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TECHNICAL SUMMARY

Study Title: Analysis of Fish Populations at Platforms off Summerland, California

Report Title: Analysis of Fish Populations at Platforms off Summerland, California

Contract Number: M12AC00004

Sponsoring OCS Region: Pacific

Applicable Planning Area: Southern California

Fiscal Years of Project Funding: 2012; 2013; 2014

Completion Date of the Report: September 2015

Costs: FY 2012: $250,000; FY 2013: 350,000; FY 2014: 25,000

Cumulative Project Cost: $625,000

Project Manager: Milton Love

Affiliation: University of California, Santa Barbara; Marine Science Institute

Address: Santa Barbara, CA 93106

Principal Investigator: Milton Love

Key Words: oil platforms, platforms, California oil platforms, rockfishes, decommissioning, platform decommissioning

Background and Objectives

The BOEM defines decommissioning as the process of ending oil, gas, or sulfur requirements of the regulations. The BOEM works to ensure that wells are plugged to prevent pollution; that pipelines are decommissioned and sometimes removed to prevent seepage of hydrocarbons and to resolve conflicts with other uses 

of the OCS; and that all sites are cleared of obstructions to minimize use conflicts. The BOEM will conduct 

detailed environmental reviews of any proposed decommissioning projects to evaluate the impacts from 

platform removal on regional fish populations. Obviously, when a platform is disassembled, habitat is removed, and numerous fishes and invertebrates are killed.

The fate of spent offshore platforms off California has been a subject of considerable debate, much of which 

is focused on the potential importance of fish populations residing at these facilities. These platforms contribute considerable hard structure habitat for marine fishes; providing both a food source and complex 

physical habitat for fishes in an area that would otherwise be void of such associated fauna. In addition, recent research has shown that oil and gas platforms off the coast of California have the highest secondary fish 

production per unit area of seafloor of any marine habitat that has been studied (Claisse et al. 2014). The 

majority of species found on California platforms are rockfishes but include many other groups of fishes 

including some not well represented on nearby natural reefs or in coastal kelp beds. 

The role that each California platform may play as fish habitat must be seen in light of the Secretary of the 

Department of Commerce’s 2000 declaration designating the West Coast groundfish fishery a disaster with 

extremely small populations remaining. Recent BOEM-funded studies (Love et al. 2005, Love and York 

2006, Nishimoto and Love 2011) have revealed that some of the platforms hold large numbers of both 

juvenile and reproductively mature rockfishes in numbers far greater than any natural reef that has been 

surveyed. The observed rockfish species include bocaccio and cowcod, both of which are species of concern, 

with bocaccio once considered for listing as threatened under the Endangered Species Act. Additionally, 

four more federally declared overfished species have been observed, sometimes in large numbers, at some 

platforms: canary, darkblotched, widow and yelloweye rockfishes. All of these species are subject to federal 

rebuilding plans, as specified by the Magnuson-Stevens Fishery Conservation Act. The Pacific Fishery Man-
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agement Council and the State of California began to severely restrict targeted fishing for these species in 

2002 and 2003 and created the Cowcod Conservation Area in southern California to protect that species. 

Since 2001, cowcod have been managed as a no-retention fishery in California. In addition, the State of 

California banned the spot prawn trawl fishery in order to eliminate all by-catch of bocaccio. Populations 

of rockfishes at platforms, and the platforms as habitat for specific life history stages (e.g., nursery habitat 

for juveniles), may prove to be vital for timely recovery of the regional rockfish populations and fisheries. 

However, yet unknown are the impacts of platform removal on regional populations of coastal organisms, 

particularly the economically important rockfish species, on the Pacific OCS.

The assessment of the effects of platform activities and of the habitat created by the structure of platforms 

on marine populations greatly bears upon decommissioning issues, as questions about Essential Fish Habitat and the ecological role of Pacific OCS platforms are still unresolved.

Pacific OCS platforms reside in a variety of depths and oceanographic conditions (Love et al. 2003) and 

there are large differences in fish assemblages between platforms (Love et al. 2003, Love and York 2006, 

Nishimoto and Love 2011). Thus, this assemblage variability suggests that a case-by-case scenario is likely 

for decommissioning decisions. In order to analyze the environmental consequences of platform decommissioning on local or regional fish populations, it is essential to know the role that each platform plays as 

fish habitat. Data gaps concerning the fish assemblages exist at some of the oldest facilities, yet these facilities 

may be the first to be decommissioned. Knowledge of the potential importance of the local population at 

platforms to the depleted Pacific rockfish stocks is essential for fully evaluating the various options proposed 

for decommissioning California’s offshore oil platforms.

