Trends in the Abundance of American Shad, Alosa sapidissima, in the Delaware River Basin

Chesapeake Science Vol. 15, No. 2, p. 9 6 - 1 0 3 June, 1974

Trends in the Abundance

Alosa sapidissima, in the

Delaware River Basin 1, 9

of American Shad,

MARK E. CHITTENDEN, JR. 3

Virginia Institute of Marine Science Gloucester Point, Virginia 23062

ABSTRACT: The American shad, Alosa sapidissima, was very abundant in the Delaware River Basin until 1901. Annual commercial landings f rom 1890 to 1901 (about 11 to 17 mill ion Ib) were several times greater than in any other river system. Abundance declined rapidly after 1901, except for a resurgence in 1907 which may be interpreted as evidence that by 1903 pollution was affecting successful seaward movement of young produced in the Delaware River. Less than 0.5 million Ib were landed in 1920. Abundance has remained low since 1920, although fluctuations have occurred.

Extra-Delaware Basin fish mLx with Delaware Basin fish at the mouth of Delaware Bay. It is not clear how far extra-Delaware Basin fish penetrate upbay, but they do not enter fresh water of the Delaware River. Records available for several years in the period 1890-1901 indicate that 39% of the total Delaware Basin landings came from fresh water of the Delaware River, suggesting that landings at that time were primarily dependent on Delaware Basin fish.

Introduction

The Delaware River Basin once supported larger landings of American shad, Alosa sapidis- sima, than any other river system (Stevenson, 1899; Sykes and Lehman, 1957). The abundance of Delaware Basin American shad has varied greatly, but there is no up-to-date accurate description of this. Sykes and Lehman (1957) presented catch estimates for many years in the period 1887 to 1954 but made no estimates for many years in the early 1900's when abundance of this species changed greatly. Walburg and Nichols (1967) discussed landings in 1960. However, trends after 1954 have not been described although fluctuations have occurred. Causes of fluctuations in abundance after 1900 are discussed by Ellis et al. (1947), Sykes and Lehman (1957) and

1 Contribution No. 608 from the Virginia Institute of Marine Science.

~Based on part of a Ph.D. thesis, Rutgers Univer- sity, New Brunswick, N.J.

3Present address: Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas 77840.

Chittenden (1969) and are not emphasized in the present paper.

The objectives of this paper are to describe more fully the historical and recent status of American shad in the Delaware River Basin and to suggest the sources of American shad landed in the Delaware Basin. In lieu of better data, total catch records are extensively used in this paper to suggest trends in population size. Total catch C is related to population size N by the expression:

C = q f N

where f = total number of units of standard effort, and q = catchability, the fraction of the population captured by one unit of standard effort. Total catch records then depend on population size N, an assumed constant catch- ability q and the total effort f for which good records unfortunately do not exist.

Abundance

BEFORE 1880

American shad were very abundant in the colonial and post-revolution period. Gay (1892)

96

Abundance of Delaware River Basin American Shad

and Meehan (1896) described abundance in this period, but few catch records exist. Indians drove many American shad into stone pens in the shallows by beating the water with brush. William Penn mentioned one seine-haul catch of 600 fish in the Schuylkill River near Phila- delphia (Fig. 1). Thousands of fish were captured near Milford, Pa., about 1751 in a 1.5-mile-long seine haul. Immense numbers of fish appeared at Deposit, N.Y., on the West Branch of the Delaware River each spring; local residents captured hundreds, sometimes thou- sands, of fish during the early 1800's using the Indian method of brush seines and pens. One seine haul catch of 10,800 American shad was made in tidal water during 1820 (Gay, 1892). Howell (1837) estimated the total annual Delaware Basin catch was nearly 1.5 million fish. About 90,000 to 170,000 fish were caught annually from 1819 to 1822 and in 1845 and 1846 at the Fancy Hill Fishery, a haul-seine fishery formerly near Gloucester City, N.J. (Stevenson, t899). Howell's estimate may be fairly reasonable, because several other haul seine fisheries existed then in addition to an unknown number of recently introduced drift

Fig. 1. The Delaware River Basin

97

gill nets reported by Howell to have caught many fish.

