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Home > GCR > Vol. 17 > Iss. 1 (2005)

 

Alternate Title

Long-Term Fish Assemblage Dynamics of the Alvarado Lagoon Estuary, Veracruz, Mexico

Document Type

Article

Abstract

The fish assemblages of Alvarado Lagoon Estuary (a complex of coastal lagoons in the state of Veracruz, Mexico) have been surveyed intermittently by different researchers over the last 40 years. Assessing longterm trends in fish assemblage composition for this ecosystem is problematic due to differences in sampling efforts among the survey periods (1966–1968, 1987–1988, 1989, 1989–1990, 1990–1991 and 2000–2001) and by the inherent ecological variability of estuaries. To overcome these data limitations and better understand fish assemblage change over time, we used robust, simulation-based analyses to compare collections from the different surveys. The 107 fish species collected from the Alvarado Lagoon Estuary in these surveys represent 4 ecological guilds: marine stenohaline, marine euryhaline, estuarine, and freshwater fishes. The occurrence frequency of fish species representing each guild did not change significantly among the survey periods: the chi-square deviation statistic ( 2 = 8.53) was not significantly larger than the average value for 1000 simulated matrices ( 2 = 138.64; P = 1.00). A non-metric multidimensional scaling (MDS) based on Bray-Curtis similarities of fish species presenceabsence data showed that the 1966–1968 survey period was the least similar to the other survey periods. For the 1966–1968 survey, the range of Bray-Curtis inter-survey similarities was 40.4–58.6 (n = 5). By comparison, the remaining range of inter-survey similarities was 61.5–81.7 (n = 10). Average taxonomic distinctness (Δ+) and variation in taxonomic distinctness (Λ+), two sample size-independent measures of diversity, were calculated for all survey periods. Although Δ+ and Λ+ for all survey periods were within the simulated 95% confidence limits for expected values, these values for the 2000–2001 survey period were less than the average Δ+ and Λ+ values for the entire species pool. This suggests that the fish assemblage collected during the latest survey reflects a loss of both widespread higher taxa (reduced Δ+) and that the higher taxa lost are those with only a few representative species in the assemblage (reduced Λ+). These assemblage data show that fish assemblages of Alvarado Lagoon Estuary have not experienced significant changes over 40 years, but differences among the earliest (1966–1968), the latest (2000–2001), and the remaining survey periods indicate a recent decline in diversity.

First Page

145

Last Page

156

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