Effect of feed and feeding in the culture of salmonids on the marine aquatic environment: a synthesis for European aquaculture

Abstract

While marine aquaculture has grown rapidly, so have concerns regarding the environmental impacts caused by the industry. In particular, increasing discharges of solid and dissolved fish excretions, nutrients and therapeutic chemicals have coincided with greater public awareness of the possibility of environmental damage. This has stimulated a number of criticisms, drawn from a wide spectrum of interests, ranging from the use of natural fish stocks to produce fish meal for aqua feeds to the effects of enhanced nutrient input on the coastal marine environment. The present study reviews available information on the environmental effects of feeding practices in salmonid aquaculture in Europe. Accumulation of waste food and fish faecal material results in changes in the sediment under fish cages, characterized by a low redox potential, high content of organic material and accumulation of nitrogenous and phosphorous compounds. Although significant environmental impacts have been reported in the literature at distances of up to 100 m from the cages, in general such impacts are reported to be localized to within 20-50 m around the cages. For farmed salmon and trout, mass balance models have been developed for nitrogen and phosphorus, indicating that 50% of the nitrogen and 28% of the phosphorus supplied with the food is wasted in dissolved form. The maximum nutrient release can be estimated from the hydrographic conditions in the immediate vicinity of the farm, such as water volume, tidal water exchange and currents. At present production levels, improvements in the feeding efficiency and Ó Springer Science+Business Media B.V. 2006 feed quality of aquafeeds could reduce waste and consequent environmental impacts.

An overview of the utilisation of microalgae biomass derived from nutrient recycling of wet market wastewater and slaughterhouse wastewater

“…High nutrient content such as carbon, phosphorus, and nitrogen from uneaten fish food and faeces leads to eutrophication and the outbreak of diseases. However, the improvement of feed quality can help reduce nutrient pollutants in water columns (Focardi et al 2005;Mente et al 2006). High level of nutrients in water columns from fish farming may create favourable conditions for the growth of dinoflagellates (Mente et al 2006) and lead to harmful algal blooms (HAB) which can deplete oxygen level, reduce light penetration, and release toxins associated with paralytic shellfish poisoning.…”

“…However, the improvement of feed quality can help reduce nutrient pollutants in water columns (Focardi et al 2005;Mente et al 2006). High level of nutrients in water columns from fish farming may create favourable conditions for the growth of dinoflagellates (Mente et al 2006) and lead to harmful algal blooms (HAB) which can deplete oxygen level, reduce light penetration, and release toxins associated with paralytic shellfish poisoning. The previous studies by Joseph et al (1988) and Michels et al (2014) had turned problems into opportunities in which integrated aquaculture systems were used to convert waste into algal biomass.…”

“…The production of aqua feeds is essential as a source of dietary lipids (fish oil) and proteins (fish meal). Dietary protein levels for different species vary from 30 to 57%, and 5 to 8% for dietary lipid levels (Mente et al 2006). Other critical problems related to the wild catch of fisheries include high cost and limited stock.…”

“…It also involves low-cost fluctuation and sustainable production (Mente et al 2006). Currently, the replacement of fishmeal is constrained by anti-nutritional factors that cause adverse effects on fish health.…”

Integrated Multitrophic Aquaculture: Filter Feeders Bivalves as Efficient Reducers of Wastes Derived from Coastal Aquaculture Assessed with Stable Isotope Analyses

“…Whereas the dissolved compounds are easily dispersed and diluted in the water column, the particulate compounds sink to the sea floor, causing severe modifications of the physical and chemical characteristics of the sediment and the community dynamics of marine seagrass and benthic fauna (Brown et al, 1987;Karakassis et al, 2000;Mente et al, 2006). The severity and extend of the environmental impact depends on a large number of factors, such as local hydrodynamics, water depth and total output from fish farms.…”