Man seemingly had tittle effect on abundance of American shad in the Delaware Basin until about 1825 to 1840. Dams were constructed then, restricting access to spawning grounds and nurseries in major tributaries such as the Lehigh and Schuylkill rivers and to the Delaware River above Lackawaxen, Pa. (Meehan, 1896; Mihur- sky, 1962). Slack (1874) reported the following average annual catches at the Fancy Hill Fishery: 1818 to 1822, 131,000; 1845 to 1849, 66,890; 1865 to 1869, 60,739; and 1870 to 1873, less than 25,000. Annual figures reported by Stevenson (I899) indicate the average catch was about 44,000 fish from 1870 to 1873. Trends in abundance during the period covered by Slack's figures are not clear, however, because the annual amount of effort is not known. Increased effort associated with intro- duction of gill nets was probably responsible, at least in part, for the reduced catches of the haul seine fisheries after the early 1820's. Gill nets were introduced after 1822, although the gill net fishery was not fully established until after 1865 (Stevenson, 1899). It does seem from the catches above and especially from the tenor of accounts by Abbott (1868), Slack (1874), Gay (1892) and Meehan (1896) among others that abundance decreased after the 1820's and that it was "low" about the 1870's. However, Slack (1874) stated that at least 2.5 million fish were caught in 1872. Slack was then a New Jersey Fish Commissioner; his estimate may be fairly reliable (although possibly high), because par- tial censuses of the New Jersey catch were made after 1870. The New Jersey catch in 1876 and in 1877, based on incomplete records, was about 700,000 fish (New Jersey Commissioners of Fisheries; 1877, 1878).

1887-1968

Estimates of annual commercial landings of American shad in the Delaware River Basin for most years after 1886 are in Fig. 2. Estimates prior to 1955, unless specifically stated other- wise, were taken from Sykes and Lehman (1957). Revision of certain of their estimates seemed desirable and this was done. Comments about the nature of the estimates follow. The abbreviations N.J. and Pa. were used for annual reports of the Board ~of Fish and Game

98 M. E. Chittenden, Jr.

4-

~e85 ,e~o ,895 leOO ~905 ,s~o 1915 ,9zo fee5 1930 ,e35 ,e40 19~ f~50,955,96o ,9s5 ,97o

Fig. 2. Catch of American shad in the Delawaie Basin, 1887-1968.

Commissioners of New Jersey and Commis- sioners of Fisheries of Pennsylvania, respec- tively. In some instances, catch records about 1900 expressed in numbers were converted to pounds. The correct weight conversion factor is not known, but I assumed a value of 3.75 lb chosen from published estimates in that time period (see discussion of landings in 1896).

1893, 1894, 1895. Sykes and Lehman (1957) estimated landings as 19.0, 14.8 and 16.0 million lb for these respective years based upon Stevenson's (1899) statement that the 1896 catch was the best since 1893 and was 20% and 30% larger than the catches in 1894 and 1895, respectively. Sykes and Lehman's estimate for 1896 (which see) is probably much too high. Following Sykes and Lehman but using Smith's (1898) estimate of the 1896 catch as a comparative basis, the 1893 catch was probably about 14.5 million lb; catches in 1894 and 1895 were estimated as

1896 catch = __=x 14 million lb 120 100

and

1896 catch _ x _ 12.9 million lb, 130 100

respectively. 1896. Estimates of the 1896 catch were

4,016,862 fish weighing 16,828,250 lb (Smith, 1898) and 4,017,462 fish of which 3,882,624 came from Delaware Bay and the Delaware River (Stevenson, 1899). Sykes and Lehman a~ 2arently used an average weight of about 5 lb to convert one of Stevenson's numbers to 19.2 million lb, but their weight conversion factor is much higher than any used by workers about 1896 (average = 3.75 or 3.50 lb from Steven- son, 1899:121, 123; average = 3.75 lb from

Townsend, 1901: 264; average = 4.2 lb from Smith's 1898 figures). Therefore, Sykes and Lehman's estimate is probably too high. Wal- burg and Nichols (1967) apparently had the same opinion; they cited Sykes and Lehman but estimated the 1896 landings as 16,699,741 lb based on one of Stevenson's counts. It is not clear which, if any, of these several weight averages and landings figures are correct. How- ever, it seems best to accept Smith's (1898) figures for 1896, because he was contemporary to the situation and presented both numbers and weight of the catch.

