Editorial Type:
Article Category: Research Article
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Online Publication Date: 01 Sept 2010

Salinity Tolerance of the African Jewelfish Hemichromis letourneuxi, a Non-native Cichlid in South Florida (USA)

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Page Range: 475 – 480
DOI: 10.1643/CP-09-069
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Abstract

The African Jewelfish (Cichlidae: Hemichromis letourneuxi) is a predatory, non-native fish that has recently (since 2000) begun to expand its geographic range across south Florida. The salinity tolerance of H. letourneuxi was unknown, and thus it was unclear whether the species could use estuarine or coastal environments. The response of H. letourneuxi to chronic change in salinity was evaluated here by exposing fish to progressively increasing salinities (0–80 ppt). Fish were held at target salinities for a minimum of 30 days. The species showed excellent survival from 0–50 ppt. At 60 ppt, only 25% of the fish survived, and mean estimated survival time was 12 days. Above 60 ppt, mortality was 100%. Fish grew equally well from 0–50 ppt. In another experiment, fish were transferred directly from freshwater to various salinities from 5–35 ppt (seawater) and held for seven days, after which survivors were returned to freshwater. All fish transferred directly from freshwater to salinities up to 20 ppt survived; only 56% survived when transferred from freshwater to 25 ppt, and none survived transfer above 25 ppt. Experimental results indicated that H. letourneuxi can persist easily in salinities prevalent in coastal environments, even during periods of hypersalinity common in south Florida estuaries. Salinity will not restrict its dispersal by coastal pathways.

Copyright: 2010 by the American Society of Ichthyologists and Herpetologists
Figure 1
Figure 1

Distribution of H. letourneuxi in Florida (shaded areas). A =  Hillsborough River, B  =  Alafia River, C  =  Myakka River, D  =  Peace River, E  =  Caloosahatchee River, F  =  Miami River Canal, ENP  =  Everglades National Park, BNCP  =  Big Cypress National Preserve. U.S. Geological Survey Hydrologic Unit Codes (HUCs) were used as a base to build the map. Data used to create the map were derived from the USGS Nonindigenous Aquatic Species Database, which is composed of several different data sources including published literature, reports, other databases, and personal communications.


Figure 2
Figure 2

Survival of H. letourneuxi over time when chronically exposed to various salinities (0–60 ppt). When compared to the control (0 ppt) with the log-rank test, treatments of 60, 70, and 80 ppt were significantly different (all P < 0.001). Log-rank statistics for each test are: 12.94 (0–60 ppt comparison), 24.00 (0–70 ppt comparison), and 20.00 (0–80 ppt comparison).


Figure 3
Figure 3

Survival of Hemichromis letourneuxi over time when acutely exposed to various salinities (0–35 ppt). When compared to the control (0 ppt) with the log-rank test, treatments of 25, 30, and 35 ppt were significantly different (all P < 0.05). Log-rank statistics for each test are: 4.88 (0–25 ppt comparison) and 19.00 (0–30 and 0–35 ppt comparisons).


Contributor Notes

U.S. Geological Survey, 7920 NW 71st Street, Gainesville, Florida 32653, e-mail: (PJS) pschofield@usgs.gov. Send reprint requests to PJS.
Program in Fisheries and Aquatic Sciences, School of Forest Resources and Conservation, University of Florida, Tropical Aquaculture Laboratory, 1408 24th Street SE, Ruskin, Florida 33570, e-mail: jeffhill@ufl.edu
U.S. Geological Survey, Everglades National Park Field Station, 40001 State Road 9336, Homestead, Florida 33034, e-mail: arc_wfl@bellsouth.net

Associate Editor: E. Schultz.

Received: 13 Apr 2009
Accepted: 16 Feb 2010
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