Foote, Karen Jo

Shafland, Paul L.

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Northeast Gulf ScienceVolume 6Number 2 Number 2 Article 1210-1983A Lower Lethal Temperature for Fingerling Snook,Centropomus undecimalisPaul L. ShaflandFlorida Game and Freshwater Fish CommissionKaren Jo FooteFlorida Game and Freshwater Fish CommissionDOI: 10.18785/negs.0602.12Follow this and additional works at: https://aquila.usm.edu/gomsThis Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf of Mexico Scienceby an authorized editor of The Aquila Digital Community. For more information, please contact Joshua.Cromwell@usm.edu.Recommended CitationShafland, P. L. and K. J. Foote. 1983. A Lower Lethal Temperature for Fingerling Snook, Centropomus undecimalis. Northeast GulfScience 6 (2).Retrieved from https://aquila.usm.edu/goms/vol6/iss2/12Northeast Gulf Science Vol. 6, No.2 October 1983 175 A LOWER LETHAL TEMPERATURE FOR FINGERLING SNOOK, Centropomus undecimalis Snook (Centropomus undecimalis) are a marine/estuarine, tropical-subtro-pical gamefish which have a strong affinity for fresh water. Nearly all references to snook consider low water temperature as a factor limiting their distribution. Estimated lower lethal temperatures in current use are based on field observations (Storey and Gudger 1936; Storey 1937; Marshall 1958; Gilmore et at. 1978). This note is the first report of laboratory identified lower lethal temperatures for snook. These data were, in turn, used to estimate the potential inland range of snook in Florida. METHODS Eight 4-month-old snook (125-145 mm TL; 18-26 g) reared from artificially fertilized eggs (Shafland and Koehl1979) were transferred from a freshwater rearing pond to a 3400 ~ temperature control system (1 November 1977) which had been adjusted to the temperature of the pond (24°C). The temperature control system consisted of a cold water reservoir, eight 190 { aquaria with individual temperature controls ( ± 0.1 °C) and a collection and return box. Air-lifts provided even mixing of fresh water within aquaria. Snook were acclimated in the system for eight days at 24°C. Starting on day nine, temperature was decreased in six of the aquaria at a constant rate of 1 °C/day. Two aquaria were main-tained as controls at 24°C throughout the study. Daily monitoring included: counting the rema1n1ng forage organisms (Gambusia affinis), calcu-lating the number consumed and replacing those eaten during the previous 24 hours; observing the snook for behavioral changes associated with each decrease in temperature; and exchanging approximately 10% of the system's water volume and siphoning feces from each aquaria. Experimental fish we-re weighed, measured and examined for parasites and disease at the conclusion of the study. Using these methods, a sample size of five or more will yield the true mean lower lethal temperature ( ± 1 °C) for snook 95% of the time. This value is based on the maximum standard deviation (S = 0.9) for lethal temperatures reported for 14 tropical fishes pre-viously tested (Shafland and Pestrak 1982), 95% confidence and an 1 °C acceptable error of the mean (1.96 ox = 1°C; ox= S/(n-1)v., where ox= standard error of the mean, S = standard devia-tion and n = sample size). RESULTS Mean (n = 6) temperatures at which snook: stopped feeding completely was 14.2°C (S = 2.1; R = 12-18°C); lost equilibrium was 12.7°C (S = 0.81; R = 12-14°C); and died was 12.5°C (S = 0.84; R = 12-14°C). Of the experimental fish, one died at 14°C, another at 13°C and four at 12°C. Control fish remained healthy and continued to feed through-out the study period. Four of the six experimental fish fed at temperatures~ 2°C above their subse-quent lethal temperature. In general, snook became less active but neither lost equilibrium nor laid on the bottom for extended periods of time prior to dying. No parasites or physical anomalies were apparent on the experimental fish. Control fish continued feeding and appeared healthy throughout the study. 1Shafland and Foote: A Lower Lethal Temperature for Fingerling Snook, Centropomus undePublished by The Aquila Digital Community, 1983176 Short papers and notes DISCUSSION Storey and Gudger's (1936) survey of temperature induced mortalities at Sanibel Island, Florida, from 1886-1934 emphasized the temperature restricted range of snook. They concluded minimum safe water temperature for snook was 15.6°C. Marshall (1958) placed the nominal northern limits of snook in Florida at Vol usia County on the east coast and Hernando County on the west coast. Concurring with Storey and Gudger, he suggested that a low mean monthly water temperature of 15.6°C serves as a range determinant for snook in Florida. Similarly, Springer and Wood-burn (1960) reported finding three dead snook in a bayou when the water temperature dropped to 13°C. These field observations were supported by the present study in which juvenile snook began dying at 14°C. The winter of 1976-1977 was one of the coldest on record in Florida and there are several reports of its