Temporal space-variation of fish larvae in the Gulf of Guayaquil, Ecuador

Abstract

This study presents the density, taxonomic composition, spatial and temporal distribution of fish larvae in the Gulf of Guayaquil, as well as the relationship with some physical-chemical variables. Samples were collected at 16 stations, taken in the first nautical mile of the external and internal estuary of the gulf, located in front of the province of Guayas and northwest of the island of Puná, during June to December 2012. Surface trawls were carried out with a simple conical network (mesh eye: 300 µm; mouth diameter: 0.3 m; length: 1.2 m). Temperature, salinity, and transparency were measured before each drag. Significant differences were detected between zones, registering higher temperatures, lower salinity, and transparency in the interior estuary. 321 638 ind/100m3 of fish larvae were collected, belonging to 13 families and 36 species between the external and internal zone. Engraulidae (58.9 %) was the most abundant family in the exterior estuary stations, followed by Sciaenidae (22.8 %) and Haemulidae (9.6 %). Most frequent families in the interior estuary were Engraulidae (74.4 %) and Gobiidae (16.1 %). 85 % of the total density was contributed by five species, of which Anchoa sp. and Bairdiella sp. were the most abundant and dominant, mainly during December. Structure and composition of the larval community were significantly different between areas (MW-U = 450; p < 0.05) and months of sampling (KW = 14.24; p < 0.05), with higher records in the exterior estuary during December. With the redundancy analysis (ADR) it is observed that in the exterior area, the species were associated with the transparency of the water, while the species that concurred in the interior zone were positively related to salinity. In general terms, the abundance and richness of fish larvae in the external area of the Gulf of Guayaquil is related to the conditions of transparency and local salinity, which favored the larval presence.