On Whales and their Usefulness N°1 April 2010 On Whales and their Usefulness Summary Introduction ……………………………………………………………………………………………... 3 I – Stage 1……………………………………………………………………………………………….. 5 Amphipods, sharks, hagfish, black seasnail, grenadiers, sablefish padgy cuskeel II – Stage 2……………………………………………………………………………………….…… 10 Sea cucumbers, annelids, osedax, crabs. III – Stage 3…………………..……………………………………………………………………...... 13 Sulphophilic period IV – Stage 4……………………………………………………………………………………….….. 14 The reef Conclusions……………………………………………………………………………………………… 14 Recommandations …………………………………………………………………………………… 14 Map:……………………………………………………………………………………………………... 15 Inventory of studied whale remain sights Bibliography……………………………………………………………………………………………... 16 ___________________________________________________________________________________________ On Whales and their Usefulness/ n°1 / Robin des Bois / April 2010 – 2/18 On Whales and their Usefulness 7 7 et al. 200 Braby © A polar crab on grey whale remains grazing on a carpet made of bone scavenging organisms Introduction Scientists have long thought that animal and vegetal life in the sea was exclusively dependent on solar energy and photosynthesis. After the discovery in 1977 of hydrothermal vents and cold seeps in the deep-sea, they thought that only these geological phenomenons could generate and assemble biological communities based on the association of bacteria transforming sulphur into organic matter and fauna evolving in an obscure yet colourful environment; but ten years later new discoveries have proved that whale carcasses and their skeletons in the aphotic zones of the ocean are also sources of life thanks to the symbiosis between bacteria and many extreme and hyper specialised animal species. The deep-sea includes water and seafloors below 200m, representing 64% of the Earth’s surface and 90% of the world’s oceans which feature an average depth of 3,730m. The oceans’ seafloors have long been seen as an isolated compartment yet recent advances of knowledge show that deep waters and species are vertically and horizontally connected to shallow waters through currents; this enrichment process takes place in both directions. Thus it is known for example that deep-sea fish species are contaminated by PCBs from surface waters. Ecological services rendered to the Earth by the deep-sea are beginning to be better understood, for instance primary food production of chemosynthetic bacteria and the recycling of ocean nutriments without which primary production in the ocean photic zones would collapse. ___________________________________________________________________________________________ On Whales and their Usefulness/ n°1 / Robin des Bois / April 2010 – 3/18 When dead whales fall to the dark seafloor, where phytoplankton cannot develop, carcasses are used both as food and habitats by hundreds of fish and invertebrate species. For instance, the octopus below resides in a grey whale skull 2,891m deep. © Goffredi et al. 2004 et al. 2004 © Goffredi Whales are accused by whaling countries of depleting commercial fish stocks, but their role after death as well as that of other marine mammals in conservation of marine biodiversity and dispersal of deep sea species is largely unknown and underestimated. On the contrary, the reduction of whale falls caused by historical and ongoing hunting as well as pollution is a disadvantage for biodiversity and fish. In the deep-sea, whale falls resemble oases in terrestrial deserts, along with sea snow, made up of dead plankton, crustacean molts, shell waste, diverse excretions and riverine inputs, falling at a rate of approximately 300m a day eventually covering the abyssal depths, the arrival of a food reserve such as a 40 ton whale is an opportunity for fish and other scavengers. All at once, the equivalent of 2,000 years of organic carbon falls, concentrate on about 50m² of sediment. 2 2 200 © MBARI Whale remains and biodiversity: sea cucumbers, crabs and a profusion of osedax worms. In the case of larger specimens, the decomposing of a whale carcass could last over 100 years and follows four overlapping stages: 1- The mobile scavenger stage, including fish and amphipods, which can last up to ten years when flesh and soft tissues are removed from the carcass. ___________________________________________________________________________________________ On Whales and their Usefulness/ n°1 / Robin des Bois / April 2010 – 4/18 2- The opportunistic stage includes bacteria and invertebrate species on the skeleton and surrounding sediments. 3- The sulphur stage lasting up to 50 years during which worms and bivalves live in symbiosis with bacteria transforming sulphur hydrogen into organic and nutritious sulphur. 