### Evaluating the effects of restor ation of subtropical oligohaline marshes on abundance and habitat use by juvenile snook, Centropomus undecimalis and associated fish communities.

Final Report to Charlotte Harbor National Estuary Program

June 2005

Principal Investigator: Aaron Adams, Center for Fisheries Enhancement, Mote Marine Lab

### 2 NOTE : This project was designed to measure creek fish assemblages in two types of creeks – creeks with significantly degraded upland drainages, and creeks with slightly altered upland drainages – and to determine the effect of habitat restoration in the upland drainages of the latter creeks on juvenile snook and other fishes. This would have provi ded a relatively rare beforeafter comparison of restoration effects. Ho wever, Florida Department of Environmental

Protection did not conduct the rest oration as planned. Thus, this report focuses on the effect of upland habitat degradation on mangrove creek fi sh assemblages in Charlotte Harbor.

Introduction Florida’s southwest coastline has been drastically altered for development, water management, agriculture, mining, and mosquito c ontrol purposes (references cited in Lin and Beal, 1995; Poulakis et al., 2002) . Historically, during the rai ny season, water would inundate vast stretches of upland habitats (wet and mesic pine flatwoods, hydric hammocks, and coastal tropical hammocks) and drain as slow, overl and sheetflow to oligohaline and mesohaline marshes at the upper reaches of the tidal estuarine system. In areas with larger drainage basins,

surficial flows were concentrated into tidal cr eek systems, creating a permanent flow corridor between upland salt ponds and tidal marshes. During the dry season, we t prairies and hydric hammocks dry-out, seasonally removing the corridor between upl and salt ponds and tidal marshes. In larger drainage systems, tidal creeks remain connected to the upla nd salt-water ponds. Anthropogenic alterations of freshwater flows into estuaries are of particular concern to resource managers because such changes imp act estuarine ecology (Sklar and Browder, 1998;

### 3 reviewed in Beach 2002). Freshwat er flow is a major ecological st ructuring factor in estuaries, influencing abundance and distribu tions of vegetation, and of inve rtebrates and vertebrates that use estuaries for some or all of their life cycles . The increase in impervious surfaces and loss of

wetland habitats associated with coastal development alter the source, timing, and velocity of freshwater flows, which influences salinity pa tterns (Sklar and Browder 1998). Whereas some organisms can tolerate wide range s in salinity, most species have narrow salinity tolerances or migrate to remain in a pref erred salinity range (Montague and Ley 1993, Sklar and Browder 1998), thus altering habitat use patt erns. When > 10% of a waters hed’s acreage is converted to impervious surface, the water bodies become seriously degraded, and are less diverse, productive, and stable (reviewed in Beach 2002). Lower organism abundances, lower recruitment, and shifts in dominant species of ten result from high pulse s in freshwater runoff (Sklar and Browder 1998, reviewed in Beach 2002, Beever and Chamberlain 2002, Wyda et al. 2002). With 25% of United States coastal habita ts expected to be developed by 2025 (14% of coastal habitats had been developed by 2002) (Beach 2002), there is an exigent need to understand how habitat alterations impact fish es so that appropriate conservation and management measures can be enacted. This is esp ecially true in Florida, with one of the fastest growing populations in the United States. Relative to many other estuar ies Charlotte Harbor habitats remain in good condition – much of the mangrove shoreline is intact and government owned, and s eagrass coverage has not changed significantly in ten years of monitori ng. Increasingly rapid coastal development, however, threatens to alter the estu ary’s watershed, thus altering fres hwater flow into the estuary. In fact, habitat-associated effects of such alte rations are becoming evident in some locations.

This combination of unaltered and altered habita ts makes Charlotte Harbor a perfect location for

### 4 studying the effects of habitat alteration on fish-habitat interacti ons, and formulating management strategies to cons erve estuarine habitats. Although the decline in coas tal fish populations has larg ely been attributed to overfishing, degradation of fish nur sery habitats has likely increased larval and juvenile mortality and thus contributed to population declines. Oligohaline creeks and upl and salt-water ponds are essential habitats for many young-of -the-year marine finfish and shellfish (McMichael et al., 1989; Peters et al., 1998; Baltz et al., 1998; Geary et al., 2001; Poulakis et al., 2002). The recruitment success of many tropical estuarine fishes, such as snook, Centropomus undecimalis and tarpon, Megalops atlanticus that have evolved life-hist ories based on a wet/dry season depend greatly upon access to oligohaline marshes (Poulakis et al., 2002); the recruitment of snook and tarpon larvae to creeks and ponds coincides with the wet season, when they are able to ride high tides into the flooded uplands. The sha llowness of creeks and isolation of ponds in the dry season provides protection from predation by large fishes. As they grow and undergo ontogenetic shifts in diet and habitat requirements, these fi shes migrate downstream (and eventually to the open estuary and ocean), spendi ng portions of their life history in creek and estuarine habitats. Degradation of these juvenile habitats is of special concern giving the significant economic importance of these species in the saltwater recreati onal fishery (statewide,

the Florida saltwater recreatio nal fishery is estimated to be worth $8.5 billion annually). Research to determine the effects of upla nd development and subsequent alterations of

freshwater flow on estuarine fishes is urgently needed. This is es pecially true for juvenile life stages of economically important species, such as common snook, Centropomus undecimalis and red drum, Sciaenops ocellatus , that comprise the recreati onal fishery that generates approximately $8.5 billion annually in Florida. This research ex amined habitat use patterns of

### 5 juvenile snook and red drum, and of the overall cr eek fish assemblages in two types of creeks – those with altered upland drainages (degraded) , and those with relativ ely undeveloped drainages (natural) – to determine the effects of freshwater flow alterations. This research tested three hypotheses:

• H 1 

### : Oligohaline creeks are important juvenile habitats for juvenile snook and red drum

• H 2 

### : Degraded upland habitats alter freshwater fl ow that degrades the habitat quality of estuarine mangrove creeks as juveni le habitats for snook and red drum

• 

### H 3 

### : Degraded upland habitats alter freshwater fl ow that degrades the habitat quality of estuarine mangrove creeks, and these changes are reflected in creek fish assemblages

Methods Study Location

Charlotte Harbor is a 700 km 2 

### coastal plain estuarine system in southwest Florida (Hammett 1990) (Figure 1). The Peace, Myakka, and Caloos ahatchee rivers, as well as many smaller creeks throughout the drainage, tr ansport large amounts of the fres h water into the harbor. The

harbor is connected to the Gulf of Mexico through Boca Grande Pass, San Carlos Bay, and three

smaller inlets. The climate of Charlotte Harbor is subtropical; mean seasonal water temperatures range from 12o to 36o C, and freezes are infr equent (Poulakis et al. 2003). Anthropogenic development within the watershed has stressed the estuarine system; however, compared with many other estuaries (e.g., Chesapeake Bay, Ta mpa Bay), Charlotte Harbor has remained relatively unspoiled (> 80% of mainland shor elines under protection; R. Repenning, Florida Department of Environmental Protection, pers . comm.; Hammett 1990; CHNEP 1999). Seagrass flats (262 km 2 

### ; Sargent et al. 1995) and mangrove shorelines (143 km 2 

### ; L. Kish, Florida Fish and

### 6 Wildlife Research Institute, unpubl. da ta) continue to thrive as th e dominant habitats within the

estuary.

