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Northeast Gulf Science Volume 9 Article 2 Number 2 Number 2
12-1987 Food Habits of Blueline Tilefish, Caulolatilus microps, and Snowy Grouper, Epinephelus niveatus, from the Lower Florida Keys Lourdes M. Bielsa Department of Wildlife and Range Sciences
Ronald F. Labisky Department of Wildlife and Range Sciences
DOI: 10.18785/negs.0902.02 Follow this and additional works at: https://aquila.usm.edu/goms
Recommended Citation Bielsa, L. M. and R. F. Labisky. 1987. Food Habits of Blueline Tilefish, Caulolatilus microps, and Snowy Grouper, Epinephelus niveatus, from the Lower Florida Keys. Northeast Gulf Science 9 (2). Retrieved from https://aquila.usm.edu/goms/vol9/iss2/2
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]. Bielsa and Labisky: Food Habits of Blueline Tilefish, Caulolatilus microps, and Snowy
Northeast Gulf Science Vol. 9 No. 2, December 1,987 p. 77·87
FOOD HABITS OF BLUELINE TILEFISH, Cau/olatilus microps, AND SNOWY GROUPER, Epinephelus niveatus, FROM THE LOWER FLORIDA KEYS
Lourdes M. Bielsa1 and Ronald F. Labisky Department of Wildlife and Range Sciences School of Forest Resources and Conservation University of Florida Gainesville, FL 32611
ABSTRACT: Dietary analyses of Intestinal contents from 96 bluellne tlleflsh Caulolatilus microps (mean TL = 528 ± 94 mm SO) and 32 snowy grouper Epinephelus nlveatus (mean TL = 609 ± 146mm SD) collected from the shelf environments (123·256 m) in the lower Florida Keys during July 1980 and May-October 1981, revealed that the two predatory species ex· hlbited different feeding strategies. Bluellne tlleflsh preyed principally on benthic In· vertebrates, and snowy grouper on fish. Copepods, ophluroids, and gastropods comprised 60% of the numerical, and urochordates 40% of the volumetric intestinal contents of bluellne tilefish. Frequency of occurrence of prey consumed by tlleflsh exceeded 50% only for two major taxa - Polychaeta and Natantla. Osteichthyes comprised 47% and 52% of the numerical and volumetric consumption of prey, respectively, by snowy grouper, and occurred in 72% of the Intestines; cephalopods ranked second in numerical importance (18%), and brachyuran crabs second in volumetric Importance (29%). Differences in prey taxa, space niche, and fish anatomy Indicated that bluellne tilefish and snowy grouper occupy different trophic niches, which reduc·e.~ Interspecific competition. Two species of continental shelf Investigational hypotheses were fishes, the blueline tilefish, Cau/olatilus that blueline tilefish and snowy grouper, microps Goode and Bean 1878, and the as predators, have evolved generalized snowy grouper, Epinephelus niveatus feeding strategies to cope with the con (Valenciennes, 1828), are commercially tinental shelf environment, and that exploited in the West-Central Atlantic some degree of niche specialization ex and in the Gulf of Mexico, primarily off ists to facilitate coexistence between the Florida. These species are harvested two species (Bielsa, 1982). Specific ob from the same biotopes, using the same jectives of this study were to determine gear and the same bait; however, little is the dietary components of the blueline known of their life history parameters, tilefish and snowy grouper, and to such as respective trophic niches. elucidate possible trophic interactions The blueline tilefish has been between the predatory fish species. described as an epibenthic browser (Dooley, 1978), and its diet includes MATERIALS AND METHODS polychaetes, mollusks, sipunculids, crustaceans, echinoderms, ascideans, Fish were collected from Atlantic and fish (Ross, 1982). Snowy grouper are offshore waters along the lower Florida presumed to feed near the bottom on Keys, between 24°16'-24°26' N. Latitude fishes, crustaceans, and squid. and 81 °43'-82°0'W. Longitude. Samples were from the commercial catch, taken by hook-and-line at water depths bet 'Current address: Bureau of Marine Research, Florida Department of Natural Resources, 100 ween 123-256 m. Squid was the principal Eighth Avenue S.E., St. Petersburg, FL 33701-5095. bait. Fish were collected in July 1980, Published by The Aquila Digital Community, 1987 1 77 78 Bielsa, L.M. and R.F. Labisky Gulf of Mexico Science, Vol. 9 [1987], No. 2, Art. 2 Foods of blueline tilefish and snowy grouper 79
and in May, June, July, and October 1981. testines from three additional blueline Tab.le 1. List ~f prey taxa identified in intestines of 96 C. microps collected from continental shelf All fish were measured for total length tilefish and seven snowy grouper con envlro~men.ts In the lower Florida Keys. Those taxa preceded by an asterisk (*) designate the lowest taxon 1dent1fied. (mm TL). tained no traces of food, and were ex Both fish species, when raised to cluded from analyses. The tilefish ex *Porifera the surface from deep waters, everted hibited a mean TL of 582 ± 94 mm SD, Cnidarla *Hydrozoa their stomachs because of the decom and a mean ungutted weight of *Schyphozoa pression of the gas bladder. Consequent 2.3'1 ± i .35 kg SD (N = 62). The grouper Anthozoa ly, only intestinal contents were available had a mean TL of 609 ± 146 mm and a *Octocorallia •zoantharia for analysis, which could have biased the mean ungutted weight of 3.35 ± 2.17 kg Mollusca results in favor of food items that were (N = 22). Gastropoda resistant to digestion. Intestines were Prosobranchia removed, labeled, and stored in 10% buf Food Habits of the Blueline Tilefish Fasciolariidae • Fusinus sp. fered formalin. Food items were later Marginelidae removed from the intestines, washed in Copepods, ophiuroids, and • Hyalina c.f. H. avenel/a Dall water, and preserved in 50% isopropyl gastropods comprised 60% of the Atlantidae • Atlanta peronii Lesueur, 1817 alcohol. Intestinal contents were number, but only 16% of the volume of *Turritellidae separated to the lowest identifiable tax prey contained in the intestines of *Bullidae on. Identification was facilitated by texts blueline tilefish (Table 3). Volumetrical *Other (unidentified) Opisthobranchia and keys (Rathbun, 1898, 1925; Benedict, ly, urochordates were the most prevalent Thecosomata 1900; Williams, 1965; Manning, 1969; Pe food item for tilefish (40%), followed by *Cavofinia longirostris (Biainville, 1821) quegnat, 1970; Felder, 1973; Abbott, 1974; ophiuroids (15%). Osteichthyes, due to *Cavofinia cuatridentata (Lesueur) Nelson, 1976; Warner, 1977; Barnes, the large mass of a fish prey consumed *Cavofinia tridentata (Niebuhr, 1775) *Cavolinia uncinata (Range, 1828) 1980). Each taxon was quantified by by a sitlgle tilefish, were third in *Cavolinia sp. number, volume (water displacement), volumetric· importance (13%), but com *Cuvierina sp. and frequency of occurrence of food prised only 2% of the number of items • Hyalocylis striata (Range, 1828) *Creseis acicula (Range, 1828) items. The numerical proportion of each consumed by the tilefish. Frequency of • Creseis sp. food category also was calculated for occurrence of prey found in the in *Clio cuspidata (Bosk, 1802) fish size-class:~ 500 mm, 501-600 mm, testines of tilefish exceeded 50% for on *Clio pyramidata (Linne, 1767) • Diacria trispinosa (Biainville, 1821) 601-700 mm, and~ 701 mm TL for tilefish; ly two major