Title: Ichthyofaunal evaluation of the Peace River, Florida
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Title: Ichthyofaunal evaluation of the Peace River, Florida
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Biological Sciences


Florida Game and Fresh Water Fish Commission, 3900 Drane Field Road, Lakeland, FL 33811

ABSTRACT: Fishes were collected from six locations along the freshwater portion of the Peace
River from 1983 through 1988. Analysis of fish community characteristics such as species rich-
ness, diversity, abundance, biomass and species composition indicated the fish community of the
Peace River has been significantly impacted by human activities. Degraded water quality and
invasion of exotic fishes have altered species composition, diversity and fish production. Effluent
from headwater lakes and streams increased turbidity and biological oxygen demand in the upper
35-km section of the river that was dominated by pollution-tolerant fishes. Dilution from tribu-
taries exhibiting higher water quality improved biotic conditions downstream as evidenced by
higher species diversity and more complex fish community structure. Tidal influence on the lower
35-km portion of the river reduced flushing and stressed conditions were indicated by lower
species richness and diversity. Fish community structure at the lower river was dominated by
large piscivores and omnivores.

THE Peace River begins in Polk County at Lake Hancock in south-central
Florida and flows southwest through Hardee and DeSoto counties before
discharging into Charlotte Harbor estuary in Charlotte County (Fig. 1). The
river is 211 km in length, descending 30 m at an average gradient of 0.2 m/km
with an average annual discharge of 32.7 m3/s (Estevez et al., 1981). The
Peace River valley is a pinnate system, draining 5959 km2.
Micoene deposits rich in phosphate ore were mined from the river bottom
in the late 1800's and from lands within the valley from 1900 to the present.
Most strip mine operations have occurred in the upper valley, drastically
altering natural hydrology and degrading river water quality (Hand et al.,
1988; Estevez, et al., 1981). Mining operations have caused catastrophic fish
kills, most recently occurring in 1967 and 1971 (Ware, 1969; Chapman,
1973). These were caused by massive discharges of wastewater from clay-
filled settling basins which created extremely high turbidity and resulted in
high mortality of fishes and invertebrates. Public outcry and legislative
actions during the late 1970's resulted in stringent regulations that signifi-
cantly reduced the incidence of these events.
The Peace River receives a large amount of pollutants from municipal/
industrial effluent and urban/agricultural runoff. Most cultural inputs occur
near the headwaters; as a result, the upper river exhibits poor water quality
(Hand et al., 1988; Estevez et al., 1981; Florida Department of Environmen-
tal Regulation, 1980; Florida Board of Health, 1965). Lake Hancock is a
hypereutrophic waterbody that discharges water with extremely high con-
centrations of blue-green algae, resulting in high turbidity, high biological
oxygen demand and low dissolved oxygen levels. Peace Creek drains agricul-
tural lands and many urban lakes before entering the river 4.4 km below
Lake Hancock. Studies compiled by Estevez and co-workers (1981) and Hand


Peace River Drainage Basin

FIc. 1. Location of the Peace River and fish population sample stations (H-Homeland, FM-
Fort Meade, W-Wauchula, G-Gardner, N-Nocatee, FO-Fort Ogden), 1983-1988.

and co-workers (1988) noted that progressive dilution from less disturbed
tributaries resulted in improved water quality downstream. Ross and Jones
(1979) determined that Charlie, Joshua and Horse Creeks were the least pol-
luted of all Peace River tributaries.
Groundwater withdrawals for agricultural, mining and potable uses have
resulted in a significant decline in the potentiometric surface of the Floridan
aquifer (Barcelo et al., 1989). Groundwater contributions to the Peace River
water budget have been reduced, most severely at the upper valley (South-

