FISH ASSEMBLAGES ASSOCIATED 

WITH PLATFORMS AND NATURAL REEFS 

IN AREAS WHERE DATA ARE 

NON-EXISTENT OR LIMITED 

OCS Study

BOEMRE Study 2010-012

Pacific Outer Continental Shelf Region

FISH ASSEMBLAGES ASSOCIATED 

WITH PLATFORMS AND NATURAL REEFS 

IN AREAS WHERE DATA ARE 

NON-EXISTENT OR LIMITED

Authored by: 

Milton S. Love 

Mary Nishimoto 

Donna Schroeder

Submitted by:

Marine Science Institute 

University of California 

Santa Barbara, CA 93106

Prepared under:

MMS Cooperative Agreement No.: 1435-01-05-CA-39322; NSL-PC-05-01 and

MMS Cooperative Agreement No.: M07AC13380; NSL-PC-07-04

U.S. Department of Interior

Bureau of Ocean Energy Management, Regulation and Enforcement

Pacific OCS Region

Camarillo, CA, 93010 August 2010
Disclaimer

This report had been reviewed by the Pacific Outer Continental Shelf Region, Bureau of Ocean Energy 

Management, Regulation and Enforcement, U. S. Department of Interior and approved for publication. 

The opinions, findings, conclusions, or recom¬mendations in this report are those of the authors, and 

do not necessarily reflect the views and policies of the Bureau of Ocean Energy Management, Regulation 

and Enforcement. Mention of trade names or commercial products does not constitute an endorsement 

or recommendation for use. This report has not been edited for conformity with Bureau of Ocean Energy 

Management, Regulation and Enforcement editorial standards.

Availability

Available for viewing and in PDF at: 

www.lovelab.id.ucsb.edu

Bureau of Ocean Energy Management, Regulation and Enforcement

Pacific OCS Region 770 Paseo Camarillo 

Camarillo, CA 93010 

805-389-7621

Milton Love

Marine Science Institute

University of California

Santa Barbara, CA 93106

805-893-2935

Suggested Citation

Love, M. S., M. M. Nishimoto, and D. M. Schroeder. 2010. Fish Assemblages Associated with Platforms 

and Natural Reefs in Areas Where Data Are Non-Existent or Limited. BOEMRE OCS Study 2010-012. 

Marine Science Institute, University of California, Santa Barbara, California. MMS Cooperative Agreement No.: 1435-01-05-CA-39322; NSL-PC-05-01 and MMS Cooperative Agreement No.: M07AC13380; 

NSL-PC-07-04.
TABLE OF CONTENTS

Technical Summary i-iv

Study Products v-vi

Executive Summary vii-xi

Task 1 1-71

Fish Assemblages at Central and Southern California Oil Platforms 

and Natural Sites: 2004–2009

Task 2 72-86

A Comparison of Fish Assemblages in the Midwaters of Two 

California Oil and Gas Platforms
i

TECHNICAL SUMMARY

Study Title: Fish Assemblages Associated with Platforms and Natural Reefs in Areas Where Data are NonExistent or Limited

Report Title: Fish Assemblages Associated with Platforms and Natural Reefs in Areas Where Data are NonExistent or Limited

Contract Numbers: 1435-01-05-CA39322 and M05AC12299

Sponsoring OCS Region: Pacific

Applicable Planning Area: Central and Southern California

Fiscal Years of Project Funding: 2005–2010

Completion Date of the Report: August 2010

Costs: $1,280,000

Cumulative Project Cost: $1,280,000

Principal Investigator: Milton Love

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

Background and Objectives:

The BOEMRE defines decommissioning as the process of ending oil, gas, or sulfur operations and returning 

the lease or pipeline right-of-way to a condition that meets the requirements of the regulations. The BOEMRE 

will conduct detailed environmental reviews of any proposed decommissioning projects to evaluate the 

impacts from platform removal on regional fish populations. When a platform is disassembled, habitat 

is removed, and numerous fishes and invertebrates are killed. 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. 

At this time there are several key issues in the Pacific OCS platform decommissioning and reefing debate. 

Included is defining the ecological performance and role that platforms off California may play in the recovery of important groundfish populations (such as bocaccio, Sebastes paucispinis, and cowcod, Sebastes 

levis) in southern California. The Secretary of the Department of Commerce in January 2000 declared the 

West Coast groundfish fishery a disaster with extremely small populations remaining. Recent BOEMRE 

-funded studies 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. 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, in order to understand the environmental consequences of decommissioning platforms on local 

and regional fish populations, there is a need to know the importance of platforms as fish habitat when 

compared to adjacent natural reefs. In particular, it is necessary to know the densities, abundances, and size 

classes of economically important species over both artificial and natural substrates. Such information is 
ii

particularly important when the platforms harbor large numbers of resident, reproducing adults and serve 

as nursery habitat for juvenile fishes that eventually may “spillover” or migrate to natural areas and help to 

replenish populations that are commercial and recreational fishery resources. Natural reefs need to be surveyed in order to provide the context to which densities of rockfishes at oil platforms may be evaluated, and 

the ecological importance of platform habitat may be interpreted. 

Several BOEMRE - and USGS-funded investigations have been completed and provide background for the 

present effort. The habitat value of a number of platforms on the Pacific OCS was synthesized in MMS 2003-

032, The Ecological Role of Natural Reefs and Oil and Gas Production Platforms on Rocky Reef Fishes in Southern California. In this study, the fish assemblages from eight platforms and eight natural outcrops at similar 

depth were compared. The observations were from the surface to the seafloor on both platforms and natural 

reefs over a six-year period including 2001. The analyses were based on at least 40 submersible and hundreds 

of SCUBA dives on platforms and on 133 submersible and hundreds of SCUBA dives on natural outcrops 

located throughout southern California, the Santa Barbara Channel, and off Pt. Conception and Pt. Arguello. 

The study found that platform fish assemblages are somewhat different from those of natural reefs. However, these differences were due almost entirely to the greater numbers of fishes around platforms, rather than 

large differences in species composition between platforms and natural outcrops. At least 85 species of fish 

were observed at platforms and 94 species at the outcrops. Rockfishes dominated both habitats, comprising 

89.7% of all fishes at platforms and 92.5% at outcrops. Almost all of the more abundant species that the 

researchers observed were more common around platforms. Tremendous numbers of young-of-the-year 

(YOY) rockfish from several species settled at Platform Gail in 1999 with a lesser number recruiting to Platform Gilda. Species that were more common at one or more platforms than at natural reefs included cowcod and bocaccio (YOY, juvenile, and adult), copper, greenspotted, greenstriped, YOY and juvenile widow, 

vermilion, canary and flag rockfishes and YOY, juvenile, and adult lingcod. 

The BOEMRE has recognized that there is not yet enough data to extrapolate the importance of platforms 

and associated structures fish assemblages when compared to those of natural reefs. One data gap has been 

information about the number and size of natural reefs in the vicinity of platforms. Recognizing this need, 

BOEMRE has funded through USGS sea floor mapping in the eastern Santa Barbara Channel, currently being conducted by Dr. Guy Cochrane, United States Geological Survey. 

Pacific OCS platforms reside in a variety of depths and oceanographic conditions. This physical variability 

propagates to the biotic populations associated with these offshore structures, and suggests that a case-baycase 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, particularly as compared to those natural reefs in the vicinity of platforms. 

Data necessary for these comparisons include densities and size structures of the fishes inhabiting both platforms and natural reefs and the location, area, and number of these natural reefs. 

The primary goal of the present study was to fill gaps in information about the importance of POCS platform fish assemblages in southern and central California compared to those of nearby natural reefs. 

a) What is the relative contribution of platform fishes to the total hard structure fish assemblages (platforms 

and natural reef) in the region? 

b) What is the comparative importance of platforms and natural reefs as fish nursery grounds? 
iii

Specific objectives of this study were:

• To survey the fish assemblages at platforms in order to continue long-term and short-term studies, 

to acquire information from platforms that have never been surveyed, to encompass a wide range 

of structures, occupying a diversity of water depths, geographic locations, and water masses. 

• Estimate the densities of all species at both platform and natural reef habitat and characterize the 

habitat of each fish observed.

• To synthesize the data into a report describing the ecological performance of platforms as rockfish 

habitat and as rockfish producers in comparison to natural reefs off California.

Description:

Results of this research are summarized in two tasks. 

Task One: Fish Assemblages at Central and Southern California Oil Platforms and Natural 

Sites: 2004–2009

In this task, we conducted surveys around a majority of the platforms off California and at many natural sites, using the research submarine Delta. We surveyed fishes around the midwaters, bottoms, and the 

surrounding shell mounds of platforms.

Task Two: A Comparison of Fish Assemblages in the Midwaters of Two California Oil and Gas 

Platforms

It is unclear what role habitat complexity plays in structuring fish assemblages around oil and gas 

platforms. In this task, we compared the midwater fish assemblages at a platform with relatively little jacket 

complexity (Gail) with one that is quite complex (Eureka). 

