Gastric Digestion, Food Consumption, Feeding Periodicity, and Food Conversion Efficiency in Walleye (Stizostedion vitreum vitreum)

Abstract

Gastric digestion of walleye, Stizostedion vitreum vitreum, and sauger, Stizostedion canadense, was measured by pumping stomachs at various intervals after experimental meals had been force-fed or voluntarily consumed. No significant differences in digestion rates were found between species or among walleye taken from three lakes. Repeated use of fish in digestion experiments failed to influence results. Gastric digestion rate increased with fish size, but was depressed by increased meal size, food particle size, and by force-feeding experimental meals.Food consumption rate and feeding chronology of the strong 1966 year-class of Lake of the Woods walleye were determined by applying results of laboratory digestion studies to stomach samples. An estimating technique that takes into account the effects of factors shown to influence digestion in the laboratory was developed and used to make calculations for the field population. Consumption averaged 1% of body weight during June, 2% during July, and 3% during August and September. Average temperatures were similar during June and September. Greater consumption during September resulted from higher food availability. Feeding was greatest during night and early morning hours in all months except June when it was continuous. Conversion efficiency of the 1966 year-class was described from estimates of growth and consumption rates for June through September and approximated 20% during each month.

A dieta e o consumo diário de alimento de Cichla monoculus na Amazônia Central

“…A partir do comprimento padrão de cada presa identificada no conteúdo estomacal, foi estimado o peso da presa no momento em que foi ingerida pelo tucunaré através de regressões peso/ comprimento (Swenson & Smith, 1973 A cada tucunaré foi oferecido um exemplar de T. rendalli, com peso aproximado de 3% do predador (3,93 a 12,22 g), e com nadadeira anal cortada, para dificultar o natação. A tilápia era amarrada por uma linha na superfície do tanque.…”

“…Na Bacia do Orinoco, durante a estação de seca, o principal item alimentar identificado foi composto de peixes das ordens Characiformes, Perciformes e Siluriformes, com freqüência média de 78,1%, 14,1% e 7,8%, respectivamente (Winemiller et al, 1997). Uma exceção ocorreu num reservatório natural, onde Peixoto (1982) Swenson & Smith (1973) e Andersen (1999.…”

“…A taxa de conversão alimentar seria então igual a 0,11 (grama de peixe / grama de alimento) ou 11%. Este valor também é inferior ao apresentado para outros piscívoros com táticas de caça semelhante, como, Perca flavescens e Stizostedium vitreum (Swenson & Smith, 1973;Brett, 1979;Adams et al, 1982), cuja média é 20%. Aumentandose a taxa de consumo de alimento, reduziria a taxa de conversão alimentar a valores inferiores a 10% o que seria muito baixo para um peixe piscívoro.…”

Nonlethal Methods of Examining Fish Stomach Contents

“…Gengerke et al (1973) stated that this method had been used on nine species of fish without any operational difficulties. Swenson and Smith (1973) used fired-glass tubes with a stomach pump. Fired-glass tubes prevented damage to the stomach lining and allowed visual observation for completeness of pumping (Swenson and Smith, 1973).…”

“…Swenson and Smith (1973) used fired-glass tubes with a stomach pump. Fired-glass tubes prevented damage to the stomach lining and allowed visual observation for completeness of pumping (Swenson and Smith, 1973).…”