Sibling cannibalism among juvenile vundu under controlled conditions. II. Effect of body weight and environmental variables on the periodicity and intensity of type II cannibalism

Abstract

Cannibalism among starved groups of juvenile (19-48 days old) vundu catfish Heterobranchus longifilis was 66·5% nocturnal, and its impact under modified day length was proportional to the duration of the dark phase. Shallow depth and high population density decreased the intensity of cannibalism, whereas low density and deeper environments had an opposite effect. The presence of refuges had no significant effect on cannibalism. The maintenance (R maint ) and maximum (R max ) daily food rations (% day 1 ) of cannibals feeding on live prey were modelled as R maint =3·899 W C 0·327 (r 2 =0·684; d.f.=31), and R max =49.545 W C 0·321 (r 2 =0·999; d.f.=5), where W C was the body weight of the cannibal (g). The latter model indicated that the impact of a cannibal on a population decreased by a 20% margin each time the cannibal doubled its body weight, and suggested that cannibalism among vundu would become insignificant for cannibals heavier than 30 g. The significance of these findings is discussed within the contexts of vundu aquaculture and of general, conceptual models of the dynamics of cannibalism among fishes. 1999 The Fisheries Society of the British Isles

Desenvolvimento do Surubim do Iguaçu (Steindachneridion sp., Garavello (1991)) (Siluroidei:Pimelodiae) em ambiente escuro durante a fase inicial, alimentado com diferentes dietas

“…Britz e Pienaar (1992) verificaram que para Clarias gariepinus cultivados sob luz intensa, os indivíduos se movimentam para o fundo dos tanques e a competição e a agressividade aumentam. Baras et al (1999) relatam que a criação de pimelodídeos em escuridão permanente resulta em crescimento mais rápido e menos heterogêneo, especialmente quando a alimentação é fornecida continuamente.…”

“…O canibalismo ocorreu em todos os tratamentos, mas diferindo estatisticamente para o tratamento R, e estes resultados mostram que a predação intraespecífica é um fenômeno freqüente nas fases iniciais do desenvolvimento dos peixes, o que é relatado por Baras e Jobling (2002), e ocorre também em ambientes não iluminados, pois de acordo com Baras et al (1999) e Lamb (2001, como os pimelodídeos se orientam pelo tato e por quimiosensores, localizados nos barbilhões, não necessitam de luz para a predação.…”

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

“…Considering that temperature and provision of food are set for maximising growth in aquaculture environments, light-related factors (day length, light intensity, turbidity) and stocking density are amongst the only factors that can be tailored by aquaculturists. The influence of stocking density on cannibalism in fish has been highlighted on many occasions (Li and Mathias, 1982;Degani and Levanon, 1983;Giles et al, 1986;Hecht and Appelbaum, 1988;van Damme et al, 1989;Haylor, 1991;Kaiser et al, 1995;Mélard et al, 1996a;Kucharczyk et al, 1998;Baras et al, 1999). Little is known however whether stocking density affects the emergence of cannibalism, the number of cannibals in the population and/or the dynamics of cannibalism (Kucharczyk et al, 1998).…”

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

“…In every experiment, prey density was in large excess and cannibals were isolated from each other to avoid any possible effect of competition or dominance hierarchies on the variables under scrutiny (MacLean et al 2003). The species under study was the vundu catfish Heterobranchus longifilis, a fast growing African clariid catfish of interest for the diversification of freshwater aquaculture (Legendre et al 1992;Hecht et al 1996;Otémé et al 1996), but which requires frequent size grading under culture conditions (Gilles et al 2001), because of intense cannibalism during its larval and juvenile stages (Baras 1999;Baras et al 1999;Nwosu and Holzlöhner 2000;Atse et al 2009). …”