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2009 SOUTHEASTERN NATURALIST 8(3):495–502
Abundance and Distribution of Larval and Juvenile
Fundulus heteroclitus in Northeast Florida Marshes
Stacy N. Galleher1,*, Iara Gonzalez1, Matthew R. Gilg1,
and Kelly J. Smith1
Abstract - Larvae and juveniles of Fundulus heteroclitus (Mummichog), commonly
occur in small, water-filled depressions on the intertidal marsh surface during low
tide. Previous work has shown that larger juveniles are typically found at lower
elevations on the marsh surface, while small larvae are more abundant in the high
marsh. The present study compared the abundance and size distributions of larval and
juvenile Mummichog between relatively low- and high-elevation sites on the marsh
surface at three locations in Northeastern Florida. Fundulus heteroclitus were both
more abundant and larger in size at low-elevation sites than at high-elevation sites
following the size-selective marsh-use pattern shown in other locations.
Fundulus heteroclitus (L.) (Mummichog), is an example of a resident
salt marsh fish that spends all stages of its life history exposed to the widely
fl uctuating abiotic conditions of the tidal marsh (Kneib 1986, Lipcius and
Subrahmanyam 1986, Weisberg 1986). Fundulus spp. play an important role
in salt marsh energetics, as both a predator and a source of food for other
fish and commercially important invertebrates (Allen et al. 1994, Kneib
1986). Although Fundulus spp. are nearly ubiquitous in salt marshes along
the US East coast, the marsh habitat is not a homogenous environment and
patchy distributions of young Fundulus spp. and other nekton are commonly
reported (Kneib 1984, 1987; Kneib and Wagner 1994; Rozas 1995).
Extreme environmental conditions on the marsh surface prevent most
teleosts, except for a few well-adapted genera such as Fundulus, from utilizing
this habitat for reproduction. Adult killifish predominantly reside in tidal
creeks and access the marsh surface during high tide to feed and reproduce
(DiMichelle and Taylor 1980; Kneib 1984, 1997a). Larvae inhabit natural
depressions on the marsh between culms of the emergent Spartina alternifl
ora Loisel. (Smooth Cordgrass) (Kneib 1984). These shallow depressions
are highly variable and susceptible to extreme abiotic conditions because
they are only fl ushed during a subset of high tides.
Northeast Florida, specifically the area south of St. Augustine, FL close
to Indian River Lagoon, is the southern-most extent of the Mummichog’s
range (Gonzalez et al. 2009). Previous studies on Sapelo Island, GA have
shown differences in marsh use by larval and juvenile Mummichog related
to intertidal elevation, with smaller fish inhabiting high-marsh areas and
1Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL
32224. *Corresponding author - email@example.com.
496 Southeastern Naturalist Vol. 8, No. 3
larger fish residing closer to the marsh edge (Kneib, 1984, 1986, 1993,
1997a). A similar pattern of larval and young juvenile fish abundance on the
high-marsh surface has also been shown in other locations such as New Jersey
(Able and Hagan 2000, 2003; Talbot and Able 1984), Delaware (Taylor
et al. 1977), and Connecticut (Fell et al. 2003). Some of these studies have
found that abundance of Mummichog larvae may be an indicator of marsh
health in areas with the introduced plant species such as Phragmites australis
(Cav.) Trin. ex Steud. (Common Reed) (Able and Hagan 2000, 2003; Able
et al. 2003). Kneib (1997b) hypothesized that the patterns of marsh use by
larval and juvenile Mummichog may be a key factor in tidal marsh trophic
dynamics, and reductions of viable larval habitat could have significant
implications on energy transfer throughout the marsh ecosystem. Therefore,
in the face of many changing abiotic and biotic factors on Florida marshes
including climate and land-use changes, and the introduction of non-native
species, we conducted a study to determine a current baseline for abundance
and distribution of Mummichog larvae and juveniles at different intertidal
elevations in salt marshes of northeastern Florida.
