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. Regrettably,

however

, the population of them currently declined due to poaching and overfishing for their 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 launched to carry out by artificial propagation through applying appropriate larval rearing techniques and supplying fingerlings. On the one side, feeding strategies are by far the most crucial stimuli, during

sturgeon

larviculture

. To establish an appropriate larval production strategy, manipulation of feeding patterns taking 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).

On the other hand

,

besides

the fact that

larvae

growth performance and survival are almost always under alteration by feeding procedures, knowledge in

sturgeon

aggressive nature can bring new regulations to

larviculture

technology.

Cannibalism

is considered a special form of killing and predation seems to be among

fish

larvae

,

in particular

.

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). To illustrate,

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

fish

length heterogeneity (Kestemont, Jourdan, Houbart, Mélard, Paspatis, Fontaine, Cuvier, Kentouri, &

Baras

, 2003; Ribeiro, Forsythe, & Qin, 2015; Leu et al., 2018).Having a certain effect on weight gain or even survivability by prey

frequency

are

cannibalism

nature 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 primarily impacts production and

then

rearing expenditure and costs of facilities. The possibility of feeding

frequency

and its effect on excessive aggression behaviour is monitored in some teleosts including 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

Change the capitalization

Sinensis

show examples

) (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 steady for facilitating harvesting or even feeding (Biswas, Thirunavukkarasu, Sundaray, & Kailasam, 2010; Chiu, Chu, Huang, Ho, Huang, & Yeh, 2020), though the effects of

size

sorting should be elucidated properly during

larviculture

. Regarding

larviculture

as a crucial phase, there is a necessity to round off knowledge in

sturgeon

larviculture

. The current study aimed to evaluate the effects of feeding/fasting strategy,

size

heterogeneity and stocking

density

on growth performance and survival of

Persian

sturgeon

larvae

as well as exploring the

cannibalism

rate

in

this

species

.