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Proposed Depredation
Order DEPARTMENT OF THE INTERIOR (DOI) Migratory Bird Permits; Proposed
Depredation Order for the Double-Crested Cormorant SUMMARY: The U.S. Fish and Wildlife Service (hereinafter Service) proposes to implement a depredation order for the double-crested cormorant. In those States in which double-crested cormorants have been shown to be seriously injurious to commercial freshwater aquaculture, and when found committing or about to commit depredations upon aquaculture stock, persons engaged in the production of aquaculture commodity stocks would be allowed, without a Federal permit, to take or cause to be taken such double-crested cormorants as might be necessary to protect aquaculture stocks. DATES: Comments must be submitted on or before August 22, 1997. ADDRESSES: Comments may be mailed to Chief, Office of Migratory Bird Management (MBMO), U.S. Fish and Wildlife Service, Department of the Interior, ms 634-ARLSQ, 1849 C Street, NW, Washington, D.C. 20240. Comments will be available for public inspection during normal business hours in room 634, Arlington Square Building, 4401 N. Fairfax Drive, Arlington, Virginia. FOR FURTHER INFORMATION CONTACT: Paul R. Schmidt, Chief, MBMO, U.S. Fish and Wildlife Service, (703) 358-1714. SUPPLEMENTARY INFORMATION: The Service is the Federal agency with the primary responsibility for managing migratory birds. The Service's authority is based on the Migratory Bird Treaty Act (MBTA) (16 U.S.C. 703-711), which implements conventions with Great Britain (for Canada), the United Mexican States (=Mexico), Japan, and the Soviet Union (=Russia). The double-crested cormorant is afforded Federal protection by the 1972 amendment to the Convention for the Protection of Migratory Birds and Game Animals, February 7, 1936, United States-Mexico, as amended, 50 Stat. 1311, T.S. No. 912, as well as, the Convention Between the United States of America and the Union of Soviet Socialist Republics [=Russia] Concerning the Conservation of Migratory Birds and Their Environment, November 26, 1976, 92 Stat. 3110, T.I.A.S. 9073 (16 U.S.C. 703, 712). The take of double-crested cormorants is strictly prohibited except as may be permitted under regulations implementing the MBTA. In addition to, Federal statutes, the double-crested cormorant may also be protected by State regulations. Regulations governing the issuance of permits for migratory birds are authorized by the MBTA and subsequent regulations (Title 50, Code of Federal Regulations, Parts 13 and 21). Regulations in Subpart D of Part 21 deal specifically with the control of depredating birds. Section 21.41 outlines procedures for issuing permits. Sections 21.43 through 21.46 deal with special depredation orders for specific species of migratory birds to address particular problems in specific geographical areas, establishing a precedent for species and geographic treatments in the permitting process. Service policies for issuing depredation permits for aquaculture were described by Trapp et al. (1995). Federal responsibility for the management of injurious wildlife, including migratory birds, lies with the Animal Damage Control (ADC) program of the U.S. Department of Agriculture's Animal and Plant Health Inspection Service. The primary authority for ADC activities is the Animal Damage Control Act of 1931, as amended, 46 Stat. 1468 (7 U.S.C. 426-426c). Animal Damage Control activities are conducted at the request of, and in cooperation with, other Federal, State, and local agencies; private organizations; and individuals. Management responsibilities of ADC in the cormorant-aquaculture conflict were reviewed by Acord (1995). Population Status of the Double-crested Cormorant The double-crested cormorant breeds widely throughout much of coastal and interior North America. As of 1992, it had been found breeding in 40 of the 50 United States, all 10 Canadian provinces, and in Mexico, Cuba, and the Bahamas (Hatch 1995). However, it is not uniformly distributed across this broad area. Sixty-one percent of the breeding birds belong to the Interior population, while another 26 percent belong to the Atlantic population. Two major areas of concentration are apparent in the vast range of the Interior population: (1) the prairie lakes of Alberta, Manitoba, and Saskatchewan (which account for 69 percent of the Interior population); and (2) the U.S. and Canadian Great Lakes (accounting for another 12 percent). Seven political units account for 70 percent of the North American breeding birds, with Manitoba