Distribution and abundance of larval and juvenile Mummichog were
determined by collecting fish from pit traps at three intertidal marsh locations
in northeastern Florida, including Nassau River (30.5209850°N,
81.4986218°W), Crescent Beach (29.9507020°N, 81.3109463°W), and Pellicer
Creek (29.6797363°N, 81.2245700°W) (Fig. 1). The Nassau collection
site was chosen based on abundance of adult Mummichog recorded by the
Fish and Wildlife Research Institute (FWRI) Jacksonville field lab from 2001–
2004. All other sites were chosen because they had habitat characteristics
similar to the Nassau site. Collection sites were situated adjacent to small intertidal
creeks that fed into larger subtidal channels. Intertidal vegetation was
predominantly Smooth Cordgrass with Juncus roemerianus Scheele (Black
Needlerush) located nearby but not within sampling sites. At each location,
traps (10-cm diameter x 5-cm height pyrex containers) were placed in two
grids consisting of 9 traps each in a 3 x 3 formation. Each trap was buried to its
top edge in the marsh substratum, and held fl ush to the surface by three metal
stakes. One grid was placed at each of two elevations (low and high) within
each location. Simple devices consisting of plastic mesh markers with fl oats
were held in place by wooden dowels set at each corner of the sampling grids
to measure maximum tidal inundation prior to each sampling event. Low- and
high-elevation sites were characterized by a mean spring tidal inundation of
45.7 (±12.97) cm and 28.7 (±13.22) cm, respectively (Table 1). Grids were
located within 30 m of each other near the spring high-tide mark and were
completely inundated during spring high tides. All traps were sampled at least
once after each semi-monthly set of spring tides from March–July in 2005 at
the Nassau and Crescent sites and March–July 2006 at all three sites. Fish were
identified, enumerated, and measured to the nearest mm standard length (i.e.,
2009 S.N. Galleher, I. Gonzalez, M.R. Gilg, and K.J. Smith 497
tip of snout to end of vertebral column at the caudal peduncle). Mummichog
was the dominant fish species at all sites (Gonzalez et al. 2009). Other species
caught by pit traps (e.g., Poecilia latipinna (Lesueur) [Sailfin Molly] and
Figure 1. Larval and juvenile pit-trap sampling locations in Northeast Florida.
Table 1. Average maximum tidal inundation and standard deviations for all sites (cm) from
Sites Mean S.d.
Nassau 44.70 14.15
Crescent 47.81 14.05
Pellicer Creek 44.46 10.72
Nassau 29.54 12.58
Crescent 35.55 16.43
Pellicer Creek 21.12 10.64
498 Southeastern Naturalist Vol. 8, No. 3
F. confl uentus Goode and Bean in Goode [Marsh Killifish]) were not included
in this study.
Mean abundance of fish collected per sampling event was compared between
high-and low-elevation sites using paired t-tests. Length frequencies
were not normally distributed and so were compared between elevations
within locations using non-parametric Mann-Whitney rank sum tests. A
reciprocal transformation was applied prior to analysis in order to equalize
variances. Size distributions among locations were normally distributed,
and so mean standard lengths were compared using ANOVA and post hoc
Tukey’s HSD applied separately to high- and low-elevation sites.
Mean number of fish collected per sampling interval was significantly
greater at low- than high-elevation sites at all locations (Nassau:
t5df = 2.58, P = 0.0491; Crescent: t4df = 3.12, P = 0.0354; Pellicer: t5df =
3.38, P = 0.0196). When samples were pooled over the season, mean
abundance was approximately two times greater at low-elevation sites
than high-elevation sites (Table 2). Fish from low-elevation sites were
significantly larger than fish collected from high-elevation sites at all locations
and in both years (Table 2).
Inequality of variances between years precluded the use of all data in
comparisons of length distributions across locations. Consequently, comparisons
were made only for 2006, when data were available from all three
locations (Nassau River, Crescent Beach, and Pellicer Creek). Mean length
at high-elevation sites did not differ significantly among locations (Table 3,
Fig. 2), but mean length (reciprocally transformed) at low-elevation sites
was greater at Nassau than at the other two locations (Table 4, Fig. 2).