taxa - Polychaeta and Bivalvia and ~ 510 mm, 511-685 mm, and ~ Natantia. Brachyuran crustaceans occur Cardiidae 686 mm TL for grouper. The relative im red in 40% of the intestines. Biogenic • Laevicardium sp. portance of each food category was sediment was found in 58% of the in Nuculanidae • Nuculana sp. determined by computing the index of testines from blueline tilefish. Collective Cephalopoda relative importance (IRI = (N + V) F), ly, as reflected by the IRI, urochordates, *Teuthoidea where N = numerical percentage, V = natantian decapods, and ophiuroids *Other (unidentified) Annelida volumetric percentage; F = frequency of were the three most important foods for Polychaeta occurrence percentage (Pinkas et a/., blueline tilefish, contributing 20%, 19% • Aprhoditidae 1971). The presence or absence of and 18%, respectively, to the overall diet *Giyceridae Goniadidae biogenic sediment also was recorded for of the tilefish (Fig. 1). • Goniada sp. each intestine. Ophiuroids, gastropods, and crusta *Other (unidentified) ceans (copepods, natantian and *Eunicidae RESULTS brachyuran decapods) were the three Onuphidae *Diopatra sp. most important prey taxa consumed by *Other (unidentified) Ninety-seven prey taxa were found tilefish ~ 500 mm TL, comprising 39%, Arabellidae · in the intestines of 96 blueline tilefish 20% and 20% of the number of prey con • Arabella sp. • Lumbrineridae (Table 1), and 17 prey taxa in the in sumed (Table 4). Crustaceans con *Chaetopteridae testines of 32 snowy grouper (Table 2). In- tributed 36% to the numerical occur- • Flabelligeridae https://aquila.usm.edu/goms/vol9/iss2/2 2 DOI: 10.18785/negs.0902.02 Bielsa and Labisky: Food Habits of Blueline Tilefish, Caulolatilus microps, and Snowy Foods of blueline tilefish and snowy grouper 81 80 Bielsa, L.M. and H.F. Labisky Table 1. (cont.) Table 1. (cont.)
• Euprognatha rastellifera marthae (Rathbun) • Capitell idae • Podochela sp. *Sabellidae *Other (unidentified) *Serpulidae Parthenopidae Other • Parthenope agona (Stimpson) • Palacostrema c/dariophilum *Other (unidentified) *Other (unidentified) Tanaidacea *Sipunculida • Apseudidae Prlapulida Isopod a • Priapu/us sp. Cirolanidae Arthropoda • Giro/ana sp. Crustacea • Excirolana sp. *Ostracoda *ldoteidae Copepoda .*Other (unidentified) *Calanoida Amphipoda *Cirripedia Hyperiidae Eumalacostraca *Primo sp. Stomatopoda • Vibilia sp *Pseudosquillidae Aoriidae *Squillidae • Rildardanus sp. Decapoda .*Other (unidentified) Natantia *Other crustaceans (unidentified) Penaeidea *1;3ryozoa Aristeidae Echinodermata *Ceratopsis sp. • Asteroidea Penaeidae Ophiuroidea • Trachypenaeus sp. *Ophiura c.f. 0. sarsi Lutken • Parapenaeus longirostris (Lucas) Echinoidea Caridea *Echinidae Pasiphaeidae *Spatangoida • Parapasiphae su/catifrons (Smith) Urochordata Eugonatonotidae *Ascidacea • Euonatonotus crassus (A. Milne Edwards 1881) Qhordata *Other (unidentified) Osteichthyes Reptantia *Ciupeidae Anomura *Ophichthidae Galatheidae *Gadidae *Munida sp. Sternoptychidae Paguridae • Argyrope/ecus sp. • Py/opagurus sp. *Scaridae Dlogenidae *Other (unidentified) • Dardanus sp. Organic deposits Brachyura *Calcareous deposits Raninidae Inorganic deposits • Ran ilia sp. *Silt • Raninoides sp. *Clay • Lyreides sp. *Other residuals Dromiidae • Dromidia antillensis (Stimpson) *Dromia sp. r~nce in the 501-600 mm TL size class, numerically contributed 55% of the food Homolidae • Homola barbata (Fabricius) and gastropods and ophiuroids, 24% and items in tilefish ::;;. 