OCS Study 

MMS 2003-072 

 

Selected Aspects of the Ecology of the 

Continental Slope Fauna of the Gulf of 

Mexico: A Synopsis of the Northern 

Gulf of Mexico Continental Slope Study, 

1983-1988 

U.S. Department of the Interior

Minerals Management Service 

Gulf of Mexico OCS Region 
U.S. Department of the Interior

Minerals Management Service 

Gulf of Mexico OCS Region 

OCS Study 

MMS 2003-072 

Selected Aspects of the Ecology of the 

Continental Slope Fauna of the Gulf of 

Mexico: A Synopsis of the Northern 

Gulf of Mexico Continental Slope Study, 

1983-1988 

Authors 

Benny J. Gallaway 

John G. Cole 

Robert G. Fechhelm 

Prepared under MMS Purchase Order 17037 

by 

LGL Ecological Research Associates, Inc. 

1410 Cavitt Street 

Bryan, Texas 77801 

Published by 

New Orleans

November 2003 
iii

DISCLAIMER

This report was prepared under a purchase order from the Minerals Management Service 

(MMS) to LGL Ecological Research Associates, Inc. This report has been technically 

reviewed by the MMS and approved for publication. Approval does not signify that 

contents necessarily reflect the views and policies of the Service, nor does mention of 

trade names or commercial products constitute endorsement or recommendation for use. 

It is, however, exempt from review and compliance with MMS editorial standards.

REPORT AVAILABILITY

Extra copies of this report may be obtained from the Public Information Office (Mail 

Stop 5034) at the following address:

U.S. Department of the Interior

Minerals Management Service

Gulf of Mexico OCS Region

Public Information Office (MS 5034)

1201 Elmwood Park Boulevard

New Orleans, Louisiana 70123-2394

Telephone: (504) 736-2519 or

1-800-200-GULF

CITATION

Suggested citation:

Gallaway, B.J., J.G. Cole, and R.G. Fechhelm. 2003. Selected aspects of the ecology of 

the continental slope fauna of the Gulf of Mexico: A synopsis of the Northern Gulf of 

Mexico Continental Slope Study, 1983-1988. U.S. Department of the Interior,

Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA. 

OCS Study MMS 2003-072. 44 pp.
v

TABLE OF CONTENTS

Page

LIST OF FIGURES......................................................................... vii

LIST OF TABLES.......................................................................... ix

ABSTRACT................................................................................... xi

INTRODUCTION............................................................................ 1

APPROACH AND METHODS............................................................ 2

Analytical Design......................................................................... 3

Field Methods............................................................................. 6

Hydrographic Measurements....................................................... 6

Box Core Sampling (Meiofaunal/Macrofauna).................................. 6

Trawl Sampling (Megafauna)...................................................... 8

Benthic Photography (Megafauna)................................................ 8

Laboratory Methods...................................................................... 10

Statistical Methods........................................................................ 10

ENVIRONMENTAL CHARACTERIZATION.......................................... 12

BIOLOGICAL CHARACTERIZATION................................................. 14

Meiofauna................................................................................. 14

Macrofauna................................................................................ 18

Megafauna................................................................................. 23

Abundance and Diversity............................................................ 26

Life History Data..................................................................... 29

CONCLUSIONS.............................................................................. 34

LITERATURE CITED....................................................................... 35

APPENDIX 1: SUMMARY OF TRAWLING EFFORT................................ 39
vii

LIST OF FIGURES

Figure Page

1 Sample sites in the Gulf of Mexico............................................... 4

2 Box core and configuration of in situ subsampling tubes in the box corer.. 7

3 Schematic diagram of photographic system used for benthic 

Photography........................................................................ 9

4 Taxonomic experts involved in faunal identifications for the NGOMCS 

Study................................................................................. 11

5 Relative occurrence of meiofauna and macrofauna with depth at all 

sampling stations in terms of density and approximate biomass............. 17

6 Macrofauna density by depth...................................................... 20

7 Comparative density by depth of macrofauna for the Atlantic and Gulf of 

Mexico NGOMCS study sites.................................................... 24

8 Number of expected species of macrofauna given the number of 

individuals in a sample for three depth strata in the North and MidAtlantic and the Gulf of Mexico.................................................. 25

9 Megafaunal density by depth interval for the northern Gulf of Mexico 

based upon trawls................................................................... 27

10 Megafaunal density by depth interval for the northern Gulf of Mexico 

based upon photographic observations and trawls.............................. 28

11 Comparison of fish diversity levels, by depth, between the Gulf of 

Mexico and the Atlantic continental slopes..................................... 31

12 Results of rarefaction analyses for megafaunal fish and invertebrate data 

by depth.............................................................................. 32
ix

LIST OF TABLES

Table Page

1 Distribution of total area sampled by gear type and depth interval.......... 15

2 Relative abundance of major macrofaunal groups.............................. 19

3 Density of the 13 polychaetes that comprised as much as 2% of the total 

macrofaunal collection............................................................. 22

4 Densities of abundant decapod crustaceans and fish by depth as reflected 

by the trawl collections of the NGOMCS Study............................... 30
xi

ABSTRACT

The Minerals Management Service (MMS) funded a Northern Gulf of Mexico 

Continental Slope (NGOMCS) study which was conducted over the period 1983-1998. 

The studies were completed and a review of selected aspects were published in the peerreviewed literature (Pequegnat et al. 1990). A new continental slope study was funded by 

MMS in the late 1990’s. It was subsequently learned that large portions of the historical 

database had been lost or corrupted. In this study, we have 1) reconstructed and updated 

the database to include corrections to the data tha t were made after the contract was 

completed; 2) conducted new analyses to test the zonation hypothesis proposed in the 

original study; and 3) prepared a summary of the overall findings. We conclude that the 

Gulf continental slope appears to differ from the slope fauna of the U.S. Atlantic region 

in several fundamental ways and that the general pattern of faunal change on the upper 

slope is that of a non-repeating sequence of species arrayed along the depth gradient 

rather than three distinct and homogeneous megafaunal assemblages.
1

INTRODUCTION

By the late 1970s, the continental shelf of the northwestern Gulf of Mexico had 

become the most intensely developed offshore oil and gas region in the world. Further, 

new technology was envisioned that would allow movement of oil and gas exploration 

off the shelf down the continental slope (200-3,000 m in depth). Given this potential 

expansion of development, the federal agency responsible for regulating offshore oil and 

gas development (U.S. Department of Interior’s Minerals Management Service, MMS) 

commissioned a synthesis of available environmental and biological information about 

the continental slope region of the Gulf of Mexico. The results of that study (Pequegnat 

1983) characterized the continental slope of the northern Gulf as having five distinctive 

faunal zones, arranged in broad, depth-delimited bands around the perimeter of the slope. 

The fauna was generally considered, however, to be poorly known and new studies were 

proposed as being necessary to evaluate the impacts of oil and gas development in this 

region.

In response to this recommendation, MMS funded the Northern Gulf of Mexico 

Continental Slope (NGOMCS) Study which was conducted over the period 1983 to 1988 

(Gallaway et al. 1988a; Gallaway 1988a, 1988b, 1988c). The focus of the study centered 

on testing the hypothesized depth-biological zonation concept, i.e., sampling stations 

were not evenly spaced down the slope, but were the approximate mid-point of the 

previously defined biological zones or faunal assemblages. Biota were sampled using 

box cores (meiofauna, macrofauna), trawls (megafauna), and a benthic camera system 

(megafauna). Abundance was compared among geographic regions, seasons, and along 

isobaths as well as by depth. The relationships of faunal abundance to sediment type, 

sediment and water quality, and hydrocarbon content and type of hydrocarbon were also 

evaluated. While the study design supported the use of only four basic ANOVA’s, there 

were many species and physical variables to be evaluated. The basic macrofauna

correlation matrix was 83 x 83 variables yielding nearly 7,000 correlations. Analysis of 

the 61 species of abundant macrofauna yielded 244 ANOVA analyses, each with a 

corresponding set of orthogonal contrasts addressing questions of interest. The findings 

were presented and discussed in some 2,000 plus pages of the final reports produced for 

MMS in 1988 as cited above. These gray-literature reports were not widely circulated.

The specimens of meiofauna, macrofauna, and megafaunal invertebrates collected 

by the NGOMCS Study were transported to the U.S. Museum of Natural History for 

archival, whereas the fish were deposited at the Texas Cooperative Wildlife Collection, 

Texas A&M University. Some 48,000 benthic photographs taken during the study were 

submitted to MMS at the Gulf of Mexico Regional Office in New Orleans, Louisiana. 

The verified data files collected by the NGOMCS Study were submitted to the National 

Oceans Data Center (NODC) for archival.

A review of the selected aspects of the NGOMCS Study was published by

Pequegnat et al. (1990). The scope of this review was comprehensive, providing

overviews of the environment, the meiofauna, the macrofauna, the megafauna, and what 

was known at the time regarding chemosynthetic seep communities. The overview
2

focused on the apparent confirmation of the zonation scheme that had been previously 

postulated by Pequegnat (1983). The five faunal zones proposed by Pequegnat (1983) 

had been challenged by Carney et al. (1983). These authors had opined that faunal 

assemblages change continually with depth such that a distinct upper slope or shelf fauna 

penetrates to about 1,000-m depths, a distinct deep slope fauna is present below 2,000 m, 

and a broad transition zone occurs between 1,000-and 2,000-m depths. Pequegnat et al. 

(1990) rejected this view, but it must be acknowledged that the analysis format used to 

reject the view were not suitable for evaluating the Carney et al. (1983) hypothesis.

Offshore oil and gas exploration and development on the continental slope did not 

accelerate until the late 1990s. This resulted in a renewed interest in the continental slope 

ecosystem, and researchers rediscovered the NGOMCS study. However, it was also 

learned that the NODC database from this study had been lost or corrupted (Carney 

2001), and the 48,000 benthic photographs were also lost. We, however, had retained 

hard copies of the data as well as duplicate photography. Under contract to MMS, we 

reconstructed the database and updated it to include revisions from work that occurred 

after the original study was completed. The updated database and the archived

photographs were submitted to MMS and have been made available to a new MMSsponsored deep-sea study being conducted by Texas A&M University.