1899. N.J. (1899) stated this was an exceptionally good year in tidal water, and Pa. (1900) reported the greatest catch ever. Using the 1896 catch as a comparative basis, about 16.5 million lb were landed in 1899.

1900. Pa. (1901) stated the catch was so large that fishermen complained about it, and N.J. (1900) reported the entire Delaware Basin catch was 4,067,307 fish. Multiplying this figure by 3.75 gives 15,252,000 lb.

1901. Sykes and Lehman's (1957) estimate was 13,368,000 lb, but its basis is not clear. Evermann (1904) reported the numbers and weight of fish caught in Pennsylvania, Delaware and New Jersey, and the Delaware Basin totals were 3,780,554 fish weighing 16,382,379 lb.

1902. N.J. (1902) stated that the catch was not as large as usual. My estimate is about 9 million lb.

1903. N.J. (1904) stated the catch was the smallest ever recorded and that 1 million fish were caught by New Jersey fishermen. N.J. (1906) reported that there had been a gradual annual decline in catch. My estimate is about 6 million lb.

1905. N.J. (1906) reported 870,975 fish caught in 1905 and 1,240,350 in 1904. U.S. Commissioner of Fisheries (1906) reported 1,216,935 fish caught in 1904. The total catch in 1905 was estimated as:

weight, 1904 =. x - 3,204,845 lb. number, 1904 number, 1905

1906. N.J. (1908) stated that 1906 was the poorest season ever known. My estimate is about 3 million lb.

1907. N.J. (1908) reported a great increase in the number caught and Pa. (1908) stated that the 1907 catch was the greatest in the new

Abundance of Delaware River Basin American Shad 99

century. Meehan (1907) stated that the catch was greatly increased over previous years. Pa. (1909:80) stated that the 1908 catch was about half that of 1907. My estimate is about 7 million lb.

I estimated catches for the period 1955 to 1968 from unpublished records of the National Marine Fisheries Service for Delaware (12. H. Lyles and H. A. Wheeland, pers. commun.) and New Jersey (E. A. LoVerde, pers. commun.). There has been no commercial catch of American shad in Pennsylvania recently (G. L. Trembley, pers. commun.), and this has been true since 1943 (Walburg and Nichols, 1967). Landings from Cape May County, N.J., which also borders the Atlantic Ocean, were excluded following Sykes and Lehman (1957).

Catch estimates for each year may not be exact. The completeness of the catch figures may vary from year to year, the correct weight conversion factors are not known, and many quanti tat ive estimates for the period 1893-1907 are based upon adjective compari- sons of abundance in the literature. The latter point deserves special comment. Adjective estimates such as "abundant," "good year," "poor year," etc., if at all valid, obviously depend upon the setting they are made in and cannot be compared over long periods of time. "Abundant" as used in the late 1800's repre- sents an entirely different magnitude of catch than "abundant" in the 1960's, for example. However, in a short period of time, such as 1896-1910, comparative adjective estimates probably represent trends fairly well, especially when some catch records are also available in that period.

Trends in Abundance

Few catch records exist, but there can be little doubt that American shad were very abundant in the Delaware Basin prior to 1880. Catch statistics (Fig. 2) show that abundance was very high through 1901. Annual landings during the 1890's were scveral times greater than those in any other river system (Steven- son, 1899). After 1901 abundance declined rapidly except for a resurgence in 1907. With the exception of 1907, landings during the period 1904-1913 were about 3 to 5 million lb, a decrease of some 10 million lb from the annual landings in the decade ending in 1901.

Less than 0.5 million lb were landed in 1920, and Delaware Basin landings have since been consistently much less than 0.5 million lb. This great change in landings probably primarily reflects greatly decreased abundance, not change in effort. The number of nets used changed from 1,189 in 1896 and 1,145 in t904 to 818 in 1910 and 961 in 1921 (Sykes and Lehman, 1957). The relative change in number of nets used is much smaller than the change in catch. The number of nets used may not be exact effort estimates, but they do indicate that change in effort was not a major factor in the greatly decreased landings.

