Shark Senses

Today we learned about shark senses. Sharks have a large brain to help process the sensory overload they must get from the SEVEN senses they have. They have the five we have plus a lateral line (pressure and vibrations) and the ampullae of lorenzini (electro-reception).

Follow this link for a cool interactive about how shark jaws stick out when they attack their prey! The interactive is down at the bottom.

If you are doing a final project on a shark... check out this new link! www.shark.ch

And once again... one try only... how much do you know about sharks? MsJ scored a 1467. Try Shark Weeks Ultimate Shark Challenge to see how much you know.

Shark Reproduction

Today students learned an introduction to sharks. We talked about the history of sharks, common characteristics of cartilaginous fish and then the reproductive strategies of sharks.

Not a lot is known about shark reproduction because in many cases it has never been observed.

Some sharks are oviparous and lay eggs (pictured). These egg cases are known as mermaid's purses. You can see the baby shark and its nutrient-rich yolk through the leathery egg case.

Some sharks are viviparous and have live birth a lot like mammals.

And some sharks are ovoviviparous and keep their eggs inside the uterus before releasing them... so its making eggs and then kind of having live birth.

Virginia Aquarium

Yesterday, many students had an exciting day at the Virginia Aquarium in Virginia Beach. The bus ride was long, but not as long and boring as most students expected. We ate lunch just as we arrived at the aquarium and then went to look at the exhibits.

Students were divided into groups and looked through the exhibits and examining the animals and answering the questions. The Virginia Aquarium is actually two building separated by a nature trail through the salt marsh and most were complaining how hot it was! It was pretty neat because you could see the fiddler crabs in the mud waving their arms around trying to impress the ladies.

Many students got a huge thrill out of touching the stingrays in the touch tank. I think stingrays feel like hotdogs - slimy but with a stiff structure. Another hit were the otters, which sometimes were sleeping and sometimes romping around. There were a lot of sea turtle fans and students were able to tell which were boys and which were girls (look how long the tail is). Students also learned how to tell boy and girl sharks apart.

After seeing the aquarium, students walked along a local beach completing a scavenger hunt and looking for sea shells. Many were surprised how much you could actually find on the beach and pleased that they knew what they were finding.

After a fast food stop for dinner, students climbed back on the bus for the long ride home. The rest area was just in time for a much needed break in the middle of the trip. Students arrived back at the school on time, a little tired, but after having a good day.

Fish Reproduction

Fish reproduce in a variety of ways. Most are broadcast spawners, meaning that when the time is right, the females release their eggs, the males release their sperm and they both meet and mix producing fertilized eggs that develop into fish fry and eventually into adult fish. These snapper are spawning and you can tell by the large cloud of gametes in the water.

By producing a lot of eggs, the snapper hope to overwhelm any predators trying to make a meal so that there is no way all the fry are eaten and some will have a chance of surviving.

Fishing Methods and Sustainable Harvesting

Thursday and Friday we discussed fishing and seafood harvesting, the good, the bad, and the just plain ugly.

The truth is that our oceans are being fished to extinction and emptiness. We are harvesting more and more fish from smaller and smaller populations. What is a person to do that wants to eat seafood, but not hurt the environment?

BECOME AWARE. Most people do not know where their seafood came from or how it was caught.

How it was caught makes a big difference. Different fishing methods have pros and cons for the environment and regarding bycatch (fish and other organisms like sharks, sea turtles, sea birds, and dolphins, that are caught, often killed, and not really wanted).

One of the biggest things to avoid is any kind of imported shrimp. Imported shrimp are either caught with destructive trawl nets that destroy habitats and that do not have TEDs that allow turtles and dolphins to escape unharmed or they are farmed in aquaculture plants that are built on destroyed mangrove forests that then leach pollution and kill nearby coral reefs.

The United States requires all shrimp trawlers to be outfitted with TEDs and regulates where they can trawl. The US has higher standards for pollution laws and laws protecting shore habitats that result in less damage to the environment. Choose US shrimp ONLY!

If you would like more information - check out SeafoodWatch, a non-profit organization that independently evaluates fisheries for their sustainability and environmental impacts.

This article also has some really nice information and photos. Sustainable seafood.