Browsing by Subject "15490"
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Diet composition and feeding periodicity of the seahorse Hippocampus barbouri reared in illuminated sea cages -
Aquaculture, 2012 - ElsevierThe zooplankton prey composition and feeding periodicity of juvenile and adult seahorses Hippocampus barbouri reared in illuminated and non-illuminated sea cages were compared. Mean frequency of occurrence (%FO), prey composition (%N), and gut fullness of seahorses were calculated from analyses of gut contents. Compared with juvenile seahorses, adults consumed more variety of prey consisting of copepods, larvae of decapods, polychaetes and fish, and euphausid shrimps. Calanoid copedods were found in the gut of more juvenile (%FO = 47) and adult (%FO = 64) seahorses in illuminated cages but harpacticoid copepods were ingested by more juvenile fish (%FO = 50) in non-illuminated cages. Decapod larvae (%N = 66) in illuminated cages dominated the diet of juvenile seahorses, whereas in non-illuminated cages harpacticoid copepods (%N = 59) did. Calanoid copepods and decapod larvae (%N = 91–97) comprised the bulk of ingested prey among adult seahorses in all experimental cages. The gut of caged seahorses was generally full during daytime but declined in the evening, becoming almost empty at midnight, particularly among juveniles. Cage illumination commencing at midnight increased the number of filled guts at dawn (0400 h) among juvenile and adult seahorses. Unlike adult seahorses over a 24-h period, the overall incidence of filled guts among juveniles was not different between those in non-illuminated and illuminated cages. These results provide an alternative to growing caged H. barbouri on cultured live food, particularly copepods attracted by night illumination.
Zooplankton distribution during winter using Two-Way Indicator Species Analysis (TWINSPAN) and Canonical Correspondence Analysis (CANOCO). Spatial distribution and community structure of zooplankton species and its relationships with the environmental parameters (temperature, salinity, and turbidity and phytoplankton distribution) in some sandbanks of the Belgian coastal zone was carried out by the use of Two-Way Indicator Species Analysis (TWINSPAN) and Canonical Correspondence Analysis (CANOCO). There were 49 zooplankters identified all over the three sandbanks. Crustaceans was the most dominant sub-phyla represented mostly by copepods. Other members of plankton community were also present like cladocera, appendicularia, pteropoda and the larger omnivores and carnivores such as hyperiid, amphipod, chaetognath, ctenophore and fish larvae. TWINSPAN did not show a distinct division of the sandbank stations because of the presence of three dominant copepod species (Temora longicornis, Pseudocalanus elongatus and Centropages hamatus) in the three sandbanks. Canonical correspondence analysis (CANOCO) showed that species distribution of zooplankton was significantly affected by the environmental variables. This was due to lower salinity values observed around Buitenratel sandbank than Gootebank and Westhinder sandbanks. Two-Way Indicator Species Analysis analyzed spatial distribution and community structure of zooplankton species over the three sandbanks of the Belgian coastal zone based on species abundance. Canonical Correspondence Analysis (CANOCO) on the other hand, gave an idea on how far these subgroups were related to environmental variables.