effect on snook. Major temperature induced snook mor-talities were reported between Cocoa and Daytona Beach (Sargent and Camp-bell1977). F.F. Snelson, Jr. (University of Central Florida, personal communica-tions) observed lethargic adult snook greater than 9.0 kg in coastal waters with a surface temperature of 8-9°C. Snelson and Bradley (1978) stated that many, if not most of these snook would probably recover as water temperatures warmed. Gilmore et at. (1978) reported adult snook swimming lethargically in water tempera-tures as low as·6.7°C and concluded that they die at temperatures approaching the lower end of a 6-13°C range. These latter reports suggest adult snook may be more tolerant of cold water than are fingerlings. Differences between these and previously reported field observations (Storey and Gudger 1936; Marshall1958; Springer and Wood-burn 1960) on the cold water tolerance of snook is poorly understoo'd. It is impossible to construct general water temperature isotherms for large geographic areas due to various thermal modifiers (e.g. water depth, flow, wind force) that cause temperatures to vary within and between different types of nearby aquatic habitats. Air tempera-tures, however, have been used routinely to reliably delineate isotherms. Since mean monthly air and stream tempera-tures in Florida are similar (Anderson 1975), it is suggested that air tempera-tures be used to estimate general water temperature zones. A subjective comparison of the lower lethal temperatures identified here and isotherms based on the mean monthly air temperatures for January (Thomas 1974; Wood and Fernald 1974; Shafland and Pestrak 1982), normally Florida's coldest month of the year (Bradley 1974), suggests fingerling snook will survive average inland Florida winters south of a line connecting St. Petersburg, Okeechobee City and Cape Canaveral. Fingerling snook may occasionally overwinter as far north as Gainesville, however, periodic survival beyond this point seems unlikely. ACKNOWLEDGMENTS We thank F.G. Banks, F.J. Ware, D.E. Holcomb, D.H. Koehl, J.W. Davis, L.A. Ager, P.G. Chapman, P.M. Shafland and B.B. Tiedrich for their assistance in various phases of this study. LITERATURE CITED Anderson, W. 1975. Temperature of Florida streams. Map Series No. 43 Revised. U.S. Geological Survey in cooperation with the Bureau of 2Gulf of Mexico Science, Vol. 6 [1983], No. 2, Art. 12https://aquila.usm.edu/goms/vol6/iss2/12DOI: 10.18785/negs.0602.12Northeast Gulf Science Vol. 6, No. 2 October 1983 177 Geology, FL Dept. Nat. Res., Tallahassee, FL. Bradley, J.T. 1974. The climate of Florida. Pages 45-70 In Climates of the states. Water Information Center, Inc., Port Washington, N.Y. Gilmore. R.G., L.H. Bullock and F.H. Berry. 1978. Hypothermal mortality in marine fishes of south-central Florida, January 1977. Northeast Gulf Sci. 2(2): 77-97. Marshall, A.R. 1958. A survery of the snook fishery of Florida, with studies of the biology of the principal species, Centropomus undecimalis (Bloch). Fl. St. Board Conserv. Tech. Ser. No. 22. 39p. Sargent. B. and H. Campbell. 1977. Winter kill 1977; the south. Sports Afield. 1977 (June): 33-37,134, 136-137. Shafland, P.L. and D.H. Koehl. 1979. Laboratory rearing of the common snook. Proc. Ann. Cont. S.E. Assoc. Fish & Wild!. Agencies 33:425-431. and J.M. Pestrak. 1982. Lower lethal temperatures for fourteen non-native fishes in Florida. Env. Bio. Fish. 7(2): 149-156. Snelson, F.F., Jr. and W.K. Bradley, Jr. 1978. Mortality of fishes due to cold on the east coast of Florida, January 1977. Fla. Sci. 41(1): 1-12. Springer, V.G. and K.D. Woodburn. 1960 An ecological study of the fishes of the Tampa Bay area. Fl. St. Board Conserv. Prof. Pap. Ser. 1: 1-104. Storey, M. 1937. The relation between normal range and mortality of fishes due to cold at Sanibel Island, Florida. Ecol. 18(1): 10-26. and E.W. Gudger. 1936. Mortality of fishes due to cold at Sanibel Island, Florida, 1886-1936. Ecol. 17(4): 640-648. Thomas, T.M. 1974. A detailed analysis of climatological and hydrological records of south Florida with reference to man's influence upon ecosystem evolution. Pages 82-122 In P.J. Gleason, ed. Environments of south Florida: Present and past. Memoir 2. Miami Geological Soc., Miami, Fl. Wood. R. and E.A. Fernald. 1974. The New Florida Atlas; Patterns of the Sun-shine State. Trend Publ., Tallahassee, Fl. 119p. Paul L. Shafland and Karen Jo Foote , Florida Game and Fresh Water Fish Commission, 801 N. W. 40th Street, Boca Raton, Florida 33431. Present Address: (K.J.F.) Loui· siana Department of Wildlife and Fisheries, P.O. Box 44095, Capitol Station, Louisiana 70804. 3Shafland and Foote: A Lower Lethal Temperature for Fingerling Snook, Centropomus undePublished by The Aquila Digital Community, 1983

A Lower Lethal Temperature for Fingerling Snook, Centropomus undecimalis

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A Lower Lethal Temperature for Fingerling Snook, Centropomus undecimalis

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