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Northeast Gulf Science Volume 9 Article 5 Number 2 Number 2

12-1987 The Relative Abundance and Feeding Habits of Juvenile Kingfish (: ) in a Gulf of Mexico Surf Zone Robert H. McMichael Jr. University of Southern Mississippi

Stephen T. Ross University of Southern Mississippi

DOI: 10.18785/negs.0902.05 Follow this and additional works at: https://aquila.usm.edu/goms

Recommended Citation McMichael, R. H. Jr. and S. T. Ross. 1987. The Relative Abundance and Feeding Habits of Juvenile Kingfish (Sciaenidae: Menticirrhus) in a Gulf of Mexico Surf Zone. Northeast Gulf Science 9 (2). Retrieved from https://aquila.usm.edu/goms/vol9/iss2/5

This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf of Mexico Science by an authorized editor of The Aquila Digital Community. For more information, please contact [email protected]. McMichael and Ross: The Relative Abundance and Feeding Habits of Juvenile Kingfish (S Northeast Gulf Science Vol. 9 No. 2, December 1987 p. 109-123

THE RELATIVE ABUNDANCE AND FEEDING HABITS OF JUVENILE KINGFISH (SCIAENIDAE: Menticirrhus) IN A GULF OF MEXICO SURF ZONE

Robert H. McMichael, Jr. 1 and Stephen T. Ross2

Department of Biological Sciences University of Southern Mississippi Hattiesburg, MS 39406-5018

ABSTRACT: We describe seasonal and diel occurrence patterns, density, dietary progres­ sions, and trophic relationships of Menticirrhus littoralis, M. americanus and M. saxatitis collected from the Horn Island, Mississippi, surf zone. Menticirrhus littoralis was the most abundant species (62.7%), followed by M. american us (21.8%) and M. saxatitis (15.5%). Den­ sities were highest during spring and summer and decreased markedly during the winter. Species showed diel changes in abundance, with abundance increasing during dusk and dawn forM. littoralis, and during the day forM. americanus and M. saxatilis. All three species showed ontogenetic progressions in diet, with siphon tips from Donax spp., cumaceans and mysids being most important to smaller (<80 mm SL) M. littoralis and M. americanus; cumaceans, mysids and amphipods were most important to smaller M. saxatitis. Larger in· dividuals of all three species fed more on whole Donax, , Emerita talpoida, brachyurans, and fishes. Both intra- and interspecific dietary overlap was greatest for the smaller size groups of juveniles and declined with growth. Dietary overlap between 20 mm size classes was greatest for intra- compared to interspecific comparisons.

The Menticirrhus complex of the have reported them from estuaries as northern Gulf of Mexico consists of three well (Bearden 1963; Schaefer 1965). Adult species, M. americanus (southern northern kingfish move into deeper water kingfish), M. saxatilis (northern kingfish), with increasing age (Schaefer 1965; Irwin and M. littoralis (gulf kingfish). Juveniles 1970). Southern kingfish are less of these species occur in various inshore restricted to surf zones as juveniles, marine habitats (Springer and Woodburn often occurring in low salinity estuaries. 1960; Irwin 1970; Crowe 1984) and may Adult southern kingfish are thought to co-occur in surf zones (Naughton and leave the inner coastal and surf zone Saloman 1978; Modde and Ross 1981). areas for deeper, more saline water, Juvenile gulf kingfish are strongly especially with the onset of cold weather associated with surf zones of moderate (Bearden 1963; Irwin 1970; Crowe 1984). to high salinities (Modde and Ross 1981), Recently, Smith and Wenner (1985) found and adults apparently remain in relatively that southern kingfish from the South shallow water (<36 m) near such areas Atlantic Bight moved south during the (Gunter 1945; Irwin 1970; Christmas and winter, rather than simply moving into Waller 1973; Darovec 1983). Juvenile nor­ deeper water at the same latitude. thern kingfish also occur primarily in Surf zones in the Gulf of Mexico are outer surf zone habitats (Irwin 1970; important as nursery areas for many fish Johnson 1978), although various studies species (Mod de and Ross 1981; Ross 1983; Ross et a/. 1987b), even though 'Present Address: Florida Department of Natural such areas are physically dynamic. Resources, Bureau of Marine Research, 100 Eighth Ave., S.E., St. Petersburg, FL 33701-5095. Modde and Ross (1983) found that cer­ •Authorship decided by a coin toss. tain species from the Horn Island surf

