In Sharkland, you’ll learn why species that are normally found oceans apart converge in this one relatively small stretch of coastline, and you’ll be introduced to many of these unique animals, including the catsharks of the Agulhas Bank a 155-mile-wide stretch of shallow warm seas off the southeastern tip of the continent, Southern Africa’s richest fishing grounds. You’ll also explore nature’s most extreme sharks – the fastest, fiercest, smallest, and strongest – and discover the innovative adaptations that have made the Great White such an efficient killing machine.

To order a copy of Sharkland, please visit the Nature Shop.

Online content for Sharkland was originally posted May 2007.

MISSION: SUPERFISH

Marine biologist and award-winning filmmaker Rick Rosenthal set out to capture on film the biggest, fastest, most dangerous gamefish in the sea — the ancient creatures known as billfish.

The largest of all billfish is the marlin. They top speeds of 60 miles an hour on migrations that can span 9,000 miles. The largest, always female, weigh in at over 1,000 pounds, and are known as “granders.” Ernest Hemingway immortalized the grander in The Old Man and the Sea, the story of an elderly fisherman locked in a life and death struggle with this apex predator. To Hemingway’s great disappointment, he himself never landed a grander, although his novella captures the impact of this huge and graceful creature.

Rosenthal’s pursuit of these exotic fish unfolds in NATURE’s Superfish. Two years in the making, Rosenthal’s documentary travels to the Pacific and Atlantic Oceans as well as the Caribbean Sea in pursuit of these giants of the deep. In one extraordinary scene, off Australia’s Cape York Peninsula, Rosenthal is shown swimming with a stunning giant female marlin and two courting males.

Throughout his journey, Rosenthal encounters commercial fisherman, anglers, and researchers, who are also out looking for billfish. The search has become increasingly difficult for everyone due to over-fishing of billfish and their prey, as well as the environmental degradation of the oceans, which has resulted in a dramatic decline in their populations. The trajectory of population decline in all large fish has been precipitously steep, estimated at 90 percent within the last half century.

In the 1950’s, sports fishermen — like those who flocked to Cabo Blanco, Peru in the heyday of “Marlin Boulevard” — were known for testing themselves against marlin with rods and reels. Today, some fisherman are defending billfish against commercial fishing fleets that, while going after the seafood we eat, kill these increasingly rare sport fish in their nets as so called accidental by-catch. In major part because of the absence of regulations that limit such by-catch, marlin and other billfish populations continue to decline. In the case of marlin, some anglers, frustrated with governmental inaction, have pressed for local bans on the sale of such fish, and have sought commitments from local restaurants not to serve marlin.

Rosenthal’s difficult quest to encounter a giant marlin in the wild, rewarded by his exceptional footage of this fabulous creature, not only offers a rare aesthetic and learning experience for viewers but may serve to awaken people to the need to preserve these remarkable billfish in their native habitats.

To order a copy of Superfish, please visit the NATURE Shop.

Online content for Superfish was originally posted May 2008.

Seafood lovers take note: there’s good news and bad news.

First, there’s the bad news for those who enjoy tuna on rye.

High concentrations of mercury, a neurotoxin that can damage developing brains in fetuses, are found in some kinds of popular fish such as albacore tuna. Swordfish and shark, king mackerel, marlin, orange roughy and tilefish also contain dangerous levels of mercury.

Women of reproductive age and young children are advised to avoid these types of fish and limit overall consumption of all fish to no more than 12 ounces per week, according to the Food and Drug Administration, as it takes months for the body to rid itself of mercury.

The danger from mercury is not just to developing brains. There is evidence to suggest an association between mercury exposure and heart disease, making it dangerous for everyone, but especially those who are already at risk.

The American Heart Association, however, recommends eating fatty fish at least twice a week because it is high in omega-3 fatty acids which are believed to help lower rates of heart disease, reduce hypertension, relieve some arthritis symptoms and prevent cancer. Fatty varieties that are low in mercury include herring, sardines, and wild salmon. Some popular fish that are also good choices include sole, tilapia, clams and oysters.