Table 2. A series of separate Mann-Whitney Rank Sum tests performed on standard length (SL)
distributions for all locations for both sampling years. Reciprocal transformation of all data was
performed to homogenize variances. * = significant comparisons marked in bold.
Location/year n Mean SL (mm) Mean rank Sum of ranks Mann-Whitney U P
High 152 7.7090 253.48 38,529.00
Low 249 9.3092 168.96 42,072.00 10,947.000 <0.001*
High 61 9.1285 151.25 9226.50
Low 156 13.0641 92.48 14,426.50 2180.500 <0.001*
High 150 7.5024 276.29 41,444.00
Low 326 8.4407 221.11 72,082.00 18,781.000 <0.001*
High 50 8.2316 99.79 4989.50
Low 109 10.9900 70.92 7730.50 1735.500 <0.001*
High 5 6.5240 10.30 51.50
Low 66 10.2326 37.95 2504.50 36.500 0.004*
2009 S.N. Galleher, I. Gonzalez, M.R. Gilg, and K.J. Smith 499
In all study locations, Mummichog displayed a pattern of size selectivity
in marsh use, with larvae/juveniles less abundant in the high marsh, and
smaller size classes found in higher elevation areas farther from the marsh
Table 3. Comparison of mean standard length of Mummichog from high-elevation sites among
locations from 2006.
Source Sum of squares df Mean square F P
Corrected model 45.272(a) 2 22.636 2.253 0.110
Intercept 2413.144 1 2413.144 240.198 <0.001
Location 45.272 2 22.636 2.253 0.110
Error 1135.253 113 10.046
Total 9819.155 116
Corrected total 1180.525 115
Figure 2. Mean larval length ± 1 s.d. from 2006. Significant differences among locations
are indicated by different letters above the bars.
Table 4. Comparison of reciprocally transformed mean standard length of Mummichog from
low-elevation sites among locations from 2006.
Source Sum of squares df Mean square F P
Corrected model 0.035(a) 2 0.017 14.487 <0.001
Intercept 2.950 1 2.950 2461.606 <0.001
Location 0.035 2 0.017 14.487 <0.001
Error 0.393 328 0.001
Total 3.564 331
Corrected total 0.428 330
500 Southeastern Naturalist Vol. 8, No. 3
edge. These data show that Northeast Florida marshes display a pattern of
marsh-surface use by young Mummichog similar to that reported in Georgia
(Kneib 1984, 1986) and New Jersey (Talbot and Able 1984). Small fish may
use high-marsh areas to avoid nektonic predators, including larger conspecifics that are too large to inhabit the shallow marsh-surface depressions
(Kneib 1997a). It has been hypothesized that larger juveniles tend to reside
closer to the marsh edge because: (1) there are typically more and deeper
puddles of residual tidal water on the exposed marsh surface at lower elevations
closer to creeks or rivulets (Able and Hagan 2003; Kneib 1984, 1997a),
and (2) food resources may be re-distributed and replenished by more frequent
tidal inundation (Kneib 1997b).
Size-selective marsh use has been observed in previous studies; however,
it is difficult to make direct comparisons across studies due to differences in
methodology and the definitions of Mummichog larvae among researchers.
