The annual cycle of the vertical distribution oxygen concentrations at a deep water station on Lake Victoria in 1990–1991 was compared with data collected 1960–1961. Oxygen mixed layer are higher now, nearly continuous supersaturation surface waters. hypolimnetic waters lower now for longer period, values <1 mg liter−1 occurring as shallow 40 m shallowest occurrence >50 1961. changes oxygenation consistent measurements algal biomass and productivity. causes eutrophication yet undetermined,...

Seasonal variations in the carbon isotope composition of components pelagic food web Lake Kinneret were recorded and compared with those for bulk plankton from lake early 1970s. Individual planktonic as well isotopically lightest shortly after overturn January heaviest May, peak annual bloom dinoflagellate Peridinium gatunense. The range δ 13 C values observed over an cycle seasonal means varied considerably between taxa. Within primary producers, P. gatunense (range, −23.2 to −17.9‰) was...

SUMMARY. The diet and feeding habits of natural cultured populations Mesocyclops leuckarti were studied. Nauplii copepodid stages I–III are herbivorous. Copepodid IV–V adults preferentially preyed upon Ceriodaphnia Diaphanosoma whereas Bosmina was not upon. Rate predation on newborn Artemia nauplii higher between 15–22°C than 22–27°C. Under starvation conditions, the survival time for males shorter females.

In laboratory experiments, feeding rates of small (40–61‐mm standard length, SL) and large (98–143‐mm Galilee Saint Peter’s fish ( Tilapia galilaea ) on phytoplankton zooplankton increased as a function particle size, leveling off when size exceeded 6–10 µ m. Fish had high zooplankton, the dinoflagellates Peridinium cinctum elpatiewsky, few nanoplankton, but most species nanoplankton were consumed at lower rates. To examine community‐level effects fish, we conducted two 7‐d outdoor tank...

Summary The abundance of Ceriodaphnia reticulata (Jurine) in Lake Kinneret is restricted every year to the period March June with a peak May. most constant parameter accompanying temperature range 20–22° C. An attempt was made clarify whether estival high average temperatures observed epilimnion this lake (27–28° C) could explain decrease population. Three physiological parameters: food intake, ammonia excretion and respiration rates, were measured experimentally at three (15, 22 27° C). dry...

Analysis of long‐term records temperature profiles in subtropical Lake Kinneret revealed changes thermal stratification during the period 1969–1991. Thermocline depth and rate seasonal thermocline deepening have decreased stable has increased. These appear related to a decline mean winter air temperatures, which produced cooler hypolimnetic waters increased density gradients across metalimnion. structure been accompanied by increases phosphorus concentrations phytoplankton abundances...

Recent investigations in Lake Kinneret, Israel, indicated that physical, chemical and biological changes took place from 1973 onwards. The modifications observed zoo-plankton populations were analysed related to concomitant noted the population of Mirogrex terraesanctae (Kinneret sardine), which is main predator zooplankton. cladocerans Diaphanosoma sp., Bosmina spp. Ceriodaphnia found be preferential food sources for when compared with Copepoda. In first half 1974, biomass productivity...

1. Daphnia lumholtzi is a subtropical, Old World species which rapidly spreading throughout reservoirs in the southern U.S.A. It was first recorded Lake Texoma (Oklahoma–Texas) September 1991. 2. Southern U.S. typically have strong spatial and temporal gradients temperature, conductivity, turbidity distribution of organisms. Therefore, present experiments examined reproductive moulting rates, survival D . relation to extremes food concentration, conductivity turbidity. 3. Increases...

Dramatic changes in the Lake Victoria (East Africa) environment were observed after introduction of Nile perch (Lates niloticus) 1950s. An extraordinary spectrum endemic haplochromine fishes, a result intralacustrine adaptive radiation was reduced by massive species extinctions (ca. 65%) due part to predation Perch. Such an abrupt destruction natural diversity has never before been documented scientists. Victoria's flock comprised upwards 400 (5% world's known freshwater fishes),...

Particle ingestion by filter-feeding Galilee Saint Peterˈs fish Tilapia galilaea increased as a function of particle size, leveling off when diameter exceeded 20 μm. Ingestion rates this cichlid also with concentration, asymptotically approaching maxima 4,785 and 84,746 particles˙fish −1˙min−1 for small (3.9–6.0 cm standard length, SL) large (12.6–14.3 fish, respectively. Surgical removal gill rakers microbranchiospines did not affect or selectivity.

In an experimental study the cyclopoid copepod Corycaeus anglicus Lubbock was found to ingest Artemia nauplii at much higher rates (up 15 times) in light than dark. Maximal ingestion observed represent daily rations of 70% and 66% body carbon for males females respectively. From observations together with studies ultrastructure photoreceptors it is suggested that can locate prey visually. This contrast majority other copepods which use chemoreceptors mechanoreceptors.