The Origin and Seasonality of the Fish Fauna on a New Jetty in Northeastern Gulf of Mexico

Abstract

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 recruitment 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.