Significant Results:

Task 1:

Surveys were conducted at platforms and natural sites between 2004 and 2009 aboard the research 

submersible Delta. Natural sites were comprised of both high and low rocky reefs. We conducted 803 transects around 20 platforms, encompassing 144,022 m2

 of habitat. The habitats of almost all platforms were 

surveyed at least once and some platforms were surveyed in a majority of years. In addition, we made 134 

natural site dives (422 transects, 377,851 m2), at bottom depths of 17–343 m. A total of at least 110 unique 

natural sites were assessed and some sites, such as North Reef, were surveyed in more than one year. Over 

all habitats, we observed 687,142 fishes, comprising a minimum of 128 species. Of these, 317,583 fishes, 

of 95 species, inhabited platforms and 369,559 fish, of 114 species, lived on natural sites. On average, fish 

densities were over twice as high at platforms (257.4 individuals/100 m2) compared to natural sites (104 

individuals/100m2). Rockfishes, of 45 species (at least 45 species at platforms and 43 species at natural sites) 

dominated the survey, as they comprised 85.8% of all fishes observed (83.8% at platforms and 87.5% at 

natural sites). 

Among the highest density species or species complexes, squarespot, halfbanded, and shortbelly rockfishes, and a complex of young-of-the-year (YOY) rockfishes dominated both platform and natural sites. 

Blacksmith, widow rockfish, jack mackerel, unidentified Sebastomus rockfishes, blackeye goby, and calico 

rockfish rounded out the top ten platform species. A somewhat different suite of species, including pygmy, 
iv

blackeye goby, unidentified Sebastomus rockfishes, swordspine rockfish, blacksmith, and blue rockfish comprised the top ten species by density at natural sites. 

We observed three distinct fish assemblages around each platform: midwaters, bottom, and shell 

mound. These assemblages did not appreciably change over the course of the study. There was a tendency 

for densities of fishes to increase and peak in deeper midwater depths or at the bottom. Fish densities over 

shell mounds were usually lower than those at the adjacent platform bottom. In addition, fish densities 

varied greatly between platforms at similar depths. However, there appeared to be no geographic pattern to 

these differences. There was a tendency for fish densities on the bottoms and shell mounds of the deepest 

platforms to be lower than those at shallower structures. 

Midwater assemblages were similar across platforms, while bottom and shell mound assemblages varied with platform bottom depth. In general, all of these assemblages were at least somewhat different from 

the assemblages observed on natural sites. There tended to be higher densities of young-of-the-year fishes, 

particularly rockfishes, around many platforms than at most natural sites. Older juveniles and adults of economically important species were also more likely to be found at higher densities at some platforms than at 

most natural sites. This latter may reflect 1) an extensive and complex bottom habitat around the bottoms 

of some platforms that serve as sheltering areas for economically important species and 2) the lower fishing 

effort (a de facto marine reserve effect) of platforms as many of these structures appear to be rarely fished. 

The shell mounds surrounding California platforms are a unique feature of these structures and are 

composed primarily of living and dead mussels, and associated marine life. They form an extensive web of 

low, but rugose, sea floor. The relatively small crevices created by mussel shells deter large numbers of many 

high-relief species from venturing onto these areas. Rather, most shell mound species are either the juveniles 

of larger species, whose juvenile stages require small sheltering sites, or somewhat generalist species that live 

over 1) soft sea floors, 2) the ecotones between soft and low-relief hard bottom, and 3) low-relief reefs. While 

shell mound assemblages in shallow and middle depth waters tend to be different from those of natural sites 

of the same depths, deep depth shell mound assemblages more closely resemble those at natural sites. This is 

likely because reefs in the deeper waters of California tend to be low relief and thus more like shell mounds. 

Task 2: 

We observed 13,609 fishes of at least 32 species at Platform Eureka and 2,980 fishes of at least 20 species at 

Platform Gail. Total average fish density was much higher at Eureka (135.9 individuals per 100 m2) than at Gail 

(28.7 individuals per 100 m2). Rockfishes (genus Sebastes) dominated both assemblages, comprising 99.5% 

and 96.7% of all fishes observed at Eureka and Gail, respectively. A minimum of 28 rockfish species (28 species at Eureka and 14 at Gail) inhabited the platform midwaters. Those species with highest densities at Eureka 

included squarespot, widow, speckled, and blue rockfishes, while squarespot and widow rockfishes and bocaccio dominated the midwaters of Gail. Fifteen species were unique to Eureka and four species were found only 

at Gail. Of the species shared by the two structures, the densities of almost all species were higher at Eureka, 

sometimes by a factor of 10 or more. The number of species around the crossbeams varied with depth (ranging 

from 6-11 at Gail, and 14-18 at Eureka) and tended to be highest around the deeper members. Between the two 

platforms, species numbers were higher at all depths at Eureka and usually 2-3 times that of Gail. 

Thus, while the assemblages of both platforms were dominated by rockfishes there were also significant differences between them. Compared to Gail, Eureka harbored 1) higher densities both of all species 

combined and of most species held in common, 2) far more mature individuals of most species, 3) greater 

species richness, and 4) much higher densities of species that live over complex high relief. We propose that 

from a fish’s perspective, the complex midwater jacket of Eureka, with its many sheltering sites, mimics rugose 

natural reefs. This research both re-enforces the conclusion that many reef species have quite specific habitat 

requirements and that the platform decommissioning process must examine each platform individually.
v

STUDY PRODUCTS

Papers

2005 Love, M. S. and A. York. A comparison of the fish assemblages associated with

an oil/gas pipeline and adjacent seafloor in the Santa Barbara Channel, Southern 

California Bight. Bull Mar. Sci. 77:101-117.

2006 Emery, B. M., L. Washburn, M. S. Love, M. N. Nishimoto, and J. C. Ohlmann.

Do oil and gas platforms off California reduce recruitment of bocaccio (Sebastes 

paucispinis) to natural habitats? Analysis on trajectories derived from high 

frequency radar. Fish. Bull. 104:391-400.

Love, M. S. and D. M. Schroeder. 2006. Ecological performance of OCS platforms as 

fish habitat off California. OCS Study MMS 2004-005. Marine Science Institute, 

University of California, Santa Barbara. MMS Cooperative Agreement 

Number 1435-01-03-CA72694.

Love, M. S. and A. York. The role of bottom crossbeam complexity in 

influencing the fish assemblages at California oil and gas platforms. Fish. Bull. 

104:542-549.

Love, M. S., D. M. Schroeder, and B. Lenarz. Gimme shelter: the importance of 

crevices to some fish species inhabiting a deeper-water rocky outcrop in southern 

California. CalCOFI Rep. 47:119-126.

Love, M. S., D. M Schroeder, W. Lenarz, A. MacCall, A. Scarborough-Bull, and 

L. Thorsteinson. Potential utility of offshore marine structures in rebuilding an 

overfished rockfish species, bocaccio (Sebastes paucispinis). Fish. Bull. 104:383-390.

Scarborough-Bull, A., M. S. Love, and D. M. Schroeder. Artificial reefs as fishery 

conservation tools: contrasting the roles of offshore structures between the Gulf of 

Mexico and the southern California Bight. American Fisheries Society 

Symposium, p. 587-603.

2007 Love, M. S. and D. M. Schroeder. A characterization of the fish assemblage of 

deep photic zone rock outcrops in the Anacapa Passage, Southern California, 

1995 to 2004. with evidence of a regime shift. CalCOFI Rep. 48:165-176.

Love, M. S., E. Brothers, D. M. Schroeder, and W. H. Lenarz. Ecological 

performance of young-of-the year blue rockfish (Sebastes mystinus) associated 

with oil platforms and natural reefs in California as measured by daily growth 

rates. Bull. Mar. Sci. 80:147-157.
vi

2008 Love, M. S. and M. Yoklavich. Habitat characteristics of juvenile cowcod, 

Sebastes levis (Scorpaenidae), in Southern California. Env. Biol. Fish. 

82:195-202. 

Scarborough-Bull, A., M. S. Love, and D. M. Schroeder. Artificial reefs as fishery 

conservation tools: contrasting the roles of offshore structures between the Gulf 

of Mexico and the Southern California Bight. Amer. Fish. Soc. Symp. 49:899-915.

2009 Love, M. S., M. Yoklavich, and D. M. Schroeder. Demersal fish assemblages in 

the Southern California Bight based on visual surveys in deep water. Env. 

Biol. Fish. 874:55-68.

Love, M. S. and S. R. Goldberg. A histological examination of the ovaries of Pacific 

sanddab, Citharichthys sordidus, captured at two oil platforms and two natural sites 

in the southern California Bight. Bull. S. Calif. Acad. Sci. 108:45-51.

Love, M. S., M. Nishimoto, and M. Saiki. Reproductive ecology and body burden 

of resident fish prior to decommissioning. MMS OCS Study 2009–019. Marine 

Science Institute, University of California, Santa Barbara, California. MMS 

Cooperative Agreement Number 1435–01–05–CA–39315.
vii

Fish Assemblages Associated with Platforms and Natural Reefs 

in Areas Where Data are Non-Existent or Limited

EXECUTIVE SUMMARY

Information Needed

There are 27 oil and gas platforms in the waters off California. These platforms are located between 1.2 

and 10.5 miles from shore and at depths ranging from 11 to 363 m (35–1,198 ft). All platforms have a finite 

economic life and the life spans of some California platforms may be nearing an end. Once an industrial 

decision is made to cease oil and gas production at a platform, managers must decide what to do with the 

structure, a process known as decommissioning. The BOEMRE defines decommissioning as the process 

of ending oil, gas, or sulfur operations and returning the lease or pipeline right-of-way to a condition that 

meets the requirements of the regulations. The BOEMRE will conduct detailed environmental reviews of 

any proposed decommissioning projects to evaluate the impacts from platform removal on regional fish 

populations. When a platform is disassembled, habitat is removed, and numerous fishes and invertebrates 

are killed. 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. 

At this time there are several key issues in the Pacific OCS platform decommissioning and reefing debate. 

