Diel feeding rhythms, daily ration and gastric evacuation rates of Sepia officinalis in the Ria Formosa Lagoon (south Portugal)
Abstract:In this paper, the diel feeding rhythms and the daily food consumption of the cuttlefish Sepia officinalis were examined from field data. Specimens (n = 1069) were collected over 24 h sampling operations in March, June, September and December 1995. Higher values for the weight fullness index (WFI: the ash-free dry weight of the stomach content divided by the wet body weight) occurred in March (0.083) and December (0.092). Higher numbers of empty stomachs occurred in June (24%) and September (28%), whereas in March and December empty stomachs represented only 14%. Feeding activity occurs essentially in twilight periods, but this pattern tends to disappear as water temperature rises. The daily ration varied between 5% and 9% body weight per day (BW d−1) according to Elliot and Persson's method, and between 2% and 5% BW d−1 with the Eggers method. The values of the evacuation rates ranged from 0.469 h−1 in June to 0.191 h−1 in December. Temperature has a major role, by conditioning the animal's energetic needs as well as determining a higher gastric evacuation rate. Sex, maturity stage, and food type seem to have an effect on the rate of feeding activity. Both females and mature individuals presented higher values for the WFI.
Document Type: Research Article
Publication date: September 1, 2002
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