Sample Design From February 2003 through October 2004, four mangrove-fringed estuarine creeks, each approximately 2 km long, on the eastern shorelin e of Charlotte Harbor, FL (Figure 1) were sampled every other month using a 22 x 1.2 m cen ter bag seine with 3.2 mm mesh. Each creek was divided into three equal st rata (upper, middle, lower) for sampling, with five samples per stratum, and thus 15 samples per creek, per samp le period. Sample locations within each creek stratum were selected haphazardly in each month. For each sample, the net was set in a semicircle against a mangrove shorelin e and pursed to force fish into the bag, all fish were identified to the lowest taxon possible, the first 25 indi viduals of each taxon were measured (standard length) and the remainder counted, and temperat ure, salinity, and dissolved oxygen recorded

with a handheld YSI 556 MPS. All fish were retu rned to the water at th e site of capture. All creeks are within the same estuarine hydr ological zone (Poulaki s et al. 2003), so are unlikely to differ greatly in larval supply. Fo r the purposes of this study, the two northernmost

creeks were considered ‘natural ’: their morphology remains largely intact except for remnant mosquito ditches (compared to 1953 aerial photos), and their upland drainages are undeveloped. Creek widths range from 2 m in narrow passes to >60 m in wider bays, depth is shallow (< 0.5 m except in narrow passes where depths reach 1m), shorelines are lined entirely by red mangroves Rhizophora mangle , and bottom is mixed mud and sand. The submerged aquatic vegetation in the upper stratum is entirely Ruppia maritima, whereas the middle and lower strata are dominated by Halodule wrightii . The two southern creeks, located 16 km south of the natural

### 7 creeks, are considered ‘degraded’: their dr ainages and wetlands have been altered for development, creating impervious surfaces and alte ring freshwater flow regimes. The altered flow regimes cause short, pulsing hydroperiods limited to the immediat e creek with little overland sheet flow. The bottoms are mostly hard sand, and the submerged aquatic vegetation ( R. maritima and H. wrightii ) is patchy and limited to the lower two-thirds of the creeks. The creeks are narrow (mean = 5 m) for the upper two- thirds, and have wider bays (60 m) only in their extreme lower portions. Narrow sections ar e scoured to > 2 m depth with undercut banks, and greatly reduced width of the inter tidal mangrove prop root habitat.

Data Analysis

Taxa were defined as residents (R), transients (T), and juveniles (J), based upon frequency of occurrence, habitat requirements (Robins et al. 1986) and dominant life stage when in the creeks: residents were present in > 200 samples (N = 547) and had creek-associated habitat requirements, transients were ma rine or estuarine species able to use numerous habitats and present in < 201 samples, and taxa were classi fied as juveniles when > 90% of individuals captured were juveniles. Taxa were define d as freshwater (F) or non-native (N) based upon Robins et al. (1986) and Page and Burr (1991). Mean density (no. fish/m 2 

### ) and frequency of occurrence (total number of samples in which the taxon occurred) were ca lculated by creek and zone for each taxon, and examined using cluster analysis (standardized, Average linkage method, Euclidean distance) to determine the extent of (dis)similarity among fish assemblages in the different creeks (Wilkinson et al. 1996). If the classification of creeks based upon appare nt habitat quality was co rrect, the expectation

was that creeks would be most similar within type (i.e., North Silcox and South Silcox zones

### 8 would group together (natural creeks), and Culvert Creek a nd Yucca Pen would group together (degraded creeks)). Density and frequency of occurrence for the most abundant non-native species, Cichlasoma urophthalmus , were examined by creek to determine the extent that presence of this species differed by creek type (natural vs degr aded). Frequency of occurrence and abundance were examined graphically to determine the ex tent that freshwater and non-native species occurrence were related to salinity (data were insufficient (i.e., no freshwater or invasive species were captured in most samples) to warrant regr ession analysis). Since frequency of occurrence and abundance were low for these species, data we re summed for all species within each group. For non-native species, C. urophthalmus were excluded from regressi on analysis because of their extreme salinity tolerance in their native ra nge (0 – 26ppt, Morales-Gó mez et al. In Press).

To determine whether creek characteristics in fluenced use of creek habitats by juvenile

C. undecimalis and S. ocellatus , density data were examined by creek and zone. Because many samples contained no individuals of these sp ecies, density data did not meet normality assumptions required for parametric analysis, so densities were examined separately by creek and zone with Kruskal-Wallis non-parametr ic ANOVA (Sokal and Ro hlf 1995). Lengths (measured as standard length) of C. undecimalis and S. ocellatus were log-transformed and examined with a two-way ANOVA, with creek and zone as factors. Because no C. undecimalis or S. ocellatus were captured in the upper zone of Yucca Pen, Yucca Pen was excluded from this analysis (The effect of sa linity on size distributions of C. undecimalis and S. ocellatus were examined with linear least squares regression. Length data were log-transformed prior to analysis.

### 9 Effects of hurricane Charley In August 2004, Category 4 hurrica ne Charley traversed Charlotte Harbor, the eastern eyewall passing over the study creeks. Sampling of the natural creeks was completed 3 days prehurricane, and was repeated from 13 through 21 days post-hurricane. Normal sampling in natural and degraded creeks resumed in October, 2 months post-hurricane.

Results Salinity (Figure 2), temperature (Figure 3), and dissolved oxygen (Figure 4) varied seasonally.

Seasonal trends for each variable were simila r among creeks. Salinity maxima and minima occurred in degraded creeks. Yucca Pen experien ced the longest periods of low salinity (in eight of ten sample periods, salinity was < 10 ppt in middle and lower zones). Surface and bottom salinity, temperature, and dissolved oxygen were similar, so were combined for analysis. When salinity was compared by creek and zone, there were significant creek and z one effects (Table 1, Figure 5), but the trend was simila r in all creeks – salinity decreased from lower to upper zones. Temperature differed among creeks, but not by zone (Table 1, Figure 6), whereas dissolved oxygen varied differed by creek and zone (Tab le 1, Figure 7). Di ssolved oxygen minima occurred in the degraded creeks. Temperatur e and dissolved oxygen were negatively correlated for North Silcox (Pearson r 2 

### = -0.34, p < 0.001, df = 1), South Silcox (r 2 

### = -0.57, p < 0.001, df = 1), and Yucca Pen (r 2 

### = -0.41, p < 0.001, df = 1), but not for Culvert Creek (p > 0.1). Salinity and temperature were weakly negatively correlated for South Silcox (r 2 

### = -0.28, p < 0.01, df = 1) and Yucca Pen (r 2 

### = -0.22, p < 0.05, df = 1), but not for Culv ert Creek or North Silcox (p > 0.1). Salinity and dissolved oxygen were positively correlated for the natural creeks (North Silcox r 2 

