GnRH affects activity and jumping frequency in adult sockeye salmon, Oncorhynchus nerka

We tested whether waterflow, gender, maturity or treatment with a GnRH analogue affected jumping frequency, an acclimatization response and swimming activity in three-year-old sockeye salmon when confronted with an artificial waterfall. In our first behavioural experiment, increased waterflow and the stage of sexual maturity led to a significant increase in the number of fish that overcame an artificial waterfall, while sex had no significant effect. In a second experiment, we demonstrated that GnRH treatment affected behavioural responses in a waterfall channel as follows: (i) GnRH injected fish did not display an increase in their time of acclimatization while the acclimatization period in control fish increased significantly. (ii) GnRH significantly enhanced swimming activity and jumping motivation. We suggest that waterflow, degree of sexual maturity and injections with a GnRH analogue, lead to behavioural patterns that are correlated with migratory behaviour of adult sockeye salmon.