Ichthyoplankton dynamics in a highly urbanized estuary

Abstract

Spatio-temporal distribution and composition of ichthyoplankton assemblages were studied in the Golden Horn estuary (Istanbul) over a 10-month period. Environmental parameters were considered to determine the environmental status in different parts (upper, middle and lower) of the estuary. The ichthyoplankton composition of the Golden Horn estuary consisted of 23 species and was dominated by Mullus sp., Diplodus spp. and Liza sp. The largest densities of fish eggs and larvae were found in September 2009 with 786.4 ind. 100 m^–3 and 355.9 ind. 100 m⁻³, respectively. As supported by the multivariate analysis, most species showed a seasonal pattern, with the presence of higher densities during summer and winter. Moreover, the spatial pattern showed that ichthyoplankton distribution and diversity was relatively high in the lower part of the Golden Horn and gradually decreased through the upper parts. Canonical correspondence analysis revealed that spatial changes in depth and water clarity were the main factors forcing larval assemblage distribution and leading to a decrease in density and diversity of fish larvae through the upper part of the estuary. For the seasonal changes, sea surface salinity and chlorophyll a were the main factors in shaping the structure of the larval assemblage and increasing sea surface temperature lead to an increase in the density and diversity of fish larvae.

Key words:

• Early life stages
• environmental factors
• Golden Horn estuary
• larval assemblage
• nursery
• urbanization

Acknowledgments

I would like to thank Dr Aslı Aslan, subject editor Dr David McKinnon and two anonymous reviewers for their valuable recommendations that improved this manuscript. Dr Nuray Balkıs, Dr Seyfettin Taş, Dr Ahsen Yüksek, and Dr Hüsne Altıok kindly shared the physical and biochemical data. I am especially grateful to the Captain of R/V Arar2, Remzi Hendem, and the crew for their excellent support during the sampling campaigns.

Additional information

Funding

This study was funded by the Scientific and Technological Research Council of Turkey (TUBITAK). It was conducted as part of the Water Quality Monitoring Project funded by the General Directorate of Istanbul Water and Sewerage Administration.