Published by The Aquila Digital Community, 1987 109 1 Gulf of Mexico Science, Vol. 9 [1987], No. 2, Art. 5 110 McMichael, R.H. Jr. and S.T. Ross Juvenile kingfish abundance and feeding 111

zone showed partitioning of food by no more than 1.2 km wide. The center a subjective scale from 0 (empty) to 5 which results when a few individuals resources by prey kind and size, as well of the island is located at 30°14'N, (full). consume very large prey items (Mathur as through temporal separation of food 88°40'W. The Horn Island surf zone is Diets were described by percent oc­ 1977; Wallace 1981). Because of the ef­ and habitat use. Such "resource parti­ characterized by a sand substratum, currence (F), total number (N) and total fect of small samples on the reliability of tioning" may be due to coevolution of moderate wave activity and no rooted volume (V) of each prey item. These overlap measures (Wallace and Ramsey surf zone species, but may also be due vegetation. methods have been reviewed by Hynes 1983), we grouped fishes into 20 mm SL to historical or environmental effects We sampled monthly from March, (1950), Windell (1971) and Hyslop (1980). intervals to retain sufficient sample (Wiens 1977; 1984; James et a/. 1984; 1978 through September, 1979 at Sta­ Prey volume was measured by a sizes, while still keeping size groups fair­ Ross et a/. 1987a). Thus, while it is tions 1 and 4 of Modde and Ross (1981). displacement technique, or by a squash ly homogeneous. generally not possible to understand The April, 1978 and March, 1979 sampl­ technique (Hellawell and Abel1971; Ross causation from observational field ing periods were omitted due to adverse 1974) when prey volume was visually RESULTS 3 studies (e.g. Connor and Simberloff weather. We made diel collections over estimated as <.05 cm • Specimens with 1986), it is important to document pat­ a 24 h period in July, August and Oc­ empty stomachs were not used in com­ Seasonal Occurrence terns of resource use so that there is a tober, 1978, and April, May and June, puting measures of dietary importance basis for formulating testable 1979. All other collections were between of prey kinds. During the 17 month study period hypotheses regarding the underlying 0900 and 1600 CST. During the day we As a criterion for sample size in food we collected 1,192 kingfish. Menticirrhus mechanisms (Ross 1986). took two samples at each station and habit analyses, we plotted cumulative littoralis was the most abundant of the Due to the increasing habitat time period; at night we made only one new prey taxa against cumulative three species, comprising 62.7% of the divergence associated with growth, the sample per time period at a single stomachs examined. A minimal sample kingfish catch by number, followed by M. early juvenile stage is the period of station. size, sufficient for description of prey americanus (21.8%) and M. saxatilis greatest potential ecological overlap of We used three types of sampling taxa, is indicated when the curve reaches (15.5%). Menticirrhus littoralis also had the three kingfish species in the northern gear; 1) A 9.1 x 1.8 m, 3.2mm bar mesh a horizontal asymptote. When all sizes the greatest frequency of occurrence in Gulf of Mexico. However, most bag sein~ - used from March, 1978 were combined approximately 35 gulf seine hauls (66.7%), again followed by M. ecological studies of Menticirrhus have through June, 1978 and periodically kingfish (excluding fish with empty americanus (29.7%) and M. saxatilis either emphasized only late juvenile to thereafter; 2) A 50 x 1.8m, 3.2mm bar stomachs), and 15 southern and northern (24.6%). adult forms (e.g. Bearden 1963), or have mesh, block seine, with a 1.83m2 bag kingfish were required to meet our Kingfish abundance varied only considered a single species (e.g. located 7.6 m from one end- used from criterion. Because adequate sample size seasonally, with the highest abundance Schaefer 1965; Crowe 1984). As recently July, 1978 through September, 1979; and changes as the diet varies, or as the size from June through October (Fig. 1). Both summarized by Ross (1986), an 3) An 18m experimental gill net - used distribution of the predators changes, we frequency of occurrence and abundance understanding of resource requirements periodically during the study to collect tested each size class where com­ decreased rapidly during the fall and and interactions within a taxocene ideal­ larger fishes. The 50 m block seine was parisons were made. All dietary com­ winter months, and no kingfish were ly requires an examination of all life set around poles to enclose a 300 m2 parisons met our criterion for adequate taken in December, 1978, or January, history stages. Our purpose in this paper area. Procedures for using this net are sample size unless so specified. 1979. is to expand the knowledge of resource described in Ross eta/. (1987b). Comparisons of food habits bet­ Gulf kingfish first appeared in the differences of. these species by examin­ Fishes were fixed in 10% formalin ween species were made using surf zone as juveniles (10-20 mm) in May, ing resource use of the co-occurring and larger specimens were injected in­ Schoener's (1968) index of proportional 1979, and density increased during juvenile forms. Specifically, we describe traperitoneally to halt digestion. In the . overlap based on mean food volume, spring and early summer reaching 14 per seasonal and diel occurrence patterns, laboratory, specimens were identified, following recommendations of Wallace 100m2 by August, 1979. Specimens taken densities, trophic relationships and weighed (to the nearest 0.1 g), and (1981) and Linton eta/. (1981). The index during summer collections ranged from dietary progressions. grouped into 20 mm standard length (Sl) ranges from 0 (no overlap) to 1 (total 5-270 mm SL (fish >150 mm were cap­ intervals. For food analyses, the portion overlap). While there is not a simple tured primarily during qualitative sampl­ METHODS AND MATERIALS of the alimentary tract between the statistical test of what constitutes a ing by the gill net), but most were less esophagus and the pylorus, hereafter significant value, we followed current than 50 mm, with 21-30 mm fish making The study sites were in the surf zone called the stomach, was removed. All practice (e.g. Galat and Vucinich 1983) in up 60%,70% and 84% of the individuals on the south shore of Horn Island, contents were identified to the lowest considering overlap index values > 0.60 collected for May, June, and July, 1979, Mississippi. Horn Island lies approx­ taxonomic level possible. The fullness of to indicate substantial overlap. Use of respectively. Recruitment into the surf imately 14 km offshore and is 19 km long each stomach was estimated based on mean prey volume lessens the bias zone by 10-20 mm fish continued through https://aquila.usm.edu/goms/vol9/iss2/5 2 DOI: 10.18785/negs.0902.05 McMichael and Ross: The Relative Abundance and Feeding Habits of Juvenile Kingfish (S 112 McMichael, R.H. Jr. and S.T. Ross Juvenile kingfish abundance and feeding 113