701 mm TL. Calappidae 19%, respectively. The only numerically *Calappa f/amea (Herbst) important food taxon consumed by Food Habits of the Snowy Grouper • Calappa sp. tilefish in the 601-700 mm TL size class Portunidae • Ba thynectes sp. was crustaceans, which accounted for Osteichthyes was the most impor *Other (unidentified) 81% of the number of prey consumed. tant prey found in the intestines of Majidae Ophiuroids and gastropods, together, grouper (Table 3). This taxon comprised Published by The Aquila Digital Community, 1987 3 82 Bielsa, L.M. and RF. Labisky Gulf of Mexico Science, Vol. 9 [1987], No. 2, Art. 2 Foods of blueline tilefish and snowy grouper 83 Table 2. List of prey taxa identified in intestines of 32 E. niveatus collected from continental shelf en vironments in the lower Florida Keys. Those taxa preceded by an asterisk(*) designate the lowest taxon NATANT lA ------, identified. 1477 (19%) ~---GASTROPODA 794 (10%)
Cnidaria CEPHALOPODA Anthozoa 245 (3%) *Octocorallia COPEPODA Mollusca 271 (4%) *Gastropoda OPHIUROIDEA BRACHYURA 1349 (18%) *Cephalopoda 250 (3%) Annelida Polychaeta *Goniadidae *Other (unidentified) Arthropoda Crustacea OSTEICHTHYES_----/ UROCHORDATA Copepoda 575 (7%) 1530 (20%) *Calanoida Eumalacstraca MISCELLANEOus*______, •stomatopoda 713 (9%) L______POLYCHAETA Decapod a C. microps 551 (7%) Natantia Penaidea Aristeidae •ceratopsis sp. *Other (unidentified) Reptantia Brachyura Raninidae • Ranilia sp. Calappidae *Calappa oce/lata Holthuis *Portunldae *Other (unidentified) BRACHYURA *Urochordata 596 (6%) *Ascldacea Chordata Osteichthyes MISCELLANEOUSt *Ciupeidae 548 (6%) *Other (unidentified) Organic deposits *Calcarious ooze Inorganic deposits *Silt *Clay
E. niveatus 47% of the number and 52% of the The numerical consumption of volume of prey consumed, and occurred osteichthyes was relatively uniform Figure 1. Composition of diets of C. microps (n = 96) and E. niveatus (n = 32) from continental shelf in 72% of the intestines. Cephalopods among the three size classes of snowy environments (123-256 m) in the lower Florida Keys. Numbers indicate the index of relative importance ranked second in numerical importance grouper, ranging from 43% to 65% (Table (IRI) for a particular taxon; percentages indicate the proportionate contribution of that taxon to the total (18%), and brachyuran crabs second in 5). The importance of cephalopods in· diet. *Miscellaneous = Porifera, Cnidaria, Bivalvia, Sipunculida, Priapulida, Ostracoda, Cirripedia, Stomatopoda, Anomura, Tanaidacea, lsopoda, Amphipoda, unidentified crustaceans, Bryozoa, Asteroidea volumetric importance (29%). Biogenic creased with the increasing fish size; and Echinoidea. +Miscellaneous = Cnidaria, Gastropoda, Polychaeta, Copepoda, Stomatopoda, Urochor sediment occurred in 19% of the in· numerically, they comprised 6% of the data, and unidentified crustaceans. testines. Overall, osteichthyes number of prey in the smallest fish~ 510 dominated the IRI, contributing 78% of mm TL), and 18% in both the in· the diet (Fig. 1). _ termediate size class (511-685 mm TL) https://aquila.usm.edu/goms/vol9/iss2/2 4 DOI: 10.18785/negs.0902.02 Bielsa and Labisky: Food Habits of Blueline Tilefish, Caulolatilus microps, and Snowy 84 Bielsa, L.M. and R.F .. Labisky Foods of blueline tilefish and snowy grouper 85
