By combining these disparate datasets, conclusions are strengthened through weight of evidence. Chemical archives, such as eye lenses, preserve information regarding several life stages for each individual.
#Fish net eye lens series#
Most fishery datasets, such as catch records, length frequencies, and stomach contents, create a series of snapshots, with each captured fish representing a single timepoint during the lifespan. Many predatory marine fishes undergo ontogenetic diet and habitat shifts as they grow. Such information would have immediate application towards conservation management of diverse species and habitats at multiple scales. SIA in eye lenses using three dietary isotopes (δ13C, δ15N, and δ34S), has significant potential for answering critical questions about migration, diet, foraging ecology, and life‐history of migratory aquatic animals on Earth. We then successfully applied the method to a larger, reproductively mature adult salmon captured in freshwater and inferred juvenile habitat use. Slight additional isotopic fractionation was only found in δ13C. Bulk eye‐lens stable isotope measurements were analyzed for juvenile salmon lenses and were found to be consistent with the isotopic values of rearing habitats. This experimental approach allowed us to directly measure diets and quantify tissue turnover rates in eye lenses as well as the isotopic fractionation among fish tissues (fin and muscle tissue) in distinct habitat types using stable isotopes δ13C, δ15N, δ34S. We placed juvenile Chinook Salmon (Oncorhynchus tshawytscha) in experimental enclosures in three different freshwater habitats (hatchery, river, and seasonal floodplain), each with isotopically distinct and well‐characterized food webs. To date, no studies have examined freshwater taxa nor used δ34S isotopes. Currently, studies using fish eye lenses to study SIA in diets have primarily been conducted in marine environments using δ13C and δ15N to identify resource partitioning, ontogenetic shifts, and lifelong trophic histories. Stable isotope analysis (SIA) in consecutive laminae in eye lenses, a protein‐rich depositional tissue, has emerged as a promising tool in fishes to develop long‐term interpretive records of dietary histories using a single archival tissue.
Yet conventional animal tracking often precludes tracking small juveniles at critical life‐stages where recruitment bottlenecks often manifest. Tracking habitat use and dietary shifts in migratory species is vital to conservation and management.
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