**3. Acquiring knowledge on the biology of** *P. fluviatilis* **and**  *P. flavescens*

A the end of the 1980s and beginning of the 1990s, an in-depth analysis of the available literature on the biology of Eurasian perch and a North American close species, the yellow perch *P. flavescens*, was performed to better evaluate potentialities of this species. We first analyzed general articles as well as book chapters [12–22]. Then, we considered more specific studies focusing on the characteristics of populations inhabiting particular aquatic areas [13–27]. In the meantime, because some farming trials were already performed on yellow perch in the United States (large lake areas), a similar approach was realized aiming at establishing a synthesis of knowledge acquired on the zootechny of this sister species [28–38]. At this period, yellow perch was considered as the reference to promote the farming of Eurasian perch. This choice was reinforced by the fact that questioning about the rearing systems (ponds or recirculated systems) was similar. Based on these bibliographical analyses, preliminary thoughts resulted in the emergence of farming possibilities in Europe [39], and perciculture (i.e., farming of perch) was proposed as a possible way to diversity inland aquaculture in Europe [40].

#### **3.1. Study of the life cycle of perch in natural conditions, first zootechnical trials, and choice of the rearing system**

During the 1990s, researches were undertaken to first better know the life cycle of the species in local aquatic ecosystems, mainly in the Mirgenbach reservoir and Lindre ponds (Moselle, France), and second to determine the potential of this species at different stages (larval rearing, on-growing). The choice of the Mirgenbach was linked to the fact that this reservoir presents heated waters due to the nuclear power plant of Cattenom and could potentially present thermic conditions more favorable for the growth of perch, in the perspective of a future economic development. These field studies allowed describing the feeding regime, growth (relation size-weight), composition of the main tissues (muscles, gonads, liver, viscera), as well as the reproductive cycle [27, 41–44]. These data constituted the frame of reference and brought the basis for future experimentations, such as the control of the reproductive cycle. In parallel to these descriptive studies, first trials of acclimatization were realized using perch sampled at different development stages in natural conditions (e.g., egg ribbons mainly from the Leman Lake, INRA Thonon-les-Bains, Haute-Savoie, France), polyculture ponds (young perch of 4–20 g for Lorraine fish farm ponds), or rivers (eggs ribbons from Meuse). The acclimatization of young perch, either juveniles or sexually mature individuals, with diverse features from one year to another, was closely linked to the will to value stocks of fish often very abundant during fall and spring pond fisheries and displaying a low market value. Based on the works performed on the yellow perch [32, 34, 36], several weaning protocols were tested using feeds or diverse raw materials (beef liver, frozen plankton, dried or hydrated formulated feeds) [45]. Because of (i) very high mortality rate (40–60% in 2 months) linked to food refusal, development of pathologies caused by *Aeromonas hydrophila* and cannibalism, (ii) high variability of qualities of the different batches of fishes received (juveniles or mature fishes, sizes, more or less lean fish, etc.), and (iii) difficulty of weaning protocols, this way of developing perciculture was rapidly stopped. Nevertheless, it was

and an established market niche and (2) the development of a new activity that did not harm other traditional activities of the sector (no competition). Initially, this project of diversification aimed at developing a complementary activity for pond fish farmers. Besides, linking to the survey realized [9], a possible competition with capture fisheries coming from Eastern and Central Europe as well as Scandinavia was highlighted; yet, surveyed persons stated that the capture levels were highly variable from one year to another, product quality (filleting yield) also strongly varied (effect of reproductive cycle), and supply period of market was stopped during the spawning season in spring. Consequently, all these facts confirmed the possibilities to develop an aquaculture of Eurasian perch targeting a regular production of fresh fillets

**Countries Production/exploited ecosystems Valorization**

Belgium Fisheries in rivers, polyculture in ponds Angling

Great Britain Fisheries in lakes and rivers Angling Hungary Fisheries in lakes and rivers Angling Ireland Lough Neagh Exportation

