Prey acceptance and feeding kinematics in native and non-native fishes from Colorado River tributaries, or “My what a big mouth you have”


Meeting Abstract

32.4  Tuesday, Jan. 5  Prey acceptance and feeding kinematics in native and non-native fishes from Colorado River tributaries, or “My what a big mouth you have!” GIBB, A.C.; ARENA, A.*; Northern Arizona University; Northern Arizona University alice.gibb@nau.edu

The American Southwest is home to a diverse fish fauna that has been imperiled by the introduction of non-native species. We examined native and non-native fish occupying two trophic guilds in Colorado River tributaries: top predators, roundtail chub (Gila robusta) and smallmouth bass (Micropterus dolomieu), and benthic omnivores, Sonora sucker (Catostomus insignis) and common carp (Cyprinus carpio). Fish were presented with six ecologically-relevant prey types to assess prey acceptance, quantify feeding movements, and address the following specific questions. Do species at the same trophic level consume the same array of food items? Do species capture different food items via similar or distinct feeding behaviors? From our laboratory studies, several patterns emerge. (1) Natives consume a broader array of food items, relative to non-natives. (2) Species at a given trophic level demonstrate similar feeding behaviors: for example, roundtail chub and smallmouth bass bite and tear benthic attached prey using their jaws, but immediately engulf midwater prey into the buccal cavity. (3) Three of four species modulate mouth gape in response to different prey items; Sonora sucker, however, show an “inflexible” feeding behavior, whereby gape and other kinematic variables are not modified in response to different food types. (4) Non-native species consistently produce a larger gape then their native counterparts, and gape is a function of cranial morphology. This last finding has two significant ecological ramifications: (a) prey items included in the diet of non-natives may be excluded from the diet of natives because they are too large and (b) non-natives may be able to consume similarly-sized native fish, while the converse is highly unlikely.

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