Running Title: Temperature and reproduction in salmonids

Fish reproduction is likely to be affected by increasing water temperatures arising from climate change. Normal changes in environmental temperature have the capacity to affect endocrine function and either advance or retard gametogenesis and maturation, but above-normal temperatures have deleterious effects on reproductive processes. In Atlantic salmon (Salmo salar, L.) exposure to elevated temperature during gametogenesis impairs both gonadal steroid synthesis and hepatic vitellogenin production, alters hepatic estrogen receptor dynamics and ultimately results in reduced maternal investment and gamete viability. Exposure to high temperature during the maturational phase impairs gonadal steroidogenesis, delaying or inhibiting the preovulatory shift from androgen to maturation-inducing steroid production. There are also deleterious effects on reproductive development of female broodstock of rainbow trout (Oncorhynchus mykiss (Walbaum)) and Arctic charr (Salvelinus alpinus L.) when they are exposed to elevated temperature. Less is known about temperature effects on male fish but inhibition of spermiation has been observed in Atlantic salmon and rainbow trout. Among wild stocks, the response to elevated temperatur