Table 1. Percent occurrence, number and volume of prey organisms of Menticirrhus littora/is collected the summer, with 5-10 mm fish occurring 80 mm were collected with the gill net. between March, 1978 and June, 1979 (N = 423). as late as October. The minimum size for Southern kingfish were not collected bet­ PREY CATEGORY % OCCURRENCE %NUMBER %VOLUME the November, 1978, collection was 20 ween November, 1978 and May, 1979. mm, suggesting that recruitment into the The recruitment period for northern Pelecypoda (siphon tubes) 50.7 64.00 15.40 surf zone had ended. kingfish was more limited with juvenile 34.7 7.90 17.90 Data for both M. america nus and M. fish (10-20 mm) only being collected in Cumacea (Oxyurostylis sp.) 18.4 9.90 4.20 Emerita talpoida 16.3 3.10 19.70 saxatilis suggest that abundances were May, 1978 and June-July, 1979. Northern Mysidacea (Metamysidopsis sp.) 9.7 5.60 3.30 highest in June, 1979, preceding the peak kingfish ranged from 10-130 mm, with Calanoidea 7.3 4.00 0.70 density of gulf kingfish (Fig. 1). Southern fish less than 50 mm most common. Pelecypoda (entire) 3.8 3.30 17.90 kingfish first appeared in the surf as Brachyura (Callinectes sp.) 3.5 1.00 17.40 Gammaridea 2.8 0.50 0.60 juveniles (10-20 mm) in May, 1978 and Diel Occurrence Patterns lsopoda 2.6 0.40 0.40 June 1979 and recruitment of early Vegetation 0.9 0.10 0.30 juveniles continued into October. Fish Diel estimates of density for M. lit­ Fishes 0.7 0.10 0.20 Caligoidea 0.5 0.10 0.03 were between 10-225 mm, and all fish> fora/is in July and October, 1978, and Brachyur<:!.n megalops 0.5 0.10 0.03 Caprellidea 0.2 0.03 0.03 20 Unidentified material 0.90 remains 0.30 M. littora lis C\1E 15 0 0,...... Mentjcjrrhus ljttora!ls ..c: 10 (/) u.

