Environmental and maternal effects on hatch characteristics and early growth of fishes in Newfoundland and Labrador

Penney, Heather D. (2019) Environmental and maternal effects on hatch characteristics and early growth of fishes in Newfoundland and Labrador. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Early life history can set individuals on phenotypic trajectories that subsequently affect their ability to survive. Additionally, early life stages are the most vulnerable to sub-optimal conditions and predation so early success can be fundamentally important for overall fitness and health of an individual. This thesis focuses on two important adaptations, phenotypic plasticity and growth compensation. In Chapter 2 I looked at how temperature and conductivity impacted embryonic development and found that most of the variation in hatch success was explained by temperature and not conductivity levels. In Chapter 3 I showed that hatch synchrony was affected by both temperature variability and water pH. However, the main focus was on the relative contributions of maternal and environmental factors (temperature variability and pH) on embryonic development and how maternal effects influenced the degree of phenotypic plasticity. Overall maternal factors were more important than environmental factors in explaining early life history characteristics and the degree of phenotypic plasticity that embryos expressed. Both Chapters 4 and 5 were field-based research chapters where I examined the relationship between growth rate and hatch timing. Through daily aging of otoliths I found no relationship between age and fork length in young of the year salmonids, suggesting that older fish were not necessarily larger and that later hatchers were likely growing faster than early hatchers. This was supported across four species from six different locations in Newfoundland and Labrador and may be a within-population compensatory growth adaptation for a shorter growing season that late hatchers experience. The populations I examined were from northern latitudes (Labrador-Chapter 4 and Newfoundland-Chapter 5) where the relationship cannot be explained by changes in environmental conditions or age alone, which may point to a within-population adaptation to a short growing season. Overall, this thesis supported previous work that abiotic factors affect early development. I found that environmental and maternal factors can impact hatch success and size, and that the timing of hatch can affect early growth rates. This is significant because small changes in growth and survival resulting from environmental changes can have far reaching implications.

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