Included is defining the ecological performance and role that platforms off California may play in the recovery of important groundfish populations (such as bocaccio, Sebastes paucispinis, and cowcod, Sebastes 

levis) in southern California. The Secretary of the Department of Commerce in January 2000 declared the 

West Coast groundfish fishery a disaster with extremely small populations remaining. Recent BOEMRE 

-funded studies 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. 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, in order to understand the environmental consequences of decommissioning platforms on local 

and regional fish populations, there is a need to know the importance of platforms as fish habitat when 

compared to adjacent natural reefs. In particular, it is necessary to know the densities, abundances, and size 

classes of economically important species over both artificial and natural substrates. Such information is 

particularly important when the platforms harbor large numbers of resident, reproducing adults and serve 

as nursery habitat for juvenile fishes that eventually may “spillover” or migrate to natural areas and help to 

replenish populations that are commercial and recreational fishery resources. Natural reefs need to be surveyed in order to provide the context to which densities of rockfishes at oil platforms may be evaluated, and 

the ecological importance of platform habitat may be interpreted. 
viii

Several BOEMRE - and USGS-funded investigations have been completed and provide background for 

the present effort. The habitat value of a number of platforms on the Pacific OCS was synthesized in MMS 

2003-032, The Ecological Role of Natural Reefs and Oil and Gas Production Platforms on Rocky Reef Fishes in 

Southern California. In this study, the fish assemblages from eight platforms and eight natural outcrops at 

similar depth were compared. The observations were from the surface to the seafloor on both platforms and 

natural reefs over a six-year period including 2001. The analyses were based on at least 40 submersible and 

hundreds of SCUBA dives on platforms and on 133 submersible and hundreds of SCUBA dives on natural 

outcrops located throughout southern California, the Santa Barbara Channel, and off Pt. Conception and 

Pt. Arguello. 

The study found that platform fish assemblages are somewhat different from those of natural reefs. However, these differences were due almost entirely to the greater numbers of fishes around platforms, rather than 

large differences in species composition between platforms and natural outcrops. At least 85 species of fish 

were observed at platforms and 94 species at the outcrops. Rockfishes dominated both habitats, comprising 

89.7% of all fishes at platforms and 92.5% at outcrops. Almost all of the more abundant species that the 

researchers observed were more common around platforms. Tremendous numbers of young-of-the-year 

(YOY) rockfish from several species settled at Platform Gail in 1999 with a lesser number recruiting to Platform Gilda. Species that were more common at one or more platforms than at natural reefs included cowcod and bocaccio (YOY, juvenile, and adult), copper, greenspotted, greenstriped, YOY and juvenile widow, 

vermilion, canary and flag rockfishes and YOY, juvenile, and adult lingcod. 

The BOEMRE has recognized that there is not yet enough data to extrapolate the importance of platforms 

and associated structures fish assemblages when compared to those of natural reefs. One data gap has been 

information about the number and size of natural reefs in the vicinity of platforms. Recognizing this need, 

BOEMRE has funded through USGS sea floor mapping in the eastern Santa Barbara Channel, currently being conducted by Dr. Guy Cochrane, United States Geological Survey. 

Pacific OCS platforms reside in a variety of depths and oceanographic conditions. This physical variability 

propagates to the biotic populations associated with these offshore structures, and suggests that a case-baycase 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, particularly as compared to those natural reefs in the vicinity of platforms. 

Data necessary for these comparisons include densities and size structures of the fishes inhabiting both platforms and natural reefs and the location, area, and number of these natural reefs. 

The primary goal of the present study was to fill gaps in information about the importance of POCS platform fish assemblages in southern and central California compared to those of nearby natural reefs. 

a) What is the relative contribution of platform fishes to the total hard structure fish assemblages (platforms 

and natural reef) in the region? 

b) What is the comparative importance of platforms and natural reefs as fish nursery grounds? 
ix

Specific objectives of this study were:

• To survey the fish assemblages at platforms in order to continue long-term and short-term studies, 

to acquire information from platforms that have never been surveyed, to encompass a wide range 

of structures, occupying a diversity of water depths, geographic locations, and water masses. 

• Estimate the densities of all species at both platform and natural reef habitat and characterize 

the habitat of each fish observed.

• To synthesize the data into a report describing the ecological performance of platforms as 

rockfish habitat and as rockfish producers in comparison to natural reefs off California.

Research Summary

Task 1: Fish Assemblages at Central and Southern California Oil Platforms and Natural Sites: 

2004–2009

Surveys were conducted at platforms and natural sites between 2004 and 2009 aboard the research 

submersible Delta. Natural sites were comprised of both high and low rocky reefs. We conducted 803 transects around 20 platforms, encompassing 144,022 m2

 of habitat. The habitats of almost all platforms were 

surveyed at least once and some platforms were surveyed in a majority of years. In addition, we made 134 

natural site dives (422 transects, 377,851 m2), at bottom depths of 17–343 m. A total of at least 110 unique 

natural sites were assessed and some sites, such as North Reef, were surveyed in more than one year. Over 

all habitats, we observed 687,142 fishes, comprising a minimum of 128 species. Of these, 317,583 fishes, 

of 95 species, inhabited platforms and 369,559 fish, of 114 species, lived on natural sites. On average, fish 

densities were over twice as high at platforms (257.4 individuals/100 m2) compared to natural sites (104 

individuals/100m2). Rockfishes, of 45 species (at least 45 species at platforms and 43 species at natural sites) 

dominated the survey, as they comprised 85.8% of all fishes observed (83.8% at platforms and 87.5% at 

natural sites).

Among the highest density species or species complexes, squarespot, halfbanded, and shortbelly 

rockfishes, and a complex of young-of-the-year (YOY) rockfishes dominated both platform and natural 

sites. Blacksmith, widow rockfish, jack mackerel, unidentified Sebastomus rockfishes, blackeye goby, and 

calico rockfish rounded out the top ten platform species. A somewhat different suite of species, including 

pygmy, blackeye goby, unidentified Sebastomus rockfishes, swordspine rockfish, blacksmith, and blue rockfish comprised the top ten species by density at natural sites. 

We observed three distinct fish assemblages around each platform: midwaters, bottom, and shell 

mound. These assemblages did not change appreciably over the course of the study. There was a tendency 

for densities of fishes to increase and peak in deeper midwater depths or at the bottom. Fish densities over 

shell mounds were usually lower than those at the adjacent platform bottom. In addition, fish densities 

varied greatly between platforms at similar depths. However, there appeared to be no geographic pattern to 

these differences. There was a tendency for fish densities on the bottoms and shell mounds of the deepest 

platforms to be lower than those at shallower structures. 

Midwater assemblages were similar across platforms, while bottom and shell mound assemblages 

varied with platform bottom depth. In general, all of these assemblages were at least somewhat different 

from the assemblages observed on natural sites. There tended to be higher densities of young-of-the-year 

fishes, particularly rockfishes, around many platforms than at most natural sites. Older juveniles and adults 

of economically important species were also more likely to be found at higher densities at some platforms 
x

than at most natural sites. This latter may reflect 1) an extensive and complex bottom habitat around the 

bottoms of some platforms that serve as sheltering areas for economically important species and 2) the 

lower fishing effort (a de facto marine reserve effect) of platforms as many of these structures appear to be 

rarely fished. 

The shell mounds surrounding California platforms are a unique feature of these structures and are 

composed primarily of living and dead mussels, and associated marine life. They form an extensive web of 

low, but rugose, sea floor. The relatively small crevices created by mussel shells deter large numbers of many 

high-relief species from venturing onto these areas. Rather, most shell mound species are either the juveniles 

of larger species, whose juvenile stages require small sheltering sites, or somewhat generalist species that live 

over 1) soft sea floors, 2) the ecotones between soft and low-relief hard bottom, and 3) low-relief reefs. While 

shell mound assemblages in shallow and middle depth waters tend to be different from those of natural sites 

of the same depths, deep depth shell mound assemblages more closely resemble those at natural sites. This is 

likely because reefs in the deeper waters of California tend to be low relief and thus more like shell mounds. 

Task 2: A Comparison of Fish Assemblages in the Midwaters of Two California Oil and Gas 

Platforms

In this study, we compared the midwater fish assemblages of Platform Eureka, whose midwater jacket 

is studded with fascicles of pilings and bowl-shaped piling guides, with that of Platform Gail, a more typically configured platform with rounded crossbeams and pilings. These two platforms are similar in other 

respects. They were constructed at about the same time, Eureka in 1984 and Gail in 1987. Both platforms 

are about 13 km from shore and stand in similar depths: Gail in 224 m, Eureka in 212 m. Both have nine 

midwater crossbeams and these crossbeams are situated at comparable depths. Although Eureka is found 

about 118 km to the southeast of Gail, both platforms are in the southern California Bight and are bathed 

by waters of similar temperatures. Lastly, the dominant natural reef species in the two areas are comparable.

While the fish assemblages of both platforms were dominated by rockfishes (Sebastes), there were 

significant differences. Compared to Gail, Eureka harbored 1) higher densities both of all species combined 

and of most species held in common, 2) far more mature individuals of most species, 3) greater species 

richness, and 4) much higher densities of species that live over complex high relief. We propose that from 

a fish’s perspective, the complex midwater jacket of Eureka, with its many sheltering sites, mimics rugose 

natural reefs. This research both re-enforces the conclusion that many reef species have quite specific habitat 

requirements and that the platform decommissioning process must examine each platform individually.
xi

Conclusions

This research strengthens and confirms observations made in previous studies. 

