Impact of shellfish aquaculture on coastal energy fluxes: insights from fatty acid profiling

There is a growing concern about the ability to produce enough nutritious food to feed the global human population in this century, the so-called 9 billion people question. In addition, environmental conflicts and a limited freshwater supply constrain further developments in agriculture and global fisheries landings have been declining since the mid-1980s. Yet, more and more hope is focussed on the use of marine resources to support the growing human population. In light of these future perspectives, the Food and Agriculture Organization (FAO) has pointed to aquaculture as the most promising future source for food protein for humans. Many scientists perceive this productive model as a key element for the pressure alleviation on wild stocks. In terms of productivity, fish production is much more efficient than land farming as it takes 15 times more feed to produce 1 kilogram of beef than to produce 1 kilogram of carp. The weakest point on the sustainability of this exploitations is the dependence on wild stocks to obtain good quality fish meal. A sustainable exploitation of marine resources is then necessary in order to prevent a total collapse of marine food webs (fishing down the food web). However graphics shown that fish oil and fishmeal production have reached an asymptote even with a constant increase on aquaculture production. The FIFO index (Fish In Fish Out) is in constant decrease and research on new feeding techniques gives some lights on this problem. It is also notable that sustanaible labelling e.g. the Aquaculture Stewardship Council' certificate is gaining importance. In aquaculture installations a lot of fish feed (1-25 %) is lost as solid particulate organic matter in the form of unconsumed feed pellets and faecal material. The organic loading can eventually cause organic enrichment of the water column and eutrophication. One of the most successful attempts to recycle this waste overload from fish farming operations is obtained by simultaneously culturing organic extractive species such as bivalves or algae, with fed aquaculture in so-called Integrated Multi-Trophic Aquaculture (IMTA). The optimal functioning of an IMTA installation and its impact on the surrounding water largely depends on the efficiency of trophic interactions between the target species. The present study aims to test the energy flow between the species involved in particular IMTA installations. The feeding efficiency of organisms is expected to depend on local environmental conditions e.g. naturally available primary production, overload of nutrients etc. By sampling different installations (ponds, open sea, high vs. low nutrient levels, small vs. large installations) these aspects will be tested. Species of different trophic levels (primary producers, first and second level consumers) and different trophic guilds (detritivores vs. herbivores, filter feeders vs. deposit feeders) will be analysed by means of trophic markers e.g. fatty acid profiling and stable isotopes. These markers will allow to analyse the energy flow in different IMTA installations. This will give arguments to conclude on the effectiveness of IMTA in different contexts and the suitability of different species to be integrated in it.

ISCED Categories

The highlighted icons, represent the fields of education (in compliance with ISCED Classification) engaged during this course/programme.

0831 - Aquaculture", "0521 - Ecology