Appendix B Regional Distribution of Fishing Effort
Commercial fisheries using trawls for groundfish and shrimp and dredges fo\r scallops take place in the 6 fishery management regions of the contiguous United States. The information collected about those fisheries by the National Marine Fisheries Service (NMFS) and state agencies varies in quality and content from one region to another. Relatively good qualitative information is available for bottom trawl and scallop dredge fisheries, and detailed information on the location of bottom trawling, the duration of tows and the associated catches is available for most of the intensively trawled areas. However, the methods of data collection, the details maintained, and the geographic resolution differ. Four of the six regions have sufficient information about the distribution of trawling effort during the 1990s to allow depiction of fishing effort by geographic statistical area. The material in this appendix was collected and prepared by Natural Resources Consultants. It appears in this report with their permission.
ATLANTIC SEABOARD (FIGURES B.1–B.5)
Information about the trawl effort off New England and the mid-Atlantic states was provided to the committee by the Northeast Fisheries Science Center. Between 1964 and 1993 catch and fishing effort data were collected through a voluntary program using NMFS port agents in various fishing communities from Maine to Virginia. The system relied on interviews with captains of a portion of the fleet. Additional data were collected from weigh-out (dealer) transactions, auction sales, and from trucking companies. The objective of the program was to interview a large portion of the offshore-vessel operators, because their vessels were likely to fish in different areas from one trip to the next (or even on the same trip). Inshore, fixed-gear fleets that were more likely to fish the same grounds were thus interviewed less frequently.
For each vessel’s trip interview, the port agent assigned a 10-minute square (10′ latitude by 10′ longitude) that best characterized the location of landings from the trip. When data were available, the trip landings were split into several 10-minute squares, particularly if the catches of various species changed during the trip. All non-interviewed trips were assigned to the most appropriate quarter-degree square, based on the vessels known fishing patterns, port landings, or vessel location, as supplied by captains. Thus, the effort database is a combination of interviewed trips wherein data are located to 10-minute squares and noninterviewed trips wherein the data were assigned to quarter-degree squares. Effort data are defined in 24-hour days, not including steaming time.
SOUTH ATLANTIC COAST (FIGURES B.6–B.7)
Fishery data along the southeastern coast of the United States has been collected by different agencies for the past 100 years. NMFS has been involved in fisheries data collection in the region for a considerable period, either as the sole entity, or in cooperation with state agencies. Unfortunately, because of the lack of effective regulations, states have been handicapped and trawl effort data in many instances are not very quantitative. Current estimates of the bottom trawling effort are patchy. Only two states, Florida and North Carolina, have implemented the use of trip tickets, thus improving the collection of effort data. Those two states, along with most of the Atlantic coast states, are developing a coast-wide, unified data collection system. In 1998–1999, there were 15,067 trawl trips by 901 licensed vessels reported off North Carolina.
In recent years more than 900 vessels have been involved in the North Carolina trawl fishery. About 82 percent of shrimp trawl trips during 1994–1997 occurred in estuaries. Occasional catches of shrimp are taken in the ocean areas and offshore vessels land close to a quarter of the state’s shrimp landings. Most of the shrimp and crab trawling along the North Carolina coast occurs close to the beach, generally at depths <18.3 m.
GULF OF MEXICO (FIGURES B.8–B.10)
Although there has been small-scale trawl fishing for finfish for food and industrial purposes in the Gulf, essentially all bottom trawling now is directed at harvesting various species of shrimps. Scallop dredging and trawling also occurs in the region.
NMFS began collecting standardized fishery statistics for the Gulf in l960 (catch, effort, gear, locale) using a shore-based sampling program, that more recently has been coupled with a low-level at-sea observer program. James M. Nance, NMFS Galveston Laboratory, provided the committee with detailed effort data for the Gulf of Mexico. Additional information was provided by Ecological Research Associates, Byran, Texas, a company involved in a voluntary sampling program that uses remote-sensing satellite positioning to track trawling in the Gulf throughout the year. NMFS notes four areas of shrimp bottom trawling concentration, as follows:
Subarea 1–3, middle depths off Florida;
Subarea 11, middle depths off Mississippi and Alabama;
Subareas 13–17, shallow depths off Louisiana (west delta); and
Subareas 18–19, shallow and mid-depths off west Texas.
Although the distribution of fishing effort can and does change daily, weekly, and monthly, annual averages over the 1990s did not vary much from one locality to another. Overall the bottom trawl effort declined 41 percent between the 1991–1993 and 1998–1999 periods. However, the Gulf of Mexico is still one of the most intensely bottom trawled areas off the United States. It has been noted (Sheridan, 2001) that the effort in some statistical blocks translates into a block area swept 37–75 times per year.