This paper is primarily intended to provide a summary of some of the key

NGOMCS Study findings, and also includes some new analyses addressing the zonation 

concept. We address the question of whether 1) there are three distinct megafaunal 

assemblages represented between the shelf edge and about 1,000 to 1,200 m, and that 

within each of these the fauna is homogeneous (i.e. does not change with depth); or 2) 

whether the fauna changes with depth in such a way that the general pattern of change is 

that of a nonrepeating sequence of species arrayed along the depth gradient. 

While, theoretically, sampling had been targeted to occur at the mid-point of a 

defined biological zone, a much broader depth range of depths was typically sampled 

than was planned. We assigned samples to evenly-spaced 100-m depth intervals between 

300 m and 3,000 m, and had good coverage for each of these depth intervals between 300 

and 1,200 m. The primary question we address below is whether there are three distinct 

and homogeneous biological zones represented between 300 m and 1,000 to 1,200 m or 

whether the biota changes continually with depth. Both the Pequegnat et al. (1990) and 

Carney et al. (1983) viewpoints include a monotonous environment and biota between 

1,000+ m to 2,000+ m where the fauna changes abruptly.

APPROACH AND METHODS

The sampling program of the NGOMCS Study was structured to test whether the 

abundance and composition of the biota on the continental slope varied in response to 

changes in any of several spatial, temporal, or physiochemical variables. 
3

Analytical Design

A major component of the analytical design was the location of sampling stations. 

Sampling stations were located between the 200-m and 2,900-m isobaths on the

continental slope of the northern Gulf of Mexico between about 86° and 94° west 

longitude (Fig. 1). Station locations by depth reflected the desire to compare fauna 

among depths and thus test the depth-zonation concept; sampling locations east and west 

of a central Gulf transect were intended to characterize the different OCS planning

regions.

Three series of sampling stations, or transects, one in each MMS lease planning 

area, formed the nucleus of the sampling plan. (Additional areas were eventually

sampled, for reasons to be discussed later.) Some characteristics of these three transects 

and the planning areas they represented are as follows:

1. Central Lease Planning Area—The transect representing this area

extended across the slope in the vicinity of the Mississippi Trough, 

from approximately 28°20'N, 89°40'W to 26°40'N, 89°20'W (Fig. 1). 

The area has extremely active sediment movement, relatively high

terrigenous inputs, and few striking topographic features; it is

occasionally bathed by the Loop Current.

2. Western Lease Planning Area—The transect in this area extended

across the slope just south of the Flower Garden Banks, from 27°25'N, 

93°40'W to 25°50'N, 93°30'W (Fig. 1). The area has relatively sluggish 

circulation, a number of pronounced topographic features, and

moderate to low declivity compared to the Mississippi Trough

Transect.

3. Eastern Lease Planning Area—The sampling transect crossed the

Florida Escarpment from 27°40'N, 85°15'W to 27°30'N, 85°40'W (Fig. 

1). The area has high declivity (especially on the lower slope), a low 

rate of terrigenous input and sedimentation, and moderate to strong

currents along the face of the slope.

Various combinations of these transects were sampled on Cruises I, II, and III. 

Cruises IV and V sampled additional areas in the eastern and western Gulf, respectively 

(Fig. 1). Descriptions of the sampling efforts on each cruise, and the rationale for such 

efforts, are described below.

On Cruise I (fall 1983), five stations at five different depths were sampled on the 

central transect (Fig. 1). The primary purpose of Cruise I was to collect samples within 

previously-defined faunal zones over a wide depth range (300 to 2,400 m) as a basis for 

refining future sampling efforts.
4

94° 92° 90° 88° 86°

26°

28°

30°

2

100m

500m

1000m

1500m

2000m

2500m

1

2

3

4

5 

W WC

1

11

2

3

4

5

6

12 4

7

9

8

10

1 6

3

7

8

9

12

5

11

10

1a

1

1b

1c

2a

2b2

2c

2d

2e

3a

3d

3 

3b 4

5

C

E

3c

GULF OF MEXICO

3000m

Figure 1. Sample sites in the Gulf of Mexico.
5

Cruise II (spring/summer 1984) re-sampled the stations occupied on Cruise I and 

also extended the geographic coverage to the western and eastern regions of the Gulf 

(Fig. 1). Cruise II results provided data for comparisons among planning areas and 

depths, and for stations on the central transect, between seasons.

During Cruise III (fall 1984), the five original central transect stations were sampled 

again in fall 1984, along with seven additional stations (Fig. 1). The seven new stations 

were located on the central transect at different depths from the first five stations. The 

locations for the additional stations were mainly in suspected biological "transition" areas 

and were based upon the advice of the program's Scientific Advisory Committee. 

Sampling the five original central transect stations allowed comparisons to be made 

between the fall cruise of 1983 and that of 1984.

 During Cruise IV (spring/summer 1985), 16 stations were sampled near and on the 

eastern transect, including those previously occupied on the eastern transect on Cruise II 

(Fig. 1). The new stations were grouped by depth at approximately 350 m (four stations), 

625 m (six stations), 850 m (five stations), and 2900 m (one station). The purpose of this 

grouping design was to test depth-related differences against variability related to

distance along these isobaths. Annual variability could also be studied by comparing the 

data from Stations E1, E2, E3, and E5 on Cruise IV (Fig. 1) to data from Cruise II (Fig. 

1) from the same stations a year earlier.

Station locations for Cruise V (spring/summer 1985) (Fig. 1) were chosen on the 

basis of two major needs. First, the area of sampling between the western and central 

transects was subject to ongoing and expected future oil and gas exploration and

development activities, and many sites were selected along depth contours in this area to 

document longitudinal variability in sediment and biological characteristics. Second, 

hydrocarbon seeps had been reported in the area, and the associated biota had not been 

well documented. Two suspected areas of hydrocarbon seeps (Stations WC6 and WC7) 

were chosen to compare with probable “control” (non-seep) areas at comparable depths 

(Stations WC8 and WD2). Further, samples at WC11 (a topographic high feature 1,226 

m deep) were compared to samples at WC12 (a topographic depression 1,236 m deep).

The sampling strategy described above permitted project scientists to make the 

following contrasts:

Contrast Data Source

ANOVA 1 Seasonal, geographic, and Central Transect, Cruises I & II

annual variation by depth Western, Central, and Eastern

Transects, Cruise II; Central

Transect, Cruises I & III

ANOVA 2 Zonation Patterns Central Transect, Cruise III, plus data

from all other cruises

ANOVA 3 Variation within depths, West-Central Cruise V

Western Gulf

ANOVA 4 Variation within depths, Eastern Transect, Cruise IV

Eastern Gulf
6

These sampling design considerations allowed researchers to analyze faunal

distributions and abundance in space and time. Additional relationships of interest were 

the influences of sediment size, presence and types of hydrocarbons, and water quality on 

faunal distribution and abundance. Sediments and hydrocarbons were analyzed from the 

same samples from which meiofauna and macrofauna were analyzed; this allowed for 

comparisons among these physical variables and these faunal groups. Water quality was 

analyzed from samples taken along sampling transects providing data to compare with 

faunal characteristics of those transects.

Field Methods

Hydrographic Measurements

Continuous and discrete measurements of hydrographic parameters were obtained 

throughout the water column (surface to bottom) at five stations on each cruise. A NeilBrown Mark III CTD/Rosette/Transmissometer System was used to obtain continuous 

data and discrete water samples. Continuous conductivity (salinity), temperature, depth, 

and transmission records were provided by the Neil-Brown CTD. At each station, a 12-

bottle rosette attached to the CTD was used to collect 12 discrete water samples for 

measurements of temperature, salinity, dissolved oxygen, nutrients, and particulate

organic carbon. Bottles were spaced throughout the water column in order to delineate 

the major water masses at each site. The CTD/Rosette/Transmissometer System was 

deployed with a pinger so that the cast could be safely lowered to within a few meters of 

the bottom. This was done in order to discern whether there were bottom nepheloid 

layers at each site.

Box Core Sampling (Meiofauna/Macrofauna)

Box core samples were taken at each station to obtain material for macroinfauna and 

meiofauna identification, sediment grain size, carbonate, total organic carbon, carbon 

isotopes, and hydrocarbons. Six replicate samples were taken at each station, except on 

the western and eastern transect stations during Cruise II, when only three replicates were 

taken per station. The replicates were then subdivided to provide material for the various 

types of analyses.

Box corers were deployed in yoked pairs, using a TAMU-modified version of the 

Gray-O’Hara modification of the J&O box corer (Fig. 2). On many occasions, only one 

cast was required to collect two replicates. The box corer measured 24.5 x 24.5 x 44 cm. 

It was fitted with a hinged door to prevent washout of samples, and had up to 135 kg of 

ballast. The door was open until the device had penetrated the substrate, whereupon the 

jaws and the door closed. The amount of ballast was adjusted to ensure adequate 

substrate penetration.
7

Box Core Configuration - Cruise I

Box Core Configuration - Cruises II-V

Meiofauna and Sediment Sample Cores

(Area = 9.6 cm / core) 2

Macrofauna Sample

(Area = 0.0569m ) 2

Meiofauna and Sediment Sample Cores

(Area = 9.6 cm / core) 2

Macrofauna Sample

(Area = 0.0475m ) 2

Figure 2. Box core and configuration of in situ subsampling tubes in the box corer.
8

The box corer contained six metal coring tubes, 43.5 cm long and 3.5 cm in interna l 

diameter. During Cruise I, these tubes were mounted in three pairs on a wire rack in the 

center of the box. This design was improved on successive cruises by mounting all six 

tubes against one wall of the box and securing them behind an aluminum partition that 

extended the full depth of the box. As each box corer came onboard, the overlying water 

was carefully siphoned into the macrofauna container, and the remaining subsamples 

processed according to their intended uses.

