Florida Institute of Technology. Department of Oceanography and Ocean Engineering. Melbourne, Florida 32901. MARK S. PETERSON. University of Southern ...
Estuaries
Vol. 6, No. 3, p. 3114322
September 1965
Ecotopic and Ontogenetic Trophic Variation in Mojarras (Pisces: Gerreidae)’ BARBARA A. KERSCHNER
Florida Institute of Technology Department of Oceanography and Ocean Engineering Melbourne, Florida 32901 MARK
S. PETERSON
University of Southern Mississippi Department of Biological Sciences Hattiesburg, Mississippi 39406-5018 R. GRANT GILMORE, JR.
Harbor Branch Foundation, R.R.1 Box 196 Ft. Pierce, Florida 33450
Inc.
Seven species of mojarras (Gerreidae) were collected from three stations in the ABSTRACT: Indian giver lagoon near the Sebastian Inlet, Florida over an eighteen month period to study spatial and temporal variations in occurrence and feeding habits. Two major habitats common to this area were represented in the study; a sandy beach and a seagrass flat. Of the 2,899 gerreids collected, Eucinostomus gula represented 67% and was found primarily in the Halodule seagrass site. The next most abundant species, E. argenteus (ll%), E. jonesi and E. lefroyi (each lo%), were found most frequently at the inlet site. Diapterus auratus, E. melanopterus, and Gerres cinereus were captured infrequently and were considered incidental. Prey items found included amphipods, bivalves, copepods, fish eggs, foraminifera, isopods, nematodes, ostracods, polychaetes and crustacean parts. Significant amounts of sand and unidentifiable amorphous debris were also included in the gut content analysis. Little interspecific variation in diet was found among the four major species examined. The general shift seen from a diet composed primarily of copepods and other crustaceans to one of polychaetes suggests an intraspecific ontogenetic progression. Spatial variations in diet composition were also indicated between the two major habitats. Feeding analyses showed gerreids to be diurnal feeders with the greatest consumption (total gut content weight) occurring at dusk.
Introduction
sand beaches, shallow reef formations and open neritic waters (Randall 1967; Gilmore 1977). Mojarras are mainly benthic feeders with highly protrusible mouths and have been observed foraging for infaunal invertebrates (Randall 1967). Studies have shown them to feed primarily on copepods, amphipods, mysids, shrimps, pelecypods, ostracods, nematodes, polychaetes, and detritus (Reid 1954; Odum 1970; Carr and Adams 1973). Few comprehensive studies have been conducted exclusively on gerreids although they are abundant and occupy an important
Mojarras, family Gerreidae, are among the common fish species inhabiting the nearshore waters of Florida (Reid 1954; Springer and Woodburn 1960; Carr and Adams 1973; Gilmore 1977). While mainly found in estuarine habitats, gerreids have been reported from freshwater tributaries,
’Contribution No. 470 of the Harbor Branch Foundation, Inc. and contribution No. 63 of the Florida
Institute of Technology. 0 1985 Estuarine Research Federation
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312
!3.A. Kerschner et al.
Fig. 1. Studylocationin the IndianRiver lagoon.