The apparent resurgence in 1907 deserves special comment, because it is circumstantial evidence which may be interpreted as an indication that pollution limited abundance of American shad in the Delaware River by 1903. There are unfortunately no catch data for 1907, but the fact of a resurgence is indicated by the four references cited. Pollution causes extremely low dissolved oxygen in the Phila- delphia area during much of the year, and this has been responsible for the low abundance of American shad (Ellis et al., 1947; Sykes and Lehman, 1957; Chittenden, 1969). Dissolved oxygen levels greatly influence the success with which the adults migrate upstream through the Philadelphia area. However, dissolved oxygen levels tend to be lower in the fall than during the spring, and destruction of the young as they move seaward in the summer and fall has been the main factor (Chittenden, 1969). Sykes and Lehman (1957) constructed a linear regression model which indicated that as far back as 1921 oxygen conditions during the fall were com- parable to conditions during the 1960's, but their model was based on little data. 12hittenden (1969) presented actual dissolved oxygen records from the fall of 1921 which closely coincided with predictions of Sykes and Leh- man's model, and Chittenden presented addi- tional records indicating similar gross pollution by 1915. Obviously this condition did not arise overnight, but I am not aware of earlier dissolved oxygen records. Large numbers of Delaware River American shad first return to the parent stream at age IV (Chittenden, 1969), so that a large run in 1907 could reflect very successful seaward movement of the young in 1903 if pollution were then limiting abundance. Seaward movement of the young is regular in

100 M.E. Chittenden, Jr.

its timing, is closely keyed to water tempera- ture in its later stages and most young produced upstream from the Philadelphia area probably have always passed that area during September, October and November (Chittenden, 1969, 1972). One of the greatest floods ever recorded in the Delaware River occurred on 11 October 1903 when discharge at Trenton, N.J. was estimated at 295,000 fta/sec (U.S. Geological Survey, 1965) in contrast to a mean October discharge of about 6000 ft3/sec from 1945 to 1963 (Keighton, 1965). The flood coincided closely in time with the normal seaward movement of many young past tile Philadelphia area and may have modified water quality to greatly enhance the success of seaward move- ment in 1903.

Fig. 3 shows abundance trends from 1925 to 1968 based upon total landings in the Delaware River Basin (Fig. 2) and upon annual catch/haul records (Table 1) of the Lewis Fishery located on nontidal water of the Delaware River at Lambertville, N.J. The Lewis Fishery records are not based on constant fishing procedures. Four haul seine fisheries operated at Lambert- ville from 1925 to 1927 and three from 1928 to 1943. Thereafter, only the Lewis Fishery was active except for one other in 1947. Effort and total catch were generally much greater before 1948, because the fishery was primarily a hobby after 1947. Maximum net length de- creased from 400 to 250 yards after the early 1950's, and the seining distance was halved. Procedural changes after 1948 tend to decrease the catch, making these records more com- parable to earlier ones when there was more gear competition.

Total landings data and Lewis Fishery records show quite similar trends from 1925 to

5 6

600- !, !, . ,5 =

-Jo ~ g

"g o - w ~

0[920 , i I f 1930 19'40 1950 1960 1970

Fig. 3. Trends in American shad catches in the Delaware Basin and in the Lewis Fishery.

1968. American shad runs in the Delaware River during the 1930's varied but were generally larger than in most succeeding years. The smallest runs ever probably occurred after 1945, especially during some years in the 1950's when the Lewis Fishery captured no fish. Abundance greatly increased during the

TABLE I. Statistics of the Lewis Fishery at Lambertville, N.J., 1925-1968.

Days Number Number Catch/ Year Fished of Hauls Caught Haul

1925 42 455 742 1.6 6 31 208 661 3.2 7 46 436 1,016 2.3 8 53 543 2,174 4.0 9 64 616 2,706 4.4

1930 45 362 479 1.3 1 53 501 887 1.8 2 47 450 1,442 3.2 3 45 420 2,325 5.5 4 48 520 1,796 3.4 5 42 328 4,417 13.5 6 45 392 951 2.4 7 32 448 4,161 9.3 8 63 693 3,249 4.7 9 48 506 4,439 8.8