1) There is very extensive diversity in the species assemblages around the oil and gas platforms of 

California. Factors driving this variability include A) location around the platform, B) geographic location 

of the platforms, and C) bottom depth of the platform.

2) Around each platform, there are three, unique, fish assemblages: midwaters, bottom, and shell 

mound. While a suite of rockfishes (of 43 species) dominate most platform assemblages, a number of other 

taxa (e.g., lingcod, combfishes, sculpins, and seaperches) are also important. These assemblages did not appreciably change over the course of the study. 

3) Midwater fish assemblages tend to be similar across platforms; there are substantial differences 

among those found at bottoms and shell mounds. Platform bottom depth, and the complexity of the platform jacket at the bottom, is important in structuring bottom fish assemblages. Bottom depth also influences shell mound assemblages. 

4) In general, the assemblages of platforms and natural sites are different. These differences are primarily based on differences in species’ densities rather than the presence or absence of taxa. A) All of the 

platforms we surveyed serve as nursery grounds for a variety of rockfishes and other taxa and, in general, 

platform habitats harbor higher densities of young fishes than do many natural sites. B) The bottoms of a 

number of platforms have higher densities of economically important species than do most natural sites. 

This is probably due to a combination of extensive, complex habitat (most suitable for these species) and 

relatively low fishing pressure (a de facto marine reserve effect). C) The shell mounds surrounding California 

platforms are a unique feature of these structures and are composed primarily of living and dead mussels, 

and associated marine life. They form an extensive web of low, but rugose, sea floor. Most shell mound species are either the juveniles of larger species, whose juvenile stages require small sheltering sites, or somewhat 

generalist species that live over 1) soft sea floors, 2) the ecotones between soft and low-relief hard bottom, 

and 3) low-relief reefs. While shell mound assemblages in shallow and middle depth waters tend to be different from those of natural sites of the same depths, deep depth shell mound assemblages more closely 

resemble those at natural sites. This is likely because reefs in the deeper waters of California tend to be low 

relief and thus more like shell mounds.

5) The role that habitat complexity plays in structuring platform fish assemblages should not be underestimated. We compared the species assemblages of fishes living around two deepwater platforms, Eureka 

and Gail. Gail is a typical California platform, with rounded crossbeams and pilings, while the midwater 

jacket of Eureka, studded with fascicles of pilings and bowl-shaped piling guides, is much more complex. 

While rockfishes dominated the assemblages of both platforms, there were also significant differences. Compared to Gail, Eureka harbored 1) higher densities both of all species combined and of most species held in 

common, 2) far more mature individuals of most species, 3) greater species richness, and 4) much higher 

densities of species that live over complex high relief. Thus, it is likely that the complex midwater jacket of 

Eureka, with its many sheltering sites, mimics rugose natural reefs. This both re-enforces the conclusion that 

many reef species have quite specific habitat requirements and that the platform decommissioning process 

must examine each platform individually. 

1

Task 1: Fish Assemblages at Central and Southern California Oil Platforms and Natural Sites: 

2004–2009

Milton S. Love, William H. Lenarz, Mary Nishimoto, and Donna M. Schroeder

Abstract

Surveys were conducted at platforms and natural sites between 2004 and 2009 aboard the research 

submersible Delta. Natural sites were comprised of both high and low rocky reefs. We conducted 803 transects 

around 20 platforms, encompassing 144,022 m2 of habitat. The habitats of almost all platforms were surveyed 

at least once and some platforms were surveyed in a majority of years. In addition, we made 134 natural site 

dives (422 transects, 377,851 m2), at bottom depths of 17–343 m. A total of at least 110 unique natural sites 

were assessed and some sites, such as North Reef, were surveyed in more than one year. Over all habitats, 

we observed 687,142 fishes, comprising a minimum of 128 species. Of these, 317,583 fishes, of 95 species, 

inhabited platforms and 369,559 fish, of 114 species, lived on natural sites. On average, fish densities were 

over twice as high at platforms (257.4 individuals/100 m2) compared to natural sites (104 individuals/100m2). 

Rockfishes, of 45 species (at least 45 species at platforms and 43 species at natural sites) dominated the survey, 

as they comprised 85.8% of all fishes observed (83.8% at platforms and 87.5% at natural sites).

Among the highest density species or species complexes, squarespot, halfbanded, and shortbelly rockfishes, and a complex of young-of-the-year (YOY) rockfishes dominated both platform and natural sites. 

Blacksmith, widow rockfish, jack mackerel, unidentified Sebastomus rockfishes, blackeye goby, and calico 

rockfish rounded out the top ten platform species. A somewhat different suite of species, including pygmy, 

blackeye goby, unidentified Sebastomus rockfishes, swordspine rockfish, blacksmith, and blue rockfish comprised the top ten species by density at natural sites. 

We observed three distinct fish assemblages around each platform: midwaters, bottom, and shell 

mound. These assemblages did not appreciably change over the course of the study. There was a tendency 

for densities of fishes to increase and peak in deeper midwater depths or at the bottom. Fish densities over 

shell mounds were usually lower than those at the adjacent platform bottom. In addition, fish densities 

varied greatly between platforms at similar depths. However, there appeared to be no geographic pattern to 

these differences. There was a tendency for fish densities on the bottoms and shell mounds of the deepest 

platforms to be lower than those at shallower structures. 

Midwater assemblages were similar across platforms, while bottom and shell mound assemblages varied with platform bottom depth. In general, all of these assemblages were at least somewhat different from 

the assemblages observed on natural sites. There tended to be higher densities of young-of-the-year fishes, 

particularly rockfishes, around many platforms than at most natural sites. Older juveniles and adults of economically important species were also more likely to be found at higher densities at some platforms than at 

most natural sites. This latter may reflect 1) an extensive and complex bottom habitat around the bottoms 

of some platforms that serve as sheltering areas for economically important species and 2) the lower fishing 

effort (a de facto marine reserve effect) of platforms as many of these structures appear to be rarely fished. 

The shell mounds surrounding California platforms are a unique feature of these structures and are 

composed primarily of living and dead mussels, and associated marine life. They form an extensive web of 

low, but rugose, sea floor. The relatively small crevices created by mussel shells deter large numbers of many 

high-relief species from venturing onto these areas. Rather, most shell mound species are either the juveniles 

of larger species, whose juvenile stages require small sheltering sites, or somewhat generalist species that live 

over 1) soft sea floors, 2) the ecotones between soft and low-relief hard bottom, and 3) low-relief reefs. While 

shell mound assemblages in shallow and middle depth waters tend to be different from those of natural sites 

of the same depths, deep depth shell mound assemblages more closely resemble those at natural sites. This is 

likely because reefs in the deeper waters of California tend to be low relief and thus more like shell mounds. 
2

Introduction

Offshore oil and gas platforms have continuously occupied California marine waters since 1958. Currently, there are 26 platforms in California waters, 23 are in federal waters and 3 are in state waters. They 

are located between 2 and 17 km from shore, in waters between 11 and 363 m deep. Other details regarding 

platform placement are found in Love et al. (2003). California platforms are steel structures and all are attached to the sea floor. The platform structure, referred as the jacket, is composed of vertical pilings, and 

horizontal and diagonal crossbeams. The crossbeams are located at about 30 m intervals and range from 

near the surface to the bottom. A shell mound, composed of mussels and other invertebrates that have fallen 

from the jacket, surrounds each platform.

All oil and gas platforms have a finite economic life, one driven by the price of oil and gas and by operating costs. Thus, at some point, all platforms become uneconomical to operate and become candidates 

for decommissioning. Decommissioning may take a number of forms, ranging from leaving much, or all, of 

the jacket in place to complete removal (Schroeder and Love 2004). Off California, seven platforms (Harry 

– 1974, Helen – 1978, Herman – 1978, Hilda, Hazel, Hope, and Heidi – 1996) have been decommissioned 

by complete removal, although the removal of the latter 4 platforms was not without controversy (Love et 

al. 2003).

Management decisions regarding decommissioning (in federal waters involving a number of agencies 

including the Bureau of Ocean Energy Management, Regulation, and Enforcement (BOEMRE) (Schroeder 

and Love 2004) are based on both biological and socioeconomic information. In order to better understand 

the role that platforms might play as fish habitat, beginning in 1995 our group, funded by the BOEMRE, 

National Biological Survey, United States Geological Survey, and California Artificial Reef Enhancement, 

has conducted research around California oil platforms and natural reefs. A summary of the first six years 

of that research was published in Love et al. (2003) and Table 1 lists additional papers and reports that have 

come from this research through 2009. This report presents data from submersible surveys of platforms and 

natural reefs conducted between 2004 and 2009.

Methods

Fish Surveys

Surveys were conducted at platforms and natural sites between 2004 and 2009 aboard the research 

submersible Delta. Natural sites were comprised of both high and low rocky reefs. Delta is 4.8 m in length, 

accommodates one scientific observer and one pilot, and has a maximum operating depth of 365 m. Dives 

were made between September and November, during daytime hours, and were documented with an externally mounted video camera positioned above the middle viewing-porthole on the starboard side of the 

submersible. The scientific observer conducted a belt-transect survey through this same starboard viewing 

port, verbally recording onto the videotape all fishes and identifying each to the lowest possible taxon. The 

observer estimated the total length (cm) of these fishes using reference light points from two parallel lasers 

installed 20 cm apart on either side of the external video camera. These lasers also helped delineate the 

width (2 meters) of the transects. A constant speed between 0.5 and 1.0 knot was attempted. During dives 

on both shell mounds and natural sites, we attempted to maintain a constant distance within 1 meter of 

the seafloor. For each platform, we conducted surveys 1) on the shell mound, 2) platform bottom, and 3) 

platform midwaters.

