given their drastic declines in many regions, it is unclear whether at lower densities, their grazing is less intense, reducing their need to travel between meadows. We studied the effect of the feeding behaviour of a small dugong population in the Andaman and Nicobar archipelago, India to understand how small isolated populations graze seagrasses. In the seven years of our observation, all recorded dugongs travelled either solitarily or in pairs, and their use of seagrasses was limited to 8 meadows, some of which were persistently grazed. These meadows were relatively large, contiguous and dominated by short-lived seagrasses spe- cies. Dugongs consumed approximately 15% of meadow primary production, but there was a large variation (3–40% of total meadow production) in consumption patterns between meadows. The impact of herbivory was relatively high, with shoot densities c. 50% higher inside herbivore exclosures than in areas exposed to repeated grazing. Our results indicate that dugongs in the study area repeatedly graze the same meadows probably because the proportion of primary production consumed reduces shoot density to levels that are still above values that can trigger meadow abandonment. This ability of seagrasses to cope per- haps explains the long-term site fidelity shown by individual dugongs in these meadows. The fact that seagrass meadows in the archipelago are able to support dugong foraging requirements allows us to clearly identify locations where this remnant population persists, and where urgent management efforts can be directed.
- Popular Article2015A day to celebrate the dugong-a story of their conservationAndaman Chronicle, 04, October
- Journal Article2015Erosion of Traditional Marine Management Systems in the Face of Disturbances in the Nicobar ArchipelagoHuman Ecology, DOI 10.1007/s10745-015-9781-x
- Popular Article2015Marine Meadows – Following The Feeding Trail Of The DugongSanctuary Asia, Vol. XXXV No. 1, February 2015.
- Popular Article2014The Constant GardnerCurrent Conservation, Issue 8.2, http://www.currentconservation.org/?q=articles/feature&n=297
- Newsletter2013Protecting the dugong: Better late than neverSpecial bulletin of the 59th Wildlife Week Booklet Department of Environment and Forests, Andaman and Nicobar Administration, September issue.
- Newsletter2013Where have all the dugongs gone? A study on long-term occupancy trends in the Andaman and Nicobar archipelago, India,Sirenews, Newsletter of the IUCN Sirenia Specialist Group, Vol. 60.
- Journal Article2013Long-Term occupancy trends in a data-poor dugong population in the Andaman and Nicobar ArchipelagoPLoS One. 8(10): e76181
Prioritizing efforts for conserving rare and threatened species with limited past data and lacking population estimates is predicated on robust assessments of their occupancy rates. This is particularly challenging for elusive, long-lived and wide- ranging marine mammals. In this paper we estimate trends in long-term (over 50 years) occupancy, persistence and extinction of a vulnerable and data-poor dugong (Dugong dugon) population across multiple seagrass meadows in the Andaman and Nicobar archipelago (India). For this we use hierarchical Bayesian dynamic occupancy models accounting for false negatives (detection probability,1), persistence and extinction, to two datasets: a) fragmentary long-term occurrence records from multiple sources (1959–2004, n = 40 locations), and b) systematic detection/non-detection data from current surveys (2010–2012, n = 57). Dugong occupancy across the archipelago declined by 60% (from 0.45 to 0.18) over the last 20 years and present distribution was largely restricted to sheltered bays and channels with seagrass meadows dominated by Halophila and Halodule sp. Dugongs were not found in patchy meadows with low seagrass cover. In general, seagrass habitat availability was not limiting for dugong occupancy, suggesting that anthropogenic factors such as entanglement in gillnets and direct hunting may have led to local extinction of dugongs from locations where extensive seagrass meadows still thrive. Effective management of these remnant dugong populations will require a multi-pronged approach, involving 1) protection of areas where dugongs still persist, 2) monitoring of seagrass habitats that dugongs could recolonize, 3) reducing gillnet use in areas used by dugongs, and 4) engaging with indigenous/settler communities to reduce impacts of hunting.