Trawl Sampling (Megafauna)

Megafauna sampling was performed with a standard 9-m, semi-balloon otter trawl 

with 60-cm steel doors, 3.8-cm stretch mesh, and 1.3-cm cod end mesh. Target trawling 

times were one hour at stations shallower than 1300 m, and two or more hours at deeper 

stations. The amount of time on the bottom was arbitrarily measured as the time from 

winch brake application until the winch was started again for trawl retrieval. At a towing 

speed of one to three knots, a ratio (scope) of 3.5:1 between amount of wire out and the 

depth produced good samples.

The contents of each retrieved trawl were dumped into metal tubs. Fishes and 

invertebrates intended for hydrocarbon assays were quickly removed, photographed, and 

frozen. The remaining organisms were usually rough-sorted into three categories (fish, 

decapods, and "other"). They were then narcotized with isotonic magnesium sulfate if 

necessary, and preserved in 10% neutral buffered formalin in sea water.

Benthic Photography (Megafauna)

Benthic photographs were taken with the use of a Benthos Model 372 deep-sea 

camera fitted with a 28-mm lens (angle of view 35° x 48.5°), and equipped with a 200 

watt-second (Joule) Benthos strobe. On each visit to every station, the camera exposed 

800 frames of Kodak Ektachrome Professional 5936 film, ISO 200. Photographs were 

taken every eight seconds.

The photographic gear was mounted inside a protective framework (Fig. 3). This 

framework had a clock and altimeter that recorded the time and altitude above the bottom 

in the corner of each photograph. The altimeter had a resolution of ± 0.1 m.

The camera system was suspended from the vessel by a hydrographic wire, and 

allowed to drift near the bottom along transects 1500 to 5000 m long. This technique 

prevented skipping and bouncing on the bottom, thereby minimizing disturbance and 

reducing the chances of attracting or frightening animals away.

Altitude was maintained by adjusting the vessel's winch in response to an acoustic 

signal transmitted by a 12 kHz bottom-finding pinger on the framework. The signal was 

portrayed continuously on a strip chart recorder. Optimum camera altitude was

approximately 2 m above the bottom, which produced shots that included 2.27 m2 of the 
9

((((

((((

((((

45

o

Photographic Dimensions

1.3 x 1.8 m = 2.3 m

2

at 2 m altitude

Altitude

2 m

Optimum

Pinger

Camera

Altimeter

Strobe

Frame Length = 1.85 m

Weight inAir = 240 kg

Figure 3. Schematic diagrams of photographic system used for benthic photography.
10

bottom. However, acceptable shots were obtained at altitudes from 0.7 m (0.27 m2 area) 

to 4.0 m (9.09 m2 area).

Laboratory Methods

Laboratory activities included (1) analyzing sediments and biota for physical,

chemical, and hydrocarbon parameters and for carbon isotope ratios; (2) sorting,

identifying, enumerating, weighing, and measuring biota and analyzing their gut

contents; and (3) analyzing photographs for biota and lebenspurren. Standard methods 

were used throughout each analysis and were detailed in Gallaway (1988b).

In the NGOMCS study, meiofauna were defined as those metazoan organisms 

retained on a 0.063-mm sieve after the sample had been rinsed through a 0.300-mm sieve 

to remove larger macrofaunal organisms. Biomass of meiofauna was estimated using 

published values for the size ranges and types of organisms in the samples (Fauble 1982, 

Rowe et al. 1974). Results were presented as densities per 10 cm2 following Thiel 

(1983). Macrofauna were defined in the NGOMCS Study as those organisms collected in 

the box corer and retained on a 0.300-mm sieve. Representatives of four taxonomic 

groups (Nematoda; Copepoda, primarily harpacticoid copepods; Aplacophora; and

Scyphozoa) were not included as macrofauna in the NGOMCS Study despite being

retained on a 0.300-mm sieve. We include these forms in our synthesis as they constitute 

a significant fraction of the macrofaunal density and biomass that is not measured 

elsewhere.

Perhaps the most difficult aspect of the laboratory component of the study was the 

identification of the macrofauna. Our technicians field-collected and then sorted the 

collections to major taxonomic groups in the laboratory. With the exception of the 

polychaetes, we did not attempt to make any species-level identifications for any of the 

major groups represented in the collections. Rather, the rough-sorted samples were sent 

to an expert on the taxonomy of that group who made the species-level identifications. 

Overall, more than 30 taxonomic experts participated in the study (Fig. 4). Once 

identified, the samples and the data were returned to LGL. This process extended the 

time estimated necessary to identify the macrofauna by over one year. Nevertheless, the 

process yielded state-of-science level identifications, at least for that period in time.

Statistical Methods

Statistical treatment of the data included numerical classification (cluster analysis), 

calculation of diversity indices, and analysis of variance (ANOVA) on density values 

(Gallaway et al. 1988a; Gallaway 1988a, 1988b, 1988c). Also, correlation analyses 

(Pearsons product moment) were conducted, relating the density of the most abundant 

species to water and sediment quality variables.
11

TAXONOMIC EXPERTS

Nemertea - J. Wern (Texas A&M University) Isopoda - G. Wilson (Consultant)

Oligochaeta - C. Erseus (University of Goteborg) Ostracoda - L. Kornicker (Smithsonian Institution)

Polychaeta - G.F. Hubbard (LGL), P. Wolfe & Stomatopoda - D. Camp (Florida Dept. Natural Resources)

L. Sierte (B.A. Vittor & Assoc., Inc.) Tanaidacea - R. Heard (Gulf Coast Research Lab)

Bivalvia - F. Rokop (Scripps Institute of Oceanography), Decapoda - L. & W. Pequegnat (Consultants), P. McLaughlin

T. Waller (Smithsonian Institution) (Florida International University)

Cephalopoda - M. Sweeney (Smithsonian Institution) Asteroidea - D. Pawson (Smithsonian Institution)

Porifera - S. Pomponi (Consultant), D. La Chance (Consultant) Crinoidea - C. Messing (University of Miami)

Actiniaria - D. Dunn Fautin (Calif. Academy of Sciences) Echinoidea - D. Pawson (Smithsonian Institution)

Alcyonaria - J. Lowery (Consultant), S. Viada (LGL) Holothuroidea - R. Carney (Louisiana State University)

Scleractinia - S. Cairns (Smithsonian Institution), S. Viada (LGL) Ophiuroidea - G. Hendler (LA County Museum of

Hydrozoa - D. Calder (Royal Ontario Museum) Natural History)

Gasteropoda - P. Bouchet (Museum National d'Historie Naturelle) Brachiopoda - G.A. Cooper (Smithsonian Institution)

Scaphopoda - J. Kraeuter (Baltimore Gas and Electric) Bryozoa - A.J.J. Leuterman (Dresser Industries)

Pycnogonida - C.A. Child (Smithsonian Institution) Sipunculida - M. Rice (Smithsonian Institution)

Pogonophora - M. Jones (Smithsonian Institution) Tunicata - C. & F. Monniot (Museum National d'Historie

Amphipoda - L. McKinney (Texas Parks and Wildlife) Naturelle)

Cirripedia - H. Spivey (Florida State University) Fishes - C. Chandler (LGL), E. Matheson & J. McEachran

Cumacea - N. Jones (University of Liverpool) (Texas A&M University)

Figure 4. Taxonomic experts involved in faunal identifications for the NGOMCS study.
12

Hurlbert’s modification (1971) of the rarefaction method (Sanders 1968) was used 

to predict the number of species in a random sample without replacement, given a 

population N:

N -N

m

i ( )

N

( m )

E(S ) = 1 - m

^

Σ

k

i=1

 

in which N1 is the finite population of species i; and E( m) is the variable denoting the 

expected number of species in a random sample of size m (Smith and Grassle 1977). N is 

the total number of individuals in the finite population:

Σ Ni

For the macrofauna species diversity results, we used m=50 or the number of species per 

50 individuals; m=100 or the number of species per 100 individuals; m=500; m=1,000; 

m=2,000; and m=3,000. For megafauna diversity, we used m’s ranging from 15 to 150.

ENVIRONMENTAL CHARACTERIZATION

One of the primary objectives of the NGOMCS Study was to describe the

environment of the continental slope of the northern Gulf of Mexico in terms of overlying 

water masses, bottom water conditions, sedimentary character and hydrocarbon levels in 

the sediments. The overall purpose of this physical-chemical characterization was to 

identify spatial and temporal variations or discontinuities that might account for or be 

related to biological features. A major emphasis was placed upon the sources of, and the 

present levels of hydrocarbons in the sediments. Originally, this effort was perceived to 

be of most importance in that the data would constitute a pre-development baseline which 

could be used as a standard against which to compare the effects of hydrocarbon

development on the continental slope. Sediment hydrocarbon levels were determined to 

influence biological communities of the slope, even when present in only trace amounts 

(Gallaway and Kennicutt 1988).

The primary water column difference between the Gulf of Mexico continental slope 

and other slope systems is that the shallow sill depth (~1900 m) at the Yucatan Strait 

connection between the Gulf and the Atlantic prevents the input of cold (2°C) bottom 

waters. As a result, slope habitats below 2000 m remain relatively warm (~4°C). Depth 

variation in temperature, salinity and dissolved oxygen exhibited classical and expected 

patterns and there were no, or only minimal, regional differences in these patterns.
13

Sediment characteristics did exhibit regional differences. The most common

sediment type on the slope was silty clay, occurring in all geographic regions. However, 

in the eastern Gulf this general sediment type had higher percentages of sand than in the 

western or central areas of the Gulf. Clay sediments were found in the western and 

central Gulf but were not present in any of the eastern Gulf samples. In contrast, sandsilt-clay sediments were represented at some eastern Gulf stations but absent from the 

western Gulf stations. Sandy clay was found at shallow and deep stations in the western 

Gulf and at deep stations in the eastern Gulf.