5 July 1978

2 6

A 5 0 N D F M A M A 5 15

(\J E M. america nus 0 10 ~ ,...0 >-E"' f-0 ...... -o ..c: (JJ..- October 1978 (/) z-- u. 5 cgw~ +--...... __ -- 1\ / A 5 0 N D F M A M A 5

(\J 10 E 7 0 M. saxatilis e 0 5 ::: 5 4 ..c: June 1979 (/) u. 3 .,.._._ A 5 0 N D F M A M A 5 1978 1979 0900 0900 Figure 1. Mean number ( 1 SE) of Menticirrhus littora/is, M. americanus and M. saxatilis collected + /- TIME from Horn Island, July, 1978-Sept., 1979. Asterisks indicate the time period of samples taken with the 9.1 m net (catch = 0); all other samples were taken with the 50 m net. For dates with only two samples, Figure 2. Densities of Menticirrhus littoralis collected at different times (CST) during July and October, the vertical line is the range, the horizontal line the midpoint. Number above the ranges are seine hauls. 1978, and June, 1979. Shading indicates night samples; ss = sunset, sr = sunrise. Published by The Aquila Digital Community, 1987 3 114 McMichael, R.H. Jr. and S.T. Ross Gulf of Mexico Science, Vol. 9 [1987], No. 2, Art. 5 Juvenile kingfish abundance and feeding 115

June, 1979 (months of their greatest 24 Whitney U-Test, .1>P>.05) (Fig. 3). Peak h representation), showed significant in­ abundance of these species fell within creases during times of astronomical our regular monthly sampling times so July 1978 sunset and sunrise ( + /- 1h; Mann­ that monthly samples should be Whitney U-Test, P<.05) (Fig. 2). However, representative of maximal abundance. total densities did not differ between day and night, either when tested separate­ Food Habits ly for each month or for the three diel .M.. amerjcaoys sample months combined (Mann­ Menticirrhus littora/is ;; >-E June 1979 Whitney U-Test, P>.05). Overall, pelecypod siphon tips i-0 -o Numbers of M. americanus and M. (/)~ (predominantly Donax spp.) were the Z'.<: Ww saxatilis collected over any 24 h period most important prey on the basis of OiL were relatively low. However, diurnal den­ number and percent occurrence, and sities for July, 1978 and June, 1979 fifth in importance on the basis of (months of greatest 24 h representation volume (Table 1). Other important prey of these species) significantly exceeded (on the basis of percent occurrence, .M.. saxatllls night densities forM. americanus (Mann­ number or volume) were polychaetes Whitney U-Test, P<.05), and approached (primarily Nephtyidae), Emerita talpoida June 1979 significance for M. saxatilis (Mann- and cumaceans (Oxyurostylis sp.). 36 58 34 18 100

POLYCH,c\ETA MISC. MISC. MISC. 90 TIME , ISOPODA EAIERI A Figure 3. Densities of and M. saxati/is coi.lected at different times (CST) di.jr­ BRACHYURA loii'GAI_OPS ISOPODA ing July, 1978 and June, 1979. Shading indicates night samples; ss sunset, sr sunrise. MYSIDACEA FISHES EMERirA = = 80 MYSIDACEA EMERITA COPEPODA 105 156 105 20 9 16 ISOPODA 100 MEGALOPS MISC. POLYCHAETA MISC. MISC. MISC. MISC. MISC. 70 • COPEPODA COPEPODA BRACHYURA 90 COPEPODA CUMACEA OONAX E"AIE"RirA MYSIDACEA I&J FISHES VEGETATI N ::E CUMACEA OONAX POLYCHAETA 80 COPEPODA MYSIIiACEA E"AIE"RirA VEGETATION 3 60 AMPHIPODA 0 PELECYPOD BRACHYURA FISHES CUMACEA > AMPHIPODA OONAX 70 SIPHONS .... POLYCHAETA z 50 CUMACEA AMPHIPODA w I&J :IE 0 PELECYPOD 3 60 a: 0 POLYCHAETA I&J CUMACEA > 0.. 40 SIPHONS ... POLYCHAETA POLYCHAETA E"ME"RirA ill 50 I&J - (!) 0 E"AIE"R/rA POLYCHAETA a:: ~ w a: 0.. 40 . UJ 30 AMPHIPODA w MYSIDACEA ~ POLYCHAETA ~ a:: MYSIDACEA w 30 20 PELECYPOD BRACHYURA ~ PELECYPOD PELECYPOD 20 SIPHONS PELECYPOD SIPHONS SIPHONS PELECYPOD E"AIE"RirA POLYCHAETA SIPHONS 10 - 10 CUMACEA BRACHYURA SIPHONS

