SYNCHRONIZATION OF THE HATCHING TIME OF THE SILVERSIDE ODONTESTHES BONARIENSIS(TELEOSTEI, ATHERINOPSIDAE) THROUGH TEMPERATURE SALINITY, ANDOXYGEN STIMULI

The silverside, Odontesthes bonariensis, shows an extended hatching pe riod from the 15(th) to the 19(th) day after. fertilization at 15 degr ees C, what is undesirable for bioassay tests and larviculture purpose s, since it is important to obtain the maximum number of larvae emergi ng on the same day. In order to try a shyncronization of the hatching period, seven tests pins a control were performed, including temperatu re (+3 degrees C), salinity (+5 parts per thousand), and dissolved oxy gen (-1 mLO(2)l(-1)) shocks, either individualy or in combination. Mat ure: silverside were collected in the held and the eggs were artificia lly fertilized, in the laboratory they were incubated under controlled temperature (15 +/- 0.5 degrees C), salinity (5 +/- 1 parts per thous and), and photoperiod (12L:12D); the oxygen was kept at saturation lev el (6.79 mlO(2).l(-1)). The tests were initiated when the brat larvae began to hatch (15 days after the fertilization). The control groups s howed an average hatching of 38%, while eggs subjected to temperature shocks showed the best hatching performance, averaging 86%. The lowest result was observed with the salinity shock treatment, where only 14% of the larvae hatched during the 24h period. Based on these results, it is recommended a temperature shock (3 degrees C rise) to obtain at least 80% of the O. bonariensis larvae hatching on a single day.