Shrimp are merobenthic and migrate from bays and estuaries to open Gulf waters at different stages of development in different seasons. The white shrimp for example, reaches its offshore peak in April, May and June and its bay peak in the months of September, October

and November.

Each of these species has a sediment preference.

mud, the white sandy mud, and the pink shell sand.

The brown prefers

Additional

differences occur in their behavior. The brown shrimp are nocturnal, burying in the softer muds during the day, whereas the white shrimp are diurnal and bury themselves at night.

that are

In addition to the benthic invertebrates, there are some species of fish nektonic but are closely related to the bottom communities. These species are referred to as demersal. Among the more abundant species are the longspine porgy, Atlantic croaker, inshore lizardfish, silver seatrout, and sand seatrout, and wenchman.

Snapper and

groupers, demersal carnivores and valuable food fish, school near topographic irregularities, normally at the bases of banks (or rises), but also around ledges, stillstands, and other irregular bottom conditions. Bottom topography of the Louisiana and eastern Texas OCS is ideally suited as snapper and grouper habitats, and has been fished since at least the turn of the century. While gear improvements have been made, the standard method of catching these fish is deep hook and line fishing, in 25-100 fathoms. (See section IV.E. for locations of snapper-grouper banks.)

According to Pequegnat, et al. (1972) the Outer Continental Shelf

edge and the upper slope benthic populations in the northwest Gulf are larger than previously thought, based on dredge hauls and photographs.

Numerous holothurians, starfish, brittle stars and crustaceans can be seen in bottom photographs and brought to the

surface in benthic trawls. Much of the surface sediment is strewn with fecal pellets, trails and burrows.

Several benthic species may have commercial potential in the future. Royal-red shrimp (Hymenopenaus robustus), already being harvested to some extent in the Gulf, are found in the depth range of 180 to 820 meters.

The giant red crab (Geryon quinquedens), although more abundant in the deeper waters has been recovered in depths as shallow as 275 meters. This same sort of pattern is true of the giant isopod crustacean (Bathynonius giganteus). Populations of tilefish (Lopholatilus chameleonticeps) are found in depths around 300 meters, and like the aforementioned crab and isopod, have not become commercially important yet. As more becomes known of their habitats and life cycles, however, they may be of considerable commercial value. 1/

1/ Much of the information in these paragraphs is taken from the testimony of Dr. Willis E. Pequegnat at the OCS Public Hearing on the Proposed Offshore Louisiana Oil and Gas Lease Sale, November, 1973.

Individuals of this group commonly, but not always,

range over broad areas, and in doing so, participate in several

biotic communities.

Examples are the semicatadromous fish such

as the menhaden which are pelagic plankton larvae, estuarine juveniles, and pelagic adults. Other examples are the sharks which may cruise over broad areas of the ocean, the shore and the bays searching for prey. Nevertheless, most nekton are limited in range by the same environmental conditions of temperature, salinity, available food materials, and type of bottom as are organisms which are less mobile.

Near the surf zone, over sand bottoms and grass beds live the sea robins (Triglidae), gobies (Gobiidae), midshipman (Batrachoididae), sea catfish (Arridae), pipefish (Syngnathidae), and jacks and pompano (Carangidae).

From a few feet below low tide level nearly to the outer limits of the continental shelf are populations of spot, croakers, seatrout or weakfish (Sciaenidae), rays (Rajidae, Dasyatidae), hake (Gadidae), rabbit fish and puffer fish (Tetraodontidae), and the families of sole and flounders (Soleidae and Bothidae) including the commercial southern flounder, gulf flounder, little flounder, ocellated flounder, whiffs, fringed flounder, hog chokers, blacklined naked sole, and tongue sole.

The most important neritic nektonic in the Gulf are the herring

like fishes such as the menhaden (Clupeidae) and the anchovies (Engraulidae).

These make up the larger part of the secondary

food chain and are preyed upon by a great variety and number of other fish. Some other common or abundant nektonic fish include the sharks (Carcharhinidae, Sphyrnidae), snapper (Lutjanidae), groupers and sea basses (Serranidae), spanish mackerel (Scombridae), jacks (Carangidae), sailfish and marlin (Istiophoridae), swordfish (Xiphiidae), spanish mackerel (Scombridae), tilefish (Branchiostegidae) and tuna (Scombridae). Common non-fish nekton include the squid

(Loliginidae), and bottlenose dolphins (Delphinidae).

The demersal organisms were discussed in the previous section on

the benthic biota but may be considered in the nekton also.

5. UNIQUE ENVIRONMENTS

FLOWER GARDEN BANKS 1/

Description

The Flower Garden Banks are two topographic

highs on the Texas OCS approximately 110 miles SSE of Galveston, Texas (Fig. 25). The larger structure, West Flower Garden Bank, is located at approximately 93°49.0'W longitude and 27°52.6'N latitude, and the smaller structure, East Flower Garden Bank, is about eight miles ENE of the former. They were first identified in survey work by Coast and Geodetic Survey in 1936 (Shepard, 1937). Stetson (1953) suggested that the banks were capped by coral reefs, and Pulley (1963) reported these reefs to be live and flourishing.

The Flower Garden Banks are members of a series of pinnacles that rise abruptly from the smooth, sediment covered Outer Continental Shelf and slope off Texas and Louisiana (Fig. 26). The origin of many of these pinnacles, and the Flower Gardens specifically, is the result of piercement salt domes, salt plugs which have thrust upward and warped and folded the overlying rock strata (Edwards, 1971). The West Flower Garden structure (Fig. 27) at the edge where it rises from the seafloor, is approximately 7 miles long by 5 miles wide, trending northeast to

southwest.

Relief is about 300 feet, with water depth at the northern edge of the bank (landward) around 360 feet, and 450 feet at the southern (seaward) edge. The uppermost point on the bank is 60-65

1/ Taken from Edwards (1971), Bright and Pequegnat (1973, in press) and testimony of Dr. Bright, Texas A & M University, at OCS Public Hearing in Houston, Texas on February 21, 1973.