0 0 <20 21-40 41-60 61-80 100-120 >140 20 21-40 41-60 61-80 SL (mm) SL (mm) Figure 4. Average proportional volume of major(> 2% volume) food items from Menticirrhus fittora/is Figure 5. Average proportional volume of major(> 2% volume) food items from Menticirrhus americanus, in 20 mm SL size classes, collected from the Horn Island surf, March, 1978- June, 1979. N = numbe~ in 20 mm SL size classes, collected from the Horn Island surf, March, 1978- June, 1979. See Fig. 4 for of stomachs examined which contained food. Misc. = prey taxa contributing< 2% proportional volume. further information. https://aquila.usm.edu/goms/vol9/iss2/5 4 DOI: 10.18785/negs.0902.05 McMichael and Ross: The Relative Abundance and Feeding Habits of Juvenile Kingfish (S Juvenile kingfish abundance and feeding 117 116 McMichael, R.H. Jr. and S.T. Ross

Table 2. Overlap based on average proportional volume of prey items for 20 mm SL size classes of Men­ tant prey on the basis of percent occur­ cumaceans, copepods and mysids (Fig. ticirrhus. Sample sizes are shown in parentheses for each group which met our criterion of minimum sample size. L = Menticirrhus littoralis; A = M. americanus; S = M. saxatilis. 1 = <20 mm; 2 = 21·40 rence and number, and ranked sixth in 5). Diets of fish between 21-60 mm were mm; 3 = 41-60 mm; 4= 61-80 mm; 5 = 81-100 mm; 6 = 101-120 mm; a = >141 mm. Values ~0.60 are importance by volume (Table 3). more varied, but showed a decline in the underlined; long dashed lines undersore intraspecific comparisons. However, unlike gulf kingfish, siphon tips volumetric importance of siphon tips, occurred in less than one-third of the cumaceans and mysids, and increased (105) (156) (105) (20) (9) (14) (36) (58) (34) (18) (68) (24) (15) L-1 L-2 L-3 L-4 L-6 L-8 A-1 A-2 A-3 A-4 S-3 S-4 S-5 southern kingfish stomachs, reflecting importance of polychaetes and am­ L-2 .64 the broader food spectrum of this phipods. Larger fish (61-80 mm SL) ob­ L-3 .46 .77 species. Cumaceans, brachyurans, am­ tained the bulk of their prey volume from L-4 .45 .63 .74 L-6 .24 .33 .51 .50 phipods, polychaetes, mysids and fishes brachyurans, amphipods, fishes and L-8 .30 .39 .42 .45 .73 were also important prey taxa (on the polychaetes. Dietary overlap was again basis of percent occurrence, number or highest between adjacent 20 mm SL size A-1 .65 .61 .46 .48 .06 .11 A-2 .68 .61 .43 .49 .18 .28 .64 volume) . groups (Table 2). A-3 .52 .52 .44 .47 .35 .39 .36 &1 An ontogenetic dietary progression A-4 .21 .20 .15 .23 .34 .47 .21 .42 .51 is apparent with smaller southern kingfish (<41 mm) obtaining the largest Cumaceans were the most impor­ S-3 .65 .40 .20 .30 .23 .33 .51 .61 .60 .53 S-4 .44 .31 .12 .21 .21 .31 .33 .59 .49 .52 .68 food volume from pelecypod siphons, tant prey on the basis of percent occur- S-5 .36 .28 .35 .46 .54 .56 .23 .47 .43 .54 .54 .66 24 15 100 68 MISC. MISC. MISC. IM. Gulf kingfish showed strong volumetrically important prey over all 90 ISOPOD A - AMPHIPODA evidence of an ontogenetic dietary pro­ size groups. Fragments of seagrass BRACHYURA gression. A feeding transition occurred blades also were consumed by larger EMERITA 80 at about 60-80 mm SL, with smaller fish fish. The !lighest overlap b13tween 20 mm - FISHES POLYCHAETA obtaining most of their prey volume from SL size \classes generally occurred AMPHIPODA pelecypod siphons, polychaetes, cuma­ among adjacent size groups, providing 70 .. ceans and mysids, and larger fish obtain­ further evidence of dietary changes with LLI POLYCHAETA ::::E BRACHYURA MYSIDACEA ing most of their prey volume from increasing length (Table 2). ::J .J 60 Emerita talpoida, polychaetes, 0 - brachyurans and whole pelecypods Menticirrhus americanus > I- AMPHIPODA CUMACEA (Donax spp.) (Fig. 4). Polychaetes were Pelecypod siphon tips were impor- z 50 LLI - BRACHYURA (..) 0:: Table 3. Percent occurrence, number and volume of prey organisms of Menticirrhus americanus col­ LLI lected between March, 1978 and June, 1979 (N = 147). 0.. 40 LLI - PREY CATEGORY % OCCURRENCE % NUMBER % VOLUME (!) MYSIDACEA ~ MYSIDACEA 0:: FISHES LLI 30 Pelecypoda (siphon tubes) 28.6 37.40 6.80 - Cumacea (Oxyurostylis sp.) 24.5 19.20 4.70 ~ Mysidacea (Metamysidopsis sp.) 16.3 5.40 7.90 20 Polychaeta 15.0 6.20 8.40 - Brachyura (Callinectes sp.) 12.9 11.90 29.00 CUMACEA Gammaridea 12.9 4.00 13.80 FISHES EMERITA Isopod a 8.2 2.80 3.00 10 Fishes 7.5 2.20 16.40 - Calinoidea 6.8 7.20 1.10 Emerita tatpoida 2.7 1.60 1.70 0 Brachyuran megalops 2.7 1.00 0.90 41-60 61-80 81-100 Caligoidea 2.7 1.00 0.70 S L (mm) Caprellidea 0.7 0.20 0.30 Figure 6. Average proportional volume of major(> 2% volume) food items from Menticirrhus saxatilis, Unidentified material 4.40 in 20 mm SL size classes, collected from the Horn Island surf, March, 1978- June, 1979. See Fig. 4 for 1.10 Crustacean remains further information.