### = 0.30, p < 0.001, df = 1; South Silcox r 2 

### = 0.44, p < 0.001, df = 1), but not for the degraded creeks

### 10 (p > 0.1). A total of 205,992 fish representing 79 taxa (f ishes were identified to the lowest taxon possible, resulting in assignation of individuals to 60 species, 14 genera, and 5 families) was captured in 547 samples (Table 2). Of these ta xa, 27 were classified as residents, 10 as transients, 18 as juveniles, 12 as freshwater spec ies, and four as non-native species. The seven most abundant species were resident s, and were present in all cree ks. Juveniles of recreationally important Centropomus undecimalis and Sciaenops ocellatus were ranked 10 and 14 in total abundance, respectively, and were also captured in all creeks. The most abundant invasive species, Cichlasoma urophthalmus , was ranked 26 in total abunda nce, higher than the native freshwater taxon, Lepomis sp., which was ranked 32 in to tal abundance, although both groups

were recorded in all creeks. Density of all species combined and species richness tended to be gr eater in the natural creeks (North Silcox and South Silcox) than in the degraded creeks (Culvert Creek and Yucca Pen) during the wet season, and sim ilar during the dry season (Figur e 8). When species densities and frequency of occurrence by creek and zone were examined with cluster analysis, fish assemblages in natural creeks were most similar to one another, and most dissimilar to degraded creeks (Figure 9). Although freshwater species were captured in all months, trends in abundance and frequency of occurrence coincided with the wet season, with peaks in June, August, and September (Table 3, Figure 10). Both total abundance (R 2 

### = 0.49, p < 0.01) and frequency of occurrence (R 2 

### = 0.46, p < 0.01) of all freshwater species combined were negatively related to salinity. The most common freshwater fishes were Lepomis spp and Micropterus spp. (Figure 11), which were captured mos tly in salinities < 6ppt ( Lepomis spp. mean salinity at capture =

### 11 3.51, se = 0.56; Micropterus spp. mean salinity = 5.93 ppt, se = 1.69). Lepomis spp were seasonally present in all creeks, and were most abundant in South Silcox (38% of Lepomis spp. individuals), followed by North Silcox (29%), Culvert Creek (26%), and Yucca Pen (7%). Micropterus spp were present seasonally only in Yucca Pen (62% of Micropterus spp. individuals) and Cu lvert Creek (38%). Non-native species were not captured in samples until August 2003 (the fourth sample period of the study). Although there was no rela tionship between salinity and abundance (p > 0.1) or frequency of occurrence (p > 0.1) of non- native species, their seas onality of occurrence followed high freshwater flows associated with the wet season. The most common and most abundant non-native species was Mayan cichlid, Cichlasoma urophthalmus , which occurred in

all creeks but was most abundant in Culvert Cree k (Table 4), and was ca ptured in all months after August 2003. Oreochromis mossambicus and Hemichromis bimaculatus were present seasonally in low abundance only in North Silc ox and South Silcox creeks: each species was captured in August 2003, O. mossambicus was captured again in October 2003, and February and June 2004, and H. bimaculatus again in June 2004.

Juvenile C. undecimalis were captured in all months, a nd occurred in all zones in North Silcox, South Silcox, and Culvert Creek, but were absent from the upper zone and rare in the middle zone of Yucca Pen (Figure 12). Temporal trends in density varied among creeks and zones. Densities differed when examined by creek and zone (Table 5). Within creeks, densities tended to be highest in the lower zone and le ast in the upper zone in Culvert Creek, Yucca Pen,

and North Silcox. This trend was reversed in Sout h Silcox. Within zones, densities were similar among all creeks in the lower zone, but were high est in South Silcox and least in Yucca Pen in middle and upper zones (snook were absent and rare in upper and middle zones, respectively, of

### 12 Yucca Pen). There was no relationship between salinity and C. undecimalis abundance or size (p > 0.1). Samples were dominated by small C. undecimalis in all creeks (Fi gure 13), with postsettlers occurring in late summer and early fall . Although there was a significant creek x zone interaction effect (Table 6), all creeks exhibited the same tre nd in size – lengths were greatest in the middle zone (Figure 14). (Yucca Pen was remove d from length analyses because no juveniles were captured in the upper zone , and relatively few were capture d in middle and lower zones.)

Juvenile S. ocellatus were captured almost entirely from October through February, and were in greater densities in No rth Silcox and South Silcox than Culvert Creek and Yucca Pen in all zones (Figure 15, Table 7). Juvenile S. ocellatus were rare or absent from upper zone of Culvert Creek and Yucca Pen. Within creeks, the trend was for densities to be greatest in the lower zone and least in the upper zone. Althoug h there was no significant relationship between

S. ocellatus density and salinity, within each creek between 72% and 87% of samples that contained juvenile S. ocellatus were in salinities between 10 and 28 ppt. Samples were dominated by small S. ocellatus (Figure 16), with post- settlers first present in October. In Culvert Creek and Yucca Pen, where S. ocellatus were less abundant, fish size was positively related to salinity (CC – R 2 

### = 0.57, F = 121.64, p < 0.001: YP – R 2 

### = 0.27, F = 30.199, p < 0.001), but there was no such relationship in North and South Silcox creeks (p > 0.1). Yucca Pen was removed from length analysis because of very low or no catches in all zones. The significant creek x zone interaction effect (T able 8) was due primarily to increases in size from lower to upper zones in Culvert Creek and North Silcox, whereas fish size was similar in all zones of South Silcox (Figure 17).

### 13 Effects of hurricane Charley Sampling of natural creeks was completed 3 days pre-hurricane, was repeated from 13 through 21 days post-hurricane. Normal sampling in natura l and degraded creeks resumed in October, 2 months post-hurricane. Hurricane Charley might be considered an acute disturbance because its direct effects (high winds, rainfall, storm surge) lasted < 12 hr. However, low dissolved oxygen from decomposition of leaves from defoliated ma ngroves lasted for > 1 wk. Thus, Charley is defined as a press disturbance (Glasby and Underwood 1996, Lake 2000). Above-water impacts were severe, with all mangrove branches > 6 m height completely defoliated or broken and partial defoliation of shorter mangroves. With in creeks, damage incl uded scouring of narrow sections of creeks, moderate redistribution of sediments, complete loss of SAV, high turbidity, and reduction of dissolved oxygen to > 1 ppm (purportedly due to mangrove leaf decomposition). The direct effects (high winds, rainfall, storm surge) of Hurricane Charley lasted < 12 hr. Above-water impacts were severe, with all mangrove branches > 6 m height completely defoliated or broken and partial defoliation of shorter mangroves. Within creeks, damage included scouring of narrow sections of creeks, moderate redistribution of sediments, complete loss of SAV, high turbidity, a nd reduction of dissolved oxygen to > 1 ppm. Since the low dissolved oxygen (purportedly fr om decomposition of leaves from defoliated mangroves) lasted for > 1 wk, the indirect eff ects of the hurricane will likely have greater impact. The passage of the hurricane was noted by th e abrupt decline in species richness and abundance 13 days post-hurricane sampling in na tural creeks thus indi cating a strong immediate effect (Figure 18). A rapid response was suggest ed by a rapid recovery of species richness and abundance by 21 days post-hurricane, after dissolv ed oxygen levels began to recover toward pre-

### 14 hurricane levels. However, sampling 2 months post-hurricane indicate d a delayed response – species richness was similar to pr e-hurricane levels, but density de clined. The apparent sluggish recovery may indicate a lag effect, whereby eff ects of physiological stress from depression of DO and salinity and increase in turbidity were dela yed. Sampling in the cree ks continues so that longer-term hurricane effects can be determined.

