Variability in fish size/otolith radius relationships among populations of Chinook salmon

Abstract

Back-calculation of growth trajectories from otolith microstructure is a valuable tool for understanding mechanisms underlying variability in growth among fish populations. We analyzed fish length/otolith radius relationships for Snake River spring/summer Chinook and Snake River fall Chinook salmon, listed as separate "Evolutionarily Significant Units" (ESUs) under the US Endangered Species Act, to determine whether these ESUs shared relationships. In addition, we analyzed otoliths from seven separate populations within the Snake River spring/summer Chinook ESU to assess the variability in relationships among populations, which are much more closely related than ESUs. We also examined several potential functional forms for the equations. We found that the separate ESUs had significantly different fish length/otolith radius relationships, but that variability in otolith growth rate could not explain the difference. Relationships among populations within the spring/summer Chinook ESU did not vary nearly as much as those between ESUs. The quadratic model and the power model fit the data equally well, and constraining these models to pass through a biological intercept (estimated fish length and otolith radius at hatching) resulted in only a slight decrease in model fit. To test the ability of the models to backcalculate fish lengths, we predicted the length at tagging for 17 PIT-tagged fall Chinook that were measured at release and at recapture. The backcalculation demonstrated little bias (<1 mm FL, on average) and relatively small standard deviation (∼3.5 mm) for the best model. When we repeated the back-calculation with data from both ESUs combined, bias increased substantially (to 15 mm FL), demonstrating the importance of determining the proper taxonomic level at which to combine data within a species.

Assessing estuaries as stopover habitats for juvenile Pacific salmon

“…Hard structures such as scales or otoliths can provide insight into reconstructed movement patterns (Volk et al 2010, Brennan et al 2015, Claiborne & Campbell 2016. Perhaps due to different environmental conditions, different populations of salmon can have different otolith growth patterns (Zabel et al 2010), and laboratory studies have found that time estimates based on otoliths are fairly accurate and precise (Freshwater et al 2015, Claiborne & Campbell 2016. Here we used a complementary approach -the application of known turnover rates of tissues and stable isotopes as clocks.…”

Validation of Daily Increment Formation in Otoliths from Spring Chinook Salmon

“…Volk et al (2010), on the other hand, conducted a mark-recapture study to investigate the periodicity of otolith increment formation. For our study, confirmation of an emergence check and of daily increment formation grew out of our need to better understand early life history development (Zabel and Achord 2004), growth (Achord et al 2007, Zabel et al 2010, and habitat use (Hegg et al 2013) so as to predict survival to adulthood Williams 2002, Miller et al 2010). Further, we sought to contribute to literature regarding increment validation of Chinook salmon by focusing on the Yakima River population in Washington State, compared to work of Volk et al (2010), which used fish from Salmon River in Oregon, and Neilson and Geen (1982) and Gauldie (1991), which used Chinook salmon from Vancouver, British Columbia, Canada.…”

“…To quantify somatic growth, our research (e.g. Zabel et al 2010) used otoliths and thus relied upon studies that validated the formation of daily increments (e.g., Geen 1982, Gauldie 1991). Here our lab experiment sought to confirm the formation of daily increments and an emergence check so we could better understand the otolith microstructure of juvenile Chinook salmon.…”

Using otolith chemical and structural analysis to investigate reservoir habitat use by juvenile Chinook salmon Oncorhynchus tshawytscha

“…The natal origin chemical signature was quantified by averaging the first chemically stable point in the transect (generally located 110-200 μm from otolith core). The region was selected to estimate the geochemical signature during early growth in the natal stream because it is outside the area where maternal compounds associated with yolk-sac absorption are known to influence natal signatures (Barnett-Johnson et al, 2008), yet not within the area associated with potential early post-emergence downstream movement (Zabel et al, 2010). The capture location chemical signature was quantified by averaging a stable signature located in the 100 μm closest to the otolith edge.…”

“…The rearing geochemical signature was estimated during the first year of growth in adult samples with mean concentrations on the transect 500-650 μm from the otolith core. The location of the rearing signature was selected based on autumn O. tshawytscha in the Snake River where 250-800 μm from otolith core was considered first-year rearing and past 800 μm from otolith core was considered an overwintering signature (Zabel et al, 2010). Qualitative observations of elemental and isotopic profiles from the sampled individuals indicated stable signatures in this region.…”