2% - p.*' + 0.:%: 4.' 1%* B -944 3 =5. M.: - . * 18 . .,:i -/- JL J-1.4:7 - of the FLORIDA STATE MUSEUM Biological Sciences Volume 24 1979 Number 1 THE ORIGIN AND SEASONALITY OF THE FISH FAUNA ON A NEW JETTY IN THE NORTHEASTERN GULF OF MEXICO ROBERT W. HASTINGS *S 0 4 - ' In/ g. .f, i»-ly -.Id UNIVERSITY OF FLORIDA - GAINESVILLE Numbers of the Bulletin of the Florida State Museum, Biological Sciences, are pub- lished at irregular intervals. Volumes contain about 300 pages and are not necessarily completed in any one calendar year. John William Hardy, Editor Rhoda J. Rybak, Managing Editor Consultants for this issue: Robert L. Shipp Donald P. deSylva Communications concerning purchase or exchange of the publications and all manuscripts should be addressed to: Managing Editor, Bulletin; Florida State Museum; University of Florida; Gainesville, Florida 32611. Copyright © 1979 by the Florida State Museum of the University of Florida. This public document was promulgated at an annual cost of $3,589.40, or $3.589 per copy. It makes available to libraries, scholars, and all interested persons the results of researches in the natural sciences, emphasizing the circum-Caribbean region. Publication date: November 12, 1979 Price, $3.60 THE ORIGIN AND SEASONALITY OF THE FISH FAUNA ON A NEW JETTY IN THE NORTHEASTERN GULF OF MEXICO ROBERT W. HASTINGS1 SYNOPSIS: The establishment of the fish fauna on a new jetty at East Pass at the mouth of Choctawhatchee Bay, Okaloosa County, Florida, was studied from June, 1968, to January, 1971. Important components of the jetty fauna during its initial stages of development were: (a) original residents that exhibit some attraction to reef habitats, including some sand-beach inhabitants, several pelagic species, and a few ubiquitous estuarine species; and (b) reef fishes originating from permanent populations on offshore reefs. The jetties provided artificial reef-like habitat for these species and furnished shelter and food sources on a sandy beach where such habitats were normally absent. Continued recruit- ment of species to the jetties consisted of (a) occasional strays from other habitats in the area, and (b) stragglers from more tropical areas carried into the northern gulf by currents. Reef fishes of the northern Gulf of Mexico can be divided into three groups based upon their occurrence: (1) common species on the offshore reefs in the northern gulf that frequently form summer populations in shallow coastal reef habitats; (2) species also common on the offshore reefs but apparently restricted to depths greater than about 18 m and consequently not colonizing artificial reef habitats in shallow water; and (3) typical coral reef species occurring in the northern gulf as stragglers, being carried into the area by currents (by the Eastern Gulf Loop Current from the Caribbean Sea). The only obvious successional change was the continued yearly increase in the number of species on the jetties. Average counts of species numbers from July through October were 28 in 1968, 35 in 1969, and 39 in 1970. This annual increase prevailed even though most species were absent from December through March. Seasonal changes in the fish fauna at the jetties were pronounced. The major autumn decline in the number of species inshore occurred in November at about 20°C. Only 5 to 10 species were usually counted during winter. The annual increase in species numbers began during February or March at about 15 to 20'C. A total of 204 species was recorded at the East Pass and St. Andrew jetties (a similar but older habitat 80 km to the east). At least 150 species were common to both habitats. In spite of minor differences observed between the two areas, the fish fauna of the East Pass jetties has apparently reached its peak in diversity and is similar to that of the St. Andrew jetties. 1The author is an Associate Professor of Biology at Rutgers University, Camden, New Jersey. The publication costs were subsidized in part by a grant from the Sport Fishing Institute, Washington, D.C. HASTINGS, ROBERT W. 1979. The Origin and Seasonality of the Fish Fauna on a New Jetty in the Northeastern Gulf of Mexico. Bull. Florida State Mus., Biol. Sci. Vol. 24(1):1-122. I. 2 BULLETIN FLORIDA STATE MUSEUM Vol. 24, No. 1 TABLE OF CONTENTS INTRODUCTION. 5 ACKNOWLEDGEMENTS. MATERIALS AND METHODS ......... ........... .. 5 DESCRIPTION oF STUDY AREA ....... ....,.., 19 SYSTEMATIC ACCOUNTS . .. ....., 27 DISCUSSION. .. 78 ORIGIN OF THE JETrY FISH FAUNA ..... 78 SUCCESSIONAL CHANGES IN THE FISH FAUNA ... ... 83 SEASONAL CHANGES IN THE FISH FAUNA . .. ... 86 EFFECTS OF CHEMICAL AND PHYSICAL FACTORS . ... 90 TROPHIC STRUCTURE OF THE FISH FAUNA . 91 COMPARISON OF EAST PASS AND ST. ANDREW JETIES , 93 COMPARISON OF THE JETTIES AND OFFSHORE REEFS 95 RECOMMENDATONS 97 LITERATURE CITED . 