Baltic countries Fisheries in lakes Exportation

Poland Fisheries in inland waters (Swinoujscie region) Angling, exportation

Sweden Fisheries in the Baltic Sea Angling, exportation, human

**Table 2.** Interest for Eurasian perch according to European countries, survey realized in 1993 [9].

Switzerland Fisheries in lake Angling, strong human consumption

Norway Fisheries in inland waters of East, South, and North-East

Romania Fisheries in ponds, in the Danube River, Razelm Lake

Lake)

Serbia and Macedonia Fisheries in the Danube River and lakes (Dojran

Germany Fisheries (large lakes, rivers, Baltic Sea) Angling, exportation, weak human

Austria Fisheries (Constance Lake) Exportation, human consumption

Bulgaria Fisheries in rivers or in reservoirs Angling, human consumption

Luxemburg Fisheries in rivers Angling, weakly consumed

Netherlands Fisheries in IJsselmeer lakes and inland waters Angling, weak human consumption

Fisheries in the Danube River and other rivers Angling, human consumption

Finland Fisheries in Baltic Sea and inland waters Angling, strong human consumption France Fisheries in lakes and rivers Angling, strong human consumption

Denmark Fisheries in lakes or estuaries Angling, exportation

consumption

(East)

Angling, exportation, human

Angling, human consumption

Human consumption

consumption

consumption

with a constant and high quality.

Czech Republic and

140 Animal Domestication

Slovakia

maintained during few years to produce the biological material to realize growth trials and produce breeders [46]. This work allowed conducting a thinking on the choice of the rearing system, which was the most adapted to perciculture. If the production of juveniles could be realized in small ponds following extensive or semi-intensive methods [47], the on-growing phase was rapidly focused on rearing systems in controlled conditions, which allow higher production levels and a rationalization of rearing conditions to guarantee a reproducibility of performances and the development of the sector. Thus, on-growing trials were performed in floating cages (Lindre ponds, Lake of Féronval) and in recirculated aquaculture system (RAS) in Belgium and France. In this comparative approach of the possible potentialities by different rearing systems, it was demonstrated that similar specific growth rates were obtained in cages and RAS, but survival rates, feed conversion rates, and the homogeneity of individual weights were better in RAS [45, 48, 49]. It also appeared that perches farmed in cages had started a reproductive cycle: females and males captured in September (40–70 g) displayed gonadosomatic indexes of 2.4 and 7.1%, respectively, whereas they were constant and low in RAS (<0.5, sexual resting) [45, 48]. Yet, the development of gonads at such a low weight, lower than the market weight targeted (80–120 g), constituted a problem for maintaining optimal growth performances. These zootechnical trials also demonstrated that this species was very sensitive to pathogens, among which are parasites such as *Heteropolaria sp*., a protozoaire [50, 51], or bacteria, such as *Aeromonas sobria* [52]. This sensitivity of this species led to the shutdown of the project of the enterprise Perlac SA located in the Lake Neuchâtel in Switzerland. The sensitivity of this species to external parasites, such as *Dactylogyrus* or *Costias*, was confirmed during the first rearing trials performed by the society Lucas Perches created in 2001 in France [53]. At this period, this society used the water from a small river "La petite seille" to decrease the water temperature coming from a geothermal forage used by the society. At last, a strong individual growth heterogeneity was observed during trials [50]. All these experiences realized in Belgium, France, and Switzerland resulted in the choice of RAS as the most adapted rearing system for the development of perciculture [54, 55]. This choice was confirmed by technical choices operated by the first perch farms, Percitech in Switzerland (society created in 1994) and Lucas Perches in France (created in 2002) (**Figure 1**). Since then, researches exclusively focus on this rearing system using diets for trout or sea bass mainly.

**3.3. Control of the reproduction**

occurred (below the bar) over the period 1990–2018.

performances [70, 71].