The eight platforms within the Dos Cuadras oil field, off Summerland, California (C, B, A, Hillhouse, Henry, 

Houchin, Hogan, and Habitat) have been in operation for over four decades and are expected to be some of 

the first to be in line for decommissioning. Problematically, these structures are situated in a depositional, 

and hence turbid-water, region. In practice, this has meant that, despite a number of attempts over 15 years, 

water visibility at the bottom of the platform jackets has been judged by the pilots of manned submersibles 

too poor to safely allow assessment of fish assemblages. However, a review of segments of a remotely operated vehicle (ROV) survey of one of these platforms indicated that fish populations at these platform habitats could be adequately surveyed using a combination of SCUBA and ROV techniques. 

Information is needed as soon as possible for the use by the State of California to consider for decommissioning options under the California legislation AB 2503 (the California Marine Resources Legacy Act). The 

Act requires California to consider reefing OCS oil and gas platforms, if their ecological value warrants, 

before decommissioning and potential removal. BOEM can specify requirements to industry or other interested parties when decommissioning occurs. Using the results, BOEM can ensure that specified criteria 

can be properly evaluated during the decommissioning process pursuant to the federal regulations at 30 

CFR 250.1730 and the State of California can ensure proper evaluation under the California Rigs-to-Reefs 

Program law AB 2503 (the California Marine Resources Legacy Act).

The primary goals of this research were:

1) To make a more detailed assessment of the fish assemblages of these eight platforms (and by extension a more accurate picture of their ecological importance) than is currently available and

2) To compare these assemblages with some other platforms in the Santa Barbara Channel.
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Literature Cited

Claisse, J. T., D. J. Pondella II, M. Love, L. A. Zahn, C. M. Williams, J. P. Williams, and A. S. Bull. 2014. Oil 

platforms off California are among the most productive marine fish habitats globally. Proc. Nat. Acad. 

Sci. 111:15462–15467.

Love, M. S. and A. York. 2006. The relationships between fish assemblages and the amount of bottom horizontal beam exposed at California oil platforms: fish habitat preferences at man-made platforms and 

(by inference) at natural reefs. Fish. Bull. 104:542–549.

Love, M. S., D. M. Schroeder, M. M. Nishimoto. 2003. The ecological role of natural reefs and oil and gas 

production platforms on rocky reef fishes in southern California: A synthesis of information. U. S. Geological Survey, OCS Study MMS 2003-032.

Love, M. S., D. M. Schroeder, and W. H. Lenarz. 2005. Distribution of bocaccio (Sebastes paucispinis) and 

cowcod (Sebastes levis) around oil Platforms and natural outcrops off California with implications for 

larval production. Bull. Mar. Sci. 77:397–408.

Nishimoto, M. M. and M. S. Love. 2011. Spatial and seasonal variation in the biomass and size distribution 

of juvenile fishes associated with a petroleum platforms off the California coast, 2008–2010. BOEMRE 

OCS Study 2011-08. Marine Science Institute, University of California, Santa Barbara, California. MMS 

Cooperative Agreement no. M08AX12732.

Description

We conducted fish assemblage surveys around the midwaters, bottoms, and shell mounds of eight oil and 

gas platforms (A, B, C, Habitat, Henry, Hillhouse, Hogan, and Houchin) off Summerland, California. We 

conducted scuba surveys in the upper 39 m of the water column, from June–September of 2012 and 2013. 

Deeper midwaters, bottoms, and shell mounds were surveyed with a remotely operated vehicle.

Significant Results

We conducted 57 transects around eight platforms encompassing 34,389 m2 of habitat. Over all platforms, 

we observed 108,303 individual fish, comprising a minimum of 46 species. Rockfishes, of at least 22 species, were most characteristic of all of the assemblages; we observed 105,114 individual rockfishes and this 

represented 97.1% of all fishes recorded. Rockfishes comprised between 76.8% (shell mounds) and 98.3% 

(midwaters) of all fishes observed. In particular, YOY rockfishes comprised most of the midwater fish assemblage (94.7% of all fishes observed) and about 20% of the bottom and shell mound assemblages (21.1% 

and 22.9%, respectively). Of the top ten species ranked by density, all were rockfishes and seven of these taxa 

were YOY stages. Of particular importance were squarespot, blue, shortbelly, widow, and halfbanded rockfishes, and bocaccio. Among non-rockfish species, lingcod, senorita, painted greenling, shortspine combfish, 

and blacksmith comprised at least one percent of the assemblages as measured by density.

Around platform bottoms, we conducted 29 transects, covering 4,792 m2

. A total of 5,193 fish (a minimum 

of 34 species) were observed. Rockfishes, of a minimum of 19 species and totaling 4,359 individuals (83.9% 

of all fishes observed) dominated the assemblages. About 25% of all fishes observed were YOY rockfishes 

(1,098 of 4,359). The bottom fish assemblages were fairly similar across all platforms and most different at 

the deepest (Habitat) and shallowest (Hogan) structures. 

