Investigation of unusual mortalities of bottlenose dolphins along the mid-Texas coastal bay ecosystem during 1992

Colbert, A. A. and Scott, G. I. and Fulton, M. H. and Wirth, E. F. and Daugomah, J. W. and Key, P. B. and Strozier, E. D. and Galloway, S. B. (1999) Investigation of unusual mortalities of bottlenose dolphins along the mid-Texas coastal bay ecosystem during 1992. Seattle, WA, NOAA/National Marine Fisheries Service, (NOAA Technical Report NMFS, 147)

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Abstract

An investigation was conducted into the deaths of more than 220 bottlenose dolphins (Tursiops truncatus) that occurred within the coastal bay ecosystem of mid-Texas between January and May 1992. The high mortality rate was unusual in that it was limited to a relatively small geographical area, occurred primarily within an inshore bay system separated from the Gulf of Mexico by barrier islands, and coincided with deaths of other taxa including birds and fish. Factors examined to determine the potential causes of the dolphin mortalities included microbial pathogens, natural biotoxins, industrial pollutants, other environmental contaminants, and direct human interactions. Emphasis was placed on nonpoint source pesticide runoff from agricultural areas, which had resulted from record rainfall that occurred during the period of increased mortality. Analytical results from sediment, water, and biota indicated that biotoxins, trace metals, and industrial chemical contamination were not likely causative factors in this mortality event. Elevated concentrations of pesticides (atrazine and aldicarb) were detected in surface water samples from bays within the region, and bay salinities were reduced to <10 ppt from December 1991 through April 1992 due to record rainfall and freshwater runoff exceeding any levels since 1939. Prolonged exposure to low salinity could have played a significant role in the unusual mortalities because low salinity exposure may cause disruption of the permeability barrier in dolphin skin. The lack of established toxicity data for marine mammals, particularly dermal absorption and bioaccumulation, precludes accurate toxicological interpretation of results beyond a simple comparison to terrestrial mammalian models. Results clearly indicated that significant periods of agricultural runoff and accompanying low salinities co-occurred with the unusual mortality event in Texas, but no definitive cause of the mortalities was determined. (PDF file contains 25 pages.)

Item Type: Monograph or Serial Issue
Title: Investigation of unusual mortalities of bottlenose dolphins along the mid-Texas coastal bay ecosystem during 1992
Personal Creator/Author:
CreatorsEmail
Colbert, A. A.
Scott, G. I.
Fulton, M. H.
Wirth, E. F.
Daugomah, J. W.
Key, P. B.
Strozier, E. D.
Galloway, S. B.
Series Name: NOAA Technical Report NMFS
Number: 147
Date: 1999
Publisher: NOAA/National Marine Fisheries Service
Place of Publication: Seattle, WA
Issuing Agency: United States National Marine Fisheries Service
Subjects: Ecology
Management
Fisheries
Item ID: 2522
Depositing User: Patti M. Marraro
Date Deposited: 28 Jul 2009 17:07
Last Modified: 29 Sep 2011 18:48
URI: http://aquaticcommons.org/id/eprint/2522

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