Gulf of Mexico slope sediments contain a mixture of terrigenous, petroleum, and 

planktonic hydrocarbons. The influence of river/land derived material is widespread and 

is probably delivered to the slope by secondary sediment movement such as slumping 

and slope failure. Petroleum hydrocarbons were detected at all locations and have a dual 

source in natural seepage and river-associated transport. Other contemporary studies 

suggested that natural seepage is much more widespread on the Gulf of Mexico slope 

than previously thought and probably represents a significant input of petroleum

hydrocarbon to Gulf slope sediments (Brooks et al. 1985, Lacerda et al. 1987, Kennicutt 

et al. 1987).

In general, the concentration of hydrocarbons in slope sediments (except in seep 

areas) was lower than previous reports for shelf and coastal sediments but no consistent 

decrease with increasing water depth was apparent below 300 m. Hydrocarbon

distributions, in general, were observed to be patchy on the slope and this may have been 

due in part to the non-uniform distribution of natural seepage on the slope. Variability in 

hydrocarbon concentrations were as much as 1 to 2 orders of magnitude along an isobath, 

due to changes in sediment texture and hydrocarbon inputs. Hydrocarbons were

preferentially associated with clayey, organic-rich sediments suggesting a linkage with 

river-derived material. Aromatic hydrocarbon concentrations were very low at all

locations but their presence was confirmed by fluorescence analysis.

Megafaunal organisms collected from non-seep areas had variable levels of

hydrocarbons in their tissues, mainly derived from the sediments either directly or from 

organisms that had ingested sediments (Gallaway and Kennicutt 1988). Hydrocarbons 

were more prevalent in fishes than in decapod crustaceans. Terrigenous hydrocarbons 

were common but the majority of the hydrocarbons appeared of plankton origin.

Results of the Principal Component Analyses (PCA) suggested distinct regional 

differences in slope habitats, with the central Gulf having the highest levels of total 

organic carbon and petroleum hydrocarbons and the lowest levels of sand in the

sediments (Gallaway and Kennicutt 1988). The stations in the eastern Gulf had the 

lowest levels of organic carbon and hydrocarbons in slope sediments and the highest 

levels of sand. Stations along the western Gulf slope transect were intermediate between 

these extremes. Data from each regional transect suggested differences along the transect 

by depth, namely that the proportion of plankton-derived hydrocarbons and the petroleum 

indicator of high molecular weight hydrocarbons (PE-Hi) increased with depth and 

distance from shore. There was also an indication of higher organic carbon and
14

petroleum levels associated with topographic irregularities that would enhance sediment 

accumulation.

Results of the PCA designed to evaluate depth differences suggested distinct 

differences in habitats by depth on the central transect. Three general habitats were 

indicated—shallow (<500-m deep), deep (>2000 m) and intermediate (500- to 2000-m 

deep). This suggests a distinct deep-shelf habitat, connected by a broad transition zone to 

a distinct abyssal habitat beginning at about 2000 m. Subsequent PCA's conducted on 

samples collected along isobaths suggested habitats along depth contours differed more 

by depth than along a depth contour.

BIOLOGICAL CHARACTERIZATION

Fifty-nine (59) of the 60 planned box core samples were obtained and analyzed. 

However, macrofaunal data from station C1, replicate 3 and C12, replicate 4 were lost to 

laboratory error (samples were sorted to major group, but improperly preserved and then 

deteriorated prior to identification). Similarly, 59 of the 60 planned trawl tows were 

taken but an additional 14 of the tows experienced problems such that the data collected 

could not be considered quantitative (Appendix 1). A total of 45 quantitative tows were 

obtained. None of the benthic photography samples from Cruise I (5 stations) yielded 

quantitative data. However, quantitative data were obtained from all other cruise and 

station combinations. 

The overall distribution of biological sampling effort by depth is shown by Table 1. 

Reasonable coverage was obtained for all gear types to depth intervals between 300 and 

1,500 m. Little or no sampling was conducted using any gear between 1,600 and 2,000 

m, and limited box core, photographic, and trawl sampling was conducted between 2,100 

and 3,000 m. 

Meiofauna

The meiofauna collections contained in excess of 230,000 individuals representing 

43 major groups of animals (Gallaway et al. 1988b). However, representatives of five 

taxa of permanent meiofauna (Nematoda, Harpacticoida, Polychaeta, Ostracoda, and 

Kinorhyncha) along with naupliar larvae (temporary meiofauna) comprised 98% of the 

collections. Numerically the collections were dominated by nematodes and

harpacticoids, but on a biomass basis polychaetes and ostracods were dominant. This 

structure was remarkably consistent across all stations, regions, seasons, and years

(Gallaway et al. 1988b).

From inspection of the overall density patterns, meiofaunal abundance appeared 

somewhat greater in spring than in fall and higher on the central transect than on the 

eastern and western transects. Also, there was an overall trend of decrease in abundance 

with depth, but this was not always the case.
15

Table 1

Distribution of Total Area Sampled by Gear Type and Depth Interval

Depth Interval Box Core (m2) Camera (ha) Trawl (ha)

300 1.206 0.165 10.744

400 1.748 0.316 15.616

500 0.950 0.203 10.077

600 3.571 0.351 24.985

700 0.238 0.166 5.330

800 1.871 0.308 33.522

900 1.368 0.188 11.285

1000 0.285 0.055

1100 0.095 0.047 6.413

1200 0.713 0.117 7.787

1300 0.209 0.078

1400 1.130 0.102 10.744

1500 0.238

1600 0.057

1700

1800

1900

2000

2100 0.285 0.055

2200

2300

2400 0.285 0.086 5.663

2500 0.769 0.029 5.122

2600

2700

2800 0.095

2900 0.475 0.136

3000 0.143
16

A more detailed examination of depth distribution was enabled from the fall 1984 

sampling on the central transect. The results of this sampling also suggest a general 

decline in abundance with depth with notable exceptions to the pattern exhibited at 

Stations C7 and C4. The former station had anomalously high petroleum hydrocarbon 

levels and was documented to have had a population of chemosynthetic bivalves.

Relatively little variation was observed along isobaths sampled in the eastern and 

western Gulf of Mexico, and little across-isobath variation was noted for the depth

intervals sampled on these cruises. The samples reflected remarkable constancy.

Mean density of meiofauna across all stations in this study was 700 organisms/10 

cm2, with individual station values ranging from about 200 to 1,100 organisms/10 cm2. 

In general these counts appear higher than comparable meiofaunal values for the western 

Atlantic (Wigley and McIntyre 1964, Tietjen 1971, and Coull et al. 1977 as shown in 

Thiel 1983). There, maximum values were on the order of 100 to 400 individuals/10 

cm2. Sieve sizes used in the referenced western Atlantic samples ranged from 0.042 to 

0.074 mm as compared to the 0.063 mm sieve used in this study. From this comparison 

we conclude that the Gulf meiofaunal densities are greater than those of the U.S. Atlantic. 

In fact, review of the data presented in Thiel (1983) suggests that the meiofaunal

densities observed in this program are among the highest recorded in any deep-sea 

habitat.

Both macrofauna and meiofauna numbers and biomass decreased overall with depth. 

For the macrofauna, numbers declined less rapidly than biomass, suggesting that

macrofaunal size decreased with depth (Fig. 5). For the meiofauna, numbers also 

declined less rapidly than biomass but the difference between the two slopes was

marginal, suggesting little change in size. In contrast to Thiel’s (1983) findings, we 

observed densities of meiofauna to decline at a more rapid rate than densities of

macrofauna (ratio between meio- to macrofaunal slopes was 1.67 to 1 as compared to 0.5 

to 1 in Thiel). However, the macrofauna were screened using a 0.300 mm sieve in our 

program, whereas Rowe (1971) used a screen size of 0.42 mm in his studies. Rowe’s 

(1971) results formed the basis for Thiel’s comparison.

Because of the gross level of taxonomy used (and available) for the meiofauna, 

detailed correlations were considered unwarranted. However, some observations were 

made. As noted above, significant exceptions to the trend of decreasing density of 

meiofauna with depth were observed. These included Stations C4 and C7 sampled on the 

central transect in fall 1984. Station C7 had enriched levels of petroleum hydrocarbons 

and benthic photographs revealed a dense community of chemosynthetic clams in the 

surface sediments. This may be indicative that when localized chemical enrichment of 

sediments provides the basis for a chemosynthetic food web, a general increase in

infaunal density and diversity may occur in the larger area.
17
18

Some 500 specimens of the phylum Loricifera were collected during the NGOMCS 

Study at depths ranging from 298 to 2,959 m (Hubbard et al. 1988). They were collected 

from all but four of the stations sampled. This phylum was only described in 1983

(Kristensen 1983) based upon specimens collected from near Roscoff, France; the

Azores; and near Fort Pierce, Florida at depths ranging from 15 to 480 m. Specimens of 

this phylum were reported by Kristensen to be generally overlooked since a species shock 

treatment with freshwater was required to effectively dislodge them from marine

sediments. One must wonder how many might have been collected if our samples had 

been treated accordingly. In any case, the NGOMCS Study findings substantially

increase both the geographic and depth ranges for the Loricifera.

The meiofauna of the Gulf of Mexico were poorly known at the time of the 

NGOMCS Study and remain so. However, meiofaunal densities on the continental slope 

of the Gulf were high in the mid 1980s and rivaled or exceeded the macrofauna in 

biomass, attesting to the small size of Gulf macrofauna. The patterns of abundance as 

compared to the macrofauna lend credence to the idea that, in comparison to other slope 

systems, food or energy availability in the Gulf may be low, thereby limiting population 

density levels.

Macrofauna

A total of 69,933 organisms representing in excess of 1,548 differentiable taxa were 

obtained by the NGOMCS Study (Table 2). It should be noted that we have included 

some forms generally considered as meiofauna (e.g., Nematoda, Harpacticoida,

Cyclopoidea) in the macrofaunal counts. Larger specimens of these groups were retained 

on the 0.300-mm screen and, if not included in the macrofauna counts, would not be 

represented in any of the samples. These forms constitute up to half or more of the total 

density and biomass of the slope infauna. One characteristic of the Gulf-slope 

macrofauna which was remarked upon by many of the taxonomic experts who identified 

the species within groups was their small size as compared with the western North

Atlantic.

