Understanding and managing suspended solids in intensive salmonid aquaculture : a review

Abstract

The intensive aquaculture of salmonids is a relatively young discipline within the animal husbandry sector. It differs to terrestrial livestock farming in one obvious and fundamental aspect – the aquatic environment. Besides great advantages such as buoyancy, the fluid medium also poses specific challenges for fish and fish farmers. One issue identified as a central problem in aquaculture is the presence of undissolved particulate matter in the water column. The ideal of fish living in pure, transparent water is seldom a reality as virtually every water body is subject to multiple inputs of solid matter, for example from the ground, the air and from the organisms living in it. In aquaculture, these solids are derived from both natural and anthropogenic sources, but by far the biggest input comprises excreted waste from the relatively high biomass of fish. The ratio of different inputs varies significantly between individual systems, dependent on factors such as the type of husbandry system, water exchange rate, the species being farmed, stocking density and the composition of the feed being supplied. This review aims to summarize potential sources of solid wastes in salmonid aquaculture, the properties of those solids and their implications for system stability, the quality of connected environments and the welfare of fish being reared. We will also review the expanding opportunities for solid management.