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Studies on the Biology of the Pink Shrimp

Durbin Creighton TabbDavid L. DubrowAndrew E. Jones

其他書名	Penaeus Duorarum Burkenroad, in Everglades National Park, Florida
出版	Marine Laboratory, Institute of Marine Science of the University of Miami, 1962
URL	http://books.google.com.hk/books?id=haZ_JQAACAAJ&hl=&source=gbs_api

註釋1. The biology of pink shrimp of northern Florida Bay was studied in conjunction with other studies on the ecology of estuarine plants and animals in a natural fluctuating environment. 2. More than 25,000 juvenile pink shrimp collected during the period September, 1957, through April, 1962, were examined for length and sex composition. 3. Pink shrimp enter the Coot Bay area as postlarvae with a minimum carapace length of 1.7 mm. and with a 4 dorsal spines on the rostrum. 4. The modal carapace length of entering postlarvae was 1.8 mm. with six dorsal and no ventral rostral spines. 5. There appear to be peaks of postlarval abundance in the spring and early summer, low numbers in the late summer and fall, and increasing numbers again beginning about November. 6. Postlarvae enter the Coot Bay area on the flooding tides at night, traversing the 3 mile length of Buttonwood Canal in approximately one hour at the peak velocity of the tide. 7. Peak numbers of postlarvae in samples usually occur at the peak velocity of the flooding tides. 8. Night plankton samples usually produce more postlarvae than daytime samples. 9. Catch-per-unit-effort data indicate that juvenile pink shrimp are most abundant during the period June through September. A smaller peak of abundance is usually found sometime during the period February through May. Lowest catch rates normally occur in December and January. 10. Among large samples of juvenile pink shrimp the sex ratio consisted of about 50 per cent females and 50per cent males, however, small samples may show wide departure from 1:1 ratio. 11. Predation by fish is probably the major cause of shrimp mortality in southern Florida estuarine areas. 12. Shrimp infected with sporozoan parasites causing the condition known as "cotton shrimp" were detected in only two instances during 55 months of sampling. 13. Pink shrimp are sensitive to sudden cold temperatures of winter and respond by moving to deeper water. With warming of the shallows they move back unless they have reached the size for final emigration. 14. Mass mortality of pink shrimp was observed following hurricane Donna. Deaths were caused by storm turbulence, stranding and post-hurricane oxygen depletion. 15. Carapace length-frequency distributions show time and characteristics of periods of juvenile immigration into the nursery, and size at time of emigration to the offshore grounds. 16. Orderly progression of modal groups along a similar pattern each year, followed by a sharp regression of size in June-July can be interpreted as indications of growth patterns and completion of offshore movement respectively. 17. An average monthly carapace length increase of about 2 mm. and a maximum of 3 to 4 mm. is suggested by length-frequency studies. 18. Few shrimp having carapace lengths greater than 25 mm. were taken in Coot Bay samples. This suggests that most have moved out of Coot Bay prior to attainment of that size. 19. Petersen tags were used in an attempt to learn whether the shrimp of the mainland nursery areas actually did contribute to the Tortugas fishery, had increased from 110 count to 36 count per pound (heads off), and in carapace length from 21 to 32 mm. 20. Three kinds of shrimp movement were noted ; daily movement within the bay systems back and forth with the tides, short-term offshore movements to escape winter cold, and mass movement offshore in response to abnormal weather and water conditions attendant with hurricanes. 21. Catches of small shrimp in the Tortugas during September and October, 1960, following hurricane Donna were far greater than the average for the same months of the preceding three years. The post-hurricane catches in the Tortugas contained much higher percentages of very small shrimp than usual at that time of year and suggests that hurricanes can cause shrimp to move offshore earlier and at a smaller size than is normal. 22. Pink shrimp are tolerant of wide ranges in salinity. Postlarvae and juveniles to 28 mm. carapace length were taken throughout the full range of salinity observed in the study area. The general scarcity of shrimp larger than 28 mm. carapace length in salinity lower than 32 parts per thousand suggest that they are less tolerant to salinity variation as they approach adult size. 23. Two other penaeid shrimp species were found in small numbers. Penaeus aztecus was taken in samples of P. duorarum. Trachypeneus constrictus was usually found in marine salinity areas of Florida Bay, and occasionally, in the tidal portion of the Shark River estuary.