The taxonomic experts were able to identify 1,107 species within the 46 major 

groups. Polychaetes were represented by 405 species, tanadaceans were represented by 

168 species and 119 species of isopods were identified (Table 2). Selective and nonselective deposit feeders (196 taxa) dominated the polychaete collections in terms of total 

counts and number of taxa. However, more families of carnivorous polychaetes were 

collected than families or any other category, but their abundances were less than either 

deposit feeders or omnivores (Pequegnat et al. 1990). Scavengers were the least

abundant of any of the polychaete feeding types.

Overall, macrofaunal density appeared to decline with depth, especially between 

1,000 to 3,000 m (Fig. 6). However, there was a large gap in sampling effort between 

1,500 and 2,100 m. There was no marked trend of decline between 300 and 1,500 m 
19

Table 2

 Relative Abundance of Major Macrofaunal Groups

Number of Number of Number of Number of

Taxonomic Group Abundance Taxa Species Genera Other Taxa

Polychaeta 24,547 601 405 151 45

Nematoda 17,020 1 1

Ostracoda 4,931 22 18 1 3

Harpacticoida 3,727 1 1

Bivalvia 3,648 55 41 10 4

Tanaidacea 3,579 186 168 13 5

Bryozoa 3,043 99 82 12 5

Isopoda 2,372 133 119 8 6

Amphipoda 1,277 76 49 10 17

Aplacophora 871 1 1

Nemertini 645 20 19 1

Ophiuroidea 602 17 13 3 1

Sipuncula 568 36 30 3 3

Cumacea 508 85 75 8 2

Porifera 416 39 21 11 7

Scaphopoda 381 10 5 2 3

Scyphozoa 331 1 1

Gastropoda 278 52 8 26 18

Holothuroidea 249 13 4 4 5

Oligochaeta 248 9 6 1 2

Ascidiacea 135 18 11 3 4

Hydrozoa 102 15 8 3 4

Brachiopoda 79 2 2

Halacaridae 62 1 1

Kinorhyncha 60 3 2 1

Echinoidea 49 6 3 1 2

Priapulida 33 1 1

Scleractinia 33 6 4 1 1

Cyclopoida 28 1 1

Decapoda 25 13 10 1 2

Mystacocarida 12 1 1

Pogonophora 11 1 1

Echiura 9 1 1

Actiniaria 8 3 3

Alcyonaria 8 2 1 1

Turbellaria 8 1 1

Crinoidea 7 2 2

Pycnogonida 7 4 3 1

Anthozoa 4 2 2

Hemichordata 4 1 1

Asteroidea 2 2 1 1

Mysidacea 2 1 1

Archiannelida 1 1 1

Cephalochordata 1 1 1

Cirripedia 1 1 1

Osteichthyes 1 1 1

______ ____ ____ ___ ___

69,933 1,548 1,107 276 165
20
21

(peak abundance occurred at 1,000 m) nor was there a trend of decline between 2,100 and 

2,900 m. However, the densities in the later region were substantially lower than

observed densities between 300 and 1,500 m. The actual pattern of the decline between 

these two depths was not documented. The lowest density was observed at 3,000 m. 

Overall, the decline of macrofaunal abundance with depth fits a linear model (p<0.0001, 

r

2

 = 0.58), especially for the depth region between the 1,000-m peak and the 3,000-m 

low.

As noted in Pequegnat et al. (1990), macrofaunal abundance (excluding nematodes 

and copepods) was higher in spring than in fall and, in spring, higher on the central 

transect (x = 3,437 individuals/m2) than on the eastern (x = 2,878 individuals/m2), and 

western transects (x = 2,189 individuals/m2). Note that these numbers differ somewhat 

from the values shown in Pequegnat et al.’s (1990) Figure 4. The changes reflect 

corrections and updates made to the data after program completion. 

Total macrofaunal density patterns based on all macrofauna (including nematodes 

and copepods) also showed higher abundance in spring than in fall. In spring, abundance 

on the central (x = 4,938 individuals/m2) and eastern transects (x = 4,869 individuals/m2) 

were similar and higher than abundance on the western transect (x = 3,389

individuals/m2). Note that densities including total organisms retained on the 0.300-mm 

mesh screen are some 1.4 to 1.7 times higher than the densities reflected when large 

specimens of meiofaunal taxa (e.g., nematodes and copepod) are not included.

Thirteen species of polychaetes were included in the list of 18 macrofaunal species 

which constituted as much as 2% of the total macrofaunal collection (Table 3). Of these 

13 species, three (Litocorsa antennata, Pholoe “Sp. C”, and Fauveliopsis Sp. B)

exhibited high abundance at depths between 300 and 1,000 m, and one (Muldane, “Sp. A) 

was more abundant at deeper (> 1000 m) as opposed to shallower depths (300-900 m). 

The remaining nine species exhibited variable but generally high abundance across the 

entire depth range sampled, at least to 1,500 m.

Observed diversity of macrofauna on the continental slope of the Gulf was high. 

The 1,107 species identified were represented by a total of 28,609 specimens. There 

were 972 species in 22,604 specimens collected at depths < 1,000 m and 604 species 

contained in 6,005 specimens collected at depths greater than 1,000 m. The results of 

rarefaction analysis of these data were:

All Depths Depth < 1,000 m Depth > 1,000 m

Subsample Mean No. Species Mean No. Species SD Mean No. Species SD

50 39.56 38.42 2.85 36.46 2.90

100 68.74 66.31 4.21 64.18 4.22

500 207.28 195.45 8.10 195.20 7.84

750 263.22 247.01 9.05 247.00 8.56

1000 308.96 289.16 9.66 288.38 8.93

2000 439.51 409.63 10.82 402.13 9.04

3000 527.82 491.35 11.20 474.89 8.33
22

Table 3

Density (no/m2) of the 13 Polychaetes that Comprised as Much as 2% of the Total Macrofaunal Collection

(Bold line represents high density zone)

Polychaeta Species 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

Litocorsa antennata 268 130 249 116 4 4

Pholoe "Sp. C" 17 26 9 54 59 35 4

Levinsenia gracilis 39 39 52 35 38 22 10 14 8 5 9 8

Fauveliopsis Sp. B 22 27 4 20 8 20 29 4 21 22 10 10 4

Aricidea suecica 45 54 27 27 4 15 32 39 3 62 27 42

Aurospio dibranchiata 153 144 46 90 17 85 75 126 28 36 93

Prionospio ehlersi 41 70 88 25 8 10 9 4 32 1 6 25

Sarsonuphis hartmanae 16 16 33 37 17 11 13 4 21 15 19 8 17

Spiophanes berkeleyorum 44 27 63 43 8 30 30 81 42 13 14 32 29

Tachytrypane Sp. A 48 52 87 67 17 14 14 25 3 4 13

Exogone "Sp. A" 7 17 17 37 13 36 29 32 32 11 72 44 67

Terebellides atlantis 5 19 12 38 33 55 25 4 14 19 42

Maldane "Sp. A" 1 2 3 1 2 3 1179 305 177 220 277 968
23

There was little difference in the number of species represented in a given subsample size 

between depths, except for the largest of the sample sizes. At large sample sizes, 

macrofauna were more diverse at depths less than 1,000 m than at deeper depths.

Densities of macrofauna observed at NGOMCS Study sampling sites were generally 

lower than densities observed in contemporary continental slope studies being conducted 

in the Atlantic (Maciolek-Blake et al. 1985, Maciolek et al. 1986), especially at depths 

shallower than 1,000 m (Fig. 7). The differences in density between the Gulf and the 

Atlantic were less pronounced at deeper depths. The implication is that density of

macrofauna on the continental slope of the Gulf declines at a much lower rate than is the 

case along the north- and mid-Atlantic coasts of the U.S.

In contrast, diversity of macrofauna at sampling sites on the upper Gulf slope (< 

1,000 m) was observed to be much higher than was observed at depths less than 1,000 m 

on the Atlantic slope (Fig. 8). However, between depths of 1,000 m and 2,000 m, the 

Atlantic rarefaction curves for macrofauna all fell within the envelope of Gulf

macrofaunal rarefaction curves. Further, at depths between 2,000 m and 3,000 m, the 

Gulf curves all fell within the envelope of Atlantic curves (Fig. 8). Thus, the observed 

diversity difference between the Atlantic and the Gulf was restricted to depths shallower 

than 1,000 m, the same area where density differences were most pronounced. The 

shallow (< 1,000 m) Gulf slope was characterized by high diversity and low abundance 

as compared to the same region of the Atlantic slope which had relatively high density 

and low diversity.

Megafauna

The NGOMCS Study trawl collections contained 5,751 specimens of fish

representing 153 taxa of which 124 were identified to species. The trawl collections 

contained about 6 times more invertebrates (33,695 specimens) than fish. The trawl 

collection of invertebrates contained some 538 taxa of which 392 were identified to 

species. The photographs taken during the NGOMCS Study contained some 517 fishes 

among which 76 taxa were delineated. In contrast, some 56,052 observations

representing 193 taxa of non-fish organisms were photographed. The observed plants 

and invertebrates in the latter category ranged from bacterial mats, to sargassum weed to 

colonial and individual invertebrates. Of these, roughly one-half of the observations 

(28,393) were represented by pteropod (a pelagic gastropod) shells. The photographic 

samples were dominated by holothurians (11,423 observations), bivalves (2,832

specimens, mainly from a chemosynthetic clam bed), and alcynarians (1,744 specimens, 

mainly sea pens). None of these groups were amenable to effective sampling by

trawling. In fact, not one of the dominant holothurian photographed throughout the study 

area (Peniagone sp.) was trawled.
24
25
26

Decapod crustaceans were the fourth most abundant major taxa in the benthic

photographs and they dominated the trawl collections. Decapods and demersal fish are 

used as a basis for comparison of abundance trends represented by the two different 

sampling approaches. 

