30-10 Stable isotopes analysis vs. TROPH: A comparison of methods for estimating trophic positions of fish in a subtropical estuarine system

Wednesday, September 15, 2010: 11:40 AM
303 (Convention Center)
Felipe Amezcua, PhD , Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Mazatlán, Mexico
Martin Soto, PhD , Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Mazatlán, Mexico
Juan Madrid, PhD , Centro Regional de Investigaciones Pesqueras de Mazatlán, Instituto Nacional de Pesca, Mazatlan, Mexico
An ecosystem-based management of fisheries requires a proper estimation of the trophic position (TP) of each component of the food web. Stable isotope analysis (SIA) and stomach contents analysis (SCA) are used to estimate TP of aquatic systems, but few studies have compared the results obtained from both methods. We used SIA (d15N) and SCA (TrophLab) to estimate the trophic position (TP) of 75 fish species from an estuarine system in the Gulf of California, and to compare TP estimates between methods. TPSIA ranged from 2.6 to 5.6, and most of the analyzed species showed TP from 4.5 to 5. TPSCA ranged from 2.5 to 4.5 and most of the species showed TP from 3.5 to 3.75. It was determined that TrophLab underestimates the TP, mainly in piscivorous fishes because the TP default for the consumed fish preys is always 3.5. However, it was observed that when the TROPH of a species was estimated from a known TP of its prey, other than the TrophLab defaults, the yielded results of the TPSCA were similar to the results of TPSIA. TPSIA gives more accurate results, but the TPSCA can give adequate results if the TP of the prey items is known.
See more of: Trophic Ecology I
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