Why is cannibalism less frequent when larvae of sutchi catfishPangasianodon hypophthalmusare reared under dim light?

Abstract

Survival rates of the larvae of sutchi catfish Pangasianodon hypophthalmus are reported to be three times higher under dim conditions (0.1 lx) than those under 100 lx. In this study, larval behaviour of sutchi catfish was examined under various light intensities (<0.01, 0.1, 1, 10 and 100 lx) using a CCD camera to understand why survival rates vary under different light intensities. Five-day-old larvae showed significantly higher swimming activity under <0.01, 0.1 and 1 lx than those under 10 and 100 lx. On the other hand, the larvae showed significantly higher aggressive behaviour under 10 and 100 lx; swimming larvae attacked resting individuals more frequently under 10 and 100 lx than those under 0 and 0.1 lx. Aggressive behaviour was considered to induce lesions, inflicted by the sharp teeth of attacking larvae, on larval skin surfaces. It is considered that the chemical substances would generate from injured skin surfaces then acted as stimuli, causing the cannibalistic behaviour in other fish around the injured fish. This study provided evidence that the observed higher survival rates depended on lower frequency of aggressive behaviour under dark or dim conditions. It is therefore recommended that larval rearing of sutchi catfish be conducted under dim (less than 1 lx) conditions.

Light intensity affects the survival and growth of matrinxã larvae, Brycon amazonicus (Spix & Agassiz, 1829)

“…Smaller swimming activity reduces the likelihood of encounters between animals and, therefore, social interactions among group members (Souza et al, ). Thus, in low light conditions, there is a reduction in aggressive behaviour and increased survival as observed in Pangasianodon hypophthalmus (Mukai et al, ) and Sander lucioperca larvae (Tielmann, Schulz, & Meyer, ).…”

“…The luminosity, for example, is an essential environmental condition for the survival of fish (Rick & Bakker, ). Some studies suggest that the manipulation of light intensity can regulate biological rhythms and modulate various physiological functions in different species of fish, and it may reflect on survival (Mukai, Nai, & Lim, ; Navarro, Navarro, Murgas, & Felizardo, ), growth (Biswas, Morita, Yoshizaki, Maita, & Takeuchi, ; Falcón, Migaud, Muñoz‐Cueto, & Carrillo, ; Imsland et al, ; Rad, Bozaoglu, Gözükara, Karahan, & Kurt, ), food intake (Kitagawa et al, ; Puvanendran & Brown, ), metabolic rate (Porter, Duncan, Handeland, Stefansson, & Bromage, ), locomotor activity (Navarro et al, ; Trippel & Neil, ), body pigmentation, sexual maturation, reproduction (Fujii, Sugimoto, & Oshima, ; Song et al, ), melatonin (Ekström & Meissl, ; Falcón et al, ) and aggressive behaviour (Carvalho, Ha, & Gonçalves‐de‐Freitas, ; Carvalho, Mendonça, Costa‐Ferreira, & Gonçalves‐de‐Freitas, ; Lopes et al, ; Sarmento, Almeida, Marcon, & Carvalho, ).…”

Development, nutrition, and rearing practices of relevant catfish species (Siluriformes) at early stages

“…In this context, Mukai 216 found that P. hypophthalmus larvae showed higher survival and growth rates when reared under 0.1 lx (1.40 × 10 −3 μmol m −2 s −1 ) of white fluorescent light compared with those reared under other light intensities (1, 10, and 100 lx). Moreover, Mukai et al 217 demonstrated that P. hypophthalmus larvae showed more aggressive behaviour at higher light intensities (10 and 100 lx) than those under low light intensity (0 and 0.1 lx); these results corroborate those reported for C. gariepinus 213 . Furthermore, when C. gariepinus larvae were reared under normal photoperiod (600–1000 lx during light hours) or continuous dark (<0.01 lx) conditions from hatching up to 20 dph, no differences in larval size were found, even though larvae reared under dark conditions had higher survival rates than those under normal photoperiod 89 .…”

Visual pigments and spectral sensitivity of juvenile sutchi catfish (Pangasianodon hypophthalmusSauvage 1878)

“…In previous studies, under white fluorescent light, sutchi catfish larvae were reported to exhibit significantly higher survival rate and lower cannibalism under dim light conditions than bright light conditions (Mukai, Tan, & Lim, ; Mukai, ). Moreover, under red light with a light intensity of 1.40 × 10 −3 µmol m −2 s −1 , sutchi catfish larvae showed a tendency to have higher survival and growth rates (Tan, Yusoff, Ismail, Sallehudin, & Mukai, ), while sutchi catfish juveniles showed a tendency to have higher growth rates and production index (Tan, ).…”

“…Therefore, taking into account the reported species‐specific visual spectral sensitivity among fish and the dearth of studies on the sensitivity of sutchi catfish towards light conditions (Mukai et al, ; Mukai, ; Tan, ; Tan et al, ; Yusoff, Sallehudin, Tan, Mohammad‐Noor, & Mukai, ), this study aimed to understand the visual spectral sensitivity of juvenile sutchi catfish through the peak differences in spectral absorbance of wholemounts of retinae by spectrophotometric analyses.…”