Abundance and Diversity

Megafaunal invertebrate and fish densities were variable but high between depths of 

300 and 1,200 m as compared to densities observed between 1,400 and 2,400 m (Figs. 9 

and 10). Megafaunal invertebrate trawl densities increased at 2,500 m and a different 

species composition than was observed at shallower depths was associated with this 

increase. Holothurians were the dominant component. The trawl data (Fig. 9) reflect two 

peaks in invertebrate and fish abundance; the highest occurred at 500 m, and another but 

lower peak was evident between 1,100 and 1,200 m. The decline in abundance after 

1,200 m was abrupt and abundance remained low down to 2,400 m. The overall trend is 

one of decline with depth, but the rate of decline is not necessarily consistent across all 

depths.

The densities of decapod crustaceans from both the trawl and photographic sampling 

reflected a pattern similar to that described for the total invertebrate collections (Fig. 10). 

Abundance was variable but generally declined with depth from between about 500 and 

1,200 m, after which abundance was markedly lower than the peaks seen at shallower 

depths (Fig. 10). The fish density data showed an oscillating abundance pattern between 

300 and 1,200 m followed by a step decline. Low abundance was characteristic of all 

sampling depths between 1,300 and 2,900 m.

The camera and trawl densities [transformed using loge (n+1)] were regressed on 

depth and subjected to analysis of covariance. Both regressions were significant at p <

0.001 and the slopes of the two regressions were not significantly different. The

regression of the transformed trawl decapod densities on camera densities was significant 

(p = 0.0019, r3 = 0.599) with the relationships being expressed 

Loge (trawl density +1) = -3.0859 + 1.1552 loge (camera density +1)

Overall, the density of decapod crustaceans estimated from photographs was about 

3.2 times higher than the density estimates reflected by trawling.

A similar analysis comparing trawl and photographic sampling results was

conducted for the fish data. Significant regressions were obtained by depth, and the 

regressions had non-significant slope differences. The regression of trawl on camera 

density was significant (p = 0.001, r2 = 0.797) with their relationship being expressed

Loge (trawl density +1) = -3.0251 + 1.1916 x loge (camera density +1)
27
28
29

Again, fish densities calculated from the photographic samples were, on average, about 

three times higher than calculated trawl densities.

There were nine species of decapod crustaceans which comprised as much as 2% of 

the total decapod trawl collections, and 12 species of fish which comprised as much as 

2% of the total fish collections made by trawling. In each instance, these species showed 

sequentially overlapping depth distributions from 300 m down to 1,200 m, and none was 

abundant at 1,400 m (Table 4). Overall, the NGOMCS Study megafauna data support the 

idea that faunal composition changes continually with depth such that a distinct upper 

slope fauna penetrates to about 1,200-m depths and a distinct deep-slope fauna is present 

below 2,500 m. A broad transition zone characterized low abundance and diversity 

occurs between depths of 1,200 and 2,500 m.

Musick (1976) calculated Shannon-Weiner (H’) diversity indices for fish collections 

taken on the U.S. Atlantic continental slope. Diversity was observed to decline with 

depth between 500 and 2,600 m. Shannon-Weiner fish diversity indices calculated from 

the NGOMCS Study data exhibited similar magnitudes of diversity as shown by Muscik 

(1976), and diversity at deeper stations was lower than diversity at shallower stations 

(Fig. 11). However, in the Gulf, diversity was high between 500 and 1,200 m and then 

exhibited a step decline. Below 1,200 m, diversity was uniform at about one-half the 

level observed at shallower depths (Fig. 11). The Musick (1976) data reflected a near 

linear or exponential decay in diversity with depth.

Results of rarefaction analysis did not reflect a decline in fish or megafaunal

invertebrate diversity with depth between depths of 300 and 1,200 m (Fig. 12). For 

invertebrates, diversity at nine sampling depths between 300 and 1,200 m showed four 

groups of similar curves. The diversity levels for the three deepest depths (900; 1,100; 

and 1,200 m) fell among the highest observed (900 m), in the upper middle range (1,200 

m) and at the lowest (1,100 m) level of observed diversities. The depth pattern for fish 

diversity between depths of 300 and 1,200 m was similar to that observed for megafaunal 

invertebrates. There was no evidence of a depth-related decline in diversity for this depth 

range (Fig. 12).

Life History Data

Life history data were taken for megafauna trawled at the 60 sampling stations. The 

specimens were first measured and weighed, and invertebrates were sexed and examined 

externally to determine the number of ovigerous females. Fish were dissected to

determine food habits and state of maturity. As noted earlier, over 5,700 fish were 

collected, representing 124 species. However, most species were represented by fewer 

specimens than the number of trawls taken (60). Only five species were represented by 

more than 300 specimens, or on average as many as five specimens per trawl. Thus, 

while the data are of value because there is very little life history information concerning 

any of the species, they were not adequate to delineate trends or differences among 

regions, seasons, years, and depth.
30

Table 4

Densities of Abundant Decapod Crustaceans and Fish by Depth as Reflected by the 

Trawl Collections of the NGOMCS Study

Species 300 400 500 600 700 800 900 1000* 1100 1200 1300* 1400 1500*

Decapods

Penaeopsis serrata 94.6 97.5 3.3

Benthochascon schmitti 3.7 18.7 103 0.5 0.1

Uroptychus nitidus 0.1 4.3 10.2 0.4 0.0 0.4 0.6 0.6 0.1

Plesionika holthusi 0.6 7.5 52.3 11.1 0.7 0.4

Munida valida 21.4 49.5 5.4 1.1 0.4 0.5

Bathyplax typhla 0.1 38.6 60.2 37.7 2.5 0.4 0.6 0.6

Nematocarcinus rotundus 0.2 54.1 9.9 10.2 8.2 159 36.3 1.0

Stereomastis sculpta 3.8 1.1 7.7 5.3 10.4 12.1 0.7

Glyphocrangon nobilis 0.1 0.1 40.2 5.5 1.0

Fishes

Coelorinchus caribbaeus 9.3 4.2 0.0

Poecilopsetta beani 5.8 5.4 0.0 0.0

Chloropthalmus agassizi 4.9 12.6 2.7

Urophycis cirratus 7.1 6.4 18.0 0.7

Bembrops goboides 6.1 14.0 6.5 0.2 0.2

Epigonus pandionis 2.2 6.0 4.0 0.1 0.1

Coelorinchus coelorhynchus 2.0 4.5 9.7 0.5 0.4

Hymenocephalus italicus 0.3 14.0 6.5 0.2 0.2

Dibranchus atlanticus 1.3 17.9 8.3 9.0 2.5 1.0

Nezumia aegualis 0.6 5.9 3.0 1.2 1.2 0.1

Synaphobranchus oregoni 0.1 1.1 0.6 5.0 2.7 7.5 2.7 0.1

Gadomus longifilis 0.6 0.6 18.4 4.5

*Depth interval not sampled.
31
32
33

For the invertebrates, 465 (86%) of the total 538 taxa collected were represented by fewer 

than 60 specimens, but 22 taxa were represented by more than 300 specimens. However, 

among this group were four species that represent incidental species (e.g., small isopods 

and barnacles) contained in the tows. Although the numbers appear large, at least 

compared to the fish, even these data were not adequate to determine trends among 

regions, seasons, years, and depths. For the most part, a few large trawl catches comprise 

most of the data for each of the abundant species.

Nevertheless, some useful information was obtained from the megafauna

collections. The complete data and detailed life history accounts can be found in

Gallaway et al. (1988c). These data are synthesized below.

The length-weight data represent the largest of the life history data sets (Gallaway et 

al. 1988c). The relationships, even when pooled, all exhibited very tight fits to a linear 

regression, indicating low variability across seasons, years, and regions. These

relationships can therefore be used as a predevelopment, baseline measure of megafaunal 

health or condition. The relationships also enable one to estimate biomass levels of 

megafauna given numbers and size distribution.

The length data showed ovigerous females of a number of invertebrates to have been 

significantly larger than males and non-ovigerous females—not a surprising result. Our 

data were not adequate to determine any seasonal or spatial patterns in the distribution of 

decapod crustaceans in a given reproductive state.

Although the size frequency data were often bi- or multimodal, indicating the 

possibility of multiple age groups, the sampling schedule was not frequent enough to 

delineate growth patterns. More frequent sampling at fixed locations than was planned 

for the NGOMCS Study would be required. The data suggest, however, that with

adequate sampling (e.g., monthly) size groups or cohorts could be followed through time, 

yielding growth information.

We were able to obtain reasonably good trophic information from a limited number 

of specimens representing eight species of fish. Poor success in obtaining trophic 

information from fish raised from great depths is not unusual. Complete data for all fish, 

although fragmentary, is found in Gallaway et al. (1988c). Of the eight species, four 

were generally distributed at depths of about 500 m or less. Two (Coelorinchus 

caribbaeus and Poecilopsetta beani) fed mainly on polychaetes and amphipods,

respectively. The other two (Chloropthalmus agassizi and Bembrops gobiodes) were 

predatory on larger forms, feeding mainly on fish and natantia, respectively.

Dibranchus atlanticus occurred over a wide depth range, but was most abundant at 

depths of 500 to 800 m. While the biomass data would indicate that this small predator 

fed largely on small hermit crabs (pagurids) and polychaetes, these data are misleading 

since pagurids actually occurred in only two of 33 stomachs. The primary food of this 

species consisted of amphipods and polychaetes. Nezumia aequalis had a depth
34

distribution similar to Dibranchus atlanticus but fed almost exclusively on natantia 

(82%), based upon the contents of 13 stomachs.

Specimens of Gadomus longifillis and Synaphobranchus oregoni from which we 

were able to obtain stomachs in good condition were largely associated depths between 

800 and 1,200 m The diet of Synaphobranchus oregoni consisted of fish and natantia, 

whereas Gadomus longifillis fed mainly on natantia and copepods.

The biochemistry work on the NGOMCS Study, conducted to compliment the food 

habits investigation, showed that the megafauna of the continental slope of the northern 

Gulf of Mexico reflect the signatures of planktonic as well as terrestrial biogenic and 

petroleum hydrocarbons. Biogenic hydrocarbons of planktonic origin were the most 

prevalent, especially in the eastern Gulf. 