and the largest fish Q: 686 mm TL). Urochordates, ophiuroids, polychaetes, gests strongly that this species occupies habits. These anatomical features sug Gastropods were numerically important cnidarians, and poriferans are obligate a higher relative position in the water col gest that the snowy grouper has less of in the diet of the groupers~ 510 mm TL, benthic organisms. Brachyuran crusta umn than the blueline tilefish. The diet a demersal habit than the blueline as were brachyuran crustaceans for ceans, though capable of swimming, are of the snowy grouper was dominated by tilefish. The comparatively low frequen groupers~ 686 mm TL. The most diverse primarily benthic inhabitants. Natantian clupeid fishes, which, as pelagic cy of occurrence (19%) of biogenic sedi diet was exhibited by intermediate-sized decapods and stomatopods, though organisms, have a closer association ment in the intestines of the snowy snowy groupers. adapted for swimming, are bottom with the water column than the bottom. grouper supports the contention of dwellers, and swim only intermittently. Benthic and semi-benthic prey pelagic feeding habits. DISCUSSION Most of the gastropods (Thecosomata), (brachyuran crustaceans, urochordates, In summary, this study revealed that and calanoid copepods are pelagic, but polychaetes, natantian decapods, the blueline tilefish and snowy grouper The blueline tilefish is a generalized undergo vertical migrations that main stomatopods, and calanoid copepods) differed in their food habits- the tilefish feeder that consumes a diverse prey tain them in close proximity to the were of secondary importance in the diet being benthic and euryphagic, and the assemb~age, comprised mostly of ben bottom. of this predatory species. grouper, pelagic and relatively thic invertebrates. In contrast, the snowy The blueline tilefish has mor The presence of a large mouth, stenophagic. These divergent feeding grouper is a relatively specialized feeder, phological adaptations for benthic short and conical teeth, and a snout that strategies were attributable principally to with fish constituting the principal browsing: a terminal mouth and pointed is shorter than the jaw are adaptations differences in the anatomical adapta dietary component. snout to facilitate the extraction of of the snowy grouper to piscivorous food tions of the two species for capturing The diets of blueline tilefish and organisms from crevices in the irregular snowy grouper suggest that these substrate; upper and lower jaws with Table 4. Percentage numerical occurrence of foods, by major taxa, found in the intestines of four size classes of C. microps from continental shelf environments (123-256 m) in the lower Florida Keys. predatory species occupy different single rows of moderately large canines; realized niches. This niche differentiation and a medial patch of 4-5 rows of Numerical Occurrence(%) is probably founded in the different villiform teeth to facilitate grabbing, tear s 500 mm TL 501-600 mm TL 601-700 mm TL ~ 701 mm TL anatomical adaptation of their mouth ing and/or scraping benthic organisms Food taxa (n - 16) (n = 43) ( n= 19) (n = 14) parts for capturing prey, which, subse from the 'substrate (Ross 1978). These quently, results in their spatial segrega anatomical features likely explain the Gastropoda 20.3 24.1 3.4 22.4 high frequency of occurrence of biogenic Cephalopoda 0.3 0.8 0.7 1.4 tion in the water column. Polychaeta 5.7 5.9 1.6 2.0 In terms of space, the blueline sediment (58%) in the intestines of the Copepoda 1.2 21.6 54.3 0.7 tilefish, as evidenced by its diet, its tilefish. Natantia 12.6 11.8 23.3 18.6 The diet of the snowy grouper sug- Brachyura 6.0 2.8 3.0 4.5 closely associated with the bottom. Ophiuroidea 38.5 18.6 1.8 32.8 Table 3. Percentage numerical occurrence (N), volumetric occurrence (V) and frequency of occurrence Urochordata 1.7 2.0 5.1 2.9 (F) of foods, by major taxa, found in the intestine of C. microps (N = 96) and E. niveatus (N = 32) from Osteichthyes 1.7 3.7 0.7 2.5 continental shelf environments (1223-256m) in the lower Florida keys. Miscellaneous 12.0 8.7 6.1 12.2
