How many meals a day to minimize cannibalism when rearing larvae of the Amazonian catfishPseudoplatystoma punctifer? The cannibal’s point of view

Abstract

-Meal frequency is a key parameter in fish larviculture, especially in highly cannibalistic species. Knowledge of the biological bases of cannibalism (growth capacity of cannibals, morphological constraints on cannibalism, prey size preference) can help predicting the risks of cannibalism for different feeding schedules under culture conditions. This study relied on the day-by-day analysis of prey size preference and bioenergetics of individual cannibals of the catfish Pseudoplatystoma punctifer (8-65 mm standard length, SL, 0.5-400 mg dry mass, DM) at 28.5• C under 12L:12D. The results were equated with the ontogenetic variations of morphological factors (head and mouth width) and feed efficiency of larvae feeding on Artemia nauplii, in order to calculate the risks of cannibalism among fish fed 2-7 daily meals. The predation capacities of P. punctifer were highest at 8 mm SL and decreased in larger fish (largest prey = 86% and 70% SL in fish of 8 and >30 mm SL, respectively). Cannibals of increasing size preferred increasingly smaller prey relative to their own size, but also to their predation capacities. These morphological and behavioural constraints were largely compensated for by bioenergetics performance. Cannibals consumed high daily food rations (as high as 171 and 29% DM in fish <1 and >300 mg DM, respectively), exhibited high gross conversion efficiencies (0.50-0.55 and about 0.70, in fish <1 and >30 mg DM, respectively), and grew rapidly (90 and 18% DM day −1 in fish <1 and >300 mg DM, respectively). The growth advantage of cannibals over siblings fed Artemia nauplii was decisive, except for high meal frequencies (6-7 daily meals). This study supports the view that the risk of cannibalism and adequate feeding strategies can be largely predicted in a particular fish species if the morphological, behavioural and bioenergetics bases of cannibalism are examined altogether in an ontogenetic perspective.

Histological development of the digestive system of the Amazonian pimelodid catfish Pseudoplatystoma punctifer

“…P. punctifer (Teleostei: Siluriformes, Pimelodidae) is an appreciated catfish species, because of the flavour and texture of its flesh, and the absence of intramuscular spines. Several studies have been performed to develop the culture of this species (Nuñez et al, 2008 and2011;Baras et al, 2011 and2012). One of the limiting factors of fish culture development in this area is the lack of sustained fingerling production to support this economical activity.…”

“…However, survival rates in these systems are generally low and quite unpredictable (Gomes et al, 2000;Mai and Zaniboni Filho, 2005, among others), as they are highly impacted by food availability and the presence of predators. In P. punctifer, the difficulty of larvae to accept inert diets at weaning and a strong cannibalistic behaviour hampers the aquaculture of this fast-growing Amazonian catfish species, even in recirculation systems (Baras et al, 2011;Nuñez et al, 2011). One of the first steps in order to enhance the success of P. punctifer larval rearing and facilitate the overcoming of the major bottleneck of its culture, is the description of the ontogeny of the digestive system in order to synchronize the larval stage of development and maturation of their digestive organs with the feeding protocol and rearing practices, as well as identifying limiting factors during larval rearing.…”

“…Larvae were reared in triplicate (initial density = 90 larvae/l) under 0L : 24D photoperiod, fed six times a day from 4 to 17 dpf with non-enriched Artemia spp. nauplii in slight excess (0.4 to 17 nauplii/ml) considering the larval density, the weight increase of the larvae and the daily food ration (Baras et al, 2011) and weaned onto a Gisbert, Moreira, Castro-Ruiz, Öztürk, Fernández, Gilles, Nuñez, Duponchelle, Tello, Renno, García-Dávila and Darias 1766 commercial inert diet (BioMar ® , Nersac, France; proximate composition: 58% proteins, 15% lipids, 11% ash; particle size: 0.5 mm) within 4 days. Once weaned (22 dpf, 23.7 mm TL), larvae were fed five times a day at 5% of the larval wet weight, changing at 33 dpf (29.9 mm TL) to another commercial diet (Aquaxcel ® , Cargill Animal Nutrition, Franklinton, LA, USA; proximate composition: 45% proteins, 12% lipids, 10% ash; particle size: 0.8 mm) until the end of the trial (41 dpf, 58.1 mm TL) (Figure 1).…”

Do cannibalistic fish forage optimally? An experimental study of prey size preference, bioenergetics of cannibalism and their ontogenetic variations in the African catfishHeterobranchus longifilis

“…However, cannibals generally prefer small over large conspecifics (Atlantic cod Gadus morhua, Folkvord and Otterå 1993; walleye pollock Theragra chalcogramma, Sogard and Olla 1994; Arctic charr Salvelinus alpinus, Amundsen et al 1995;snakehead Channa striata, Qin and Fast 1996;dorada Brycon moorei, Baras et al 2000). Evidence has also been provided that cannibals of increasing size tend to select prey that are increasingly smaller relative to their predation capacities (Asian catfish Pangasius djambal, ; Amazonian catfish Pseudoplatystoma punctifer, Baras et al 2011). The bioenergetics of cannibalism has been investigated in several fish species, but the effects of prey size on the growth and food conversion of cannibals have been overlooked.…”

Frequência alimentar e taxa de arraçoamento durante o condicionamento alimentar de juvenis de pacamã

“…A frequência alimentar adequada é fundamental para o bom desempenho de peixes (Silverstein et al, 2001), principalmente na fase inicial do cultivo de espécies carnívoras, pois pode melhorar a uniformidade do lote e reduzir o canibalismo (Baras et al, 2011).…”