Cetacean Diversity and Mixed-Species Associations off Southern Sri Lanka

March 8-9, 2011, BANGKOK, THAILANDSri Lanka, in the northern Indian Ocean island, has a relatively narrow continental shelf and an abundance of cetacean fauna in her waters. A few vessel surveys have produced data on cetacean occurrence off the east and west coast but no similar data exists for the south. To fill this data gap vessel-based transects were carried out in 2008/2009 off a selected segment of the south coast. A high sighting rate was recorded and nine species were documented: Balaenoptera musculus, Balaenoptera brydei, Physeter macrocephalus, Stenella longirostris, Tursiops truncates, Pseudorca crassidens, Feresa attenuata, Orcinus orca and Globicephala macrorhynchus. Significantly the first scientifically documented sighting of O. orca anywhere in Sri Lanka's waters was recorded. Additionally blue whale feeding aggregations including mother-calf pairs were documented off southern Sri Lanka in the Austral summer. Mixed species associations involving five species of cetaceans were also recorded. The coastal waters off southern Sri Lanka are therefore an important cetacean habitat with high diversity and mixing of coastal and usually pelagic species. The implications of the importance of the area for blue whales also warrants further study and more detailed studies are recommended to generate data that can inform future management and conservation decisions

Cetacean bycatch in Indian Ocean tuna gillnet fisheries

Pelagic gillnet (driftnet) fisheries account for some 34% of Indian Ocean tuna catches. We combined published results from 10 bycatch sampling programmes (1981−2016) in Australia, Sri Lanka, India and Pakistan to estimate bycatch rates for cetaceans across all Indian Ocean tuna gillnet fisheries. Estimated cetacean bycatch peaked at almost 100 000 ind. yr−1 during 2004−2006, but has declined by over 15% since then, despite an increase in tuna gillnet fishing effort. These fisheries caught an estimated cumulative total of 4.1 million small cetaceans between 1950 and 2018. These bycatch estimates take little or no account of cetaceans caught by gillnet but not landed, of delayed mortality or sub-lethal impacts on cetaceans (especially whales) that escape from gillnets, of mortality associated with ghost nets, of harpoon catches made from gillnetters, or of mortality from other tuna fisheries. Total cetacean mortality from Indian Ocean tuna fisheries may therefore be substantially higher than estimated here. Declining cetacean bycatch rates suggest that such levels of mortality are not sustainable. Indeed, mean small cetacean abundance may currently be 13% of pre-fishery levels. None of these estimates are precise, but they do demonstrate the likely order of magnitude of the issue. Countries with the largest current gillnet catches of tuna, and thus the ones likely to have the largest cetacean bycatch are (in order): Iran, Indonesia, India, Sri Lanka, Pakistan, Oman, Yemen, UAE and Tanzania. These 9 countries together may account for roughly 96% of all cetacean bycatch from tuna gillnet fisheries across the Indian Ocean

Cetacean bycatch in Indian Ocean tuna gillnet fisheries

Pelagic gillnet (driftnet) fisheries account for some 34% of Indian Ocean tuna catches. We combined published results from 10 bycatch sampling programmes (1981−2016) in Australia, Sri Lanka, India and Pakistan to estimate bycatch rates for cetaceans across all Indian Ocean tuna gillnet fisheries. Estimated cetacean bycatch peaked at almost 100 000 ind. yr−1 during 2004−2006, but has declined by over 15% since then, despite an increase in tuna gillnet fishing effort. These fisheries caught an estimated cumulative total of 4.1 million small cetaceans between 1950 and 2018. These bycatch estimates take little or no account of cetaceans caught by gillnet but not landed, of delayed mortality or sub-lethal impacts on cetaceans (especially whales) that escape from gillnets, of mortality associated with ghost nets, of harpoon catches made from gillnetters, or of mortality from other tuna fisheries. Total cetacean mortality from Indian Ocean tuna fisheries may therefore be substantially higher than estimated here. Declining cetacean bycatch rates suggest that such levels of mortality are not sustainable. Indeed, mean small cetacean abundance may currently be 13% of pre-fishery levels. None of these estimates are precise, but they do demonstrate the likely order of magnitude of the issue. Countries with the largest current gillnet catches of tuna, and thus the ones likely to have the largest cetacean bycatch are (in order): Iran, Indonesia, India, Sri Lanka, Pakistan, Oman, Yemen, UAE and Tanzania. These 9 countries together may account for roughly 96% of all cetacean bycatch from tuna gillnet fisheries across the Indian Ocean

Impacts of Whale-Watching on Blue Whales (Balaenoptera musculus) off Southern Sri Lanka

