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The inland water fishes of Africa

 | 
Didier Paugy
, 
Christian Levêque
, 
Olga Otero

Diets and food webs

Didier Paugy und Christian Levêque

Zusammenfassung

All animals use food as their sole source of energy. The search for food is thus a key activity for fishes, which devote a significant portion to their time to this quest, and perhaps even the bulk of their activities.
A major problem for fish is deciding when and where to feed, for how long, identifying the most suitable prey (in terms of size and nutritional value), and finding and capturing such prey. That is the reason why some view feeding strategies as decision-making systems (Cézilly et al., 1991). A fundamental axiom is that such strategies were shaped during natural selection, and that any decision tends to optimize variables such as the rate of energy assimilation, which is correlated with the concept of “fitness” (Pyke, 1984). Thus, given the different options available in their natural environment, animals do not choose their food at random. On the contrary, they carry out activities that provide the highest reproductive success (Pulliam, 1989). As a corollary, food research strategies are adaptations that allow fishes to address, as efficiently as possible, different environmental constraints such as competition, food scarcity, and unpredictable variations in resources.
Some results also suggest that fishes have the capacity to learn and use alternative behaviours that allow them to be more efficient in finding prey, and therefore live longer (Hart, 1986).

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Diets and trophic groups

Characterizing a fish’s diet requires a qualitative and quantitative description of prey found in its stomach. The simplest assessment method is noting the presence or absence of a type of prey in stomachs. The data is then used to calculate the percentage of occurrence which is the ratio of the number of stomachs in which one type of prey is found with the total number of stomachs studied.

Comparative advantages of the methods used for the analysis of stomach contents

Methods

Advantages

Failures

Occurrence

simple, easy, quick

rudimentary does not take into account the volume and the relative abundance of prey

Numerical

simple, quick

does not take into account the volume of each prey
small-sized prey digested more quickly than large-sized prey
difficulty of counting prey during digestion

Volumetric

determines the respective volume of each type of prey gives the most representative picture of the diet

difficult and long to implement
difficulty to separate taxa after ingestion...

Autoren

Research director at IRD. He has published numerous works on the systematics, distribution, and ecology of West African fresh water fishes, and expanded the collections of the MNHN in Paris.

Research director at IRD. He has published numerous works on the systematics, distribution, and ecology of West African fresh water fishes, and expanded the collections of the MNHN in Paris.

© IRD Éditions, 2017

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