Seasonal distribution, movements and taxonomic status of bluewhales (Balaenoptera musculus) in the northern Indian Ocean

Seasonal distribution, movements and taxonomic status of bluewhales (Balaenoptera musculus) in the northern Indian Ocean

Year of publication 2013

Product type Document

Edition 1

Synopsis (short abstract) There is a distinct population of blue whales, Balaenoptera musculus, in the northern Indian Ocean. The taxonomic status of these animals has long been uncertain, with debate over whether this population represents a distinct subspecies, and if so which me should apply. They have most frequently been assigned to B. musculus brevicauda, but are currently considered to be B. m. indica. The movements of these blue whales within the northern Indian Ocean are poorly understood. This paper reviews cat ches (n = 1,288), sightings (n = 448, with a minimum of 783 animals), strandings (n = 64) and acoustic detections (n = 6 locations); uses ocean colour data to estimate seasolity of primary productivity in different areas of the northern Indian Ocean; and develops a migration hypothesis. It is suggested that most of these whales feed in the Arabian Sea off the coasts of Somalia and the Arabian peninsula during the period of intense upwelling associated with the southwest monsoon (from about May t o October). At the same time some blue whales also feed in the area of upwelling off the southwest coast of India and west coast of Sri Lanka. When the southwest monsoon dies down in about October–November these upwellings cease. The blue whales then disperse more widely to eke out the leaner months of the northeast monsoon (during about December to March) in other localised areas with seasolly high productivity. These include the east coast of Sri Lanka, the waters west of the Maldives, the vic inity of the Indus Canyon (at least historically), and some parts of the southern Indian Ocean. The data are consistent with the hypothesis that at least some of the blue whales that feed off the east coast of Sri Lanka in the northeast monsoon also feed in the Arabian Sea during the southwest monsoon. These whales appear to migrate eastwards past the north of Maldives and south of Sri Lanka in about December–January, returning westwards in about April–May.

Meeting Session Number 9

Language English

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Summary report on cruise of the R/V Shoyo Maru in the north Arabian Sea, 2 October 1976 - 13 January 1977 1977

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At the Fifth session of the IOFC Executive Committee held in Rome in April 1976, the Indian Ocean Programme reported its success in bringing the R/V Shoyo Maru to the Arabian Sea and adjacent waters off India and Pakistan in November and December 1976. The present paper gives a brief description of the survey and its results, summarized from the original report in Japanese which will be published by the Fishery Agency of Japan in 1977. The activities covered oceanographic observation, convention al biological survey (sighting of pelagic shoals and collection of fishes) and acoustic survey. In spite of special attention, the squid Sympleototeuthis oualaniensis did not appear abundantly during the present cruise. The equatorial undercurrent did not exist in the equatorial waters during the transitional period, from the southwest monsoon to the northeast monsoon. Although the upwelling was recognized in the western part of the Second Area in the 1975 cruise, this was not encountered in the 1976 cruise. This might be attributed to the difference in the survey period; the first cruise in 1975 covered the late southwest monsoon season while the present cruise the early northeast monsoon season. The coastal upwelling on the continental slope was evidently less remarkable during the present cruise than during the previous one. The pelagic shoals again appeared rather scarce in the offshore waters throughout the survey period as was the previous cruise. There was a considerable number of important commercial fishes, almost the same species of the previous survey, on the Pakistani continental shelf, but none of them appeared to be large enough to attract a large-scale operation. In the present survey, the squids were not caught as often as in the previous survey. The index of echo abundance in the Second Area in 1976 was half of that in 1975. Since the duration of our cruise was very limited, it was difficult to find any reasoning for such year-to-year variation. However, it might be suggested that the squids moved toward the west coast of India or the southern Arabian Peninsula, or a deeper layer during the northeast monsoon season.
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Post nesting migration of green turtle (Chelonia mydas) in the western Indian Ocean 2013

