Age and Growth of Coregonous kiyi in Lake Superior
Taylor A. Lepak, Northland College Derek H. Ogle, Northland College Mark R. Vinson, U. S. Geological Survey Deepwater Coregonids
• Difficult to identify species – Cisco (Coregonous artedi) – Bloater (Coregonous hoyi) – Blackfin Cisco (Coregonous nigrippinis) – Shortjaw Cisco (Coregonous zenithicus) – Kiyi (Coregonous kiyi) Coregonous kiyi
• Smallest of ciscoes • Historically found in all Great Lakes except Lake Erie – Now only in Lake Superior • Inhabit deep (>100m) waters • Only scale-derived ages published
Pratt & Chong, 2013 Objectives
• Assess ages – Compare scales and otoliths – Identify bias and precision among agers for otoliths • Assess population characteristics by region – Age distribution – Growth Field Methods Northern Ontario
Isle Royale Southern Ontario
Western Arm
East Keweenaw
• 21 sites • Subsampled for ageing • Bottom trawl collections • All fish <159mm • 5/sex/10mm from 160-279mm • Measured all fish • All fish >280mm • 335 total individuals Lab Methods Analysis
• Assess Age Bias – Age Bias Plot • Assess Age Precision – Percent Agreement – Coefficient of Variation (CV) • measure of relative variability between agers • <5 implies ages are acceptably precise • Age Distribution
Campana, 2001 Scales vs. Otolith Ages Between-Ager Otolith Ages 72% agreement (97% w/in 1 year) CV = 2.8 Overall Age Frequency 6 11 Length Frequency – 2014 Length Frequency – 2003-2014 6 1
1 7 2
2 3 8
3 4 9 Percentage of of Catch Percentage 4 10 5
5 6 11
Total Length (mm) Total Length (mm) Age Validation?
• Strong year-classes in 2003 and 2008 – Age-6 and age-11 in 2014
• High numbers of age-5, 10, and 12 fish Age Frequency by Region 6 11
6 6 11 11
6 Percentage Catch of Percentage 11 6 11
Consensus Age Consensus Age Conclusions
• Sporadic recruitment – Only 2 major year-classes since 2003 – Consistent across all regions of Lake Superior • Scales ages lower than otolith ages • Strong year classes allow age validation – Otoliths may provide accurate ages Future Work
• Difficulties with center and edge – Re-examine pictures • Examine growth Age and Growth of Coregonous kiyi in Lake Superior
Taylor A. Lepak, Northland College Derek H. Ogle, Northland College Mark R. Vinson, U. S. Geological Survey