Seafood Harvesting - Shrimp

We started discussing marine harvesting and fishing today by talking about who harvests the most seafood (China), who eats the most seafood (China), and which people eat the most seafood pounds per person (the Maldives). Americans are about sixth on the list as far as consumption, but we are the number one consumer and importer of shrimp. Importing shrimp is damaging to the environment for two reasons.

1. Shrimp that are farmed in other countries are not as regulated as here in the states, so shrimp farm pollution is not as regulated and it damages coral reefs. Also many mangroves are cleared to build these farms.

2. US boats are required to have turtle excluder devices (TED) on trawl nets so that turtles do not get caught in shrimp nets and drown. Other countries do not regulate this and as a result catch and drown sea turtles.

To make a environmentally responsible seafood choices, choose shrimp that are farmed or caught in the US. For more sustainable seafood choices, check out Seafood Watch.

Seafood Harvesting

Netting is the most popular method of commercial fishing because a lot of fish can be caught in short amount of time without a lot of effort.

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.

Sexual Dimorphism

Sexual Dimorphism is when males and females exhibit different characteristics. These usually involve, color, size, behavior, and other appendages. 

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.

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. 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).

Fish Bodies and Shapes

Today in class we discussed fish mouth shape and body shape and what they mean about the fish.

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

Fish with forward facing mouths eat what is in front of them - no surprise. Downward mouths eat algae, prey below them like crustaceans and molluscs, or they take in mouth fulls of gravel, eat the particles, and spit the gravel back out. Upward facing mouths indicate the fish eats prey above them - typical of benthic ambush predators. There are also bills and beaks. Bills are long and skinny used for poking in crevices and eating plankton one at a time. Beaks are used for chomping and can be seen on the parrotfish, a fish that chomps on the algae growing on the surface of dead coral. Fish can also have very large mouths common on filter feeders and fish that swallow large prey whole. Fish also have teeth - a surprise to many - and come in many shapes and size.

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.

Jawless Fish

Today we discusses jawless fish. Jawless fish are primitive fish with a notochord instead of a backbone and a flat rasping mouth that cannot close like ours. As a result thes fish cannot bite... only scrape and hold on.

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.