Even though the market for the perch fillet remains seasonal in the traditional consumption market (March–October), the development of an intensive monoculture in RAS required a complete control of the reproductive cycle in order to obtain out-of-season spawning and not only rely on the single annual reproduction occurring in spring [41–43, 56]. A first research axis focused on the environmental control of the reproductive cycle. A preliminary test demonstrated the possibility of controlling the reproductive cycle by manipulating both water temperature and duration of photoperiod [57]. Thereafter, these researches allowed disentangling the respective roles of water temperature variations and duration of photophase by distinguishing the different phases of a reproductive cycle: induction, vitellogenesis, and final steps of the cycle [58–66]. All these works allowed developing a reliable protocol for the induction of out-of-season spawning close to 100% [67]. This program is now routinely applied in farm conditions; it allowed the realization of 2–12 reproductive cycles per year with different batches of breeders managed in delayed conditions. If the temperature variations and the duration of photoperiod drive the timing of the successive steps of the reproductive cycle (determining factors), other factors can modulate the quality of reproductive performances observed. For example, the feeding strategy is very important, and thus the nutritional needs of breeders were specified [68, 69]. In fact, numerous rearing factors, including environmental, nutritional, and populational, can act on breeders and influence their reproductive performances; multifactorial approaches must be used to optimize rearing conditions and secure

**Figure 1.** Timeline displaying the key phases of the domestication of Eurasian perch with from one hand the main knowledge acquired and the decisive decision taken (above the bar) and from the other hand the major events that

Domestication of the Eurasian Perch (*Perca fluviatilis*) http://dx.doi.org/10.5772/intechopen.85132 143

#### **3.2. Control of the life cycle of Eurasian perch for the development of perciculture in RAS**

Once the rearing system selected (intensive monoculture in RAS for the production of fillet for human consumption), diverse researches were performed in order to control the life cycle of the species in indoor conditions. They include the control of the reproductive cycle, the development of larval rearing protocols, the determination of nutritional needs, the optimization of growth performances, the control of quality of products, and first trials of genetic improvement. These researches were funded by both national (mainly in Belgium and France) and international, chiefly thanks to the European Union (FAIR-CT96-1572 1996-1998, FAIR-CT98-9241 1998-1999, Σ! 2321 ACRAPEP/ANVAR A0011134L 2001-2004, COOP-CT-2004-512629-PERCATECH 2004-2006) programs.

**Figure 1.** Timeline displaying the key phases of the domestication of Eurasian perch with from one hand the main knowledge acquired and the decisive decision taken (above the bar) and from the other hand the major events that occurred (below the bar) over the period 1990–2018.

#### **3.3. Control of the reproduction**

maintained during few years to produce the biological material to realize growth trials and produce breeders [46]. This work allowed conducting a thinking on the choice of the rearing system, which was the most adapted to perciculture. If the production of juveniles could be realized in small ponds following extensive or semi-intensive methods [47], the on-growing phase was rapidly focused on rearing systems in controlled conditions, which allow higher production levels and a rationalization of rearing conditions to guarantee a reproducibility of performances and the development of the sector. Thus, on-growing trials were performed in floating cages (Lindre ponds, Lake of Féronval) and in recirculated aquaculture system (RAS) in Belgium and France. In this comparative approach of the possible potentialities by different rearing systems, it was demonstrated that similar specific growth rates were obtained in cages and RAS, but survival rates, feed conversion rates, and the homogeneity of individual weights were better in RAS [45, 48, 49]. It also appeared that perches farmed in cages had started a reproductive cycle: females and males captured in September (40–70 g) displayed gonadosomatic indexes of 2.4 and 7.1%, respectively, whereas they were constant and low in RAS (<0.5, sexual resting) [45, 48]. Yet, the development of gonads at such a low weight, lower than the market weight targeted (80–120 g), constituted a problem for maintaining optimal growth performances. These zootechnical trials also demonstrated that this species was very sensitive to pathogens, among which are parasites such as *Heteropolaria sp*., a protozoaire [50, 51], or bacteria, such as *Aeromonas sobria* [52]. This sensitivity of this species led to the shutdown of the project of the enterprise Perlac SA located in the Lake Neuchâtel in Switzerland. The sensitivity of this species to external parasites, such as *Dactylogyrus* or *Costias*, was confirmed during the first rearing trials performed by the society Lucas Perches created in 2001 in France [53]. At this period, this society used the water from a small river "La petite seille" to decrease the water temperature coming from a geothermal forage used by the society. At last, a strong individual growth heterogeneity was observed during trials [50]. All these experiences realized in Belgium, France, and Switzerland resulted in the choice of RAS as the most adapted rearing system for the development of perciculture [54, 55]. This choice was confirmed by technical choices operated by the first perch farms, Percitech in Switzerland (society created in 1994) and Lucas Perches in France (created in 2002) (**Figure 1**). Since then, researches exclusively focus on this rearing system using diets

