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TECHNICAL SUMMARY

STUDY TITLE: Explosive Removal of Structures: Fisheries Impact Assessment

REPORT TITLE: Explosive removal of structures: fisheries impact assessment

CONTRACT NUMBER: M16PC00005

SPONSORING OCS REGION: Gulf of Mexico New Orleans Office

APPLICABLE PLANNING AREA(S): Gulf of Mexico

FISCAL YEAR(S) OF PROJECT FUNDING: FY 2016: $166,314; FY 2017: $609,816; FY2018: 

$1,496,823; FY 2019: $332,628; FY 2020: $720,692

COMPLETION DATE OF REPORT: December 2019

CUMULATIVE COSTS: $3,326,273

PROJECT MANAGER(S): Benny J. Gallaway

AFFILIATION of Project manager: LGL Ecological Research Associates, Inc.

ADDRESS: 4103 S. Texas Avenue, Suite 2011, Bryan, TX. 77802-4043

PRINCIPAL INVESTIGATOR(S)*

: Steven Szedlmayer, Brad Erisman, Katherine Kim

KEY WORDS: Gulf of Mexico, offshore oil and gas structures, explosive removal, assemblage 

characterizations, red snapper, vermilion snapper, greater amberjack, gray triggerfish, cobia

BRIEF ABSTRACT: The US Department of the Interior, Bureau of Ocean Energy Management (BOEM) 

perceived the need for updated activities of the impacts from explosive severance decommissioning 

Activities on fish and fisheries. The study was conducted to provide this update and consisted of 

comprehensive literature synthesis, field studies and modeling assessments to determine the impacts of 

explosive removals of offshore platforms on fish and fisheries. With one exception, effects on federallymanaged fish stocks of commercial and recreational importance did not appear to be of major concern, 

given that on the order of only 5 to 8% of the total stocks occurred on platforms. The exception was 

greater amberjack where about 48% of the total stock appears to occur on platforms.The effects on 

fisheries may be more significant especially on a localized basis. For example, offshore western 

Louisiana, offshore platforms constitute 72% of the known reef habitats.

BACKGROUND: The number of offshore oil and gas platforms increased steadily from the mid-1960s to 

the early 1990s. The total number of these structures exhibited a markedly slower growth rate from the 

early 1990s to about 2007 when the net numbers began a steep decline. The net decline is explained by 

platform removals, particularly those removals made using explosives. Given that many recreationallyand-commercially valuable fish were associated with these structure, concern about the impacts of these 

removals prompted this study.

OBJECTIVES: The overarching goal of this study was to determine the impacts on federally-managed 

commercial and recreational fish and fisheries resulting from explosive severance decommissioning 

activities on the Outer Continental Shelf. The objectives were to 1) conduct a literature synthesis on 

platform associated fish and fisheries and on the types of available acoustic models and the best of these 

to use for determining the effects of underwater explosives; 2) conduct field studies to determine the 
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types and numbers of recreationally- and commercially- valuable fish using platforms as habitats; 3) 

determine the numbers of fish killed in explosive removal events and determine the impacts of the actual 

and total removals of platforms on the fish stocks and fisheries.

DESCRIPTION: Existing literature was compiled using Thomson Reuters EndNoteTM version X7.7 

bibliographic software and the UnderWater Calculator (UWC Version 1) was selected as the best acoustic 

model for determining impacts of underwater explosions. Platform fish communities were quantified using 

hydroacoustic survey methods supplemented with submerged rotating video (SRV) camera surveys to 

apportion abundance to species levels. Telemetry studies were used to determine the proportion of time 

red snapper would be in the lethal blast radius, and mark and/or recapture studies were conducted as an 

independent measure of abundance for red snapper. Age, condition and growth data were also collected 

to characterize red snapper using platform habitats.

SIGNIFICANT CONCLUSIONS: An array of recreationally and commercially valuable, federally-managed 

reef fish species aggregate to varying degrees around offshore oil and gas platforms. On a gulfwide 

basis, these aggregations typically represent small fractions of the overall stocks. However, there appears 

to be at least one potential exception. On the order of 48% of the greater amberjack stock is associated 

with offshore oil and gas platforms, mainly platforms offshore Western Louisiana. Few, if any, fish that 

aggregate around platforms survive explosive platform removal.

STUDY RESULTS: Results were based on a stratified random sample of 60 offshore platforms. All 

planned samples were obtained over three field seasons and the sampling programs were 100% 

completed within the planned schedule. Five federally-managed species were evaluated, namely red 

snapper, vermilion snapper, gray triggerfish, greater amberjack and cobia. With the exception of greater 

amberjack (48% of the stock occurred on platforms), a small percentage of the overall stocks (<10%) 

occurred on platforms, and therefore the effects of explosive removals on total fish stocks were predicted 

to be low. However, localized, or regional effects were suggested for fisheries in some areas which are 

focused on platforms. Platforms are targeted because there does not appear to be much in the way of 

alternative natural habitats or other artificial reef habitats.

STUDY PRODUCT(S):

1. Report: 

Gallaway BJ, Rabon S, McCain K, Beyea T, Default S, Conrad A, Kim K. 2020. Explosive removal 

of structures: fisheries impact assessment. New Orleans (LA): US Department of the 

Interior, Bureau of Ocean Energy Management. 149 p. Contract No.: M16PC00005. 

Report No.: OCS Study BOEM 2020-038. 

2. EndnoteTM database
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MAP SHOWING AREA OF STUDY 

(Figure 1 of report OCS Study BOEM 2020-xxx)

Figure 1. The distribution of standing platforms by year, private recreational Red Snapper 

state management area and depth zone. All marked platforms were in place when the 

study commenced in 2017 and those marked in red were removed by 2018.

*

P.I.’s affiliation may be different than that listed for Project Manager(s).