Ontogenetic diet shifts of age‐0 smallmouth bass (Micropterus dolomieu Lacepède) in the New River, West Virginia, USA

Abstract

Larval and juvenile smallmouth bass (Micropterus dolomieu Lacepède; 8.5–85.0 mm total length (TL)) were collected from 2 sites in the New River, West Virginia, in the late spring and early summer to document diet shifts during early ontogeny. The first foods of smallmouth bass (TL = 9 mm) were primarily Chironomidae and microcrustaceans (primarily Copepoda). Other aquatic insects, primarily Ephemeroptera, became more abundant in the stomachs as TL increased. A shift in the proportions and types of prey consumed began at approximately 15 mm TL and was primarily attributed to fin development and increased mouth size. Foraging success, measured by number of prey per stomach, stomach fullness, and average prey volume was lower for first‐feeding smallmouth bass than for later life stages. Mouth width appeared to restrict the size of prey consumed by larval smallmouth bass, but the maximum prey width never approached the mouth width for fish longer than 35 mm TL.

Spring diet composition of Rainbow Trout, Oncorhynchus mykiss (Walbaum, 1792) in the Urederra River (Spain)

“…This could be the explanation why smaller trout use prey not available to older trout (Jonsson & Gravem 1985). Likewise, Mollusca and fishes were only used by older trout because their bigger size requires a bigger mouth size, and a greater swimming ability in the case of fish predation (Easton & Orth 1992, Keeley & Grant 1997. This also allows older trout to have a bigger number of potential preys.…”

Effect of stream microhabitat characteristics on rate of net energy gain by juvenile smallmouth bass, Micropterus dolomieu

“…Juvenile smallmouth bass between 30-90 mm TL consume the same size-range of prey (Easton & Orth 1992). We estimated length of all juveniles to determine if the same size-range of prey were available to all juveniles.…”

“…This microhabitat shift occurs 6-8 weeks after larvae leave the nest and after they have grown larger than 30 mm in total length. At this size they are less likely to be displaced by high water velocities (Larimore 1975) and are capable of consuming a wide sizerange of invertebrate prey (Easton & Orth 1992). Therefore, this microhabitat shift can be interpreted as that of a habitat specialist (restricted to areas containing low water velocities and small prey) that becomes a generalist by entering areas it was previously excluded from.…”

The Early Life History of the Guadalupe Bass: Lessons for Culturing a Threatened Species

“…Swim bladder inflation then follows 24 h later. The swimming ability of centrarchid fry improves with fin development (Clark and Mancini ; Easton and Orth ). The above developments may represent the minima required to sustain swim‐up.…”