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How Many Fish In The Sea? Census Of Marine Life Launches First Report

October 24, 2003
Census Of Marine Life
An estimated 5,000 previously unknown ocean fish species and hundreds of thousands of other marine life forms are yet to be discovered, according to scientists engaged in a massive global scientific collaboration to identify and catalog life in the oceans.

An estimated 5,000 previously unknown ocean fish species and hundreds of thousands of other marine life forms are yet to be discovered, according to scientists engaged in a massive global scientific collaboration to identify and catalog life in the oceans.

The new marine fish species, being identified at an average rate of 160 per year (roughly three new species per week since year 2000), are being catalogued and mapped by the Census of Marine Life (CoML), an unprecedented cooperative initiative involving leading marine scientists from every world region. The Census issued its first report after three years of work Oct. 23 at the Smithsonian Institution, Washington D.C.

More than 300 scientists from 53 countries are at work on the Census, designed to assess the diversity, distribution and abundance of ocean life and explain how it changes over time. The scientists, their institutions and government agencies are pooling their findings to create a comprehensive and authoritative portrait of life in the oceans today, yesterday and tomorrow.

Over 15,300 species of marine fish are now included in the Census database with another 2,000 ¡V 3,000 expected by the time of the final Census report in 2010. CoML experts expect the final count of marine fish species to total roughly 20,000.

An average of 1,700 other animals and numerous marine plants are also being catalogued each year. CoML scientists estimate that 210,000 marine life forms of all types are currently known to science, but the total in existence could be up to 10 times that number.

The first Census report - The Unknown Ocean: Baseline Report for the Census of Marine Life - reviews the state of knowledge of ocean biodiversity and how it has advanced during the first three years of the ambitious 10-year, $1 billion Census initiative. Following the report¡¦s launch, leading scientists involved in the project will meet to map out research priorities for the next seven years, one of the most important meetings of ocean researchers ever conducted.

On a practical level, the Census identifies threatened species and important breeding areas, helping fisheries authorities develop effective strategies for the sustainable management of marine resources. New pharmaceuticals and industrial compounds are among the potential bio-prospecting spin-offs of the thousands of new species being found. Other benefits include identification of "watering holes" or "oases" and "nurseries" in the open and deep oceans that merit protection.

As well, the Census is helping develop and test new technologies that will permit exploration of areas unreachable today, vastly improving human understanding of ocean life.

By cataloging and monitoring changes in size distribution and composition of marine life, the Census will help predict ocean life in the future. Scientists also believe that as they reveal the secrets of Earth¡¦s last largely unexplored frontier, they will expand understanding of elemental processes such as climate, evolution, extinction and migration.

"This is the start of the first great voyage of discovery of the 21st Century," said J. Frederick Grassle of Rutgers University, Chair of the CoML Scientific Committee. "More importantly, it begins the first systematic global effort to measure our oceans' vital signs, and guide what must be done to reverse their decline."

Despite their importance for human well being, the oceans are mostly unexplored and little is known about the life they support, said Ronald O'Dor, chief scientist for the Census. "The enormous diversity of marine life is not only a crucial indicator of the condition of our oceans, it is key to sustaining them in a healthy state," he said.

"Increases in toxic compounds and temperature in the sea are occurring globally with consequences that are hard to predict," said Dr. O'Dor. "Accurate measures and predictions of species distribution, abundance and natural variation through time across a range of species are urgently needed to help policy-makers respond appropriately to the consequences of changes in the ocean."


Among discoveries made during the first three years of CoML projects (some of which are summarized in the Baseline Report):

• The results of tracking west coast salmon in the past two years challenge traditional notions about the survival of young salmon as they leave their home rivers and enter the ocean. Understanding life for salmon at sea may be key to maintaining their populations. The Census is creating an underwater observation system that will enable tracking of tagged salmon and marine animals anywhere on the continental shelf.

• Attached to the dorsal fins of three species of Pacific sharks are electronic tags that regularly communicate with satellites, enabling documentation of migration patterns. Similar technology has recorded trans-Pacific migrations of bluefin tuna. These fish, sharks, turtles and elephant seals are helping Census researchers record and report the vertical structure of the vast oceans.

