Spatial and temporal variation of the ichthyoplankton in the Laguna El Quelele, Nayarit, Mexico

Abstract

Estuarine systems are the most important natural aquatic resources because, from the perspective of the fish community, they include a large number of individuals and biomass, where larvae and juveniles are especially abundant. Thanks to the implementation of Ichthyoplanktonic studies, the areas of concentration of adults in reproductive stage and potentially exploitable species are detected and evaluated, generating the basis for establishing measures for rational use and conservation. This paper analyzes the composition of fish larvae in the lagoon El Quelele in Bahia de Banderas, Nayarit. 20 daytime superficial zooplanktonic trawls were conducted by using a standard “Zeppelin” net seasonally from spring to winter 2002. From the 20 samples obtained, larvae density was 573.51 org/1000 m3. Its ichthyoplanktonic group was represented by 11 families with 12 genres and 10 species, where Engraulis mordax (40.21 %), Eucinostomus sp. (22.68 %), Trachurus sp. (15.46 %) and Dormitator latifrons (13.14 %) presented greater percentage of relative abundance, while in the rest of the organisms, relative abundance was represented between 7.47 to 0.25 %. Regarding temporal variation, the highest relative abundance was presented in fall with 44.74 and the lowest during the winter with 4.85 %, with moderate average temperature records of 29.1 and 30.8 °C respectively, and low salinity (24.2 psu). While spatial variation was better represented in site 3 with relative abundance 29.41 % and site 4 with the lower value during the study period (9.2 %) at temperatures ranging from 22 °C to 35 °C and salinity of 24 psu to 34 psu. On the other hand, in spring and fall they showed greater diversity, greater richness and therefore these are the seasons with greatest equity in summer and winter. Cluster analysis applied to the species-variable sampling sites showed greater similarity or affinity between sites 3 ​​and 5 (72.2 %), similarly, variables season – species along the year showed affinity of 60.52 % between spring and fall, while in summer and winter they showed no affinity with the rest of the seasons. The spatial and temporary variations in temperature, salinity and abundance of ichthyoplankton indicate that larvae abundance is strongly related with the seasonal influence pattern which has influenced, at the same time, in the reproductive cycle of these species.