Potential fishery of Nile perch Lates niloticus Linne (Pisces: Centropomidae) in Nyanza Gulf of Lake Victoria,East Africa

From bottom trawls, Lates niloticus (Lin.) in Nyanza Gulf was observed to have a gulf-wide distribution. Lates dominated the catch at Homa point. Catch rates in kg h^-1 varied from one location to another and from month to month.Its estimated production is 11 000 metric tons, netting about 22 000 000 Kenya shillings (US $2 000 000).Abundance of food items such as freshwater shrimps of the genus Caridina, and Engraulicypris argenteus, have been used as basis for estimating the growth and production of Lates.     

DYNAMIC RESPONSE ANALYSIS. I. QUALITATIVE ESTIMATION OF STOCKSTATUS RELATIVE TO MAXIMUM NETPRODUCTIVITY LEVEL FROMOBSERVED DYNAMICS

A qualitative determination of whether a population is above or below its MNPL can be carried out under circumstances where the value of the MNPL itself, and other details of the production curve, cannot be estimated. This qualitative assessment may often be sufficient for management decisions. The method proceeds by locally approximating the production curve, in the neighborhood of the present population density, from data on population sizes and harvests, and then determining whether this represents the ascending or descending arm of the curve. When the harvests are small, or when the harvests are a constant fraction of the production, the population-size data need only be relative. With adequate quantities of data, this assessment method can accommodate random measurement error and random perturbations in the dynamics of the population system.     

Subtle population structuring within a highly vagile marine invertebrate, the veined squid Loligo forbesi, demonstrated with microsatellite DNA markers

Microsatellite DNA markers were applied for the first time in a population genetic study of a cephalopod and compared with previous estimates of genetic differentiation obtained using allozyme and mitochondrial DNA (mtDNA) markers. Levels of genetic variation detected with microsatellites were much higher than found with previous markers (mean number of alleles per locus=10.6, mean expected heterozygosity ( H _E)=0.79; allozyme H _E=0.08; mtDNA restriction fragment length polymorphism (RFLP) H _E=0.16). In agreement with previous studies, microsatellites demonstrated genetic uniformity across the population occupying the European shelf seas of the North East Atlantic, and extreme genetic differentiation of the Azores population ( R _ST/ F _ST=0.252/0.245; allozyme F _ST=0.536; mtDNA F _ST=0.789). In contrast to other markers, microsatellites detected more subtle, and significant, levels of differentiation between the populations of the North East Atlantic offshore banks (Rockall and Faroes) and the shelf population ( R _ST=0.048 and 0.057). Breakdown of extensive gene flow among these populations is indicated, with hydrographic (water depth) and hydrodynamic (isolating current regimes) factors suggested as possible barriers to migration. The demonstration of genetic subdivision in an abundant, highly mobile marine invertebrate has implications for the interpretation of dispersal and population dynamics, and consequent management, of such a commercially exploited species. Relative levels of differentiation indicated by the three different marker systems, and the use of measures of differentiation (assuming different mutation models), are discussed.     

Productivity of the aquatic macrophyte Pontederia lanceolata Nvtt. (Pontederiaceae) on floodplains of the Pantanal Mato-grossense,Brazil

The Pantanal Mato-grossense is an extensive floodplain system located in the center of South America with important macrophytic primary producers. This study describes the dynamics of net primary production and the biomass of the aquatic macrophyte Pontederia lanceolata, the dominant species in some floodplain fields near Poconé. Productivity was determined from a combination of demographic and growth methods. Biomass was determined using squares of known area, periodically distributed at random. The average productivity during the period was 3.11 g dry weight m^-2 day^-1. The minimum and maximum values (0.04 g dry weight m^-2 day^-1 and 8.59 g dry weight m^-2 day^-1, respectively) occurred during the drought and the flood period, respectively. The standing stock varied between 12.7 and 235.9 g dry weight m^-2, determined at the beginning of the flood and at its peak, respectively. The dynamics of the productivity and the standing stock of the species are associated with the flood patterns of the area and with life cycle of the plant.     

How are biodiversity and carbon stock recovered during tropical forest restoration? Supporting the ecological paradigms and political context involved

To meet agendas for biodiversity conservation and mitigation of climate change, large-scale restoration initiatives propose ecological restoration as an alternative that can reconcile these two objectives. In ongoing ecosystem restoration, increased diversity is always associated with increased productivity (and consequent carbon stock), which is among the most important ecosystem functions. The ecological paradigm of this association is that ecosystem biodiversity (B) is positively related to both ecosystem functions and services (EF and ES). However, BEF and BES relationships vary spatially and temporally, which makes understanding these relationships relevant and important for practical restoration actions. In this study, we asked how biodiversity and carbon stock recovery occurs during tropical forest restoration. We reviewed literature of the relationships between BEF and BES in the context of ecological restoration and asked whether ecological restoration can recover both. In addition, we conducted a metadata analysis of studies on the recovery of biodiversity and biomass in regenerating tropical forests (n = 83) to find the best model that describes this relationship. In general, studies showed that ecosystem biodiversity and productivity are positively related, and that restoration can recover both. We found an asymptotic and positive correlation between biodiversity and biomass in tropical forests, suggesting limitation of the mutual gains of these two ecosystem properties during restoration. We discuss these results in the context of ecological theory and the practice of ecological restoration.