Abstract
Reduced walleye (Sander vitreus) fingerling production possibly related to nuisance filamentous green algae and overly stable water chemistry patterns is a concern in earthen-substrate ponds at Blue Dog State Fish Hatchery, South Dakota, USA. We describe the success of alfalfa (Medicago sativa) meal (AFM, n = 2), alfalfa meal plus soybean (Glycine max) meal (AFM + SBM, n = 1), and alfalfa meal plus liquid 28N:0P:0K (AFM + 28:0:0, n = 1) at achieving walleye production objectives (>104,000 walleye and 32 kilograms/hectare) as well as the occurrence of filamentous green algae and the associated patterns of ammonia-nitrogen, pH, and dissolved oxygen in earthen-substrate ponds. Walleye production objectives were only achieved when filamentous green algae were absent preceding harvest, which occurred in one pond that received AFM and in the pond that received AFM + 28:0:0. The presence of filamentous green algae preceding harvest was associated with higher dissolved oxygen and pH, whereas declines in these variables occurred when filamentous green algae were absent. Organic fertilizer alone exhibited low ammonia-nitrogen (<0.1 mg/L) despite the substitution of higher protein content soybean meal, but supplementation with 28:0:0 increased ammonia-nitrogen to 0.23 mg/L. These findings highlight the reduction in walleye fingerling production that occurred in the presence of filamentous green algae and the unpredictability of results when two earthen-substrate ponds are treated exactly the same with alfalfa meal. Achievement of walleye production objectives, lack of nuisance filamentous green algae, and promotion of favorable patterns in water chemistry warrant future experimentation with alfalfa meal supplemented with 28:0:0 in earthen-substrate ponds at this hatchery.
Highlights
Earthen-substrate ponds at Blue Dog State Fish Hatchery (BDSFH) have historically received alfalfa (Medicago sativa) fertilizer to promote food webs that nourish walleye (Sander vitreus) fingerlings to approximately 30 mm total length [1]
We describe the success of alfalfa (Medicago sativa) meal (AFM, n = 2), alfalfa meal plus soybean (Glycine max) meal (AFM + SBM, n = 1), and alfalfa meal plus liquid 28N:0P:0K (AFM + 28:0:0, n = 1) at achieving walleye production objectives (>104,000 walleye and 32 kilograms/hectare) as well as the occurrence of filamentous green algae and the associated patterns of ammonia-nitrogen, pH, and dissolved oxygen in earthen-substrate ponds
Walleye production objectives were achieved in the AFM (Pond 34) and AFM + 28:0:0 ponds when filamentous green algae were absent (Table 2)
Summary
Earthen-substrate ponds at Blue Dog State Fish Hatchery (BDSFH) have historically received alfalfa (Medicago sativa) fertilizer to promote food webs that nourish walleye (Sander vitreus) fingerlings to approximately 30 mm total length [1]. Nuisance filamentous green algae (e.g., Hydrodictyon, Cladophora, Pithophora) can occur in these ponds, which reduce fish production through physical entanglement [2] and utilization of nutrients that are not directed into prey for fish. Filamentous green algae reduce efficiencies of hatchery pond production. Lined ponds enhance walleye fingerling harvest metrics [3] [4] and generally lack filamentous algae during pond harvest (unpublished data from BDSFH). Manipulating fertilizer regimens in earthen ponds to achieve these water chemistry patterns may reduce the likelihood of filamentous green algae, while improving walleye fingerling production
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.