Ronholt, L: Distribution and Relative Abundance of Commercia

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Ronholt, L: Distribution and Relative Abundance of Commercia

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O knihe

Excerpt from Distribution and Relative Abundance of Commercially Important Pandalid Shrimps in the Northeastern Pacific Ocean

A Gulf of Mexico shrimp trawl (schaefers and Johnson, 1957) measuring 41 feet 3 inches along the head rope was first used in 1955-56 off Washington. It subsequently became the major exploratory shrimp gear. The trawl was attached immediately behind the otter doors, which were fastened to a single warp line by a 25-fathom bridle. Each otter door was 2 feet high by 5 feet long. The net was constructed of 1 l/2-inch stretched mesh cotton webbing.areas shown on charts as having soft mud bottom. When the echo sounder indicated that the bottom was level enough to permit trawl ing, the net was fished. Considerable gear damage often resulted, for the echo sounder recording did not always enable us to interpret the bottom type correctly. During more recent cruises the use of a high-resolution, low frequency echo sounder provided better defi nition of bottom configuration and type, thus reducing gear damage and destruction (hitz, Johnson, and Pruter, In most instances exploratory drags were 30 minutes long.

Known commercial shrimp grounds were not fished except when it was necessary to establish that the gear was functioning prop erly.

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