Temperature is the main abiotic factor that influences the life cycle of poikilotherms. The present study investigated the thermal tolerance and phenotypic plasticity of several parameters (development time, morphometric measures, bioenergetics) for both embryos and fry of a cold stenothermal fish species, brown trout (Salmo trutta L.) in order to allow for a holistic evaluation of the potential effects of temperature. Five temperatures (4°C, 6°C, 8°C, 10°C, and 12°C) were tested, and the effects of temperature were analyzed at three stages: hatching, emergence, and first food intake. A mean of 5,440 (S.E. ± 573) eggs, coming from seven females and seven males (seven families) captured close to Linkebeek (Belgium), were used for each temperature. Maximum survival of well-formed fry at first food intake and better use of energy budget were found at 6°C and 8°C, temperatures at which the possible contribution to the next generation should therefore be greatest. At 12°C, the experimental population fell dramatically (0.9% survival rate for well-formed fry at first food intake), and fry had almost no yolk sac at first food intake. The present results on survival at 12°C are in accordance with predictions of a sharp decrease in brown trout numbers in France over the coming decades according to climate change projections (1°C to 5°C temperature rise by 2100 for France). At 10°C, there was also a lower survival rate (55.4% at first food intake). At 4°C, the survival rate was high (76.4% at first food intake), but the deformity rate was much higher (22% at first food intake) than at 6°C, 8°C, and 10°C. The energetic budget showed that at the two extreme temperatures (4°C and 12°C) there was less energy left in the yolk sac at first food intake, suggesting a limited ability to survive starvation.

The first trials of farming fish species for human consumption might date back to 8,000 yr ago, with the managed aquaculture of common carp (Cyprinus carpio) in Henan Province, China ( Nakajima et al., 2019). Evidence of farming was also found on Egyptian tombs from about 3,500 yr, with some kind of control over the reproduction of Nile tilapia (Oreochromis niloticus) in irrigation ponds ( Teletchea, 2019a). In Europe, the farming of common carp in ponds was already developed during the Middle Ages. The Italian “Vallicoltura” (extensive farming of various marine species in coastal lagoons and large open waterbodies) dates back to the 15th century. The French trout culture started around the second half of the nineteenth century ( Teletchea, 2019a). In North America, aquaculture started about 100 yr ago. In Africa, aquaculture dates back to the 1940s. In Australia, New Zealand, and diverse Pacific Island states, the development of aquaculture is even more recent. In conclusion, the rearing of fish is very old ( Gjedrem et al., 2012), particularly in Asia ( De Silva et al., 2009), even though this is not before the early 1980s that aquaculture truly boomed, becoming the fastest-growing food-production sector globally ( Teletchea, 2016a; FAO, 2019). In only four decades, aquaculture production has surpassed capture fisheries, and today more than half of the fish destined to human consumption are farmed globally ( Teletchea 2016a; FAO, 2019; Houston et al., 2020). The exponential growth of aquaculture has relied partly on the domestication of an increasing number of fish species ( FAO, 2019; Teletchea, 2019b). The aim of the present article is to discuss briefly 10 partly unanswered questions linked to fish domestication, which could be taken into account to promote a more sustainable global aquaculture production.

Domestication is a long and endless process during which animals become, generations after generations, more adapted to both captive conditions and humans. Compared to land animals, domestication of fish species has started recently. This implies that most farmed marine fish species have only changed slightly from their wild counterparts, and production is based partly or completely on wild inputs. In the past decades, global marine fish production has increased tremendously, particularly since the 1990s, to reach more than 2.2 million tons in 2013. Among the 100 marine fish species listed in the FAO’s database in 2013, 35 are no longer produced, and only six have a production higher than 100,000 tons. The top ten farmed marine species accounted for nearly 90% of global production. The future growth and sustainability of mariculture will depend partly on our ability to domesticate (i.e., control the life cycle in captivity) of both currently farmed and new species.

In the origin of modern humans, hunting of wild animals and gathering of wild plants in nature were the primary subsistence strategies. Yet, about 12,000 years ago, the domestication of plants and animals began. The two main goals of the present chapter are to briefly describe (i) how wild animals were domesticated and (ii) what are the main biological consequences for the major farmed species (cattle, pig, sheep, goat, and horse). During about 98% of their domestication history, domestic animals have been managed in a sustainable way by farmers, followed by a period of strong selection about 200 years ago to produce hundreds of well-defined breeds. A few decades ago, the selection pressures have further increased, leading to a few industrial breeds, which were introduced in numerous countries, most often at the expense of local breeds. Within a few decades, we thus might lose most of the highly valuable farm animal genetic resources that humans have gradually selected over the past millennia. Consequently, priorities should be given to preserve the genetic resources in marginal or rare breeds, and selection programs should aim at restoring the genetic diversity in industrial breeds.

The first trials of fish farming date back about 3500 years. Yet, this is only in the 1980s that the exponential development of aquaculture occurred, driven by the strong demand for aquatic products, whereas global capture fisheries started decreasing. The strong increase of aquaculture production has relied chiefly on the domestication of an increasing number of fish species. Nevertheless, only a limited number has reached a high level of domestication. The aim of this chapter is to describe the domestication history of five of the main farmed fish species globally in which all have reached Level 5 and one example that has reached Level 2 only. These six species were chosen because enough scientific literature was available to describe their domestication history that allows illustrating both ancient and recent fish domestication.