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The macroalga Oedogonium intermedium has a diverse elemental profile, high energy potential, high lipid content, a high proportion of essential amino acids and a total concentration of protein with the potential to meet the nutritional requirements of herbivorous fishes. The aim of this study was to assess growth, condition, colouration and reproductive output in an herbivorous ornamental fish. The catfish Ancistrus cirrhosus was fed one of three pelletised experimental feeds, Oedogonium, a formulated commercial feed and a 50:50 mix of the two, over a 10 month trial. After 10 months, fish that were fed exclusively on Oedogonium had equivalent growth rates, body condition, colouration, fecundity and fertilisation rates compared to those fed the commercial and mixed feeds. The absence of any major differences of these characteristics between feeds, especially between Oedogonium and the commercial feed, demonstrates the viability of Oedogonium as a feed, or significant feed ingredient, for this herbivorous fish. As such, linking the cultivation of Oedogonium with the production of herbivorous fish may provide an ideal application for Oedogonium.

Guidelines for the introduction of Seaweed Farming asan alternative livelihood opportunity in the coastal zone

The management of the coastal zones of the western Indian Ocean (WIO) is seriously compromised by the over-exploitation of coastal fisheries stocks. This overexploitation is largely due to the over-development of artisanalfisheries, which are particularly difficult to manage.

In fact, there are really only two ways to address this problem: 1) bysimply legislating to reduce the fishing effortsand then enforcing that legislation, which is politically very difficult, or 2) by linking the mutually agreed introduction of less punitivemanagement measures (for example, gear restrictions or closed areas or seasons) with the creation of alternative livelihood opportunities for fishers.

Marine aquaculture is a one such alternative that is increasingly popular following a number of successful introductions in the region. One example is the development of seaweed farming, which has been promoted over the last 20-years but other types of marine aquaculture also have potential as alternative livelihoods. These include the culture of prawns, fish, bivalves, crabs and sea cucumbers.

Seaweeds (marine macroalgae) are autotrophic organisms capable of producing manycompounds of interest. For a long time, seaweeds have been seen as a great nutritional resource,primarily in Asian countries to later gain importance in Europe and South America, as well as inNorth America and Australia. It has been reported that edible seaweeds are rich in proteins, lipids anddietary fibers. Moreover, they have plenty of bioactive molecules that can be applied in nutraceutical,pharmaceutical and cosmetic areas. There are historical registers of harvest and cultivation ofseaweeds but with the increment of the studies of seaweeds and their valuable compounds, theiraquaculture has increased. The methodology of cultivation varies from onshore to offshore. Seaweedscan also be part of integrated multi-trophic aquaculture (IMTA), which has great opportunitiesbut is also very challenging to the farmers. This multidisciplinary field applied to the seaweedaquaculture is very promising to improve the methods and techniques; this area is developed underthe denominated industry 4.0.

The integrated aquaculture of the tetrasporophyte of Asparagopsis armata Harvey (Falkenbergia rufolanosa) using fish farm effluents may be viable due to the species high capacity of removing nutrients and its content of halogenated organic compounds with applications on the pharmaceutical and chemical industries. In order to optimize the integrated aquaculture of F. rufolanosa, we followed the daily variation of the potential quantum yield (Fv/Fm) of PSII on plants cultivated at different biomass densities and different total ammonia nitrogen (TAN) fluxes to check if they are photoinhibited at any time of the day. Moreover, the photoinhibition under continuous exposure to highly saturating irradiance and its potential for subsequent recovery in the shade was assessed. The potential for year round cultivation was evaluated by measuring rates of O2 evolution of plants acclimated at temperatures ranging from 15 to 29 °C, the temperature range of a fish farm effluent in southern Portugal where an integrated aquaculture system of F. rufolanosa was constructed. Photoinhibition does not seem to be a major constrain for the integrated aquaculture of F. rufolanosa. Only when cultivated at a very low density of 1.5 g fresh weight (FW) l−1 that there was a midday decrease in maximal quantum yield (Fv/Fm). At densities higher than 4 g FW l−1 , no photoinhibition was observed. When exposed to full solar irradiance for 1 h, F. rufolanosa showed a 33% decrease in Fv/Fm, recovering to 86% of the initial value after 2 h in the shade. A midday decline of the F. rufolanosa Fv/Fm was also observed under the lowest TAN flux tested (∼6 μM h−1 ), suggesting that this fast and easy measurement of fluorescence may be used as a convenient diagnostic tool to detect nutrient-starved unbalance conditions of the cultures. Maximum net photosynthesis peaked at 15 °C with 9.7 mg O2 g dry weight (DW)−1 h−1 and remained high until 24 °C. At 29 °C, the net oxygen production was significantly reduced due to a dramatic increase of respiration, suggesting this to be the species' lethal temperature threshold. Results indicate that F. rufolanosa has a considerable photosynthetic plasticity and confirm it as a good candidate for integrated aquaculture at temperatures up to 24° C and cultivation densities of at least 5 g FW l−1 . When cultivated at these densities, light does not penetrate below the first few centimetres of the surface zone. Plants circulate within the tanks, spending around 10% of the time in the first few centimetres where they are able to use efficiently the saturating light levels without damaging their photosynthetic apparatus.