**3.2. Control of the life cycle of Eurasian perch for the development of perciculture** 

Once the rearing system selected (intensive monoculture in RAS for the production of fillet for human consumption), diverse researches were performed in order to control the life cycle of the species in indoor conditions. They include the control of the reproductive cycle, the development of larval rearing protocols, the determination of nutritional needs, the optimization of growth performances, the control of quality of products, and first trials of genetic improvement. These researches were funded by both national (mainly in Belgium and France) and international, chiefly thanks to the European Union (FAIR-CT96-1572 1996-1998, FAIR-CT98-9241 1998-1999, Σ! 2321 ACRAPEP/ANVAR A0011134L 2001-2004, COOP-CT-

for trout or sea bass mainly.

2004-512629-PERCATECH 2004-2006) programs.

**in RAS**

142 Animal Domestication

Even though the market for the perch fillet remains seasonal in the traditional consumption market (March–October), the development of an intensive monoculture in RAS required a complete control of the reproductive cycle in order to obtain out-of-season spawning and not only rely on the single annual reproduction occurring in spring [41–43, 56]. A first research axis focused on the environmental control of the reproductive cycle. A preliminary test demonstrated the possibility of controlling the reproductive cycle by manipulating both water temperature and duration of photoperiod [57]. Thereafter, these researches allowed disentangling the respective roles of water temperature variations and duration of photophase by distinguishing the different phases of a reproductive cycle: induction, vitellogenesis, and final steps of the cycle [58–66]. All these works allowed developing a reliable protocol for the induction of out-of-season spawning close to 100% [67]. This program is now routinely applied in farm conditions; it allowed the realization of 2–12 reproductive cycles per year with different batches of breeders managed in delayed conditions. If the temperature variations and the duration of photoperiod drive the timing of the successive steps of the reproductive cycle (determining factors), other factors can modulate the quality of reproductive performances observed. For example, the feeding strategy is very important, and thus the nutritional needs of breeders were specified [68, 69]. In fact, numerous rearing factors, including environmental, nutritional, and populational, can act on breeders and influence their reproductive performances; multifactorial approaches must be used to optimize rearing conditions and secure performances [70, 71].

Complementary to the control of reproductive cycle for the induction of out-of-season spawning, additional protocols based on hormonal injection were developed to synchronize spawning during the reproductive season [72–77]. They were based on previous works performed on the yellow perch [78–80]. The application of hormonal injections is now facilitated by the use of a classification method of oocyte stage maturation in preovulatory period [81]. At last, reliable protocols for collecting gametes (spermatozoa, oocytes) and artificial reproduction are also now available [82].

**3.5. On-growing, nutritional needs**

also obtained (>80%).

**3.6. Quality of products**

multifactorial [125, 126].