alone accounting for 36 percent. Thirty (52 percent) of the 58 political units listed by Hatch (1995) each harbor fewer than 100 breeding pairs. In the catfish-producing States identified by Price and Nickum (1995), only Florida and California have sizeable breeding populations. In the south-central United States (Arkansas, Louisiana, Mississippi, and west Tennessee), the double-crested cormorant has been known since pre-colonial times and has been recorded as an occasional breeder throughout the swampy forests of the region since at least the early 1800s (Jackson and Jackson 1995). Jackson and Jackson predicted that (in the absence of major limiting factors) the cormorant will once again become a regular member of the mid-South breeding avifauna, with birds dispersed more widely because of reservoir construction and with concentrations expected in the vicinity of aquaculture facilities. The double-crested cormorant has always been widely distributed as a breeding species. The only suspected instance of range expansion in the 20th century is in the United States and Canadian Great Lakes, which apparently were colonized by birds expanding eastward from the Canadian prairies beginning with Lake Superior about 1913 and ending with lakes Erie and Ontario in the late 1930s (Weseloh et al. 1995). It is possible, however, that these events represented recolonization of former (but previously undocumented) breeding localities from which the species was extirpated before 1912. For example, although Barrows (1912: 67) knew of no breeding records for Michigan, he noted that it was "generally distributed over the State during the migrations" (with specimens from almost every county) and speculated that "probably there are few sheets of water any size within our limits which are not visited by this bird at least occasionally." The core of the wintering range (i.e., the regions of greatest density) did not change appreciably between 1959-1972 and 1959-1988 (Root 1988: 11, Sauer et al. 1996b). Cormorant wintering populations are concentrated in coastal States and Provinces, from North Carolina to Texas in the east and from California to British Columbia in the west. In the mid-South, there also are appreciable concentrations inland from the coast (e.g., east Texas, eastern Oklahoma, southeastern Arkansas, west-central Mississippi, and northeastern Alabama). Of the 9 catfish-producing States for which Christmas Bird Count data are available, 6 have indices of relative abundance that exceed the national mean; the median abundance in these 6 States (including the major catfish-producers of Alabama, Louisiana, and Mississippi) was 2.0 times the national mean (range: 1.4-9.6). The scattered occurrence of early winter stragglers throughout much of the interior of the continent as far north as Minnesota and southern Saskatchewan (Sauer et al. 1996b) is probably a natural phenomenon of longstanding (i.e., it probably does not represent a northward expansion of the wintering range). As evidence of this, we find that 11 percent of 227 winter recoveries (December-February 1923-1988) of birds banded in Saskatchewan, Lake Huron, and eastern Lake Ontario were from latitudes north of the major catfish-producing States of Alabama, Arkansas, Louisiana, and Mississippi (Dolbeer 1991). Forty percent of these 227 winter recoveries are from 1 deg blocks of latitude and longitude that intersect the Gulf Coast and another 22 percent are from degree blocks that intersect the main stem of the Mississippi River. Analysis of 5,589 band recovery records for the period 1923-1988 (Dolbeer 1991) revealed that southward movement from areas north of latitude 42 deg N occurs primarily in October and November. Cormorants of all ages are at their greatest median distance from northern nesting areas-about 1,900 kilometers (1,200 miles)-from December through March. Cormorants nesting in Canada and the northern United States from Alberta to the Gulf of St. Lawrence migrate in winter primarily to the southern United States between Texas and Florida. There is considerable mixing and overlap in winter of nesting populations from widely divergent areas. From 38 to 70 percent of the birds from Saskatchewan through the Great Lakes region winter in the lower Mississippi Valley (States of Arkansas, Louisiana, and Mississippi) as do 10 percent of the birds from such disparate areas as Alberta and the New England coast (Dolbeer 1991). In other words, the major catfish-producing States of the lower Mississippi may be envisioned as lying at the apex of an inverted triangle, with cormorants