Transect length was estimated using navigation fixes (latitude and longitude coordinates) received 

from a Thales GeoPacific Winfrog ORE Trackpoint 2 USBL system at two-second intervals, and a Winfrog DAT file was generated for each dive. Distance and duration between fixes were calculated to obtain 

a point-to-point submersible speed; errant navigation fixes were removed when speed exceeded 2 m/sec. 
3

The navigation fixes were then smoothed using a nine-point moving average, and transect length was estimated from the total distance between the smoothed points. Transect length was divided by transect duration to obtain an average transect speed. The length of individual habitat patches was estimated from average speed of the submersible during each transect. 

This survey methodology underestimates the densities of some fish species. In particular, small and 

cryptic taxa, such as the bluebanded and zebra gobies (Lythrypnus dalli and L. zebra, respectively) are rarely 

observed and a number of flatfish species are difficult to visually identify. In addition, schools of benthopelagic forms, such as yellowtail rockfish (Sebastes flavidus), will occasionally aggregate in the water column 

above the Delta and are not counted.

Authors Date Topic

Emery et al. 2006 Model of rockfish recruitment to platforms.

Love et al. 1997 A description of platform fish assemblage results from the 

first year of research.

Love et al. 1999 Fish assemblages of platform shell mounds.

Love et al. 1999 A description of several years of platform fish assemblage research.

Love et al. 2000 Fish assemblages of platform midwaters and bottoms.

Love et al. 2003 A synthesis of six years of platform surveys.

Schroeder and Love 2004 Ecological and political issues surrounding platform decommissioning.

Love and York 2005 Fish assemblages on oil pipelines.

Love et al. 2005 Estimates of larval production of two rockfish species around oil 

platforms.

Love and Schroeder 2006 A summary of three separate platform experiments.

Love et al. 2006 Role of platform crossbeam complexity in influencing fish assemblages.

Love et al. 2006 Potential for platforms to rebuild overfished rockfish stocks.

Love et al. 2006 Role of crevices in structuring deeper-water reef assemblages.

Goddard and Love 2007 A description of the larger invertebrates inhabiting platform shell mounds.

Love and Schroeder 2007 Characterization of fish assemblages in a moderately deep reef system.

Love et al. 2007 A comparison of growth rates of young rockfish at platforms and

natural reefs.

Nishimoto et al. 2007 A assessment of the oceanographic factors involved in rockfish young-ofthe-year recruitment to platforms.

Page et al. 2007 A comparison of trophic links and condition of fishes living on platforms 

and natural reefs.

Love and Yoklavich 2008 A description of the habitat of the cowcod, Sebastes levis.

Love and Goldberg 2009 A histological examination of ovaries of Pacific sanddab at platforms and 

natural reefs.

Love et al. 2009 A comparison of heavy metal burdens, otolith microchemistry signatures, 

and ovary condition of fishes living around platforms and natural reefs.

Love et al. 2009 A description of rocky reef fish assemblages throughout southern 

California

Table 1. A summary of platform and natural reef-related papers based on research conducted by Milton Love’s laboratory, 1995–2009.
4

Data Analysis

We treated transect densities (count/100 m2) of each taxon as observations. Densities were transformed 

to the fourth root to satisfy variance homogeneity assumptions for discriminant analyses. We used the same 

transformation for cluster analysis to be consistent. Densities for each species were standardized to a mean 

of zero and standard deviation of one. We used the lda procedure of R(R 2005) to perform discriminant 

analysis. The procedure hclust was used for the analysis, along with the average linkage option of the Unweighted Pair-Groups Method for performing the hierarchical agglomerative clustering. The Euclidean 

method was used for calculating distances. Averages of standardized transformed densities of taxa within 

high order clusters were calculated for each habitat type. 

Results

Summary of Platform and Natural Site Fish Assemblages

We conducted 803 transects around 20 platforms, encompassing 144,022 m2 of habitat (Figure 1, Tables 2, 3). The habitats of almost all platforms were surveyed at least once and some platforms (e.g., Irene, 

Hidalgo, Grace, Gilda, Gail, Edith, Elly, and Eureka) were surveyed in a majority of years. Poor visibility 

prevented us from surveying the bottoms and shell mounds of platforms A, B, C, Hillhouse, Henry, and 

Habitat. In addition, we made 134 natural site dives (422 transects, 377,851 m2), at bottom depths of 17–343 

m (Figure 1, Table 3). A total of at least 110 unique natural sites were assessed and some sites, such as North 

Reef, were surveyed in more than one year. 

Over all habitats, we observed 687,142 individuals, comprising a minimum of 128 species (Table 4). 

Of these, 317,583 fishes, of 95 species, inhabited platforms and 369,559 fish, of 114 species, lived on natural 

500 m

500 m

500 m

100 m

1000 m

100 m

100 m

2000 m

Point Conception

San Miguel Is. Santa Rosa Is. Santa Cruz Is. Anacapa Is.Harrison’s Reef

Santa Barbara Is.

Santa Catalina Is.

San Nicolas Is.

San Clemente Is.

Santa Barbara

Los Angeles

Santa Monica Bay

Ventura

San

Diego

Piggy Bank

Santa Cruz I.

The Footprint

Anacapa Is.

Pt. Arguello

Platform

Dive Sites

Submersible Dive Sites

2004-2009

Figure 1. Location of fish surveys, 2004–2009, at platforms (stars) and natural sites (circles), off California.
5

IRENE 2004 2005 2006 2007 2008 2009

Midwater x x x x x

Bottom x x x x x

Shell mound x x x x x

HIDALGO 2004 2005 2006 2007 2008 2009

Midwater x x x x

Bottom x x x x

Shell mound x x v x

HARVEST 2004 2005 2006 2007 2008 2009

Midwater x

Bottom x

Shell mound x

HERMOSA 2004 2005 2006 2007 2008 2009

Midwater x

Bottom x x

Shell mound x x

HARMONY 2004 2005 2006 2007 2008 2009

Midwater x

Bottom x

Shell mound x

HERITAGE 2004 2005 2006 2007 2008 2009

Midwater x

Bottom x

Shell mound

HONDO 2004 2005 2006 2007 2008 2009

Midwater x x x

Bottom x x x

Shell mound x x

Holly 2004 2005 2006 2007 2008 2009

Midwater x x x x x x

Bottom x x x x x

Shell mound x x x

A 2004 2005 2006 2007 2008 2009

Midwater only x x x

B 2004 2005 2006 2007 2008 2009

Midwater only x x

C 2004 2005 2006 2007 2008 2009

Midwater only x x

HILLHOUSE 2004 2005 2006 2007 2008 2009

Midwater only x x x

HENRY 2004 2005 2006 2007 2008 2009

Midwater only x

HABITAT 2004 2005 2006 2007 2008 2009

Midwater only x x x

GRACE 2004 2005 2006 2007 2008 2009

Midwater x x x x x

Bottom x x x x x

Shell mound x x x x x

GILDA 2004 2005 2006 2007 2008 2009

Midwater x x x x x

Bottom x x x x

Shell mound x x x x

Gail 2004 2005 2006 2007 2008 2009

Midwater x x x x x x

Bottom x x x x x x

Shell mound x x x x x x

EDITH 2004 2005 2006 2007 2008 2009

Midwater x x x x x

Bottom x x x x x

Shell mound x x x x x

ELLY 2004 2005 2006 2007 2008 2009

Midwater x x x x x

Bottom x x x x x

Shell mound x x x x x

EUREKA 2004 2005 2006 2007 2008 2009

Midwater x x x x x x

Bottom x x x

Shell mound x x x

Table 2. Platforms surveyed, 2004–2009. Note that in some years, not all habitats (midwater, bottom, and shell mound) at a platform were surveyed.
6

Table 3. Area surveyed (m2) by habitat type, 2004–2009. 

Habitat Number of Transects1 Area Surveyed (m2)

Platform midwater 275 82,846

Platform bottom 55 25,849

Platform shell mound 51 35,327

Natural sites 422 377,851

Total 803 521,773

1

For platforms, transects are defined as a circumnavigation of a midwater cross beam, platform 

bottom or shell mound. For natural sites, transects are defined as 15 minute surveys. 

Table 4. Numbers and densities (average number per 100 m2) of fish species observed at platforms and natural reefs, 

2004–2009. Rankings of total counts and average densities may differ because densities are averages of transect densities 

and area surveyed varied among transects.

