Predicting use of habitat patches by spawning horseshoe crabs (Limulus polyphemus) along a complex coastline with field surveys and geospatial analyses

相似文献   

Salmon testes meal as a functional feed additive in fish meal and plant protein‐based diets for rainbow trout (Oncorhynchus mykiss Walbaum) and Nile tilapia (Oreochromis niloticus L.) fry

Fishery processing by‐products are a large resource from which to produce fishmeal and other products for a variety of uses. In this study, testes meal (TM) produced from pink salmon processing by‐product was evaluated as a functional ingredient in aquafeeds. Nile tilapia and rainbow trout fry were fed five isonitrogenous and isoenergetic experimental diets for 4 and 9 weeks respectively. Two diets were fishmeal‐based (FM) and three were plant protein‐based (PP). Salmon TM was added to the FM and PP diets at 7% to replace 20% of fishmeal protein (FMTM and PPTM respectively). An additional control diet was prepared in which fishmeal was added to the PP diet to supply an equivalent amount of protein as supplied by TM (PPFM). Inclusion of TM in both the FM‐ and PP‐based diets resulted in higher final body weights, although differences were only significant between rainbow trout fed FM or FMTM diets. Similar differences were calculated for other indices of fish performance, e.g. specific growth rate, feed conversion ratio, protein efficiency ratio and protein retention efficiency. Feed intake was significantly higher for fish fed FMTM compared with FM in rainbow trout. For tilapia, final weights were numerically higher, but not significantly different for fish fed diets containing TM compared with non‐TM diets (FM vs. FMTM; PP vs. PPTM). Performance of trout or tilapia fed the PPFM diet did not increase compared with the PP diet. The results indicate that TM addition to both FM and PP diets increased feed intake and also increased metabolic efficiency, demonstrating that TM can be a functional ingredient in aquafeeds.     

Cell wall disruption: An effective strategy to improve the nutritive quality of microalgae in African catfish (Clarias gariepinus)

The rigid cell walls of microalgae may hinder their utilization in fish feeds. The current experiment assessed the correlation between the accessibility of microalgae nutrients and their in vivo digestibility in African catfish. Nannochloropsis gaditana biomass was subjected to physical or mechanical treatments to weaken its cell wall; untreated—no disruption treatment (UNT), pasteurization (PAS), freezing (FRO), freeze‐drying (FRD), cold pasteurization (L40) and bead milling (BEM). Six experimental diets formulated from differently treated and untreated microalgae (at 30% diet inclusion level) were tested on growth performance and apparent nutrient digestibility (ADCs) in juvenile African catfish. A basal diet (REF) containing no microalgae was used as reference diet. Results showed that biomass gain and feed conversion ratio of fish fed L40 and BEM diets increased by 13% and 11%, respectively, relative to the UNT diet. Additionally, FRD, FRO, L40 and BEM cell wall disruption treatments improved protein digestibility by 0.5%, 5.9%, 8.4% and 16.3%, respectively, compared to the UNT treatment. There was a positive correlation between accessibility of microalgal nutrients and their digestibility in African catfish. Nutrient digestibility of microalgae was dependent on extent of cell disruption. Also, the impact of cell disruption on nutrient digestibility of microalgae differs between African catfish and Nile tilapia.     

A GIS-based plant prediction model for wetland ecosystems

An existing non-spatial model for the prediction of response of wetland plant species on ecological factors has been transformed into a GIS-based prediction model which produces spatial output at the landscape scale. The input, spatial patterns of the ecological factors, were constructed with geostatistical spatial interpolation (kriging). With this GIS-based model the spatial patterns of presence and absence of 78 wetland plant species are predicted for an area with wetlands in the Netherlands of approximately 500 square kilometers. The GIS-based model has been validated, and the estimated uncertainty of the input has been propagated through the model. At the species level the output shows spatially coherent and non-random patterns. The validation is affected by the propagation of input errors through the model. The number of valid predictions declines approximately 10–20% when 95% confidence intervals are used in the validation. This study shows that it is feasible to use a geostatistical interpolation method to construct spatial patterns of ecological factors on a landscape scale and to use these patterns as input for a GIS-based prediction model. The added uncertainty on the input values however, affects the number of valid predictions of the model.     

System for quasi‐continuous simultaneous measurement of oxygen diffusion rate and redox potential in soil

Oxygen diffusion rate (ODR) and redox potential (E_H) are quantitative indices representing oxygen availability and redox status in soils, which is valuable information for better understanding causes and effects of soil aeration. Because these indices are spatially and temporally highly variable, continuous measurements and adequate numbers of repetitions are essential for accurate in situ monitoring. Here, we present a new, fully automated recording system for in situ measurements where ODR and E_H are measured at the same platinum electrode. The conflict between electrode polarization for ODR and the resulting biased E_H readings is solved by reducing the polarization time and introducing a recovery interval between two consecutive measurement cycles. The shorter polarization time ensures accurate E_H readings. It also results in moderately overestimated ODR readings, but this can be corrected before data analysis. The recovery interval restricts temporal resolution of the E_H‐ODR data pairs to 8 h. We illustrate the use of the system with measurements in a field experiment in Zürich, Switzerland. ODR curves at different depths ran roughly parallel to the corresponding curves of O₂ concentration in soil air but ODR was much more sensitive to precipitation. Low ODR was a necessary but not a sufficient condition for declining E_H. E_H ran parallel to O₂ concentration in soil air rather than to ODR. The fully automated system allows for time series of replicate measurements in multifactorial field studies with reasonable labor requirements. It may be particularly suitable for studies examining the effects of soil tillage, compaction, and irrigation, where structure‐related soil properties such as porosity, gas permeability, and soil aeration play a dominant role.     

Rassen der gemeinen Kiefer

Ohne Zusammenfassung