No. 4, 1990]

west Florida Water Management District, 1988). This groundwater flow re-
duction exacerbates water quality problems by eliminating dilution effects
and decreasing flow rates.
Limited study of Peace River fishes has occurred. First collections of fish
were by Woolman (1892), who collected 20 species from the river and several
tributaries during the winter of 1890-91. The Florida Game and Fresh Water
Fish Commission (FGFWFC, 1963) conducted fish sampling at irregular in-
tervals from 1961 through 1963. Investigations of catastrophic fish kills by
Ware (1969), Ware and Fish (1969) and Chapman (1973) have provided the
most comprehensive information on Peace River fishes. Most recent fish col-
lections were conducted in 1976 by Texas Instruments (Estevez et al., 1981).
The objective of this study was to update the ichthyofaunal data base
through a comprehensive five-year sampling program. The fish community
was also evaluated to determine the degree that man's activities have altered
riverine ecology from the expected natural state. The advantages of using fish
as indicators of environmental disturbance over water quality or other
aquatic organisms were summarized by Karr (1981) and Hocutt (1981). Karr
(1981) developed an ecological assessment system (index of biotic integrity or
IBI) that incorporates a series of fish community attributes related to species
composition and ecological structure. Metrics used to calculate IBI are re-
gionally specific (Fausch et al., 1984) and no metrics applicable to peninsular
Florida streams have yet been developed. In this study, evaluation of biotic
stress was made by integrating the following parameters: fish abundance and
biomass, species richness, composition and diversity.
MATERIALS AND METHODs-Fish collections were made from six sites along Peace River (Fig.
1). Sample stations and distance downstream from Lake Hancock were: Homeland-21 km, Fort
Meade-35 km, Wauchula-70 km, Gardner-123 km, Nocatee-170 km and Fort Ogden-195 km.
River width varied between 7 and 12 m at all stations except for Nocatee and Fort Ogden where
approximate widths were 30 m and 60 m, respectively. The fish community was sampled during
various seasons from 1983 through 1988. Sampling was not conducted during extreme high nor
low flow periods to avoid anomalous results.
Fish were collected using an electrofishing boat, operating on pulsating direct current varying
from 6.0 to 7.0 amps. Electrical output was regulated by a Smith-Root model VI-A electrofisher,
utilizing the aluminum boat hull as the cathode and a pair of bow-mounted boom electrode
arrays as anodes. Two people at the bow of the boat captured stunned fish with dip nets. Stand-
ardized sampling technique was used in all samples. Available habitat types (brush, macro-
phytes, pools and eddies) at each station were sampled for 30 to 60 minute time periods. Time
periods were measured by the electrofisher as "pedal down time" or the amount of time electric-
ity was actually applied to the water. A total of 57 samples was conducted for a total electrofish-
ing effort of 2866 "pedal-down" minutes.
Species richness is the number of species collected per sample. Species diversity (H') was
calculated by the Shannon-Weaver index (Shannon and Weaver, 1949). Numerical abundance
per station is expressed by catch-per-unit-effort (CPUE) as the number of fish collected per
"pedal-down" minute. Biomass indices are expressed as total weight (kg) of fish collected per
"peda-down" minute. Fish community composition for each station is the median percent com-
position of CPUE for all samples.


[Vol. 53

TABLE 1. Species composition of electrofishing samples collected from six stations along the Peace River, 1983-88.