• Less than 10 miles off the Florida Keys, scientists recently discovered a new species (and perhaps new genus) of sponge - bright red and nicknamed the "rasta sponge". Chemical compounds found in it may help treat cancerous tumors.

• CoML deep-sea researchers exploring the abyssal sediments off Angola found an environment with more species per area than in any other known aquatic environment on Earth. About 80 % of the collected species were new to science (more than 500 suspected new species have been recognized in samples so far with a final total of 1,000 expected). The research will improve understanding of the relationship between deep-sea species diversity and the richness of food productivity in the water column and help predict the effects of global warming.

• Degradation of coral reef ecosystems began centuries ago, but no global summary of the magnitude of the change that occurred has ever previously existed. Extending back thousands of years, records of the status and trends of seven major types of carnivores, herbivores, and architectural species have been compiled from 14 regions. Large animals declined before small animals and other species, and Atlantic reefs declined before reefs in the Red Sea and Australia, but the rate of decline was markedly similar worldwide. All reefs were substantially degraded long before outbreaks of coral disease and bleaching.

• CoML research shows that by the year 1600 the level of fishing in Northern Europe was already heavily impacting the ecosystem. The European grey whale had been hunted to extinction. The herring catch in 1600 reached 100,000 tonnes per year and quintupled well before 1900; in the 1960s and 1970s the fishery was closed altogether. Following the strict imposition of measures to restore the herring fishery, it now sustains a total annual catch of 307,000 tonnes.

• CoML studies of tagged Pacific Leatherbacks, a marine turtle at risk of extinction this century, are revealing critical habitat and foraging grounds in the eastern Pacific, the goal being to help fishers avoid them;

• Underwater video technologies have revealed surprisingly rich three-dimensional habitats formed by corals and sponges in the deep-seas worldwide, replacing general beliefs that the deep-sea was mostly mud. These habitats, very important for fish and other marine life, are easily flattened by trawling. Scientists at the Oct. 23 news conference premiered never-before-seen video of life in the Mid-Atlantic Ocean at the unprecedented depth of 2.7 miles (4500 metres). The video was captured in June by CoML scientists in the MAR-ECO Project, the first human beings to ever explore the depths of the Charlie-Gibbs Fracture Zone in the North Atlantic. In addition to the variety of life at that depth, scientists were surprised by the volume of "marine snow" present, aggregations of biological debris that sift slowly downwards from the upper layers of the ocean.

• Scientists suspect that fishes indigenous to one side of the Atlantic Ocean may be using extinct undersea volcanoes as stepping stones to migrate to the other side. Exploring the Bear Seamount, the westernmost underwater peak just off Georges Bank, CoML scientists identified at least 17 species of fish, including eight from the eastern Atlantic that were previously unknown in the western Atlantic. They were among 152 species of fish and 183 species of invertebrates identified at Bear Seamount on a single cruise.

Four components of the Census

The Census of Marine Life has four components, the first three being:

• History of Marine Animal Populations (HMAP) uses historical and environmental archives to analyze marine population data to create a picture of the oceans before fishing and the relative impacts of human activities and environmental fluctuations after fishing became prevalent;

• Future of Marine Animal Populations (FMAP) synthesizes Census-generated information to develop mathematical ecosystem models to predict future changes in marine animal populations caused by environmental and human influences; and

• Ocean Biogeographic Information System (OBIS) is a web-based catalog of global geo-referenced information on marine species, with online tools for visualizing relationships among species and their environment. Work is underway to synthesize OBIS data to create educational content directed at students.

