18 Questions
What is a major problem with using the method of estimating food volume in fish samples based on percentage of stomach contents?
Water trapped within the item may cause large errors in the estimate.
How can the original properties of food items be restored to overcome the advantage resulting from the difference in the speed of food item digestion?
By taking the original volume or weight of the food item.
What is the purpose of the point method mentioned in the text?
To assign a group of points to each fish's stomach based on its degree of fullness.
Why does the author mention that the work by the method of restoring original properties of food items requires a long time?
Because the author must go back to the environment to know the approximate volumes and weights of organisms that form the food of the studied fish.
How can excess water in food items be removed before determining their volume?
By blotting items on filter paper.
What is the advantage of using the method of estimating food volume in fish samples based on the total volume of all stomach contents?
It is eminently suited in the estimation of the food of carnivorous fishes.
What is the difference between wet weight and dry weight estimation of food in fish stomachs?
Wet weight is more convenient while dry weight is more time-consuming but gives a lower error margin.
Why is dry weight estimation preferred for determining the calorific intake of fish?
Dry weight estimation provides a lower error margin in bulk determination of food.
What is the major source of error in weight measurements when determining food content in fish stomachs using wet weight estimation?
The variation in the amount of moisture removed from prey items.
What advantage does the gravimetric method have when estimating food content in fish stomachs?
It is applicable to almost all prey items.
What is the main disadvantage of the volumetric method when assessing food volume in fish stomachs?
It overemphasizes the contribution of single heavy items to the diet.
Which method is considered the most accurate for assessing the volume of food items in fish stomachs?
The displacement method.
What is the numerical method used in studying fish food habits?
Numerical method: recording the number of individuals in each food category for each gut and expressing it as a proportion of the total individuals.
Why is the numerical method not suitable for dealing with food items like macroalgae and detritus?
This method is not suitable for dealing with macroalgae and detritus because they do not occur in discrete units.
What is the frequency of occurrence method used for in studying fish food habits?
The frequency of occurrence method is used to determine the prevalence of food items by expressing the number of stomachs in which each food item occurs as a percentage of the total stomachs examined.
What is a limitation of the frequency of occurrence method?
The frequency of occurrence method neglects the quantitative side of food habits.
Why is it difficult to estimate the number of food items in each category using the numerical method for some stomachs?
It is difficult to estimate the number of food items in each category in some stomachs due to mastication of the food, especially in cyprinids fish.
When is the numerical method particularly appropriate in studying fish food habits?
The numerical method is particularly appropriate when prey items of different species are in the same size range, such as in piscivorous fishes or planktonivorous fishes.
Explore methods used in ecology studies to cover different months and seasons, including the numerical method for analyzing the number of individuals in each food category. Learn how to arrange food items by number, express proportions, and assess the importance of each food source.
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