§ Mr. William Rossasked the Secretary of State for Northern Ireland if he will list in the Official Report the years for which the mathematical model devised by Dr. Paul Elson was used to predict the size of the run of salmon into the Foyle system; and what was the prediction and the actual outcome for each year.
§ Mr. Adam ButlerThe information requested is set out in the following table. Based on redd counts Dr. Elson projected a range within which total progeny returns to the system four years later could be expected to fall. The projection is expressed as a central estimate with the extremities of the range expressed to two standard errors. In practice returns to the system have usually fallen within the lower limits ie within one to two standard errors below the central estimate.
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Parents Projected progeny returns Year Number of redds Year Lower Limits Central estimate Upper limits Total returns (actual) 2 standard errors 1 standard error 1 standard error 2 standard errors 1970 5,379 1974 65,521 92,978 131,941 187,232 265,693 85,479 1971 4,344 1975 59,937 85,055 120,698 171,277 243,052 59,337 1972 2,153 1976 38,678 54,884 77,883 110,520 156,835 43,824 1973 1,545 1977 29,862 42,376 60,135 85,335 121,095 42,234 1974 3,268 1978 51,329 72,839 103,363 146,678 208,145 55,847 1975 2,696 1979 45,365 64,375 91,352 129,634 183,958 49,387 1976 3,058 1980 49,261 69,904 99,198 140,768 199,758 71,176 1977 1,800 1981 33,739 47,878 67,941 96,412 136,815 50,722 1978 3,894 1982 56,720 80,490 114,219 162,084 230,006 *75,000 1979 3,559 1983 53,975 76,594 108,691 154,283 218,873 †NYA 1980 2,927 1984 47,901 67,974 96,459 136,881 194,242 NYA 1981 3,791 1985 55,909 79,339 112,586 159,766 226,717 NYA 1982 3,515 1986 53,591 76,048 107,917 153,140 217,315 NYA * Rod catch element estimated. † NYA—not yet available.