Study to Reduce Parasitic Infestations of Yellow Perch in Flow-Through Outdoor Growout Systems
In April and May 2009, Blue Iris Fish Farm installed the flow through tank system which was used to conduct the study. After the system was set up, power was applied to ensure that the system was performing as designed.
On June 6, Blue Iris received a shipment of approximately 5000 feed trained perch fingerlings which had been housed indoors the first year and were observed and tested to be parasite-free. After two weeks of observation and ensuring that the fish were back feed, approximately 600 fish were introduced into each of four pond side tanks and an equal number introduced into an in-pond net pen.
Blue Iris monitored the fish daily, cleaned and maintained the tanks, and tabulated fish mortalities when observed. On a bi-weekly basis, Blue Iris collected grab samples from the tanks and pen, weighed a representative sample of fish and recalculated feed needs for each tank and pen. On a monthly basis, Blue Iris obtained thirty fish from each tank and pen and these were sent to the University of Wisconsin, Stevens Point for necropsy.
The study was carried out from June to August. From mid July to September, the project was plagued by severe drought. This lowered water levels in the pond as well as lowered oxygen levels over the whole pond (especially over night). Because of the low water levels, Blue Iris was unable to draw sufficient high quality water to maintain the experiment in the blue tank portion of the project. Therefore, between the middle and end of August the fish were removed from the blue tanks and placed in a separate pond. Thirty fish from each tank and the net pen were tested for parasites as was the typical procedure for the study.
No fish in the study were observed to become infected with the target species of parasites including the fish which were located in the pen in the pond. Because it could not be determined conclusively that the water was infected (no observed infections from any of the tanks or control), Blue Iris conducted a second set of tests.
The second tests were conducted between the end of September and the middle of November. At the end of September, Blue Iris seined 150 perch ranging in size from 74 mm to 135 mm all from the same pond water source as the original experiment was conducted. Based on size and weight, these fish ranged in age from five months to seventeen months. Fifty fish from this lot were taken for necropsy while the last 100 were saved in a pen in the pond. Approximately three weeks later (October 20), a second lot of 50 fish were seined. A necropsy was performed on these fish as well as a second lot of 50 fish from the pen. Finally, on November 14 a final 50 fish were seined and these along with the final 50 from the pen were tested for parasites. A total of 250 fish were tested between October 1 and November 14. With the exception of one fish, all had parasites. To understand the infection potential, fish were ordered in size from smallest to largest. Those that were approximately 10 grams (up to 100 mm) in size were deemed to be young of the year (approximately five months old). Some of the fish in this size range had as many as twenty parasites. Based on this aspect of the research, it can be said that the pond was definitely infested with parasites and that there was an active infection occurring during the summer of 2009. Moreover, there was a sufficient infestation to infect perch in the blue tanks.
Blue Iris introduced 600 parasite free perch in each of four pond side tanks and one net pen in June 2009. Water from a three acre pond was used to provide constant 24-hour flow through flow to the tanks. The pond was known to be infected with yellow grub and black spot, two parasites of perch which hatch from snails.
At monthly intervals, 30 fish from each tank and the pond pen were taken to a lab for necropsy. Parasites if found were to be tabulated (enumerated and measured) as were each individual fish (weight and length measurements).
Four batches of fish were tested, one prior to the installation of the study, one in July, and two in August. No parasites were found in any of the fish tested.
A second study was initiated at the end of September to determine if perch which inhabited the ponds were infected. The purpose of this second test was to determine if there was an active infection of parasites in the pond during the tests with the pond side tanks. Of the 250 fish tested, all but one were infected with parasites including those fish that had hatched in 2009. This indicates that there was an active infection in the pond and fish in the tanks were exposed throughout the test window.
What we have learned from this study is that fish that are in flowing water (tanks with flow through water) may not take up parasites even if exposed to water which is known to be infested with parasites. This is a major step forward for outdoor aquaculture where one of the hurdles is providing a fish to the food market which is free of parasites and of high quality.
This project was set up to be a single year study and has accomplished its goals. However, Blue Iris is continuing additional investigation into this arena and expanding the study(ies) by making modifications to the 2009 protocols and ramping up the production model to reflect farm economies. If the SARE program is interested in additional follow-up reports, Blue Iris would welcome the opportunity to provide additional follow-up. The following dialog provides information on proposed 2010 facility production.
The year 2010 will follow the 2009 pattern with the exception of the following:
1. Holding tanks will be moved to a point where the water intake will provide sufficient water quality to remove stress conditions in holding tanks.
2. Fish density will be increased to reflect normal production standards which should be realized on the farm.
3. After observing the various ways that systems can result in insufficient oxygen supply, Blue Iris will install an oxygen monitor which will automatically regulate oxygen regardless of failed power supply, pump failure, or low oxygen intake in water.
It is anticipated that Blue Iris will begin the 2010 study between May 15 and June 1, 2010. As in 2009, fish and water quality will be monitored daily and on a monthly basis a subsample of 30 fish will be removed from each tank and control pen for necropsy. The study should be terminated by the end of August or mid-September with another report following.
As of January 1, 2010, Blue Iris already completed reconstruction of a nine pond system. This included filling two ponds (creating one trickling filter) and regarding dikes to accommodate pond side tanks.
On October 2, 2009 Blue Iris hosted an onsite seminar in which fourteen students and two instructors from the aquaculture class of UW-Stevens Point, Stevens Point, WI attended. Blue Iris provided approximately three hours of instruction regarding the types of research which was being conducted at Blue Iris Fish Farm.
Blue Iris provided a power point presentation at the National Small Farm Trade Show and Conference in Columbia, MO in November 2009.
Blue Iris has been requested to provide two days of instruction for West De Pere High School. One day will be for in class instruction and the second day will be for students to visit Blue Iris Fish Farm. The onsite tour is scheduled to take place in April 2010 so that students can observe perch spawning, egg fertilization and incubation, and early life stages related to fish husbandry.
Blue Iris will be preparing a report to be published in the Creel (publication of the Wisconsin Aquaculture Association) which will describe the project and its results. There are over 300 subscribers to the Creel.
Blue Iris will be giving a power point presentation at the annual conference of the Wisconsin Aquaculture Association in March 2009. Recent conference attendance has ranged from 100 to 150 participants.
Blue Iris has worked closely with the University of Wisconsin, Stevens Point throughout this project. Both Bill West of Blue Iris and Chris Hartleb of UWSP are on the advisory committees for North Central Regional Aquaculture Center (NCRAC) and have independently submitted this research to NCRAC for additional funding (definitive results, multiple sites in a twelve state arena, and multiple species).