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MarineBio Newsletter 6

MarineBio is pleased to bring you the 6th edition of our newsletter! We welcome your feedback on its content and would love to hear what you're interested in reading! Send your comments to:

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“What you see and hear is a perfected performance born of millions of years of concerted practice in the most competitive environment imaginable.” – Dr. Carl Safina, Eye of the Albatross

Featured Species: Sharks!

Great white sharks

Sharks, the apex predators of the Ocean, are amazing and majestic creatures that deserve the respect that they demand but do not deserve their reputation as indiscriminate killing machines. For years sharks have been associated with evil and gore, in part due to tall tales of shark attacks, such as “Jaws”, and in part due to their association with the deep and mysterious ocean. The reality is that sharks are magnificent and majestic creatures that keep the Ocean’s ecosystem in balance because of their role as apex predators. Shark ecosystems are quite varied. They can be found in tropical waters around the world and in temperate and arctic seas. Without them, smaller fish species would become overpopulated, which would have a domino effect on their marine ecosystems.

There are at least 500 shark species (with nearly 80 shark species threatened or endangered) ranging in size from a few inches up to 20 feet. The largest shark in history to inhabit the Ocean was the Megatooth shark, Carcharodon megalodon, which reached lengths up to 80 feet and only went extinct very recenty. According to fossil records, sharks are one of the oldest species on earth dating back as far as 400 million years and were the first vertebrates that had jaws. Incredibly, sharks have survived at least four global extinctions and are physically very similar to their ancient ancestors.

Their skeleton is made entirely of cartilage so they have no bones. Contrary to popular belief, there is no evidence that shark cartilage can cure or prevent cancer. Most shark species also have an extremely thick and rough skin covered in small tooth-like scales. Body shapes vary greatly among shark species. Some have thick, round bodies and other have very flat bodies. Most are torpedo shaped and have 2 dorsal fins, 2 pectoral fins, a tailfin, a caudal or tail fin, and pelvic fins. There are 5-7 gill slits on either side of the body through which water passes after oxygen is removed as it passes over the gills. In order to maintain oxygen uptake, some sharks must swim constantly to force water through their mouths, over the gills, and out through the gill slits.

Unlike many other marine fishes, sharks do not have gas-filled swim bladders, although the Sand tiger shark, Carcharias Taurus, can actually gulp air into their body for buoyancy. Most sharks rely on their large oil filled livers to control their buoyancy. Some shark species have livers that make up as much as 25% of the shark’s body weight.

Sand tiger shark, Carcharias Taurus

Most shark species have mouths found on the underside of the head. Not only do sharks have large, often serrated, extremely sharp teeth, they actually have several rows of them. The teeth are constantly shed and replaced about every 1-2 weeks. Some species have molar-like teeth used to grind food, however most species have the more characteristic razor-sharp cutting teeth. The shape of the teeth depends on the prey of each species; some are pointed and others are both pointed and curved.

Shark Reproduction
All shark species reproduce by internal fertilization after the male grasps the female using his teeth and inserts his claspers and deposits sperm into her cloaca. But after internal fertilization occurs, the species vary in their reproduction biology. Some females produce eggs, commonly called mermaid’s purses that attach to Ocean substrates and develop externally nourished by a yolk sac (oviparous). Species that reproduce in this way are often bottom dwellers such as the epaulette shark or horn sharks. Other species give birth to live young, which are nourished by an umbilical cord and develop inside the female (viviparous). Hammerheads are viviparous. Species such as tiger and whale sharks nourish multiple eggs internally with a yolk sac from an unfertilized egg then give birth to live young (ovoviviparous).

Unlike marine mammals, most shark species do not provide parental care as their newborn pups are independent and capable of finding food very shortly after birth.

Overfished shark populations are very slow to recover because sharks reproduce and grow very slowly, which increases the need to protect them from overexploitation.

blue sharks

Shark Diets
Contrary to popular belief, sharks are not indiscriminate eaters. While some shark species, such as bulls, tigers, and great whites, are more adventurous eaters than others, most sharks eat fish, squid, octopuses. The whale shark, one of the largest shark species, only eats plankton. Other large shark species also eat seals, sea lions, whales, and birds.

Sharks detect prey by using the 6 senses as well as a special sense that allows them to detect electric field signals from other animals. Sharks have an incredible sense of hearing and can hear fish and other movements in the water more than 3,000 feet away! Sharks’ sense of smell is also uniquely powerful and increases as their appetite increases. They can sense 1 part blood diluted in 1 million parts of seawater. Shark vision is also well-adapted to life underwater with a mirrored surface behind the eyes that helps them see in dim light.

Feeding frenzies occur when a group of sharks simultaneously feed on the same prey. Sharks in a feeding frenzy are quite agitated and tend to continue feeding even if they are hurt. Biologists are unsure why feeding frenzies occur but hypothesize that the sharks' brains become overloaded by too many stimuli such as prey, blood or the noise of irregular movements such as a struggling fish.

