. Bulletin. Science; Natural history; Natural history. 1971 ASIA I' l( (I. AM INVASION IN ( A I II OHNIA Summer 64 n - 166 I - 20 m. Figure 4. Depth distributions of live El Capitan Cor- bicula during the summers of 1964 through 1967. Only transect 1 was sampled during summer 1966. Maximum depth for each period is designated by (z), and (n) designates numbers. The average clam depth distribution during sum- mer 1965 was deeper than during 1964. but maxi- mum depth during both periods was about the same. Destratification beginning during June 1965 did not significantly affect their maximum dept
. Bulletin. Science; Natural history; Natural history. 1971 ASIA I' l( (I. AM INVASION IN ( A I II OHNIA Summer 64 n - 166 I - 20 m. Figure 4. Depth distributions of live El Capitan Cor- bicula during the summers of 1964 through 1967. Only transect 1 was sampled during summer 1966. Maximum depth for each period is designated by (z), and (n) designates numbers. The average clam depth distribution during sum- mer 1965 was deeper than during 1964. but maxi- mum depth during both periods was about the same. Destratification beginning during June 1965 did not significantly affect their maximum depth distribution during summer 1965. The lake began to stratify during mid-March 1966. Air injection commenced March 19, 1966 and continued through October 17, 1966. The lake was well mixed during 1966 and oxygen was abun- dant at all depths. The lake remained mixed from October 1966 through February 1967. Clams were well distributed to all depths during the summer of 1966. Stratification developed normally during March 1967 (Fast, 1968). Hypolimnion oxygen concentra- tions declined, but did not fall below mg/1 by September 1967. Corbicula were again more restricted to the shallower depths. Over 70% of all clams collected during August 1967 were above 6 m. The remainder were distributed from 12 m to maximum depth of 26 m. Few live clams were found between 6 and 12 m ["he reason i"i Ihcii absence in this zone is unknown Mosl "i ii empty shells were collected below <• m Water volume and maximum depth flu I markedly during the study period Watci volume fluctuated between a II \ ID7 m'1 minimum |., ., x I07 maximum during the study period 11 able I). Not shown are rapid drawdowns durinj summers 1966 and 1967. rhesedrawdowns Colli large volume increases caused by wintei and spring rains. Corbicula concentrations were always greater .ii transect 2. Transect 1 had the next greatest concen- trations, and transect 3 was low (I ig. 7). DISC I SSION The size dist
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