Growth, gonadal development and spawning time of Atlantic cod (Gadus morhua) reared under different photoperiods

Energy dilution with α-cellulose in diets for Atlantic cod (Gadus morhua L.) juveniles — Effects on growth, feed intake, liver size and digestibility of nutrients

“…Growth Growth can be affected by environmental factors like water temperature (Howell, 1984), light , fish size (Braaten, 1984;Jobling, 1992), sexual maturation (Braaten, 1984;Hansen et al, 2001;Hemre et al, 2002), health, nutrition (Morais et al, 2001;Rosenlund et al, 2004) and heritage (Gjerde et al, 2004). Specific growth rate (SGR) was higher in the first 7 weeks (1.00 ±0.09) than in the last 7 weeks (0.76 ±0.08), which was expected, since smaller cod have higher feed intake per weight unit than larger cod (Braaten, 1984).…”

Effect of Photoperiod Advancement of Atlantic Cod Spawning on Egg Size and Biochemistry

“…Atlantic cod respond to PP compression by reducing the number of oocytes that mature (Hansen et al 2001) rather than skipping spawning altogether as occurs in striped bass Morone saxatilis (Blythe et al 1994) and Atlantic halibut (Bjö rnsson et al 1998). In the broodstock populations studied in the present work, the PP advanced group initiated spawning approximately 4 months before the ambient controls but had a longer spawning season, had lower mean daily egg batch volumes, and produced a lower total volume of eggs over the entire spawning season (Penney et al 2006a).…”

“…Conversely, onset of spawning may be delayed beyond the normal spawning time by lengthening the PP cycle (delayed PP broodstock). Photoperiod manipulations to alternatively compress or delay spawning cycles have been used with various degrees of success in many marine species, including Atlantic salmon Salmo salar (Taranger et al 1998), rainbow trout Oncorhynchus mykiss (Bromage et al 1984), Atlantic halibut Hippoglossus hippoglossus , turbot Scophthalmus maximus (Devauchelle et al 1988), common soles Solea solea (Devauchelle et al 1987), European seabass Dicentrarchus labrax (Carrillo et al 1989), and Atlantic cod Gadus morhua (Hansen et al 2001;Norberg et al 2004). The resulting PP-manipulated broodstocks allow egg production for much longer periods throughout the year, which facilitates optimum utilization of hatchery space along with reduced production costs.…”

“…Studies to determine the effect of PP manipulation on egg quality have yielded equivocal results (Brooks et al 1997). However, it is known that PP manipulation can reduce the size of Atlantic cod eggs (Hansen et al 2001;Penney et al 2006a), although evidence of correlation between egg size and survival or hatching success in Atlantic cod under laboratory or hatchery conditions has been either conflicting (Zhao et al 2001) or lacking altogether (Ouellet et al 2001;Penney et al 2006b). In some stocks at least, hatching success is significantly related to levels of specific fatty acids (docosahexaenoic acid [DHA], eicosapentaenoic acid [EPA], and arachidonic acid [AA]) and their ratios (Pickova et al 1997), although evidence of such relationships is contradictory (Penney at al.…”

Validation of Endogenous Reference Genes for qPCR Quantification of Muscle Transcripts in Atlantic Cod Subjected to Different Photoperiod Regimes

“…Photoperiod manipulation, typified by continuous light illumination, has been used to delay sexual maturation to some extent in several aquaculture species, including Atlantic salmon (Salmo salar, L.) (Endal et al, 2000), European sea bass (Dicentrachus labrax, L.) (Begtashi et al, 2004) and Atlantic cod (Davie et al, 2003;Hansen et al, 2001;Norberg et al, 2004). The application of continuous light from the summer solstice prior to maturation is thought to mask the photoperiod signal that acts as a trigger for gonadal development and spawning (Davie et al, 2003).…”