Effect of stocking density on the dynamics of cannibalism in sibling larvae of Perca fluviatilis under controlled conditions

Abstract

The effect of stocking density (10, 31.6 and 100 larvae l À 1 ; three replicates per treatment) on the day-by-day dynamics of survival, growth and cannibalism was examined in sibling perch larvae reared from eyed-egg stage in 100-l cages (16L:8D, 20.0 F 0.5 jC, O 2 z 6.0 mg l À 1 ; feeding in excess with live Artemia nauplii during the photophase) during the first 3 weeks of exogenous feeding. Larvae unable to achieve the transition to exogenous feeding died in between 7 and 11 days post-hatch. Later, mortality from causes other than cannibalism never exceeded 1% day À 1 . Cannibalism did not start before days 10 -11 and first consisted in the incomplete ingestion of prey attacked tail first, exclusively. This type of cannibalism never caused losses higher than 2.0% of the initial stock, and ceased after days 16 -18. From days 12 -14 onwards, differential growth was apparent, and cannibals turned to complete cannibalism of small prey ingested head first, which caused greater losses (28 -53% of the stock). Increasing the stocking density did not compromise growth and decreased the overall impact of cannibalism through several complementary mechanisms: (i) a postponed emergence of cannibalism, (ii) a lower proportion of cannibals in the population, and (iii) probably a lower rate of cannibalism per capita as predation was complicated and less directed at high stocking density. D

Culture Methods of Eurasian Perch and Yellow Perch Early Life Stages

“…As size heterogeneity develops, cannibals switch to complete (type II) cannibalism, capture the prey head first and swallow them completely. According to Baras et al (2003), type I cannibalism (which has a relatively low impact on overall survival) is exerted by Eurasian perch from day 11 onwards, and ceases around day 16-18 post-hatching, while the appearance of type II cannibalism (inducing up to 50 % of total mortality) is determined by gape-size limitations and occurs from days 12 to 14 post-hatching. Type II cannibalism can be mitigated by size-sorting or other methods of limiting size heterogeneity.…”

“…The effects of stocking density on rearing performance differed between perch larvae and post-larvae. At the larval stage, the slowest growth and higher rates of Table 9.3 Population, environment and feeding variables significantly affecting the final size variation, growth a , survival and/or cannibalism in Eurasian perch larvae and post-larvae reared in tanks (Data compiled from Baras et al 2003 Standard size heterogeneity = sibling fish reared in the same tank from hatching under standard conditions, high = sibling fish initially reared at two different stocking densities to create size differences, then mixed altogether; controlled = sibling fish with regular size-sorting (i.e. removal of both large and small individuals) cannibalism were observed at low stocking density and can be attributed to several factors, such as the development of dominance hierarchies, growth depensation and territoriality.…”

“…removal of both large and small individuals) cannibalism were observed at low stocking density and can be attributed to several factors, such as the development of dominance hierarchies, growth depensation and territoriality. Baras et al (2003) described a shoaling behavior of larvae held at intermediate and high stocking density while fish reared at low density were dispersed. At high stocking density the number of available territories is proportionally limited, as is the number of cannibals, explaining why the cannibalism was less intense at the highest density.…”

Dynamics of yolk sac and oil droplet utilization and behavioural aspects of swim bladder inflation in burbot, Lota lota L., larvae during the first days of life, under laboratory conditions

“…Too early supply of food when not all larvae are able to take exogenous food can lead to size differentiation, which in the case of predatory fish (as for example the burbot) can result in intensified cannibalism (e.g. Baras et al 2003). On the other hand, a late supply of food can bring about irreversible changes in the alimentary system, as a result of exceeding the so-called point of no return (PNR), after which larvae are not able to digest ingested food (e.g.…”

“…Therefore, the knowledge of the biology of the first days of the burbot larvae life may be crucial for effective intensive larviculture of the species. Especially, ineffective procedures applied in the first days of life may affect growth differentiation and in consequence may lead to increased level of cannibalism, which is very problematic in the case of burbot (Jensen et al 2011;Trabelsi et al 2011) similar to other predators (Baras et al 2003). The published data include a series of studies related to rearing larvae of this species under controlled conditions.…”