ACCESS NUMBER: 30619

STUDY TITLE: Distribution and Abundance of Cetaceans in the North-Central and 

Western Gulf of Mexico 

REPORT TITLE: Distribution and Abundance of Cetaceans in the North-Central and 

Western Gulf of Mexico, Final Report, Volume I: Executive Summary, Volume II: 

Technical Report, Volume III: Appendix A, Volume III: Appendix B, Volume III: 

Appendix C, Part 1, and Volume III: Appendix C, Part 2 

CONTRACT NUMBER: 14-35-0001-30619; IA 16197 

SPONSORING OCS REGION: Gulf of Mexico 

APPLICABLE PLANNING AREAS: Central and Western Gulf of Mexico 

FISCAL YEAR(S) OF PROJECT FUNDING: 1992-1994 

COMPLETION DATE OF REPORT: May 1996 

COSTS: FY 1992: $1,105,700; FY 1993: $1,136,575; FY 1994: $924,841 

CUMULATIVE PROJECT COST: $3,167,116 

PROGRAM MANAGER: Randall W. Davis 

AFFILIATION: Texas A&M University at Galveston 

ADDRESS: Marine Biology Department, P.O. Box 1675, Galveston, Texas 77553 

PRINCIPAL INVESTIGATORS*: G. Scott, B. Würsig, G. Fargion, W. Evans, R. 

Benson, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate 

KEY WORDS: North-central and western Gulf of Mexico; marine mammals; cetaceans; 

distribution; abundance; density; bioacoustics; hydrography; satellite tagging; aerial 

surveys; shipboard surveys 

BACKGROUND: The Minerals Management Service (MMS) has the responsibility to 

assure that oil and gas operations on the continental slope in the Gulf of Mexico are 

conducted in a manner that reduces risks to the marine environment. To meet their 

responsibilities under the Marine Mammal Protection Act of 1972 and the Endangered 

Species Act of 1973, the MMS must understand the effects of oil and gas operations on 

marine mammals. MMS Section 7 consultation with the National Marine Fisheries 

Service identified a need for knowledge of marine mammals in deep waters of the Gulf. 

This program was designed to meet these needs. 
ACCESS NUMBER: 30619

OBJECTIVES: The purpose of this study (hereafter called GulfCet) was to determine 

the distribution and abundance of cetaceans in the areas potentially affected by future 

oil and gas activities along the continental slope in the north-central and western GOM. 

DESCRIPTION: The GulfCet Program was a 3.75 year project (1 October 1991 through 

15 July 1995). The study was restricted to the area bounded by the Florida-Alabama 

border, the Texas-Mexico border, and the 100- and 2,000-m isobaths. A major part of 

the GulfCet Program’s field research consisted of seasonal, line transect surveys to 

determine the distribution and abundance of cetaceans in the study aircraft, 2) visual 

surveys from ships, and 3) acoustic surveys using a linear hydrophone array towed 

behind a visual survey ship. The hydrographic portion of the program was designed to 

sample to meso-to-large scale features in conjunction with remote sensing. Finally, 

tagging and tracking of sperm whales using satellite telemetry was attempted. Sperm 

whales were successfully tracked by passive acoustic means. 

SIGNIFICANT CONCLUSIONS: Cetaceans were sighted throughout the length of 

study area at all water depths. However, distinct species were found at specific water 

depths. Atlantic spotted dolphins were sighted primarily near the shelf edge (mean = 

197 m), while bottlenose dolphins were observed in somewhat deeper water (mean = 

294m). Risso’s dolphins, short-finned pilot whales, pygmy/dwarf sperm whales, roughtoothed dolphins spinner dolphins, sperm whales, striped dolphins, Mesoplodon spp., 

pantropical spotted dolphins, clymene dolphins, and beaked whales were found in much 

deeper water (mean = 700-1,300 m). Several poorly known species turned out to be 

moderately common (beaked whales, pygmy and dwarf sperm whales, melon-headed 

whales, Fraser’s and clymene dolphins). Both melon-headed whales and Fraser’s 

dolphins were almost completely unknown in the Gulf of Mexico before this study 

began. 

STUDY RESULTS: A total of 351 cetacean groups representing 17 species were 

sighted on-effort during eight aerial surveys. Sperm whales, pygmy/dwarf sperm 

whales, bottlenose dolphins, Risso’s dolphins, and pantropical spotted dolphins were 

the most commonly sighted species. A total of 683 shipboard marine mammal sightings 

of at least 19 species were made during the eleven ship surveys. Pantropical spotted 

dolphins and bottlenose dolphins were the most common small cetaceans and sperm 

whales were the most common large cetacean seen by ship. Marine mammals acoustic 

contacts totaled 487. Of that number, 124 contacts were recorded, representing 12 

species. Sperm whales were the most commonly recorded species, accounting for 56% 

of identified contacts. The majority of the sperm whale acoustic contacts have been off 

the mouth of the Mississippi River and on the western side of the study area. During 

the GulfCet cruises, several anticyclonic (warm core) eddies (Trinton, Unchained, 

Vazquez, Whopper, and Extra) were detected. Small cyclonic (cold water) eddies have 

often been observed in association with the periphery of these dominant features. 

These are generally areas of higher chlorophyll concentration, and are therefore 

indicative of increased primary productivity. 
ACCESS NUMBER: 30619

STUDY PRODUCTS: Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, 

R. Benson, K. Mullin, N. May, T. Leming, B. Mate, J. Norris, and T. Jefferson. 1994. 

Distribution and abundance of marine mammals in the north-central and western Gulf of 

Mexico: Interim Report prepared in two volumes by the Texas Institute of Oceanography 

and the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals mgmt. 

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

Volume I. Technical Report, 131 pp. OCS Study MMS 94-0003. 

Volume II. Appendix, 813 pp. OCS Study MMS 94-0004. 

Davis, R.W., and G. S. Fargion, eds. 1996. Distribution and abundance of cetaceans in 

the north-central and western Gulf of Mexico: Final report prepared in three volumes by 

the Texas Institute of Oceanography and the National Marine Fisheries Service. U.S. 

Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico OCS Region, New 

Orleans, LA. 

Volume I. Executive summary, 29 pp. OCS Study MMS 96-0026. 

Volume II. Technical Report, 357 pp. OCS Study MMS 96-0027. 

Volume III. Appendix A-C. OCS Study MMS 96-0028. 

 Appendix A, 419 pp. 

 Appendix B, 501 pp. 

 Appendix C Part 1, 561 pp. 

 Appendix C Part 2, 489 pp. 

*P.I.'s affiliation may be different than that listed for Program Managers.