Survey of fish protective facilities at water withdrawal sites on the Snake and Columbia Rivers

Proliferation of water withdrawals and new pump intake and screen designs has occurred with the growth of irrigated agriculture along the Columbia and Snake Rivers. Concern for the protection of anadromous and resident fish populations resulted in formulation of a survey of the water withdrawal systems. The survey included distribution studies of juvenile fish near pump sites and field inspection of those sites to determine adequacy of screening for protection of fish. A total of 225 sites were inspected in 1979 and 1980, with a follow-up inspection of 95 sites in 1982. Results indicated a definite trend toward lack of concern for the condition of fish protective facilities. Only 4 out of 22 sites not meeting criteria in 1979 had been upgraded to acceptable conditions. Of more concern, 13 of the sites meeting criteria in 1979 were below criteria when reinspected in 1982. Some of the discrepancies included lack of protective screens, poorly maintained screens, and screens permitting excessive velocity that could result in impingement of larvae or small fish. A conclusion from these surveys is that if adequate protection for fish is to exist, screens for water withdrawals need to be properly installed, inspected, and maintained. (PDF file contains 40 pages.)

Humoral and protective response of Indian major carps to immersion vaccination with Aeromonas hydrophila

Fry of the Indian major carps, Catta catla (Ham.), Labeo rohita (Ham.) and Cirrhinus mrigala (Ham.) were immunized at 4 and 8 weeks post hatching (wph) by direct immersion in a suspension (10 super(8) cells ml super(-1))of heat inactivated Aeromonas hydrophila. Following the same procedure, booster dose was administered 20 days after the first immersion. Antibodies as well as protective response produced in both the groups after the first and the booster immersion were different and significant (P<0.05). No significant difference was found between the species in the two age groups. The specimens immunized 8 wph showed higher antibody titres and protection than the 4 wph group. C. catla had higher relative percent survival followed by L. rohita and C. mrigala.