. Bulletin. Science. SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 45 40. Planktonic Resources Benthic Resources Consumed 2 3 4 Size Class (mm) Fig. 2. Comparative size frequency (%) distributions of prey consumed by 40 killifish collected in October 1995 (N = 2097 prey) relative to prey available from the water column (N = 80740) and substratum (N = 1326). Benthic prey resources distributed in amounts less than 1% among size intervals from 6 to mm are not displayed. Discussion Our results corroborate earlier descriptions of Fundulus parvipinnis as lower level microcarnivores that primarily con
. Bulletin. Science. SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 45 40. Planktonic Resources Benthic Resources Consumed 2 3 4 Size Class (mm) Fig. 2. Comparative size frequency (%) distributions of prey consumed by 40 killifish collected in October 1995 (N = 2097 prey) relative to prey available from the water column (N = 80740) and substratum (N = 1326). Benthic prey resources distributed in amounts less than 1% among size intervals from 6 to mm are not displayed. Discussion Our results corroborate earlier descriptions of Fundulus parvipinnis as lower level microcarnivores that primarily consume arthropods (crustaceans and insects). Like others (Fritz 1975; Allen 1980), we observed marked seasonal changes in the presence of certain prey types (most notably insects) that contributed to dietary differences between warmer (Oct.) and colder (March) months. Yet, even within constraints imposed by the seasonal presence of certain prey types, the distinctive temporal changes we observed in the types of prey consumed by different size classes of fish signaled an age related shift in foraging habitat. Ontogenetic shifts in diet and foraging habitats are common among fishes (Kai- ser and Hughes 1993) and are likely to play a significant role in patterns of dietary choice by Fundulus parvipinnis. Although Fritz (1975) was unable to discern any differences in diets or foraging habitats of killifish with age or season, our results, like those of Allen (1980), indicate that juvenile killifish feed primarily on small planktonic harpacticoid copepods and gradually shift to larger benthic prey as they mature. Whether these ontogenetic shifts in diet are related to morphological changes in mouth size and/or changes in feeding behaviors remains to be deter- mined. However, the ability of juvenile fish to consume relatively large insects indicate that they are not morphologically constrained from handling similarly sized benthic prey. Dietary changes were coincidental with changes in
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