Effect of temperature on the reproductive potential of teleost fish (REPROCLIM)

Teleost fish are ectoderm animals and their physiological and metabolic activity depends on environment. To date there is still a lack of important information how temperature affects their reproduction. Increased and fluctuating temperature as expected as a possible scenario during climate change could have negative effects on reproduction by inhibiting the maturation of gametes, reducing the gamete quality and fertilization success or disturbing the embryogenesis. Also positive effects are possible due to acceleration of gamete maturation, an increase in fecundity or due to the induction of several maturation cycles. These problems are investigated in selected fish species.

After a project duration of 1 year we obtained the following results: In grayling the maturation of spermatozoa and eggs is affected by temperature and the egg maturation stronger than sperm maturation. Grayling require a gradually increasing natural temperature regime for maturation of gametes. At constant temperature and at abruptly increasing temperature females do not produce eggs and males semen of very low quality. Grayling spawn at water temperatures of 5.5 – 7.2°C. An increase in water temperature from 21 December to spawning for 1°C accelerates spawning for 5.5 days and an increase for 1°C in the last 10 – 15 days before spawning for 3.5 days. Water temperatures > 3°C inhibit the maturation of spermatozoa and eggs.

In teleost fish fertilization occurs in water. Therefore it is important to determine the thermal optimum for gametes. For spermatozoa we investigated the thermal optimum in four species, in brown trout, burbot, grayling and perch. The thermal optimum was 4 - 6°C for brown trout and burbot, 6 – 14°C for grayling, and 12 - 20°C for perch. Temperatures > 2°C above and below the optimum reduced the motility for circa 10-15%. This indicates that sperm motility and consequently also sperm fertility is only slightly affected by temperature.

The effect of temperature on the eggs and on the fertilization process was investigated in brown trout until now. The fertilization process was not affected in a temperature range from 3 to 15°C indicating a very broad temperature optimum. Therefore, an effect of increased water temperature due to climate change on the fertilization of brown trout can be excluded.

Also the embryos of most teleost fish develop in water and their differentiation is affected by temperature. For brown trout embryos the upper temperature limit for normal development was 9°C, higher temperatures resulted in increased mortalities or malformed larvae. Also short-term exposure to suboptimal temperatures for 1 – 5 d as possibly occurring due to extreme weather events induce irreversible disturbances in the process of embryogenesis and result in very low percentages of hatched larvae and of normal shaped larvae.

The project was funded by funds of the Austrian Climate and Energy Funds in the ACRP program - 1st Call for Proposals

www.klimafonds.gv.at

Publications based on that project