CONCLUSIONS

The results of our analysis of the data segregated by 100-m depth intervals provides 

little or no support for the hypothesis that there are three distinct and homogenous faunal 

bands on the upper slope between depths of 300 and 1,000 to 1,200 m. Macrofauna 

density, while highly variable between these depths, reflects no pronounced trend of 

decline (see Figure 6) and the polychaete density data by species reflect that while few 

species are restricted to the shallower depths and a few species occur at the deeper depths 

only, the vast majority occur throughout the depth range in question (see Table 3).

The megafaunal density data suggest two to three peaks in abundance at depths of 

roughly 300, 700, and 1,000 to 1,200 m (see Figures 9 and 10). However, when the data 

are examined on a species-by-species basis (e.g., Table 4), a continuum of overlapping 

distributions is seen grading from species restricted to shallower depths, to species 

generally restricted to mid-depths within the range in question, to species occurring at the 

deeper depths within the range. Sampling at broadly-spaced intervals within these

distributions would suggest zonation whereas results of sampling at a less-coarse interval 

reflects a pattern of a non-repeating sequence of species aggregated along the depth 

gradient. We conclude that the existing data discount the idea that there are three distinct 

megafaunal assemblages represented between the shelf edge and 1,000 to 1,200 m and 

that, within each of these, the fauna is homogenous. The fauna clearly changes with depth 

as described above.

Based upon our observa tions, the continental slope fauna in the Gulf of Mexico 

appears to differ from the slope fauna in the U.S. Atlantic in several ways. First, Gulf 

meiofaunal densities appear to be higher than those reported for the Atlantic. In fact, the 

meiofaunal densities observed in this program are among the highest recorded in any 

deep-sea habitat. Gulf densities of macrofauna, however, were generally lower than

densities observed in contemporary continental slope studies conducted in the Atlantic, 

especially at depths shallower than 1,000 m. In contrast, diversity of Gulf macrofauna at 

sites on the upper slope (<1,000 m) was observed to be much higher than was observed at 

depths less than 1,000 m on the Atlantic slope (see Fig. 8). The shallow Gulf slope was 
35

characterized by high diversity and low abundance as compared to the same region of the 

Atlantic slope.

As noted above, the faunal composition of the Gulf megafauna changes continually 

with depth such that a distinct upper slope fauna penetrates to about 1,200 m or so. A 

distinct deep-slope fauna appears present below 2,500 m. A broad transition zone

characterized by low abundance and diversity occurs between depths of 1,200 m and 

2,500 m. Fish diversity on the Gulf was observed to be high between 500 and 1,200 m, 

and then exhibited a step decline. Below 1,200 m, fish diversity was uniform at about 

one-half the level observed at shallower depths (see Fig. 11). This pattern contrasts 

greatly with that observed on the Atlantic slope. On the Atlantic slope, fish data reflected 

a near linear or exponential decay in diversity with depth.

The results of the NGOMCS study provide a snapshot of the Gulf slope environment 

and biota as it existed in the mid- to late 1980’s. The findings of this study provide a 

point of reference for the recent MMS-sponsored deep-sea study being conducted by 

Texas A&M University. If the general observations described herein are repeated, then it 

will be clearly evident that the Gulf slope system differs from that of the Atlantic.

LITERATURE CITED

Brooks, J.M., M.C. Kennicutt II, R.R. Bidigare, and R.R. Fay. 1985. Hydrates, oil 

seepage and chemosynthetic ecosystems on the Gulf of Mexico slope. EOS. 66:105. 

Carney, R.S., R.L. Haedrich, and G.T. Rowe. 1983. Zonation of fauna in the deep sea. 

Pages 371-398 in G.T. Rowe (ed.), Deep-Sea Biology. John Wiley & Sons, New 

York. 560 pp.

Carney, R.S. 2001. Management applicability of contemporary deep-sea ecology and reevaluation of Gulf of Mexico studies. U.S. Dept. of the Interior, Minerals

Management Service, New Orleans, LA. OCS Study MMS 2001-095. 170 pp.

Coull, B.C., R.L. Ellison, J.W. Fleeger, R.P. Higgins, W.D. Hope, W.D. Hummon, R.M. 

Rieger, W.E. Sterrer, H. Thiel, and J.H. Tietjen. 1977. Quantitative estimates of the 

meiofauna from the deep sea off North Carolina, U.S.A. Mar. Biol. 39:233-240.

Fauble, A. 1982. Determination of individual meiofauna dry weight values in relation to 

definite size classes. Cahierss de Biologie Marine, Tome XXIII:339-345.

Gallaway, B.J. (ed.). 1988a. Northern Gulf of Mexico Continental Slope Study, final 

report: Year 4. Volume I: Executive summary. U.S. Dept. of the Interior, Minerals 

Management Service, New Orleans, LA. OCS Study MMS 88-0052. 69 pp.
36

Gallaway, B.J. (ed.). 1988b. Northern Gulf of Mexico Continental Slope Study, final 

report: Year 4. Volume II: Synthesis report. U.S. Dept. of the Interior, Minerals 

Management Service, New Orleans, LA. OCS Study MMS 88-0053. 318 pp.

Gallaway, B.J. (ed.). 1988c. Northern Gulf of Mexico Continental Slope Study, final 

report: Year 4. Volume III: Appendices. U.S. Dept. of the Interior, Minerals

Management Service, New Orleans, LA. OCS Study MMS 88-0054. 378 pp.

Gallaway, B.J. and M.C. Kennicutt II. 1988. Chapter 2: The characterization of benthic 

habitats of the northern Gulf of Mexico. Pages 2-1 to 2-45 in B.J. Gallaway (ed.). 

1988. Northern Gulf of Mexico Continental Slope Study, final report: Year 4. 

Volume III: Appendices. U.S. Dept. of the Interior, Minerals Management Service, 

New Orleans, LA. OCS Study MMS 88-0054, 378 pp.

Gallaway, B.J., R.L. Howard, and G.F. Hubbard. 1988a. Chapter 3: Observations on the 

distribution and abundance of the meiofauna of the continental slope of the northern 

Gulf of Mexico. Pages 3-1 to 3-15 in B.J. Gallaway (ed.). 1988. Northern Gulf of 

Mexico Continental Slope Study, final report: Year 4. Volume III: Appendices. U.S. 

Dept. of the Interior, Minerals Management Service, New Orleans, LA. OCS Study 

MMS 88-0054. 378 pp.

Gallaway, B.J., R.L. Howard, and G.F. Hubbard. 1988b. Chapter 4: The macrofauna of 

the continental slope of the northern Gulf of Mexico: community structure, diversity 

and abundance as compared to environmental features. Pages 4-1 to 4-70 in B.J. 

Gallaway (ed.). 1988. Northern Gulf of Mexico Continental Slope Study, final

report: Year 4. Volume III: Appendices. U.S. Dept. of the Interior, Minerals

Management Service, New Orleans, LA. OCS Study MMS 88-0054. 378 pp.

Gallaway, B.J., L.R. Martin and R.L. Howard (eds.). 1988c. Northern Gulf of Mexico 

Continental Slope Study, annual report: Year 3. Volume II: Technical Narrative. 

U.S. Dept. of the Interior, Minerals Management Service, New Orleans, LA. OCS 

Study MMS 88-060. 586 pp.

Hubbard, G.F., R.L. Howard, and B.J. Gallaway. 1988. Loricifera, a recently described 

phylum occurring in the northern Gulf of Mexico. Northeast Gulf Science 10(1):49-

50.

Hurlbert, S.H. 1971. The nonconcept of species diversity: A critique and alternative 

parameters. Ecology. 52:577-586.

Kennicutt, M.C. II, J.L. Sericano, T.L. Wade, F. Alcazar, and J.M. Books. 1987. High 

molecular weight hydrocarbons in Gulf of Mexico continental slope sediments. 

Deep-Sea Res. 34(3):403-424.
37

Kristensen, R.M. 1983. Loricifera, a new phylum with aschelminthes characters from the 

meiobenthos. Zeitung fûr Zoologische Systematik und Evolutionsforschung 21:163-

180.

Lacerda, C.P., M.C. Kennicutt II, and J.M. Brooks. 1987. The distribution of

dibenzothiophens in the Gulf of Mexico sediments. Applied Geochemistry. 

2(3):297-304. 

Maciolek-Blake, N., P.D. Boehm, B. Hecker, J.F. Grassle, D. McGrath, A.G. Requejo, B. 

Brown, C.M. Cetta, D. Dade, S. Freitas, and R. Petrecca. 1985. Study of biological 

processes on the U.S. mid-Atlantic slope and rise: First interim report. Prepared for 

U.S. Dept. of the Interior, Minerals Management Service. 99 pp. + appendices.

Maciolek, N., B. Hecker, C.A. Butman, J.F. Grassle, W.B. Dade, P.D. Boehm, W.G. 

Steinhauer, V. Starczk, E. Baptiste, R.E. Ruff, and B. Brown. 1986. Study of

biological processes on the U.S. North Atlantic slope and rise. U.S. Dept. of the 

Interior, Minerals Management Service. MMS 86-0022. 201 pp. + appendices. 

Musick, J.J. 1976. Community structure of fishes on the continental slope and rise off the 

middle Atlantic Coast. U.S. Joint Oceanographic Assembly, Edinburgh. 

Pequegnat, W.E. 1983. The ecological communities of the continental slope and adjacent 

regimes of the northern Gulf of Mexico. Report to the U.S. Dept. of the Interior, 

Minerals Management Service, Metairie, LA, by TerEco Corporation, College 

Station, TX. 398 pp. + appendices.

Pequegnat, W.E., B.J. Gallaway, and L.H. Pequegnat. 1990. Aspects of the ecology of the 

deepwater fauna of the Gulf of Mexico. American Zoologist 30: 45-64. 

Rowe, G.T. 1971. Benthic biomass and surface productivity. Pages 441-454 in J.D. 

Costlow, Jr. (ed.). Fertility of the Sea, Vol. 2. Gordon and Breach, New York.

