MEPS 164:273-283 (1998)  -  doi:10.3354/meps164273

Estimation of starvation and diel variation of the RNA/DNA ratios in field-caught Sardina pilchardus larvae off the north of Spain

M. Alexandra Chícharo1,*, Luis Chícharo1, Luis Valdés2, Eduardo López-Jamar3, Pedro Ré4

1UCTRA, Universidade do Algarve, Campus de Gambelas, P-8000 Faro, Portugal 2Instituto Español de Oceanografia, Promontorio de San Martín, s/n, E-39004 Santander, Spain 3Instituto Español de Oceanografia, Avda. De Brasil, 31, E-28020 Madrid, Spain 4Lab. Mar. Guia, Fac. Ciências da Universidade de Lisboa, Est. do Guinelio, P-2750 Cascais, Portugal

The aim of this study was to analyse the general larval condition, to determine the incidence of starvation and to investigate the effect of time of day on RNA/DNA ratios among field-caught Sardina pilchardus (L.) larvae. The larvae were collected during 4 research cruises off northern Spain, during March, April, May and June 1992. A highly sensitive fluorometric method for nucleic acid quantification was applied to larvae of S. pilchardus. The means of the RNA/DNA ratio were relatively high, so the larvae collected off northern Spain were generally in good condition. Low percentages of starving larvae (RNA/DNA ratio less than 1.3), ranging from 0 to 3.23%, were found over the 4 mo. The RNA/DNA ratios were significantly correlated with zooplankton biomass. Larvae collected at night revealed higher RNA/DNA ratios compared to larvae caught during the day. This seems to indicate that there is some endogenous rhythm in the production of RNA. It would then follow that, if there are diel changes in RNA concentrations, average RNA indices can be unrepresentative if there is any day/night bias in sampling.

Fish larvae · RNA/DNA · Sardina pilchardus · Starvation · Diel variation

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