98 106 APPENDIX . INTRODUCTION Coral reefs support a tremendous diversity of fishes. Some reef species have rather narrow niche requirements that restrict them to living coral reefs. However, many may occupy such habitats because of the rich food supply usually associated with coral reefs, bacause of the numerous holes and crevices that provide shelter, or in some cases, because of an attraction to solid aobjects in open marine en- vironments. Consequently, any reef-like stfucture that breaks the monotony of open, flat bottoms of pelagic surface waters tends to at- tract numerous species. Such associations are observed even in temperate and subtropical waters where coral reefs are absent. Reef-building corals cannot survive temperatures less than about 18°C and are consequently excluded from inshore areas of the north- ern Gulf of Mexico where winter temperatures fall considerably below this level (Smith 1954; Lynch 1954). Natural rocky substrates (other than estuarine oyster reefs) are also rare in coastal areas of the northern gulf at depths less than about 12 m, so that natural habitat suitable for reef species is generally unavailable. However, numerous artificial structures, such as shipwrecks, pil- ings, and rock piles, have enabled some typical reef fishes to become established in shallow waters of the northern gulf, and some species once considered rare are now commonly collected. Artificial habitats such as the jetties at Port Aransas, Texas, and St. Andrew Bay, Florida, are important for such new inhabitants (Baughman 1947, 1950a and b; Gunter and Knapp 1951; Caldwell and Briggs 1957; 1979 HASTINGS: NORTHEASTERN GULF FISH FAUNA 3 3- FIGURE 1.-East Pass at mouth of Choctawhatchee Bay, Okaloosa County, Florida. A. View to southeast prior to construction of jetties. B. View to northwest after construction of jetties. - 4 BULLETIN FLORIDA STATE MUSEUM Vol. 24, No. 1 Hoese 1958; Caldwell 1959; Allison 1961; Briggs et al. 1964). Addi- tional records of such fishes in the northern gulf are given by Collins and Smith (1959), Dawson (1962), Caldwell (1963), Haburay et aL (1969), Haburay et al. (1974), and Moore (1975). Man has recently begun to build artificial habitats specifically to improve angling, and a new technology of artificial reefs has evolved. References on artificial reefs (Carlisle et aL 1964; Stroud and Massman 1966; Unger 1966; Woodburn 1966; Oren 1968; Anon 1969; Turner et aL 1969; Rickards 1973; Steimle and Stone 1973; Colunga and Stone 1974) include bibliographies on the subject. Although successful studies have been made on the development of artificial reef faunas in the Virgin Islands (Randall 1963) and off the coast of California (Car- lisle et aL 1964; Turner et aL 1969), detailed information is unavailable for the northern Gulf of Mexico. An opportunity to examine the effects of an artificial reef in a northern gulf locality was presented with the construction of a jetty at East Pass, Choctawhatchee Bay, at Destin, Florida (Fig. 1). The in- vestigation was begun in June, 1968, shortly after construction on the jetties had begun, and the development of the fish fauna on this reef system was followed, almost from the start. Profound seasonal changes in inshore fish populations of the north- ern gulf over-shadowed the more subtle successional changes in the developing jetty fauna. Thus, emphasis is placed on these seasonal changes, as well as on successional changes in the reef fish popula- tions. Potential sources of reef fishes to habitats such as the jetties have also been analyzed. Many obligate reef species have pelagic eggs or lar- val stages dispersed widely by ocean currents and depend on availability of reef habitats for survival. Thus stragglers from other reef habitats often occur on artificial reefs. Two reasons have been sug- gested for the frequent occurrence of reef fishes in inshore areas of the northern gulf. Caldwell (1959, 1963), Dawson (1962, 1963, 1970, 1971, 1972), and Haburay et aL (1969) believed that most were strays from tropical areas and were carried into the northern gulf from the Carib- bean. The Eastern Gulf Loop Current seasonally intrudes far into the northern gulf (Leipper 1970) and must carry large numbers of pelagic eggs and larvae into this area. In contrast, Caldwell(1963), Hildebrand et aL (1964), and Sonnier et aL (1976) emphasized that many species of supposedly "tropical" fishes were permanent residents on the sub- tropical natural reefs offshore in the northern gulf, and that the in- habitants of the inshore artificial reefs could represent strays from these offshore populations, rather than strays from areas such as the Caribbean. The seasonal occurrence patterns of reef fishes at the -- 1979 HASTINGS: NORTHEASTERN GULF FISH FAUNA 5 jetties have been used in this study to speculate on the probable origins of many of these species. ACKNOWLEDGEMENTS Thanks are extended to my fellow graduate students at Florida State University, Stephen A. Bortone, Lawrence E. Sacks, Stephen L. Smith, Camm C. Swift, and F. William Vockell, who often assisted during field trips.