22 research outputs found
Variation in the food intake of grass carp, Ctenopharyngodon idella (Val.), fed singly or in groups
Each animal may be assumed to possess a unique
combination of physiological traits (Bennett, 1987).
However, there is little information on thc effects of
interindividual variation in fish (Cui and Liu, 1990).
Individual differences in competitive ability, aggressiveness
and or size can lead to the establishment of
dominance hierarchies within groups of fish (Metcalfe,
1989; Metcalfe et al., 1989). The variation in
growth rates in groups of fish are rclated to dominance
hierarchies and preferential access to food
resources by dominant individuals (Jenkins, 1969;
Fausch, 1984; Koebele, 1985). Recently, radiography
has been used to measure individual consumption
rates for groups of salmonids and has demonstrated
considerable inter-individual variation in food intake
(Jobling et al., 1989; Carter et al., 1992a; McCarthy
et al., 1992). Two aims of this study were to use
radiography to examine the variation in the food
consumption rate of grass carp, Ctenopharyngodon
idellu (Val.), held together and to assess whcther variation
in growth rates could bc explained by variation
in consumption rates. A final aim of this study was
to compare the day to day variation in consumption
rates of grass carp held in a group to thosc held
individually, in terms of the individual meal share, in
order to examine the cffect of endogenous influences
on appetite
Swimming physiology of European silver eels (Anguilla anguilla L.): energetic costs and effects on sexual maturation and reproduction
The European eel migrates 5,000–6,000 km to the Sargasso Sea to reproduce. Because they venture into the ocean in a pre-pubertal state and reproduce after swimming for months, a strong interaction between swimming and sexual maturation is expected. Many swimming trials have been performed in 22 swim tunnels to elucidate their performance and the impact on maturation. European eels are able to swim long distances at a cost of 10–12 mg fat/km which is 4–6 times more efficient than salmonids. The total energy costs of reproduction correspond to 67% of the fat stores. During long distance swimming, the body composition stays the same showing that energy consumption calculations cannot be based on fat alone but need to be compensated for protein oxidation. The optimal swimming speed is 0.61–0.67 m s−1, which is ~60% higher than the generally assumed cruise speed of 0.4 m s−1 and implies that female eels may reach the Sargasso Sea within 3.5 months instead of the assumed 6 months. Swimming trials showed lipid deposition and oocyte growth, which are the first steps of sexual maturation. To investigate effects of oceanic migration on maturation, we simulated group-wise migration in a large swim-gutter with seawater. These trials showed suppressed gonadotropin expression and vitellogenesis in females, while in contrast continued sexual maturation was observed in silver males. The induction of lipid deposition in the oocytes and the inhibition of vitellogenesis by swimming in females suggest a natural sequence of events quite different from artificial maturation protocols
Symbiont photosynthesis increases both respiration and photosynthesis in the symbiotic sea anemone Anemonia viridis
Modulation of a rhythmic activity by serotonin via cyclic AMP in the coelenterateRenilla k�llikeri
Modulation of rhythmic contractions by melatonin via cyclic GMP in the coelenterate Renilla koellikeri
Respiratory responses of three Antarctic ascidians and a sea pen to increased sediment concentrations
Glacial retreat and subglacial bedrock erosion are consequences of rapid regional warming on the West Antarctic peninsula. Sedimentation of fine grained eroded particles can impact the physiology of filter feeding benthic organisms. We investigated the effect of increasing concentrations of sediment on the oxygen consumption of suspension feeding species, the ascidians Molgula pedunculata, Cnemidocarpa verrucosa, Ascidia challengeri, and the pennatulid Malacobelemnon daytoni in Potter Cove (South Shetland Islands, Antarctica). In A. challengeri and C. verrucosa oxygen consumption increased gradually up to a critical sediment concentration (Ccrit) where species oxygen consumption was maximal (Omax in mg O2 g-1 dm d-1) and further addition of sediments decreased respiration. Ccrit was 200 mg L-1 for A. challengeri (Omax of 0.651 ± 0.238) and between 100 and 200 mg L-1 for C. verrucosa (Omax of 0.898 ± 0.582). Oxygen consumption of M. pedunculata increased significantly even at low sediment concentrations (15-50 mg sediment L-1). Contrary to the ascidians, sediment exposure did not affect oxygen consumption of the sea pen. The tiered response to sedimentation in the four species corroborates recent field observations that detected a reduction in abundance of the sensitive ascidian Molgula pedunculata from areas strongly affected by glacial sediment discharge, whereas sea pens are increasing in abundance. Our investigation relates consequences (population shifts in filter feeder communities) to causes (glacial retreat) and is of importance for modelling of climate change effects in Antarctic shallow coastal areas
Biotic and abiotic factors determining the distribution of two prawn species: Palaemon adspersus and P. squilla
Modelling the risk of mortality of Corbicula fluminea (Müller, 1774) (Bivalvia: Corbiculidae) exposed to different turbidity conditions
Acid-base, plasma ion and blood gas changes in rainbow trout during short term toxic zinc exposure
Impact of fermented mulberry leaf and fish offal in diet formulation of Indian major carp (Labeo rohita)
Large quantities of fish offal and mulberry leaf are generated globally. The present study aimed to understand their potential utilization in aqua diet formulation, after proper fermentation, as raw materials to replace fish meal in Indian major carp (Labeo rohita) compounded diet. Fish offal meal (FOM) and mulberry leaf meal (MLM) were used in a 2 × 3 factorial design, to evaluate (i) two different fermented mixtures with the inclusion of both FOM and MLM or only MLM and (ii) to replace three different level of dietary fishmeal: 50, 75 or 80 %. An indoor trial, to evaluate diet intake and digestibility and an outdoor trial to evaluate growth performances were impended in Indian major carp fingerlings. The results showed that FOM and MLM are promising raw materials that can be successfully used in the formulation of diet for the Indian major carp. Specifically, the addition of a proper amount of MLM in the fermentation of FOM produced a fermented mixture that could successfully replace up to 80 % of FM in the diet formulation