Discussion This research provided urgently needed quant itative information on the affect of habitat degradation on fish assemblages associated with mangrove creeks, and a quantitative estimate on the effect of this degradation on the nursery va lue of creek habitats fo r economically important fishes. That the degradation was primarily asso ciated with development of upland drainages of mangrove creeks and associated alterations of freshwater flow into the creeks is especially

notable. Anthropogenic alterations of freshwater flows into estuaries are of particular concern to resource managers because such changes imp act estuarine ecology (Sklar and Browder, 1998; reviewed in Beach 2002). Freshwat er flow is a major ecological st ructuring factor in estuaries, influencing abundance and distribu tions of vegetation, and of inve rtebrates and vertebrates that use estuaries for some or all of their life cycles . In this study, Culvert Creek and Yucca Pen were considered degraded because their upland draina ges have been drastica lly altered, with an increase in impervious surface. For Yucca Pen, freshwater flows from large upland areas are now funneled into the creek, cau sing extensive periods of lo w salinity and making this poor habitat for estuarine fishes (e.g., low abundance and species richness in upper and middle zones). Culvert Creek suffers from the ‘faucet effect’, wh ereby creek salinities and flow rates fluctuated

### 15 rapidly with local rainfall: hi gh rainfall (faucet ‘on ’) created near-fresh water conditions the length of the creeks; low rainfall (faucet ‘off’) allowed mesohaline conditions to creek headwaters. Prior to these alterations, it is like ly the hydrologic conditions were similar to those of the natural creeks such that gentle, low, flat slopes provided for slow overland sheet flow of surface waters, which were retained for extend ed duration within wet and mesic slash pine flatwoods during wet season, but were dry dur ing dry season. The flows caused salinity gradients that provided impor tant habitat for fishes. The increase in impervious surfaces and loss of wetland habitats associated with coastal development alter the source, timing, and velocity of freshwater flows, which influences salinity patterns (Sklar and Browder 1998). Whereas some organisms can tolerate wide ranges in salinity, most species have narrow salinity tolerances or migrate to remain in a preferred salinity range (Montague and Ley 1993, Sklar and Browder 1998), thus altering habitat use patterns. When > 10% of a watershed’s acreage is convert ed to impervious surf ace, the water bodies become seriously degraded, and are less divers e, productive, and stable (reviewed in Beach 2002). In this study, it is estimat ed that the proportion of drainages of Culvert Creek and Yucca

Pen have exceeded this 10% alteration thre shold. Lower organism abundances, lower recruitment, and shifts in dominant species of ten result from high pulse s in freshwater runoff (Sklar and Browder 1998, reviewed in Beach 2002, Beever and Chamberlain 2002, Wyda et al. 2002). In this study, although the ov erall temporal trends in salin ity, temperature, and dissolved oxygen (DO) in the creeks were similar, the de graded creeks experienced the most extreme variation. These extreme variations likely cont ributed to the lower ha bitat quality of the degraded creeks. In addition, salinity and DO mi nima were lowest in the degraded creeks.

The differences in abiotic factors between natural and degraded creeks likely caused the

### 16 differences in species richness, total fish a bundances, and abundances of most species were higher in the natural creeks, t hus corroborating previous resear ch elsewhere on the effects of

freshwater flow alterations. The lack of submerged aquatic vegetation in the upper and lower zones of the degraded creeks further underscores the effects of freshwater flow alterations.

With 25% of United States coastal habitats expected to be developed by 2025 (14% of coastal habitats had been developed by 2002) (Beach 2002), there is an exigent need to understand how habitat alterations impact fish es so that appropriate conservation and management measures can be enacted, and this st udy contributes this im portant information for Charlotte Harbor. Moreover, since Charlotte Har bor resembles much of the Florida coastline in that coastal habitats are being drastically al tered for development, water management, and mosquito control, the findings of this research are applicable elsewhere.

Habitat alteration often facilitates invasions by non-native species (Ross 1991, Courtenay and Williams 1992), and this appears to be the case in this study. Habitat quality of mangrove creeks, as defined by the extent of alteration in upland drainages, is an important factor in the

invasion success of Cichlasoma urophthalmus into Charlotte Harbor. It appears that upland habitat alteration (ponds and canals) may provide refuge from low temperatures and predation, thus harboring source populations for individuals to colonize estuar ine habitats. The presence of drainage ditches and artificial ponds that retain oligo- and meso-h aline water year-round (prior to anthropogenic alteration these ar eas were dry during the dry s eason), may provide sources of

recruitment into Charlotte Har bor’s estuarine habitats. Base d upon the findings of this study, Charlotte Harbor National Estuary Program has recently provided funds to the PI to address questions relating to invasive species in estuarine habitats, including: Does alteration of freshwater flows in upland hab itats increase invasion success of C. urophthalmus in estuaries?

### 17 Are C. urophthalmus established in Charlotte Harbor estuarine habitats or do altered upland habitats (artificial ponds and canals) provide upstream sources of new recruits? What invasion avenues are used by C. urophthalmus to access Charlotte Harbor estuarine habitats? Once invasion avenues are defined, future restoration efforts can include strategies to interrupt these avenues as part of the restoration process to he lp reduce the establishment of this species in estuarine habitats. Future research can then begi n addressing the extent of the ecological impacts

of C. urophthalmus on native species. Abundance and size ranges of juvenile s nook and red drum capture d during this study

indicated that overall habitat use patterns were the same, but that creek-specific characteristics likely influenced the quality of the creeks as juvenile habitats. For example, juvenile red drum were present in similar size ranges in all creek s during the same, distin ct time period. In addition, the general trend was for juvenile red dr um to move toward the upper zone as they grew. However, the high freshwater flows in Yucca Pen likely caused the absence of juvenile red drum in the upper zone and limited almost all red drum to the lower zone. In Culvert Creek, variable freshwater flows (i .e., the faucet effect) and ch annelized creek morphology likely limited red drum abundance. In contrast, the mo derated freshwater flows and extensive shallow

habitats of North and South Silc ox creeks appeared to be higher qua lity habitats for juvenile red

drum. Since the expectation is that habitat degrada tion can alter spatial and temporal patterns of habitat use by many species, change species co mposition (reviewed in Sklar and Browder 1998), and lower the quality of nursery habitats, it was expected that the natural creeks would also support more juvenile snook. This was true fo r Yucca Pen, where high freshwater flows likely limited juvenile snook use of the upper and middle zones. Surprisingly, however, juvenile snook

### 18 densities were similar among all other creeks. One possible reason for similar densities among

creeks is that the difference in habitat complexity between creeks made the snook more catchable in the degraded creeks. The natural creeks had extensive flooded areas of red mangrove proproots that were inaccessible to sampling with seines , even at low tide. In contrast, subtidal red mangrove prop root habitat in the degraded creeks was very limited at low tide, so sampling in the degraded creeks was more efficient. In other words, the probability of catching juvenile snook in the degraded creeks was higher than in the natural creeks. Although not measured in this study, the amount of creek habitat av ailable to juvenile snook was far greater in the natural than degraded creeks (Figure 1). Thus, even if densities of juvenile snook were similar am ong creeks, the total abundance of snook (density X total creek area) was far greater in North a nd South Silcox than in Culvert Creek or the lower zone of Yucca

Pen. Habitats that harbor high densities of juve niles have long been defined as nurseries, and

with this standard the creeks examined in this study would be considered nursery habitats. However, the extent to which the juveniles gr ow, survive, and successfully join the adult population must be determined be fore a habitat can be defined as a nursery. Thus, a more realistic standard for defining nurse ry habitats is to determine whet her juveniles from a particular habitat eventually cont ribute to the adult populations (i.e., demonstrate habita t connectivity).

