Effects of salinity, aeration and light intensity on oil globule absorption, feeding incidence, growth and survival of early-stage grouper Epinephelus coioides larvae

ABSTRACT: A series of experiments were conducted to examine the effects of salinity, aeration and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage Epinephelus coioides larvae. Newly hatched larvae were transferred to 40-L aquaria at a density of 1500 individuals/aquarium. Larvae were exposed to different levels of aeration (0 mL/min per L, 0.62 mL/min per L, 1.25 mL/min per L, 2.50 mL/min per L, or 3.75 mL/min per L); salinity (8 ppt, 16 ppt, 24 ppt, 32 ppt, or 40 ppt); and light intensity (0 lx, 120 lx, 230 lx, 500 lx, or 700 lx) for 4–6 days. Twenty larvae were sampled daily at 11:00 hours to measure for total length (TL), oil globule volume, and feeding incidence. Survival rates were determined by counting the total number of larvae remaining in each aquarium at the end of the experiment. Significantly higher survival rates ( P   <  0.05) were observed at aeration levels of 0.62 mL/min per L and 1.25 mL/min per L, at salinity levels of 16 ppt and 24 ppt, and at light intensities of 500 lx and 700 lx. The influence of aeration level, salinity and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage grouper larvae are discussed.     

Herbage measurement in situ by electronics. 3. Calibration, characterization and field application of the earth-plate forage capacitance meter: a prototype

Calibration of an earth-plate forage capacitance meter was conducted on pure stands of Festuca arundinacea Schreb., Medicago sativa L., Cynodon dactylon (L.) Pers. and Trifolium repens L. and a mixture of Trifolium repens and Dactylis glomerata L. Dry weight (DW) prediction equations were developed using the instrument capacitance reading modified by visual estimates of height, stand density and species percentage. In general, meter readings (MR) correlated better with DW than with fresh weight or weight of water and especially when the area harvested exceeded 0·537 m². Correlation between MR and DW improved with increasing top plate area and with decreasing distance between the top plate (suspended sheet of aluminium) and the earth-plate ground. The use of a plastic shield to suppress the forage to a uniform height caused a reduction in the correlation between MR and DW.
The use of MR to predict DW from selected settings, their linear and curvilinear relationships and several auxiliary observations gave results with R ² values ranging from 0·94 to 0·99, depending on species and mixture.     

Herbage measurement in situ by electronics. 1. The multiple-probe-type capacitance meter: a brief review

The history and development of the multiple-probe capacitance meter used for in situ , non-destructive estimations of herbage mass is reviewed. An elementary, semi-theoretical electric-field analysis focuses attention on the inherent difficulties associated with the multiple-probe approach. This report establishes the background for the introduction of an 'earth-plate' capacitancemeter.     

Herbage measurement in situ by electronics 2. Theory and design of an earth-plate capacitance meter for estimating forage dry matter

A forage capacitance-measuring scheme is presented which uses the earth and plants growing in it as one plate of a two-plate capacitor. Low frequency analogue circuitry is coupled with digital circuitry to sense and read out digitally the capacitance as a function of the forage under the sensing head. The circuitry is linear, reasonably stable and offers the opportunity for electrically confining the sensed area. The apparatus behaviour is characterized by a mathematical describing function.