trophic link in estuarine food webs (Odum 1970). Data available on mojarras in the southeastern United States and Caribbean include only those extracted from major fauna1 works. The most detailed studies to date concern: Gerres oyena and 6. jilamentosus (Rao 1968); D. rhombeus (Austin 197 1); G. acinaces, G. oblongus, G. oyena, G. Jilamentosus and G. rappi (Cyrus and Blaber 1983a, 1983b, 1984). The limited knowledge of gerreid feeding ecology in Florida led to the development of this study. Our goal was to examine feeding habits of the gerreid family in the Indian River lagoon, a polyhaline Florida estuary. Specific objectives included examination of diel, ontogenetic, and spatial variation in diet and habitat utilization. Methods STUDY AREA
The Indian River is a natural estuarine lagoon located along the Atlantic coast of central Florida. Three stations were selected at two sites near the Sebastian Inlet (Fig. 1). These sites were representative of two major
habitats common in this area; sandy bottom areas and seagrass flats. The first station bordered a beach on the northern side of the inlet proper. The bottom contour slopes gradually downward until reaching the main channel (4-5 m deep) about 10 m from shore. Strong inlet tidal currents influence the mixture of sand, carbonate beach rock and shell hash which characterize the substratum. Aquatic vegetation is limited to drift algae. The second site was located approximately 1.5 km south of Sebastian Inlet in a lagoon seagrass flat, within the range of tidal influence. The area has a 66% plant cover comprised primarily of manatee grass, Syringodium @j&me and shoal grass, Halodule wrightii{Thompson 1976). An offshore sandbar bisects this flat about 110 m from shore and separates the two lagoon stations. The inshore station, reaching depths of 1.5 m, is composed primarily of Halodule grass; the offshore station, sloping downward toward the main channel, is comprised mainly of Syringodium grass. Both seagrass stations also support a diverse flora of macroalgae. Red mangrove, Rhizophora mangle, and black mangrove, Avicennia germinans, dominate the shoreline vegetation. COLLECTIONPROCEDURES
Biweekly morning and evening collections of fish were taken from all three stations between 30 October 1980 and 30 October 198 1; monthly samples were collected from 12 November 198 1 through 9 April 1982. Species capture rate per month is listed in Table 1. Collections were made with a 3.05 x 1.22 m seine constructed of 4.7 mm “ace” netting. Seven consecutive net hauls (6-7 m in distance) were taken at each station. The inlet topography caused a spatial overlap of several pulls during each sampling period, no spatial overlap occurred in the seagrass site within a given sampling. Upon capture, all gerreids were immediately placed in a narcotizing agent (5Oh ethanol solution) and then preserved in 20% buffered formalin. Fishes larger than 50 mm in standard length (SL) were also injected intraperitoneally. Specimens were fixed for one week, rinsed in water and transferred to 70% ethanol for storage.
Ecotopic and Ontogenetic Trophic Variation
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313
On 15-l 6 May 1982, specimens were collected and preserved every four hours through a 24 hour period in the Halodule station to examine short term die1 feeding patterns. Following identification and separation by size class the most complete group collected, 20-29 mm E. gula, was analyzed for comparison with morning and evening samples. FEEDING ECOLOGY
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Identified specimens were sorted by species into 10 mm SL size class sample groups based on station, sample period and date. Entire digestive tracts were analyzed for a random sample of up to 20 individuals from each group. Sorted prey items were identified to the lowest possible taxon, dried at 75 “C to constant weight, and weighed to +0.0001 g. Diet components were evaluated in terms of: % frequency of occurrence (FO), examining sample group specimens individually; % dry weight (DW), pooling all individuals from each sample group; and die1 feeding changes for each species. Limitations of these methods have been reviewed by Berg (1979) and Hyslop (1980). The relative % DW and FO compositions of all prey categories are listed in Tables 2 and 3. Fecal pellets and sand grains intact in the alimentary tract of a prey organism were classified with that organism; those found within the open digestive tract of the fish were classified separately. For the purpose of histogram presentation, polychaetes and polychaete parts were considered polychaete tissues; amphipods, isopods, and unidentified crustacean parts were considered crustaceans. No distinction was made between veligers and juveniles for bivalve types. Results Collections produced 2,899 gerreids dming the study period (Table 1). Of this total catch, Eucinostomus gula accounted for 67%, E. argenteus 1 l%, E. jonesi and E. lefrovi 10% each. The remaining species, Diapterus auratus, Gerres cinereus and E. melanopterus together comprised 2% of the total catch and were considered incidental. Because of their low abundance, these three species were not included in the feeding analysis.
314
6. A. Kerschner et al.
TABLE 2. Dry weight of prey items for morning and evening sampling periods. DW is reported as a percentage of the total DW of all prey items consumed at a given site by each species. IN = Inlet; IB = Hulodtde; OB = Syringodium. E. Food Categories
IN
IB
E. jonesi
E. ,&a
ai-genteus OB
IN
IB
OB
IN
12
7
8 10
5
9
10 5
20
7 5 3 28 12 7 6
8 4
IB
E.
iefroyi
OB
IN
32
8 16 3
Morning DW data Amorphous debris Bivalves Calanoid copepods Caprellid amphipods Gammarid amphipods Fecal pellets Harpacticoid copepods Isopods Miscellaneous Nematodes Ostracods Polychaete parts Polychaetes Sand grains Und. crust. parts
17 20
Amorphous debris Bivalves Calanoid copepods Gammarid amphipods Fecal pellets Fish eggs Harpacticoid copepods Miscellaneous Nematodes Oligochaetes Ostracods Polychaete parts Polychaetes Sand grains Und. crust. parts
9 21
11 16 10
21 21
16 20 7
1 :1 10 l!) !)
