low feeding activity. This was clearly the case 

 with the few fish that survived 2 wk in 20° C. 

 These larvae were inactive, were not seen catch- 

 ing prey, and they grew very slowly. Larvae raised 

 at higher temperatures actively attacked and ate 

 prey as soon as it was introduced to the chamber. 

 Based on these results we hypothesize that red 

 drum spawning success and subsequent year-class 

 strength will be adversely affected by the early 

 onset of low water temperatures. Red drum is a 

 fall spawner and the young must survive and 

 grow at the winter temperatures found in low- 

 temperate estuaries; bay water temperatures 

 often fall below 20° C in November and average 

 15°-17° C in December in Texas (Martinez 1975). 

 The results indicate that for the first week or so 

 the larvae are stenothermal. The ability to find 

 and catch prey when the yolk sac has been 

 absorbed is a critical phase in larval survival (May 

 1974). Once temperature in the coastal water 

 declines to 20° C red drum larvae that have 

 reached the critical phase may not be able to find 

 and catch prey. An early reduction in nearshore 

 water temperatures could result in an unsuccess- 

 ful red drum reproductive effort for that year. 

 Indirect evidence implicates the importance of 

 temperature to reproductive success in that our 

 laboratory-reared red drum stop spawning when 

 the temperature drops below 20° C. This phenom- 

 enon may account for the earlier spawning of red 

 drum in its more northerly range (Mansueti 1960) 

 and prolonged spawning in warmer regions 

 (Jannke^). 



Acknowledgments 



This work was supported in part by the Texas 

 A&M University Sea Grant Program, supported 

 by the National Oceanic and Atmospheric Admin- 

 istration Office of Sea Grant, U.S. Department of 

 Commerce, under Grant #NA-79AA-D-00127, 

 and in part by awards from the Sid W. Richardson 

 Foundation and Caesar Kleberg Foundation for 

 Wildlife Conservation. 



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