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Marine turtles do not recognize political boundaries, nor do they have regard for Exclusive Economic Zones (EEZ s), cooperative agreements, intertiol conventions, or memoranda of understanding between countries. So is it in the Southwest Indian Ocean (SWIO), a region that hosts some of the most important green turtle nesting sites in the world, most of which are isolated on remote islands (e.g. Europa and Glorieuses, Aldabra and Cosmoledo, Moheli and Mayotte). This region of the world is known t o have year round nesting of green turtles but all sites display a marked nesting season. However, very little is known about migratory pathways that sea turtles ply between their nesting and feeding grounds in this region where this species faces numerous threats such as fisheries interaction at both open sea and coastal waters. From 2009 to 2011, we deployed 81 satellite transmitters on nesting green turtle females during (d) and opposite (o) to the nesting peak in 5 important rookeries of the South West Indian Ocean (SWIO): Europa (Nd=10; No=10), Glorieuses (Nd= 10; No=10), Tromelin (Nd= 10; No=10), Mayotte (Nd=10; No=10) and Mohéli (Nd=7; No=3) and collected previous 24 old tracks in the area for a total of 105 tracks. First results showed that 39.7% of the tracked turtles used Madagascar costal foraging ground while more than 50% used the east African ones (Mozambique (32,0%), Kenya (3.8%), Tanzania (15,4%) and Somalia (2,5%)). It is worthwhile noting that the North Mozambique and South Tanzania remain the most important foraging ground for the tracked turtle (45% of the tracked turtles), but that they are mainly used by turtles tagged during the nesting season. On the other hand, we highlight here that green turtles also use a large range of foraging ground in the area (55% of the tagged turtles), some of them being hot spots (e.g. south of Maputo – Mozambique, Tulear lagoon – Madagascar). Spatial distribution estimation allowed identifying important year round coastal and oceanic migrating corridors: 2 oceanic corridors, (1) in the north of the Mozambique Channel (11°S - 14°S) and (2) the south of the Mozambique Chanel (17°S - 23°S), more particularly from the north of Europa to the north of Mozambique (38°E - 41°E); and 2 coastal corridors (1) The east African coast, between 16°S (Mozambique) and 7°S (Tanzania), and (2) all the west coast of Madagascar. The extreme north of Madagascar is also an important coastal migratory corridor The 105 tracked green turt les also crossed as many as nine different EEZs in the region before reaching their foraging grounds, which themselves are shared by six countries. Such spatial migrating pattern of adult green turtle, the temporal corridors and the regiol feeding hot spots identified are of high importance to implement targeted mitigating measures for artisal and industrial fisheries and encourage conservation on key foraging grounds.
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Outline of climate and oceanographic conditions in the Indian Ocean in the recent years: an update to August 2013 2013

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In this paper, we provide an update on the trends of climate and oceanographic conditions in the Indian Ocean and in sub-regions (Somali basin, East and West Equatorial areas, Mozambique Channel and Maldives). The ENSO cycle has been largely fluctuating between ENSO-neutral and Niña conditions during the past 4 years. Positive sea surface temperature (SST) anomalies have prevailed since the early 2000 over the West Indian Ocean (WIO). Substantial deepening of the thermocline occurs in the WIO in relation with intense El Niño events, but the opposite response (shoaling) during La Niña events is not clear on the long term. Since 2008, SOI has shown predomintly positive values (Niña) and thermocline has shoaled without major disruption along this trend until April 2011. Chlorophyll (SSC) has shown a declining trend over 2006-2010, followed by a slight increase from October 2010 to May 2011 in association with a Niña event, then continued to decline until March 2013. Then, the trend revers ed and positive anomalies developed from May 2013 onwards. Highly positive SSC anomalies were found in July-September 2013 in the Somali basin (40% above normal), suggesting an intensification of the Somali upwelling. In other areas, SSC was about the average in 2013 (Mozambique Channel, Maldives) or still slightly negative (10 % below normal) in the West equatorial (December 2012 to February 2013) and East equatorial areas. The overall chlorophyll- depleted conditions for 2006-2012 (except 2011 ) in the WIO, when the thermocline was shoaling, is unclear as we might have expected a positive chlorophyll response to an increased supply of nutrients in the photic layer associated with shallow thermocline. The skipjack purse seine CPUEs on associated sets, in the Somali basin during July-September, are distributed in chlorophyll-enriched areas resulting from the upwelling. In 2010-2012, the position of the 0.4 mg.m-3 isoline of chlorophyll concentration delineated the eastward boundary of t he skipjack CPUEs.

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