Bivalves ~ New Jersey Scuba Diving

Bivalves

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All of these bivalves are filter feeders. The other major group of mollusks is the Gastropods or snails. Squid and octopus ( cephalopods ) are mollusks too, but they don't behave like other mollusks, so I included them elsewhere. Teredos are bivalves that have evolved a worm-like wood-boring habit.

Clams

The inshore wrecks are sometimes surrounded by the empty shells of Surf Clams Spisula solidissima, right, to 7" across. Large numbers of the white shells also wash up on beaches. Surf Clams are found subtidally down to 100 feet ( which makes you wonder why they are called surf clams. )

Tiny angel wing-shaped Coquina clams Donax variabilis less than 1 inch long do live in the surf, on wave-tossed sandy beaches.

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Mussels

Mussels are found everywhere, attached to any solid substrate. Mussels are to the sea what grass is to suburbia. Mussels lack the muscular foot of clams or the large hinge muscle of scallops. Instead, they have a "beard" of tough fibers near the hinge with which they attach themselves.

The Blue Mussel Mytilus edulis, to 4" is the edible mussel. The similar Horse Mussel Modiolus modiolus grows to 6", and is considered inedible. Both types are found from the intertidal zone down to the depths. See entry on barnacles.

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Scallops

Scallops can swim in spurts by clapping their shells. Water is ejected backward through openings on either side of the hinge, propelling the scallop in the opposite direction - surprising to see for the first time. When not jetting around, they settle into evenly-spaced shallow pits in the sand.

The Deep Sea Scallop Placopecten magellanicus (right) grows to 8" and is found offshore, generally in water over 100' deep. The smaller but equally edible Bay Scallop Aquipecten irradians, to 3", is found in bays and protected shallow waters. The Bay Scallop has a deeply ribbed shell, while the Deep Sea Scallop has many tiny ribs.

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Oysters

The Common Oyster Crassostrea virginica, to 10", is the basis of a major fishery, but they occur only in turbid brackish estuaries, conditions generally not conducive to scuba diving. Oysters once dominated the bottom fauna in our local rivers and bays, but are now all but extinct due to pollution and disease. Attempts are being made to reintroduce them in places, and perhaps someday even re-establish the fishery. Disease-resistant Asian Oysters may be the key to this.

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Mermaid's Purse

The Mermaid's Purse is not an invertebrate at all - it is a fish egg capsule. The egg capsule of a skate or ray, to be precise. The "horns" are to secure the capsule in seaweed. You may find one with a baby skate growing inside, but most are empty. They are included here with bivalves because they are often found scattered around the bottom like shells, up to 3" long. They certainly don't look like fish!

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Regulators - Servicing & Warranties

The "Regulator Tax" and the Buddy System

You should probably just skip this section

The scuba industry has successfully convinced the diving public that annual servicing of regulators is essential for your safety. Actually, at $50-$100 per regulator per year, annual servicing of regulators is far more essential to their bottom line than it is to your safety. Am I so cheap that I would risk my life to save less than $100? Not really.

All this is mixed up in business, economics, liability, and the fallacious buddy system. As you know, in the buddy system your buddy is theoretically your backup emergency air supply underwater, insuring not only against out-of-air situations, but also against equipment failures, and therefore you need only one tank and regulator. In keeping with this theory, you are sold a wholly inadequate breathing system with no built-in redundancy at all. Then, to try to reduce the inherent danger of diving with such a system, or perhaps just the legal liability in promoting it, you are then "required" to have it "serviced" at least once a year, whether it needs it or not. In fact, this is the icing on the cake for the industry, since such servicing is far more profitable than sales! The real purpose of all this is to lower the entry cost of diving by several hundred dollars, expand the customer base as rapidly as possible, and maximize revenues, and all this is done at the expense of true safety. In an industry that professes to be obsessed with safety at all costs, this hypocrisy is almost beyond belief. ( I'm not saying your local dive shop is evil, but he'll go right along with the industry-standard because everyone else does, and he needs to make a living. )

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