Laboratory constraints on feeding behaviours in polymorphic bluegill sunfish (Lepomis macrochirus)

Abstract

Evaluating fish feeding behaviours is imperative to understanding prey resource use in the field. Previous work on fish feeding has taken place almost exclusively in a laboratory setting, which may impose artificial restrictions. Thus, we aimed to evaluate the constraints the captive setting places on fish feeding behaviours. We recorded polymorphic (littoral and pelagic) bluegill sunfish (Lepomis macrochirus) feeding in the laboratory and the field using a high‐speed camera and underwater cameras. Following successful strikes video events, were digitised using ImageJ (laboratory) and Argus (field). Gape velocity, ram velocity, and body deceleration were higher in the field than in captive fish. Significantly greater gape velocity in field fish suggests that these fish feed with greater suction pressure than captive fish. Prey effects were detected, as brine shrimp feeding events were characterised by slower gape and ram velocities and a smaller gape. Feeding events on brine shrimp in the field were similar to feeding events on worms in the laboratory suggesting an artefact of training. These results indicate that feeding behaviours measured in the laboratory may not be representative of feeding behaviours in the wild. Further consideration of organismal performance and laboratory constraints should be taken in future functional studies.

Feeding below the thermocline: implications for prey capture kinematics

“…Both of these species were observed above the thermocline in Lake Waban when collecting data for other work (CJ Moran, pers comm). However, when collecting field feeding data for Moran et al ., (2019) we observed numerous individuals of both largemouth bass and yellow perch (seeVideo ) moving below the thermocline to forage. This suggests that a number of species, while preferring warmer (above thermocline) conditions for routine activities, will venture below the thermocline to feed.…”

“…In this video bluegills in the wild were presented a cloud of defrosted brine shrimp which elicited this behavior. The video was taken from Lake Waban for Moran et al ., (2019). The video was recorded at 240 fps.…”

“…During feeding trials, some individuals would enter the prey patch and exhibit predatory behaviors in close succession (henceforth: successive feeding) (see Video ). While this behavior was infrequent in the laboratory setting, it was commonly seen in the wild when collecting data for Moran et al ., (2019) (see Video ). Additionally, we have not seen this mentioned in the literature.…”

“…Commonly found in freshwater systems of North America, members of the Centrarchidae are of particular interest to those studying feeding kinematics (Wainwright, 1996; Carroll et al ., 2004; Higham, Day & Wainwright, 2005; Higham, Day & Wainwright, 2006; Kane & Higham, 2014; Moran et al ., 2018; Moran et al ., 2019). Prey capture behaviors within the family range from primarily ram feeding (largemouth bass, Norton & Brainerd, 1993) to primarily suction feeding (bluegill sunfish, Higham et al ., 2006).…”