Homeland Ft. Meade Wauchula Gardner Nocatee Ft. Ogden
Species Percent Composition-Median of Samples
Micropterus salmoides 4.4 8.7 11.9 9.4 11.4 7.7
Lepomis macrochirus 10.9 12.6 14.4 5.0 8.4 9.2
Lepomis microlophus 9.6 11.1 5.7 6.5 8.4 4.8
Lepomis punctatus 11.4 27.5 14.2 11.8 7.8 1.4
Lepomis marginatus 0.5 0.0 0.2 0.3 0.7 0.0
Lepomis gulosus 0.5 0.3 0.4 0.4 0.2 0.2
Pomoxis nigromaculatus 1.4 0.0 0.1 0.0 0.0 0.0
Ictalurus punctatus 0.6 0.8 2.8 9.4 8.6 12.7
Ictalurus catus 0.4 0.5 0.6 0.7 0.6 7.0
Ictalurus nebulosus 0.4 0.2 0.4 0.0 0.3 0.1
Ictalurus natalis 0.0 0.0 <0.1 0.1 0.2 0.0
Noturus gyrinus 0.0 0.0 <0.1 0.0 0.0 0.0
Lepisosteus platyrhincus 22.8 13.8 13.3 11.7 16.9 18.5
Lepisosteus osseus 0.3 0.5 1.5 1.3 2.7 14.2
Amia calva 3.4 1.1 1.1 0.3 1.4 1.6
Erimyzon sucetta 0.3 0.3 1.8 0.3 0.0 0.0
Dorosoma cepedianum 1.3 1.1 <0.1 0.1 0.3 0.9
Dorosoma petenense 0.8 0.0 <0.1 0.0 0.0 0.0
Poecilia latipinna 1.0 0.3 0.1 0.6 0.0 0.0
Gambusia affinis 2.3 0.1 0.2 1.5 0.1 0.7
Fundulus seminolis 3.0 4.3 3.8 7.7 4.0 2.6
Notropis petersoni 0.7 7.7 7.8 11.4 3.3 0.2
Notropis maculatus <0.1 0.0 0.0 0.0 0.0 0.0
Notemigonus crysoleucas 1.4 2.9 0.1 0.1 0.1 0.1
Labidesthes sicculus 0.5 0.7 1.8 2.8 0.6 0.5
Etheostoma fusiforme 0.0 0.0 0.0 0.0 0.1 0.0
Aphredoderus sayanus 0.0 0.0 0.1 <0.1 0.0 0.0
*Trinectes maculatus 0.2 0.4 2.2 1.5 0.6 0.1
*Anguilla rostrata 0.0 0.0 0.2 0.1 0.4 0.6
*Centropomus undecimalis 0.0 3.4 2.9 6.3 1.5 11.6
*Microgobius gulosus 0.0 0.0 0.0 0.0 0.0 0.1
*Mugil cephalus 0.0 0.2 5.1 2.2 2.5 2.3

TABLE 1.-Continued

*Brevoortia tyrannus 0.0 0.0 0.0 0.0 0.0 0.2
*Diapterus olisthostomus 0.0 0.0 0.0 0.6 3.7 0.8
*Tilapia aurea 21.5 1.6 6.8 9.5 15.1 2.2
**Clarias batrachus 0.3 0.0 0.1 0.0 0.3 0.0
* Ctenopharyngodon idella 0.0 0.0 0.0 0.0 0.1 0.0
Total number of
species collected 27 23 31 27 28 25
*Marine species
* Exotic species


RESULTS-A total of 37 species of fish were collected from the river proper
(Table 1). Indigenous freshwater species found in the main channel totaled 27
and represented 12 families. Along with the freshwater forms, seven marine
species and three non-indigenous species were collected. No endangered or
threatened species were documented. Centropomus undecimalis, a marine
species, was the only fish collected that was of special concern status.
No catastrophic events such as phosphate waste spills, severe drought or
flooding occurred during the study period. Seasonal hydroperiod changes and
periodic release of water from Lake Hancock resulted in inconsistent environ-
mental conditions which caused variable data. Since the assumption of nor-
mality could not be made, comparisons between stations (Table 2) were ana-
lyzed non-parametrically (Kruskal-Wallis Test).
TABLE 2. Peace River sample station comparisons of species richness, diversity (H'), numerical
abundance (CPUE) and biomass, 1983-88.

Number Median Median Median CPUE Median Biomass
Station of Samples Richness H' (fish/minute) (kg/minute)
Homeland 9 15.0 2.05* 5.8** 1.4
Ft. Meade 3 17.0 2.29 3.4 1.0
Wauchula 14 15.5 2.20* 3.2 1.0
Gardner 12 13.0 2.28* 2.1 0.7*
Nocatee 9 14.0 2.18* 2.9 1.0
Ft. Ogden 10 11.0** 1.99* 1.6* 1.1
* Significant difference between other stations to p < 0.05.
* *Significant difference between other stations to p < 0.025.