from a 3,000 kilometer (1,860 mile) expanse of breeding range being funneled into the region in the winter by topographic features and the flow of the major rivers. In commenting on this funneling effect, Jackson and Jackson (1995) noted that "It is a most unfortunate coincidence that the very heart of the catfish-farming industry is located in the Mississippi Delta at the confluence of the Arkansas and Mississippi rivers." [p33962] Our knowledge of double-crested cormorant population trends before 1959 is based on fragmented and largely anecdotal accounts from scattered portions of the range. Syntheses of much of this information (Hatch 1995, Weseloh et al. 1995, and Jackson and Jackson 1995) reveal the following general patterns: (1) by 1900, cormorant numbers had been reduced, and their range possibly restricted, by human persecution and the extensive drainage and degradation of natural wetlands; (2) the widespread construction of reservoirs and impoundments (beginning in the 1920s), in concert with sport fish stocking programs and the creation of refuges and other conservation lands (beginning in the 1930s), had beneficial effects on cormorant numbers; (3) the widespread use of DDT and other pesticides (beginning in the 1940s) had devastating effects on cormorant reproductive success, with the result that populations reached their lowest point in the mid-1970s; (4) the ban on DDT in 1972 and the general decrease in levels of environmental contamination, in concert with development of the catfish industry in the mid-1970s, created a favorable environment for the growth of cormorant populations. Quantitative information on double-crested cormorant population trends is available from three sources: (1) Breeding Bird Survey data (1966-1994), (2) Christmas Bird Count data (1959-1988), and (3) published accounts of censuses of breeding colonies. Trend information from these sources is discussed in the following paragraphs:
FORAGING BEHAVIOR OF THE DOUBLE-CRESTED CORMORANT AT
AQUACULTURE FACILITES Feeding Rates Prey Size Impacts of Double-crested Cormorants on Aquaculture The fairly large body of literature that has developed in the past 12 years represents an attempt to assess the impacts of cormorants on the commercial catfish industry. Synopses of the pertinent literature are given in the following paragraphs. In the past, cormorants have been reported only infrequently at fish hatcheries. For example, questionnaire surveys conducted in 1977 (Scanlon et al. 1979) and 1984 (Parkhurst et al. 1987) indicate that cormorants were considered to be problems at only 4-5 percent of these facilities nationwide. Of the more than 90 other (including non-avian) species mentioned as predators, 45-50 percent were listed more frequently than cormorants. Purported instances of cormorant damage to hatchery fish in Texas (Dukes 1987) include the loss of 90 percent of the smallmouth bass (Micropterus dolomieui) 2-year-old brood stock at the Jasper facility. The frequency of occurrence of cormorants at a given catfish pond is a function of many interacting factors, including: (1) size of the regional cormorant population; (2) the number, size, and distribution of catfish ponds; (3) the size distribution, density, health, and species composition of fish populations in the catfish ponds; (4) the number, size, and distribution of "natural" wetlands in the immediate environs; and (5) the size distribution, density, health, and species composition of "natural" fish populations in the surrounding landscape. Cormorants are adept at seeking out the most favorable foraging sites. As a result, cormorants rarely are distributed evenly over a given region, but rather tend to be highly clumped or localized. For example, in 27 weekly surveys at 50 catfish ponds in Humphreys County, Mississippi, 1987-1988, cormorants were observed at only 9 of the 50 ponds and only on 14 occasions (Hodges 1989). Thus, it is not uncommon for many fish farmers in a region to suffer little or no economic damage from cormorants, while a few farmers experience exceptionally high losses. Cormorants clearly respond in a positive way to the presence of shallow-water ponds stocked with high densities of easy-to-capture prey fish. For example, within two weeks of stocking 2 ponds in Hendry County, Florida, with 5-20 centimeter (2-8 inch) fingerling catfish, 12 cormorants were feeding in the ponds and roosting on nearby poles. A nearby 2.5 hectare (6 acre), 2.5-meter (8-foot) deep pond, stocked with 75,000 3-8 centimeter (1-3 inch) fish in August 1980, had attracted 13 cormorants by