4- The reef stage. I- Stage 1 From 40 to 60 kg of flesh and soft tissues are removed per day. Thirty-eight faunal species have been identified. Macro fauna can be defined as organisms visible to the naked eye. The chronological scheme is as follows: crustacean plankton, sharks, and scavenger fish. The crustaceans are part of the diet of black snailfish, sablefish, crabs and opportunistic fish. This stage is characterised by high density but low diversity of species. Large numbers of amphipods and copepods consume most of the flesh. They break through the skin and create tunnels that ease access to muscles and fatty tissue for other predators. Amphipods AWI d'Acoz/ d'Udekem © Cédric / Wikimedia© Uwe Kils The order of amphipods in the crustaceans class are present in the world’s ocean down to the hadal zones, situated below the abyssal zone. They resemble shrimps. Amphipods are eaten by fish, invertebrates, penguins, birds and marine mammals. Mean length ranges between 4 and 10 mm. The best known amphipod species are sand fleas or talitridae that jump onto beaches and feed off organic waste in the inter-tidal zone. They are usually carnivorous and waste eating organisms. These planktonic organisms do not have autonomous swimming capabilities over long distances therefore they are displaced by currents. ___________________________________________________________________________________________ On Whales and their Usefulness/ n°1 / Robin des Bois / April 2010 – 5/18 Sharks Among the first to arrive at the whale fall are Pacific sleeper sharks (Somniosus pacificus) who can reach depths of 2,000m. These polar sharks are physiologically adapted to very low temperatures. Many are incidentally caught by trawlers in the Gulf of Alaska. Biology and physical characteristics of the Pacific sleeper shark are poorly known particularly concerning the reproduction cycle and gestation time. At birth, they can measure less than 40 cm and adults could reach up to 7 m long. Due to lack of data, the conservation status of the Pacific sleeper shark is unknown. Pacific sleeper sharks of 1.5 to 3.5 meters were seen feeding voraciously on the carcass of a grey whale and close to another carcass. From the observation of bite marks, it has been estimated that these sharks consume more of the whale flesh than other fish species. I 2004 MBAR - © David Clague Clague © David According to a Swedish study, bite marks on a Minke whale fall (Balaenoptera acutostrata) in the North Sea show the presence of a different species of sharks. This species could be the Greenland shark (Somniosus microcephalus). Historical exploitation of this shark peaked in 1910, its liver oil was sought for its alleged strengthening virtues. Today it is occasionally a by- catch from trawling and other fishing methods. It is for this reason that it is now considered an endangered species. Hagfish Hagfish (Myxinidae) can be sighted by the hundreds on whale falls, mainly black hagfish (Eptatretus deani) and Whiteheaded hagfish (Myxine circifrons). Hagfish designates a uniform group of about 60 species found in cold and deep water. They are considered to be the most primitive forms of fish. There is no notable difference between a 300 million year old fossil and a specimen living today. They live about 5 years and their mean length is 60 cm long. Ranging across the oceans, they can live in depths of 3,000 m and can inhabit areas as close as 40 m below the water surface and have developed surprising capabilities. They constitute the only fish species known to have in their blood the same level of salt as in the immediate surroundings. When attacked, they produce from 5 grams of excreted dry fibre up to 20 litres of a viscous substance obtained from the excretion of the fibre and its mixing with seawater. This substance could clog the gills of predatory fish. They owe their name to the Greek word musca (mucus). Hagfish feed off dead or dying fish and marine mammals. A large number are found in the by-catches of trawlers specialised in deep sea fishing; they seem to have acquired the habit of preying on trapped dead or dying fish. ___________________________________________________________________________________________ On Whales and their Usefulness/ n°1 / Robin des Bois / April 2010 – 6/18 They take up residence inside the carcass of the whales where they can resist exceptionally high levels of carbon gas and methane for days. Hagfish are thought to have been attracted to carcasses off the Californian coast from a perimeter of 0.6 to 0.8 km by smell or other sensor signals. : Source http://leatherplaza.tripod.com/ They are eaten in Asian countries and their smooth skin is used to make leather, called “eel skin leather”, mainly in Japan and South Korea. Fishery efforts peaked in 1986, worsened by the regular loss