41
3
3 4
3 4
31 19
1 2 5 4 4 5 13
10 5 2 3
18 25
5 11 16 10
40
8 21 6 10
3 3 11
4 13 17 21 21
60
27
19
9 20
6 5 19 10
Evening DW data 17 13
22
17 17 3
8 13 8
1’3 11: 18
19
11 13
3
5
10
12 3 6
26
7 11 2 9 12
16
36
Consumed prey items included amphipods, bivalves, copepods, fish eggs, fecal pellets, foraminifera, isolpods, nematodes, oligochaetes, ostracods, polychaetes, unidentified crustacean parts, and amorphous debris (Table 2). Sand grains were found in many individuals regardless of size or capture location. In general, a lower % DW of copepods and other crustalceans and a higher % DW of polychaete tissues appeared with increasing fish size.
Eucinostomus argenteus GENERAL L)IET
Eucinostomus argenteus occurred in collections each month from October 1980 through February 198 1 exlcept February and March 1980 and January 1981. The 318
7
3 5 2
2 20 6 13 14
2 23 21 6 6
5
4 23 24 11 6
3 8
34
3 27
21
I 40
12 13
15 1
13 6 3 27 2 7 9 3
9 5
14 14
14 2 9 9
individuals captured ranged in size from 10 to 104 mm SL. Prey composition varied little between morning and evening samples within a given station. Bivalves, crustaceans and polychaetes were the major prey items in the morning inlet specimens. Bivalve and crustacean consumption remained fairly constant at 2025% DW for each size class. Polychaete tissues ranged from -8% to -30% DW. In the evening inlet sample, bivalves contributed -30% DW of the 30-69 mm individuals’ diets, complimented by -20% DW crustaceans. For the 60-99 mm group, polychaete tissues averaged -28% DW while bivalve consumption was reduced to - 12% DW (Fig. 2). In the morning collection at the Halodule
315
Ecotopic and Ontogenetic Trophic Variation
TABLE 3. Frequency of occurrence of prey items for morning and evening collection periods. Frequencies are reported as a percentage of the number of individuals in which the prey items occurred at a given site by each species. IN = Inlet; IB = Halodulq OB = Syringodium. E. IN
argentnrs IB
E. gada OB
IN
IB
E. OB
IN
51
52
25 25
34
33
8 40
5 11 19
45
15
16 36 25 69 29 35 54
9 25 23 42 26 79 61
Evening FO data 56 37 28 43 7 17
30
E. lefroyi
jonesr IB
OB
IN
Morning FO data Algae Amorphous debris Bivalves Calanoid copepods Caprellid amphipods Crepidula sp. Gammarid amphipods Fecal pellets Fish eggs Harpacticoid copepods Isopods Miscellaneous Nematodes Ostracods Polychaete parts Polychaetes Sand grains Und. crust. parts Amorphous debris Bivalves Calanoid copepods Caprellid amphipods Cladocera Gammarid amphipods Fecal pellets Fish eggs Harpacticoid copepods Hydroid polyps Invertebrate eggs Miscellaneous Nematodes Ostracods Polychaete parts Polychaetes Sand grains Und. crust. parts
70 63 6 20
20
20
41
30
64 28
7 6 7
43 64
16
7
36
23 30 3 6 6 26 33 53 63
16
31 10 10 10 10 10 10 75
36 21
60
20 10
7 14 28
20 80
35 42
17
16 8 8
45
66
:: 15 12 10 7 19 12 36 89
24
44 6 21
8 50 16 66 66
5 31 22 31 12
100
20 12
9 12 6
13
14 6
40
10 19 26 42 22 47 70
8 2.5 19 19 10 24 33
33 14
14
28
grassbed, bivalves, copepods, other crustaceans and polychaetes were the major prey items. The 10 mm size class consumed only copepods and various other crustaceans which formed -90% of the total DW composition. Bivalves, found only in the 30 mm group, comprised -27% DW. Polychaetes were present in both the 20 and 30 mm size classes. For the evening sample, bivalves, copepods, and other crustaceans composed -70% of the DW composition in the 1O19 mm fish. Polychaetes replaced bivalves in the 20-39 mm spec:imens, and formed 40-85% DW in the 50-69 mm fish (Fig. 2).
