Interpreting Early Species Range Descriptions for Pacific Salmon, Oncorhynchus spp., in Coastal California Watersheds: The Historical Context

Abstract

Scientists and managers implementing endangered species laws often face the task of defining the historical geographic ranges for threatened and endangered species. To do so, they commonly turn to the writings of early biologists seeking accounts of species in regions where they may have been extirpated as a result of anthropogenic activities over the last 150–175 years. In the case of Pacific salmon, Oncorhynchus spp., the writings of David Starr Jordan, Charles Henry Gilbert, John Otterbein Snyder, and other faculty and staff at Stanford University during the late 1800’s and early 1900’s have been particularly influential, as these scientists were widely recognized as the leading authorities on west coast fishes and salmonids in particular. Because of the tremendous achievements of these pioneering ichthyologists, scientists and others have often taken these early range descriptions at face value, without critically examining the underlying historical context. When Jordan and his contemporaries first began writing about the ranges of Pacific salmon, scientific exploration of coastal watersheds of California was in its infancy. Additionally, the taxonomy and nomenclature of Pacific salmonids were in states of extreme disarray, with numerous putative species described based on variations due to age, sex, and reproductive condition. Even after Jordan and Gilbert began to resolve Pacific salmon taxonomy in the 1880’s, confusion in nomenclature, exacerbated by a primitive understanding of Pacific salmon life histories, contributed to frequent misidentification of west coast salmonids and hence inaccurate descriptions of their historical freshwater spawning rangtablished viability criteria for each listed DPS or ESU, and development of recovery plans for these listed units. Likewise, historical information on the freshwater distribution of Pacific salmon influenced delineation of essential fish habitat under the Magnuson Act (PFMC, 1999). Misidentification of historical salmonid habitats can have important ramifications. On one hand, failure to accurately identify a portion of a species’ natural range could result in underestimation of habitat loss and lead to inadequate protection of habitats that may be important to the longterm recovery, persistence, evolution, or sustained production of an ESU or DPS. Conversely, incorrectly concluding that a species occupied a watershed or region when it did not could lead to costly recovery efforts and restrictions on human activities in watersheds where the likelihood of naturally sustaining populations is negligible. Consequently, assessing the historical es. Further confounding interpretation of early reports is that the first systematic explorations of coastal watersheds took place well after significant anthropogenic damage to salmon habitats had already occurred; thus, failure to detect species on these surveys does not necessarily indicate a species was absent, either at the time of the survey or in the years prior to significant human disturbances. As a result, any single writing of Jordan’s and his colleagues between the late 1870’s and the early 1900’s is likely to contain species range information that is equivocal, if not demonstrably inaccurate. This is not to disparage Jordan and his contemporaries in any way or to diminish their extraordinary scientific achievements. However, scientists and managers need to be cognizant of these limitations when using historical writings to guide management of endangered species. range of species should be done with considerable care. In seeking to define the natural freshwater ranges of Pacific salmon, scientists and managers have often turned to writings and collection records of pioneering ichthyologists to substantiate the historical occurrence in particular regions or watersheds. These early descriptions and accounts are generally assumed to provide evidence of occurrence during periods when the impacts of harvest and habitat degradation were less pervasive. For salmon in California, the writings of David Starr Jordan, Charles Henry Gilbert, John Otterbein Snyder, and other faculty and staff at Stanford University during the late 1800’s and early 1900’s have been particularly influential (Fig. 1). These scientists, as well as collaborators such as Barton Warren Evermann (a former student of Jordan’s at Indiana University), worked closely with the United States Commission of Fish and Fisheries (U.S. Fish Com-