Kneib (1984) defined larvae as fish less than 10 mm SL, the size at which
they developed a full adult complement of fin rays. Able et al (2003) defined larvae as 20 mm TL (≈16 mm SL), the size at which scale formation
was complete. The present study followed Able et al (2003) and defined the
maximum size of larvae as 16 mm SL. Kneib’s (1984) study has the most in
common with the present study, with greater fish abundance at low elevations
(less than 10 m from marsh creek) than at high elevations (135 m from
marsh creek). Talbot and Able (1984) found many larval fish at a high-elevation
creek site in New Jersey and, in a later study conducted at low-elevation
sites, Able and Hagan (2000, 2003) found a greater abundance of young fish
between 5 and10 m from the marsh creek, with larger individuals found on
the marsh edge. Although the size definition of larvae and juveniles may be
different among studies, the general intertidal trend in size distribution, with
smaller fish residing near the upland border of the marsh and larger, more
abundant fish closer to the creek, is recognized across multiple geographic
locales. Some differences between the present study and earlier work, including
the relative abundance of fish sampled and the ratio of larvae to
juveniles, may be a result of the sampling methods. In this study, collections
occurred during the spring tide, where the maximum abundance of larvae is
expected (Kneib 1997a), but these numbers do not account for high larval
mortality or recruitment into other size classes.
Several alternative hypotheses have been proposed to explain the intertidal
distribution pattern of young Mummichog in intertidal marshes.
These have included the occurrence and physical characteristics of aquatic
refugia, frequency and duration of tidal inundation, and the distribution of
prey, predator, or competitor fields (e.g., Able and Hagan 2003; Able et al.
2003, 2007; Kneib 1984, 1986, 1993, 1997a). It was beyond the scope of the
present investigation to distinguish among these alternative explanations for
the observed distribution of young Mummichogs in marshes of northeastern
Florida, but the similarity of pattern in the intertidal distribution of larvae
and juveniles from New Jersey to north Florida suggests that Mummichog
2009 S.N. Galleher, I. Gonzalez, M.R. Gilg, and K.J. Smith 501
may be an excellent model organism for future research aimed at exploring
the ecological consequences of abiotic and biotic variability along intertidal
gradients within salt marsh ecosystems.
The size-selective pattern of marsh use by Mummichog observed throughout
its range could be important in comparing functional aspects of different
salt marshes. Able and Hagan (2000, 2003) reported a reduction in Mummichog
larvae in marshes dominated by the invasive Common Reed when
compared to adjacent Cordgrass-dominated marshes, suggesting that larval
abundance may be an indicator of marsh nursery-habitat function. The high
marsh can be susceptible to a variety of disturbances, such as non-native plant
introductions or activities on uplands adjacent to marshes (e.g., dredging and
residential or industrial development) and could similarly affect the presence
or availability of intertidal aquatic microhabitats on the marsh. High marshes
immediately adjacent to disturbed uplands may be the most vulnerable to
these types of disturbances that could remove essential nursery habitat for the
smallest larvae, forcing them to occupy lower marsh elevations where they are
less protected from predation.
Northeast Florida marks the southern extent of the Mummichog’s range,
so it may be interesting to determine if marsh-use patterns differ in the
zone of overlap with Fundulus grandis Baird and Girard (Gulf Killifish), a
closely related species that occurs just south of Pellicer Creek (Gonzales et
al. 2009). Gulf Killifish are generally larger as adults than Mummichog, and
if they display similar marsh-use patterns, Gulf Killifish could preferentially
inhabit low-marsh areas in greater numbers, possibly affecting the area
available to each species. Predation by, or competition with, the larger Gulf
Killifish in lower marsh habitat may be a factor that could affect Mummichog
population densities. Future studies could be performed to determine if Gulf
Killifish larvae/juveniles show similar patterns of size-selective marsh use
and whether there are significant interactions between the two species in
marshes where their distributions overlap.
The authors thank G. Ehrlinger for critical reading of the manuscript, D.C. Moon for
statistical analysis, R. Gleeson and K. Petrinec for GTM NERR data, and Russ Brodie
for FIM data. Special thanks to Dr. R. Kneib for editing this manuscript along with two
anonymous reviewers. Support for the project was through funding from the University
of North Florida Biology department and the Coastal Biology Flagship program.
Able K.W., and S.M. Hagan 2000. Effects of Common Reed (Phragmites austrialis)
invasion on marsh surface macrofauna: Response of fishes and decapod crustaceans.