February 20-21, 2012, BANGKOK, THAILANDBlue whales inhabit the coastal waters off southern Sri Lanka throughout the year, due to a narrow continental shelf and upwelling, related feeding opportunities. A busy, international shipping lane also lies off the south coast. While blue whales are listed on the IUCN Red List of Threatened Species, the subspecies status and genetic affinities of this northern Indian Ocean population is not well understood. Since 2009 a rapidly expanding, boat-based, commercial whale-watching industry has developed off the south coast, but remains unregulated due to the non-existence of national regulations or codes of conduct. As a result, unethical practices are leading to harassment of the targeted whales. Comparison of sightings data from before and after whale-watching began, shows a shift in the area of occurrence and concentration of whales. Simultaneously there is an increase in the number of stranding and vessel collision related mortality. These factors indicate that current whalewatching practices are displacing whales from their preferred feeding areas and inadvertently pushing them offshore into the shipping lane, causing an increase in fatal vessel collisions. It is recommended that a precautionary principal is followed and whale-watching activities are regulated as a priority, in order to mitigate any adverse impacts

Dugong Conservation a Critical Issue in Sri Lanka

March 8-9, 2011, BANGKOK, THAILANDThe dugong (Dugong dugon) was traditionally hunted and considered a delicacy in Sri Lanka. Dugongs were common in the Gulf of Mannar (north-west coast) and were the focus of a targeted fishery till the mid-20th century. Overexploitation caused this population to decline rapidly and recognising this, the Sri Lankan Government declared the dugong a protected species in 1970. Legal protection was however not followed by effective law enforcement and recent surveys indicate that illegal harvesting still continues. Due to an unstable security situation the remaining dugong habitat was inaccessible to researchers till 2009 and no censuses were carried out, while illegal capture went largely undetected and unreported. While the area is now accessible population assessments and threat mitigation in the form of proactive conservation measures are a matter of urgent priority. While research is essential to develop informed conservation measures such activities need to be implemented in a manner that is sensitive to local socioeconomic circumstances. Protection of endangered species is not yet considered a priority among impoverished coastal communities. Therefore these issues need urgent and innovative attention to provide this dugong population with a chance of survival and prevent imminent local extirpation

A review of cetacean research and conservation in Sri Lanka

Sri Lanka is a developing island nation in the northern Indian Ocean. Travellers and historians have documented whales in the waters around the island as far back as the 14th century but the first scientific records of live cetaceans from vessel-based research observations were documented only in the early 1980s. Sri Lanka’s waters have high cetacean species richness with 27 species recorded to date and year-round abundance. Small cetaceans are however increasingly threatened due to the developing fisheries industry, with bycatch being a major cause for concern. Other identified threats include increasing shipping traffic and unregulated marine tourism. Cetaceans are protected by national legislation but implementation of the relevant laws and conservation measures is hampered by resource constraints. The prevailing gaps in knowledge are also due to a lack of resources to carry out dedicated long-term research on cetaceans in a developing country with more immediate human development priorities. Therefore strengthened law enforcement and finding adequate resources for sustained systematic research that can inform management decisions are priorities in Sri Lanka.</jats:p

The need for taxonomic investigations on Northern Indian Ocean blue whales (Balaenoptera musculus): implications of year-round occurrence off Sri Lanka and India

The blue whale (Balaenoptera musculus) is one of the most common cetaceans in the waters around Sri Lanka and in a worldwide context one of the highest low-latitude sighting rates for this species has been recorded in these waters. As genetic analyses, acoustic studies and even long-term sighting surveys for blue whales in these waters are limited, the taxonomic status and population affinities of these animals are not definitively known at present. Sighting records of this species were examined from the waters around Sri Lanka and stranding records from the coasts of both Sri Lanka and India in terms of seasonality of occurrence and it was found that the species is clearly present in these waters throughout the year. This, together with secondary data on certain morphological characteristics and behavioural anomalies, indicates that these waters are ecologically important to blue whales in the Northern Indian Ocean and questions are raised regarding the subspecific identity and population affinities of the animals in the region. It is not clear if they belong to either of the two subspecies currently recognised for the Southern Ocean and Indian Ocean region: their apparently non-migratory nature is akin to the pygmy blue whale B.m. brevicauda, while some morphological and behavioural characteristics are indicative of Antarctic blue whales of the subspecies B.m. intermedia. This raises the possibility of an entirely different or intermediate subspecies and the need to re-examine B.m. indica as a third subspecies in the Northern Indian Ocean. As clarifying their taxonomic status is important in the context of conservation and management, multi-disciplinary studies are urgently needed.</jats:p