Variability in Burbot Cohort Abundance at Juvenile and Adult Stages in Columbia Lake, British Columbia

• Published in: Transactions of the American Fisheries Society
• Main Authors: Taylor, Josh L., Arndt, Steven K. A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2013
• Subjects: Burbot; Lota lota; lota
• Online Access: http://dx.doi.org/10.1080/00028487.2013.774292; https://afspubs.onlinelibrary.wiley.com/doi/pdf/10.1080/00028487.2013.774292

Abstract This study examined changes in the abundance of juvenile (age‐0 and age‐1) and adult Burbot Lota lota in Columbia Lake, British Columbia, for the 1991–1999 cohorts. The objectives were to quantify the degree of variation in cohort abundance at different life stages and investigate the timing of recruitment limitation. Adult spawner abundance and age composition were monitored at a tributary spawning site from 1996 to 2001. Juvenile cohort abundance was estimated from 1997 to 1999, providing age‐0 abundance indices for the 1997–1999 cohorts and age‐1 indices for the 1996–1998 cohorts. The number of tributary spawners declined from about 1,500 in 1996 and 1997 to 86 in 1999 and then rebounded to 995 by 2001. Adult length frequency and age composition showed that this fluctuation reflected periodic influxes of strong cohorts that dominated the spawning population. The strongest new cohort (1999) observed at the tributary in 2001 came from the smallest number of tributary spawners. Substantial differences in the juvenile abundance of cohorts spawned from similar numbers of adults (1996, 1997) suggested a density‐independent effect at the egg or larval stage. The 1999 cohort, however, was more abundant than several other cohorts at the adult stage but not at age 0, suggesting a second limiting period after the first growing season. Possible explanations for the exceptional survival of the 1999 cohort include a temporary expansion of interstitial habitat caused by unusually high water levels and low abundance of older Burbot. As large fluctuations in cohort abundance appear to be characteristic of some Burbot populations, inclusion of age composition is recommended for population assessments.