TEMPERATURE EFFECTS ON GROWTH AND YOLK UTILIZATION IN 

 YELLOWTAIL FLOUNDER, LIMANDA FERRUGINEA, YOLK-SAC LARVAE 



W. HuNTTiNG Howell' 



ABSTRACT 



Embryos and yolk-sac larvae of yellowtail flounder, Limanda ferruginea , were incubated at 4°, 8°, 10°, 

 and 12° C. Embryos incubated at 8° and 10°C produced significantly larger yolk-sac larvae at hatching 

 than those incubated at 4° and 12° C. Yolk utilization rate was positively correlated with temperature. 

 Growth in length was fastest at 12° C. At yolk-sac absorption there was no significant difference in size 

 among larvae incubated at 8°, 10°, or 12° C. Efficiency of yolk utilization prior to hatching was 86.2, 

 76.8, 73.5, and 45.9^r for 12°, 10°, 8°, and 4° C. Overall yolk utilization efficiency from fertilization to 

 yolk-sac absorption was highest at 12° C (47.17( ), intermediate at 8° and 10° C (43.8 and 42.2% ), and 

 lowest at 4 ° C ( 29. 8^^ i . Efficiency decreased during the course of development at all four temperatures. 



Based on the experimental results, it appears that sea temperatures between 8° and 12° C would have 

 little, if any, differential effect on larval size at yolk-sac absorption and therefore ability to survive. It 

 also appears that 4° C may be at or near the lower thermal limit for successful reproduction of southern 

 New England yellowtail flounder 



The yellowtail flounder, Limanda ferruginea, is an 

 important commercial species in both the New 

 England and Canadian otter trawl fisheries. Yel- 

 lowtail flounder range from the Gulf of St. Law- 

 rence south to lower Chesapeake Bay (Bigelow 

 and Schroeder 1953). Royce et al. (1959) and Lux 

 ( 1963) found that there are five relatively distinct 

 stocks within this range with little migration oc- 

 curring between them: Georges Bank, Cape Cod, 

 Nova Scotian, Newfoundland, and southern New 

 England. 



Over the past 35 yr, landings from the southern 

 New England ground have fluctuated widely 

 (Royce et al. 1959; Lux 1964, 1969; Sissenwine 

 1974), with a sharp decline observed in the late 

 1940's not accompanied by the usual symptoms of 

 overfishing, i.e., a decline in average size, in- 

 creased percentage of young fish, or increased 

 growth rate. Royce et al., (1959) suggested the 

 decline was caused by a warming trend inducing a 

 temporary northeastward shift of the population 

 center away from the southern New England 

 grounds. Sissenwine (1974) demonstrated a sig- 

 nificant inverse relationship between water tem- 

 perature and equilibrium catch and recruitment. 



The correlation between temperature and yel- 

 lowtail flounder abundance is an indication that 

 temperature may be causing fluctuations in the 

 fishery. This research was designed to investigate 



'Department of Zoology, University of Rhode Island, Kingston. 

 K.I.; present address: Department of Zoologv, University of New- 

 Hampshire, Durham, NH 03824. 



Manuscript accepted February 1980. 

 FISHERY BULLETIN: VOL. '78. NO. 3, 1980. 



the effect of temperature on growth rate, size at 

 hatching and yolk-sac absorption, and yolk utili- 

 zation rate and efficiency. Most fisheries biologists 

 agree that early life history stages of fishes are the 

 most vulnerable due to their small size, poor 

 swimming ability, and susceptibility to rapid en- 

 vironmental changes (May 1974a). Because of 

 this, the total set of environmental parameters in 

 which these young fishes develop will largely de- 

 termine their collective success or failure, and 

 consequently their year-class strength. During 

 larval development, the time when the larva 

 changes from its endogenous source of food (yolk) 

 to exogenous feeding is a "critical period" in the 

 organism's life history (Hjort 1926; Marr 1956; 

 Toetz 1966; May 1974a). Particularly important to 

 successful initiation of exogenous feeding is the 

 size and condition of the larva (Blaxter and Hem- 

 pel 1963; Braum 1967). To a large extent size and 

 condition will depend on the efficiency with which 

 the organism is able to convert its yolk to larval 

 tissue. Any environmental variable that affects 

 conversion efficiency could affect larval size, and 

 consequently larval ability to begin feeding. 

 Taken over the entire population of larvae, year- 

 class strength could be significantly affected by 

 such environmental influences. 



One such variable affecting yolk utilization 

 efficiency is temperature (e.g., May 1974b). Be- 

 cause temperature has been suggested as the 

 dominant environmental variable affecting yel- 

 lowtail flounder abundance and because other in- 



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