. Commercial fisheries review. Fisheries; Fish trade. January 1961 COMMERCIAL FISHERIES REVIEW 31 Systematic surveys of the bottom with a high- resolution, low-frequency echo-sounder re- sulted in the discovery of some fishable ground of soft bottom located within rocky regions a- voided by commercial fishermen. Test drags made with a Gulf-of-Mexico shrimp trawl on the soft-bottom areas produced some catches of pink shrimp in commercial quantity. The best drag of the cruise, made off the Umpqua River in 90 fathoms of water, yielded 650 pounds of pink shrimp in one-half hour of fishing. A num-
. Commercial fisheries review. Fisheries; Fish trade. January 1961 COMMERCIAL FISHERIES REVIEW 31 Systematic surveys of the bottom with a high- resolution, low-frequency echo-sounder re- sulted in the discovery of some fishable ground of soft bottom located within rocky regions a- voided by commercial fishermen. Test drags made with a Gulf-of-Mexico shrimp trawl on the soft-bottom areas produced some catches of pink shrimp in commercial quantity. The best drag of the cruise, made off the Umpqua River in 90 fathoms of water, yielded 650 pounds of pink shrimp in one-half hour of fishing. A num- ber of other one-half hour drags producedfrom 200 to 500 pounds of shrimp. The exploratory catches were generally higher than those con- currently made by commercial shrimp fisher- men on previously known grounds in the same general region. Maximum concentrations of shrimp were found at depths from 85 to 95 fathoms on green mud bottom, with good catches also in water as shallow as 72 fathoms. Test drags were made within the depth range from 50 to 110 Area of shrimp explorations M/V John N. Cobb Cruise 48 (October-November 1960). The size of the shrimp varied within the region, ranging from 70 to 140 heads-on count per pound. Samples of the catches showed that two- and three-year-old shrimp were dominant, withafewone- andfour-year- olds also present. The procedure used to survey the areas was as follows: (1) Sounding transects were made with a high-resolution, low-frequency echo-sounder. (2) On the grounds indicated by the echo-sounder as being free of snags and having a soft bottom, a series of drags from shallow to deep water were made until the center of abundance of the shrimp was located. This contour was then followed up and down the coast, when possible, until shrimp were no longer taken. Drags were then made again from shallow to deep water to insure that the center of abundance of the shrimp had not shifted. (3) Samples of shrimp from each drag were measured a
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