Published by The Aquila Digital Community, 1987 5 118 McMichael, R.H. Jr. and S.T. Ross Gulf of Mexico Science, Vol. 9 [1987], No. 2, Art. 5 Juvenile kingfish abundance and feeding 119

Table 4. Percent occurrence, number and volume of prey organisms of Menticirrhus saxatilis collected Table 5. Size range, month (interval from January-August) of earliest occurrence of the smallest size between March, 1978 and June, 1979 (N =129). grqup, and the three months of greatest kingfish abundance for juvenile or adult kingfish in surf zones. Data are arranged by decreasing latitude of collection sites. PREY CATEGORY % OCCURRENCE % NUMBER % VOLUME

Menticirrhus littoralis Cumacea (Oxyurostylis sp.) 37.2 72.40 9.40 Mysidacea (Metamysidopsis sp.) 24.8 11.10 13.60 Size range (mm) First Greatest Location Reference Pelecypoda (siphon tubes) 22.3 0.60 0.30 Occurrence Abundance Polychaeta 20.9 4.40 31.10 Gammaridea 19.4 2.60 8.50 83-145 January July-September Folly Beach, NC Anderson et at. (1977) Fishes 17.8 2.10 18.50 69-112 March July-September exposed beaches, SC Cupka (1972) Brachyura (Callinectes sp.) , 16.3 3.80 9.40 18·22 May Sapelo Beach, GA Dahlberg (1972) Emerita talpoida 5.4 0.60 3.30 10·20 May August Horn Island, MS present study Isopod a 5.4 0.80 1.20 11-15 August, 1975 August-October Horn Island, MS Modde (1980) Brachyuran megalops 2.3 0.80 0.40 11-15 May, 1976 August-October Horn Island, MS Modde (1980) Calanoidea · 1.6 0.80 0.20 16-20 April, 1977 June &September Horn Island, MS Modde (1980) Brachyuran zoea 0.8 0.10 0.10 January June-July St. Andrews Bay, FL Naughton & Saloman (1978) Caligoidea 0.8 0.10 0.11 February July-September Mustang Island, TX Gunter (1945) Unidentified material 3.50 February July-August Mustang Island, TX McFarland (1963) Crustacean remains 0.60 9-25 June July Pinellas Co., FL Springer and Woodburn (1960) 24·193 January July-September Pinellas Co., FL Saloman and Naughton (1979) renee and number, and ranked fourth in sjgnificantly greater for intraspecific importance by volume (Table 4). Addi­ (i<'= .51) than interspecific comparisons tional food items of importance (on the (X".'= .40; Mann-Whitney U-Test, P < .05). basis of percent occurrence, number or Thus, the three species showed some Menticirrhus saxatilis volume) were polychaetes, mysids, divergence in food habits. As occurred Size range (mm) First Greatest Location Reference Occurrence Abundance fishes (principally Anchoa spp.), gam­ with intraspecific comparisons, the marids and brachyurans. While hig~est values of interspecific overlap 13-26 July July-August Morris Cove, CN Warfel & Merriman (1944) pelecypod siphons occurred in 22% of were among the smaller size groups. 220.410* May May-June Fire Island, NY Schaefer (1967) the stomachs, their contribution to the 33·50 June June Folly Beach, NC Anderson et at. (1977) 18-88 June June exposed beaches, SC Cupka (1972) diet in terms of number or volume was DISCUSSION 17·50 April Sapelo Beach, GA Dahlberg (1972) low. Few fish (N = 6) larger than 90 mm 10-20 May June Horn Island, MS present study were captured which contained food, The three species of kingfish all are 6·10 April Horn Island, MS Modde (1980) primarily spring and summer inhabitants January December St. Andrews Bay, FL Naughton & Saloman (1978) and the sample size was also insufficient March June Mustang Island, TX McFarland (1963) to describe the diet of the smallest size of the Horn Island surf zone, a pattern 47-93 January May-July Pinellas Co., FL Saloman &Naughton (1979) class. Thus the diet description is bias­ typical for many other surf inhabiting ed towards intermediate sized fish. species in the Gulf of Mexico (e.g. Ross While the data are limited, an on­ 1983; Ross eta/. 1987b). Peak abundance Menticirrhus americanus togenetic dietary progression is apparent of the numerically dominant Menticir­ for fish between 40-100 mm (Fig. 6). The rhus littoralis followed peak abundances Size range (mm) First Greatest Location Reference Occurrence Abundance contribution of cumaceans and am­ of M. saxatilis and M. americanus; phipods to dietary food volume decreas­ however, the three species cooccur in 24 June exposed beaches, SC Cu pka (1972) ed with fish size, while the contribution the surf zone from June to October. The 11·15 May May-July Sapelo Beach, GA Dahlberg (1972) of fishes, brachyurans and Emerita in­ difference in timing of peak abundance 10-20 May June Horn Island, MS present study July August-October St. Andrews, Bay, FL Naughton &Saloman (1978) creased. The limited data on in­ of kingfish may be meaningful, although July July Mustang Island, TX Gunter (1945) traspecific overlap indicates the greatest times of greatest abundances of kingfish March May Mustang Island, TX McFarland (1963) dietary similarity between adjacent 20 in surf zones are variable for Gulf of Mex­ 25-45 July July, August Pinellas Co., FL Springer and Woodburn (1960) Pinellas Co., FL mm size groups. ico and Atlantic studies (Table 5). Gulf June June-July Saloman & Naughton (1979) 'I kingfish tend to have their greatest abun­ I Interspecific Overlap dance during July and August, while nor­ *fork length thern kingfish generally show earlier Overall, dietary overlap was (primarily May-June) peaks, at least for

