Ichthyoplankton assemblage structure of springs in the Yangtze Estuary revealed by biological and environmental visions

Abstract

The ichthyoplankton assemblage structure in the Yangtze Estuary was analyzed based on four springs in 1999, 2001, 2004 and 2007 in order to provide detailed characterizations of the ichthyoplankton assemblage in springs, examine the long-term dynamics of spring ichthyoplankton assemblages, and evaluate the influence of environmental factors on the spatial distribution and inter-annual variations of ichthyoplankton assemblages associated with the Yangtze Estuary. Forty-two ichthyoplankton species belonging to 23 families were collected. Engraulidae was the most abundant family, including six species and comprising 67.91% of the total catch. Only four species (Coilia mystus, Engraulis japonicus, Trachidermis fasciatus and Allanetta bleekeri) could be considered dominant, accounting for 88.70% of total abundance. The structure of the ichthyoplankton spring assemblage persisted on an annual basis, with the dominant species reappearing consistently even though their abundance fluctuated from year to year. This inter-annual variation probably reflects variable environmental conditions influenced by jellyfish blooms, declining river flow, and overfishing. Canonical correspondence analysis indicated aspatial structure of the ichthyoplankton assemblage in three areas: (1) an inner assemblage dominated by C. mystus; (2) a central assemblage dominated by A. bleekeri and T. fasciatus; and (3) a shelf assemblage featuring E. japonicus. The observed ichthyoplankton assemblage structure appears to be strongly influenced by depth, salinity and suspended particulate matter gradients.

Modelling the potential impacts of climate change on the distribution of ichthyoplankton in the Yangtze Estuary, China

“…In addition to range shifts, changing climates can also affect species abundance (Barrett et al, ; Doney et al, ; Richardson, ). Declines in the abundance of ichthyoplankton have already been observed in the Yangtze Estuary (see Zhang et al, ). It is important, yet especially challenging, to accurately model species abundance (Oppel et al, ; Pearce & Boyce, ).…”

“…These species, especially C. mystus and L. polyactis , are important fisheries resources and play an important role in the food web in the Yangtze Estuary. According to previous surveys, ichthyoplankton of the five species are abundant in the Yangtze Estuary (Zhang et al, ); the early life‐history stages of these species represent prey items for a variety of species and are directly related to recruitment success and stock abundance. According to our projections, these five ichthyoplankton species in the Yangtze Estuary are likely to exhibit two different responses to future climate change; a finding that contradicts our initial hypothesis that ichthyoplankton in this region will exclusively respond to climate change by shifting their distribution northward.…”

“…Coilia mystus is an estuarine migratory and commercially important fish in the Yangtze Estuary which inhabits China's Pacific coastal waters from Hainan province to Liaoning province (He et al, ). Hypoatherina valenciennei is distributed throughout the south‐western Pacific and as far north as Japan (Ivantsoff & Kottelat, ); this species is a common and sometimes dominant species in the Yangtze Estuary (Zhang, Xian, & Liu, ). Being one of the target species of bottom trawling (Li, Shan, Jin, & Dai, ), L. polyactis is an economically important fish resource.…”

Autumn ichthyoplankton assemblage in the Yangtze Estuary shaped by environmental factors

“…Ichthyoplankton, including fish eggs, larvae and juveniles, is the basis for the sustainable utilization of fishery resources ( Miller & Kendall, 2009 ; Zhang, Xian & Liu, 2015 ), with survival directly influencing recruitment. Because of absent or weak independent swimming capabilities and a drifting nature, ichthyoplankton are poorly adapted to changing environmental conditions.…”

“…To date, investigations into ichthyoplankton communities in Yangtze Estuary have mainly concentrated on species composition, fauna distribution and seasonal variations (i.e., Yang, Wu & Sun, 1990 ), discussions on the relationship between the ichthyoplankton community and environmental factors ( Jiang, Shen & Chen, 2006 ; Liu, Xian & Liu, 2008 ), or long term dynamics of spring ichthyoplankton assemblages ( Zhang, Xian & Liu, 2015 ). Fish reproduce in the Yangtze Estuary throughout the year, and fishery resources are most abundant in autumn.…”