This latter standard is of most use and of primary concern to resource managers. Therefore, although this study has shown that ju venile snook are present in si milar densities in one of the degraded creeks and the two natural creeks, the ra te at which these juve niles are successful at surviving to enter the adult population remains unknown. Based upon these findings, research is now underway to determine the extent that thes e creeks contribute snook to the adult population,

### 19 and thus determine the true nursery value of th ese creeks. Determining which creeks contribute more snook to the local population will aid in land acquisition and habitat management. In addition, findings will provide a framework for ex amining the effects of habitat degradation on juveniles of other species with similar life histories.

Hurricane Effects The accurate characterization of ecological distur bances such as hurricanes is important for structuring metrics of disturba nce effects. The frequency, in tensity, and duration provide a

measure of the disturbance. The effect is then a measure of the im pact of the disturbance on the system (i.e., abiotic and biotic co mponents), and is a measure of re sistance (ability of the system to withstand a disturbance, Lake 2000). The response is a measure of the recovery trajectory of the affected system (i.e., resilien ce – the ability of a system to recover from a disturbance (Lake 2000). Glasby and Underwood (1996) proposed that a system’s response be defined in similar terms to the disturbance – as either pulse (quick recovery) or press (slower recovery trajectory). Although the passage of hurricane Charley was c onsidered a pulse disturbance, the extended period of hypoxic and anoxic conditions that affected creek fishes was a press disturbance. Thus, a press response might be expected from the creek fish assemblages. In addition, interactions be tween disturbances, or between disturbances and ‘normal’ fluctuations must also be considered (White a nd Jentsch 2001). For example, normal seasonality

was found more influential on cora l reef fish abundances than hu rricanes (Letourneur et al. 1993, Adams 2001, Adams and Ebersole 2004). In this study, initial indications were that normal seasonal patterns continued after the immediate post-hurricane fluctuations: total abundance and species richness recovered within three weeks of the hurricane, s uggesting a pulse response. To

### 20 some extent, fishes are able to move out of impacted areas, and to return when conditions improve. This is especially true for fishes with mobile behavior, and less true of sedentary of site attached fishes. Moreover, some fishes ma y have behavioral adaptations to poor conditions such as those present after hurricanes. For example, dissolved oxygen levels in estuarine wetland and creek habitats are frequently >1.0 mg/L (Smith and Able 2003, this study), and some species have behavioral and physiological adaptations to these conditions (Smith and Able 2003). However, observations of aquatic surface re spiration, a sign of phys iological stress from low DO, by fishes during post-stor m sampling, and a leveling off of the recovery trajectory in October sampling (2 months post-hurricane) sugges t physiological stress, mo rtality, or long-term emigration due to extended duration of low DO. In addition, sampling in October 2004, and in spring 2005 (not reported in this manuscript) suggest a possible lag in recovery (lower than expected abundance of most species and lowe r species richness), thus indicating a press response. In addition, disturbance effect s differ between natural (e.g., hurricanes) and anthropogenic (e.g., freshwater flow alterations ) disturbances (Mackey and Currie 2001). Moreover, anthropogenic disturbances may interact with natural disturbances or alter system responses (White and Jentsch 2001). Continued sampling for one year after hurricane Charley (funded by a grant from National Science Founda tion) will provide the data necessary to determine: whether normal seasonal patterns have been influenced by th e hurricane (i.e., provide multiple years of pre- and post-hurricane data); if the ecological response was pulse (quick recovery) or press (longer recovery); and the eff ect of habitat degrada tion on fish assemblage response to the hurricane.

### 21 Management Applicability Given the increasing populations in many coastal regions, in corporation of anthropogenic impacts should be considered for any appropriately -scaled research or assessments. It is likely that anthropogenic changes will impact habitat type s differently, and thus impact fish life stages differently. If resource managers are going to make predictions about the response of coastal ecosystems to anthropogenic chan ges, the relative eff ects of anthropogenic changes on different

habitats and their associated fishes must be in corporated into their models. This study has underscored the impact of freshwater flow alte rations on estuarine habitats and associated species, and thus the importance of addressing th is type of habitat degr adation in management strategies. The ability to evaluate the success of habita t restoration projects is of both local and global significance due to widespread habitat loss and diversion of freshwat er, and the associated

decline in estuarine health. As human populations in coastal areas continue to increase, demands

on freshwater resources and coastal habitats wi ll increasingly alter the quantity, quality, and location of freshwater flow, resu lting in further degrad ation of oligohaline systems that provide habitats vital to estuarine and marine species. Quantification of the rela tionships between flow regimes and habitat quality of oli gohaline habitats is essential to long-term management of these

areas. Oligohaline marshes provide a vital link betw een terrestrial and es tuarine systems. As such, strategies for management of upland ha bitats must consider the implications of management actions on estuarine habitats and specie s. By defining the effects of freshwater flow alterations on mangrove creek hab itats in Charlotte Harbor, this research has provided managers with information needed to improve management pl ans. In addition, the fi ndings of this research

### 22 should help guide Florida Departme nt of Environmental Protection’ s restoration projects in the Charlotte Harbor Aquatic and St ate Buffer Preserve. How the restoration is implemented will influence how the sheet flow of fresh water over these areas will impact downstream areas, including mangrove and marsh habitats us ed as nurseries by estuarine fishes.

Literature Cited Adams, A.J. 2001. Effects of a hurricane on two a ssemblages of coral reef fishes: multiple-year analysis reverses a false snapshot in terpretation. Bull. Mar. Sci. 69(2):341-356. Adams, A.J. and J.P. Ebersole. 2004. Resistance of coral reef fishes in back reef and lagoon

habitats to a hurricane. Bu ll. Mar. Sci. 75(1):101-113. Baltz, D.M., J.W. Fleeger, C.F. Rakocinsk i, and J.N. McCall. 1998. Food, density, and microhabitat: factors affecting growth and recruitment potential of juvenile saltmarsh

fishes. Environ. Biol. Fish. 53:89-103. Beach, D. 2002. Coastal Sprawl: The Effects of Urban Design on Aquatic Ecosystems in the United States. Pew Oceans Commission. Arlington, VA. Beever, J. and B. Chamberlin. 2002. Freshwater inflow to Matlacha Pass performance measures for Gator Slough and Cpe Coral canals. S outh Florida Water Management District. Report. 5pp. Courtenay Jr., W.R. and J.D. Williams. 1992. Disp ersal of exotic species from aquaculture sources, with emphasis on freshwater fishes. p. 49-82. In A. Rosenfield and R. Mann (eds) Dispersal of Living Organisms Into Aquatic Ecosystems, Maryland Sea Grant Program, College Park, MD, USA. Geary, B.W., J.R. Rooker, and J.W. Webb. 2001. U tilization of saltmarsh shorelines by newly

### 23 settled sciaenids in a Texas es tuary Gulf Carib. Res. 13:37-49. Glasby T.M. and A.J. Underwood. 1996. Sampling to differentiate between pulse and press perturbations. Environ. Monit. Assessm. 42:241-252. Hammet, K. M. 1990. Land use, water use, str eamflow charateristics, and water quality

characteristics of the Charlotte Harbor infl ow area, Florida. U. S. Geological Survey Water Supply Paper 2359 A. Lake, P.S. 2000. Disturbance, patchiness, and dive rsity in streams. J. N. Am. Benthol. Soc. 19(4):573-592. Letourneur, Y., M. Harmelin-Vivien, and R. Ga lzin. 1993. Impact of hurricane Firinga on fish community structure on fringing reefs of Reunion Island, S.W. Indian Ocean. Environ.

