The Puretic power block is a special kind of mechanised

winch A winch is a mechanical device that is used to pull in (wind up) or let out (wind out) or otherwise adjust the tension of a rope or wire rope (also called "cable" or "wire cable"). In its simplest form, it consists of a spool (or drum) attache ...

used to haul nets on

fishing vessel A fishing vessel is a boat or ship used to catch fish in the sea, or on a lake or river. Many different kinds of vessels are used in commercial, artisanal and recreational fishing. The total number of fishing vessels in the world in 2016 was ...

s. The power block is a large powered aluminium

pulley A pulley is a wheel on an axle or shaft that is designed to support movement and change of direction of a taut cable or belt, or transfer of power between the shaft and cable or belt. In the case of a pulley supported by a frame or shell that ...

with a hard rubber-coated

sheave A sheave () or pulley wheel is a grooved wheel often used for holding a belt, wire rope, or rope and incorporated into a pulley A pulley is a wheel on an axle or shaft that is designed to support movement and change of direction of a ...

. While many men were needed for the back-breaking work of hauling a

purse seine Seine fishing (or seine-haul fishing; ) is a method of fishing that employs a surrounding net, called a seine, that hangs vertically in the water with its bottom edge held down by weights and its top edge buoyed by floats. Seine nets can be dep ...

manually, the same work could be done by fewer men with a power block.Schmidt PG (1959) "The Puretic power block and its effect on modern purse seining". I
''Modern Fishing Gear Of The World 1''
pp. 400–414. Editor Hilmar Kristjohsson,

FAO The Food and Agriculture Organization of the United Nations (FAO)french: link=no, Organisation des Nations unies pour l'alimentation et l'agriculture; it, Organizzazione delle Nazioni Unite per l'Alimentazione e l'Agricoltura is an intern ...

, Rome. The Puretic power block revolutionized the technology of hauling

fishing net A fishing net is a net used for fishing. Nets are devices made from fibers woven in a grid-like structure. Some fishing nets are also called fish traps, for example fyke nets. Fishing nets are usually meshes formed by knotting a relatively thin ...

s, particularly purse seine nets. According to the Food and Agriculture Organization of the United Nations (FAO), "no single invention has contributed more to the success of purse seine net hauling" than the power block, which was "the linch-pin in the mechanization of purse seining".

: Fishing Equipment
Power block
Rome. Retrieved 28 May 2009.

History

The power block was invented by a Croatian fisherman, Mario Puratić, and patented in 1953. In English, Puratić is usually incorrectly spelt Puretic, sometimes Puretich. While he was working as a tuna and sardine fisherman from San Pedro, California, Puratić started thinking about the difficulty of hauling seine nets. The original power block he designed was essentially a simple winch which used a V-shaped roller coated with hard rubber. It was suspended from a davit, and powered from the warp end of the winch by a looping rope. In 1954, the power block was trialled by American purse seiners in the Pacific. They have evolved since then, and nowadays power blocks are powered by hydraulic pumps. Their speed, torque and direction can be remotely controlled from the bridge during operations. As a result, retrieving the net is safer and requires less manual work.Bardarson, HR (1971) "Deck Equipment for Purse Seining". In ''Modern Fishing Gear Of The World 3'', pp. 283–287, Editor Hilmar Kristjohsson,

, Rome
Download PDF (56MB)
/ref> Other important innovations of the same period were the development of synthetic fishing nets and

sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect o ...

detection devices. The combination of the automated power block hauling synthetic nets with sonar sensing revolutionised the industry. The use of power blocks was found to have further advantages. It is possible to fish in rougher weather with the power block, because the steady force exerted by the net stabilizes the vessel. When deployments are made which miss the schooling fish, the net can be rapidly retrieved and redeployed on the same school. The power block also makes it easy to get nets aboard in emergencies, such as a sudden shift in tides or winds, or shark attacks on the catch and net. On the other hand, the increase in the effectiveness of purse seine fishing led to herring schools choosing to school deeper in the water. Nets that could operate in deeper water needed to be bigger and heavier. That in turn meant bigger vessels, which pushed the smaller herring vessels out of business.

Details

Seine fishing industries rapidly recognized the value of the power block, and by 1960, most northern seine vessels were using the power block. Nowadays power blocks come with dozens of configurations and sizes. They are installed on over twenty thousand

s across the major purse seining

fisheries Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

around the world. These fisheries haul huge

schools A school is an educational institution designed to provide learning spaces and learning environments for the teaching of students under the direction of teachers. Most countries have systems of formal education, which is sometimes compulsor ...

tuna A tuna is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae (mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bullet tuna (max length: ...

salmon Salmon () is the common name for several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the family (biology), family Salmonidae, which are native to tributary, tributaries of the ...

herring Herring are forage fish, mostly belonging to the family of Clupeidae. Herring often move in large schools around fishing banks and near the coast, found particularly in shallow, temperate waters of the North Pacific and North Atlantic Oceans, i ...

sardine "Sardine" and "pilchard" are common names for various species of small, oily forage fish in the herring family Clupeidae. The term "sardine" was first used in English during the early 15th century, a folk etymology says it comes from the Ital ...

anchovies An anchovy is a small, common forage fish of the family Engraulidae. Most species are found in marine waters, but several will enter brackish water, and some in South America are restricted to fresh water. More than 140 species are placed in 1 ...

and

menhaden Menhaden, also known as mossbunker and bunker and "the most important fish in the sea", are forage fish of the genera ''Brevoortia'' and ''Ethmidium'', two genera of marine fish in the family Clupeidae. ''Menhaden'' is a blend of ''poghaden' ...

from the sea, accounting for a large part the world total fish catch. Between 1969 and 1979, the Puretic power block was pictured on the reverse side of Canadian five dollar banknote issues. In 1975 Mario Puratić was given the National Inventor of the Year Award by the Intellectual Property Owners Education Foundation for his invention of the power block.Inventor of the Year Award: Past Awards
Intellectual Property Owners Education Foundation.

Notes

{{fisheries and fishing Fishing equipment Croatian inventions