Ontogenetic dietary shifts and morphological correlates in striped mullet, Mugil cephalus

Abstract

SynopsisOntogenetic dietary shifts are well studied in fishes. However, these shifts are rarely correlated with habitat and morphology. This study investigates: (1) ontogenetic dietary changes in mullet; and if dietary shifts do occur (2) whether they are correlated with feeding location, feeding behavior andlor feeding morphology. Stomach contents from eight size classes, each with 25 individuals, were analyzed using a gravimetric sieve fractionation procedure, Czechanowski's Quantitative Index and cluster analysis. Core samples (5 mm deep) were also analyzed in the same manner. Morphological characters were measured to detect differences among the size classes. Cluster analysis showed three distinct trophic units for Mugil cephalus in Cross Bayou: (1) 20.0 mm standard length -30.0 mm SL; (2) 30.0 mm SL -40.0 mm SL; and (3) 40.0 mm SL -> 100 mm SL. Comparison of the gut contents to the sediment contents for each size class showed an increase in similarity as the fish grew. Mullet gut contents from fish 20-25 mm SL were only 45% similar based on the weights of the prey items to the sediment subsample prey items, while stomach contents from fish > 100 mm SL were 84% similar to the sediment subsample contents. Gill raker length and interraker spacing of four gill arches were allometric with respect to standard length. Prey particle size within size classes appeared to be more correlated with feeding behavior than gill interraker spacing because smaller particles than predicted by the interraker spacing were ingested. It is suggested that smaller fish may be browsing more selectively than larger fish which graze.

Mouth Allometry and Feeding Habits of Some Mediterranean Fishes

“…The allometric model was the dominant model describing the above-mentioned relations, since it accounted for more than 2/3 of the species examined. The same has been reported for other species (Honda 1984, Eggold and Motta 1992, Karpouzi 2001, Lukoschek and McCormick 2001, Karpouzi and Stergiou 2003, Chalkia and Bobori 2006, although other types of models have also been reported (e.g., Erzini et al 1997, Scharf et al 2000, Ward-Campbell et al 2005. The prevalence of the allometric relation could be attributed to the fact that, as fish grow in size the amount of energy required is gradually increasing.…”

Spatial segregation of two species of Mullidae (Mullus surmuletus and M. barbatus) in relation to habitat

“…Segregation of both species in relation to size has also been noted. The size differences according to depth observed among congeneric, sympatric species of teleost fishes and other zoological groups, such as in Crustacea, have been related to increases in prey size in parallel with increases in the size of the predator (Eggold & Motta 1992, Company & Sardà 1997, Labropoulou & Eleftheriou 1997, thus producing interspecific food niche segregation based on the size of the prey. However, for the genus Mullus no such relationship exists between the individual's size and that of its prey (Golani 1994, Labropoulou & Eleftheriou 1997, which means that size-prey partitioning can be discarded as a mechanism for explaining differencies in interspecific size.…”

Bioaccumulation of human pharmaceuticals in fish across habitats of a tidally influenced urban bayou

“…Therefore, when organisms migrate or routinely move across large spatial ranges, isotope signatures are affected by both sampling area and conditions of other locations visited. For example, in the present study, M. curema and M. cephalus [24] are considered migratory species, which move within and among estuaries periodically with daily tides for feeding and reproduction. However, the present study included sampling at only 1 location in Buffalo Bayou, which was tidally influenced.…”