it has often been stated or implied that grazing is an important factor in the land degradation process, a suggestion supported by various research projects, and this study investigated the effect of livestock grazing on stem height, crowncover, production, basal diameter, stem biomass, litter, leaf-stem index (leaf to stem weight) , root diameter and weight and seed production per individual o...

The cues triggering large-scale broadcast-spawning events in marine invertebrates are not fully understood. Using the sea urchin Lytechinus variegatus, we tested the effectiveness of a variety of potential spawning cues in eliciting a spawning response. In the laboratory, during two consecutive spawning seasons, about 400 isolated sea urchins were exposed to phytoplankton, sperm, or eggs, singl...

Ž . The productivity of Nile tilapia Oreochromis niloticus L. broodfish, spawned in large hapas Ž 2. 120 m in ponds under different exchange and management strategies, was monitored over a 70-day period. Female fish were checked for eggs twice weekly and returned to the same Ž . spawning hapa throughout the experiment 0 day or exchanged for females maintained in separate Ž . Ž . single sex grou...

School of Environment and Natural Resources Ohio State University Extension Columbus, Ohio, USA Leonardo et al. (2004) obtained 100% ovulation in females of P. fasciatum maintained in ponds in Sao Paulo State, Brazil, following hormonal injections of carp pituitary extract (CPE) or human chorionic gonadotropin (hCG). In that study, the most detailed thus far, females released between 17 and 20%...

  The population parameters and spawning season of the Spangeld emperor (Lethrinus nebulosus) were studied in coastal waters of Hormouzgan province. The monthly calculated mean values of gonadosomatic index (GSI) of females were indicate to increase from February, reach the highest in March and decline in June. The spawning season peak of L. nebulosus occurred in March. The Von Bertalanffy grow...

Few time series of deep-sea systems exist from which the factors affecting abyssal fish populations can be evaluated. Previous analysis showed an increase in grenadier abundance, in the eastern North Pacific, which lagged epibenthic megafaunal abundance, mostly echinoderms, by 9-20 months. Subsequent diet studies suggested that carrion is the grenadier's most important food. Our goal was to eva...

Population attributes and migratory dynamics of spawning pink salmon Oncorhynchus gorbuscha were examined in U.S. waters of the St. Marys River from 1998 through 2002. Spawning migrations were monitored twice each week from late August through early October of each sampling year using a single gill net set immediately below their spawning grounds. Pink salmon were captured between 23 August and...

Understanding of the processes affecting recruitment of commercially important fish species is one of the major challenges in fisheries science. Towards this aim, we investigated the relation between North Sea hydrography (temperature and salinity) and fish stock variables (recruitment, spawning stock biomass and pre-recruitment survival index) for 9 commercially important fishes using spatiall...