The Influence of Temperature, Salinity, and Postlarvai, Transport On the Distribution of Juvenile Spiny Lobsters, Panulirus Argus (Latreille, 1804), in Florida Bay

Abstract

[Florida Bay is the major nursery for the Caribbean spiny lobster, Panulirus argus, population in south Florida. This region is characterized by a series of shallow hardbottom or seagrass-covered basins separated by carbonate mudbanks that serve as barriers to water circulation and presumably to transport of planktonic larvae. Temperatures fluctuate dramatically in the bay and salinities there range from 35 ppt-50 ppt. In this study, we investigated the physiological tolerance of P. argus postlarvae to various combinations of temperature and salinity representative of the conditions found in Florida Bay and also determined the extent of postlarval recruitment into the interior of the bay. We measured postlarval settlement, juvenile abundances, and postsettlement habitat availability monthly (March 1992-July 1992) along 5 transects extending north from the main Florida Keys into the interior of Florida Bay. Concurrently, P. argus postlarvae were reared in the laboratory, in a completely crossed design, at four temperatures (18°C, 22°C, 29°C and 33°C) and four salinities (25, 35, 45 and 50 ppt). Survival, time:-to-metamorphosis, and growth to the first juvenile stage were measured. Few postlarvae settled at sites beyond the emergent banks ringing Florida Bay, and lobsters were only found in one basin (Twin Keys Basin) where habitat and environmental conditions were favorable. Laboratory results indicate that at high (33°C) and low temperatures (18°C) survival at salinities other than 35 ppt is greatly reduced. Our results indicate that postlarvae are not regularly transported into the interior of Florida Bay and that the lack of suitable nursery habitat and high salinity further limit recruitment, especially at extreme temperatures. Given the present conditions in Florida Bay, recruitment of P. argus is restricted to the southernmost reaches of Florida Bay nearest the Florida Keys., Florida Bay is the major nursery for the Caribbean spiny lobster, Panulirus argus, population in south Florida. This region is characterized by a series of shallow hardbottom or seagrass-covered basins separated by carbonate mudbanks that serve as barriers to water circulation and presumably to transport of planktonic larvae. Temperatures fluctuate dramatically in the bay and salinities there range from 35 ppt-50 ppt. In this study, we investigated the physiological tolerance of P. argus postlarvae to various combinations of temperature and salinity representative of the conditions found in Florida Bay and also determined the extent of postlarval recruitment into the interior of the bay. We measured postlarval settlement, juvenile abundances, and postsettlement habitat availability monthly (March 1992-July 1992) along 5 transects extending north from the main Florida Keys into the interior of Florida Bay. Concurrently, P. argus postlarvae were reared in the laboratory, in a completely crossed design, at four temperatures (18°C, 22°C, 29°C and 33°C) and four salinities (25, 35, 45 and 50 ppt). Survival, time:-to-metamorphosis, and growth to the first juvenile stage were measured. Few postlarvae settled at sites beyond the emergent banks ringing Florida Bay, and lobsters were only found in one basin (Twin Keys Basin) where habitat and environmental conditions were favorable. Laboratory results indicate that at high (33°C) and low temperatures (18°C) survival at salinities other than 35 ppt is greatly reduced. Our results indicate that postlarvae are not regularly transported into the interior of Florida Bay and that the lack of suitable nursery habitat and high salinity further limit recruitment, especially at extreme temperatures. Given the present conditions in Florida Bay, recruitment of P. argus is restricted to the southernmost reaches of Florida Bay nearest the Florida Keys.]