https://aquila.usm.edu/goms/vol9/iss2/5 6 DOI: 10.18785/negs.0902.05 Ji ... 120 McMichael, R.H. Jr. and S.T. Ross McMichael and Ross: The Relative Abundance and Feeding Habits of Juvenile Kingfish (S Juvenile kingfish abundance and feeding 121

more southern localities. Studies of and Woodburn 1960; Irwin 1970; Chao even planktonic prey. Modde (1979) and the physical harshness of the habitat, southern kingfish indicate peak densities and Musick 1977). The food habits of M. Modde and Ross (1983) also found small the dietary separation and tendencies for between May and August, dates general­ americanus have been studied in more juvenile M. littoralis (<20 mm) to be seasonal and diel separation in habitat ly overlapping with gulf kingfish. Modde detail than the other two species (e.g. planktivores, feeding almost exclusively use may more likely reflect events and Ross (1981) found that water Smith 1907; Hildebrand and Schroeder on mysids, but shifting to pelecypod mediated primariy by anti-predation temperature was the dominant 1928; Hildebrand and Cable 1934; Miles siphons, polychaetes and mole responses and/or reproductive biology parameter affecting the frequency of gulf 1949; Pew 1954; Reid 1954; Viosca 1959; with growth. Joseph (1962), working with than present or historical selection for kingfish in the surf zone, so differences Irwin 1970; Fritzche and Crowe 1981). the eastern Pacific M. undulatus, resource separation during periods of between the three species, if real, However, only Springer and Woodburn reported a similar size related diet pro­ lower food abundances. For instance, might reflect differing temperature (1960) examined southern kingfish from gression in that fish less than 50 mm fed Ross et a/. (1985) summarized studies preferences. a surf zone area. Major food items includ­ primarily on mysids and amphipods, showing greater biological control of fish The spring (May) initiation of recruit­ ed polychaetes, crabs, mysids and while fish between 50 and 100 mm fed assemblages in benign compared to ment of the three juvenile kingfish Emerita. Our findings generally agree primarily on pelecypod siphon tips harsh environments. Thorman and species reported in this study generally with the published information on food (Donax gould!). Individuals larger than Wiederholm (1983; 1984; 1986) also found agrees with other work done in the Gulf habits of the three species, except for 100 mm fed mainly on Emerita analoga fish assemblages in the environmental­ of Mexico, with times ranging from April the importance of pelecypod siphons in and smaller fishes. ly harsh Bothnian Sea to be controlled to August for fishes < 50 mm SL (Table gulf and southern kingfish. Seagrass In part, ontogenetic changes in food more·by abiotic than biotic interactions. 5). These data corroborate the reported fragments in gulf kingfish were likely habits may be functionally related to the Because of the difficulty of conducting spring-summer spawning seasons for consumed incidentally to ingestion of presence of a swimbladder. Smaller in­ controlled field experiments in the surf kingfish in the northern Gulf of Mexico epiphytes. dividuals of M. americanus and M. sax­ zone, choosing between the alternatives (Irwin 1970; Darovec 1983). However, The primary prey of juvenile gulf atilis have swimbladders, fascilitating of primarily biotic versus abiotic spawning seasons of Menticirrhus are kingfish were pelecypod siphon tips. movements into the water column assemblage control will be difficult at often protracted and may vary with While other studies on the food habits of (Bearden 1963; Irwin 1970). With increas­ best. Perhaps, as pointed out by Conner latitude (Smith and Wenner 1985). this spe6ies have reported the presence ing fish size the swimbladders of and Simberloff (1986), the best approach Minor diel changes in abundance of pelecypods (e.g. Springer and Wood­ southern and northern kingfish become lies in the use of null hypotheses and occurred among the three kingfish, with burn 1960), only Modde (1979) and Modde less functional and the fishes apparent­ models. gulf kingfish being most abundant in the and Ross (1983) listed siphon tips ~s im­ ly forage less in the water column. Gulf morning and evening, and southern and portant food items. Pelecypod siphons kingfish lack swimbladders even as ACKNOWLEDGMENTS northern kingfish (although to a lesser were also an important dietary compo­ juveniles (Irwin 1970; N = 50, size <60 extent) more abundant during the day. nent of southern kingfish. Browsing on mm; Ross pers. obs., N = 28, size 18-86 We are indebted to the many people These results differ from Modde and infaunal invertebrates by fishes has been mm SL). who assisted in field collecting, par­ Ross (1981) who did not find a distinct observed in other systems (e.g. Woodin The three species of kingfish show­ ticularly David Ruple and Warren Gard­ diel abundance pattern for gulf kingfish, 1982; Peterson and Quammen 1982; de ed the greatest dietary overlaps as ner. We thank Jeff Billings for his help although their data showed a tendency VIas 1985), and may be an important juveniles. However, overlap of size with computer programming, and Robert for early afternoon and evening abun­ energy pathway from particulate organic groups was greater within than between C. Maris for help with invertebrate iden­ dance peaks. matter and primary production to higher size groups of species. The average in­ tification. We acknowledge the generous Previous studies of gulf kingfish consumer levels in the surf zone terspecific overlap was only 40%, a level support from the Biology Department, have listed small , molluscs, environment. that Ross (1986) used as the cutoff point University of Southern Mississippi. fishes and polychaetes as important prey Although it is difficult to assign for indicating the presence of substan­ Stephen Shabica, Coastal Field items (Gunter 1945; Breder 1948; Viosca water column positions to prey in the tur­ tial resource separation. While we did Research Laboratory, National Park Ser­ 1959; Springer and Woodburn 1960; Irwin bulent surf zone, adults of the three not attempt ro measure food abundance, vice, was especially helpful in providing 1970). Juvenile northern kingfish (13-30 kingfish species appear to be demersal it seems unlikely that food is often sampling gear and boat time. We also mm) are known to feed on copepods, feeders, as reported by previous studies limiting in the surf zone environment. thank the National Park Service, Gulf mysids, crabs and gammarid amphipods (e.g. Trewavas Chao and Musick 1964; Prey of planktonic origin would be con­ Island National Seashore, for allowing us while larger individuals feed on mole 1977). However, we observed strong on­ tinually brought into the surf zone by to collect on Horn Island. We thank crabs, amphipods, mysids, hermit crabs, togenetic shifts in food habits, with longshore currents, and benthic prey Doreen McMichael for her support and polychaetes and larval fishes (Springer smaller fishes using more epibenthic, or dislodged by wave action. Because of assistance throughout this study and Published by The Aquila Digital Community, 1987 7 Gulf of Mexico Science, Vol. 9 [1987], No. 2, Art. 5 122 McMichael, R.H. Jr. and S.T. Ross Juvenile kingfish abundance and feeding 123

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