Field projects (currently seven, with up to eight more envisioned) constitute the fourth Census component. The seven current projects involve detailed study of:

• Shore Areas (project NaGISA). An international collaboration to inventory and monitor biodiversity in the narrow inshore zone at depths of less than 20 meters;

• The Gulf of Maine. The project documents biodiversity and related processes in the Gulf of Maine, a heavily fished ecosystem. The project examines everything in the water column, from life in the bottom sediments to microbes to whales. The Gulf of Maine was chosen for study because it also has more complete observations of such variables as temperature and currents than most other marine ecosystems;

• Salmon and other Coastal Migrants (project POST) Application of new electronic tagging technology and creation of a monitoring network spanning the Continental Shelf along North America's west coast to study the environments and routes of Pacific Salmon and other migratory species;

• Abyssal Plains (project CeDAMar). A deep-sea project documenting species diversity of abyssal plains to increase understanding of the historical causes and ecological factors regulating biodiversity and global change;

• Top Predators - the Pacific (project TOPP). Use of electronic tagging technologies to study migration patterns and behaviors of large open-ocean animals and the oceanographic factors that influence them. The objective is to infer from the behavior of animals at the top of the food chain an explanation of their abundance and distribution;

• An Underwater Mountain Range: the Mid-Atlantic (project MAR-ECO). A study of the huge mountain ranges of the northern mid-Atlantic, including the processes that control the distribution and community structures of larger marine inhabitants in waters around the Mid-Atlantic Ridge;

• Vents and Seeps (project ChEss). A global study of deep-sea life that exists around dark seafloor vents and seeps and the processes that drive these isolated ecosystems that serve as nurseries for new species.

Three of the Census' seven initial field studies are based in North America, three in Europe and one in Japan. New upcoming field projects (including examinations of microbes, plankton, reefs, the Arctic, and seamounts) will be based in the Southern Hemisphere and other regions.

Each project is demonstrating the use of a new technology or technique for collecting data on diversity, distribution or abundance. As the Census proceeds, these sampling methods will be used to expand studies internationally.

The Known, Unknown and Unknowable

The first Census report describes efforts to separate the known from the unknown and unknowable.

Creating an inventory of the known, it says, is easiest. "Stone tablets, libraries, and now the electronic web have accumulated a vast inventory of the known." Earlier this year the Census FMAP team reported that every species of large wild fish has been caught so extensively over the past 50 years that 90 per cent of each type has disappeared.

Separating the unknown from the unknowable is far harder. Intrinsically, some things are simply unknowable, such as the number of fish in a bay a decade from now given such variables as climate change. As well, "some things are unknowable because the search is impractical" -- for example, a sea to be explored is inaccessible, specimens explode from extreme pressure when brought to the surface, or the cost and tedium of exploration become overwhelming.

Life in the "Six Ocean Realms"

The report describes the known, unknown and unknowable in six ocean realms - the human edges, hidden boundaries, light and dark zones of the central waters, active geology, ice and microscopic.

The Human Edges

While scientists know much about what lives near the shore, continuing effort is needed to measure changes, according to the report, and many species remain unknown and perhaps unknowable. For example, in just three cubic meters of a coral reef off New Caledonia in the South Pacific, some 130,000 molluscs were found belonging to 3,000 species, many undescribed.

To date, 2,000 species of plants and animals have been recorded in the Gulf of Maine alone, an area intensively studied as a Census pilot project, ranging from microbes in bottom sediments to whales in the wind-driven surface. Global estimates now place a total of 12,000 species in the nearshore realm worldwide.

Hidden Boundaries

Continental margins and abyssal plains hidden beneath the waters bound the oceans¡¦ sides and bottom. At the limit of some continental margins, trenches more than four kilometers deep open. The deepest water and greatest pressure in the world lie at the bottom of the 11 km-deep Mariana Trench in the Eastern Pacific near the island of Guam.

The hidden margins support many of the same species associated with deeper waters. Margins feature more complicated habitats than the abyssal plains at the bottom and are likely nursery areas in which new species evolve.

The abyssal plains are the accumulation of eons of marine snow -- particles, some living and some not, falling through kilometers of water and settling at the bottom of the oceans. The silt is wider than any other habitat on the planet -- 5 km deep in places -- giving depth of silt the same scale as the ocean above. The abyssal plain contains 100,000 known species, mostly small crustaceans and various worms. The nutrition of the plain, its sheer volume, and its unchanging character over millions of years account for its incredible diversity and abundance.