1940 29 170 611 3.6 1 30 162 129 .8

2 39 193 1,096 5.7 3 44 215 3,025 14.1 4 15 45 226 5.0 5 37 144 295 2.1 6 31 118 254 2.2 7 46 358 1,258 3.5 8 28 59 43 .7 9 30 32 3 .1

1950 41 51 9 .2 1 34 38 25 .7 2 36 43 27 .6 3 30 31 0 0 4 19 26 9 .4 5 40 43 36 .8 6 29 32 0 0 7 9 12 10 .8 8 14 18 15 .8 9 16 24 27 1.1

1960 12 19 6 .3 1 14 26 90 3.5 2 15 18 250 13.9 3 40 71 3,983 56.1 4 39 90 1,646 18.3 5 31 48 319 6.6 6 38 44 77 1.8 7 35 65 243 3.7 8 22 27 33 1.2

Abundance of Delaware River Basin American Shad 101

early 1960's and then declined after 1965. The 1963 run of American shad in the Delaware River was among the largest, possibly being the largest, in the last 45 years or more. The average Lewis Fishery catch in 1963 was larger than their total in most years after 1947, and their largest single catch (440 fish) was about the same size or larger than their totals for many years from 1925 to 1947.

Sources of Fish Captured in the Delaware Basin

The parent stream which supported the great Delaware Basin landings of American shad in the 19th century is not known with certainty. Sykes and Lehman (1957) suggested that the catch about the early ]950's was probably primarily composed of fish produced in other coastal rivers or in other Delaware Bay tribu- taries, not Delaware River fish. Talbot and Sykes (1958) reported that 10 of 237 fish tagged on the spawning grounds in the Hudson and Connecticut rivers were recaptured a year later in Delaware Bay. Many fish tagged by White, Lane and Hamer (1969) in Delaware Bay in Cape May and lower Cumberland Counties, N.J. (Fig. 1) were recaptured in the Hudson and Connecticut Rivers within about 40 days or within 60 days in Canadian waters, primarily the St. Johns River or Harbor, New Brunswick. Only one fish was recaptured that soon from south of Delaware Bay (at Wallops Island, Va.). Therefore, there is mixing of intra- and extra- Delaware Basin stocks near the mouth of Delaware Bay. Apparently the extra-Delaware Basin stocks are mostly from the more north- erly Hudson and Connecticut Rivers or Cana- dian streams, but further work is needed to establish this. Talbot and Sykes (1958) ob- served similar mixing near the mouth of Chesapeake Bay, although Chesapeake system stocks greatly predominated.

Extra-Delaware Basin fish do not penetrate far upstream. There were only 1.7% repeat spawners in the Delaware River during 1944, 1945, 1947 and 1952 (Sykes and Lehman, 1957) and none during 1961 (J. Malcolm, pers. commun.). Chittenden (1969) found 0.3% in 1963 and 1.5% repeat spawners in 1964 at Lambertville and 6.5% during 1965 in a combined sample from Lambertville and Mar- cus Hook, Pa. Most repeat spawners in 1965 were captured at Lambertville. Repeat spawners

in other rivers from Chesapeake Bay north were: James, 27% (Walburg and Sykes, 1957); York, 23% (Nichols and Massmann, 1963); Potomac, 17% (Walburg and Sykes, 1957); Hudson, 51% (Talbot, 1954); Connecticut, 35% (Moss, 1946) and seven-year means were 44 and 32% for males and females, respectively (Leg- gett, 1969). The great difference in repeat spawners between Delaware River fish and these other populations indicates little inter- mixing from Marcus Hook upstream. The transition from brackish to fresh water occurs near Marcus Hook, and it would appear that fish which penetrate upstream to fresh water are native to the river. Streams south of Chesapeake Bay probably contribute little to Delaware Basin landings. The spawning migra- tion is in general much earlier in those streams than in the Delaware Basin and all or essentially all the southern fish die after spawning (Sykes, 1956; Walburg, 1956, 1957, 1960; Godwin, 1968).

