BULLETIN OF THE UNITED STATES FISH COMMISSION. 105 



The largest iimnber of salmou, and frequently also the heaviest weight 

 was obtained in August and July, but the number of salmon was in 

 many years nearly as large in May and April. This is of great eco- 

 nomical importance, for it is well known that salmon fetches a much 

 higher price in spring and early summer than later in the season, when 

 the fish are smaller and leaner ; the earlier the great hauls are made, 

 the better it will be, During the last years of the. above period, 

 especially Irom 1879, these large hauls have as a rule been made in 

 August and July. The smallest hauls, both as regards number and 

 weight, have generally been made in March and September; but from 

 the year 1853 this circumstance is of no importance, as from some cause 

 or other the fisheries from that year on did not come to a close in Au- 

 gust; fish were still caught during the early part of September. The 

 number of fish caught has been smallest in six, or (if September after the 

 year 1852 is not taken into account) in eight, years during the month 

 of June, and in four years during July. The smallest weight, however, 

 in June was only in three years. 



It would be exceedingly interesting if we had the condition of the 

 water, wind, and temperature during all of the thirty-seven years con- 

 sidered; it is well known that the changes in the quantity of water in 

 small streams exercise a considerable influence on the salmon fisheries. 

 When there are strong spring floods the spring fisheries are generally 

 good. If there are no strong floods till later in summer, the largest 

 fisheries take place at the same time as these floods. As with few ex- 

 ceptions the strongest floods and the highest water come in autumn, 

 and as the weirs in the river Viskan cannot be passed by the salmon 

 till that time, it is very important that nothing should hinder their 

 ascent in autumn. 



The minimum annual number offish caught during the above period 

 was 207, weighing 3,241 i)ounds, and the maximum annual number 

 was 7G8, weighing 9,348 loounds. During the thirteen years 1843-1856 

 the average number of salmon caught per annum was 529, weighing 

 5,902 pounds ; during the thirteen years 185G-1869 the average per 

 annum was 410 salmon, weighing 3,929 pounds ; and during the period 

 1874-1884 the average number of salmon was 389, and the average 

 weight 3,97C pounds. In August, 1874, the water of the Viskan was 

 polluted by refuse from a factory at Rydal, and the circumstance that 

 in spite of this the salmon fivSheries did not decline to any considerable 

 extent after that year, must be ascribed to the hatching of salmon, 

 which after 1874 was carried on for a number of years. The facts 

 that very few salmon were caught in 1878, and that the average weight 

 of the s.almon was greater that year than in any of the thirty-seven years 

 in question, and that in 1878 but few small salmon were caught, while 

 they again occurred in large numbers after 1878, are owing to another 

 pollution of the water which took place in that year. 



