SEASONAL AND DAILY CYCLES IN SOUND PRODUCTION ASSOCIATED WITH SPAWNING IN THE WEAKFISH, CYNOSCION REGALIS

Hydrophone recordings were made to document the daily and seasonal cyc les of weakfish, Cynoscion regalis (Sciaenidae), sound production in t he Delaware Bay. Recordings were made at three stations perpendicular to the shore and rated qualitatively on a scale of 0-4. 'Drumming' (so nic muscles, males only) and 'chattering' (pharyngeal stridulation, bo th sexes) were tallied separately. Weakfish were collected from the fi eld throughout the spring and summer to monitor the reproductive statu s of the population. A clear seasonal trend was noted in both drumming and chattering activities. Drumming activity rose abruptly in mid-May to maximal levels, which were maintained through late June, then drop ped off in July and ceased in August. Chattering activity began abrupt ly in late June, then rose through July and remained high in August. S easonal drumming activity was more intense at the inshore station. On a daily scale, drumming activity was at its lowest level during the ea rly to mid-morning, then increased to maximal levels in the early even ing and remained high until the following morning. There was no daily trend in chattering activity. Daily drumming activity was also most in tense at the inshore station. Male and female reproductive readiness, determined by gonadosomatic indices, sperm motility and plasma androge n levels, peaked within the period of maximal seasonal drumming activi ty.