“It all depends on your diet — you can’t eat a lot of big, wild fish,” said Tim Fitzgerald, a marine scientist for Environmental Defense Fund, who provides health consumption information to Monterey Bay Aquarium’s Seafood Watch.

The problem with large, predatory species like marlin and swordfish is that they contain much higher levels of mercury than small fish, such as anchovies and sardines, because of the way mercury moves up the food chain. “Sharks, marlin, polar bears and people at the end of the food chain have the highest concentration of mercury,” Fitzgerald said.

It’s sometimes difficult for consumers to make seafood choices that are good for their health — and the environment. According to Tim Fitzgerald, “Billions of pounds of imported fish come into the United States annually, and less than one percent is tested for environmental toxins by the FDA.” Because marlin is not a popular dining choice in the U.S., many people are not aware of this. And while the FDA is the regulator body that creates consumer advisories about mercury for pregnant women, they actually do very little testing for this neurotoxin.

Another problem with the advisories is that they are not terribly specific and there’s a lot of room for interpretation, according to Fitzgerald. It’s also difficult for consumers to make the best seafood choices because sometimes what’s best for the environment is not always best for their health, and vice versa. For example, blue marlin and striped marlin from Hawaii are fairly resilient to fishing pressure and are listed as “good” alternatives for the environment on Seafood Watch. But, Seafood Watch also lists a health advisory for these fish, due to high levels of mercury. Monterey Bay’s other regional pocket guides provide further guidance for consumers and note that imported blue marlin and striped marlin should be “avoided.”

So, for U.S. consumers, the situation is “buyer beware — eat with caution,” but certainly not to give up on all fish. Consumers may just need some help from Monterey Bay’s Seafood Watch, which maintains a list of “which seafood to buy and why,” including a comprehensive seafood search, regional seafood guides — and printable pocket-sized guides for your wallet.

And, if you are a tech-savvy-seafood-lover, a “fish phone” may be more of what you’re looking for. Environmental Defense Fund’s Seafood Selector to-go allows mobile web users to look up their seafood guide on a blackberry or iPhone and download the information.

Ultimately, it’s ideal to exercise moderation and caution when eating seafood by taking into account both environmental and health concerns. Fortunately you don’t have to wonder whether the seafood menu at your favorite restaurant is environmentally friendly, the answers to your questions may just be a text-message away.

Background:
Sharks and their biological cousins, the rays, are among the highest-profile denizens of the deep. But sharks are not the solitary killing machines that popular movies and the press might have us believe. In their marine environment, sharks coexist with numerous other species – many of whom flock to be near the sharks, rather than running from them in fear. These excerpts from the NATURE episode “The Secret World of Sharks and Rays” examine the interrelationships between sharks and other marine species. In many of these cases, the interaction between two different species mutually benefits each species. But humans, too, have become an increasingly important player in the lives of sharks – and as they are increasingly hunted for their fins, sharks are actually becoming more endangered than they are dangerous. The impact on the marine ecosystem that would result from the disappearance of sharks would be devastating, but there is still time to save these magnificent creatures, and the ecosystems that depend on their existence.

Suggested focus questions:

Clip 1: Shark and Turtle

1. How does the turtle protect itself?
2. What relationship is held between the tiger shark and the loggerhead turtle?

Clip 2: Unlikely Travel Companions

1. List three ways in which being near a shark might be beneficial to a fish.
2. What is one way that a shark might benefit from a fish (other than as prey)?
3. Classify each shark-fish relationship shown in this clip as commensalism, mutualism, or parasitism.

Clip 3: Sharks and Fishermen

1. How have sharks become trained to follow fishermen?
2. Describe how the following species pairs interact in the clip: fishermen/fish; sharks/fish; sharks/fishermen.

Clip 4: Collapse of Sharks

1. Why are shark populations in danger of collapse?
2. How has the relationship between sharks and humans changed over time?
3. What might happen if the shark fin trade continues unchecked?

Clip 5: Sharks in our Future

1. Describe the type of tourism seen in this clip.
2. What benefit do these businesses provide to: sharks? To local populations? To tourists?
3. How might these businesses help prevent the collapse of shark populations?

