Monday, October 31, 2016
One the major problems with most commercial fisheries is the amount of bycatch. Bycatch is anything caught in the net that you do not want. This could include edible fish that your company is just not equipped to process.
Most organisms brought up in nets as bycatch do not survive because they are crushed or drowned. Sea turtles and dolphins sometimes get swept into nets and drown because they cannot make it to the surface to breathe.
Most scientists and fisherman agree that the oceans have been and are being overharvested. People may not like regulations, but without regulations, many fish species that we used to commonly consume would be extinct.
There are many ways to harvest fish. If you want more information, check out the links at Monterrey Bay Aquarium's Seafood Watch Organization.
Thursday, October 27, 2016
In the animal kingdom, males are typically brighter and more colorful. The males are trying to prove to the ladies that they have good genes, they are disease free, and they can escape predators.
Larger males can win contests against other males also proving their good genes. Though the males show off, it is the female's choice when she ultimately makes a decision. It is possible for a female to reject all males and choose none.
Differences in size and coloration indicate that there is female choice, the female will choose a male to fertilize her eggs and in most cases, his job is done, and she leaves to finish the baby-forming process. All she wanted was his genes.
When a large group of organisms all spawn at the same time, the organisms rely on luck and statistical chance for genetic variation. Males and females will look similar because there is no choice involved.
When males and females work together and take an equal role in raising young or protecting eggs, the males and females tend to look more similar. They look similar because of their equal roles and because the choice is longer-lasting. She is looking for more than just a pretty face (and pretty faces in the animal world do not indicate good egg care or being able to provide nesting materials, food, etc).
Differences in size between males and females varies widely. There is no set rule for who will be bigger, but there is usually a clear reason as to why one of them is bigger. Males can be bigger because they fight other males, because they have to guard eggs, or other reasons. Females can be bigger because they have to carry and nourish a fetus, carry and develop eggs, protect babies, or other reasons. To know why a male is bigger or a female is bigger the biology and reproductive strategies have to be understood.
Wednesday, October 26, 2016
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. The gamestes meet and mix producing fertilized eggs that develop into meroplankton 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.
Some fish do pair bond. In these instances one or both fish will guard the eggs until they hatch into baby mero-plankton, and then once again, the fish fry on their own. There are very very few fish that provide juvenile care.
In seahorses and their relatives, the female transfers the eggs to the male to care for until they hatch. He attaches them to his belly (or into his pouch) and once that set hatches, she gives him another to raise. This allows the seahorses and their relatives to constantly produce offspring. This photo is of a male leafy sea dragon carrying an egg mass (pink).
Tuesday, October 25, 2016
Many fishes are identified by looking at or into the mouth. The number of mouth-types exhibited by different species is nothing short of astonishing. Three lakes in Africa contained about 900 species of cichlids, nearly all differentiated mainly by the way their mouths are shaped. (This number is rapidly dwindling, by the way, as the cichlids in these lakes are driven to extinction). Cichlid mouths are variously adapted to eat other cichlids' eggs, scales pulled from fishes' living bodies, algae from rocks, tiny invertebrates, and many other forms of food. The arrowana of South America has a mouth adapted for spitting water with precision at insects perched on overhead branches. Parrotfish mouths have evolved to look and act like beaks, which they use to grind at coral, making the sand that surrounds coral reefs. Seahorses and pipefish have tubular mouths for sucking in small prey in narrow places like a vacuum cleaner. SOURCE
Body shape also tells you a bit about a fish. Com- pressed fish have flash and look skinny and can only be found in slow moving waters like coral reefs. Fusi-form fish are tapered like footballs and are very streamlined for constant fast swimming. Depressed fish are benthic and squashed looking. Eel shaped fish are poor swimmers and live on the benthos or in cracks and crevices.
Here is a website you can use to identify shapes - realize they are named a bit differently than how I do in class.
Monday, October 24, 2016
Pictured to the right, you can see five lamprey mouths and one lamprey head with blue eyes and seven gill holes.
Jawless fish include lampreys which are parasites and hagfish which are detritavores. Neither one will ever win a beauty contest.
Hagfish make slime to escape their predators... and it is quite gross. So gross that even they don't like it... so they tie their body into a knot to squeegee the slime off of themselves after evading a predator.