Common Name Scientific Name Platforms Natural Sites Total Number

Number Density Number Density

Squarespot rockfish Sebastes hopkinsi 83,635 65.4 128,842 36.3 212,478

Halfbanded rockfish Sebastes semicinctus 85,675 44.6 77,775 21.2 163,450

Unidentified rockfish1 Sebastes spp. 36,986 30.1 24,003 6.6 60,989

Shortbelly rockfish Sebastes jordani 14,297 10.6 45,706 13.6 60,003

Blacksmith Chromis punctipinnis 21,522 31.4 4,830 1.4 26,352

Widow rockfish Sebastes entomelas 24,267 24.1 202 <0.1 24,469

Pygmy rockfish Sebastes wilsoni 125 <0.1 18,755 5.6 18,880

Blackeye goby Rhinogobiops nicholsii 3,018 1.8 13,843 3.6 16,861

Sebastomus sp. 3,028 1.9 12,286 3.5 15,314

Jack mackerel Trachurus symmetricus 12,287 24.5 91 <0.1 12,378

Swordspine rockfish Sebastes ensifer 42 <0.1 9,090 2.7 9,132

Bocaccio Sebastes paucispinis 3,006 2.1 1,241 2.7 4,247

Vermilion rockfish2 2,435 1.5 1,777 0.5 4212

Calico rockfish Sebastes dallii 3,341 2.2 176 <0.1 3,517

Rosy rockfish Sebastes rosaceus 1,266 0.8 1,963 0.6 3,229

Pinkrose rockfish Sebastes simulator 1,068 0.5 2,125 0.6 3,193

Blue rockfish3 524 0.5 2,550 0.6 3,074

Painted greenling Oxylebius pictus 2,672 2.3 394 0.1 3,066

Bank rockfish Sebastes rufus 943 0.7 1,870 0.5 2,813

Shortspine combfish Zaniolepis frenata 144 <0.1 2,435 0.7 2,579

Northern anchovy Engraulis mordax 2,130 2.4 0 0 2,130

Unidentified fishes 920 0.8 1,164 0.3 2,084

Lingcod Ophiodon elongatus 1,107 0.6 835 0.2 1,942

Pink seaperch Zalembius rosaceus 237 0.1 1,650 0.5 1,887

Stripetail rockfish Sebastes saxicola 1,177 0.3 436 0.1 1,613

Flag rockfish Sebastes rubrivinctus 1,083 0.7 476 0.1 1,559

Copper rockfish Sebastes caurinus 1,023 0.7 371 0.1 1,394

Olive rockfish Sebastes serranoides 827 0.8 564 0.1 1,391

Dwarf-red rockfish Sebastes rufianus 116 0.7 1,236 0.5 1,352

Spotted scorpionfish Scorpaena guttata 1,241 0.7 59 <0.1 1,300

Honeycomb rockfish Sebastes umbrosus 1,085 0.7 168 <0.1 1,253 

Starry rockfish Sebastes constellatus 135 <0.1 1,056 <0.1 1,191
7

Common Name Scientific Name Platforms Natural Sites Total Number

Number Density Number Density

Speckled rockfish Sebastes ovalis 651 0.4 453 0.1 1,104

Splitnose rockfish Sebastes diploproa 71 <0.1 793 0.2 864

Greenblotched rockfish Sebastes rosenblatti 501 0.2 282 <0.1 783

Unidentified sanddabs Citharichthys spp. 314 0.2 419 0.1 733

Greenstriped rockfish Sebastes elongatus 386 0.2 318 <0.1 704

Unidentified combfishes Zaniolepis spp. 40 <0.1 616 0.2 656

Sharpnose seaperch Phanerodon atripes 220 0.2 418 0.1 638

Unidentified poachers Family Agonidae 49 <0.1 576 0.1 625

Unidentified flatfishes 64 <0.1 526 0.1 590

California sheephead Semicossyphus pulcher 178 0.2 396 0.1 574

Pile perch Rhacochilus vacca 270 0.2 181 <0.1 451

Senorita Oxyjulis californica 15 <0.1 430 0.1 445

White seaperch Phanerodon furcatus 68 <0.1 377 <0.1 445

Deepwater blenny Cryptotrema corallinum 3 <0.1 402 0.1 405

Spotted ratfish Hydrolagus colliei 6 <0.1 364 <0.1 370

Unidentified surfperch Family Embiotocidae 112 <0.1 251 <0.1 363

Longspine combfish Zaniolepis latipinnis 32 <0.1 320 <0.1 352

Cowcod Sebastes levis 151 <0.1 186 <0.1 337

Kelp rockfish Sebastes atrovirens 287 0.3 7 <0.1 294

Unidentified ronquil Family Bathymasteridae 132 <0.1 137 <0.1 269

Sharpchin rockfish Sebastes zacentrus 201 <0.1 57 <0.1 258

Brown rockfish Sebastes auriculatus 200 0.1 51 <0.1 251

Unidentified pricklebacks Family Stichaeidae 8 <0.1 241 <0.1 249

Cabezon Scorpaenichthys marmoratus 244 0.2 1 <0.1 245

Yellowtail rockfish Sebastes flavidus 24 <0.1 207 <0.1 231

Bluebanded ronquil Rathbunella hypoplecta 117 <0.1 111 <0.1 228

Treefish Sebastes serriceps 101 <0.1 117 <0.1 218

Halfmoon Medialuna californiensis 207 0.2 0 0 207

Canary rockfish Sebastes pinniger 173 <0.1 23 <0.1 196

Dover sole Microstomus pacificus 29 <0.1 163 <0.1 192

Pacific hake Merluccius productus 3 <0.1 178 <0.1 181

Rubberlip seaperch Rhacochilus toxotes 15 <0.1 160 <0.1 175

Gopher rockfish Sebastes carnatus 45 <0.1 129 <0.1 174

Darkblotched rockfish Sebastes crameri 123 <0.1 40 <0.1 163

Rainbow seaperch Hypsurus caryi 0 0 163 <0.1 163

Unidentified thornyheads Sebastolobus spp. 55 <0.1 101 <0.1 156

Pacific sanddab Citharichthys stigmaeus 40 <0.1 109 <0.1 149

Rosethorn rockfish Sebastes helvomaculatus 9 <0.1 139 <0.1 148

Unidentified sculpin Family Cottidae 14 <0.1 121 <0.1 135

Spotfin sculpin Icelinus tenuis 0 0 127 <0.1 127

Bluebarred prickleback Plectobranchus evides 3 <0.1 114 <0.1 117

Unidentified eelpout Family Zoarcidae 53 <0.1 47 <0.1 100

Mexican rockfish Sebastes macdonaldi 94 <0.1 3 <0.1 97

Slender sole Lyopsetta exilis 92 <0.1 0 0 92

Garibaldi Hypsypops rubicunda 91 <0.1 0 0 91

Wolf-eel Anarrhichthys ocellatus 81 <0.1 5 <0.1 86

Blackgill rockfish Sebastes melanostomus 50 <0.1 26 <0.1 76

Freckled rockfish Sebastes lentiginosus 28 <0.1 42 <0.1 70

Pacific argentine Argentina sialis 1 <0.1 69 <0.1 70

Table 4 (continued)
8

Common Name Scientific Name Platforms Natural Sites Total Number

Number Density Number Density

Bigfin eelpout Lycodes cortezianus 0 0 52 <0.1 52

Kelp greenling Hexagrammos decagrammus 38 <0.1 11 <0.1 49

Chilipepper Sebastes goodei 5 <0.1 33 <0.1 38

California smoothtongue Leuroglossus stilbius 1 <0.1 35 <0.1 36

Pink rockfish Sebastes eos 2 <0.1 25 <0.1 27

Kelp bass Paralabrax clathratus 24 <0.1 2 <0.1 26

Ocean whitefish Caulolatilus princeps 0 0 25 <0.1 25

Pacific electric ray Torpedo californica 2 <0.1 22 <0.1 24

Yelloweye rockfish Sebastes ruberrimus 19 <0.1 5 <0.1 24

California lizardfish Synodus lucioceps 3 <0.1 20 <0.1 23

Icelinus sp. 3 <0.1 20 <0.1 23

Unidentified hagfish Eptatretus sp. 0 0 23 <0.1 23

Whitespotted rockfish Sebastes moseri 0 0 19 <0.1 19

Unidentified cuskeel Family Ophidiidae 3 <0.1 11 <0.1 14

English sole Parophrys vetulus 1 <0.1 13 <0.1 14

Bronzespotted rockfish Sebastes gilli 0 0 13 <0.1 13

Black perch Embiotoca jacksoni 0 0 12 <0.1 12

Longnose skate Raja rhina 0 0 11 <0.1 11

Shortspine thornyhead Sebastolobus alascanus 0 0 11 <0.1 11

Threadfin bass Pronotogrammus multifasciatus 1 <0.1 10 <0.1 11

Aurora rockfish Sebastes aurora 9 <0.1 1 <0.1 10

Rex sole Glyptocephalus zachirus 0 0 9 <0.1 9

Bearded eelpout Lyconema barbatum 3 <0.1 4 <0.1 7

Blacktail snailfish Careproctus melanurus 4 <0.1 2 <0.1 6

Bull sculpin Enophrys taurina 5 <0.1 1 <0.1 6

Grass rockfish Sebastes rastrelliger 6 <0.1 0 0 6

Fantail sole Xystreurys liolepis 0 0 5 <0.1 5

Striped seaperch Embiotoca lateralis 0 0 5 <0.1 5

Bay goby Lepidogobius lepidus 0 0 4 <0.1 4

California grenadier Nezumia stelgidolepis 0 0 4 <0.1 4

California halibut Paralichthys californicus 2 <0.1 2 <0.1 4

Hornyhead turbot Pleuronichthys verticalis 0 0 4 <0.1 4

Opaleye Girella nigricans 4 <0.1 0 0 4

Threadfin sculpin Icelinus filamentosus 4 <0.1 0 0 4

Unidentified skate Family Rajidae 0 0 4 <0.1 4

Bat ray Myliobatis californica 0 0 3 <0.1 3

Blackbelly eelpout Lycodes pacificus 1 <0.1 3 <0.1 3

C-O sole Pleuronichthys coenosus 0 0 3 <0.1 3

Plainfin midshipman Porichthys notatus 0 0 3 <0.1 3

Red brotula Brosmophycis marginata 0 0 3 <0.1 3

Spotted cusk-eel Chilara taylori 1 <0.1 2 <0.1 3

California skate Raja inornata 0 0 2 <0.1 2

Island kelpfish Alloclinus holderi 0 0 2 <0.1 2

Petrale sole Eopsetta jordani 0 0 2 <0.1 2

Redbanded rockfish Sebastes babcocki 2 <0.1 0 0 2

Tiger rockfish Sebastes nigrocinctus 1 <0.1 1 <0.1 2

Unidentified witch-eel Family Nettastomatidae 2 <0.1 0 0 2

Barred sand bass Paralabrax nebulifer 0 0 1 <0.1 1

Bluebanded goby Lythrypnus dalli 0 0 1 <0.1 1

California tonguefish Symphurus atricauda 0 0 1 <0.1 1

Table 4 (continued)
9

sites. On average, fish densities were over twice as high at platforms (257.4 individuals/100 m2) compared 

to natural sites (104 individuals/100m2). Rockfishes, of 45 species (at least 45 species at platforms and 43 

species at natural sites) dominated the survey as they comprised 85.8% of all fishes observed (83.8% at platforms and 87.5% at natural sites).