Downloadable QuickTime versions of the video segments:
(Note: To download a video, right-click on the video title and click “Save Link As…” or “Save Target As…”. On a Mac, press the CTRL key and simultaneously click the mouse, then save the link.)

Clip 1: “Shark and Turtle”

Clip 2: “Unlikely travel companions”

Clip 3: “Sharks and fishermen”

Clip 4: “Collapse of sharks”

Clip 5: “Sharks in our future“

GRADE LEVEL: Grades 9-12

TIME ALLOTMENT: Five 45-minute class periods

OVERVIEW: This lesson focuses on symbiosis and ecological relationships. Students will investigate the many ways that species that live in close proximity to each other might interact in an ecosystem, whether via competition or predation or through an ongoing symbiotic relationship such as mutualism, commensalism, or parasitism. Segments drawn from the NATURE episode The Secret Lives of Sharks and Rays and an online interactive featuring the malaria parasite will be used to provide specific examples of these interactions. The students will discover that all ongoing ecological relationships, even parasitic or predatory ones, have evolved over long periods of time and are integral to the maintenance of the balance and stability of an ecosystem.

The lesson then moves to a discussion of the ways that ecosystems can be thrown out of balance, often as a result of human action. A video segment showing the barbaric practices of the shark fin harvesting industry is used as a case in point of a human behavior that places a species in peril. Students will brainstorm ideas for restoring the relationship between sharks and humans to a healthy balance and will view an optimistic video segment featuring the ecotourism industry. As a culminating activity, students will select a case study for which to formulate an “Ecosystem Action Plan.” They will research an ecosystem thrown out of balance by human action and will prepare a presentation for the class describing the problem and suggesting three possible actions that could be taken to rectify the imbalance.

SUBJECT MATTER: Biology/ Living Environment

LEARNING OBJECTIVES:

• Define and describe the possible ecological relationships between species that coexist in an ecosystem
• Classify specific interspecies relationships as mutualistic, commensal, or parasitic
• Understand that ecological relationships evolved over time and are integral to maintaining the balance and stability of ecosystems
• Name factors that can throw ecosystems out of balance
• Describe human actions that have contributed to ecosystem imbalance and species decline
• Suggest remedial actions to ameliorate human-caused imbalances in ecological relationships

STANDARDS AND CURRICULUM ALIGNMENT:

National Science Education Standards

CONTENT STANDARDS C: Life Science

All students should develop understanding of:

The interdependence of organisms

• Organisms both cooperate and compete in ecosystems. The interrelationships and interdependencies of these organisms may generate ecosystems that are stable for hundreds or thousands of years.
• Human beings live within the world’s ecosystems. Increasingly, humans modify ecosystems as a result of population growth, technology, and consumption. Human destruction of habitats through direct harvesting, pollution, atmospheric changes, and other factors is threatening current global stability, and if not addressed, ecosystems will be irreversibly affected.

New York State Regents Core Curriculum Alignments

Living Environment Core Curriculum

Standard 1: Students will use mathematical analysis, scientific inquiry, and engineering design, as appropriate, to pose questions, seeks answers, and develop solutions.

Key Idea 1: The central purpose of scientific inquiry is to develop explanations of natural phenomena in a continuing and creative process.

Performance Indicator 1.1: Elaborate on basic scientific and personal explanations of natural phenomena, and develop extended visual models and mathematical formulations to represent one’s thinking.

1.1a scientific explanations are built by combining evidence that can be observed with what people already know about the world.

Performance Indicator 1.2: Hone ideas through reasoning, library research, and discussion with others, including experts.

1.2a Inquiry involves asking questions and locating, interpreting, and processing information from a variety of sources.

1.2b Inquiry involves making judgments about the reliability of the source and relevance of information.

Standard 4: Students will understand and apply scientific concepts, principles, and theories pertaining to the physical setting and living environment and recognize the historical development of ideas in science.

Key Idea 1: Living things are both similar to and different from each other and from nonliving things.