September. These birds continued to feed at the pond throughout the fall and winter, and in spring 1981 they nested in a nearby cypress dome. By November 1981, about 50 cormorants were feeding in the pond (Schramm et al. 1984). The positive response of cormorants to the presence of shallow-water ponds stocked with high densities of easy-to-capture prey fish (as illustrated above) is clearly a major factor responsible for their impacts in a variety of aquaculture situations (e.g., baitfish ponds in Minnesota, koi ponds in Missouri and elsewhere, ornamental fish ponds in Florida, and catfish pods in the southeastern United States and elsewhere). Assuming averages of 5 fingerling catfish consumed/cormorant/hour and 30 cormorants/pond (a constant number of feeding birds present throughout an 8 hour day), the catfish population of a typical pond in the Mississippi Delta (51,000 fish/hectare in a 8-hectare pond, which is equivalent to 20,650 fish/acre in a 20-acre pond) would be halved in 167 days (Stickley et al. 1992). However, if actual values were nearer the median values of 2 fish/cormorant/hour and 15 birds/pond (from Stickley et al. 1992), the number of days required for the cormorants to reduce the population by half would be increased to 850 days (a 5-fold increase). Of 281 catfish farmers queried on the Mississippi Delta in 1988 (Stickley and Andrews 1989), 87 percent felt that they had a bird problem. Moderate to heavy cormorant activity (defined as at least 25 birds/day) was reported by 57 percent of Delta farmers. Losses to birds (harassment costs plus value of fish lost) were estimated at $ 5.4 million (3 percent of total sales). Overall, there appears to be little conflict between cormorants and the food- or game-fish industry in Florida (Brugger 1992), but losses of food fish, primarily catfish, can be locally severe (Brugger 1995); for example, cormorants were responsible for the loss of up to 50 percent of the fingerling catfish in open 0.125 hectare (0.31 acre) ponds during 1991 at the University of Florida. Although fish of commercial value made up only a small percentage of the diet of cormorants collected in the vicinity of aquaculture facilities in central and southeast Arkansas from mid-October to early December, the finding of a few fish of very high value (e.g., grass carp with wholesale value of about $ 4.00 and koi worth $5.00-10.00 each) suggests that cormorant depredations can be locally or seasonally severe. On the Mississippi Delta, cormorants consumed an estimated 18-20 million catfish during the winters of 1989-1990 and 1990-1991, which was equivalent to 842-939 metric tons (928-1,035 short tons, or 1.86- 2.07 million pounds, or 844-939 thousand kilograms). Based on the cost of replacing these fish, annual losses to the catfish industry were estimated at $ 1.8-2.0 million, which corresponds to about 4 percent of the estimated catfish standing crop each year. Although losses were documented over a six-month period, the majority (about 64-67 percent) occurred in February and March (Glahn and Brugger 1995). At catfish farms in Oklahoma (with about 324 hectares [800 acres] of surface water in production) in 1993, cormorants consumed an estimated 7,196 kilograms (15,900 pounds, or 7.9 short tons) of catfish valued at $ 14,000-36,000 (depending on size of the fish consumed), or about 3-7 percent of Oklahoma catfish sales (Simmonds et al. 1995). [p33964] Cormorant Depredation Permits Between 1989 and 1996, the number of permits issued to take double-crested cormorants in the southeastern United States more than quadrupled, from 50 to 215 (Coon et al. 1996). The reported take of 4,000-8,000 birds annually has had no noticeable effect on the size of the regional wintering population. Mastrangelo et al. (1995) noted that the reported take never exceeded 68 percent of the authorized take and attributed this to the frightening effect that lethal control has on bird behavior. Hess (1994) described a recent study in which catfish farmers at three complexes in Mississippi were authorized (under Fish and Wildlife Service permits) to remove as many as 2,500 cormorants in a 19-week period. Participants were supplied with ammunition and encouraged to kill as many birds as allowed by the permit. The fact that only 290 birds had been killed by the end of the project was attributed to a learned behavior by the birds to avoid areas where they might be shot (Hess 1994). Proposed Regulation Promulgation PART 21-[AMENDED] 2. Part 21, subpart D, is amended by adding Sec. 21.47 to
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