the bay. After reaching the shoals in the middle portion of the river they move slowly, having already found pretty good spawning grounds. They are about two months reaching their spawning grounds (between stations 17 and 8 of the accompanying map), which are but little more than half as far up stream as those of the spring run.
In September, 1901, over a hundred salmon were weighed and branded with serial numbers and released in the river at Rio Vista. Three of these were taken later upon their arrival at the spawning grounds. The following is a tabular statement of the data concerning them, the loss in weight being due to migration alone. No. 34 was 8 days in spawning, extruded all but 20 ova, and lost thereby 21 per cent, more of the Rio Vista weight.
| No. | Sex. | Distance traveled. miles. |
Time, days. |
Loss in weight, percentage |
| 8 | female | 300 | 65 | 28 |
| 34 | female | 300 | 61 | 20 |
| 43 | male | 350 | 65 | 26 |
The salmon of the spring run reach their spawning grounds from two to six weeks, or even longer, before spawning, which time they spend lying quietly in the pools. The fall salmon are more nearly ripe when they arrive at the spawning grounds, many of them ceasing to ascend only when ready to spawn. 
Head of a Salmon with the Opercle cut away, showing the gills attacked by fungus and Parasitic Copepods. Yet alive when taken.
Spawning and Death.
Salmon are in fairly good condition when they begin spawning, notwithstanding the fact that they have been without food for several weeks or even months, and have traveled several hundred miles in the meantime. The male has changed his appearance. His snout has grown longer and much hooked; large, conical, hooked teeth have appeared in his jaws; his body has grown thinner and apparently deeper, though the latter point has not been determined yet by measurements; his skin has thickened and embedded the scales. The larger males become somewhat reddish in color as spawning time approaches. The female has changed less. The abdomen is somewhat distended from the ripening ova, the skin thickened as in the male, and the color has become more or less of a dull olive.