Rowe, G.T., P.T. Polloni, and S.G. Horner. 1974. Benthic biomass estimates from the 

northwestern Atlantic Ocean and the northern Gulf of Mexico. Deep-Sea Res. 

21:641-650.

Sanders, H.L. 1968. Marine benthic diversity: A comparative study. Amer. Nat. 102:243-

282.

Smith, W.L. and J.F. Grassle. 1977. Sampling properties of a family of diversity

measures. Biometrics. 33:283-291.

Thiel, H. 1983. Meiobenthos and nanobenthos of the deep sea. Pages 167-230 in G.T. 

Rowe (ed.). Deep-Sea Biology, Chapter 5. John Wiley & Sons, New York. 560 pp.
38

 Tietjen, J.H. 1971. Ecology and distribution of deep-sea meiobenthos off North Carolina. 

Deep-Sea Res. 18:941-954.

Wigley, R.L. and A.D. McIntyre. 1964. Some quantitative comparisons of offshore 

meiobenthos and macrobenthos south of Martha’s Vineyard. Limnol. Oceanogr. 

9:485-493.
39

APPENDIX 1

SUMMARY OF TRAWLING EFFORT
40
41

APPENDIX 1. SUMMARY OF TRAWLING EFFORT

CRUISE I - MMS-NGOMCS TRAWL STATIONS, NOVEMBER 1983

Depth On-Bottom Position Duration

Station (m) N. Lat (Deg.). W. Long. (Deg.) (Hrs:Min) Remarks QA

C-1 329 28.044 90.175 1:09 5 containers (2 fish, 3 invertebrates) (1)

C-2 786 27.533 90.053 1:14 All fish (except ophidiids) kept for HC (1)

C-3 850 27.480 90.033 2:30 3 buckets and 3 jars (1)

C-4 1440 27.254 89.476 1:21 Small catch (trawl bridge twisted) (2)

C-5 2400 26.565 89.332 5:19 Trawl malfunctioned, minimal catch (2)

1Quantitative

2Non-quantitative

CRUISE II - MMS-NGOMCS TRAWL STATIONS, 7-19 APRIL 1984 

Depth On-Bottom Position Duration

Station (m) N. Lat (Deg.). W. Long. (Deg.) (Hrs:Min) Remarks QA

W-1 342 27.370 93.336 1:08 5 gal. shell hash (dead clams) plus 1 (1)

bucket, 1 jar

W-2 576-732 27.245 93.189 1:02 1 bucket, 1 jar (1)

W-3 792-864 27.084 93.236 2:39 3 containers (1)

W-4 1372-1454 26.444 93.186 2:18 Palm fronds and sargassum (1 bucket (1)

of specimens

W-5 2322-2305 26.171 93.246 2:37 Port side door had turned over 1com- (2)

plete revolution. Both doors covered

with traces of mud. 2 containers: 1 

vial and 1 9-oz jar

C-1 329-347 28.033 90.150 1:05 2 buckets and 1 16-0z jar (1)

C-2 603 27.544 90.060 1:04 Many brittle stars (1 bucket and 1 gal. (1)

jar)

C-3 805 27.497 90.067 2:19 1 container (1)

C-4 1358-1518 27.281 89.436 2:00 2 1-gal jars (1)

C-5 2412-2390 27.014 89.303 2:16 Poor catch (1 gal. jar) (1)

E-1 375-358 28.265 86.031 1:17 Good catch (1)

E-2 603-640 28.176 86.148 0:59 Lazy line wrapped around cod end. 1 (2)

bucket

E-3 840 28.107 86.256 2:14 2 buckets (1)

E-4 1170 28.060 86.353 2:07 3 buckets (1)

E-5 2881-2834 28.019 86.401 2:12 Poor trawl--doors probably collapsed (2)

1Quantitative

2Non-quantitative
42

CRUISE III - MMS-NGOMCS TRAWL STATIONS, NOVEMBER-DECEMBER 1984 

Depth On-Bottom Position Duration

Station (m) N. Lat (Deg.). W. Long. (Deg.) (Hrs:Min) Remarks QA

C-1 366-326 28.023 90.148 1:03 No problems noted (1)

C-2 632 27.543 90.075 1:23 Counted and discarded 718 ophiuroids. (1)

3 buckets (2 fish, 1 invertebrate)

C-3 841-764 27.489 90.078 1:09 Fair trawl (sample in 3 buckets) (1)

C-4 1420-1600 27.277 89.455 2:00 Not many animals (low biomass). Lot (2)

of bottom debris (burnt coal-type 

material). 1 5-gal. Bucket

C-5 2486-2523 26.567 89.306 2:03 Good haul (1)

C-6 501-448 28.01 90.051 1:00 No problems noted (1)

C-7 896-1033 27.445 90.015 1:02 Due to sudden rise in bottom stopped (2)

wire out at 3289 m and turned vessel

to 045 deg. At 1001 hrs. turned to 090

deg. as bottom still rising (outside 

acceptable range)

C-8 1064 27.311 89.489 1:34 Greatest variety so far; baby giant squid, (1)

pteropods, shrimp, fish, benthosaurus

C-9 1309-1317 27.295 89.479 0:50 Large mud ball. Trawl anchored vessel (2)

C-10 1680-1790 27.25 89.422 2:02 Lots of mud--2.5 tons. Not much biota-- (2)

probably some lost with mud lumps

(clays)

C-11 2085-2063 27.137 89.368 2:00 Lots of trash--terrigenous material, sar- (2)

gassum, rocks, starfish. 1 5-gal bucket

C-12 - - - - Gear problems, no trawl (2)

1Quantitative

2Non-quantitative
43

CRUISE IV - MMS-NGOMCS TRAWL STATIONS, MAY 1985

Depth On-Bottom Position Duration

Station (m) N. Lat (Deg.). W. Long. (Deg.) (Hrs:Min) Remarks QA

E-1 351-357 28.448 86.042 1:00 4 buckets, good tow (1)

E-1a 351-351 28.906 86.407 0:55 3 buckets, good tow (1)

E-1b 346-344 28.311 85.739 0:58 2 buckets plus 1 gallon (1)

E-1c 353-347 28.219 85.566 0:58 High shrimp catch, many fish (1)

E-2 613-618 28.268 86.201 1:00 Good catches (1)

E-2a 625-625 28.584 86.762 1:35 7 buckets + 2 gal. Containers (1)

E-2b 625-600 28.316 86.316 0:59 4 buckets (1)

E-2c 620-616 28.226 86.111 0:59 No problems noted (1)

E-2d 624-631 28.127 85.860 1:00 7 buckets, rocks and wood (1)

E-2e 629-629 28.018 85.661 1:00 2 buckets, no problems (1)

E-3 871-871 28.160 86.399 1:00 1 bucket, no problems (1)

E-3a 841-783 28.499 86.969 0:44 4 buckets (1)

E-3b 845-823 28.119 86.286 1:00 3 buckets (1)

E-3c 838-847 28.267 86.604 1:07 No problems noted (1)

E-3d 845-856 28.373 86.808 1:01 No problems noted (1)

E-5 - - - Gear problems, no trawl (2)

WC-5 402-444 27.784 91.729 1:00 No problems noted (1)

WC-8 486-472 27.862 90.764 1:04 6 buckets (1)

WC-9 807-695 27.713 91.255 0:59 4 buckets (1)

1Quantitative

2Non-quantitative
44

CRUISE V - MMS-NGOMCS TRAWL STATIONS, JUNE 1985

Depth On-Bottom Position Duration

Station (m) N. Lat (Deg.). W. Long. (Deg.) (Hrs:Min) Remarks QA

WC-1 344-393 27.716 92.868 0:45 Net clogged with sargassum, not on

bottom long, irregular bottom (2)

WC-2 518-585 27.752 92.483 1:00 2 buckets (1)

WC-3 781-768 27.587 92.378 0:59 Bridle twisted nearly to doors, doors (2)

only open to 3 m on retrieval

WC-4 527-516 27.719 92.154 0:58 2 buckets (1)

WC-6 543-783 27.712 91.549 1:06 12 buckets, coral reef fauna (1)

WC-7 457-472 27.759 91.227 1:00 Noted as rope & worm station, strong (1)

current

WC-10 741-752 27.755 90.800 1:00 Tow too fast; not enough scope, meager (2)

catch

WC-11 1247-1024 27.412 92.634 1:00 4 buckets (1)

WC-12 1236-1170 27.327 91.522 1:00 No problems noted (1)

1Quantitative

2Non-quantitative
The Department of the Interior Mission

As the Nation's principal conservation agency, the Department of the Interior has responsibility

for most of our nationally owned public lands and natural resources. This includes fostering

sound use of our land and water resources; protecting our fish, wildlife, and biological diversity;

preserving the environmental and cultural values of our national parks and historical places;

and providing for the enjoyment of life through outdoor recreation. The Department assesses

our energy and mineral resources and works to ensure that their development is in the best

interests of all our people by encouraging stewardship and citizen participation in their care.

The Department also has a major responsibility for American Indian reservation communities

and for people who live in island territories under U.S. administration.

The Minerals Management Service Mission

As a bureau of the Department of the Interior, the Minerals Management Service's (MMS)

primary responsibilities are to manage the mineral resources located on the Nation's Outer

Continental Shelf (OCS), collect revenue from the Federal OCS and onshore Federal and Indian

lands, and distribute those revenues.

Moreover, in working to meet its responsibilities, the Offshore Minerals Management Program

administers the OCS competitive leasing program and oversees the safe and environmentally

sound exploration and production of our Nation's offshore natural gas, oil and other mineral

resources. The MMS Minerals Revenue Management meets its responsibilities by ensuring the

efficient, timely and accurate collection and disbursement of revenue from mineral leasing and

production due to Indian tribes and allottees, States and the U.S. Treasury.

The MMS strives to fulfill its responsibilities through the general guiding principles of: (1) being

responsive to the public's concerns and interests by maintaining a dialogue with all potentially

affected parties and (2) carrying out its programs with an emphasis on working to enhance the

quality of life for all Americans by lending MMS assistance and expertise to economic 

development and environmental protection.