The Laguna Madre is a hypersaline lagoon. Despite harsh conditions, the upper
Laguna Madre (ULM) is a highly productive ecosystem and a popular sportfishing area,
especially for spotted seatrout and red drum. It is also the most important Texas bay for
commercial fishing of black drum. TPWD’s Coastal Fisheries division began
conducting routine monitoring of coastal fishery resources in 1977 to guide
management. The goal of the present study was to improve understanding of spatiotemporal
trends in relative abundance of selected fish and macro-invertebrate species in
the upper Laguna Madre. I used TPWD’s bag-seine and water-quality data from the
years 1985-2004 to examine variation in species’ relative abundances and relationships
to several environmental factors. I hypothesized that one or more of these variables,
alone or in combination, were related to spatial and temporal trends in community
composition. I used detrended correspondence analysis (DCA) to measure species
turnover (beta diversity) and to determine which model (linear or unimodal) of species
response along a gradient to apply. I used canonical correspondence analysis to relate
species abundances directly to explanatory variables. The explanatory variables were tested for significance and the variance partitioned among three groupings: temporal,
spatial and environmental.
DCA indicated complete species turnover along two dimensions: seasonal and
spatial. It also indicated that a unimodal method such as CCA was appropriate for
further analysis. The CCA model included 39 variables. The included variables
explained 14% of the variation in species abundance in the data set. Since the first four
axes explained 67% of the variation contained in the first two DCA axes, the chosen
explanatory variables were sufficient to explain the majority of the tractable variation in
species abundance. The variance partitioning procedure indicated that temporal effects
were the most important in explaining species variation in the Upper Laguna, followed
by the spatial component. The pure environmental component explained the least
amount of variation.
In this study, much of the variability in species abundance was due to the
spawning patterns of estuary-dependent species, most of which spawn in the spring and
summer months, leading to higher abundances from spring through fall.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-3087 |
| Date | 15 May 2009 |
| Creators | Larimer, Amy Beth |
| Contributors | Gelwick, Fran, Neill, William |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | electronic, application/pdf, born digital |
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