ALASKA (FIGURES B.11–B.32)
Data and graphs for the Alaska region were provided to the committee by Alaska Fisheries Science Center, NMFS. The data were based on observer records. Rebecca F. Reuter (Alaska Fisheries Science Center) and Cathy Coon (North Pacific Fisheries Management Council) compiled and summarized the data and provided supporting text. Jonathan Heifetz of the Auke Bay Laboratory, NMFS, provided data on the total trawl effort. Only fishery data from hauls taken when observers were onboard were included. Catcher processors and catcher vessels were included in the data summaries discussed below. Vessels longer than 38 m had 100 percent observer coverage while vessels 20– 38 m had 30 percent coverage. Thus, the smaller vessels are underrepresented in the effort distribution charts. No information was available for vessels less than 20 m.
Regardless, the observed tows are assumed to be representative of the general distribution of the total bottom fishing effort. Only the endpoints of each tow were used to summarize the data for the maps, so the lengths of the tows are not represented in the grid, and some tows extend across several grids. The trawling effort data do not include the pollock fishery, because this fishery converted to pelagic trawl gear starting in 1990 (Box 6.1). It is known that during some midwater trawling, the footrope will make contact with the seabed. However, the amount of bottom contact and the effects of that gear on the seafloor are unknown.
Over large portions of the Bering Sea (about 94,000 km2 total) there were either no observed bottom trawls or about four observed tows (averaged over two years) per 25 km2 cell per year in 1999 and 2000 (FigureB.24). In the Gulf of Alaska also, there was a reduction in the number of observed tows and in the intensity of trawling in many of the geographic cells. Closed areas, less productive grounds, and unobserved tows are responsible for much of the untrawled area. The relatively low intensity of trawling (compared with other regions of the United States) over a large part of the Bering Sea reflects the distribution of flounder populations in time and space over much of the large flats that extend out to near the continental break, the relatively high catch rate for the harvested species, and unobserved tows and the growing use of midwater trawls. Within any year there are open and closed seasons, limiting bottom trawling to only a portion of the year.
Small-scale scallop dredging occurs in several areas in the Gulf of Alaska and the Bering Sea, and a beam trawl fishery for shrimp occurs in the inside waters of southeastern Alaska, near Petersburg (Figures B.25– B.32). The Alaska Department of Fish and Game has maintained excellent records of the state’s distribution and intensity of scallop dredging.
CONTIGUOUS WEST COAST STATES (FIGURES B.33–B.37)
Information on the trawling effort off California, Oregon, and Washington was provided by the Natural Resources Consultants, the California Department of Fish and Game, the Oregon Department of Fish and Wildlife, and the Washington Department of Fish and Wildlife. The data were compiled and graphed by Karma Dunlop (Natural Resources Consultants). Oregon and Washington data are 1991–1993 and 1998–1999; California data are 1994–1996. The calculated effort distribution data and the number of tows and duration from all three states are based on log books. Some of the tows are not included in this data set because they could not be geographically resolved to the data cells. Shrimp trawl data are provided for 1979–1999. In August 2001, a compulsory observer program was implemented for California, Oregon, and Washington (Randy Fisher, Pacific State Marine Fisheries Commission, personal communication).
The intensity of trawling off the contiguous West Coast states appears relatively similar for the three states, with perhaps somewhat higher effort occurring off Washington and Oregon (the years for which data have been summarized for Washington, Oregon, and California differ). The average number of tows per year off California during 1994–1996 was 15,535. Although we do not have a 1998–1999 database for California, it is obvious from the Oregon and Washington data that the trawl effort along the West Coast declined sharply between the early 1990s and the latter part of the decade. For example, the number of blocks in the four highest effort categories off Oregon and Washington declined 36 percent, or from 102 to 68 blocks. The decline in effort is demonstrated even more dramatically by the reduction in the average number of tows per year. Between the 1991–1993 and 1998–1999 periods the number of tows declined from 28,489 to 11,487, a reduction of 60 percent in the average number of tows per year. The reduction in effort has followed declines in the abundance of target species and subsequent Pacific Fishery Management Council reductions in quotas and fishing time. The decline continued for all three states in 2000–2001 (Randy Fisher, Pacific State Marine Fisheries Commission, personal communication).
Swept-area information for the region has not been published. To provide an estimate of the affected area, preliminary calculations were performed assuming 3-hour towing times at 3 knots/hour, and a 300-foot door spread. Under these assumptions, one tow would sweep 16.4 million square feet. An average statistical block between 41° and 42° is roughly 71.7 square miles or 2.64 billion square feet. Based on these calculations, it would take about 160 three-hour tows to sweep one statistical block.
DECLINE IN TRAWL EFFORT (FIGURE B.38)
Although scientists do not have trawl effort data for all NMFS regions, sufficient data are available to document a considerable decline in trawling in Alaska, Oregon and Washington, and the Gulf of Mexico between the early 1990s (1991–1994) and later in the decade (1998–2000).