6
28
: 6 21
12 7 19 24 9 28 32
8 28 16 47 29 21 29
8 24 26 43 26 22 39
7 13 12 13
33
45
7 12
7
10
7
7
18
28 72
10 34 17 70
36 6 21 11 10 33 8 35 57
Few specimens were encountered in the Syringodium bed. Major prey items for the morning collections included copepods and other crustaceans. Crustaceans (- 6 5% DW) and ostracods (-35% DW) comprised the diet of the lo-19 mm size class. The 20-29 mm size class exhibited a greater variety in diet, including bivalves, calanoid and harpacticoid copepods and various other crustaceans. The 30-39 mm size class was represented by an individual which ingested primarily copepods and other crustaceans. Only two size classes, 1O-29 mm, were found at this station during the evening collec-
316
8. A. Kerschner et al.
Inlet p.m.
Inlet a.m.
Halodule a.m.
Holodufe
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65’
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Other
Fig. 2. Diet of E. argenteus from each of the stations. Histograms represent stomach contents based on the % DW of major food categories. Numbers above histograms represent size classes of fish in mm SL. Numbers below histograms represent the number of fish with food in the digestive tracts over the total number of fish examined.
Ecotopicand OntogeneticTrophicVariation
Inlet
0.m
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, 4%
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Crustaceans
Polychaetes
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Other
Diet of E. g&a from each of the stations. Histogram presentation f&lows that in Fig. 2.
318
B. A. Kerschner et al.
70
1
Eucinostommgula 20-29mm SL
flat in the morning collections. Crustaceans remained fairly constant at - 10% DW in each of the size classes, although they were absent in the 60-69 mm fish. Bivalves appeared only in the 50-59 mm group. Evening collection fish in the lo-59 mm size classes fed primarily on copepods (- 3-25% DW), various other crustaceans (- 3-30% DW), and polychaete tissues (- 8-60% DW). The 60 mm individual had a more diverse diet which included fecal pellets, invertebrate eggs and ostracods (Fig. 3). Morning collections from the Syringodium grass showed copepods, other crusTIME OF DA” taceans, and polychaetes to be the major Fig. 4. Die1 feedinghabits of E. gula based on the diet constituents. Copepods and crustatotal DW of stomach contents. Numbers above the ceans formed -90% DW of the diet of the histogramsrepresentthe number of fishcontainingfood 1O-l 9 mm fish. Polychaete tissues frequentin the digestive tract over the total number of fish ly dominated the prey composition in the examined. 20-59 mm fish, averaging -37% DW. Copepods and various other crustaceans actions. Food of these fish included copepods, counted for - 80% DW in the 10-l 9 mm crustaceans and ostracods (Fig. 2). fish in the evening collections. In the 30-80 mm size classes, crustaceans decreased to Eucinostomus gula - 10% DW, while polychaete tissues ranged GENERAL DIET from -28-70% DW (Fig. 3). Eucinostomus gula was collected in DIEL COMPARISON morning and evening samples each month except March 198 1. The 1,942 individuals The 24 hour feeding study was analyzed captured ranged in size from 10 to 109 mm by total DW using the 20-29 mm size class. SL. Prey composition varied little between Prey items appeared in the digestive tract morning and evening samples within a giv- in the early morning collection and were en station. present throughout the day ranging from 20Morning collections from the inlet pro40 x 10e4 g. A peak in the amount of conduced few individuals, these typically from sumed materials (55 x 10e4 g) occurred at the 50-109 mm size classes. Major dietary dusk. In late evening, the total weight of components included bivalves, crustaceans, prey items found in the gut decreased to ostracods, and amorphous debris. Analysis 15 x 10d4 g, while the first appearance of of the evening collections showed the major empty guts was recorded. No prey items components to include bivalves, crustaoccurred in the guts after midnight (Fig. 4). ceans and polychaetes. Nothing was found in the gut of the 1O-l 9 mm individual. Prey Eucinostomus jonesi of the 30-49 mm fish included -30% DW GENERAL DIET bivalves and -40% DW crustaceans. In the 50-89 mm size group, a decrease to - 12% Eucinostomus jonesi was collected at each DW of crustaceans was observed, with polyof the study sites during both morning and chaete tissues averaging -30% of the DW evening sampling periods from July 198 1 content. For the 90-109 mm fish, bivalves through January 1982. The 288 specimens (-8% DW), polychaetes (-25% DW) and captured ranged in size from 10 to 109 mm amorphous debris (-63% DW) were the SL. Similar prey items were found in the morning and evening samples for each staprimary dietary components (Fig. 3). tion. Copepods, other crustaceans and polyA high degree of variability in diet was chaete tissues were the major items conseen among the individuals comprising the sumed by fish from the Halodule seagrass
r-7
3/5
015
Ecotopic and Ontogenetic Trophic Variation
El jonesi Inlet
Inlet
0.m.
