OTTER TRAWL A Wings, square, belly Cod end B Wings, square, belly Head rope Rib lines Hanging of Both Nets Head rope Footrope 48 thread, 4" mesh cotton webbing 60 thread, 41" mesh cotton webbing 71 feet plus eyes, of " 6x19 galvanized wire rope 94 feet plus eyes, of " 6x24 galvanized wire rope wrapped with 27-thread manila line. 7 feet including eyes, of galvanized wire rope wrapped with 6-thread manila line. 8 each, of 27-thread manila line, one along each seam and one along top and bottom center, and one from the corners at each bosom on top and bottom running diagonally to join alde rib lines. 45M 28 FEET 68M 5 BARS 1MESH W os Fig. 4 Details of a standard 400-mesh eastern-type otter trawl used for bottom-fish explorations off Southeastern Alaska. growths of Alaska coral2 were encountered over much of the grounds fished, but these areas proved productive in spite of the nuisance of the minor gear damage sometimes incurred. Clear Trawling Bottom: One of the Another large area free of snags was located off Iphigenia Bay. This area is somewhat pear-shaped being about 5 to 10 miles wide inshore and from 15 to 20 miles wide in the deeper offshore part. The bottom topography is characterized by a trough or gully which extends offshore from Iphigenia Bay and fans out to form a deep basin at its outer extremity. Green mud and sand were found throughout the region with some gravel noted on the southeast slope of the basin and in parts of the gully. A total of 20 otter-trawl drags was made in this area at depths ranging from 87 to 165 fathoms with minor gear damage experienced during only two drags which were made on the north slope of the gully near Iphigenia Bay. Fig. 5 Chart depicting: (1) are as free of snags, (2) grounds where Alaska coral growths were encountered, and (3) areas unsuitable for trawling. A small clear basin, about 6 miles in diameter, lies 5 to 11 miles south of Cape Bartolome. It is separated from the Baker Island clear grounds mentioned above by 2/Alaska coral is a soft coral and is related to the tropical soft corals (sea fans etc.). It is not similar to the stony corals normally encountered in tropical waters. a narrow strip of uneven bottom. Two otter-trawl drags and 5 shrimp-trawl drags were made at depths from 84 to 93 fathoms in this basin without encountering obstructions. Another small clear area was found next to the western boundary of the halibut nursery grounds off Noyes Island. The bottom in this region is composed of green mud and sand. Five otter-trawl drags made in this area at depths from 77 to 97 fathoms encountered no snags. Other areas found to be free of snags are shown in figure 5. Alaska Coral: A large amount of the ocean bottom off Southeastern Alaska would be excellent for trawling except for considerable growths of Alaska coral. This growth Fig. 6 Depth recordings made aboard the John N. Cobb off Southeastern Alaska. (A) Tracing made during drag which hung up solid, probably on Alaska coral. (B) Typical bottom trace made in gully between Forrester and Dall Islands. (C) Tracing made in Dixon Entrance during drag which resulted in the loss of the complete net and one door. is not easy to detect with commercial echo-sounding equipment (fig. 6-A), but is prominent enough to hang up a trawl and stop a vessel, even one the size of the John N. Cobb. Slight gear damage usually resulted from such hang-ups and occasionally no damage at all occurred to the net. Some hang-ups, however, resulted in damage requiring several manhours to repair the gear. In addition to actual specimens taken in the net (fig. 7), the type of gear damage experienced gave further evidence that Alaska coral was the chief cause of snagging. The upper leading edge of the net, particularly on the wings, received the most wear; and broken hangings, lost floats, badly chafed "dandy lines," and chafing of the headrope were common types of damage suffered. A substantial portion of the localities showing Alaska coral in figure 5 are trawlable, although a risk of incurring minor gear damage exists. It was sometimes found possible to work the gear free from coral snags and continue towing. Evidently the fishing ability of the net is not greatly affected by the presence of Alaska coral. Two drags which encountered snags yielded catches of 3,000 and 3,700 pounds of Pacific ocean perch. Several other drags which hung up solidly caught fish at rates in excess of 1,000 pounds an hour. Fig. 7 Alaska coral picked up during exploratory trawling by the Tordenskjold. UNTRAWLABLE AREAS: Localities found unsuitable for trawl operation included: (1) all areas explored inside the 50-fathom depth contour, (2) Iphigenia Bay, (3) inside the 100-fathom depth contour immediately south of Hazy and Coronation Islands, (4) the 110-fathom edge off Cape Bartolome, and (5) the continental slope at depths ranging from about 200 to 400 fathoms. The gully and adjacent slopes between Forrester and Dall Islands also offered little in the way of suitable trawling bottom (fig. 6-B). Although navigational charts and depth recordings (fig. 6-C) indicated favorable trawling bottom in Dixon Entrance east of Learmonth Bank at depths of over 100 fathoms, of the two drags made, one resulted in the loss of the complete net and one door. Because of strong currents, speed and directional control were difficult and it was apparent that not enough time was available to obtain significant results. A careful analysis of currents and tides would be necessary along with the possibility of having to wait for slack water to accomplish the actual trawling. FISHING RESULTS Positions of otter-trawl and shrimp-trawl drags made during the two cruises are shown diagrammatically in figures 8 and 9, and the catches and particulars for each drag are given in tables 2, 3, and 4. Drags in which snags or torn gear were encountered have been plotted on the charts for quick reference. Pacific ocean perch were caught in commercial quantities during both explorations with the best catches in the spring; and several good catches of black rockfish |