Effects of Trawling and Dredging on Seafloor Habitat (2002) / Chapter Skim
Currently Skimming:
4 Habitat Mapping and Distribution of Fishing Effort
4 Habitat Mapping and Distribution of Fishing Effort
Pages 30-47
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From page 30... ...
In most areas, mapping of habitats and fishing effort has been done at a relatively large scale compared to the smaller scale at which ecological effects are described. Dredge and trawl fishing grounds cover hundreds of square kilometers, but most study areas are <1 km2.
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From page 31... ...
Biologic features, the presence of seagrass beds, kelp forests, and coral reefs, for example, also define habitats. World Wildlife Fund Canada has sought to apply the concepts of terrestrial habitat mapping to Canadian marine waters (Roff and Taylor, 2000~.
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From page 32... ...
However, for most of the continental shelf where most federally regulated fishing activity occurs, bathymetric maps with 2 m contours offer the highest resolution available. This scale is insufficient for some fishery management purposes because some features (e.g., ledges, boulders, depressions)
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From page 34... ...
In some areas, the databases can provide a large-scale estimate of substrate types, but the distribution of existing sediment samples is highly variable. Some areas, such as the Atlantic continental shelf, have been systematically sampled approximately every 10 nautical miles (Poppe and Polloni, 2000~.
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From page 35... ...
HABITAT MAPPING AND DISTRIBUTION OF FISHING EFFORT 35 FIGURE 4.3 Map showing distribution of sediment samples catalogued in U.S. Geological Survey database for the Atlantic Continental Margin (Poppe and Polloni, 2000~.
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From page 36... ...
Fishing effort data superimposed on habitat maps, for example, would help identify regions where more study is needed or where problems could arise. Presentation of data sets of differing scales is not a problem in GIS: The user can zoom in where the data density warrants a close-up view or zoom out for a regional view.
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From page 37... ...
These estimates are based on data provided by the various state and federal fishery management agencies and make several assumptions regarding the areas swept, the estimated total fishing area, and the total number of trawl or dredge tows, as described below. There is considerable regional variation in the collection of data on bottom trawling and dredging activities conducted on the continental shelf and slope off the U.S.
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From page 38... ...
Trawling in the Pacific, North Pacific, and New England regions is directed primarily at groundfish and pandalid shrimps; bottom trawling in the Gulf of Mexico and off the southeastern states is directed primarily at various warmwater shrimp species, with some seasonal effort directed at crabs or scallops. The fishing gear used to harvest shrimp is lighter than that used for most groundfish.
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From page 39... ...
Although the effort data have not been collected in recent years, this pattern is also likely for bottom trawling off the Atlantic coast as a result of more restrictive regulations during the late 1990s. Reductions in effort have followed declines in stock levels, closure of areas to trawling, and other management measures (Pacific Fishery Management Council, 2000~.
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From page 40... ...
The scallop fishery in 2000 was the most valuable in the region. New Bedford is a major scallop port, producing 55 percent of scallops landed in the New England and mid-Atlantic regions (New England Fishery Management Council, 2000~.
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From page 41... ...
. 1 = National Marine Fisheries Service, 2001b; 2 = Aguirre International, 1996; 3 = New England Fishery Management Council, 2000; 4 = South Atlantic Fishery Management Council, 2001; 5 = South Atlantic Fishery Management Council, 1996; 6 = South Atlantic Fishery Management Council, 2000; 7 = Thomas et al., 1995; 8 = Good et al., 1987; 9 = Thomson, 2001; 10 = Pacific States Marine Fisheries Commission, 1999; 11 = Leet et al., 1992; 12 = Pacific States Marine Fisheries Commission, 1998; 13 = Radtke and Davis, 2000; 14 = Hiatt et al., 2001; 15 = Alaska Department of Fish and Game, 2002.
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From page 42... ...
Effort Distribution and intensity Fishing effort in the New England region was analyzed based on port agent interviews and port landings, for the period 1991-1993. The effort data for various regions of the U.S.
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From page 43... ...
In 1985, 95 percent of the 0.5° statistical blocks were swept less than once a year by bottom trawls, and, on average, only 12 percent of the region's seabed was swept in 1985. Analysis of similar data for the scallop dredge fishery indicates that the effort also was considerably less intense than in New England; no statistical areas were swept more than once a year.
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From page 44... ...
In one 1995 data set from North Carolina, a localized, special inshore shrimp management area was documented to be swept more than 4 times by shrimp trawl gear. Most of the continental shelf off the North Carolina shore is hard rocky bottom inhabited bY the snapper-grouper complex of fishes, but because North Carolina regulations prohibit trawl and dredge fishing vessels from possessing fish in this complex no effort is reported in this area.
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From page 45... ...
Other fisheries in which groundfish trawl fishery participants take part include shrimp, prawn trawl, or crab pot fisheries in Northern and Central California. Trawl fisheries in Southern California are seldom pursued in combination with other gear types (Thomson, 2001~.
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From page 46... ...
EFFECTS OF TRAWLING AND DREDGING ON SEAFLOOR HABITAT North Pacific: Alaska Fishery Descriptions: Finfish Bottom Trawl (Flounder, Yellow Fin Sole, Rock Sole, Rockfish, Atha Mackerel, and Cow, Scallop Fishery Dredge, and Shrimp Trawl (Otter and BeamJ The continental shelf and slope region off the coast of Alaskan coast constitutes one of the most extensive fishing grounds in the world. Bottom trawling in the Bering Sea began in 1929 with a Japanese exploratory operation; commercial operations began during the 1930s and early 1940s.
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From page 47... ...
CONCLUSION Domestic trawl and dredge fisheries are conducted along most of the continental shelf and slope adjacent to the United States, although the level of fishing effort, and hence the amount of area affected, varies widely by region and by the spatial distribution of the fishing grounds. Groundfish trawls dominate the Alaska, Pacific coast, and New England fisheries; shrimp trawling is the major fishery in the Gulf of Mexico and in the coastal southeast Atlantic.
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