Sea cages near to Fremantle Harbour are the focus of a new trial to establish the viability of fish food made from lupins. The rainbow trout farmed in this area are being fed on three different lupin-based mixtures. Cheaper to produce and more environmentally friendly than traditional feeds, data monitoring has shown that lupin-based food has had less impact on the environment than predicted, due to restricted levels of phosphorous and nitrogen in fish excreta, which usually contribute towards the growth of damaging algal blooms. Aquaculturalist Brett Glencross, from Fisheries WA, revealed that so far the trials have also shown that the trout displayed better growth and survival rates, but admitted that the physiological reasons for this were yet to be understood. The next stage of the experiment will involve increasing the sensitivity of testing methods on the impact of lupin feed, and measuring the nutrient levels on the seabed.