Food and initial size influence overwinter survival and condition of a juvenile marine fish (age-0 Atlantic cod)

• Published in: Canadian journal of fisheries and aquatic sciences 2021-04, Vol.78 (4), p.472-482
• Main Authors: Geissinger, Emilie A, Gregory, Robert S, Laurel, Benjamin J, Snelgrove, Paul V.R
• Format: Article
• Language: English
• Subjects: Age; Analysis; Arctic zone; Availability; Bioenergetics; Body condition; Climatic zones; Coastal ecology; Cod; Condition factor; Controlled conditions; Energy budget; Famine; Feeding trials; Fish; Food; Food availability; Food supply; Gadidae; Gadus morhua; Growth; Juveniles; Laboratory experimentation; Lipids; Low temperature; Marine; Marine fish; Metabolism; Methods; Mortality causes; Overwintering; Settlers; Starvation; Survival; Survival after airplane accidents, shipwrecks, etc; Water temperature; Winter
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/cjfas-2020-0142

In subarctic Newfoundland, age-0 Atlantic cod (Gadus morhua) settle into coastal habitats in several summer–autumn pulses, resulting in broad length-frequency distributions before winter. Low winter temperatures and potential decreases in food availability pose challenges for young-of-year fish. To examine how size variation affects overwintering success under contrasting food scenarios, we conducted 114-day laboratory feeding trials at ambient overwinter sea temperatures, using demersal age-0 cod collected from Newman Sound, Newfoundland. We reared two size classes of juvenile cod under four daily ration levels (starvation, low, medium, high). We used Fulton’s K condition factor to interpret effects of food availability and fish size on survival over winter. We showed that small amounts of consumed food (80% until Day 74. Therefore, we expect higher survival of earlier settlers and increased size-selective mortality in age-0 cod during either unproductive or protracted winters, when food abundance is often low.