Among the highest density species or species complexes, squarespot, halfbanded, and shortbelly rockfishes, and a complex of young-of-the-year (YOY) rockfishes dominated both platform and natural sites 

(Table 4). Blacksmith, widow rockfish, jack mackerel, unidentified Sebastomus, blackeye goby, and calico 

rockfish rounded out the top ten platform species. A somewhat different suite of species, including pygmy, 

blackeye goby, unidentified Sebastomus, swordspine rockfish, blacksmith, and blue rockfish comprised the 

top ten species by density at natural sites. 

Platform Fish Assemblages

Fish densities were highly variable both between depths at each platform and between platforms (Figures 2a–c). While no single trend described these differences, several patterns were apparent. First, at most 

Santa Barbara Channel and Point Conception-Point Arguello platforms, fish densities were relatively low 

in the first 30 m of the water column. The one exception was at Platform Holly, where a single school of 

jack mackerel in one year dramatically increased the average upper water column density. By contrast, fish 

densities in the shallow waters of the more southerly platforms (Edith, Elly, Ellen, and Eureka) were high, 

primarily driven by high numbers of squarespot rockfish (adults and YOY) and blacksmith YOY (Table 5). 

There was a tendency for densities of fishes to increase and peak in deeper midwater depths or at the 

bottom. Fish densities over shell mounds were usually lower than those at the adjacent platform bottom. In 

addition, fish densities varied greatly between platforms at similar depths. However, there appeared to be 

1

Primarily young-of-the-year.

2

Likely two species, Sebastes miniatus and an undescribed species. 3

Likely two species, Sebastes mystinus and an undescribed species.

Common Name Scientific Name Platforms Natural Sites Total Number

Number Density Number Density

Unidentified catshark Family Scyliorhininidae 1 <0.1 0 0 1

Chameleon rockfish Sebastes phillipsi 0 0 1 <0.1 1

Giant sea bass Stereolepis gigas 0 0 1 <0.1 1

Pacific mackerel Scomber japonicus 0 0 1 <0.1 1

Popeye catalufa Pristigenys serrula 1 <0.1 0 0 1

Rock sole Lepidopsetta sp. 0 0 1 <0.1 1

Rock wrasse Halichoeres semicinctus 1 <0.1 0 0 1

Sablefish Anoplopoma fimbria 0 0 1 <0.1 1

Unidentified Trichiuridae 0 0 1 <0.1 1

Semaphore rockfish Sebastes melanosema 0 0 1 <0.1 1

Shiner perch Cymatogaster aggregata 0 0 1 <0.1 1

Starry flounder Platichthys stellatus 1 <0.1 0 0 1

Swell shark Cephaloscyllium ventriosum 0 0 1 <0.1 1

Unidentified lanternfish Family Myctophidae 0 0 1 <0.1 1

Unidentified snipe eel Family Nemichthyidae 0 0 1 <0.1 1

Total 317,583 257.4 369,559 104.0 687,142

Minimum number of species 128 95 114 128

Table 4 (continued)
10

1000

900

800

700

600

500

400

300

200

100

1000

2000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

1000

2000 2000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

0-30

31-60

Bottom

S.M.

0-30

31-60

61-90

Bottom

S.M.

121-150

>180

Bottom

30-60

61-90

91-120

Bottom

S.M.

0-30

61-90

91-120

121-150

151-180

Bottom

S.M.

0-30

61-9031-60

91-120

121-150

151-180

>180

Bottom

S.M.

31-60

61-90

91-120

121-150

151-180

Bottom

S.M.

31-60

61-90

91-120

121-150

>180

Bottom

S.M.

Irene

Heritage Holly

Hidalgo Harvest

Hondo

Hermosa

Harmony

Density of Fishes (per 100m2) at Platforms

Midwater, Bottom, and Shell Mound

Figure 2a. Density, with standard error bars, of all fishes (per 100 m2) at platform midwaters, bottom, and shell mound, 2004–2009. 

Platforms are listed from northernmost to southernmost. Note that densities on y-axis vary among platforms.
11

1000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

0-30

31-60

No bottom or

shell mound

surveys

No bottom or

shell mound

surveys

No bottom or

shell mound

surveys

No bottom or

shell mound

surveys

No bottom or

shell mound

surveys

No bottom or

shell mound

0-30

surveys

31-60

0-30

31-60

0-30

31-60

0-30

31-60

0-30

31-6061-90

0-30

31-6061-90

Bottom

S.M.

0-30

31-60

Bottom

S.M.

0-30

61-9031-60

91-120

121-150

151-180

>180

Bottom

S.M.

A B C Hillhouse Henry

Habitat Grace Gilda Gail

Density of Fishes (per 100m2) at Platforms

Midwater, Bottom, and Shell Mound

Figure 2b. Density, with standard error bars, of all fishes (per 100 m2) at platform midwaters, bottom, and shell mound, 2004–2009. 

Platforms are listed from northernmost to southernmost. Note that densities on y-axis vary among platforms.
12

Density of Fishes (per 100m2) at Platforms

Midwater, Bottom, and Shell Mound

1000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

1000

2000

900

800

700

600

500

400

300

200

100

1000

900

800

700

600

500

400

300

200

100

0-30

31-60

Bottom

S.M.

0-30

31-60

Bottom

0-30

S.M.

Bottom

S.M.

0-30

61-9031-60

91-120

121-150

151-180

>180

Bottom

S.M.

Edith Elly Ellen Eureka

Figure 2c. Density, with standard error bars, of all fishes (per 100 m2) at platform midwaters, bottom, and shell mound, 2004–2009. 

Platforms are listed from northernmost to southernmost. Note that densities on y-axis vary among platforms. 
13

no geographic pattern to these differences. There was a tendency for fish densities on the bottoms and shell 

mounds of the deepest platforms to be lower than those at shallower structures. 

There are three different fish assemblages, midwaters, bottom, and shell mound, around each platform 

(Figure 3). The fish assemblages in midwaters tended to be similar across platforms. On the other hand, 

substantial differences in fish assemblages were observed among platform bottoms and shell mounds, both 

at each platform and between them. Because of the differences among these three habitats, below we report 

separately upon each assemblage. 

Platform Midwaters

We observed between 5 (Heritage) and 40 (Eureka) fish species in the platform midwaters (Figure 

4, Table 5). The number of species tended to be lowest around the northern-most structures and highest 

around the southern-most ones (Figure 4). The relative paucity of species in the northern platform assemblage was at least partially due to the absence of a suite of warm-temperate taxa, such as blacksmith, sheephead, and garibaldi (Table 5). There did not appear to be a relationship between platform bottom depth and 

number of species in the midwaters (Figure 4). The exceptionally large number of species in the midwaters 

of Platform Eureka is related to the complex structure of Eureka’s midwater jacket and is discussed in more 

detail in Task 2. 

With a few exceptions, midwater fish assemblages were quite similar among platforms and at a platform 

among years (Figures 5–7, Table 5). These assemblages tended to be dominated by juvenile fishes, particularly juvenile rockfishes (e.g., squarespot and widow rockfishes, and bocaccio) and a range of shallow-water 

reef taxa (e.g., cabezon, painted greenling, pile perch, and blue rockfish). The assemblages of four closely 

situated platforms, Edith, Elly, Ellen, and Eureka were somewhat different from those of other structures 

Edith – 49 m 

Ellen – 80 m 

Elly – 77 m 

Eureka – 212 m 

Gail – 224 m 

Gilda – 62 m 

Grace – 96 m 

Harmony – 363 m 

Harvest – 205 m 

Hermosa – 183 m 

Hildalgo – 130 m 

Holly – 64 m 

Hondo – 255 m 

Irene – 73 m 

Combined platforms

Bottom 

Midwater 

Shell Mound 

Platform Midwaters, Bottom, and Shell Mound

Canonical Discriminant Analysis

Centroids Standardized Transformed Data

Discriminant 2 (17%) 

Discriminant 1 (22%) 