Once fry were available, trials on pre-on-growing and on-growing were realized in order to determine from one part the optimal conditions of growth and on the other part the potential of this species. It was first demonstrated that this species has a diurnal feeding activity [105]; the application of photoperiod with a long photophase stimulates growth and inhibits gonadal development [106]. First rearing trials had also demonstrated the gregarious behavior of this species (schooling behavior) and its ability to feed on pellets [46]. At this period, feeds for rainbow trout or sea bass were distributed to perch; feed conversion rates of 1.0–1.5 were registered according to the ration rate applied [49, 106–108]. High survival rates were

Domestication of the Eurasian Perch (*Perca fluviatilis*) http://dx.doi.org/10.5772/intechopen.85132 145

Once these favorable prerequisites were established (gregarious behavior, sufficient survival, acceptability of artificial feeds, correct alimentary conversion rate, etc.), more dedicated researches were realized on the effects of both major abiotic and biotic factors on growth. Thus, it was demonstrated that the optimal temperature for growth was 22–24°C [107]. Thereafter, complementary works allowed specifying the effects of the rearing environment (tank wall color, light intensity, manipulations) on the ingested feed and growth [109–110]. The effects of rearing conditions on the physiological state of fish were also studied; perch appeared as very sensitive to both poor conditions and manipulations [111, 112]. At the feeding level, ration table for maintenance and optimal and maximal growth according to physiological stages were determined [107, 108, 113, 114]. Then, nutritional needs were progressively determined to promote the emergence of a feed for percids once the volume of production would be large enough. Thus, the nutritional requirements in proteins, lipids, and some additives, such as oxidative as ethoxyquin, were specified [89, 115–118]. These studies allowed defining that a feed for perch should contain 43–50% of proteins, 13–18% of lipids, and 10–15% of glucids [119].

The domestication of species for the human consumption market requires knowing and controlling the quality of products (whole fish, fillet). Thus, very early, once the first zootechnical trials were completed, the chemical composition of the tissue of perch, and notably muscle, was analyzed [41, 120]. One major goal was the production of constant quality fillet to consumers, similar to the wild fillet coming from the lake. Researches were started from one part to understand the natural variability of organoleptic properties of the perch fillet according to the origin of captures and, on the other part, to identify the determinants of this quality. Importantly, the quality of a product is a vague and complex notion that depends on nutritional, technological, sensorial, and sanitary features. Thus, features of perch coming from different regions (Geneva Lake, Rhine estuary) were compared among themselves and to perch obtained from RAS [121, 122]. It was found that first the quality of products was highly variable according to the natural environment studied and second that farming factors (feeds, rearing densities, etc.) strongly impacted the properties of farmed perch [123, 124]. In fact, the control of the quality of products (flesh or whole fish), over the course of domestication, is

#### **3.4. Larval rearing**

Initially, trials of larval rearing were performed with spawning collected in various aquatic areas. Like for on-growing trials, several ways were initially prospected to promote the production of weaned juveniles: (1) an extensive production in small ponds with an *ex situ* weaning in tanks, (2) a semi-intensive production in mesocosms, and (3) an intensive production in RAS [83]. Even though few fish farms used the methods of mesocosms to produce the juveniles, particularly in Ireland, this is the intensive rearing in RAS that is mainly used nowadays. The first works aimed at optimizing the abiotic environment of farming (light intensity, duration of photophase, color of tank walls) and feeding protocols [84–87]. Initially, particular attention was paid to the use or not and the choice of live prey for larval rearing. The first protocols that have been developed used rotifers [88] or nauplii of *Artemia* spp. of various sizes [84, 87, 89–91]. The feeding transition (weaning = change from a feeding based on live prey to a commercial formulated diet) was soon questioned [92]. Very rapidly, major issues appeared: first, a high growth heterogeneity with a strong intra-cohort cannibalism rate [93–95] and second, the onset of developmental anomalies (malformations of skeleton and lordosis) with notably low inflation rate of the swim bladder [96–98].

