Distribution and segregation of two sympatric Brevoortia species (Teleostei : Clupeidae)

The authors described and analysed the temporal and spatial distribution an d segregation patterns of Brevoortia patronus and B. gunteri, in a coastal lagoon of Veracruz, Mexico. A total of 394 individuals of B. gunteri (mean SL of 61.7 mm) and 378 of B. patronus (mean SL of 128.0) were collected, in 189 monthly and 48 diel (24-h cycles) samples. Both species showed two cat chability peaks-one during March-May (dry season) and the second in July-Oc tober (rainy season)-and these peaks were related with the two primary prod uction pulses in the system. These patterns were slightly different for eac h species, the first peak being more important for B. gunteri (68.6%), and the second for B. patronus (78.2%). Brevoortia patronus number was correlat ed with rainfall (P<0.01), and the relative abundance of both species was c orrelated with salinity (P<0.05). In 24-h cycle analysis, the two species w ere more abundant around midday (10:00 to 14:00 h), with few individuals ca ptured during the night, and this behaviour was probably related to light i ntensity and their trophic activities. Moreover, no diel separation between species was observed. Spatially, B. gunteri was principally captured (67.4 %) in sites with higher salinities and with no submerged vegetation, and B. patronus was mainly captured (70.9%) in sites with low salinity and with d ense beds of Ruppia maritima. Thus, the authors consider salinity as an imp ortant factor in the seasonal and spatial segregation of Brevoortia species , with B. gunteri common in periods and zones with higher salinity and B. p atronus in periods and areas of low salinity. The results presented here su ggest that these segregation patterns permit resource partitioning between these species and facilitate their local co-existence. (C) 2000 Academic Pr ess.