Prof S D Rathod

B N Bandodkar College of Science

Thane, Maharashtra, India

LifeBuoy

Life saving raft and boat

Inflatable Yatch Inflatable Boat

Flash signal light High

speed rescue-boat

Rocket Flares and horns

signaling

Radio devices

GPS Personal Locator

Beacon is the perfect

solution

Nautilus Lifeline GPS

Marine Radio for Divers or

Boaters

Radio Devices

Remote Sensing

Satellite System The open ocean

provides a tough

work

environment, it

is vital that

personnel and

vessels stay in

touch at all

times & help in

improvement of

crew moral and

entertainment.

Oceanographic Instruments

Sonar fish finders

Eco-ranging

Fish finding

Nansen’s reversing bottle

Nansen bottles, invented by the

Norwegian oceanographer Fridtjof

Nansen, are cylindrical containers that

sample sea temperature and salinity.

The bottle, more precisely a metal or

plastic cylinder, is lowered on a cable

into the ocean, and when it has reached

the required depth, a brass weight called

a "messenger" is dropped down the

cable. When the weight reaches the

bottle, the impact tips the bottle upside

down and trips a spring-loaded valve at

the end, trapping the water sample

inside. The bottle and sample are then

retrieved by hauling in the cable.

Peterson’s grab

Device is used by aquatic and marine biologists. Since 1930 the Petersen grab has been used in fresh water for collecting macroscopic fauna in sand, gravel, marl, clay or clay combinations. If used in salt water, it must be painted for protection. Since it has been widely used over 6 decades, it is ideal for comparing samples with data collected previously by a Petersen grab.

Vent holes permit water to flow through while the grab is being lowered, minimizing diagonal movement as well as reducing the frontal shock wave generated by descent. Jaws close clamshell fashion

Dredges Similar to a beam trawl, a dredge

consists of a rugged triangular steel frame and tooth-bearing bar, behind which a mat of linked steel rings is secured.

A heavy netting cover joins the sides and back of this mat to form a bag in which the catch is retained. Shellfish are raked out of sand or gravel and swept into the bag.

Several dredges are towed together from a tow bar and larger vessels generally tow two bars, one from each side of the vessel. In suction dredges and hydraulic dredges, water is shot into sediments and displaced shellfish are collected in a mesh bag (hydraulic) or sucked to the surface through a pipe (suction).

Scallop Dredge Scallop dredging involves using

a dredge that consists of a metal frame with spring-loaded teeth to which a chain-mesh bag is attached.

The dredge is towed over seabed habitats, where the teeth rake the seabed disturbing the scallops. This gear is extremely robust and can be used over much harder grounds than traditional trawls. As a consequence, scallop dredges can severely damage other seabed organisms and habitats.

Clamshell bucket dredge The clamshell bucket dredge, also known as

the grab dredge, is the most commonly used mechanical dredge. the world over. This dredge may consist simply of a crane mounted on a spud barge, although most bucket dredges have a crane/barge system specifically designed and constructed for dredging.

A bucket dredge is operated similarly to a land-based crane and bucket. The crane operator drops the bucket through the water column, allowing it to sink into the sediment on contact. The loaded bucket is then lifted, causing the jaws to close, and raised through the water column. Once above the water surface, the operator swings the bucket over the receiving container (usually a barge) and lowers the bucket to release its load. The bucket dredge usually leaves an irregular, cratered sediment surface (Herbich and Brahme 1991).

Other dredges

Dredge and power shovel : Dredges

There are two types of dredge: the mechanically operated and hydraulically operated. Mechanical dredges, which are similar to land-based excavating machines, were the first to be developed and can be classified as dipper, grapple, or ladder dredges.

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