The very strong impact of cannibalism within the first weeks of rearing was rapidly confirmed during the first commercial production [53]. Up to now, the strategy adopted by fish farmers to reduce cannibalism relies on frequent sorting (each week or 2 weeks) to maintain homogeneous batches during the nursery period and early weeks of on-growing. At that level, the results obtained by Mandiki et al. [99] suggested that they are natural populations less aggressive than others are, when they are placed in rearing conditions. Consequently it could be interesting to evaluate the intraspecific variability of wild populations (search for more docile populations). Concerning the problems of the inflation of the swim bladder and developmental anomalies often linked to the first point, they are mainly related to larval rearing conditions [100]. An improvement of rearing conditions associated with a high level of prophylaxis allowed increasing inflation rates and reduced malformation rates. In order to avoid the on-growing of individuals without swim bladder, protocols of sorting, based on practices realized in marine fish farming, were developed [101, 102]. Today, perch farms with well-conceived and seriously managed hatchery-nursery produce regular batches of 0.5 up to 1 million of weaned juveniles. However, developmental anomalies remain regularly observed in farms [103]. It is important to specify that the publication of a developmental table for the embryo-larvae corresponding to a normal development constitutes a major tool to identify the causes of common developmental anomalies) [104].

#### **3.5. On-growing, nutritional needs**

Complementary to the control of reproductive cycle for the induction of out-of-season spawning, additional protocols based on hormonal injection were developed to synchronize spawning during the reproductive season [72–77]. They were based on previous works performed on the yellow perch [78–80]. The application of hormonal injections is now facilitated by the use of a classification method of oocyte stage maturation in preovulatory period [81]. At last, reliable protocols for collecting gametes (spermatozoa, oocytes) and artificial reproduction

Initially, trials of larval rearing were performed with spawning collected in various aquatic areas. Like for on-growing trials, several ways were initially prospected to promote the production of weaned juveniles: (1) an extensive production in small ponds with an *ex situ* weaning in tanks, (2) a semi-intensive production in mesocosms, and (3) an intensive production in RAS [83]. Even though few fish farms used the methods of mesocosms to produce the juveniles, particularly in Ireland, this is the intensive rearing in RAS that is mainly used nowadays. The first works aimed at optimizing the abiotic environment of farming (light intensity, duration of photophase, color of tank walls) and feeding protocols [84–87]. Initially, particular attention was paid to the use or not and the choice of live prey for larval rearing. The first protocols that have been developed used rotifers [88] or nauplii of *Artemia* spp. of various sizes [84, 87, 89–91]. The feeding transition (weaning = change from a feeding based on live prey to a commercial formulated diet) was soon questioned [92]. Very rapidly, major issues appeared: first, a high growth heterogeneity with a strong intra-cohort cannibalism rate [93–95] and second, the onset of developmental anomalies (malformations of skeleton and lordosis) with notably

The very strong impact of cannibalism within the first weeks of rearing was rapidly confirmed during the first commercial production [53]. Up to now, the strategy adopted by fish farmers to reduce cannibalism relies on frequent sorting (each week or 2 weeks) to maintain homogeneous batches during the nursery period and early weeks of on-growing. At that level, the results obtained by Mandiki et al. [99] suggested that they are natural populations less aggressive than others are, when they are placed in rearing conditions. Consequently it could be interesting to evaluate the intraspecific variability of wild populations (search for more docile populations). Concerning the problems of the inflation of the swim bladder and developmental anomalies often linked to the first point, they are mainly related to larval rearing conditions [100]. An improvement of rearing conditions associated with a high level of prophylaxis allowed increasing inflation rates and reduced malformation rates. In order to avoid the on-growing of individuals without swim bladder, protocols of sorting, based on practices realized in marine fish farming, were developed [101, 102]. Today, perch farms with well-conceived and seriously managed hatchery-nursery produce regular batches of 0.5 up to 1 million of weaned juveniles. However, developmental anomalies remain regularly observed in farms [103]. It is important to specify that the publication of a developmental table for the embryo-larvae corresponding to a normal development constitutes a major tool to identify

are also now available [82].

low inflation rate of the swim bladder [96–98].

the causes of common developmental anomalies) [104].

