Field estimation of daily ration of Norway lobster (Nephrops norvegicus) in the south of Portugal

Abstract

Daily ration estimates of Norway lobster (Nephrops norvegicus) from field samplings over a 24-h cycle were obtained. Four tows were conducted in the middle continental slope, off the south coast of Portugal. The results from Eggers (1977Eggers ( , 1979 and Elliot & Persson (1978) daily ration models were compared, by the Worobec 8-method (1984), showing no significant differences among them. The estimates of food consumption obtained varied from 1.098 to 1.170 g dry food per 100 g body wet weight in males and 1.642 to 1.755 g dry food per 100 g body wet weight in females. Our results were compared with daily rations reported for other crustaceans. Daily ration values were compared and tested by a two-way ANOVA, with interaction, showing significant differences between sexes. This has been registered for other decapods and may be explained by a period of active growth in females, on the onset of vitellogenesis, increasing their nutritional/ feeding needs.

A history of recent advancements on Nephrops norvegicus behavioral and physiological rhythms

“…The analysis of these feeding patterns did not report differences based on the sex or size of animals (Aguzzi et al 2007). Recently, similar conclusions were also obtained for a deeper water population of the middle slope (600 m) off Portugal (Cristo and Castro 2005).…”

“…Oakley 1979;Aguzzi et al 2004g;Cristo and Castro 2005). Although there are no quantified observations on the behavior of food collection during the emergence, but only the presumption that animals chiefly leave their burrows on a daily basis in order to forage (Oakley 1979), we proposed what follows.…”

Rhythms of feeding activity and food consumption of two Mediterranean burrowing fishes: Gnathophis mystax (Delaroche) and Chlopsis bicolor Rafinesque

“…2006). It must be pointed out that our values are computed from only one survey; the low number of collected specimens was not sufficient to estimate the food consumption for all the four periods studied, which need subsequent studies, as daily ration may vary greatly with season (Maynou & Cartes 1998; Cristo & Castro 2005; Carpentieri et al. 2006).…”

Habitat and Ecology of Nephrops norvegicus

“…Measuring scope for growth suffers from methodological constraints including accurately calculating metabolic rates and dealing with high individual variability. Again, in this case, more research is required to explore whether different rhythms in feeding and digestive activity perhaps cancel out habitat-specific foraging patterns (Cristo and Castro, 2005). Aguzzi et al, 2003), even if habitat-specific emergence patterns do not necessarily translate into differences in stomach fullness (Aguzzi et al, 2004).…”