Feeding and Vertical Migration of the Chaetognath Sagitta Friderici (ritter-zahony, 1911) in the Southern Benguela during Spring 1987, with Notes on Seasonal Variability of Feeding Ecology
نویسنده
چکیده
The feeding biology and the vertical migration of Sagitta friderici were examined over 24 h at two stations in the southern Benguela during spring (October) 1987. Together with studies conducted during summer (February 1991) and winter (May 1984), they serve to allow valuable generalizations of the biology and ecology of this abundant chaetognath. Populations migrate vertically and feed nocturnally, although the timing and the extent of migration vary between studies. S. friderici exhibits ontogenetic layering and the cross-shelf distribution of maturity stages differs, suggesting that it is able to take advantage of cross-shelf water movement in order to maintain populations in the nearshore waters of the West Coast. S. friderici prey almost exclusively on copepods (cannibalism is rare), and there is a positive relationship between the lengths of predator and prey that is influenced by the size structure of the prey environment. This casts doubt on the validity of a chaetognath species-specific relationship between predator and prey size. S. friderici selects its prey on the basis of size, and not species. Daily ration is related linearly to prey density, so reflecting the low density of prey and providing support for theoretical predictions regarding ingestion rates under oceanic conditions. The impact of S. friderici predation on the copepod assemblage is generally less than 3% of the standing stock, although it could be much higher under conditions of low copepod biomass and poor secondary production.
منابع مشابه
Short communication:A study of food consumption of the deepwater Goby, Ponticola bathybius (Kessler, 1877), during spring migration in the southern Caspian Sea
متن کامل
Reproduction and structure of the population of the Chaetognath Parasagitta friderici in Guanabara Bay (Brazil) based on short term sampling.
The aim of this study was to describe the total density, densities of developmental stages and the reproduction period of Parasagitta friderici. Weekly samples were collected at one station in the channel of Guanabara Bay, Rio de Janeiro, during one year. Three vertical hauls were made for each sample, and P. friderici was separated, the developmental stages were identified, and body length (BL...
متن کاملAquatic Biosystems
Background: Predatory copepods of the family Euchaetidae are widely distributed in polar, temperate, subtropical and tropical oceans. Paraeuchaeta concinna is the most abundant Euchaetidae in the subtropical coastal seas of Hong Kong and southern China. However, compared to Euchaetidae species in temperate and polar regions, relatively little information is available on the ecology of P. concin...
متن کاملAge determination and feeding habits of Nemipterus japonicus (Bloch, 1791) in the northern Oman Sea
Age determination and feeding habits of the Japanese threadfin bream, Nemipterus japonicus, was carried out in the northern Oman Sea (Chabahar area), based on 212 specimens collected between September 2009 and May 2010. The minimum and maximum fork length and body weight were measured as 145, 258 mm and 55.31, 288.12 g. The relationship between Body Weight (BW) and Fork Length (FL) for all indi...
متن کاملAge determination and feeding habits of Nemipterus japonicus (Bloch, 1791) in the northern Oman Sea
Age determination and feeding habits of the Japanese threadfin bream, Nemipterus japonicus, was carried out in the northern Oman Sea (Chabahar area), based on 212 specimens collected between September 2009 and May 2010. The minimum and maximum fork length and body weight were measured as 145, 258 mm and 55.31, 288.12 g. The relationship between Body Weight (BW) and Fork Length (FL) for all indi...
متن کامل