Subtropical-Tropical Seagrass Communities of the Southeastern United States: Fishes and Fish Communities
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Subtropical-Tropical Seagrass Communities of the Southeastern United States: Fishes and Fish Communities R Grant Gilmore Division of Marine Sciences Harbor Branch Oceanographic Institution, Inc. 5600 Old Dixie Highway Fort Pierce, Florida 33450 ABSTRACT Prior to 1960, most ichthyofaunalresearch was necessarilytaxonomic and zoogeographic,with little attentiongiven to habitator substrateassociations. With the adventof long-termfaunal studies within specific habitats and analyses of physical and biological parameters affecting fish distribution, seagrasseswere recognized as a distinct fish habitat. Regionalichthyological research in seagrassecosystems has been conducted primarily in the northeastern Gulf of Mexicoand principallyin the ApalacheeBay region.Consequently, regional tropical and subtropical seagrassichthyofaunas have received little study. The availableliterature on tropical and subtropicalfish- seagrassassociations is not adequatefor quantitativeassessment, but it revealszoogeographic distribution patterns and enablessome prediction of speciesoccurrence in seagrassecosysterns. Fisheryspecies have received the mostintense study, particularly certain sciaenids and sparids,such as the spottedseatrout, Cynoscion nebulosus, and the pinfish,Lagodon rhornboides. However, many species need further treatment as their microhabitat associations,general biology, behavior, and mortality rates during juvenile developmentalperiods have not receivedadequate attentioIL Typically diminutiveand numerically abundantnonfishery species,such as gobiids and syngnathids,make up the majority of resident specieswithin the seagrassecosystem. Their biology and impact on this ecosystemawait further study. The inter- and intraspecific interactions of various seagrassresidents and systematically occurring transients need to be researched,particularly with regard to predatory relationships, territorial behavior, invertebratepopulation dynamics and distribution,seagrass morphology, and meadowhomogeneity. The hierarchial predatory relationships between various fish species guilds throughout the total ecosystem, particularly with regard to tertiary and upper level predators,have beenvirtually ignored. INTRODUCTION systematic work from researchers attempting to discern the species comprising various populations and communities encountered in seagrass systems. Early ichthyofaunal studies in the southeastern Therefore, much of the historical emphasis in United States rarely considered distinct habitat ichthyological studies has necessarily been placed associations with regard to seagrass meadows on taxonomy and zoogeography rather than habitat Boschung, 1957; Briggs, 1958; Fowler, 1945; Gunter, 1945; Longley and Hildebrand, 1941!. associations. These studies occurred at a time when compre- Reid 954! published the first work to recog- hensive and detailed systematic, morphological, nize a distinct seagrass-ichthyofaunal association embryological, and zoogeographical studies occupied within a subtropical latitude in the southeastern most ichthyologists. Even more recent comprehen- United States. Reid recognized the value of the sive ichthyofaunal studies scarcely mention the seagrass habitat to marine and estuarine fishes and seagrass meadow as an integral habitat with an was among the first in the Piedmont coastal region associated fish community Bohlke and Chaplin, to try to numerically define fish associations with 1968; Hoese and Moore, 1977!. The rich south- seagrasses as a fish habitat, His major objective was eastern ichthyofauna has required considerable to determine the composition of fish communities in 118 FLORIDA lVIARINE RESEARCH PUBLICATIONS the vicinity of Cedar Key, Florida, their local habitat researchersstudying seagrassfish, macrophyte, and distribution, and the relative abundanceof species invertebrate populations Darcy, 1985; Stoner, in the habitats. A secondary objective was to 1979b, 1980a!. determine some of the basic environmental, physical, and biologicalfactors that causedpopulation changes in the various species studied. Ever since Reid's comprehensivework, these same objectives have SEAGRASS ICHTHYOLOGICAL RESEARCH been soughtby many workers in this region of North SINCE ISBO America e.g., Baird et aL, 1971, 1972; Gilmore et aL, 1976; Jones et aL, 1975; Livingston, 1975, The progressionof ichthyologicalresearch 1982b, 1984a; Schmidt, 1979, U,S. Dept. of Interior, during the past 250 years has followed a systematic National Park Service, Everglades National Park patternclosely resembling the evolutionof research Research Station, personalcommunication; Springer activities and interests in other phyla. Early studies, and Woodburn, 1960!. What