Able, K.W., and S.M. Hagan. 2003. The impact of Common Reed, Phragmites
australis, on essential fish habitat: Infl uence on reproduction, embryological
development, and larval abundance of Mummichog (Fundulus heteroclitus).
502 Southeastern Naturalist Vol. 8, No. 3
Able, K.W., S.M. Hagan, and S. Brown. 2003. Mechanisms of marsh habitat alteration
due to Phragmites: Response of young-of-the-year Mummichog (Fundulus
heteroclitus) to treatment for Phragmites removal. Estuaries 26(2B):484–494.
Able, K.W., S.M. Hagan, K. Kovitvongsa, S.A. Brown, and J.C. Lamonaca. 2007.
Piscivory by the Mummichog (Fundulus heteroclitus): Evidence from the laboratory
and salt marshes. Journal of Experimental Marine Biology and Ecology
Allen, E.A., P.E. Fell, M.A. Peck, J.A. Gieg, C.R. Guthke, and M.D. Newkirk. 1994.
Gut contents of common Mummichogs, Fundulus heteroclitus, in a restored impounded
marsh and in natural reference marshes. Estuaries 17:462–471.
DiMichele, L., and M.H. Taylor. 1980. The environmental control of hatching in
Fundulus heteroclitus. Journal of Experimental Zoology 214:181–187.
Gonzalez, I., M. Levin, S. Jermanus, B. Watson, and M.R. Gilg. 2009. Genetic assessment
of species ranges in Fundulus heteroclitus and F. grandis. Southeastern
Fell, P.E., R.S. Warren, J.K. Light, R.L. Rawson, Jr., and S.M. Fairley. 2003. Comparison
of fish and macroinvertebrate use of Typha angustifolia, Phragmites
austrlis, and treated Phragmites marshes along the lower Connecticut River.
Kneib, R.T. 1984. Patterns in the utilization of the intertidal salt marsh by larvae
and juveniles of Fundulus heteroclitus (Linnaeus) and Fundulus luciae (Baird).
Journal of Experimental Marine Biology and Ecology 83:41–51.
Kneib, R.T. 1986. The role of Fundulus heteroclitus in salt marsh trophic dynamics.
American Zoologist 26:259–269.
Kneib, R.T. 1987. Seasonal abundance, distribution, and growth of postlarval and
juvenile Grass Shrimp (Palaemonetes pugio) in a Georgia, USA, salt marsh.
Marine Biology 96:215–223.
Kneib, R.T. 1993. Growth and mortality in successive cohorts of fish larvae within
an estuarine nursery. Marine Ecology Progress Series 94:115–127.
Kneib, R.T. 1997a. Early life stages of resident nekton in intertidal marshes. Estuaries
Kneib, R.T. 1997b. The role of tidal marshes in the ecology of estuarine nekton.
Oceanography and Marine Biology: An Annual Review 35:163–220.
Kneib, R.T., and S.L.Wagner 1994. Nekton use of vegetated marsh habitats at different
stages of tidal inundation. Marine Ecology Progress Series 106:227–238.
Lipcius, R.N., and C.B. Subrahmanyam. 1986. Temporal factors infl uencing killifish
abundance and recruitment in Gulf of Mexico salt marshes. Estuarine, Coastal,
and Shelf Science 22:101–114.
Rozas, L.P. 1995. Hydroperiod and its infl uence on nekton use of the salt marsh: A
pulsing ecosystem. Estuaries 18(4):579–590.
Talbot, C.W., and K.W. Able. 1984. Composition and distribution of larval fishes in
New Jersey high marshes. Estuaries 7:434–443.
Taylor, M.H., L. DiMichele, and G.J. Leach. 1977. Egg stranding in the life cycle
of the Mummichog, Fundulus heteroclitus (Pisces: Cyprinodontidae). Copeia
Weisberg, S.B. 1986. Competition and coexistence among four estuarine species of
Fundulus. American Zoologist 26:249–257.