A new method for assessing fish feeding rhythms using demand feeders and automated data acquisition

A new approach to monitoring fish feeding rhythms and associated environmental variables is described. This system includes demand feeders attached to load cells to monitor feed consumption, and environmental probes to monitor variables such as temperature, solar radiation, barometric pressure, dissolved oxygen, turbidity, and pH. Measurements from the load cells and probes are recorded at some desired time interval on a data logger, and the data are then analyzed for correlations between feed consumption and environmental conditions. An example of feed consumption rhythms by Chinese catfish (Clarias fuscus) is given.     

Nutritional Depletion of the Aquaculture Feed Organisms Euterpina acutifrons, Artemia sp. and Brachionus plicatilis During Starvation

The nutritional quality of the harpacticoid copepod Euterpina acutifrons , freshly-hatched Artemita nauplii, juvenile and adult Artemia , and the rotifer Brachionus plictatilis , in fed and starved conditions, was evaluated through the use of ratios of dry weight to wet weight (DW/WW), ash-free dry weight to dry weight (AFDW/DW), calories per mg ash-free dry weight (cal/mg AFDW), and carbon to nitrogen by weight (C/N). E. acutifrons had in nearly all cases the highest values of DW/WW, AFDW/DW, and cal/mg AFDW. Calculated losses in caloric content per unit of wet weight (cal/mg WW) during one day's starvation were similar among species, ranging from 3 to 52 percent. C/N ratios were less variable, but also reflected starvation-related changes indicating depletion of C relative to N, which is consistent With depletion of lipids and carbohydrates relative to protein.
Because little or no change in caloric density of organic material (cal/mg AFDW) was observed in any species under either condition, decreases in caloric content of wet weight or of individuals were due to decreases in DW/WW and AFDW/DW. Caloric content and carbon content were related by the factor 11.3 cal/mg C. Starvation-related losses in the nutritional value of forage organisms can be important in larval rearing systems.