HOUDE: ABUNDANCE AND POTENTIAL YIELD OF ROUND HERRING 



class was nearly twice as abundant in 1972-73 as 

 in 1971-72. Other length classes were somewhat 

 more abundant in 1971-72 catches. 



11) Mortality rates of larvae were estimated by 

 length and for estimated ages. For lengths, the 

 instantaneous coefficients of decline in catches 

 wereZ = 0.2269 in 1971-72 and Z = 0.3647 in 

 1972-73, corresponding to 20.3 and 30.5% losses 

 per millimeter of growth. For ages, a range of 

 estimates of daily mortality, based on varying 

 growth rates and nonfully vulnerable larva stage 

 durations, was obtained. The most probable daily 

 mortality estimates were Z = 0.1317 in 1971-72 

 and Z = 0.1286 in 1972-73, corresponding to per- 

 centage losses of 12.3 and 12.1% on a daily basis. 



12) It is probable that more than 99.4% mortal- 

 ity from eggs to 15.5-mm larvae occurred in 1971- 

 72, and that more than 98.3% mortality occurred 

 during that period in 1972-73. About 4 larvae/ 

 1,000 eggs spawned survived to 31 days and 15.5 

 mm in 1971-72, while about 12 larvae/1,000 eggs 

 survived to that stage in 1972-73. 



ACKNOWLEDGMENTS 



This project was initiated as part of cooperative 

 efforts to investigate biological and physical pro- 

 cesses in the eastern Gulf of Mexico. Assistance 

 was provided by many people and agencies. Par- 

 ticular thanks go to Murice Rinkel of the State 

 University System of Florida, Institute of 

 Oceanography, for his help in coordinating 

 EGMEX and Western Florida Continental Shelf 

 cruises, as well as reduction of physical oceano- 

 graphic data. The 1971 plankton surveys were 

 coordinated with the National Marine Fisheries 

 Service MARMAP program in the eastern Gulf of 

 Mexico and special acknowledgments go to the 

 following personnel: Ed Hyman, Larry Ogren, 

 William J. Richards, Charles Roithmayr, and 

 Stuart Smith. My students and technical person- 

 nel deserve thanks for long hours spent at sea and 

 tedious hours sorting and enumerating; among 

 these are Steven Berkeley, Alfred Cardet, Reuben 

 Charles, Ann and Nicholas Chitty, Lise Dowd, 

 John Klinovsky, Walter Stepien, A. Keith 

 Taniguchi, and Gregg Waugh. Harvey Bullis and 

 Paul E. Smith of the National Marine Fisheries 

 Service criticized earlier drafts of this paper, and I 

 thank them for the suggestions and ideas that 

 they provided. 



This research was sponsored by NOAA Office of 



Sea Grant, Department of Commerce, under 

 Grant 04-3-158-27 to the University of Miami. 



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