Total number of species collected at all stations ranged from 23 to 31
(Table 1) and species richness per sample varied from 9 to 20. Significantly
lower richness occurred at the Fort Ogden station (p <0.025). Median rich-
ness was not significantly different among the other stations (Table 2). Species
diversity, H', varied from 1.09 to 2.55 and was not correlated with species
richness (R= 0.43), and H' was significantly different between stations
(p<0.05). Median H' was low at Homeland (2.05, increased downstream
(Ft. Meade-2.29, Wauchula-2.20, Gardner-2.28) and decreased as the river
became tidally influenced (Nocatee-2.18, Fort Ogden-1.99). Median CPUE
was highest at Homeland, 5.8 fish/minute, and lowest at Fort Ogden, 1.6
fish/minute. CPUE at the middle four stations varied from 2.1 to 3.4 fish/
minute and were not significantly different. Biomass was not significantly
different between stations except for Gardner which was lowest at 0.70 kg/
minute. Biomass for the other stations ranged from 1.0 to 1.4 kg/minute.
Fishes abundant at all stations were Lepisosteus platyrhincus, Tilapia
aurea, Micropterous salmoides and several Lepomis spp. (Table 1). Abun-
dance of Lepisosteus osseus, Centropomus undecimalis and Ictalurus puncta-
tus were higher at the three downstream stations. Ictalurus catus was abun-
dant only at the Fort Ogden station. The presence of Notropis petersoni,
Notropis maculatus and Labidesthes sicculus appeared to be related to water
quality and were considered indicative of favorable biotic conditions. Notro-

No. 4, 1990]

pis petersoni was most abundant at Fort Meade, Wauchula and Gardner.
Abundance of Labidesthes sicculus was higher at Wauchula and Gardner
than at other stations.
DIsCUSSION-The freshwater fish fauna of the Peace River is depauperate
in species richness; which is primarily a result of the natural zoogeography of
peninsular Florida (Gilbert, 1987). Review of earlier Peace River studies in-
fers that anthropogenic influences may have reduced species richness during
recent times. Records from FGFWFC (1963), Ware and Fish (1969), Chap-
man (1973), Texas Instruments (Estevez et al., 1981 and Layne et al., 1977)
documented 11 freshwater species not collected in the main channel during
this study. Several of these species were collected by Champeau and co-work-
ers (1988) in tributaries exhibiting higher water quality than the Peace River
proper. It is probable that habitat requirements for these species are not cur-
rently being met in the main channel and these species have been either
reduced to less impacted tributaries or extirpated from the system.
Besides cultural degradation of aquatic habitat, human introduction of
non-indigenous fishes has also affected the ichthyofauna. Historical records
(FGFWFC, 1963; Buntz and Manooch, 1968; Ware and Fish, 1969) infer
that Tilapia aurea, an African cichlid, invaded the Peace River between 1963
and 1967. Buntz and Manooch (1968) documented the rapid expansion of
Tilapia aurea in several Polk County lakes from 1961 to 1968. Migration to
the Peace River most likely occurred from these upper-basin lakes. Tilapia
aurea has become well established throughout the river and is a significant
component of the community. These omnivorous filter-feeders exploit areas
of Peace River where algal and detrital biomass are high. Tilapia aurea is
opportunistic and capable of surviving dissolved oxygen levels that are intol-
erable to most indigenous species. Dominance of Tilapia aurea in other Flor-
ida systems has been associated with poor water quality and low biotic integ-
rity (Foote, 1977). The ability of Tilapia aurea to exploit severely polluted
habitats is well-documented; however, the degree of displacement of native
fishes by Tilapia aurea in higher quality habitats is poorly understood (Noble
et al., 1975; Noble and Germany, 1985; Shafland and Pestrak, 1983;
Shafland and Metzger, 1986). Competition, predation by piscivores and al-
teration of energy flow thereby changing trophic structure are possible im-
pacts of Tilapia aurea on native ichthyofauna.
Clarias batrachus became established in the Peace River between 1973
and 1977, although the route of initial river invasion is not clear. This species
was not abundant in the samples and probably does not have a significant
impact on the fish community. One specimen of Ctenopharyngodon idella
was collected that probably escaped from a headwater lake where stocking
was utilized for aquatic plant control.
Several marine species were found in the Peace River. Centropomus unde-
cimalis and Mugil cephalus were most common and were collected at all but
the uppermost station. Centropomus undecimalis ranged from 1 to 12 kg in
weight, and this piscivore is a competitor with Micropterus salmoides, Lepi-