Biol. Fish. 37:109-120. Lin, J. and J.L. Beal. 1995. Effects of mangr ove marsh management on fish and decapod communities. Bull. Mar. Sci. 57(1): 193-201. Mackey, R.L. and D.J. Currie. 2001. The diversity- disturbance relationship: is it generally strog and peaked? Ecology. 82(2):3479-3492. McMichael, R.H., Jr., K.M. Pe ters, and G.R. Parsons. 1989. Ea rly life history of the snook, Centropomus undecimalis , in Tampa Bay, Florida. North east Gulf Sci. 10(2):113-125. Montague, C.L. and J.A. Ley. 1993. A possible e ffect of salinity fluctuation on abundance of benthic vegetation and associated fauna in northeastern Florida Bay. Estuaries. 16(4):

703-717. Morales-Gómez, A.A., R. Chávez-López, J. Franco-López, M.S. Peterson and N.J. Brown- Peterson (in review) Ecol ogy of the Mayan cichlid, Cichlosoma urophthalmus Günther, in the Alvarado lagoonal system, Veracruz , Mexico. Gulf and Caribbean Research.

### 24 Page, L.M. and B.M. Burr. 1991. A field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Co. Boston. 432pp. Peters, K.M., R.E. Matheson, Jr., and R.G. Ta ylor. 1998. Reproduction and early life history of common snook, Centropomus undecimalils (Bloch), in Florida. Bull. Mar. Sci. 62(2):509-529. Poulakis, G.R., D.A. Blewett, and M.E. Mitchell. 2003. The E ffects of Season and Proximity to Fringing Mangroves on Seagrass-Associated Fish Communities in Charlotte Harbor, Florida. Gulf Mexico Sci. 21(2):171-184. Poulakis, G.R., J.M. and D.S. Taylor. 2002. Habita t use by fishes after tid al reconnection of an impounded estuarine wetland in the Indian River Lagoon, Flor ida (USA). Wetlands Ecol. Manag. 10:51-69. Robbins, C.R., G.C. Ray, and J. Douglass. 1986. A fi eld guide to Atlantic coast fishes of North America. Houghton Mifflin Co. Boston. 352pp. Ross, S.T. 1991. Mechanisms structuring stream fish assemblages: are there lessons from introduced species? Environmental Biology of Fishes 30:359-368. Sklar, F.H. and J.A. Browder. 1998. Coastal envi ronmental impacts brought about by alterations

in freshwater flow in the Gulf of Mexico. Environ. Manag. 22(4): 547-562. Smith, K.J. and K.W. Able. 2003. Dissolved oxygen dynamics in salt marsh pools and its potential impacts of fish assembla ges. Mar. Ecol. Prog. Ser. 258:223-232. Sokal, R.R. and F.J. Rohlf. 1995. Biometry. Tjird Ed. W.H. Freeman and Co. New York. 887pp. White, P.S. and A. Jentsch. 2001. The search fo r generality in studies of disturbance and ecosystem dynamics. Progr. Bot. 62:399-450. Wilkinson, L., G. Blank, C. Gruber. 1996. Desktop da ta analysis with Systat. Prentice Hall. NJ.

### 25 798pp. Wyda, J. C., L. E. Deegan, J. E. Hughes, and M. J. Weaver. 2002. The response of fishes to submerged aquatic vegetation complexity in two ecoregions of th e Mid-Atlantic bight: Buzzards Bay and Chesapeake Bay. Estuaries 25(1):86-100.

### 26 List of Figures Figure 1. Locations of study site s along the eastern shoreline of Charlotte Harbor, Florida. Figure 2. Mean (+/- SE) salinities of study creeks and zones by year and month. Only surface values are shown for graphical cl arity. Salinity was recorded during each sample. N = 5 for each creek-zone-month. Figure 3. Mean (+/- SE) temperatures ( o 

### C) of study creeks and zone s by year and month. Only surface values are shown for gr aphical clarity. Temperature was recorded during each sample. N = 5 for each creek-zone-month. Figure 4. Mean (+/- SE) disso lved oxygen (mg/L) of study cree ks and zones by year and month. Only surface values are shown for graphical clarity. Dissolved oxygen was recorded during each sample. N = 5 for each creek-zone-month. Figure 5. Mean (+/- SE) surface salinity (PPT) by creek and zone. Figure 6. Mean (+/- SE) surface ( ◊ ) and bottom ( □ ) temperatures by creek. Only the creek factor was significant (Table 1), so is the only factor shown. Figure 7. Mean (+/- SE) surface ( ◊ ) and bottom ( □ ) dissolved oxygen by creek (A) and zone (B). Only the creek and zone factor s were significant (i .e., there was no interaction effect, Table 1) , so are the only factors shown. Figure 8. Mean total abundance (A) and me an total species richness (B) by creek. Figure 9. Dendrogram of results of hierarchical cluster analysis (average linkage method, Euclidean distance) of species density and frequency of occurrence by creek and

zone. The first two letters in the abbr eviations are creek identifiers: CC = Culvert Creek, NS = North Silcox, SS = South Silcox, YP = Yucca Pen. The third letter

in the abbreviations is a zone identif ier: L = Lower, M = Middle, U = Upper.

### 27 Figure 10. Total abundance of freshwater specie s (all species combined) by creek, zone, and

month. Figure 11. Total abundance and frequency of occurrence for freshwater species. Figure 12. Mean density (+/- SE) of juvenile Centropomus undecimalis by creek, zone, and

month. Figure 13. Length frequencies of juvenile Centropomus undecimalis by creek. Data pooled across zones and sample periods. Figure 14. Mean lengths (+/- SE) of juvenile snook by creek and zone. Figure 15. Mean density (+/- SE) of juvenile Sciaenops ocellatus by creek, zone, and

month. Figure 16. Length frequencies of juvenile Sciaenops ocellatus by creek. Data pooled across zones and sample periods. Figure 17. Mean length (+/- SE) of juvenile Sciaenops ocellatus by creek and zone. Figure 18. Summary of short-term effects of hu rricane Charley. Mean total abundance (+/- SE) and mean total species richness (+/- SE) by creek and sample period prior to and after hurricane Charley. Sampling wa s interrupted by the hurricane, so the degraded creeks (Culvert Creek and Yu cca Pen) were not sampled. Immediate post-hurricane sampling was limited to No rth Silcox and South Silcox since there were immediate pre-hurricane data from these creeks.

