In general, the catch by month declined as the season advanced 

 dirring both years. With the exception of the low catch in March of 1957^ 

 the catch started at a high level in April of both years and declined to 

 a low level during August. 



Brail sampling. --Twenty- three species of mussels were represented 

 in brail samples made in the commercial fishing areas on Chickamauga, 

 Guntersville, Wheeler, and Kentucky Reservoirs during 1957 (table 3). Of 

 these, 15 species are of commercial value to the industri'-. Although the 

 pigtoe is the most abundant species in the catch from the lower part of 

 the river, abundance of this species increased at upstream locations. 



The more intensive sampling program on Wheeler Reservoir provided 

 a comparison of the catch per square yard per drag between the harvest 

 seasons of 1956 and 1957- A total of 15 species occurred in the 1956 

 samples and l6 species in the 1957 samples (table k) . The catch per drag, 

 for all species combined, declined 29 percent from 1956 to 1957- The sea- 

 sonal catch per drag was highest in April and, in general, declined as the 

 season progressed. 



Altho\igh the pigtoe accounted for over 80 percent of the commercial 

 catch in Wheeler Reservoir in both 1956 and 1957> brail samples showed that 

 the mean catch per drag in 1957 (0.264 per square yard) decreased by 33 ^^ 

 percent below the level for 1956 (0.391 pei" square yard). 



Statistical analysis showed that the difference _represented by the 

 decrease during the second year was highly significant (table 5) • 



The nianber of brail drags made over the harvest area in Wheeler 

 Reservoir during 1956 and 1957 'was estimated to determine the degree of 

 fishing effort. Based on the total number of pigtoes harvested per square 

 yard (table 2) and the mean number caught per drag (table 5)^ the result 

 indicates that an average of 13.7 drags was made over the entire fishing 

 area in 1956 and 10. U drags in 1957* This suggests that fishing effort 

 declined approximately 2^4- percent during the latter year. 



The data arrayed in table 6 and illustrated in figiore 3, demon- 

 strate the relationship among total catch per unit area, catch per unit 

 of effort, and fishing effort. From observation, approximately 25 boats 

 per day fished the area in April while the catch rate was high, and only 

 4 or 5 boats operated per day when the catch rate declined during the 

 latter part of the season. 



Length frequency data from 11,658 pigtoe mussels, selected at 

 random from the commercial catch in ^ mainstream reservoirs, provided a 

 comparison of the size distribution of different populations at loca- 

 tions between river mile 190 and river mile 519 (table 7) • The mean 

 lengths varied from Jl.l mm. in Wlieeler, to 83.8 mm. in Chickamauga. The 

 samples from Guntersville and Kentucky Reservoirs had mean lengths between 



10 