Lemon sharks

Fascinating shark facts:

Issues in Marine Conservation


Legend has it that in the late 1800s, fishermen were able to fish for cod in the North Atlantic simply by dipping a bucket into the water. This is, of course, an exaggeration but it is true that the cod was abundant in those times. Today, according to the Census of Marine Life, cod stocks on the Scotian shelf in the North Atlantic have dropped to a mere four percent of what they were in the late 1800s. Similar depletions are reported among other large predatory fish species such as tuna, swordfish, grouper, and shark. It is estimated that the most popular fish species among consumers, which are predominantly large fish species, have been depleted to one-tenth of what they were before the advent of commercial fishing on a massive scale. According to the Food and Agriculture Organization, more than 70% of the world’s fish stocks are overexploited for fully depleted.

These apex predators are essential to ocean health. Without them, species down the food chain will increase dramatically and cause disturbances to the balance of marine ecosystems. In spite of their importance to ocean health, these larger species are being depleted more rapidly than they can reproduce as well. In order to reverse this trend, fisheries require a radically different system of management that includes consideration for the impact large species have on their respective ecosystems. The fishing industry targets larger predatory species because they are more profitable and high in demand.

In an article recently published in Science News, Dr. Elliot Norse said: "We’ve always treated the ocean like a frontier, as if its resources were infinite and free to plunder. And several centuries ago, that may effectively have been true," says Norse. "However, humankind is now mining the ocean’s living resources, making them nonrenewable. We must learn how to use them sustainably—by understanding and respecting their biology."

Worldwide, fish currently supply the greatest percentage of protein for human consumption. Currently, the global fishing fleet is estimated to be 250% larger than needed to catch what the ocean can sustainably produce. There are a number of issues that need to be addressed quickly in order to preserve fish stocks as a natural resource.

There are a number of solutions to reverse the damaging trends created by overfishing. Management of fisheries worldwide needs to shift the focus from individual species (e.g. catch limits and other policies that consider a single target species) management to management that will support the entire ecosystem and food chain associated with target species. This approach is greatly needed to maintain populations of target species so that they are capable of fulfilling their natural role in ecosystems and of reaching sustainable reproduction rates. In addition to an ecosystem-based approach for policy makers, cooperation among all stakeholders is needed to ensure future sustainability including: policymakers, governments, the fishing industry, fishing communities, and the private sector.

Consumer awareness of the instability facing popular species’ populations is needed to empower consumers to choose wisely and drive the market toward sustainable fishing. This potentially powerful intervention is being implemented by organizations such as Blue Ocean Institute and the Monterey Bay Aquarium by publishing seafood guides to help consumers make informed choices when buying seafood. Some retail outlets are supporting sustainable fisheries by raising awareness of overfishing and selling only products of well-managed fisheries. Organizations such as the WWF have worked with corporations such as Unilever, one of the world's largest consumer food companies, to form the Marine Stewardship Council (MSC), which provides a mechanism for identifying and certifying sustainable fisheries.

Marine Protected Areas (MPAs) and no-take zones also have potential to ease the burden on overexploited fish stocks. MPAs and no-take zones provide target species with a haven to reproduce and feed. This solution, however, will only work if strictly enforced.

For more detail on this topic, see our new Sustainable Fisheries page. Note that at the bottom of the page you will find a list of organizations that support sustainable seafood consumption.

Current Research

The Work of The Census of Marine Life (COML)

COML defines its mission as: a growing global network of researchers in more than 70 nations engaged in a ten-year initiative to assess and explain the diversity, distribution, and abundance of marine life in the oceans—past, present, and future.

They want to know the answers to:

What lived in the oceans?

What lives in the oceans?

What will live in the oceans?

The current plan through 2010 is to quantify the answers to these questions and to help identify which species and their breeding sites are threatened so that decision makers can develop policies for the sustainable management of these resources and their biodiversity. Protecting these resources is important for a number of reasons such as 1) research for biochemicals for use in the development of pharmaceuticals and industrial compounds; and 2) research on some of the oldest biological processes on earth to explain climate, ecosystems, evolution, extinction, and migration.

The data gathered by COML will help to combine the ocean’s living history with information from current exploration so that the future of the ocean can be determined. For example, scientists use historical and environmental archives to determine what the ocean was like before the advent of human activity and to study the impact of environmental changes to develop a History of Marine Animal Populations.

COML is also working to quantify the diversity, distribution, and abundance of marine life by dividing the ocean into 6 ocean realms, or marine regions, habitats, or oceanic communities, that span life at the surface and near shore communities to ecosystems at the bottom of the deep ocean:

Each of the Census field projects focuses on a specific realm, and is using the latest technology to collect data on diversity, distribution, and abundance of species. The field projects include:

Near shore and coastal communities
An international collaboration called NaGISA, which in Japanese means coastal zone where the land meets the sea, is working to inventory and monitor biodiversity in the inshore zone of depths of less than 20 meters. Another COML project is documenting the biodiversity and related processes in the Gulf of Maine, which in this zone and is a heavily fished ecosystem. This project aims to help establish ecosystem- and science-based management of the area.

