Marc Legendre

Giant gourami (Osphronemus goramy) is one of the main freshwater fish of economic importance in Indonesia. Although this species has been reared for decades, particularly in the province of West Java, and naturally spawns in captivity, the availability of fry is still a limiting factor in aquaculture. Research efforts on giant gourami aquaculture are, however, limited and do not always address the difficulties encountered by fish farmers. The objectives of the present study were to provide the first description of giant gourami egg and fry production and highlight the main problems faced by farmers through targeted questionnaires and interviews. Our results show that the production of this species from eggs to juveniles is highly segmented, and there are currently no clear and standardized production methods. Farming practices vary greatly from one fish farmer to another. Climate factors (such as rain and temperature), proximity to urban areas, and the availability and quality of food are identified as the main limiting factors for egg and fry production. Based on a strengths, weaknesses, opportunities, threats analysis, we explore possible approaches to improve giant gourami aquaculture in Indonesia. The present study provides guidance for future research.

Several ecological services and functions are attributed to macrophytes, which may represent valuable resource for the ecological intensification of tropical fish farming. However, considering the multiple potential eco-services provided by macrophytes, the choice of the most appropriate species requires multiple criteria to assess these eco-services. Five floating macrophytes (Eichhornia crassipes, Lemna minor, Azolla filiculoides, Salvinia molesta and Salvinia spp.) were selected for this study. The six eco-services parameters compared among these macrophytes were: productivity (in % of seeded macrophytes), risk of non-productive cycles, nutritional value, impact on water quality, palatability (expressed as the percentage of plant ingested in 4 h) and ease of use. Experiments to determine these indicators were carried out in simple devices (net cages and plastic tanks) partially immerged in earthen ponds. The palatability of fresh macrophytes (whole or chopped) was studied in ponds using Osphronemus goramy juveniles. All indicators were scored from 1 to 5, and the highest score was assigned to the highest performer. These scores corresponded either to the evaluation of a single parameter (e.g. productivity) or to the average from scores of several parameters (e.g. nutritional score). Multiplier coefficients were applied for nutritional value and palatability. Azolla filiculoides showed the best scores for productivity; L. minor for nutritional value and palatability, and E. crassipes for the lowest risk of non-productive cycles and a positive impact on water quality. After integrating the scores in a multi-parameter matrix, A. filiculoides had the best overall score. The results of this approach to select macrophytes are discussed in light of the eco-services provided by macrophytes which may, in turn, promote the ecological intensification of tropical small-scale aquaculture.

Here, on the basis of published information upon over 800 species from 39 orders and 202 families, we analyse how the size of oil globules in fish eggs varies between reproductive guilds and environments with contrasting salinities. About 80% of marine fishes produce eggs with oil globules, the volume of which (V_O) never exceeds 9% of the egg reserves and averages 2%. These proportions vary very little between marine fish species producing pelagic or demersal eggs. Fewer freshwater fishes (about 40%) produce eggs with oil globules, but their globules are much larger (mean V_O of 10%) and their volumes vary considerably between reproductive guilds: V_O is on average 3–10 times lower in freshwater species with demersal eggs than among freshwater pelagophils and aphrophils (i.e., bubble nesters), where it averages about 40% (range of 23%–69%) of the egg reserves. These results support the idea that oil globules serve to hydrostatic lift in fresh waters, but not or very little in marine waters, where egg buoyancy can be achieved at a lower energy cost through egg hydration. Advantages and constraints of oil globules in fish eggs are discussed in the light of species producing eggs with very large oil globules (V_O > 20%): access to oxygen‐rich water layers that are indispensable for egg development vs. smaller size of larvae at first feeding, since the saturated lipids contained in oil globules essentially serve very little to tissue construction.

Ecological intensification is a new concept in agriculture that addresses the double challenge of maintaining a level of production sufficient to support needs of human populations and respecting the environment in order to conserve the natural world and human quality of life. This article adapts this concept to fish farming using agroecological principles and the ecosystem services framework. The method was developed from the study of published literature and applications at four study sites chosen for their differences in production intensity: polyculture ponds in France, integrated pig and pond polyculture in Brazil, the culture of striped catfish in Indonesia and a recirculating salmon aquaculture system in France. The study of stakeholders’ perceptions of ecosystem services combined with environmental assessment through Life Cycle Assessment and Emergy accounting allowed development of an assessment tool that was used as a basis for co‐building evolution scenarios. From this experience, ecological intensification of aquaculture was defined as the use of ecological processes and functions to increase productivity, strengthen ecosystem services and decrease disservices. It is based on aquaecosystem and biodiversity management and the use of local and traditional knowledge. Expected consequences for farming systems consist of greater autonomy, efficiency and better integration into their surrounding territories. Ecological intensification requires territorial governance and helps improve it from a sustainable development perspective.

The black-chinned tilapia Sarotherodon melanotheron heudelotii Rüppell 1852 (Teleostei, Cichlidae) displays remarkable acclimation capacities. When exposed to drastic changes of salinity, which can be the case in its natural habitat, it develops quick physiological responses and keeps reproducing. The present study focused on the physiological impact of salinity on male reproductive capacities, using gene expression as a proxy of acclimation process. Two series of experimental fish were investigated: the first one was composed of fish maintained in freshwater for several generations and newly acclimated to salinities of 35 and 70, whereas the second one consisted of the descendants of the latter born and were raised under their native salinity. Expression patterns of 43 candidate genes previously identified from the testes of wild males was investigated in the three salinities and two generations. Twenty of them showed significant expression differences between salinities, and their predicted function revealed that most of them are involved in the osmotic tolerance of sperm cells and/or in the maintenance of sperm motility. A high level of expression variation was evidenced, especially for fish maintained in freshwater. In spite of this, gene expression patterns allowed the differentiation between fish raised in freshwater and those maintained in hypersaline water in both generations. Altogether, the results presented here suggest that this high variability of expression is likely to ensure the reproductive success of this species under varying salinities.

The black-chinned tilapia Sarotherodon melanotheron heudelotii Rüppell 1852 (Teleostei, Cichlidae) displays remarkable acclimation capacities. When exposed to drastic changes of salinity, which can be the case in its natural habitat, it develops quick physiological responses and keeps reproducing. The present study focused on the physiological impact of salinity on male reproductive capacities, using gene expression as a proxy of acclimation process. Two series of experimental fish were investigated: the first one was composed of fish maintained in freshwater for several generations and newly acclimated to salinities of 35 and 70, whereas the second one consisted of the descendants of the latter born and raised under their native salinity. Expression patterns of 43 candidate genes previously identified from the testes of wild males was investigated in the three salinities and two generations. Twenty of them showed significant expression differences between salinities, and their predicted function revealed that most of them are involved in the osmotic tolerance of sperm cells and/or in the maintenance of sperm motility. A high level of expression variation was evidenced, especially for fish maintained in freshwater. In spite of this, gene expression patterns allowed the differentiation between fish raised in freshwater and those maintained in hypersaline water, in both generations. Altogether, the results presented here suggest that this high variability of expression is likely to ensure the reproductive success of this species under varying salinities.