Development of Notropis spilopterus (spotfin shiner) Aquaculture Propagation Methods and Techniques
Work activities to date included the setup of small indoor aquarium systems to conduct the first step of our research project, which was to determine if year round propagation of the spotfin was possible. The aquarium systems were needed to hold brood stock, induce spawning activity, hatch eggs, nurture fry, and grow zooplankton.
In the wild, spotfins spawn in our region from early May through late August. They lay their eggs in crevices usually found in rocks or between the bark of log snags. In order to induce spawning throughout the months of September through March, an artificial environment would need to be developed. The indoor aquarium systems noted previously were used for this purpose. The spotfins were allowed to proceed into a cool period of the Fall in their natural environment, and were then harvested and placed into the aquariums. A cool environment was maintained for a two month period while the spotfins adjusted to their new surroundings. The photoperiod was also maintained to simulate natural lighting conditions during this time period. Devices designed to mimic substrate crevices were made and suspended in the tanks for the spotfins to lay their eggs in.
During the first weeks of January, the water temperature and the photoperiod were gradually accelerated until Spring spawning conditions had been achieved. By the end of January, the male and female spotfins started exhibiting mating behaviors.
Research was also conducted in the area of both natural and commercially available food for the newly hatched fry. In the wild, spotfin fry feed on zooplankton. So it was necessary to artificially produce zooplankton indoors as a food source for the fry. We also wanted to determine if newly hatched fry were capable of surviving solely on commercially available food. If commercially available food could be used as a substitute for zooplankton, it would be very beneficial to subsequent larger scale production processes.
Also during this time period, research was conducted in the area of net pen design. Net pens will be needed in the second part of the research project, which will focus on the grow-out stage of the fry.
Grant funds to date were used to purchase and construct the aquarium systems, to purchase water quality meters, chemicals, and food, and to cover costs of labor.
By adjusting the water temperature and photoperiod in the aquarium systems and by providing appropriate substrate, we were successful in achieving propagation by the end of the second week in February. Shortly after mating signs were exhibited, the females began laying eggs in the artificial substrate. The substrate was removed and placed into a hatching tank after approximately five days, and new substrate was placed into the spawning tanks. The spotfins continued laying eggs as long as the water temperature and photoperiod were maintained at natural spawning conditions.
In the hatching tanks, the substrate remained until the eggs all hatched which was approximately 10 to 12 days. Hatching was found to occur much sooner if water temperature was increased 10 degrees. At first, zooplankton was introduced in combination with a commercially prepared food for the newly hatched fry to consume. Due to the large number of fry in the hatching tank, it was difficult to determine mortality. However, a significant number of fry survived past two weeks and were transferred into a nursery tank. Zooplankton was gradually decreased until the fry were solely on a commercially prepared food.
Some of the problems we encountered that resulted in fry mortality were related to water quality issues and food types. The high density of fry and the feeding regimen quickly overloaded the biofilter and led to water quality degradation in the small nursery tanks. Frequent water changes were necessary to address this problem, which also contributed to mortality induced by stress. It is suspected that spotfin fry at early stages after hatching are very sensitive to water quality, and therefore it is necessary to closely monitor the water and stocking density in the tanks. A larger capacity system would likely minimize the monitoring and decrease mortality in small fry.
Food nutrition also caused us problems in developing fry. After about 10 weeks of feeding, many of the spotfins exhibited spinal deformations (Lordosis scoliosis). While these permanent deformations did not generally contribute to mortality, they affected the growth rate of the fry compared to those without the deformity. A change was made in the commercially prepared food to provide other commercially available foods with better nutritional value. The results were positive and seemed to prevent newly hatched fry from developing the deformity. However, the new diet did not reverse the damage already done to the more mature spotfins.
The fry were held for six months and released into the wild in October, 2006. The average length of the fry without deformities was approximately 1 inch. The growth rate in the small aquariums was much less than expected. This is likely due to feeding rates, absence of grading, and tank size. Grow out will be conducted during the summer of 2007 as described below. We anticipate growth rates to increase substantially next year.
WORK PLAN FOR 2007
Because of the problems encountered during the initial propagation phase, we plan to reproduce the research experiment on a slightly larger scale for two primary reasons. First, we want to test our hypothesis that nutrition was the primary cause of the spinal deformities in young fry. We also want to see if newly hatched fry can survive solely on the enhanced commercially prepared food diet. In addition, we want to confirm that a larger system with controlled stocking density will minimize routine maintenance and improve water quality, which previously led to mortality in the smaller systems. The second reason is to produce a sufficient number of fry to proceed with the subsequent research, which is grow out in a net pen placed in a natural water body.
Net pens will need to be constructed out of varying dimensions and net opening sizes to contain the fish as they grow. Based on our current research, we have determined that the initial pens will need to be the following dimensions (6’L x 4’W x 8’D) with an initial net opening size of 1/32 to1/16 inch. Based on growth information from this year, the spotfin fry should be transferred to this initial net pen 6 to 8 weeks after hatching. The dimensions of the subsequent net pens and the opening sizes will be based on the growth rate in the wild, which is expected to be much faster due to natural food sources and the abundance of zooplankton.
Critical issues that have already been identified in this final phase of the research are diminished oxygen levels due to algal growth on the nets, and predation. We will possibly experiment with treated nets to minimize routine cleaning associated with algal growth. If necessary, we may also experiment with air bubblers to minimize the impacts of algal growth and keep oxygen content at acceptable levels. Predation from birds will be controlled by nets covering the top of the net pen. Predation from other animals such as snapping turtles, raccoons, and muskrats will be controlled by aggressive trapping. Cannibalism could be a problem and will be addressed by routine grading of the fry.
No scheduled field days or demonstrations were held this year due to the location of the project and its small scale. However, information from our project was shared with our local OSU (Ohio State University) aquaculture extension educator and collaborator, Shawn McWhorter. This information was used to replicate our results in a larger system constructed at his facility in Bowling Green, Ohio with our assistance. Similar results were achieved in this system, which required less maintenance and minimized mortality due to better water quality. This system was more available for observation by local aquaculturists, potential aquaculturists, other extension educators, and visitors that frequent his facility. By constructing this system together, Mr. McWhorter was able to help us disseminate the information we have obtained to date in addition to providing a visual representation of our initial experiment. For instance during a recirculation workshop held at the OSU facility on December 11, 2006, the results of our research and the system that was constructed was discussed by both us and Shawn with the 17 participants. There was a lot of interest in the baitfish industry in Ohio, especially since the emergence of VHS and the recent transportation restrictions enacted by the federal government. The spotfins produced from this system were grown-out and released into a 1 acre pond. They will be used in future research at the OSU extension office planned for 2007.
Next year (2007), information will continue to be shared with the OSU extension office regarding propagation and final grow-out in net pens. Opportunities should be available to have small groups of aquaculturists and interested parties observe the spotfins during grow out using net pens in a natural water body. Another larger replicate system has recently been constructed at the OSU extension office for additional research. The results of this research will help to further disseminate our information to a larger audience. In addition, Shawn is scheduled to give a presentation on our findings at the Ohio Aquaculture Association annual meeting in February, 2007. This presentation will be to a much larger audience and may include aquaculturists from nearby states. Finally, we may publish a short abstract to be included in the Ohio Aquaculture Association newsletter later in 2007 so that additional information can be shared pertaining to grow out with net pens.