Shamaila Fraz

1 INTRODUCTION Temperature is a fundamental factor that can directly affect the physiology and the ecology of fishes because they are obligate poikilothermic ectotherms (Beitinger & Fitzpatrick, 1979; Kordas et al., 2011).

Abstract Temperate waters, such as the Great Lakes, are predicted to increase by 1{degree sign}C every decade. Poikilothermic fish thermoregulate behaviourally, moving to more suitable thermal environments. Embryos are incapable of locomotion and may be exposed to non-optimal temperatures during development.

1 INTRODUCTION Development consists of an integrated, ordered, and well-mapped sequence of early life-history events that are timed through extrinsic and intrinsic clocks present at molecular, cellular, and tissue levels (Burggren & Dubansky, 2018). These clocks time the spacing and the sequence of developmental events in the ontogeny of a species (Burggren & Dubansky, 2018) and define the rate of development and timing of the transitional events.