Responses of Young California Grunion, Leuresthes tenuis, to Gradients of Temperature and Light

Abstract

In a laboratory temperature gradient, young California grunion, Leuresthes tenuis, exhibited a final modal preferendum of 25 C, 7 C lower than the final preferendum of young L. sardina from the Gulf of California. No circadian rhythms in thermal preference were found, and the final preferendum was unaffected by acclimation temperature. Like L. sardina, young L. tenuis were strongly attracted to bright light (10,000 lux). In a simultaneous opposed gradient of temperature and light, the fish spent more time at the preferred temperature than at the preferred light intensity. The laboratory results are discussed in relation to observed field distribution and geographic range.