Hofodule a.m.
Syringodiim a.m.
cm
kfafodufe Dm
Syringodium
p.m.
100 90
2
80
r
60
20
70
5 ‘;
50
s
40
69
30
p
20
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IO 0
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Fig. 5.
Copepods
Crustaceans
Polyctxletes
Sand
Diet of E. jonesi from each of the stations. Histogram presentation
Other
follows that in Fig. 2.
319
320
B. A. Kerschner et at.
.E. leff oyi Inlet a.m.
Bivalves
Inlet pm.
Capepods
Crustaceans
Polychaetes
Sand
Hafodule a.m.
Other
Fig.6. Diet of E. Zefoyikom theinletandHalodule stations.Histogram presentation fallows that ia Fig.2.
small sample of the inlet mofrning collections. The primary constituents included bivalves, crustaceans, and polyclhaetes. In the evening, - 80% DW of the major prey items included bivalves, crustaceans and polychaetes. Copepods and various other crustaceans formed - 80% DW of the diet of the lo-19 mm fish. In the 20-59 mm fish, bivalves, crustaceans and polychaetes formed -70-l 00% DW of the prey, remaining relatively constant in each of the size classes. Polychaete tissues composed 98% DW of the diet of the 70-79 mm group. Guts of the 100 mm individuals were empty (Fig. 5). For the Hulodule station during both the morning and evening, copepods and other crustaceans were consumed by the fish examined. Ostracods and sand also appeared in the 10 mm class from the evening group (Fig. 5). The morning sample from the Syringodium station showed crustaceans to be a food source of both size classles. Copepods and amorphous debris were also found in the larger fish. In the evening, the diet of
the lo-29 mm fish consisted mainly of copepods (-40% DW), other crustaceans (-25% DW), and ostracods (- 5% DW). Bivalves, copepods, fecal pellets and oligochaete worms were consumed by the 30-39 mm individual (Fig. 5). Eucinostomus
lefroyi
GENERAL DIET
Eucinostomus lefroyi appeared in collections during November 1980, January 198 1, and May through December 198 1. The 290 specimens collected ranged from 10 to 69 mm SL. Prey items were similar in the morning and evening samples. Major prey items in the morning samples included bivalves, copepods, other crustaceans and polychaetes. The lo-29 mm fish ate -70% DW copepods and crustaceans. Bivalves (1 O-30% DW) and polychaete tissues (8-40% DW) were present in the 3050 mm classes. Major items found in the evening samples included primarily copepods, various other crustaceans and polychaete tissues. Crustaceans formed -2278% DW in the lo-29 mm fish, decreasing
Ecotopic and Ontogenetic Trophic Variation
to - 7-22% DW in the 30-59 mm fish. Polychaete tissues ranged from -6% DW in the lo-29 mm classes, to - 1537% DW in the 30-59 mm group and 100% DW in the 6069 mm individual (Fig. 6). INTERSPECIFIC COMPARISON
General Diet Little difference in diet was observed among E. argenteus, E. gula, 6. jonesi and E. lefroyi. Bivalves, copepods, other crustaceans, ostracods, polychaete tissues, sand and amorphous debris comprised the major categories of ingested materials, while other food items occurred less frequently (Table 3). Discussion
A highly diverse gerreid species composition was found in the Sebastian Inlet region. Five of the seven gerreid species observed were collected at the inlet site, while each was represented in collections at the seagrass site. A varied species assemblage commonly occurred within the same seine haul. Several reports have suggested a habitat related species separation between E. argenteus and E. gula (Springer and Woodburn 1960; Odum 1970), while another found little difference in the area of occurrence between these two species (Brook 1977). Abundance data from the two collection sites studied suggested an interspecific habitat preference. Eucinostomus lefroyi was found almost exclusively in the inlet. Eucinostomus argenteus and E. jonesi were also captured more frequently in the inlet. Eucinostomus gula was taken more frequently from the Halodule station. A general occurrence pattern exhibited by the species found in both habitats showed that the smaller fish were more abundant in the seagrass site while the larger fish were more abundant in the inlet. It is suggested that habitat specific environmental parameters contributed to the observed size separation. Seagrass beds have also been well documented as nursery grounds for a variety of marine species seeking adequate food resources and refuge from predation (Briggs and O’Connor 197 1; Zieman 1982).