is most remarkable from Catesby'sNatural History of Carolina, Florida about this early work is that no regional systematic and the Bahama Islands, published 1731-1743, to study of the distributionof fishesin varioushabitats, Fowler's Fishes of the Southern Piedmont and including seagrass meadows, was previously con- Coastal Plain 945!, concentrated on species des- ducted. Gunter 945! had conducteda similar study criptionsand zoogeography.Greater interest has of the Copano and Aransas Bay systemsalong the characteristically been given to fishery species. Texas coast, but failed to mention seagrass meadows Since the mid-nineteenth century, fishery species as a significant ichthyofaunal habitat. This was in have received more detailed biological and life spite of the wide distribution of seagrassesaround history treatment than other species, including the Gulf of Mexico and along the east coast of study of habitat associations,trophic habits, and Florida. In the literature, one can find earlier recog- population dynamics relative to various environ- nition of the habitat value of seagrasses,but the mental parameters. Taxonomic and zoogeographic acknowledgement is generally purely incidentaL studies in warm-temperateestuarine regions reached Hildebrand and Cable 938! stated that the primary a peak during the latter half of the 19th century, but nursery habitat in inshore waters for the pinfish, are still continuing in tropical regions. Life history Lagodonrhomboides, was "...eelgrassor other bottom studies of fishery species have continued in both growth, a habitat also occupied by their relatives, regions,and our present knowledgeof these species the young sheepshead."Thus, recognitionthat sea- fai surpassesthat of the multitude of nonfishery grassesplayed a rote in the developmentalphase of species Cato and McCullough, 1976; Darcy, 1985; a number of regional estuarine species came within Gilmore et aL, 1983b; Mercer, 1984a, 1984b; the last 50 to 60 years, However, research strictly Nickerson, 1984; Overstreet, 1983a, b; Starck and on fishesinhabiting seagrass meadows and the nature Schroeder, 1970; Tashiro, 1979!, These recent of their associationwith seagrasseswas not con- studies are major review papers for gray snapper, ducted seriously until after Reid 954!, and prin- striped and white inullet, pinfish, snook, red drum, cipally after 1960. and spotted seatrout, constituting228 publications Caldwell 957! published a detailed biological specifically on these species, 193 published since and systematicstudy of the most ubiquitous 1960, Eighty-six percent of these papers are on seasonal seagrass resident in the southeastern warm- temperate species. United States, the pinfish, Lagodon rhomboides. Detailed biological study of certain regional This work was significant for at least two reasons, nonfishery specieshas occurred during the past 37 First, the pinfish was not necessarilya commercial years, with increased interest in warm-temperate or sport fishery species of significance,and, there- and tropical speciesassociated with seagrasshabitats fore, this comprehensivebiological treatment was within estuariesor adjacent to coral reef formations soinewhat innovative. Caldwell's study came during e.g., Caldwell, 1957; Clemente and Livingston, a period in which study of the naturat history and 1983, 1984; Dawson, 1966, 1969; Joseph, 1957; biology of fishes of tittle or no fishery value was Kaill, 1967; Randall, 1961, 1963, 1965, 1967; uncommon. Second, the overwhelining seasonal Randall and Randall, 1963; Springer and McErlean, abundance of this species in seagrass beds is now 1962; Starck and Davis, 1966; Stoner, 1979 b; thought to have a major impact on the remainder of Stoner and Livingston, 1980, 1984; Strawn, 1958!. the seagrasscommunity. Subsequently,the pinfish The number of detailed quantitative studies of has become a species of major importance to entire fish communities to include analyses of south- NUMBER 42 eastern seagrass habitats actually surpasses that of Young et al., 1976!. However, the effect of top individual species biology works to date Table 1; predators e.g,, piscivorous fishes! on fishes in Figure 1!. Much of this research, particularly during seagrass ecosystems has not received modern treat- the 1970's, resulted from the great emphasis on ment Larger predators may have a significant effect anthropogenic impacts on inarine ecosystems. How- on the population structure of smaller, lower trophic ever, long-term studies of the effects of environ- level fishes in seagrass habitats, as was recently mental parameters on fish populations inhabiting demonstrated by Holt et aL 983!. This higher subtropical or warm-temperate seagrass meadows level predation may, in turn, affect the benthos and have been conducted only during the past decade or epifauna so heavily studied in