Abstract
The summer (July 2002 and 2003) larval concentrations of two commercially important clupeoid species (order: Clupeiformes), the European anchovy (Engraulis encrasicolus) and round sardinella (Sardinella aurita), were measured in Kavala Gulf (northern Aegean Sea), in order to examine their distribution patterns. Anchovy was generally most abundant, reaching 13 852 larvae 10 m−2 in 2003 and occurred in more stations compared to round sardinella. Despite the spawning of both species occurring across the entire gulf, the general spatial distribution of their larvae was different, with European anchovy larvae occupying the entire gulf and round sardinella larvae mainly concentrated at offshore stations. The reason proposed for the spatial segregation of their larvae is direct competition for resources. Yet, coexistence of the two species was observed in frontal areas with abundant food resources that prevent competition.
Highlights
Competition can be an important factor in structuring ichthyofaunal communities because it largely determines the distribution and resource partitioning of closely related species, affecting their population characteristics [1]
Clupeid larval fish and hydrographic data were collected at the northern Aegean Sea (Kavala Gulf, 24∘ 25Ε, 40∘ 52 N) across a fixed grid of 17 stations (Figure 1) in two surveys, carried out on the 2nd and 3rd of July 2002 and 2003
Kavala Gulf is a shallow gulf covering an area of 264 km2 and is located on the continental shelf of the northern Aegean Sea, which supports some of the most productive fisheries, in terms of biomass landed, in Greek waters (Greek fishing subarea 14 [23])
Summary
Competition can be an important factor in structuring ichthyofaunal communities because it largely determines the distribution and resource partitioning of closely related species, affecting their population characteristics [1]. Sympatric occurrence of closely related species utilizing the same resources may result in interspecific competition [2], which in turn may lead to one species differentiating in order to survive [3] This condition holds only when the shared resource is limited [4]. Competition avoidance through the selection of distinct habitats (in terms of depth range and distance from shore) will ensure optimal growth and survival at the vulnerable larval stages [1]. Such selective adaptations to habitats with often less favourable conditions have been reported for clupeoid fishes (order: Clupeiformes) at various life stages [13]
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