**3.4. Larval rearing**

144 Animal Domestication

Once fry were available, trials on pre-on-growing and on-growing were realized in order to determine from one part the optimal conditions of growth and on the other part the potential of this species. It was first demonstrated that this species has a diurnal feeding activity [105]; the application of photoperiod with a long photophase stimulates growth and inhibits gonadal development [106]. First rearing trials had also demonstrated the gregarious behavior of this species (schooling behavior) and its ability to feed on pellets [46]. At this period, feeds for rainbow trout or sea bass were distributed to perch; feed conversion rates of 1.0–1.5 were registered according to the ration rate applied [49, 106–108]. High survival rates were also obtained (>80%).

Once these favorable prerequisites were established (gregarious behavior, sufficient survival, acceptability of artificial feeds, correct alimentary conversion rate, etc.), more dedicated researches were realized on the effects of both major abiotic and biotic factors on growth. Thus, it was demonstrated that the optimal temperature for growth was 22–24°C [107]. Thereafter, complementary works allowed specifying the effects of the rearing environment (tank wall color, light intensity, manipulations) on the ingested feed and growth [109–110]. The effects of rearing conditions on the physiological state of fish were also studied; perch appeared as very sensitive to both poor conditions and manipulations [111, 112]. At the feeding level, ration table for maintenance and optimal and maximal growth according to physiological stages were determined [107, 108, 113, 114]. Then, nutritional needs were progressively determined to promote the emergence of a feed for percids once the volume of production would be large enough. Thus, the nutritional requirements in proteins, lipids, and some additives, such as oxidative as ethoxyquin, were specified [89, 115–118]. These studies allowed defining that a feed for perch should contain 43–50% of proteins, 13–18% of lipids, and 10–15% of glucids [119].

#### **3.6. Quality of products**

The domestication of species for the human consumption market requires knowing and controlling the quality of products (whole fish, fillet). Thus, very early, once the first zootechnical trials were completed, the chemical composition of the tissue of perch, and notably muscle, was analyzed [41, 120]. One major goal was the production of constant quality fillet to consumers, similar to the wild fillet coming from the lake. Researches were started from one part to understand the natural variability of organoleptic properties of the perch fillet according to the origin of captures and, on the other part, to identify the determinants of this quality. Importantly, the quality of a product is a vague and complex notion that depends on nutritional, technological, sensorial, and sanitary features. Thus, features of perch coming from different regions (Geneva Lake, Rhine estuary) were compared among themselves and to perch obtained from RAS [121, 122]. It was found that first the quality of products was highly variable according to the natural environment studied and second that farming factors (feeds, rearing densities, etc.) strongly impacted the properties of farmed perch [123, 124]. In fact, the control of the quality of products (flesh or whole fish), over the course of domestication, is multifactorial [125, 126].

#### **3.7. Manipulation of sex and ploidy: genetic management of domesticated populations**

The Eurasian perch displays a sexual dimorphism of growth in favor of females [107, 108]; thus, the production of monosex female populations has rapidly appeared as a solution to reduce growth heterogeneity and increase growth performances. Hence, protocols (hormonal treatment with 17α-methyltestosterone) were developed for the production of homogametic males or neomales (XX) [127], with a sperm quality similar to heterogametic males [128]. Once produced and mature, those neomales were breeded with normal females (XX) allowing the production of 100% females, for which growth improvements were observed after 7 months of rearing in RAS at 23°C [129]. In a complementary study, trials of production of 100% female populations were also realized by gynogenesis using spermatozoa inactivated by UV radiation [130]. However, due to the low survival rates as well as insufficient growth performances, this method is rarely used [129].