321
In contrast to habitat selection, interspecific distinction in food types was not well defined. The diet of these mojarras was similar in composition to those reported in the feeding analyses by Carr and Adams (1973) and Brook (1977). Variations lie in the relative composition percentages reported in each investigation. Sand ingestion correlated with bivalves and polychaete tissues and appeared to be inadvertently consumed. Changes in feeding have been attributed to habitat structure and relative food availability, varying as a factor of both spatial and seasonal fluctuations in prey density (Stoner 1980). Slight changes in food composition between the two sites by the mojarras in this study appeared to be influenced by overall habitat structure. Distinction occurred primarily of inlet or seagrass sites rather than by species. Intraspecific variations in FO can be seen between the two major sites. Amphipod, bivalve, fish egg and isopod consumption was greatest in the inlet; copepod and nematode consumption was greatest in the grassbeds by each species (Table 3). Interspecific FO diet similarities also suggest a habitat influence on prey availability. Food preference may be an additional factor. Intraspecific variation in diet was reflected in an apparent ontogenetic feeding progression. The general pattern observed in each of the 4 species showed a transition from the consumption primarily of copepods and crustacean tissues in the smaller fish, to one which included a high percentage of polychaete tissues in the larger fish. Carr and Adams (1973) and Kinch (1979) found E. gula to exhibit the distinct transition from a planktivore, feeding on copepods, to a carnivore, feeding almost exclusively on polychaetes. Polychaete tissues represent a major dietary component throughout the range of individuals observed, increasing in importance with the growth of the fish. Due to mouth morphology, which limits the extent of substratum penetration, polychaete tissues found in the smaller specimens probably originated from prey captured in the water column (Dean 1979) or larval stages on the substratum surface.
322
B. A. Kerschner et al.
Die1 variation in feeding was evidenced in the feeding analyses. The mojarras studied exhibited an evening lcrepuscular feeding behavior. The high total gut content weight observed concurrently with a high frequency of empty guts in the evening specimens suggests either differential digestive rates of the prey items consumed or feeding on heavier items at dusk. Brook (1977) recognized E. gula and E. argenteus as diurnal feeders but did not determine specific feeding periods during the day. Mechanisms of resource partitioning, dependent upon variance through food type, habitat, and/or time allow the settlement of a great diversity of species (Schoener 1974; Livingston 1982). Although niche partitioning along the food resource dimension was not indicated by these data, slight interspecific differences of prey items were found. The inter- and intraspecific feeding behavior exhibited in this study was apparently an interrelationship of ontogenetic, spatial and temporal parameters. This is attributed to the utilization of available resources within the habitat structure. ACKNOWLEDGMENTS This research was supported by two research grantsin-aid from the Sebastian Inlet Tax District, Florida and the Florida Institute ofTechnology, and three graduate scholarships to Mark S. Peterson from the Slocum-Lunz Foundation of Charleston, South Carolina. We thank Michael Bodle, Elizabeth Cantrell, Robert Fricke and Brian Wendler for their aid in field collections. Thanks also to the many other people who assisted with field collections and in preparation of this manuscript. LITERATURE CITED AUSTIN,H. M. 197 1. Some aspects of the biology of the rhomboid mojarra Diapterus rhombeus in Puerto Rico. Bull. Mar. Sci. 21:886-903. BERG, J. 1979. Discussionofmethodsofinvestigating the food of fishes, with reference to a preliminary study of the prey of Gobiusculusflavescens (Gobiidae). Mar. Biol. 501263-273. BRIGGS,P. T., AND J. S. O’CONNOR. 