MEPS 208:229-248 (2000)  -  doi:10.3354/meps208229

Predator size-prey size relationships of marine fish predators: interspecific variation and effects of ontogeny and body size on trophic-niche breadth

Frederick S. Scharf1,*, Francis Juanes2, Rodney A. Rountree3,**

1Department of Natural Resources Conservation, University of Massachusetts, Amherst, Massachusetts 01003, USA
2Department of Natural Resources Conservation and Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA
3NOAA/NMFS/NEFSC, Woods Hole Marine Laboratory, 166 Water St., Woods Hole, Massachusetts 02543, USA
Present addresses: *NOAA/NMFS/NEFSC, James J. Howard Marine Laboratory, 74 Magruder Rd., Highlands, New Jersey 07732, USA. E-mail: **Department of Natural Resources Conservation, University of Massachusetts, Amherst, Massachusetts 01003, USA

ABSTRACT: We utilized a long-term data base collected over a broad geographic range to examine predator size-prey size relationships for 18 species of marine fish predators from continental shelf waters off the northeast US coast. Regression analysis was used to illustrate interspecific variation in ontogenetic patterns of prey size use, gape allometries, and ratio-based trophic niche breadths. Size-based feeding strategies were assessed through comparison of frequency distributions of relative prey sizes eaten and were related to general predator feeding tactics and gape morphology. The results demonstrated that the range of prey sizes eaten expanded with increasing predator body size for each of the marine predators examined, leading to asymmetric predator size-prey size distributions. Absolute maximum prey size and slopes of maximum prey size versus predator size varied widely among predator taxa. Distinct size-based feeding strategies were evident, as diets of some predators were dominated by prey that were 10 to 20% of predator size, whereas other predators frequently consumed prey >50% of predator size. Gape sizes and allometric relationships with body size were also diverse among predators and often were closely associated with maximum prey sizes. Ratio-based trophic-niche breadths generally did not expand with predator ontogeny and tended to narrow for the largest predators, which may be common for animal taxa.

KEY WORDS: Predator-prey · Body size · Piscivorous fish · Trophic niche · Gape size

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