Effects of urbanization on assemblage structure of estuarine fish larvae and juveniles: A case study of Gongsitian Stream in north Taiwan
Date Issued
2015
Date
2015
Author(s)
Xu, Xin
Abstract
Estuaries own high productivity, and function as critical habitat, foraging site and nursery ground for fishes and other creatures. Many changes have taken place to the estuary landscape due to urbanization, thus bring disturbance to the rivers and the local living creatures. The Danhai New Town Project, a government permitted urban development, started in 1994. Since then, many changes to the landscape have been witnessed in the nearby estuary of Gongsitian Stream. To understand the correlation between the urbanization project and the assemblage structure of estuary fish larvae and juveniles in the estuary, species richness, diversity and composition of estuary fish larvae and juveniles were compared during the period in 1984-1985, 1997-1998 and 2004-2005. Species are divided into different habitat functional guild; seasonal changes of the proportion of different guilds are compared in and between these years. Besides, we compared satellite images of different years to illustrate the changes of urbanization area and present the landscape transformation from natural to artificial before and during the urbanization project. The analysis of the satellite images reflect that the urbanization area gradually increased since 1994, a land reclaiming happened during 1995-2001, and the construction of buildings and roads took place after 1997. The three samplings on fish larvae and juveniles during the 20 years showed similar seasonal pattern, but the total individual number decreased with time (from 6802 to 15467 to 3041, individual/hour). The number of fish species (and families) has a little decrease from 86 species (40 families) in 1984-1985 to 39 species (21 families) in 2004-2005. The species number changes seasonally in all year periods but with a similar trend that increases in spring and falls after summer. The significant differences (p<0.05) of the richness and diversity indexes of the 3 years reflect the total loss on assemblage richness and diversity. A similarity test reveals that the species compositions in the 3 years have little in common, which indicates a phase transition during the 20 years. Six habitat functional guilds of fishes can be found, but the dominant guild changed from estuarine to coastal water fish in 1984-1985 to diadromous and sand-mud fish in 2004-2005. The losses of richness and diversity on the fish larvae and juveniles in Gongsitian Stream estuary reflect a deterioration of the estuary area. There are many reasons could be responsible for the pattern. Based on the transformation of dominant habitat guild, it suggests that the urbanized landscape changes, including land clearing, construction of buildings and roads, land reclamation and stream channel transformation, bring enough disturbances to the natural stream estuary. These changes the fish assemblage in Gongsitian Stream estuary.
Subjects
Danhai New Town Project
urbanization
fish larvae and juvenile
fish assemblage
Gongsitian Stream estuary
Type
thesis
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