Strontium isotopes reveal ephemeral streams used for spawning and rearing by an imperilled potamodromous cyprinid Clear Lake hitch Lavinia exilicauda chi
Frederick Feyrer A D , George Whitman B , Matthew Young A and Rachel C. Johnson B C
Identification of habitats responsible for the successful production and recruitment of rare migratory species is a challenge in conservation biology. Here, a tool was developed to assess life stage linkages for the threatened potamodromous cyprinid Clear Lake hitch Lavinia exilicauda chi. Clear Lake hitch undertake migrations from Clear Lake (Lake County, CA, USA) into ephemeral tributary streams for spawning. An aqueous isoscape of strontium isotopic ratios (87Sr/86Sr) was constructed for Clear Lake and its watershed to trace natal origins and migration histories of adult recruits. Aqueous 87Sr/86Sr differentiated Clear Lake from 8 of 10 key tributaries and clustered into 5 strontium isotope groups (SIGs) with 100% classification success. Otolith 87Sr/86Sr showed all five groups contributed variably to the population. The age at which juveniles migrated from natal streams to Clear Lake ranged from 11 to 152 days (mean ± s.d., 43 ± 34 days) and was positively associated with the permanency of natal habitat. This information can be used by resource managers to develop conservation actions for Clear Lake hitch. This study demonstrates the utility of strontium isotopes in otoliths as a tool to identify important freshwater habitats occupied over the lifespan of an individual that would otherwise be challenging or impossible to trace with other methods.A
Additional keywords : intermittent, isoscape, LA-MC-ICP-MS, laser ablation–multicollector–inductively coupled plasma–mass spectrometry, migration, potamodromy, threatened species.
Fig. 1. (a) Map of Clear Lake and streams showing sites where water (closed circles) and fish (crosses) were collected. Colours represent strontium isotope groups (SIG) based on aggregations of non-overlapping 87Sr/86Sr values given in Table 1: SIG 1, red; SIG 2, orange; SIG 3, blue; SIG 4, purple; SIG 5, green. Readers are referred to Table 1 for the range of 87Sr/86Sr values corresponding to each SIG. Inset, map of the counties of California with Lake County highlighted as the filled polygon. (b) Geological map showing the primary rock types in the Clear Lake watershed.