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Population dynamics of the gastropod Theodoxus jordani (Sowerby) in the Shatt Al-Arab river |
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| Authors: | KHALID Y AL-DABBAGH JAMAL Y LUKA |
| Institution: | Department of Zoological Sciences, Biological Research Center, Scientific Research Council, Jadiriya, Baghdad, and Fisheries Research Center, Zafaraniya, Baghdad, Iraq |
| Abstract: | SUMMARY. 1. Measurements of the population density of Theodoxus jordani were made for the period July 1980 until June 1981. Numbers showed a well-defined pattern of fluctuation and varied between 390 in February and 1804 snails m 2. The population age structure revealed that the snail was semelparous, and that one generation dominated the population for most of the year. 3. The breeding season was long. Snails laid eggs from early December to the end of April. Eggs were laid in protective capsules and one snail developed per capsule. Total population natality estimated from field samples was 9813 snails m 4. Age specific mortality was high immediately after recruitment, low during the juvenile stages, and increased sharply at the adult stage with the onset of reproduction. |
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