The Chemical Composition of Settleable Solid Fish Waste (Manure) from Commercial Rainbow Trout Farms in Ontario, Canada

Abstract

The chemical composition of settleable faecal fish waste was determined from fresh manure samples collected at 12 commercial farms growing rainbow trout Oncorhynchus mykiss in Ontario, Canada. The manure samples from the commercial farms averaged 2.83% nitrogen (N), 2.54% phosphorus (P), 0.10% potassium (K), 6.99% calcium (Ca), and 0.53% magnesium (Mg) on a dry-weight basis. The concentrations of the metals, arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), iron (Fe), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), selenium (Se), and zinc (Zn) were also measured. Mean concentrations of these metals ranged from 0.05 mg/kg for Hg to 1,942 mg/kg for Fe. Fresh fish manure has similar levels of N, P, Ca, and Mg, and lower levels of K when compared to manure from beef, dairy cattle, poultry and swine. Fish manure tended to have a higher content of Mn, Cd, Cr, Pb, Fe, and Zn than most other livestock manures, but had lower levels of As, Se, Co, and Ni. The copper (Cu) content of fish manure was similar to all other livestock manures. The results from this study indicate that fresh fish manure is similar in its chemical composition to other livestock manures, and should be suitable for use as an agricultural fertilizer. In addition, it is hoped that these data will also help regulatory agencies and farmers make sensible and pragmatic decisions concerning the appropriate and safe disposal of manure wastes collected from land-based trout culture facilities.