THE RELATIONSHIP OF WINTER TEMPERATURE AND 

 SPRING LANDINGS OF PINK SHRIMP, PENAEUS DUORARUM, 



IN NORTH CAROLINA 1 



William F. Hettler and Alexander J. Chester 2 



ABSTRACT 



Spring landings of pink shrimp in North Carolina were highly correlated with water temperature 

 during the previous winter. The strongest relation was found between landings and the average 

 water temperature of the two coldest consecutive weeks of each year ( r 2 = 0.82). Following the cold 

 winters of 1977, 1978, 1980, and 1981, when temperatures averaged below 5°C, landings were 

 <160,000 kg. Following the warm winters of 1965, 1974, and 1975, when temperatures averaged 

 above 8°C, landings were >450,000 kg. Changes in water temperature through the year were de- 

 scribed by a sine-cosine curve in which minimum temperatures generally occurred during the 5th 

 week and maximum temperatures occurred during the 31st week of the year. Weekly mean air 

 temperatures were linearly related to water temperatures (r 2 = 0.97) over the entire range of data, 

 but they were not useful as proxy data for predicting pink shrimp landings (r 2 - 0.50) because the 

 air-water relation was more variable at low temperature. Local rainfall did not have a significant 

 effect on shrimp landings. 



Temperature is a critical environmental factor 

 influencing metabolism, growth, reproduction, 

 distribution, and survival of animals (Kinne 

 1963). Local abundance may be affected by mi- 

 gration or death in response to extreme devia- 

 tions from temperatures to which the animal is 

 adapted. The effect of such temperature ex- 

 tremes is expected to be more severe for a popu- 

 lation at the limit of its geographic range, par- 

 ticularly when temperature is known to be a 

 factor limiting north-south distribution (Wil- 

 liams 1969a). 



For species whose life cycle is completed in 1 

 yr, or in fisheries where reliance on annual re- 

 cruitment is heavy (Loucks and Sutcliffe 1978), 

 temperature records may be useful as a predic- 

 tor of landings. A cause-and-effect relationship 

 between harvest and temperature may be more 

 obvious for species with one year class than for 

 long-lived species whose landings are compli- 

 cated by multiple year-class contributions (Nor- 

 cross and Austin 1981). Penaeid shrimp, which 

 have an annual life cycle, have no significant con- 

 tribution from other year classes to compensate 

 for a reduction in biomass caused by unfavorable 

 temperatures. 



'Contribution No. 82- 12B of the Southeast Fisheries Center, 

 National Marine Fisheries Service, NOAA. 



Southeast Fisheries Center Beaufort Laboratory, National 

 Marine Fisheries Service. NOAA, Beaufort, NC 28516-9722. 



Shrimp mortality in the southeast United 

 States due to cold has been reported by Gunter 

 and Hildebrand (1951), Lindner and Anderson 

 (1956), and Lunz (1958). Of the three species of 

 Penaeus that occur in North Carolina waters, 

 only pink shrimp, Penaeus duorarum Burken- 

 road, overwinter in shallow estuaries (Williams 

 1955a) and, therefore, would be more likely to 

 suffer from abnormally cold winter tempera- 

 tures than either brown shrimp, P. aztecus, or 

 white shrimp, P. setiferus. Pink shrimp have an 

 annual life cycle in which the adults spawn off- 

 shore during early summer and postlarvae and 

 juveniles utilize the estuaries, where several en- 

 vironmental factors can affect distribution and 

 survival. These factors include temperature, sa- 

 linity, substrate, debris cover, and seagrass spe- 

 cies and density (Costello and Allen 1970; Grady 

 1971; Gunter 1950, 1961; Williams 1955a, 1958, 

 1969b). Peak recruitment of postlarvae into 

 North Carolina estuaries occurs from July to 

 September (Williams 1969b). Juveniles that 

 overwinter in the estuary migrate towards the 

 sea as adults, primarily in May and June, and be- 

 come the object of a trawl and channel net fishery 

 located in the mouth of the Neuse River, south- 

 western Pamlico Sound, Core Sound, Bogue 

 Sound, and in the ocean between Beaufort Inlet 

 and Bogue Inlet (Williams 1955b). 



The primary purpose of this study was to in- 

 vestigate the relationship between winter tern- 



Manuscript accepted March 1982. 



FISHERY BULLETIN: VOL. 80. NO. 4. 1982. 



761 



