Distribution and Segregation of Two Sympatric Brevoortia Species (Teleostei: Clupeidae)

Abstract

The authors described and analysed the temporal and spatial distribution and segregation patterns ofBrevoortia patronus and B. gunteri, in a coastal lagoon of Veracruz, Mexico. A total of 394 individuals of B. gunteri (mean SL of 61·7mm) 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 catchability peaks—one during March–May (dry season) and the second in July–October (rainy season)—and these peaks were related with the two primary production pulses in the system. These patterns were slightly different for each species, the first peak being more important for B. gunteri (68·6%), and the second for B. patronus (78·2%). Brevoortia patronus number was correlated with rainfall (P<0·01), and the relative abundance of both species was correlated with salinity (P<0·05). In 24-h cycle analysis, the two species were more abundant around midday (10:00 to 14:00h), with few individuals captured during the night, and this behaviour was probably related to light intensity 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 dense beds of Ruppia maritima. Thus, the authors consider salinity as an important factor in the seasonal and spatial segregation of Brevoortia species, with B. gunteri common in periods and zones with higher salinity and B. patronus in periods and areas of low salinity. The results presented here suggest that these segregation patterns permit resource partitioning between these species and facilitate their local co-existence.