Continental Margins and Abyssal Plains
Just beyond the coastal zone, the continental margins and abyssal plains are found marking the sides and the bottom of the oceans. A deep-sea project is currently documenting the species diversity of this zone to increase understanding of the historical causes and ecological factors regulating biodiversity.

Central Waters—Light and Dark Zones
The continental margin and abyssal plains contain the central waters of the ocean. Two COML projects are working to track the movements of marine life through the light zone of these waters, or the top 200 meters where sunlight penetrates. One project is using electronic tagging technology to track the migratory patterns of Pacific Salmon and other species along the length of North America's west coast. A second project is also using tagging technology to monitor the movements of top predators in the Pacific. Another COML field project is working to increase understanding of the ocean's dark zone 4,000+ meters below the surface, which is virtually unexplored territory. Research efforts are focusing on the distribution and community structures of larger marine inhabitants in waters around the Mid-Atlantic Ridge, the enormous mountain ranges of the northern Mid-Atlantic.

Active Geology—Vents and Seeps
Since the discovery of hydrothermal vents and seeps little more than a quarter century ago, scientists have been studying these areas to understand the processes that drive these isolated ecosystems found at least 1,000 meters deep. These areas are home to a variety of new species, the study of which will lead to an understanding of how they survive in an environment that lacks sunlight.

Other Regions, Habitats, and Oceanic Communities
Census projects are also underway to examine microbes, plankton, coral reefs, continental margins, seamounts, the Arctic and Antarctic to increase understanding of all factors that influence biodiversity in the world's seas.

Data collected is entered into the Ocean Biogeographic Information System (OBIS), which is a web-based catalog or database of global geo-referenced data on marine species. OBIS also provides on-line tools for visualizing relationships among species and their environment. This valuable data is being used to create mathematical ecosystem models that will help predict changes in the Future of Marine Animal Populations caused by environmental or human influences.

The COML is headquartered in Washington D.C. where a secretariat is based at the Consortium of Oceanographic Research and Education. The COML is governed by national and regional steering committees, and technology is monitored by the Scientific Committee on Oceanic Research Working Group to ensure that the latest technology is being used.

COML is supported by a number of agencies and organizations including government agencies concerned with science, the environment, and fisheries, and private and corporate foundations. The COML is affiliated with a number of international organizations including:

The Intergovernmental Oceanographic Commission of the United Nations
The Food and Agriculture Organization of the United Nations
The United Nations Environment Programme and its World Conservation Monitoring Center
The Global Biodiversity Information Facility
The International Council for the Exploration of the Seas
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.

» Visit the Census of Marine Life (COML) website

MarineBio Recommends

Marine Conservation Biology : The Science of Maintaining the Sea's Biodiversity

Edited by Drs. Elliott A. Norse and Larry B. Crowder, this excellent book is the updated first scholarly text to educate on the science of marine conservation biology.

From the publisher:

Humans are terrestrial animals, and our capacity to see and understand the importance and vulnerability of life in the sea has trailed our growing ability to harm it. While conservation biologists are working to address environmental problems humans have created on land, loss of marine biodiversity, including extinctions and habitat degradation, has received much less attention. At the same time, marine sciences such as oceanography and fisheries biology have largely ignored issues of conservation.

Marine Conservation Biology brings together for the first time in a single volume leading experts from around the world to apply the lessons and thinking of conservation biology to marine issues. Contributors including James M. Acheson, Louis W. Botsford, James T. Carlton, Kristina Gjerde, Selina S. Heppell, Ransom A. Myers, Julia K. Parrish, Stephen R. Palumbi, and Daniel Pauly offer penetrating insights on the nature of marine biodiversity, what threatens it, and what humans can and must do to recover the biological integrity of the world's estuaries, coastal seas, and oceans.

Sections examine: distinctive aspects of marine populations and ecosystems; threats to marine biological diversity, singly and in combination; place-based management of marine ecosystems; the often-neglected human dimensions of marine conservation.

Marine Conservation Biology breaks new ground by creating the conceptual framework for the new field of marine conservation biology—the science of protecting, recovering, and sustainably using the living sea. It synthesizes the latest knowledge and ideas from leading thinkers in disciplines ranging from larval biology to sociology, making it a must-read for research and teaching faculty, postdoctoral fellows, and graduate and advanced undergraduate students as well as the general public.

We consider this book one of MarineBio’s “bibles” because of the wealth of information it provides on marine biodiversity, the problems associated with it, and innovative solutions and strategies for long-term conservation.

California Marine Life IdentificationWe also recently enjoyed California Marine Life Identification. This informative and entertaining marine biology DVD produced by Hammerhead Video was designed to educate scuba divers on the variety of marine life found off the California coast. Narrated by Kristine Barsky, a marine biologist and experienced scuba diver, the DVD provides fascinating details about California marine life along with underwater footage of more than 80 species of marine plants and animals that inhabit the California coast. Viewing this DVD prior to diving the California coast will enhance any diver’s ability to enjoy the fantastic sea life found in these waters. We thoroughly enjoyed this DVD for its captivating footage and informative narration.

We hope you found this quarter's MarineBio Newsletter interesting. Click around for more species, more research and more Marine Biology News. As always, we welcome all feedback.

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