krillSpawn (Spawning frequency and egg production) 04jan 9 Jan to 28 Jan, 2004 [of experiments] Spawning frequency and egg production experiments were conducted on board the Laurence M. Gould (04-01) in a flow-through aquarium at ambient temperature according to the method of Ross and Quetin (1983). These experiments yield estimates of spawning intensity, i.e. the percent of the females in the reproductive cycle spawning per day, and the interbrood period or interval between multiple batches of eggs. Measurements of embryo size and the batch volume are indices of individual reproductive output during the cruise. Female total length, period spawned, embryo batch volume, embryo diameter, estimates of total number of embryos. Details of experiments include: experiment number, initial temperature, and for each 6-h observation period - time checked, temperature of the seawater in the individual spawning jars, and number of females spawned. The summary includes experiment number, event number, trawl number, day/month start, local time start, grid location, average temperature, total number of spawners, total number of females in the experiment, duration of experiment, and calculated spawning frequency. Spawning frequency (% spawning per day) is: 100 * (no. spawners/no. females in experiment)/days of experiment The inverse of the spawning frequency is the interbrood period. The number of embryos in a batch is estimate from an equation derived from 5 regression lines relating embryo number and volume. These regression lines are derived from incremental embryo counts with volume measured as embryos accumulate in the tube for five females with embryos of as wide a size range as possible. Both the slope and y-intercept are significantly related to embryo diameter. Calculated number of embryos = y-intercept + slope * batch volume = For 2004: ((0.275 * embryo diameter) Ð 252.48) + ((-10.829 * embryo diameter) + 11301)* batch volume Experiments are conducted as indicated by female status, i.e. adequate number of females with red thelycums, with the objective of one experiment per transect line. Five experiments were conducted during the 04Jan LTER cruise: two on the 600 line, and one each on all but the 500.* transect line. Observations of spawning frequency during 5 growth experiments, yielding additional estimates of spawning frequency, including 2 on the 500.* transect line. Euphausia superba are collected with the 2-M trawl for these experiments, either with standard tows or with targeted tows. Experiments are conducted on board in the aquarium room in flowing seawater tables. All live individuals with red thelycums from a catch are gently transferred from the initial catch tub to a second tub filled with cold seawater. The red thelycum indicates that the female is in the reproductive cycle. Forty females are randomly selected from the total by picking a spot in the tub and only removing those individuals that swim through the spot. Each female selected is placed in a 2-liter glass jar filled with filtered seawater and with a 3000 µm mesh circle partway down the jar to prevent the female from damaging the eggs after release. Each jar is checked for the presence of eggs every 6 h for 4 days. If eggs are seen, the female is given an additional 6 h to completely release the batch. The female is then removed, the total length measured, and then preserved individually in 10% buffered formalin. Total length is measured with digital calipers from the tip of the rostrum to the end of the uropods. The eggs are collected by attaching a funnel apparatus terminated with a scintillation vial to the 2-liter jar, inverting the jar, and allowing the eggs to sink into the scintillation vial over the next 1-2 h. The entire batch of eggs is then preserved in 5% buffered formalin. With this timing, eggs are preserved by a maximum age of 12-15 h and before the diameter of the egg begins to increase (Quetin and Ross, 1984). At the end of the experiment all non-spawners are measured fresh and either frozen individually or preserved as a group of non- spawners. In the laboratory at UCSB or at Palmer Station, diameters, including the perivitelline membrane, of 30 eggs from each batch are measured under a dissecting microscope. The total volume of the batch of eggs is measured to the nearest 0.025 in a narrow (0.4 mm ID) tube calibrated with a volumetric pipette and marked in 0.05 ml increments. Spawning frequency experiments are planned for the outer edge of each transect line (grid stations 160, 180 or 200) in order to observe any alongshore gradients in spawning intensity or reproductive output. spawning intensity, spawning frequency, interbrood period, fecundity, reproductive output In the first row a "!" is preceded by the number of columns of data (n) and followed by information about the experiment. Each column is described in the subsequent n rows. Data follows as comma separated text. Palmer LTER web site 04jan/krillspawn/ Raw data from each experiment is in files named spawn (experiment number).csv. The header for each file contains the study, spawning frequency experiment number, and event number. Columns of data are: female total length (mm), spawning period (period in which female released embryos 1-16; 0 if no spawn), embryo batch volume (ml), embryo diameter (µm), estimated total number of embryos, and notes. Spawn_sum is a summary file for all experiments during the cruise. Data include experiment number, event, tow, date of start of experiment, local time start, LTER grid location, average temperature, number of spawners, number of females in experiment, duration of experiment, and spawning frequency over the experiment, and notes. Spawn_details is a file with details of local time experiment checked, temperature, and number of spawners for each of the observation periods (usually 16) for each experiment. Robin M. Ross and Langdon B. Quetin Marine Science Institute University of California at Santa Barbara Santa Barbara, CA 93106 Experiments conducted and females measured by RMRoss, B Cheng, S Talley, R Cadiz, A Kaiser and J Watts on board the L. M. Gould. In austral spring 2004 J Sprague measured the diameters of embryos, the batch volumes for each female, and did incremental counts and volumes for five batches of eggs to set up the relationship between embryo diameter and number of embryos per volume. RM Ross, J Sprague RM Ross, LB Quetin and J Sprague RM Ross 3 November, 2006 Ross, RM and LB Quetin. 1983. Spawning frequency and fecundity of the Antarctic krill Euphausia superba. Marine Biology 77, 201-205. Quetin, LB and RM Ross. 1984. Depth distribution of developing Euphausia superba embryos, predicted from sinking rates. Marine Biology 79, 47-53. Quetin, LB and RM Ross. 2001. Environmental variability and its impact on the reproductive cycle of Antarctic krill. Amer. Zool. 41: 74-89. At start of data collection PIs train and supervise new members of the research team to ensure that measurements are consistent across experiments and cruises. Data entry checked by a second person, both by proofing and by inspecting graphs for outliers. Top of Form 1 Datafile Form V1.2 for describing a data file.