1971. Comparison of shore-zone fishes over naturally vegetated and sand filled bottoms in Great South Bay. N.Y. Fish Game 18:15-41. BROOK,I. M. 1977. Trophic relationships in a seagrass community (Thalassia testudinum Konig) in Card Sound, Florida. Fish diets in relation to macrobenthic and cryptic fauna1 abundance. Trans. Am. Fish. Sot. 1061219-229. CARR, W. E. S., AND C. A. ADAMS. 1973. Food habits
of juvenile marine fishes occupying seagrass beds in the estuarine zone near Crystal River, Florida. Trans. Am. Fish. Sot. 102:5 1 l-539. CYRUS, D. P., ANDS. J. M. BLABER. 1983a. The food and feeding ecology of Gerreidae, Bleeker 1859, in the estuaries of Natal. J. Fish. Biol. 221373-394. CYRUS, D. P., AND S. J. M. BLABER. 1983b. Diet of Gerres fry in the Kosi system. S. Afr. J. Zool. 18: 403-406. CYRUS,D. P., ANDS. J. M. BLABER. 1984. The feeding ecology of Gerreidae (Teleostei) in the Kosi system, with special reference to their seasonal diet. Lammergeyer 32135-49. DEAN,D. 1979. The swimming ofbloodworms (Glycera spp.) at night, with comments on other species. Mar. Biol. 48199-104. GILMORE,R. G., JR. 1977. Fishes of the Indian River lagoon and adjacent waters, Florida. Bull. Fla. State Museum Biol. Sci. 221101-147. HYSLOP,E. J. 1980. Stomach content analysis-a review of methods and their application. J. Fish Biol. 17:41 l-429. KINCH, J. C. 1979. Trophic habits of the juvenile fishes within artificial waterways-Marco Island, Florida. Contrib. Mar. Sci. 22~77-90. LIVINGSTON, R. J. 1982. Trophic organization of fishes in a coastal seagrass system. Mar. Biol. 7: 1-12. ODUM, W. E. 1970. Pathways of energy flow in a south Florida estuary. Ph.D. Dissertation, University of Miami. 162 p. RANDALL,J. E. 1967. Food habits of reef fishes of the West Indies. Proceedings of the International Conference on Tropical Oceanography. Nov. 17-24, 1965. Miami Beach, Florida. University of Miami Inst. of Mar. Sci. RAO, A. V. P. 1968. Observations on the food and feeding habits of Gerres oyena (For&al) and Gerres filamentosus Cuvier from the Pulicat Lake with notes on the food of allied species. J. Mar. Biol. Assoc. India 10:332-346. REID, G. K., JR. 1954. An ecological study of the Gulf of Mexico fishes, in the vicinity of Cedar Key, Florida. Bull. Mar. Sci. GulfCaribb. 4:1-94. SCHOENER, T. W. 1974. Resource partitioning in ecological communities. Science 185:27-39. SPRINGER,V. G., AND K. D. WOODBURN. 1960. An ecological study of the fishes of the Tampa Bay area. Fla. State Board Cons. Mar. Lab. Contribution No. 36. 107 p. STONER,A. W. 1980. Feeding ecology of Lagodon rhomboides (Pisces: Sparidae): variation and functional responses. Fish. Bull. 78~337-352. THOMPSON,M. J. 1976. Photomapping and species composition of the seagrass beds in Florida’s Indian River estuary. Harbor Branch Technical Report No. 10. 34 p. ZIEMAN,J. C. 1982. The ecology of the seagrasses of south Florida: a communitv profile. U.S. Fish and Wildl. Svcs. Office of Biol. Svcs., Washington, D.C. FWS/OBS 82/25. 158 p. Received for consideration, December 5, 1984 Acceptedfor publication, June 6, 1985