### Figure 1. ‘Natural’ creeks

‘De g raded’ creeks Charlotte Harbor

### 29 Figure 2.

### 30 Figure 3.

### 31 Figure 4.

### 32 0 5 10 15 20 25

Lower Middle Upper 

### Creek ZoneMean Salinity (ppt) +/- SE Culvert Creek North Silcox South Silcox Yucca Pen



### Figure 5.

### 33 23 23.5

24 24.5

25 25.5

26 26.5

27 27.5

Culvert Creek North Silcox South Silcox Yucca Pen 

### CreekMean Temperature (oC) +/- SE



### Figure 6.

### 34 0 0.5

1 1.5

2 2.5

3 3.5

4 4.5

Culvert Creek North Silcox South Silcox Yucca Pen 

### CreekMean Dissolved Oxygen (mg/L) +/- SE 

### A

0 0.5

1 1.5

2 2.5

3 3.5

4

Lower Middle Upper 

### Creek ZoneMean Dissolved Oxygen (mg/L) +/- SE 

### B



### Figure 7.

### 35 0 2 4 6 8 10 12 14 16

February April June August October December February April June August Year/MonthMean No. Fish/m2 Culvert Creek Yucca Pen N Silcox Creek S Silcox Creek

2003 2004 A

0 5 10 15 20 25

February April June August October December February April June August Year/MonthMean No. Species/100m2+/- SE Culvert Creek Yucca Pen N Silcox Creek S Silcox Creek

2003 2004 B



### Figure 8.

### 36 Figure 9.

### 37 Figure 10.

0 5 10 15 20 25 30

February April J une A ug

ust Oc to

ber Decem be

r February April J une August O c tob er



### Year/MonthTotal Abundance

### 38 Figure 11.

Freshwater Species

0 10 20 30 40 50 60 70

s unfi s h s p

l m

bass

m inno w

s

p b a ss sp gar s p d ac

e s

p

fl ori

da ga r

l on

gnos e g

ar

yel

l owbullh e



### Common NameTotal Abundance/Occurrence Total Abundance Frequency of Occurrence

### 39 Figure 12.

### 40 Figure 13.

### 41 Figure 14.

0 20 40 60 80 100 120 140

Lower Middle Upper 

### Creek ZoneMean Standard Length (mm) +/- SE Culvert Creek North Silcox South Silcox

### 42 Figure 15.

### 43 Figure 16.

### 44 Figure 17.

0 10 20 30 40 50 60 70 80

Lower Middle Upper 

### Creek ZoneMean Standard Length (mm) +/- SE Culvert Creek North Silcox South Silcox

### 45 0 2 4 6 8 10 12 14 16 18

February Apr i l Jun e Au

gu

s t O

c t o be

r De

c ember Fe

b

ru

a ry Apri l June Au

gu

s t 1 3 1 4 1 7 1 8 1 9 O

c tober



### Year/MonthMean No. Fish/m2 +/- SE Culvert Creek North Silcox South Silcox Yucca Pen

Days post-hurricane 2003 2004 A

0 5 10 15 20 25

February Apr i l Jun e Au

g ust

O

c t o be

r Dece mb er Feb r ua

r y A p r i l J un

e Au

g ust 1 3 1 4 17 18 1 9 O

c t o be

r



### Year/MonthMean No. Species/100m2+/- SE Culvert Creek North Silcox South Silcox Yucca Pen

2003 2004 Days post-hurricane B



### Figure 18.Table 1. Summary of two-way ANOVA results of effects of Creek (N = 4) and Zone (N = 3) on Salinity, Temperature, and Dissolved Oxygen. A) Salinity

Source SS df MSE F p Creek 3418.255 3 1139.418 13.427 < 0.001 Zone 3142.511 2 1571.256 18.515 < 0.001 Creek X Zone 1070.724 6 178.454 2.103 > 0.05 Error 45401.69 535 84.863

B) Temperature

Source SS df MSE F p Creek 210.917 3 70.306 5.047 < 0.05 Zone 27.065 2 13.533 0.971 > 0.1 Creek X Zone 16.597 6 2.766 0.199 > 0.1 Error 7369.171 529 13.93

C) Dissolved Oxygen

Source SS df MSE F p Creek 130.045 3 43.348 12.958 < 0.001 Zone 35.486 2 17.743 5.304 < 0.01 Creek X Zone 18.953 6 3.159 0.944 > 0.1 Error 1772.959 530 3.345Table 2. Summary of abundance and occurrence of species captured in Charlotte Harbor study creeks. See Figure 1 for creek locations. Species listed by rank order of total abundance.Abundance = total abundance summed across all samples. Frequency = total number of samples in which the species was recorded (N = 574).Natural CreeksDegraded CreeksNorth SilcoxSouth SilcoxCulvert CreekYucca PenTotalAbundanceTotalFrequencyCreek UseClassification*SpeciesAbundanceFrequencyAbundanceFrequencyAbundanceFrequencyAbundanceFrequencyLucania parva283971423788913833724638817273539398RMenidia peninsulae277341421351313623027978399951388456RGambusia holbrooki162709937066720444724394724459260RPoecillia latipinna807193553484589243372614531227REucinostomusspp.13634935078022615232935410424235RMenidiaspp.28958225159127329608436291245REucinostomus harengula13276513179030042592363536233RLagodon rhomboides2141519597622316177273500170JMicrogobius gulosus115590141111018337233572982294RCentropomus undecimalis497559708086471259232590229JAnchoaspp.2221631680000253714TMicropogonias undulatus6811093626653068134629JCyprinodon variegatus5887848661531599151226169RSciaenops ocellatus361395213496211197995JCallinectes sapidus207723611351175613776822339RDiapterus plumieri3165329151122286515794147RLeiostomus xanthurus224214363233671876467JFundulus confluentus49438942180855772374RFarfantepenaeus duorarum2133125553441385520102JFundulus grandis1853315935691714742792RAdinia xenica1108279123250042125RSciaenidae spp juvenile395172102713324119JEucinostomus gula6657311431011519331RFundulus heteroclitus10913531122119619341RLucania goodei361211111281616630RCichlasoma urophthalmus4329141121414415935NSyngnathus louisianae371711547443315971RFundulus majalis1222331330012827RStrongylura notata171573344225811959TSyngnathusspp.28206937636510965RGobiosoma robustum2310291315111378041RLepomisspp.19102512178526632FMugilspp. juvenile256168105655724JAchirus lineatus136651391955125JJordanella floridae281200002255017FMenidia beryllina007321281375ROreochromis mossambicus15918500003314NFundulusspp.2773300113111RArchosargus probatocephalus95161322002720JOligoplites saurus3185001652711TOpsanus beta11814600002514JTrinectes maculatus00221022002412JMicropterusspp.0000851372112FStrongylura marina8500221032010TGobiosomaspp.131630000194RMugil cephalus3212944001915RSphoeroides nephelus430085641812JSyngnathus scovelli00151111001612TLepisosteus oculatus752232331512FCyprinidae spp.00008261143FCynoscion nebulosus53740000127JHemichromis bimaculatus53322100106NFundulus similis3143210095RElops saurus3143000074TSerranidae spp juvenile0000610061JGobionellus smaragdus0000420042RLutjanus griseus1122110044JMegalops atlanticus3300000033JStrongylura timucu0033000033TBothidae spp juvenile0011001122JLepisosteusspp.1100110022FTylosurus crocodilus0000210021TAmeiurus natalis0000001111FCichlidae spp juvenile1100000011NDormitator maculatus0000110011FLepisosteus osseus0000001111FLepisosteus platyrhincus0011000011FMugil curema0000001111TMyrophis punctatus1100000011TPortunusspp0000001111TRhinichthysspp.0000001111FSphyraena barracuda0000110011JSynodus foetens1100000011TTriglidae spp.1100000011TGobiosoma bosci0000000000RTotal Abundance96141754241366020767205992* R = Resident, T = Transient, J = Juvenile, F = Freshwater, N = Non-native. Designations based on this study, Robins et al. (1986), and Page and Burr (1991).Table 3. Summary of occurrence of the most common freshwater and non-native fish species.