Monday, October 17, 2016
Most people are familiar with an orange sea star because on the east coast, that's all we've got. On the west coast and in other places around the world, it is easier to find a variety of sea stars in other colors and with different amounts of legs.
Sea stars have powerful tube feet that use water suction to open molluscs. When they eat molluscs, they actually stick their stomach into the shells of the mollusc, digest it, and then put their stomach.
Feather stars and basket stars both have crazy looking legs that they wave around to filter feed. Sea urchins and sand dollars are both covered with protective spines and eat with a scraping mouth called Aristotle's Lantern.
Sea cucumbers have lost most of their exoskeleton and are a bit squishier than other echinoderms. Sea cucumbers are important detritus eaters on the sea floor. When attacked by predators they will expel their guts as a meal for the predator as they make a get away. Sea cucumbers are able to regenerate these guts over time.
Thursday, October 13, 2016
If you look at a diagram, barnacles are like little shrimp glued on their backs with a white fence around them. They stick their feathery legs out to filter feed plankton. They are plankton for a while and once settled and glues onto a hard substrate never move again. This makes mating difficult, but the hermaphroditic barnacles have special talents. Gooseneck barnacles have a stalk that they attach to substrates with.
- Gulf shrimp are the ones people most people are familiar with because these are the ones we eat!
- Shore shrimp live in sea grasses, are fairly small and clear, and are not commercially harvested because no one would make any money.
- Snapping shrimp (or pistol shrimp) have slightly larger claws and can use them to make sonic waves to stun their prey with sound.
- Mantis shrimp whack their prey with arms that can unfold and strike lightning quick.
- Cleaner shrimp make their living eating parasites off of fish and other sea creatures.
Wednesday, October 12, 2016
- Blue Crabs are found in the Chesapeake Bay. They are very agressive, like to pinch, but are good to eat. They have a pointy-ended shell and swim fins. (you can kind of see the swim fins on the last leg of the crabs on the right)
- Spider Crabs have a rounder body shape, often a bumpy shell that will grow algae for camouflage, and longer more spindly legs. Spider Crabs include snow crabs and king crabs like the ones seen on Deadliest Catch. A decorator crab is a kind of spider crab that attaches stuff to its bumpy shell to blend in.
- Fiddler Crab males have one claw that is a lot bigger than the other. This is for impressing the ladies, and used to show dominance over other males.
- Hermit Crabs have a weak exoskeleton and thus protect it with a stolen mollusc shell. They have adapted to this lifestyle and have modified back legs that hook on the inside to hold the shell on and one claw that is slightly larger to use as an operculum.
Tuesday, October 11, 2016
Wednesday, October 5, 2016
Tuesday, October 4, 2016
Cephalopods are characterized by their large well developed eyes, numerous tentacles, a parrot like beak in the center of the tentacles, and well developed chromatophores in their skin that allow them to change color.
We watched numerous videos today to see and understand how and why cephalopods make ink clouds, to see how an octopus can swim with jet propulsion or use its tentacles to crawl around, and we also saw how a octopus can eat a shark!
For more information about cephalopods, check out CephBase and the Australian Cephalopod Research page.
Monday, October 3, 2016
Sometimes my classes get a close up look at the Limax maximus, the common garden slug, and their slimy mollusc bodies. Students will look at the two sets of tentacles (eyespots and sensory tentacles) and the hole the land slug breathes through. Some will touch it to see what the slug feels like and quite a few students will let the slug slime all over them. Way to be brave!
Slugs can be considered gross because of the copious amounts of mucus they leave behind. The mucus helps them get a better grip on surfaces and helps prevent dessication, drying out. It can also make the slug more difficult to pick up by predators. More information about slugs can be found here.
Computer Lab Etiquette
You are in the computer lab to do work for this class. If you are not doing work, then we will have problems.
Do not pack up early. Work until the bell or until MsJ says.
SAVE OFTEN. And if you save to a key, also save it to your number. If you lose it, you will have to do it again.
If MsJ asks for your attention, stop what you are doing and listen to what she has to say.
You may watch videos about your organism through reliable websites.
You may listen to music through the computer if you have your own headphones. Rule1 MsJ cannot hear it. You get one warning. Rule2 Turn it on and listen – no million clicks and constant changing. Take both ear phones out when MsJ is talking.