Ten species of flatfish were studied to see to what extent interspecif
ic competition influences their diet or spatial distribution and wheth
er the potential of these flatfish species to avoid interspecific comp
etition through resource partitioning is constrained by specific morph
ological characteristics. For this, seven morphological characteristic
s were measured, diet composition was determined from gut content anal
yses and overlap in distribution was determined from the co-occurrence
in trawl hauls. Canonical correspondence analysis revealed the morpho
logical characteristics that were most strongly correlated with the di
et composition. Based on these findings the mouth gape was considered
to be the most important morphological constraint affecting the choice
of food. Two resource dimensions were distinguished along which inter
specific competition can act on the flatfish assemblage: the trophic d
imension (diet composition) and the spatial dimension (distribution).
Resource partitioning was observed along both dimensions separately an
d, more importantly, the degree of resource partitioning along thr two
dimensions was negatively correlated. Especially thp latter was consi
dered strong circumstantial evidence that interspecific competition is
a major factor structuring the flatfish assemblage. Resource partitio
ning along the two resource dimensions increased with decreasing mouth
gape, suggesting that interspecific competition mainly acts on the sm
all-mouthed fish, i.e. juveniles. (C) 1998 Elsevier Science B.V. All r
ights reserved.