in the suspected spawning sites near either pulled a pier. Water volum - PDF document

in the suspected spawning sites near either pulled a pier. Water volume filtered, calculated usually varied were taken retained untreated provide live be hatched and egg the young but since looked similar they raised until time series samples were taken plankton samples taken h period in this initial samples taken these same coincidentally with drum and collected in plankton samples in the morning in August through samples taken collected in same samples. silver perch, red night time samples taken a pier the pass between was determined by during the sampling. seatrout, spotted seatrout, drum and the preserved sorted, counted stages determined. Additional information was gained studies using photoperiod-temperature several sciaenids (described 1976, 1977, Laboratory-spawned red eggs were silver perch plankton were also used carried out using laboratory-raised red drum wet weight. experiments were using red the same No fish were re-used ment. One on size) placed in eggs, spawned were added at densities h the the remaining darkness during the experiment. The rate in with no were standardized replication was compare individual soon after lights were turned on in the evening while maintaining h dark photoperiod, and the shifted their time accordingly. developmental time drum is shown the plankton developed in Based on field collections, times reported by May assumed that other sciaenids in our h sampling that newly spawned eggs were taken near sunset lected later the morning. collected live the developmental al.: Spawning in 32 min 50 min ocellatus. Development time each subsequent red drum noon collection. laborative study, Females were running final oocyte period before dusk (Thomas et al. samples taken rnin from dark during July, well-developed embryos lected in samples (Table when the eggs were in late cleavage stages. occurred over a period beginning about hour after 2. Cynoscion (no. 100 11, 1983. Sunset occured Morula Late 7 3 2 5 9 0 Ecol. Prog. several hours the new eggs were during the sunset (Table Samples taken only embryo Silver perch occurred over a longer period 4) with some spawning earlier than continuing later in the evening. However, silver perch never this relatively 'window' around sunset. 15 other from April through September, sam- times throughout day and in a predictable stage ment based spawning near sunset the previous day. collected after species were collected in the bay estuarine spawners. consistently collected on several other sciaenids been developed bi-weekly in late summer (water tempera- embryos were always in stage at known development 12 to collected at night between cell division time period 11, 1983. Sunset occured Time (h) Egg developmental 4 5 1915 18 55 524 1946 96 352 74 2045 646 15 7 1192 2724 earlier, near shown in (1) precise time series data spotted seatrout; tions over seatrout, black last 5 represent the peak spawning the range times. Where silver perch, spotted seatrout, in the within a was indicated several other sciaenids. eggs were time before feeding rate (Table showed that