Use of archaeological data in retracing diet and growth of extirpated fish populations in the California Delta: An allometric and isotopic approach to Sacramento perch (Archoplites interruptus) historical ecology

Abstract Sacramento perch (Archoplites interruptus), ubiquitous in the archaeological record throughout Central California, is now extirpated from the California Delta. Descriptions of Sacramento perch ecology, biology, and behaviour are either from relocated or declining populations. Archaeological specimens have the potential to provide insight on Sacramento perch demographics and feeding behaviour in their native range prior to large scale damming and the introduction of invasive species. We develop regression formulae to predict live length for three skeletal elements (vomer, dentary, and atlas). Formulae were applied to archaeological specimens (n = 182) from CA-CCO-647 (cal CE 1230–1440), Contra Costa County, California. Archaeological samples were then compared to length data from six contemporary relocated populations. Bulk collagen samples of specimens of varying lengths (n = 12) were run for δ13C and δ15N. Archaeological specimens averaged 196 mm in standard length, and attained longer average and maximum lengths than relocated perch populations. Length distributions showed a high proportion of newly sexually mature individuals, suggesting that Sacramento perch were targeted while spawning nearshore. Nitrogen values correlated positively with standard length, suggesting that within the California Delta, Sacramento perch feeding behaviour changed as individuals grew, likely marking a shift to more piscivorous diets with age. Data highlight the potential of archaeological assemblages in reconstructing past length distributions and feeding behaviour for extirpated fish populations in their endemic ranges.