Performance Indicator 1.1: Explain how diversity of populations within ecosystems relates to the stability of ecosystems.

1.1c In all environments, organisms compete for vital resources. The linked and changing interactions of populations and the environment compose the total ecosystem.

1.1d The interdependence of organisms in an established ecosystem often results in approximate stability over hundreds and thousands of years. For example, as one population increases, it is held in check by one or more environmental factors or another species.

1.1f Every population is linked, directly or indirectly, with many others in an ecosystem. Disruptions in the numbers and types of species and environmental changes can upset ecosystem stability.

Key Idea 6: Plants and animals depend on each other and their physical environment.

Performance Indicator 6.1: Explain factors that limit growth of individuals and populations.

6.1g Relationships between organisms may be negative, neutral, or positive. Some organisms may interact with one another in several ways. They may be in a producer/consumer, predator/prey, or parasite/host relationship or one organism may cause disease in, scavenge, or decompose another.

Performance Indicator 6.3: Explain how the living and nonliving environments change over time and respond to disturbances.

6.3c A stable ecosystem can be altered, either rapidly or slowly, through the activities of organisms (including humans), or through climatic changes or natural disasters. The altered ecosystem can usually recover through gradual changes back to a point of long-term stability.

Key Idea 7: Human decisions and activities have had a profound impact on the physical and living environment.

Performance Indicator 7.1 Describe the range of interrelationships of humans with the living and nonliving environment.

7.1a The Earth has finite resources; increasing human consumption of resources places stress on the natural processes that renew some resources and deplete those resources that cannot be renewed.

7.1c Human beings are part of the Earth’s ecosystems. Human activities can, deliberately or inadvertently, alter the equilibrium in ecosystems. Humans modify ecosystems as a result of population growth, consumption, and technology. Human destruction of habitats through direct harvesting, pollution, atmospheric changes, and other factors is threatening current global stability, and if not addressed, ecosystems may be irreversibly affected.

Performance Indicator 7.3 Explain how individual choices and societal actions can contribute to improving the environment.

MEDIA COMPONENTS

Video

NATURE: The Secret World of Sharks and Rays, selected segments

Clip 1: “Shark and Turtle”

A battle between a loggerhead turtle and a shark.

Clip 2: “Unlikely travel companions”

A variety of symbiotic relationships exist between sharks and other marine species.

Clip 3: “Sharks and fishermen”

Sharks and fishermen compete for the same catch.

Clip 4: “Collapse of sharks”

This clip shows the destructiveness of the shark fin and shark cartilage industries.

Clip 5: “Sharks in our future”

If sharks can be shown to have value while alive, their future may be bright.

Access the streaming and downloadable video segments for this lesson at the Video Segments Page.

Web sites

Malaria games from nobelprize.org
This site provides two games – the mosquito game and the parasite game – to help students understand the transmission of malaria.

Life Cycle of a Malaria Parasite Interactive Tour
This flash-based interactive tour provides a detailed explanation of each stage of the malaria parasite’s life cycle.

MATERIALS

For each student:

• Ecological Relationships Student Organizer (PDF) (RTF)

For each group (3-4 students):

• Malaria Student Organizer (PDF) (RTF)
• Computer with Internet access
• Ecosystem Action Plan Student Organizer (PDF) (RTF)

For the teacher:

• One computer with Internet access for class demonstration
• Teacher Answer Key (PDF) (RTF)
• Ecosystem Action Plan Assessment Rubric (PDF) (RTF)

PREP FOR TEACHERS

Prior to teaching this lesson, you will need to:

Preview all of the video clips and Web sites used in the lesson.

Download the video clips used in the lesson to your classroom computer, or prepare to watch them using your classroom’s Internet connection.

Bookmark the Web sites used in the lesson on each computer in your classroom. Using a social bookmarking tool such as del.icio.us or diigo (or an online bookmarking utility such as portaportal) will allow you to organize all the links in a central location.

Gather the necessary materials as outlined above in “Materials” in advance of teaching the lesson.

Next: Proceed to Activities