New Jersey landed 53% of the Delaware Basin catch from 1955 to 1968 and Delaware landed the remainder. Nearly all the New Jersey catch (87%) came from Cumberland County (Fig. 1). Trends in Delaware Basin landings seem quite similar to trends in catch/seine haul of the Lewis Fishery at Lambertville where only Delaware River fish are captured (Fig. 3), suggesting that both sources of data are similarly influenced or are based upon fish which have a common origin. If the latter is true, it would seem that comparatively few extra-Delaware Basin fish regularly penetrate Delaware Bay much past Cape May or lower Cumberland Counties. White et al. (1969) reported that half or more of the fish tagged near the mouth of Delaware Bay were re- covered outside the bay. They pointed out that the representation of Delaware Basin fish in their returns may not be accurate because the Delaware Bay fishery terminates when the market price paid is too low to make fishing profitable. Many American shad which occur near the mouth of the bay are of extra-Dela- ware Basin origin, but studies in Salem and upper Cumberland counties and adjoining waters in the state of Delaware are necessary to clarify how far extra-Delaware Basin fish penetrate Delaware Bay and how they affect the magnitude of the Delaware Basin catch.

New Jersey, Delaware and Pennsylvania

102 M.E. Chittenden, Jr.

caught 71%, 11% and 16%, respectively, of 69 milfion lbs of American shad reported caught in 1890, 1891, 1892, 1897 and 1901 by Smith (1895), Townsend (1901) and Evermann (1904). Of the New Jersey total catch in these years and in 1898 (Townsend, 1901), 7% came from Cumberland County, 62% from Salem County and 31% from counties bordering fresh water upstream of Salem. All the Pennsylvania counties are upstream of Salem and 72% of the Delaware (State) catch came from Newcastle County which is opposite Salem County. About 39% of the total catch came from fresh water upstream of Salem and Newcastle counties and about 8% were captured downbay of these counties. Stevenson (1899) gave more weight to Delaware Bay catches. Approximately 28% of the 3,882,624 fish he reported landed in 1896 came from Delaware Bay which begins about the downstream limits of Salem and Newcastle counties. Greatest landings were in the Salem and Newcastle county areas, so that slight differences in reporting procedures could greatly influence the apparent importance of Delaware Bay catches. The point appears valid, however, that most of the catch from 1890 to 1901 came from the Delaware Basin upstream of Cumberland County and that about 39% came from fresh water upstream of the Marcus Hook area. Because fish captured in fresh water upstream of Marcus Hook are now of Delaware River origin, it seems probable that the great 19th Century Delaware Basin landings were primarily composed of Delaware Basin stocks and that most fish must have been from the Delaware River.

ACKNOWLEDGMENTS

I am greatly indebted to Mr. Fred Lewis for making catch records of the Lewis Fishery available and to C. H. Lyles, E. A. LoVerde and H. Wheeland of the National Marine Fisheries Service who furnished unpublished federal landings records. Dr. G. Grant of the Virginia Institute of Marine Science reviewed the manuscript.

LITERATURE CITED

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- - - . 1901. Rep. 1900. 194 p. PENNSYLVANIA DEPARTMENT OF FISHERIES.

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the Delaware River, p. 457-459. In Notes on the natural history of the shad and alewife. U.S. Comm.

Abundance of Delaware River Basin American Shad 103

Fish Fish. Rep. Comm. 1872-1873. Past 2. Ap- pend. C:452-462.

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. 1898. Report of the division of statistics and methods of the fisheries. U.S. Comm. Fish and Fish. Rep. Comm. 1897. Part 23 :XCI-CXXlV.

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- - - , and J. E. SYKES. 1958. Atlantic Coast migrations of American shad. U.S. Fish Wildl. Serv. Fish. Bull. 58(142):473-490.

TOWNSEND, C. H. 1901. Statistics of the fisheries of the middle Atlantic states. U.S. Comm. Fish and Fish. Rep. Comm. 1900. Part 26:195-310.

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WALBURG, C. H. 1956. Commercial and sport shad fisheries of the Edisto River South Carolina, 1955. U.S. Fish Wildl. Serv. Spec. Sci. Rep. Fish. 187.9 p. - - . 1957. Neuse River shad investigations, 1953. U.S. Fish. Wildl. Serv. Spec. Sci. Rep. Fish. 206.13 p.

- - , 1960. Abundance and life history of shad St. Johns River, Florida. U.S. Fish. Wildl. Serv. Fish. Bull. 60(177):487-501.

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