Event Title

The source of elevated free carbon dioxide at the state fish hatchery, Springville, Utah

Start Date

2-4-2014 5:45 PM

End Date

2-4-2014 6:00 PM

Description

The Utah Division of Wildlife Resources operates the Springville State Fish Hatchery for raising rainbow trout for stocking lakes and ponds throughout Utah. Since February 2011 the hatchery has observed excessive physical activity among the trout, including jumping out of the hatchery raceways onto the concrete walkways, which can result from free CO2 levels above 15 ppm. Free CO2 levels in the hatchery water have been measured as high as 40 ppm, although the temporal variation has not been well-documented. Thus far, the problem has been addressed by passing the water through aerators before it enters the hatchery and by greatly reducing the food intake of the trout, which both increase costs and reduce production. Current mitigation measures have reduced free CO2 levels at the hatchery entrance by only 5 ppm, which is roughly equal to the increase in CO2 due to fish respiration from the hatchery entrance to exit. The objective of this study has been to determine the source of elevated free CO2 and provide the hatchery with recommendations for mitigation of the problem. The water source for the hatchery is a shallow pond, which is fed by 10 springs, both warm and cold. The pond was formerly used as a receptor for municipal stormwater and the bottom of the pond includes several feet of organic-rich mud, which may be a product of stormwater input. The objective was first addressed by collecting unfiltered water samples from each spring, the pond outlet, the hatchery entrance (outlet of aerator) and exit, and measuring temperature, pH, electrical conductivity, dissolved O2, and free CO2 on-site. The Hach DR-2700 Spectrophotometer was used to measure Cu, Fe, Zn, ammonia, nitrite and hardness, which are the most common stressors of rainbow trout. The discharge of each spring was estimated based upon flow over sharp-crested weirs. Mixing calculations showed that the chemistry and discharge of the springs predicted the chemistry of the pond outlet within (2-9) % for all parameters except Cu, Fe and Zn. The free CO2 at the pond outlet was over-predicted by 9%, indicating that the organic mud in the pond is not a significant contributor of free CO2. The heavy metals Fe, Cu and Zn were under-predicted by (22-27) %, suggesting that the organic mud is a sink for heavy metals. Mixing calculations showed further that the free CO2 level at the hatchery entrance could be reduced as low as 12 ppm with acceptable discharge and other chemical parameters by diverting the four springs with the highest CO2 levels. Current research involves improved documentation of the daily variation in free CO2 levels at the pond outlet and hatchery entrance and exit along with monthly collection of both filtered and unfiltered samples and on-site measurements at all of the above-mentioned sites. In addition to measuring nitrite, ammonia and hardness with the spectrophotometer, Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Ti are being measured using the PerkinElmer Optima-8000 ICP-OES. Further results will be reported at the meeting.

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Apr 2nd, 5:45 PM Apr 2nd, 6:00 PM

The source of elevated free carbon dioxide at the state fish hatchery, Springville, Utah

The Utah Division of Wildlife Resources operates the Springville State Fish Hatchery for raising rainbow trout for stocking lakes and ponds throughout Utah. Since February 2011 the hatchery has observed excessive physical activity among the trout, including jumping out of the hatchery raceways onto the concrete walkways, which can result from free CO2 levels above 15 ppm. Free CO2 levels in the hatchery water have been measured as high as 40 ppm, although the temporal variation has not been well-documented. Thus far, the problem has been addressed by passing the water through aerators before it enters the hatchery and by greatly reducing the food intake of the trout, which both increase costs and reduce production. Current mitigation measures have reduced free CO2 levels at the hatchery entrance by only 5 ppm, which is roughly equal to the increase in CO2 due to fish respiration from the hatchery entrance to exit. The objective of this study has been to determine the source of elevated free CO2 and provide the hatchery with recommendations for mitigation of the problem. The water source for the hatchery is a shallow pond, which is fed by 10 springs, both warm and cold. The pond was formerly used as a receptor for municipal stormwater and the bottom of the pond includes several feet of organic-rich mud, which may be a product of stormwater input. The objective was first addressed by collecting unfiltered water samples from each spring, the pond outlet, the hatchery entrance (outlet of aerator) and exit, and measuring temperature, pH, electrical conductivity, dissolved O2, and free CO2 on-site. The Hach DR-2700 Spectrophotometer was used to measure Cu, Fe, Zn, ammonia, nitrite and hardness, which are the most common stressors of rainbow trout. The discharge of each spring was estimated based upon flow over sharp-crested weirs. Mixing calculations showed that the chemistry and discharge of the springs predicted the chemistry of the pond outlet within (2-9) % for all parameters except Cu, Fe and Zn. The free CO2 at the pond outlet was over-predicted by 9%, indicating that the organic mud in the pond is not a significant contributor of free CO2. The heavy metals Fe, Cu and Zn were under-predicted by (22-27) %, suggesting that the organic mud is a sink for heavy metals. Mixing calculations showed further that the free CO2 level at the hatchery entrance could be reduced as low as 12 ppm with acceptable discharge and other chemical parameters by diverting the four springs with the highest CO2 levels. Current research involves improved documentation of the daily variation in free CO2 levels at the pond outlet and hatchery entrance and exit along with monthly collection of both filtered and unfiltered samples and on-site measurements at all of the above-mentioned sites. In addition to measuring nitrite, ammonia and hardness with the spectrophotometer, Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Ti are being measured using the PerkinElmer Optima-8000 ICP-OES. Further results will be reported at the meeting.