farmers, designer of fish farms, traders in aquatic products, etc.). Progressively, knowledge was compiled in more and more comprehensive book [135, 136]. Obviously, this diffusion of knowledge and co-construction also occurred at local, regional, and national scales. In France, for instance, an informal group of exchanges, entitled "National group of pond carnivorous fish," often met in the beginning of the 1990s to discuss experience on various species (Wels, pikeperch, black-bass, and perch) that were the subject of diversification [137–140]. At the regional level, in Lorraine, the " Filière Lorraine d'Aquaculture Continentale (FLAC)" supports diverse zootechnical trials and, therefore, actively contributes to the emergence of perch farms on this territory. Later a similar initiative was taken in other regions from other coun-

Domestication of the Eurasian Perch (*Perca fluviatilis*) http://dx.doi.org/10.5772/intechopen.85132 147

The domestication of Eurasian perch was initially based on local issues (niche market, development of activities and jobs in rural environments). This domestication occurred in a few main steps: (1) socioeconomic analysis of the market, (2) first zootechnical trials and choice of the major rearing system (RAS), and (3) acquisition of in-depth knowledge on the successive stages of the production cycle (control of the reproductive cycle and reproduction, control of the larval rearing, on-growing, and quality of products) (**Figure 1**). It is important to highlight that the first two steps strongly considered the knowledge previously acquired on a close species, the yellow perch. Today, the Eurasian perch is considered at the level 4 of domestication, which means that the entire life cycle is closed in captivity without any wild inputs but no

Even though the first experimental trials were initiated at the beginning of the 1990s, the first perch farm (SARL Lucas Perches) created within the European Union was located in 2002 as a pilot enterprise. Importantly in Switzerland, a perch farm, Percitech, was created much earlier in 1994. About 20 years later, numerous projects were launched, some with very high expectations (e.g., FjordFresh Holding S/A in Estonia), in numerous European countries; 10 of these enterprises truly developed a commercial activity. Today, most perch farms pursue their activities; only few, mainly in Ireland (country where perch is not consumed), have stopped their activity. The investors that initially believed in this species were not issued from the aquaculture sector and discovered it. Sometimes, it corresponds to industrials that succeeded in other sectors and wants to diversify their activities. This initial distance from the aquaculture sector constitutes one of the reasons of the slow development of perciculture. Learning requires time. Without doubt, the domestication of Eurasian perch was and remained a particular human adventure, where the link between the species and humans is

In terms of perspective, one can expect that this young sector will pursue its development first based on current farms, whose economic viability remains to be demonstrated and second in link with the emergence of new projects and expansion of the market toward new consumers. This new development could imply the production of both pikeperch and perch within the same farms. To support this development, it is imperative to reduce production costs, high

tries, like in Ireland [141].

selective breeding programs is applied [142].

visible at different levels and various forms.

**5. Conclusion**

A second path, triploidization, was also studied in order to produce sterile animals. This path also appeared as very important because Eurasian perch is a species that can start a reproductive cycle before reaching market size. It is possible to capture in natural habitats (ponds) sexually mature females and males as such low weights as 10–20 g, even lower for males. As for other species reared in fish farming (salmonids), protocols based on thermal or pressure chocks were also developed to produce triploid perch [131].

With the development of perch farms (7–8 farms localized in Germany, France, Ireland, and Switzerland) and the increase of production in RAS (estimated between 500 and 800 tons per year), first thinking on the necessity to develop selective breeding programs emerged, mainly to improve growth performances and decrease production costs. Yet, up to now, no true selective breeding programs exist, even though basic genetic knowledge was acquired to develop them. Studies have notably allowed to characterize the genetic variability of wild perch, very often used as founding populations of current farmed stocks [132–133] and stocks of domesticated breeders currently present in perch farms [134]. These studies have demonstrated that the available stocks of domesticated perch in farms were (i) sufficiently genetically variable to allow developing selective genetic programs (lack of consanguinity) and (ii) often genetically distant from the origin populations (Alpine lakes) presumably assumed by fish farmers.
