Browsing by Author "Van der Lingen, C. D."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- Diet and feeding intensity of sardine Sardina pilchardus: correlation with satellite-derived chlorophyll dataPublication . Garrido, Susana; Ben-Hamadou, Radhouan; Oliveira, P. B.; Cunha, M. E.; Chicharo, Maria Alexandra; Van der Lingen, C. D.Spatio-temporal variability of the diet of sardine Sardina pilchardus off Portugal was examined through analysis of the stomach contents of fish collected every 14 d from the west and south of Portugal during 2003/2004. Dietary composition of the modal sardine length class was assessed by determining the frequency of occurrence and carbon content of identified prey, and these 2 parameters were combined to estimate a modified index of relative importance of prey (mIRI). The most important prey for sardines were zooplankton, comprising crustacean eggs, copepods, decapods, cirripedes and fish eggs, dinoflagellates and diatoms (particularly the toxin-producer genus Pseudo-nitzschia), which together accounted for >90% of the estimated dietary carbon. Dietary seasonality was similar for both areas, except that the contribution of phytoplankton was higher for fish from the west Portuguese coast, where upwelling events are stronger and recurrent during spring and summer months. The predominance of prey <750 μm in sardine diet suggests that filter feeding is the dominant feeding mode used in the wild. Feeding intensity was similar for both sexes and for fish of different length classes and was higher on the west coast than in the south, which is probably related to the higher productivity of the west coast. Although there was high inter-annual variability in feeding intensity, this parameter was highest for both areas during spring and winter months. Temporal variability in satellite-derived chlorophyll a matched the temporal variability in the dietary contribution by phytoplankton and of sardine feeding intensity, suggesting further investigation of the potential use of satellite-derived chlorophyll a data as a proxy for sardine feeding intensity.
- Effect of maternal fat reserves on the fatty acid composition of sardine (Sardina pilchardus) oocytesPublication . Garrido, Susana; Rosa, R.; Ben-Hamadou, Radhouan; Cunha, M. E.; Chicharo, Alexandra; Van der Lingen, C. D.We compared the fatty acid (FA) composition of the muscle and gonads of female Iberian sardines with hydrated oocytes collected during the 2002/03 spawning season off southern Portugal (November and February) and off western Portugal (February). Sardine condition and total FA concentration in the muscle decreased between the two sampling dates, while the gonadosomatic index was similar between samples. Total monounsaturated FA concentrations in sardine gonads were different for the three samples while saturated and polyunsaturated FA concentrations were similar. Significant linear relations were found between FA concentrations in female muscle and oocytes, including eicosapentaenoic acid (EPA; 20:5n−3) and arachidonic acid (AA; 20:4n−6), both being essential for normal larval development. The concentration of docosahexaenoic acid (DHA; 22:6n−3) in oocytes was independent on muscle concentration, probably resulting from its selective transfer to the oocytes. The EPA/ DHA ratio was highly conserved in sardine tissues, while DHA/AA and EPA/AA ratios varied significantly between samples. These results indicate that the FA content of eggs produced by sardines varies throughout the spawning season, egg FA concentrations decreasing as females lose condition, and FA composition also shows spatial variability. Both types of variability may have a significant impact on egg quality, particularly on the amount of reserves available to larvae affecting their resistance to starvation, and the appropriate FA composition required for normal growth.
- Spatio-temporal variability in fatty acid trophic biomarkers in stomach contents and muscle of Iberian sardine (Sardina pilchardus) and its relationship with spawningPublication . Garrido, Susana; Rosa, R.; Ben-Hamadou, Radhouan; Cunha, M. E.; Teodosio, Maria; Van der Lingen, C. D.Temporal variation in the fatty acid (FA) composition of stomach contents of Iberian sardines was compared to the relative contribution to dietary carbon made by different prey types for Wsh from two areas of Portugal. The effect of the FA content of the diet on sardine muscle FA composition was also studied, aiming at (1)analysing if FA biomarkers can be used as a complementary technique for the study of sardine diet and (2) to relate spatial and temporal variations of prey FA content with sardine condition and reproduction. Significant spatial differences in the FA composition of sardine diet occurred with concentrations of n-3 polyunsaturated FA, namely eicosapentaenoic acid [EPA, 20:5n-3] and linolenic acid 18:3n-3, being signifcantly higher in the diet of sardines from the west coast, whilst the diet of sardines from the south coast was richer in monounsaturated fatty acids (MUFA), namely the carnivory biomarker oleic acid 18:1n-9. These results are in agreement with the higher contribution made by diatoms and dinoflagellates to the diet of sardines of the west coast. Spatial variation in sardine dietary FA was also detected in their muscle composition, specifically for EPA, and the eicosapentaenoic/docosahexaenoic acid and (n-3)/(n-6) ratios, which were higher in sardines from the west coast. No difference in FA composition was detected between sexes, and the seasonal variability in sardine total FA concentration was primarily related to the seasonality of spawning. Sardines accumulate high concentrations of FAs during the resting stage of reproduction when the feeding intensity is similar or lower to that observed during the spawning season. Additionally, sardines show a high selective retention of MUFA and polyunsaturated FA (PUFA) throughout the year except at the beginning of the spawning season, when these FAs are largely invested in the formation of the gonads. Therefore, temporal and regional diVerences of prey environments are strong enough to be reflected in fish body composition, namely on the accumulation of essential FAs, which can have a strong impact on reproduction success for this species.