The darkness, depth, pressure, and size of the abyssal plain make continuous or even frequent observations in this realm extremely difficult, hiding how fast things are changing, which will keep much of the life this area unknowable. Experts question whether even an intensive and expensive sampling program could describe the projected millions of new species in this currently inaccessible realm.

The Central Waters - light and dark zones

The oceans' central waters fill the vast bowl formed by the hidden boundaries. Sunlight penetrates and fuels photosynthesis of food within the top 200 meters or so, enriching these waters that cover 70% of the planet and feeding tens of thousands of species. A marine snow from the light zone falls into the dark zone between the light and abyssal plain, feeding still more species.

The 50,000 species of plankton in the light zone are mostly single cell organisms like many algae and protozoa or krill, miniature relatives of shrimps. Plankton capable of photosynthesis, the phytoplankton, is the grass in the oceanic pasture, converting CO2 gas into 300 billion tons of food for tiny animals like krill that in turn feed the larger animals up the food chain. This is equal to all the food on land made through photosynthesis.

Satellites looking at light reflected from the ocean provide reasonable indications of the location, abundance, and even some kinds of phytoplankton present across most of the ocean surface, revealing oceanic hotspots, the equivalent of lush meadows on land.

Some 20,000 swimming species of inhabit the light zone, including the oceans¡¦ largest mammal (Blue Whales) and largest fish (Whale Sharks). Questions in the light zone are more about distribution and abundance than about the species themselves. The uncertain movement of organisms in the light zone and the scarcity of scientists to monitor them render some knowledge beyond current reach. For example, whales cruising at 20 km/h could circle the globe several times in a year. The lush pastures of phytoplankton sometimes move thousands of kilometers in a year.

Extending more than 4,000 meters into pitch-blackness, the dark zone's volume exceeds by many fold the volume of the 200-meter light zone. The snow of wastes, carcasses of large animals, and swimmers venturing below their normal light zone end up as food for animals in the dark beneath. The mass of organisms declines with depth, modified by mid-ocean ridges that affect circulation just as mountains affect weather on land.

Some 20,000 species live in mid-water; arthropod crustaceans and chordate fish predominate, but strange floating jellyfish and molluscs are also important.

Several hundred thousand species exist in the bottom water and many may remain unknowable. In the dark, at 200 m to 5 km below the surface, without normal oxygen and at crushing pressure, many species may never be caught and named. And, if they are caught and brought to the surface, their shape will change as a result of the pressure changes.

The Active Geology -- Seamounts, Vents and Seeps

To qualify as seamounts, underwater ghost volcanoes must rise at least 1,000 m from the abyssal plain without appearing above water as an island. At mid-ocean ridges interactions among the liquid magma from Earth's core, gases, and water at extreme pressures create high temperature deep-sea vents rich in chemicals that feed bacteria at the base of these unique food chains. At many continental margins, groundwater and oil seep out of rocks to feed bacteria. The flows caused by vents and seeps allow the creation of food without light and good conditions for species evolution.

Although the technology to explore vents and seeps may differ, research shares the need for comparing species and behaviors that colonize and sustain isolated populations. The number of species known to inhabit the active geology realm stands at 6,000. Vents and seeps were only discovered 25 years ago, but 700 new species have already been described, from a few dozen sites. Recent explorations of seamounts found that 15-40% of the species collected were new to science and likely found nowhere else.

The Ice Oceans -- Arctic and Antarctic

In the cold, inhospitable oceans near the poles, photosynthesis still proceeds as microscopic algae absorb light transmitted through the ice and feed a spectrum of life from crustaceans to fish to mammals, like seals and narwhals.

In the ice oceans the unknown species are largely nematodes and single cell organisms. Large opportunities lie in interpreting the samples already collected in Antarctic waters and in exploring the neglected cracks in the sea ice, the coastal fjords of the Canadian Archipelago and Greenland and the Eastern Siberian Shelf. A recent international expedition to the Canada Basin using the newest under-ice technology discovered and filmed large schools of arctic cod between the layers of pack ice. Normally bottom feeders, these cod were filmed grazing on upside-down algal pastures. This surprising find encourages further exploration under the ice.

