Effects of size heterogeneity, feeding/fasting strategy and stocking density modulation on body performance and cannibalism rate of Persian sturgeon (Acipenser persicus) larvae

Persian

sturgeon

(

Acipenser

persicus) is one of the most valuable

species

in the southern parts of the Caspian Sea.

However

, regrettably, the population of

this

species

currently declined due to poaching and overfishing for its meat or caviar harvesting, environmental pollution and destruction of spawning grounds in the Caspian Sea. The Persian

sturgeon

has been considered an endangered

species

in IUCN Red List (IUCN, 2012) and

thus

for five decades, the conservation of Persian

sturgeon

is carried out by artificial propagation through applying appropriate larval rearing techniques to supply fingerlings. Feeding strategies are considered crucial stimuli, during

sturgeon

larviculture

. To establish an appropriate larval production strategy, manipulation of feeding patterns conceived by food restriction effects on green

sturgeon

(

Acipenser

medirostris) through pursuing fingerlings metabolic and homeostasis responses (Lin, Huang, Deng, Lee, Liang, & Hung, 2019), as well as the importance of initial feeding evaluation for growth and survivability in Siberian

sturgeon

(

Acipenser

baeri)

larvae

(Gisbert & Williot, 1997), and white

sturgeon

(

Acipenser

transmontanus) (Deng, Koshio, Yokoyama, Bai, Shao, Cui, & Hung, 2003). Thereby, the feeding strategy could be a noticeable factor over

larviculture

.

Although

fish

growth performance and survival are mostly discussed in

larviculture

technology, knowledge in

sturgeon

aggressive nature would be definitely required more attention.

Cannibalism

is considered a special form of killing and predation, particularly among

fish

larvae

.

This

aggressive behaviour leads to an excessive mortality rate in

larviculture

which is well-documented in teleosts (Manica, 2002;

Baras

, Kestemont, & Mélard, 2003; Puvanendran 2008; Manley, Rakocinski, Lee, & Blaylock, 2015; Leu, Tai, Meng, Tang, Wang, & Tew, 2018).

Cannibalism

can be definitely altered by a number of environmental and population factors (Naumowicz, Pajdak, Terech-Majewska, & Szarek, 2017) including feeding

frequency

or food availability (Manley et al., 2015),

fish

stocking

frequency

(Folkvord, 1991;

Baras

et al., 2003) or even length heterogeneity (Kestemont, Jourdan, Houbart, Mélard, Paspatis, Fontaine, Cuvier, Kentouri, &

Baras

, 2003; Ribeiro, Forsythe, & Qin, 2015; Leu et al., 2018). These literally cause either prey

frequency

or production weight gain consequences (Hecht & Pienaar, 1993; Kestemont et al., 2003;

Baras

et al., 2003). Control of the outlined factors is rooted in knowing

larviculture

based on

species

that have direct impacts on production, rearing expenditure and costs of facilities.

Furthermore

, the possibility of feeding

frequency

and its effect on excessive aggression behaviour of teleosts is proved in African catfish Clarias gariepinus

larvae

(Kaiser, Weyl, & Hecht, 1995) and yellowtail flounder Limanda ferruginea (Dwyer, Brown, Parrish, & Lall, 2002). In some

species

such

as juvenile Asian seabass Lates calcarifer (Ribeiro et al., 2015), Eurasian perch Perca fluviatilis (Król & Zieliński, 2015) and wild Atlantic bluefin tuna Thunnus thynnus

larvae

(Uriarte, Johnstone, Laiz-Carrión, García, Llopiz, Shiroza, Quintanilla, Lozano-Peral, Reglero, & Alemany, 2019)

cannibalism

rate was fluctuated by

fish

density. Moderation of

cannibalism

rate may be

also

controlled by optimizing the stocking density. Stocking density

also

regarded as a negative variable for juvenile Chinese

sturgeon

(

Acipenser

Sinensis) (Long, Zhang, Ni, Liu, Wu, & Wang, 2019) and Amur

sturgeon

(

Acipenser

schrenckii) (Ni, Wen, Li, Chi, Bu, Ren, Zhang, Song, & Ding, 2014) performance, resistance and survivability. The effect of size differentiation is another contributing option confirmed in the aggressive behaviour of Asian seabass fry (Ribeiro & Qin, 2013), Eurasian perch and pikeperch Sander lucioperca (Król et al., 2013). In many cases, the main target of aquaculture is keeping size heterogeneity for facilitating harvesting or even feeding (Biswas, Thirunavukkarasu, Sundaray, & Kailasam, 2010; Chiu, Chu, Huang, Ho, Huang, & Yeh, 2020),

however

Add the comma(s)

,however

show examples

the effects of size sorting should be elucidated properly during

larviculture

.