C. microps E. niveatus Table 5. Percentage numerical occurrence of foods, by major taxa, found in the intestines of three size classes of E. niveatus from continental shelf environments (123-256 mm) in the lower Florida Keys. Food taxa N v F N v F Numerical Occurrence (%) Gastropoda 19.0 0.6 40.6 5.3 1.0 3.1 s 510 mm TL 511-685 mm TL ~ 686 mm TL Cephalopoda 0.8 12.2 18.8 18.4 7.6 28.1 Polychaeta 4.2 6.0 54.2 3.9 0.4 9.4 Food taxa (n = 6) (n = 17) (n = 7) Copepoda 21.2 0.4 12.5 1.3 0.1 3.1 12.5 Natantia 15.4 8.6 61.5 6.6 6.4 Gastropoda 23.5 0 18.2 Brachyura 3.9 2.4 39.6 9.2 29.0 15.6 Cephalopoda 5.9 17.5 18.2 Ophluroidea 20.2 14.8 38.5 0 0 0 Polychaeta 5.9 5.0 0 Urochordata 2.9 40.3 35.4 2.6 1.9 6.3 Copepoda 0 2.5 0 Osteichthyes 2.4 12.9 37.5 47.4 51.7 71.9 Natantia 0 12.5 0 M iscellaneous• 10.0 1.8 60.4 5.3 1.9 12.5 Brachyura 0 10.0 27.3 Total 100.0 100.0 100.0 100.0 Ophiuroidea 0 0 0 Urochordata 0 5.0 0 •c. mlcrops: Porifera, Cnidaria, Bivalvia, Sipunculida, Priapulida, Ostracoda, Cirripedia, Sto~atopoda, Osteichthyes 64.7 42.5 54.5 Anomura Tanaidacea, lsopoda, Amphipoda, unidentified crustaceans, Bryozoa, Asteroidea, and Miscellaneous 0 5.0 0 Echinoid~a. E. niveatus: Cnidaria, Stomatopoda, and unidentified crustaceans. Published by The Aquila Digital Community, 1987 5 Gulf of Mexico Science, Vol. 9 [1987], No. 2, Art. 2 86 Bielsa, L.M. and R.F. Labisky Foods of blueline tilefish and snowy grouper 87 prey, which, in turn, spatially stratified LITERATURE CITED Oceanogr. Studies 1. the predators on the basis of prey Pinkas, L., M.S. Oliphant, and I.L.K. Iver availability. Thus, the blueline tilefish Abbott, R.T. 1974. American seashells: son. 1971. Food habits of albacore, and the snowy grouper, although in the marine mollusca of the Atlantic bluefin tina, and bonito in California habiting tne same continental shelf and Pacific coasts of North America. waters. Calif. Fish Game Fish. Bull. biotype, occupy different trophic niches, 2nd edition. Van Nostrand Reinhold 152:1-105. which tends to reduce interspecific com Co., New York, N.Y. 663 p. Rathbun, M.J. 1898. The Brachyura of the petition for food resources, and thereby, Barnes, R.D. 1980. Invertebrate zoology. biological expeditions of the Florida allows coexistence of the two predatory 4th edition. Saunders College/Holt, Keys and the Bahamas in 1893. Iowa fish species. Rinehart and Winston, Philadelphia, State University Bull. Lab. Nat. Hist. Pa. 1089 p. 4:250-294, 9 pis. ACKNOWLEDGMENTS Benedict, J.E. 1900. The anomuran col _____ 1925. The spider crabs of lections made by the Fish Hawk ex America. U.S. Natl. Mus. Bull. 129. 613 Acknowledgment is due to the pedition to Porto Rico. Bull. U.S. Fish p., 283 pis. following taxonomic specialists who Comm. 20:129-148, 4 pis. Ross, J.L. 1978. Life history aspects of assisted in the identification of in Bielsa, L.M. 1982. Food-web community the gray tilefish Cau/olatilus microps vertebrates: D. L. Pawson and T. Coffin, of two deep-water reef fish, (Goode and Bean, 1878). M.A. thesis, Smithsonian Institution (echinoderms); Caulolatilus microps Goode and Bean College of William and Mary, F. J. Maturo, Jr~, University of Florida 1978, and Epinephelus niveatus (Valen Williamsburg, Va. 120 p. (crustaceans and echinoderms); W. G. ciennes, 1928), in the Lower Florida ____ . 1982. Feeding habits of the Lyons and D. K. Ca!llp, Florida Depart Keys. M.S. thesis, University of Florida, gray tilefish, Caufolatilus microps ment of Natural Resources (DNR) Gainesville. 34 p. (Goode and Bean, 1878) from North (crustaceans); J. F. Quinn, Jr., DNR Dooley, J: