26 research outputs found
Yellow-banded Mangrove Snakes (Cantoria violacea) consume hard-shelled Orange Signaler Crabs (Metaplax elegans)
Catch composition and life history characteristics of sharks and rays (Elasmobranchii) landed in the Andaman and Nicobar Islands, India
Detailed information on shark and ray fisheries in the Andaman and Nicobar Islands, India are limited, including information on the diversity and biological characteristics of these species. We carried out fish landing surveys in South Andamans from January 2017 to May 2018, a comprehensive and cost-effective way to fill this data gap. We sampled 5,742 individuals representing 57 shark and ray species landed from six types of fishing gears. Of the 36 species of sharks and 21 species of rays landed, six species of sharks (Loxodon macrorhinus, Carcharhinus amblyrhynchos, Sphyrna lewini, C. albimarginatus, C. brevipinna, and Paragaleus randalli) comprised 83.35% of shark landings, while three species of rays (Pateobatis jenkinsii, Himantura leoparda and H. tutul) comprised 48.82% of ray landings, suggesting a species dominance in the catch or fishing region. We provide insights into the biology of species with extensions in maximum size for seven shark species. Additionally, we document an increase in the known ray diversity for the islands and for India with three previously unreported ray species. We found that amongst sharks, mature individuals of small-bodied species (63.48% males of total landings of species less than 1.5 m total length when mature) and immature individuals of larger species (84.79% males of total landings of species larger than 1.5 m total length when mature) were mostly landed; whereas for rays, mature individuals were predominantly landed (80.71% males of total landings) likely reflecting differences in habitat preferences along life-history stages across species and fishing gear. The largest size range in sharks was recorded in landings from pelagic longlines and gillnets. Further, the study emphasizes the overlap between critical habitats and fishing grounds, where immature sharks and gravid females were landed in large quantities which might be unsustainable in the long-term. Landings were female-biased in C. amblyrhynchos, S. lewini and P. jenkinsii, and male-biased in L. macrorhinus and H. leoparda, indicating either spatio-temporal or gear-specific sexual segregation in these species. Understanding seasonal and biological variability in the shark and ray landings over a longer study period across different fisheries will inform future conservation and fishery management measures for these species in the Andaman and Nicobar Islands
Highly Variable Taxa-specific Coral Bleaching Responses to Thermal Stresses
Complex histories of chronic and acute sea surface temperature (SST) stresses are expected to trigger taxon- and location-specific responses that will ultimately lead to novel coral communities. The 2016 El Niño-Southern Oscillation provided an opportunity to examine large- scale and recent environmental histories on emerging patterns in 226 coral communities distrib- uted across 12 countries from East Africa to Fiji. Six main coral communities were identified that largely varied across a gradient of Acropora to massive Porites dominance. Bleaching intensity was taxon-specific and was associated with complex interactions among the 20 environmental variables that we examined. Coral community structure was better aligned with the historical temperature patterns between 1985 and 2015 than the 2016 extreme temperature event. Addi- tionally, bleaching responses observed during 2016 differed from historical reports during past warm years. Consequently, coral communities present in 2016 are likely to have been reorganized by both long-term community change and acclimation mechanisms. For example, less disturbed sites with cooler baseline temperatures, higher mean historical SST background variability, and infrequent extreme warm temperature stresses were associated with Acropora-dominated communities, while more disturbed sites with lower historical SST background variability and frequent acute warm stress were dominated by stress-resistant massive Porites corals. Overall, the combination of taxon-specific responses, community-level reorganization over time, geographic variation, and multiple environmental stressors suggest complex responses and a diversity of future coral communities that can help contextualize management priorities and activities
Large Geographic Variability in the Resistance of Corals to Thermal Stress
Aim: Predictions for the future of coral reefs are largely based on thermal exposure and poorly account for potential geographic variation in biological sensitivity to ther- mal stress. Without accounting for complex sensitivity responses, simple climate ex- posure models and associated predictions may lead to poor estimates of future coral survival and lead to policies that fail to identify and implement the most appropri- ate interventions. To begin filling this gap, we evaluated a number of attributes of coral taxa and communities that are predicted to influence coral resistance to thermal stress over a large geographic range.
Location: Western Indo-Pacific and Central Indo-Pacific Ocean Realms.
Major taxa studied: Zooxanthellate Scleractinia – hard corals.
Methods: We evaluated the geographic variability of coral resistance to thermal stress as the ratio of thermal exposure and sensitivity in 12 countries during the 2016 global-bleaching event. Thermal exposure was estimated by two metrics: (a) histori- cal excess summer heat (cumulative thermal anomaly, CTA), and (b) a multivariate index of sea-surface temperature (SST), light, and water flow (climate exposure, CE). Sensitivity was estimated for 226 sites using coordinated bleaching observations and underwater surveys of coral communities. We then evaluated coral resistance to ther- mal stress using 48 generalized linear mixed models (GLMMs) to compare the poten- tial influences of geography, historical SST variation, coral cover and coral richness.
Results: Geographic faunal provinces and ecoregions were the strongest predic- tors of coral resistance to thermal stress, with sites in the Australian, Indonesian and Fiji-Caroline Islands coral provinces having higher resistance to thermal stress than Africa-India and Japan-Vietnam provinces. Ecoregions also showed strong gradients in resistance with highest resistance to thermal stress in the western Pacific and Coral Triangle and lower resistance in the surrounding ecoregions. A more detailed evaluation of Coral Triangle and non-Coral Triangle sites found higher resistance to thermal stress within the Coral Triangle, associated with c. 2.5 times more recent historical thermal anomalies and more centralized, warmer, and cool-water skew SST distributions, than in non-Coral Triangle sites. Our findings identify the importance of environmental history and geographic context in future predictions of bleaching, and identify some potential drivers of coral resistance to thermal stress.
Main conclusions: Simple threshold models of heat stress and coral acclimation are commonly used to predict the future of coral reefs. Here and elsewhere we show that large-scale responses of coral communities to heat stress are geographically variable and associated with differential environmental stresses and histories
Elasmobranch conservation, challenges and management strategy in India: recommendations from a national consultative meeting
Historically, India has been projected as one of the major elasmobranch fishing nations in the world. However, management and conservation efforts are not commensurate with this trend. Along with the Wildlife (Protection) Act, 1972, several generic conservation measures are in place at the regional/local level. But India is still a long way from meeting global conservation commitments. We present here the status of elasmobranch management and conservation in India, with the specific objec-tive of identifying the gaps in the existing set-up. We also present recommendations based on a national consultative workshop held at the Central Marine Fisheries Research Institute, Kochi, in February 2020. We recommend the implementation of a National Plan of Action (NPOA-Sharks) and more in-clusive governance and policymaking for elasmobranch conservation in India
Seagrass Herbivory Levels Sustain Site- Fidelity in a Remnant Dugong Population
17 páginas, 5 figuras, 5 tablasHerds of dugong, a largely tropical marine megaherbivore, are known to undertake long-distance
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 species.
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 perhaps
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.This work was supported by Ravi Sankaran Inlaks Fellowship Program, to ED; Mohammed Bin Zayed Species Conservation Fund, to ED; Ministry of
Environment and Forests, CSIC under the PIE programme (Ref: 201330E062), to TAPeer reviewe
For traditional island communities in the Nicobar archipelago, complete no-go areas are the most effective form of marine management
11 páginas, 6 figuras, 3 tablas.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 effectiveness
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 results
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.We thank Wildlife Conservation Society; Research Fellowship Program (RFP) and Rufford Small grant for Nature Conservation
(RSG), (Refernce no. 60.09.09) for providing financial support to
carry out fieldwork.Peer reviewe
Erosion of Traditional Marine Management Systems in the Face of Disturbances in the Nicobar Archipelago
11 páginas, 3 tablas, 2 figurasTo sustainably manage naturally scarce resources,
island communities often evolve complex mechanisms including
customary laws, belief systems, and reciprocity arrangements
among others, to prevent overharvest. Their effectiveness
depends largely on the extent to which resource users
comply with the rules. We examined patterns of compliance
with traditional marine management in the Nicobar
Archipelago, India, before, and six years after, the 2004 tsunami.
We used interview-based surveys to document marine
harvest regulations, and changes in compliance patterns. Our
results indicate that pre-tsunami, complex harvest rules
existed, including spatio-temporal closures, gear restrictions
and species bans; many reefs were subject to multiple, overlapping
restrictions. Post-tsunami, compliance weakened considerably;
younger individuals (19–35 years) and individuals
receiving tsunami aid (boats, gear, etc.) were the most likely
non-compliers. Around 84 % of interviewees attributed declining
compliance directly to post-tsunami changes in resource
availability and a perceived decline in traditional authority.
Changes in resource availability can interact strongly
with institutional decline, eroding the resilience of traditional
management.Peer reviewe
Occurrence and distribution of tetraodontiform fishes of the Andaman and Nicobar Islands, India
Some fish groups are common on coral reefs, but we still lack fundamental information about how fish assemblages vary across seascapes. The order Tetraodontiformes, which includes pufferfish, triggerfish, shingles, porcupinefish, burrfish, leatherjacketfish, filefish, and trunkfish, is one such group. We systematically surveyed 75 sites around 52 islands of the Andaman and Nicobar archipelago to evaluate the occurrence and distribution of tetraodontiform fishes. We recorded 25 species from 16 genera and 6 families. We found the distribution of fishes to vary between sites and geographical regions, with the southern Nicobar region having higher species richness than other geographical regions in the island group. Possible reasons for the observed patterns of the occurrence and distribution of tetraodontiform fishes are discussed
Effect of dugong herbivory on the shoot density of <i>Halophila ovalis</i>.
<p>Shoot densities were measured inside and outside experimental exclosures at the start of the experiment (T0) and 4 months later (T1). Error bars are standard errors.</p