Nematalosa erebi also showed size-related changes in diet composition, with a clear shift from a mostly planktivorous diet (Moinidae and Calanoida) in smaller individuals (B69 mm TL) to a predominantly detritivorous diet in larger fish ( [69 mm TL). Pronounced size-related patterns in the diet of Nematalosa erebi are a known feature in the dietary ecology of this species recognized by Kennard et al. (2001) and Pusey et al. (2004) among others. Bunn et al. (2003) also noted a size-related shift in stable isotope signatures of this species, reflecting a decrease in dependence on zooplankton and a greater dependence on benthic algae and terrestrial detritus as fish grew. Even though the cutoff value for the size when this species switches from a diet based on invertebrates to a more herbivorous/ detrital diet varies, in general, individuals smaller than 70 mm TL can be expected to have higher contributions of invertebrates to their diet. This is in accordance with results presented in this study, which shows that individuals larger than 70 mm TL were mostly detritivorous. Morphological changes that occur with growth of Nematalosa erebi play a major role in the dietary shifts of this species. Kennard et al. (2001) suggested that variations in diet between juveniles and adults of Nematalosa erebi probably reflect increasing mouth size as well as shifts in foraging habitat. Moreover, Atkins (1984) found that some of the morphological correlates of dietary shifts in this species included a change in mouth positioning, from dorso-terminal to terminal in fry and juveniles (related to planktivory), to ventro-terminal in adults (related to omnivory and detritivory), as well as ontogenetic changes in gut morphology, where smaller individuals have a relatively simple, straight, and short alimentary tract and only later in life the gizzard (used to help digest detrital/plant materials) becomes muscular and functional.
Nematalosa erebi also showed size-related changes in diet composition, with a clear shift from a mostly planktivorous diet (Moinidae and Calanoida) in smaller individuals (B69 mm TL) to a predominantly detritivorous diet in larger fish ( [69 mm TL). Pronounced size-related patterns in the diet of Nematalosa erebi are a known feature in the dietary ecology of this species recognized by Kennard et al. (2001) and Pusey et al. (2004) among others. Bunn et al. (2003) also noted a size-related shift in stable isotope signatures of this species, reflecting a decrease in dependence on zooplankton and a greater dependence on benthic algae and terrestrial detritus as fish grew. Even though the cutoff value for the size when this species switches from a diet based on invertebrates to a more herbivorous/ detrital diet varies, in general, individuals smaller than 70 mm TL can be expected to have higher contributions of invertebrates to their diet. This is in accordance with results presented in this study, which shows that individuals larger than 70 mm TL were mostly detritivorous. Morphological changes that occur with growth of Nematalosa erebi play a major role in the dietary shifts of this species. Kennard et al. (2001) suggested that variations in diet between juveniles and adults of Nematalosa erebi probably reflect increasing mouth size as well as shifts in foraging habitat. Moreover, Atkins (1984) found that some of the morphological correlates of dietary shifts in this species included a change in mouth positioning, from dorso-terminal to terminal in fry and juveniles (related to planktivory), to ventro-terminal in adults (related to omnivory and detritivory), as well as ontogenetic changes in gut morphology, where smaller individuals have a relatively simple, straight, and short alimentary tract and only later in life the gizzard (used to help digest detrital/plant materials) becomes muscular and functional.
การแปล กรุณารอสักครู่..