7824 - Laserfiche WebLink

Home Browse Search

The onset of spawning closely followed an increase in river tem- perature from 9 to 12° C over a 2-day period (Figure 2). Cool, rainy weather prior to June 24 resulted in water temperatures in the 7 to 10° C range. The temperature increase associated with spawning resulted from clear, sunny weather on June 24 and 25. Spawning activity was inter- rupted on July 7 when river temperature fell from 15 to 11° C and level increase 10 cm overnight following cold rains. Temperature rose to 14° C by the time spawning resumed and 18° C was reached by the completion of spawning. Increasing temperatures through the spawning period were accompanied by decreasing river discharge and a drop in river level of 30 cm. The dates of the beginning and ending of spawning and of peak activities varied between sites, although the same pattern was followed at all sites (Figure 3). Spawner counts increased and peaked 1 week earlier at the lowermost site than at the 3 upriver sites. At the up- river sites fish appeared and began spawning at about the same time. Spawning activity at the lower and uppermost sites ended a week earlier than at the other sites. Dates and water temperatures associated with spawning in the St. Joe, St. Maries, and Clearwater Rivers in 1980 were comparable with those documented in the St. Joe in 1981. Spawning was already in prog- ress on the St. Joe River in 1980 when the first site was located on July 1. River temperature increased from 11° C on that date to 16° C by July 12, when spawners had dispersed. Spawners were not observed in the • St. Maries River, but netting information indicated spawning was in progress on June 10, 1980, at a river temperature of 10° C. Fish were apparently still spawning on June 26, when water temperature was 12° C, but was suspended by June 27 when river temperature fell 7° C in 2 days following heavy rains. Whether activity resumed when favorable tempera- tures were again reached is unknown. A school of 500 to 600 spawners located in the Clearwater River on June 20, 1980, when the water tempera- ture was 18° C, had dispersed by the following day. Table 1 summarizes dates and water temperatures associated with spawning by northern squawfish in this and other studies. In all cases spawning occurred in June or July at temperatures between 10 and 20° C. Dates of spawning varied within this context as the required water temperature were reached at different times. In Cooper and Seeley Lakes (Hill 1962) and in Cascade Reservoir, spawning dates also varied in successive years as conditions varied. Different temperature regimes in tributaries to Cascade Reservoir were thought to explain the vari- able spawning dates in that system. The variations in times of spawning recorded in this study can also be explained by different temperature regimes in successive years and in the different systems. Site preference A total of 9 spawning sites were scattered throughout an 18 mile section of.the lower fastwater of the St. Joe River (Figure 4). Physical conditions at the locations of egg deposition at each site are summarized in Figures 5 and 6. Relatively deep areas in the river were favored by 53