The Microscopic Microorganisms in the oceans make up for their minute size by their numbers. The 1030 microbe cells in the ocean comprise more than 90% of the mass of all living things in the oceans, and represent an amount of biomass 10,000 times greater than all the world¡¦s whales. Some 50% of earth¡¦s oxygen is created by photosynthesis produced by ocean microbes.

Challenges ahead

The report describes huge challenges ahead en route to a comprehensive Census.

For example, nearly 500 fish taxonomists work to classify and name fish in the world today. This is likely 10 times the number of taxonomists working on non-commercial marine groups like nematodes (worms consisting of an elongated stomach and reproduction system inside a resistant outer skin. A microscope is needed to see most nematodes, which measure between 400 micrometers to 5 mm.). Nematode taxonomists, even if working 10 times as fast as fish experts and given the benefit of today¡¦s information technologies, would need thousands of years to name most of the estimated 1 million unknown species.

"By the end of the 10-year Census initiative, we expect several results," says Jesse Ausubel, Program Director of CoML for the Alfred P. Sloan Foundation. "We will have identified many new species and will know with far greater precision how many remain undiscovered. "We will know better whether the size spectrum of animals in the ocean is changing: Are small animals replacing the large? We will know better how changes in the abundance of ocean life are shifting among major groups: Are jellies replacing fish? And we will know much better what we do not know - identifying the unexplored.

"As important," he added, "we will have created fundamental tools for the future, especially the Ocean Biogeographic Information System, the essential information utility for the next generation of marine resource managers and researchers, and components of the Global Ocean Observing System monitoring marine life. This observing system, used to monitor waves and currents as well as whales and microbes, should improve our view of marine life and conditions in ways unimaginable short years ago."

Said Dr. Grassle: "We hope our early progress inspires many others to join in writing and appreciating the marine chapters of life¡¦s encyclopedia. We invite additional worldwide support and participation to advance this remarkable work."


Census of Marine Life sponsors:

Support for the Census of Marine Life comes from government agencies concerned with science, environment, and fisheries in a growing list of nations as well as from private foundations and companies. The Census is associated or affiliated with several intergovernmental international organizations including the Intergovernmental Oceanographic Commission of the UN, the Food and Agriculture Organization of the UN, the UN Environment Programme and its World Conservation Monitoring Centre, the Global Biodiversity Information Facility, the International Council for the Exploration of the Seas, and the North Pacific Marine Science Organization. It is also affiliated with international nongovernmental organizations including the Scientific Committee on Oceanic Research and the International Association of Biological Oceanography of the International Council for Science. The Census is led by an independently constituted international Scientific Steering Committee whose members serve in their individual capacities and a growing set of national and regional implementation committees.

Participating countries so far include:North America: Canada, US, Mexico, BermudaSouth America: Chile, Peru, Ecuador, Colombia, Venezuela, Guiana, Brazil, Uruguay, ArgentinaAsia and the Pacific: New Zealand, Australia, Japan, South Korea, China, Taiwan, Vietnam, Philippines, Indonesia, Malaysia, Thailand, IndiaEurope: Russia, Norway, Ireland, Iceland, UK, Portugal, Spain, France, Belgium, Netherlands, Italy, Greece, Germany, Denmark, Estonia Africa: South Africa, Ivory Coast, Ghana, Nigeria, Cameroon, Gabon, Angola, Namibia, Mozambique, Tanzania, Kenya, Madagascar, Mauritius, Seychelles

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Census Of Marine Life. "How Many Fish In The Sea? Census Of Marine Life Launches First Report." ScienceDaily. ScienceDaily, 24 October 2003. <>.
Census Of Marine Life. (2003, October 24). How Many Fish In The Sea? Census Of Marine Life Launches First Report. ScienceDaily. Retrieved May 21, 2024 from
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