Their slow reproduction rate (averagely one pup every 4-5 years) means it is difficult for the species to recover from the ‘Vulnerable’ and ‘Endangered’ IUCN statuses, and with their habitats and food sources steeply declining due to climate change, the need for better protection has never been more needed.Oceanic Manta Ray (Mobula birostris) Mantas in Fiji Discarded marine gear also opposes a threat as the gear gets tangled around their cephalic lobes and fins. Unfortunately, the commercial fishing industry poses a big threat to manta rays, as they are not only often targeted for their gills and dorsal fins to be sold in international trade, but also caught as by-catch of big fishing vessels. The species also control plankton abundance and diversity and therefore act as an important connection between the deep sea and shallower water columns of the ocean. The faeces contain nutrients not found in coral reefs surroundings, which help corals grow. As they travel regularly between the deep ocean and coral reefs, the waste they accumulate while feeding on zooplankton acts as a fertiliser on the reef.
Manta rays’ feeding behaviour makes them one of the key species for the reef health. In February 2021 we saw a massive aggregation of giant mantas deep in the Canyon feeding on a plankton front, where more than 30 individual were seen in a single day. We have sighted both species at various cleaning stations in the region during dives. 3-Trees, 9-mile, and 2-mile reefs), but giant manta rays are rare, as they spend most of their time in deeper waters. Reef manta rays are encountered regularly during scuba dives in other parts of the archipelago (e.g. Our surface-sighting records show that manta rays predominantly occur in two areas: south of the Bazaruto Archipelago on the east side of Magarruque Island and near the Canyon (see below), as well as off the north side of Bazaruto Island. It is during this period that we see more manta rays in the Bazaruto Archipelago and surroundings. After the arrival of phytoplankton, zooplankton typically follows as zooplankton feeds on phytoplankton. The colder water contains high quantities of nutrients, which combined with sunlight warms up and may trigger phytoplankton blooms. Strong and sudden Mozambique Channel wind reversals trigger upwelling of colder water (water being pushed up from the deeper ocean to shallower water columns) resulting in higher density of plankton: the primary food source of both reef manta rays (M.
Manta ray season in the Mozambique Channel starts around February, when seawater temperatures drop from the peaks of the summer, and large amounts of plankton are trapped in fronts and eddies as well as after upwelling events. Being pelagic, giant manta rays travel further than reef manta rays, as they embark on ocean crossings, covering the Pacific, Atlantic and Indian Ocean, where the reef manta ray is only found in the Indian ocean and part of the Pacific Ocean and usually keeps to smaller, coastal areas throughout their lives, for example the Bazaruto Archipelago. Reef manta rays are found globally in (sub)tropical waters, whereas oceanic manta rays are found in both (sub)tropical and temperature ocean waters. Other differences between the manta ray species are the fact that there are no spots in between the gills of giant manta rays and the dark edges at the end of the bottom of their fins. The two species look very similar, however, reef manta rays are typically 3 to 3.5 meter in disc width ( the largest reef manta rays have been found in Mozambique, sizing up to 5m in disc width), while giant oceanic manta rays can impressively reach up to 9 meters in size. Though, only in 2008 scientists discovered that there are two species of manta ray, not one. Research has proven that manta rays can recognise themselves in the mirror, which is considered a high cognitive function. Manta rays have sparked the interest of scientists globally for decades, for one because the species have the biggest brain-to-size ratio of any fish, indicating high intelligence.
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