20 research outputs found
Effects of chromium supplementation on the infrapopulations of Anacanthorus penilabiatus (Monogenoidea) and Piscinoodinium pillulare (Dinoflagellida) parasites of Piaractus mesopotamicus (Characidae)
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Evaluation of Current and Historical 10-inute-count screens at the Tracy Fish Collection Facility, Tracy, California
The U.S. Department of the Interior, Bureau of Reclamation\u27s Tracy Fish Collection Facilities (TFCF) 10-minute-count screen is a critical tool used to acquire sub-samples and provide an estimate of fish entering the facility. The introduction of a new screen in 1999, prior to fish screen retention comparisons, could possibly have altered TFCF salvage estimates. Three experiments were conducted during 2003 and 2004 to evaluate the retention efficiencies of the current and historical screens for juvenile delta smelt (Hypomesus transpacificus): (1) Wild Juvenile Delta Smelt Retention Comparison, (2) Evaluation of Bead Loss, and (3) Cultured Juvenile Delta Smelt Retention Comparison. In experiment No. 1 there was no significant difference between the mean number of juvenile delta smelt (20 to 30.5 mm in fork length [FL]) retained using the current (40.1 percent +/- 7.4; mean +/- standard error [SE], n = 6) and historical (34.5 percent +/- 7.9; n = 8) screens (p = 0.70). However, delta smelt with a greater maximum body depth than the maximum hole width were recovered outside of both screens. Experiment No. 2 was conducted to determine where, aside from screen holes, these fish may have been lost. The lowest success rate for retention of beads was achieved when no seal was used (8.6 percent for 4 mm, 41 percent for 10 mm). Retention of particles was highest (100 percent for beads \u3e 5 mm) when seals were used on the top and bottom of the screen, demonstrating that loss was occurring at both locations. In experiment No. 3 eight conditions were tested, using the two screen types. Retention was evaluated with and without seals with two class sizes of delta smelt (small, 20 to 25 mm in FL and large, 25 to 30 mm in FL). Retention of the small class size was significantly lower using the current screen with seals, compared to all three other treatment types (current + seal, 3 percent; current, 18 percent; historical + seal, 13 percent; historical, 15 percent, P = 0.002). However, no significant differences were detected among treatments of the large class size (current + seal, 23 percent; current, 33 percent; historical + seal, 59 percent; historical, 44 percent, P = 0.06). Experiments Nos. 1 and 3 support the hypothesis that there is no difference in retention between current and historical screens when seals are not used. SInce seals were not used historically, we conclude that the current and historical salvage data sets are comparable
109-117 BaskerÕille-Bridges
Abstract Ž . Ž A microparticulate diet was introduced on 8, 15, 22, 29 and 29 days post-hatch dph with . Artemia . Larvae were weaned from rotifers directly onto the diet in the first four treatments. Artemia were used in the fifth treatment and were fed for a period of 10 days. The microparticulate diet was able to completely replace live prey long before metamorphosis and larvae were weaned by 8.5 mm standard length. With the earliest introduction of the microparticulate diet on 8 Ž . dph, we observed 35% survival through 71 dph 21 mm . The survival of larvae from the other treatments was not significantly different and ranged from 32.7% to 39.4%. Weaning time did not have a significant affect on growth of cod larvae, as there were no differences when introducing Ž . the microparticulate diet on 8 or 29 without Artemia dph. However, supplementation of Artemia for 10 days had a growth-promoting effect. Larvae were larger than individuals from the other four treatments beginning on 29 dph and continued throughout the experiment. By 71 dph, Ž . they were 24 mm and weighed 20 mg dry weight . Successful culture of many finfish species is dependent on the use of live prey during the larval period. Early introduction of a microparticulate diet reduces the quantity of rotifers required and makes Artemia nonessential. This lowers production costs considerably by reducing the number of live animal cultures that must be maintained. However, until better diets are produced, careful consideration should be given to how early weaning affects production cost vs. growth rate of the larvae. q 2000 Elsevier Science B.V. All rights reserved
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Empirical and experimental analyses of secondary louver efficiency at the Tracy Fish Collection Facility: March 1996 to November 2007
The Bureau of Reclamation operates the Tracy Fish Collection Facility (TFCF) to remove fish from the San Francisco Bay-Delta water before that water is diverted south. We obtained empirical measurements of secondary louver efficiency at the TFCF for 33 species of fish. We also conducted insertion experiments with splittail, Pogonichthys macrolepidotus. In this study we found men louver efficiency for chinook (Oncorhynchus tshawytscha) juveniles to be 85.1 percent. We found the mean louver efficiency for striped bass (Morone saxatilis) juveniles to be 61.5 percent. Both of these efficiencies are lower than historical values (Bates et. al. 1960). For four species of fish, splittail, delta smelt (Hypomesus transpacificus), chinook salmon, and striped bass, we analyzed three independent variables and their influence on secondary louver efficiency. None of these independent variables (time of day, debris load, average channel velocity) was statistically significantly related to or a strong predictor of secondary louver efficiency. Splittail insertion experiments showed secondary louver efficiency was significantly higher during the day, and during the daytime a simulated heavy debris load significantly reduced efficiency. Combined empirical and experimental approaches provide the best approach to evaluation of factors influencing louver efficiency at the TFCF