[Vol. 53



sosteus spp. and Amia calva. Centropomus undecimalis was most abundant
in the lower river and was commonly collected from habitats incorporating
deep water, flow and dense cover. Trinectes maculatus was abundant at all
stations where sandy substrates existed. Other marine species appeared to be
transients with the exception of Anguilla rostrata, a catadromous eel.
Two components of degraded water quality that appeared to affect the
fish community most were high turbidity and unstable dissolved oxygen.
High concentrations of phytoplankton in Lake Hancock effluent results in
elevated levels of suspended organic matter and biological oxygen demand
loading of the upper river (Hand et al., 1988; Estevez, 1981). High turbidity
and low dissolved oxygen directly impact fish communities by displacing in-
tolerant species. Tilapia aurea, Lepisosteus spp. and Amia calva became
dominant since these species were able to exploit stressed conditions.
Seasonal rainfall patterns and variable discharge from Lake Hancock re-
sulted in fluctuations in diversity and species composition; however, these
data indicate a pattern of differentiated fish assemblages from upper to lower
stations. These differences are a result of pollution-loading of the upper river
rather than a function of natural longitudinal zonation. Consistently poor
water quality at the Homeland station resulted in low diversity; however, this
area supported a high density of fish. Lepisosteus platyrhincus and Amia
calva were dominant predators supported by a prey base consisting of Tilapia
aurea and Lepomis spp. High fish density resulted from high algal biomass
exhibited in the upper river. Low diversity and dominance of fishes tolerant
to unstable dissolved oxygen demonstrated poor water quality in the upper
river created biotic disturbances that greatly affected the fish community.
Physical and biotic conditions became less stressful downstream of Home-
land. The Fort Meade station is 35 km downstream of Lake Hancock, (14 km
below Homeland) and improved conditions were evidenced by increased di-
versity and higher abundance of Notropis petersoni and Micropterus sal-
moides. This area does not receive dilution from major tributaries, and it is
probable that biotic conditions are occasionally unstable. Reduced stress was
evident at the Wauchula station 35 km downstream of Fort Meade. Increased
diversity and more complex community structure indicated that habitat con-
ditions were consistently more favorable than upstream.
Four major and several minor tributaries enter the river between Fort
Meade and Wauchula. Dilution from these inputs improves water quality
which allows for more fish species to exist. Downstream 53 km, the Gardner
station was influenced by input of relatively unpolluted water from Charlie
Creek and seven smaller tributaries. Biomass estimates indicated that carry-
ing capacity was lowest in this area; however, species diversity was high.
Dilution of upstream loadings of chemical nutrients and suspended organic
matter resulted in lower fish production while higher quality habitat pre-
vented dominance and allowed for good equitability of species.
Tidal influence on water flow at the Nocatee and Fort Ogden stations
created biotic conditions dissimilar from observations upstream. Species rich-

No. 4, 1990]

ness, H', and CPUE decreased while fish production (biomass) was un-
changed. Insectivorous and planktivorous species were scarce from the lower
river while omnivores were abundant. Large piscivores (Lepisosteus spp.,
Centropomus undecimalis, and Micropterus salmoides) that could utilize a
prey base consisting primarily of Tilapia area and Ictalurus spp. dominated
the community. This community structure resulted in decreased fish density
while maintaining higher biomass.
CONCLUSIONS-Cultural impacts have significantly affected biotic condi-
tions of the Peace River system. Analysis of fish communities indicates the
upper (35 km) and lower sections (35 km) showed greater impact than the
middle section (125 km). These impacts are believed to be expressions of
pollution from headwater lakes and streams. Dilution from less polluted trib-
utaries improved biotic conditions in the middle section. Agricultural activi-
ties and phosphate mining within the drainage basins of these streams is in-
creasing and wise land management practices must be mandated for their
future protection. Tributaries already affected by mining should be re-
claimed to re-establish flow of high quality water to the main channel. Treat-
ment of effluent from Lake Hancock and Peace Creek by diversion to created
wetlands would improve biotic conditions throughout the river's course.
The Peace River fish community recovered from catastrophic events in
the past (Ware and Dequine, 1967; Ware, 1969; Chapman, 1973) and re-
sponds favorably to improved water quality. A holistic, long-term solution to
improve the Peace River involves many factors such as ecologically-sound
phosphate land reclamation, municipal and industrial wastewater manage-
ment, urban and agricultural stormwater management, flood control, lake
restoration, and regulation of land use. Protection and enhancement of the
river's aquatic resources are possible if these factors are incorporated into a
comprehensive basin management program.

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Florida Sci. 53(4): 302-311. 1990.
Accepted: February 23, 1990.

No. 4, 1990]

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