There was a tendency for the mid-depth platforms to harbor the highest number of species; a high of 26 was 

observed at Platform B and a low of 12 was seen at Hogan. On the other hand, the overall density of fishes at 
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various platform bottoms did not vary statistically with bottom depth because at most platforms overall fish 

density varied greatly between years. This was due primarily to substantial interannual differences in densities linked to quite variable recruitment of YOY squarespot, shortbelly, halfbanded, and calico rockfishes 

and California lizardfish, as well as changes in densities of somewhat older juvenile squarespot, vermilion, 

and blue rockfishes and bocaccio. Most of the fishes we observed around platform bottoms were relatively 

small, about 70% were 15 cm or less. These fishes were either juvenile fishes (e.g., calico, copper, halfbanded, 

squarespot, and vermilion rockfishes, bocaccio, and lingcod) or were dwarf species such as halfbanded and 

calico rockfishes. 

We conducted 28 transects on the shell mounds and these transects covered 4,433 m2

. A total of 2,822 fishes, 

of at least 32 species, were observed. As with the platform bottoms, rockfishes (2,168 individuals of at least 

16 species) again dominated the species assemblage; they comprised 76.8% of all fishes observed. Almost 

30% of all fishes observed were YOY rockfishes (646 of 2,168). While shell mound fish assemblages were 

similar across all platforms, we observed relatively small differences between the deeper platforms Habitat, 

A, and B, and the rest of the structures. However, there was no evidence that the shell mound assemblage of 

any platform was unique.

The shell mound around Platform B was the most species rich (22 taxa) and that around Habitat (11 species), Henry (11 species), and Hogan (10 species) harbored the fewest taxa. Similar to our observation 

around platform bottoms, a substantial inter-annual variation in fish densities at several platforms made 

it difficult to determine if densities varied among platforms. Species that exhibited large interannual differences in densities included calico, halfbanded, shortbelly and squarespot rockfishes YOYs, blue, calico, 

halfbanded and vermilion rockfishes and California lizardfish. Again, as with platform bottoms, small fishes 

(of 20 cm or less) were by far most abundant in this habitat at all platforms. Species that characterized this 

habitat included calico, halfbanded, squarespot, and vermilion rockfishes, as well as California lizardfish, 

lingcod (particularly YOYs) and painted greenling. 

We observed a total of 100,287 fishes in platform midwaters, composed of at least 28 species. Of these fishes, 

98,587 (98.3% of the total) were rockfishes (of 17 species), and 96.4% of these were YOYs. YOY rockfishes 

dominated this habitat and comprised 94.7% of all fishes observed. Densities of five rockfish species (i.e., 

blue, bocaccio, shortbelly, squarespot, and widow) greatly exceeded those of other taxa. 

We observed between 27 (Platform B) and 14 (Platform Henry) species in the midwaters of eight platforms. 

No pattern in species richness among the platforms was observed. Around most platforms, fish densities 

varied greatly between years and this variability was due to very large interannual differences in YOY recruitment of blue, shortbelly, squarespot, and widow rockfishes, bocaccio and blacksmith. Midwater fish 

assemblages around these eight platforms were fairly similar – perhaps the greatest differences were withinplatform interannual ones driven by this recruitment variability. The overwhelming importance of YOY 

rockfishes in this habitat explains our observations that almost all of the fishes observed in the platform 

midwaters were small, 10 cm or less long. 

We compared the bottom and shell mound assemblages of the Summerland platforms with previous findings from Platforms Holly and Gilda; these structures are located within the Santa Barbara Channel and are 

in similar bottom depths. We found that the Summerland fish assemblages are closely related to these two 

other platforms. Given that the Summerland platforms are arguably in some of the most turbid waters of 

any California platforms, the implication is that bottom turbidity plays less of a role in structuring fish assemblages as do other habitat characteristics such as bottom depth.
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Overall, the data from 2012–2013 found that: 

1) The fish assemblages found around the Summerland platforms are similar to those around other 

platforms situated in the same bottom depths in the Santa Barbara Channel (i.e., Holly and Gilda); 

2) There is substantial overlap in the species living in the midwaters, bottoms, and shell mounds on 

many, if not all, of these relatively shallow water platforms. This is at least partially due to a suite of 

rockfish species that recruit as YOYs to platform midwaters and are then able to occupy both midwater and bottom depths; 

3) Based on the high densities of juveniles, one of the major functions of the Summerland platforms is 

as a nursery ground for a suite of species, primarily rockfishes but also including lingcod and painted 

greenling. Adult fishes (e.g., blacksmith, cabezon, garibaldi, and sheephead) are present, sometimes 

in substantial numbers, but juvenile rockfish dominance relegates these other species to a relatively 

small fraction of the total fish population. 

4) The densities of fishes in the midwaters of most California platforms vary greatly between years, 

regardless of platform bottom depth, because juvenile rockfish recruitment varies (sometimes dramatically) between years (Nishimoto and Love 2011). At many shallower platforms (such as those 

off Summerland) the three habitat assemblages, which share a variety of juvenile rockfish species, are 

linked and thus fish densities at all depths and habitats may vary greatly interannually.