Evaluation of three organic fertilizers for paddlefish,Polyodon spathula, production in nursery ponds

Abstract

Organic fertilization of paddlefish (Polyodon spathula) nursery ponds with rice bran (RB), distiller's dry grain (DG) or cottonseed meal (CSM) was evaluated in nine 0.02-ha ponds over a 40-d period. Net yields (kg/ha) and growth rate of fish in ponds fertilized with RB were significantly higher (P ≤ 0.05) than with CSM, but not significantly different (P > 0.05) in ponds fertilized with DG. There was no significant difference (P > 0.05) in fish survival (RB 77%, DG 79%, and CSM 65%) for ponds receiving any of the three fertilizers. Secchi disk visibility and dissolved oxygen were significantly lower (P ≤ 0.05) in ponds fertilized with RB than in ponds fertilized with CSM and DG. Ammonia and nitrite levels differed only during week 3 and were significantly higher (P ≤ 0.05) in ponds fertilized with CSM and DG than in ponds fertilized with RB. Large cladocerans (Daphnia, Simocephalas, Scaphaleberis) were the dominant food items found in stomachs of fish in all treatments. RB proved to be superior to CS and DG as an organic fertilizer for paddlefish nursery ponds when evaluated in terms of fingerling growth, water quality, and zooplankton production.