Months of Occurrence b Salinity (ppt) c Species Classification a F A J Au O D Min Max Mean Ameirus natalis F √ 0.1 0.1 - Cyprinidae F √ √ 0 7.8 2.6 Dormitator maculatus F √ 7.5 7.5 - Jordanella floridae F √ √ √ √ 0.1 9.5 2.1 Lepisosteus osseus F √ 32.2 32.2 0 Lepisosteus platyrhincus F √ 12.1 12.1 - Lepisosteus spp F √ 4.2 25.9 15.1 Lepistosteus oculatus F √ √ √ 0.8 22.1 6.2 Lepomis spp. F √ √ √ 0.1 13.4 3.51 Micropterus spp. F √ √ √ √ √ √ 0.1 15.9 5.93 Rhinichthys spp. F √ 0.1 0.1 - Cichlasoma urophthalmus N √ √ √ √ √ √ 1.1 26.6 13 Hemichromis bimaculatus N √ √ 1.1 21.4 5.33 Oreochromis mossambicus N √ √ √ √ 0.6 20.4 4.13

a F = Freshwater, N = Non-native, based upon Page and Burr (1991). b F = February, A = April, J = June, Au = August, O = October, D = December. Data pooled across years (2003 and 2004) and creeks.

c Data pooled across years (2003 and 2004) and creeks.Table 4. Summary of abundance, occurrence, and densities of non-native cichlids in estuarine mangrove study creeks in Charlotte Harbor, Florida. Total Abundance is summed across all samples; Frequency of Ocurrence is the total number of samples in which the species was captured; Density is mean number fish/100m 2 (SE).

Natural Creeks Degraded Creeks Species North Silco x South Silco x Y ucca Pen Culvert Cree k Cichlasoma urophthalmus Total Abundance 4 29 14 112 Frequency of Occurrence 3 14 4 14 Density 0.023 (0.014) 0.149 (0.048) 0.085 (0.055) 0.958 (0.393)

Hemichromis bimaculatus Total Abundance 5 3 0 0 Frequency of Occurrence 3 2 0 0 Density 0.022 (0.014) 0.013 (0.01) 0 0

Oreochromis mossambicus Total Abundance 13 17 0 0 Frequency of Occurrence 7 4 0 0 Density 0.074 (0.032) 0.093 (0.069) 0 0 Tilapia spp Total Abundance 2 1 0 0 Frequency of Occurrence 2 1 0 0 Density 0.011 (0.007) 0.006 (0.006) 0 0Table 5. Summary of Kruskal-Wallis tests of Centropomus undecimalis densities by creek and zone. A) Comparison of densities by creek. Densities were different by creek: H = 44.46, p < 0.001, df = 3.

Mean Density Creek Rank Sum SE South Silcox 48379 0.0478 0.0178 Culvert Creek 43749 0.0643 0.0188 North Silcox 42949.5 0.0265 0.0074 Yucca Pen 29373.5 0.0147 0.006

B) Comparison of densities by zone within creeks. Values are mean (standard error).

Zone Creek Lower Middle Upper H* p

South Silcox 0.022 (0.008) 0.034 (0.013) 0.091 (0.054) 5.136 >0.05

Culvert Creek 0.076 (0.027) 0.027 (0.009) 0.09 (0.049) 0.583 >0.1

North Silcox 0.017 (0.0043) 0.0137 (0.004) 0.049 (0.022) 3.652 >0.01

Yucca Pen 0.041 (0.017) 0.003 (0.001) 0 26.489 <0.001



### Snook Density by Creek and Zone

0 0.2 0.4 0.6 0.8 1 1.2

ZoneMean No. Fish/m2Table 6. Summary of two-way ANOVA on effects of Creek (N = 4) and Zone (N = 3) on log-transformed standard length of snook, Centropomus undecimalis . Yucca Pen was not included because snook were absent from upper and rare in middle zones.

Source SS df MSE F p Creek 7.053 2 3.527 59.01 < 0.001 Zone 16.069 2 8.034 134.433 < 0.001 Creek X Zone 6.269 4 1.567 26.225 < 0.001 Error 126.163 2111 0.06Table 7. Summary of Kruskal-Wallis tests of Sciaenops ocellatus densities by creek and zone. A) Comparison of densities by creek. Densities were different by creek: H = 8.41, p < 0.05, df = 3.

Mean Density Creek Rank Sum SE North Silcox 47597 0.0156 0.004 South Silcox 44996 0.0246 0.0078 Culvert Creek 36598 0.0059 0.0022 Yucca Pen 35260 0.0113 0.0074

B) Comparison of densities by zone within creeks. Values are mean (standard error).

Zone Creek Lower Middle Upper H* p

North Silcox 0.026 (0.01) 0.016 (0.006) 0.004 (0.002) 4.838 >0.1

South Silcox 0.05 (0.021) 0.016 (0.007) 0.006 (0.003) 2.738 >0.1

Culvert Creek 0.012 (0.006) 0.004 (0.002) 0.002 (0.001) 2.354 >0.1

Yucca Pen 0.027 (0.022) 0.006 (0.004) 0 15.885 <0.001

Table 8. Summary of two-way ANOVA on effects of Creek (N = 4) and Zone (N = 3) on log-transformed standard length of red drum,

Source SS df MSE F p Creek 0.09 2 0.045 1.29 > 0.1 Zone 2.363 2 1.181 33.941 < 0.001 Creek X Zone 1.404 4 0.351 10.085 < 0.001 Error 28.749 826 0.035

### The Charlotte Harbor National Estuary Program is a partnership of citizens, elected officials, resource managers and commercial and recreational resour ce users working to improve the water quality and ecological integrity of the greater Charlotte Harbor watershed. A cooperative decision-making proce ss is used within the program to address diverse resource management concerns in the 4,400 square mile study area. Many of these partners also financially support the Program, which, in turn, affords the Program opportunities to fund projects such as this. The ent ities that have fi nancially supported the program include the following: U.S. Environmental Protection Agency Southwest Florida Water Management District South Florida Water Management District Florida Department of Environmental Protection Florida Coastal Zone Management Program Peace River/Manasota Regional Water Supply Authority Polk, Sarasota, Manatee, Lee, Ch arlotte, DeSoto and Hardee Counties Cities of Sanibel, Cape Coral, Fort Myers, Punta Gorda, North Port, Venice and Fort Myers Beach and the Southwest Florida Regional Planning Council.