Factors in Interpreting Data Obtained by Diel Sampling of Fish Stomachs

1977 ◽  
Vol 34 (2) ◽  
pp. 290-294 ◽  
Author(s):  
Douglas M. Eggers
Keyword(s):  
Feeding Activity ◽  
Equation Model ◽  
Food Level ◽  
Fish Analysis ◽  
Fishing Gear ◽  
Daily Ration ◽  
Diel Pattern ◽  
Gastric Evacuation ◽  
Differential Equation Model ◽  
Feeding Regimes

A simple differential equation model describing the level of food in the stomach, incorporating simultaneous ingestion and gastric evacuation, is used to gauge the sensitivity of methods that utilize diel change in food level of the stomach to determine diel feeding activity of fish. Analysis of model behavior under different feeding regimes shows that diel pattern of food level in the stomach is less sensitive to feeding regime than many authors claim.An expression is derived for the magnitude of bias associated with cessation of feeding and continuance of gastric evacuation while fish are retained by the fishing gear. This bias may be reduced by minimizing sampling time and accelerating preservation of captured fish in experiments to determine feeding chronology and daily ration.

Daily ration and feeding activity of juvenile hake in the central Mediterranean Sea

2008 ◽  
Vol 88 (7) ◽  
pp. 1493-1501 ◽  
Author(s):  
P. Carpentieri ◽  
F. Colloca ◽  
G. Ardizzone
Keyword(s):  
Mediterranean Sea ◽  
Feeding Activity ◽  
Central Italy ◽  
Stomach Contents ◽  
Western Coast ◽  
Daily Ration ◽  
Gastric Evacuation ◽  
Central Mediterranean ◽  
Migratory Activity ◽  
Central Mediterranean Sea

We investigated daily ration, feeding rhythms and gastric evacuation rates of juvenile (<16 cm total length) European hake Merluccius merluccius, using stomach samples collected during four 24-hour trawl surveys carried out in 2001–2002 on the continental shelf-break (from 120 m to 160 m in depth) off the western coast of central Italy (central Mediterranean Sea). In each survey 8 hauls of 30 minutes were performed every three hours throughout the 24-hour period to cover the entire diel cycle. Diet of juvenile hake was mostly composed of the euphausiid Nyctiphanes couchii, showing a peak in stomach contents during early morning followed by a daytime decrease. Fullness index (%FI) was generally higher during sunrise when migratory activity ceased and juvenile hake return to the bottom after feeding. Concerning the hake abundance the highest density value was obtained in May during the recruitment period.Two independent daily ration estimates were produced. First, an empirical attempt to estimate the daily amount of food consumed was obtained by back-calculating the fresh weight of euphausiid prey ingested by juvenile hake. Estimated values ranged from 4.96–5.89% body wet weight (%BW). Second, the daily ration was computed applying the exponential gastric evacuation models proposed by Elliot & Persson (1978) and Eggers (1979). Daily ration values obtained using these consumption models produced a considerable (15–20%) underestimation of consumption rate for juvenile hake.

Minimising waste through bioenergetically and behaviourally based feeding strategies

1995 ◽  
Vol 31 (10) ◽  
pp. 29-40 ◽  
Author(s):  
J. E. Thorpe ◽  
C. Young Cho
Keyword(s):  
Feeding Activity ◽  
Activity Patterns ◽  
Growth Efficiency ◽  
Wild Food ◽  
Feeding Strategies ◽  
Physico Chemical ◽  
Evolutionary Features ◽  
Feeding Regimes ◽  
In The Wild ◽  
Genetically Determined

Most species in aquaculture are new to cultivation and so behave like wild animals. They are products of evolution, with adaptations to specific habitat conditions. In the wild, food is not available uniformly throughout the day or the year, or in space, and rarely exceeds the fishes needs. Competition is energetically expensive, reducing growth efficiency. Consequently, feeding activity patterns have evolved, implying internal appetite rhythms, which optimise food intake under these various constraints. Salmonids can adapt quickly to short term variation in food availability, but show seasonal genetically determined anorexia. Rational feeding regimes in culture should take all such features into account. When appetite is high naturally, food should be presented so that it is economically indefensible - where every individual can eat, and where fighting does not pay. At periods of anorexia it will be prudent to offer no food. Manufacturers' feed tables are usually regimes devised to meet the bioenergetic needs of fishes, as they are understood in a physico-chemical sense. While useful first approximations, they do not take into account these evolutionary features of the fishes, and can lead to waste. Methods of presentation are described which allow the fish to determine when food shall be available, and in ways which, by diminishing the advantages of social dominance, ensure relatively even opportunities to feed for all individuals in the population. Allowing the fish to set the time-table reduces the likelihood of waste.

scholarly journals A spatially varying stochastic differential equation model for animal movement

2018 ◽  
Vol 12 (2) ◽  
pp. 1312-1331 ◽  
Author(s):  
James C. Russell ◽  
Ephraim M. Hanks ◽  
Murali Haran ◽  
David Hughes
Keyword(s):  
Differential Equation ◽  
Stochastic Differential Equation ◽  
Animal Movement ◽  
Equation Model ◽  
Differential Equation Model ◽  
Spatially Varying

scholarly journals A Stochastic TB Model for a Crowded Environment

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Sibaliwe Maku Vyambwera ◽  
Peter Witbooi
Keyword(s):  
Compartmental Model ◽  
Deterministic Model ◽  
Reproduction Number ◽  
Stochastic Perturbation ◽  
Equation Model ◽  
Ordinary Differential Equation Model ◽  
Differential Equation Model ◽  
The Stability ◽  
Crowded Environments ◽  
Disease Free

We propose a stochastic compartmental model for the population dynamics of tuberculosis. The model is applicable to crowded environments such as for people in high density camps or in prisons. We start off with a known ordinary differential equation model, and we impose stochastic perturbation. We prove the existence and uniqueness of positive solutions of a stochastic model. We introduce an invariant generalizing the basic reproduction number and prove the stability of the disease-free equilibrium when it is below unity or slightly higher than unity and the perturbation is small. Our main theorem implies that the stochastic perturbation enhances stability of the disease-free equilibrium of the underlying deterministic model. Finally, we perform some simulations to illustrate the analytical findings and the utility of the model.

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