-15 -10 -5 0 5 10 15 

-15 

-10 

-5 

0 

5 

10 

15 

20 

25 

Figure 3. A canonical discriminant analysis of platform midwaters, bottom, and shell mound fish assemblages, based on centroids 

of surveys conducted in 2004–2009.
14

Irene

Hidalgo

Harvest

HermosaHarmony

Heritage

Hondo

Holly

A

B

C

Hillhouse

Henry

Habitat

Grace

Gilda

Gail

Edith

Elly

Ellen

Eureka

49 m – Edith

52 m – Henry

57 m – A

58 m – B

58 m – C

58 m – Hillhouse

62 m – Gilda

64 m – Holly

73 m – Irene

77 m – Elly

80 m – Ellen

88 m – Habitat

96 m – Grace

130 m – Hidalgo

183 m Hermosa

205 m – Harvest

212 m – Eureka

224 m – Gail

255 m – Hondo

326 m – Heritage

363 m – Harmony

40

36

32

28

24

20

16

12

8

4

40

36

32

28

24

20

16

12

8

4

Number of Species

Number of Species Ordered by Platform Locations

Number of Species

Number of Species Ordered by Platform Bottom Depth

Number of Species – Platform Midwaters

Figure 4. Number of species observed in the midwaters of platforms, 2004–2009. Platforms are listed first from northernmost to 

southernmost and then from shallowest to deepest.
15

A

B 

C 

Edith 

Ellen 

Elly 

Eureka 

Gail 

Gilda 

Grace 

Habitat 

Harmony 

Harvest 

Henry 

Heritage 

Hermosa 

Hildalgo 

Hillhouse 

Holly 

Hondo 

Irene 

Platform Midwaters 

Canonical Discriminant Analysis

Standardized Transformed Densities 

Discriminant 2 (17%) 

Discriminant 1 (33%) 

-4 -3 -2 -1 0 1 2 3 4 5 

-6 

-5 

-4 

-3 

-2 

-1 

0 

1 

2 

3 

Edith, Ellen and Elly 

Eureka 

Rest of Platforms

Species Cluster 

Average Density 

All Platform Midwaters Standardized Transformed Densities 

1 2 3 

-0.4 

-0.2 

0 

0.2 

0.4 

0.6 

0.8 

1 

Figure 5. A canonical discriminant analysis of platform midwaters fish assemblages, by year, 2004–2009.

Figure 6. A comparison of densities of the three midwater species clusters shown in Figure 7. 
16

(Figures 5–7, Table 5). Edith, Elly, and Ellen harbored particularly high densities of juvenile blacksmith. A 

variety of both juvenile and adult deeper-water rockfishes, that were absent or rare around other platform 

midwaters, occupied Platform Eureka (see Task 2). 

Platform Bottoms

We observed between 5 (Harmony) and 38 (Holly) fish species around platform bottoms (Figure 8, 

Table 6). While there appears to be little relationship between species richness and platform location, bottom 

depth was an important factor as there was a clear peak in species numbers at platforms situated in about 

60–80 m and perhaps a second peak in about 220 m (Figure 8).

Halfbanded rockfish

Blacksmith

Blacksmith YOY

Greenspotted rockfish

Greenblotched rockfish

Pinkrose rockfish

Bocaccio

Widow rockfish

Widow rockfish YOY

Starry rockfish

Swordspine rockfish

Honeycomb rockfish

Rosy rockfish

Sebastomus

Unidentified rockfishes

Bocaccio YOY

Flag rockfish

Lingcod

Lingcod YOY

Sharpnose surfperch

Olive rockfish

Pile perch

Calico rockfish

Vermilion rockfish

Kelp greenling

Treefish

Cabezon

Unidentified rockfishes YOY

Squarespot rockfish

Squarespot rockfish YOY

Blue rockfish

Copper rockfish

Gopher rockfish

Kelp rockfish

Shortbelly rockfish

Sebastomus YOY

Painted greenling

Painted greenling YOY

14 16 18 20 22 24

Platform Midwaters

More typical of 

platforms Edith, Elly, 

and Ellen midwaters

More typical of

Platform Eureka

midwaters

More typical of

all other platform

midwaters

Figure 7. A cluster analysis of the characteristic species of platform midwaters, 2004–2009.
17

Table 5. Numbers and densities (average number per 100 m2) of fish species observed in the midwaters of platforms, 2004–2009. Rankings of total counts and average densities may differ because densities are averages of transect densities and area surveyed varied among 

transects. Young-of-the-year (YOY) and older fish are listed separately.

PLATFORM IRENE (Surveyed 2004–6, 2008, 2009)

Species Number Density

Widow rockfish YOY 5,431 211.1

Unidentified rockfish YOY 3,316 126.1

Shortbelly rockfish YOY 2,100 78.8

Squarespot rockfish YOY 1,487 55.8

Widow rockfish 987 33.1

Olive rockfish YOY 610 22.9

Northern anchovy 300 16.9

Painted greenling 102 4.3

Unidentified rockfishes 67 2.4

Painted greenling YOY 65 2.8

Sebastomus sp. 11 0.4

Sebastomus sp. YOY 10 0.4

Copper rockfish 7 0.3

Blue rockfish 6 0.3

Lingcod YOY 4 0.1

Unidentified fishes 3 0.1

Yellowtail rockfish YY 3 0.1

Blacksmith YOY 1 <0.1

Bocaccio YOY 1 <0.1

Cabezon 1 <0.1

Flag rockfish YOY 1 <0.1

Total 14,513

Minimum number of species 15

Total rockfish YOY 12,959

Total rockfishes 13,970

Rockfish YOY comprised 89.3% of all fishes surveyed

All rockfishes comprised 96.3% of all fishes surveyed

PLATFORM HIDALGO (Surveyed 2004–2006, 2009)

Species Number Density

Unidentified rockfish YOY 11,406 205.3

Widow rockfish YOY 175 4.1

Squarespot rockfish 123 2.6

Unidentified rockfish 122 2.4

Painted greenling YOY 64 1.4

Painted greenling 52 1.1

Unidentified fishes 17 0.4

Sebastomus sp. 11 0.2

Widow rockfish 10 0.2

Squarespot rockfish YOY 8 0.2

Sebastomus sp. YOY 7 0.1

Flag rockfish 5 <0.1

Flag rockfish YOY 5 0.1

Halfbanded rockfish 2 <0.1

Pygmy rockfish 2 <0.1

Bocaccio 1 <0.1

Bocaccio YOY 1 <0.1

Cabezon 1 <0.1

Greenspotted rockfish 1 <0.1

Total 12,013

Minimum number of species 9

Total rockfish YOY 11,602

Total rockfishes 11,879

Rockfish YOY comprised 96.6% of all fishes surveyed

All rockfishes comprised 98.9% of all fishes surveyed

PLATFORM HARVEST (Surveyed 2004)

Species Number Density

Squarespot rockfish 247 9.5

Widow rockfish 191 7.8

Sharpchin rockfish 169 4.8

Painted greenling 72 2.5

Painted greenling YOY 21 0.9

Unidentified rockfish YOY 19 0.7

Widow rockfish YOY 10 0.4

Unidentified rockfish 6 0.2

Sebastomus sp. 4 0.1

Darkblotched rockfish 3 <0.1

Flag rockfish 3 0.1

Unidentified sculpin 3 0.1

Halfbanded rockfish 2 <0.1

Squarespot rockfish 2 <0.1

Blue rockfish 1 <0.1

Blue rockfish YOY 1 <0.1

Cabezon 1 <0.1

Unidentified Icelinus 1 <0.1

Kelp rockfish 1 <0.1

Pacific argentine 1 <0.1

Treefish YOY 1 <0.1

Total 759

Minimum number of species 15

Total rockfish YOY 33

Total rockfishes 660

Rockfish YOY comprised 4.3% of all fishes surveyed

All rockfishes comprised 87.0% of all fishes surveyed

PLATFORM HERMOSA (Surveyed 2006)

Species Number Density

Widow rockfish YOY 237 11.4

Widow rockfish 96 4.7

Painted greenling 81 4.0

Unidentified rockfish 81 3.5

Squarespot rockfish 55 2.2

Unidentified rockfish YOY 37 1.9

Painted greenling YOY 18 1.0

Sebastomus sp. 8 0.4

Cabezon 5 0.3

Flag rockfish 4 0.2

Blue rockfish 3 0.2

Bocaccio 1 <0.1

Darkblotched rockfish 1 <0.1

Rosy rockfish 1 <0.1

Squarespot rockfish YOY 1 <0.1

Unidentified fish 1 <0.1

Total 630

Minimum number of species 9

Total rockfish YOY 275

Total rockfishes 525

Rockfish YOY comprised 43.7% of all fishes surveyed

All rockfishes comprised 83.3% of all fishes surveyed
18

PLATFORM HARMONY (Surveyed 2004)

Species Number Density

Squarespot rockfish 39 1.8

Blue rockfish 17 1.0

Darkblotched rockfish 13 0.3

Squarespot rockfish YOY 8 0.4

Bocaccio YOY 7 0.3

Unidentified rockfish YOY 7 0.4

Painted greenling 6 0.3

Kelp rockfish 5 0.3

Painted greenling YOY 4 0.2

Unidentified rockfish 4 0.1

Widow rockfish YOY 4 0.2

Unidentified fishes 3 0.1

Aurora rockfish 2 <0.1

Bocaccio 2 <0.1

Sebastomus sp. 2 <0.1

Blackgill rockfish 1 <0.1

Sharpchin rockfish 1 <0.1

Splitnose rockfish 1 <0.1

Yelloweye rockfish 1 <0.1

Total 127

Minimum number of species 14

Total rockfish YOY 26

Total rockfishes 114

Rockfish YOY comprised 20.4% of all fishes surveyed

All rockfishes comprised 89.8% of all fishes surveyed

PLATFORM HERITAGE (Surveyed 2008)

Species Number Density

Bank rockfish 179 8.4

Pinkrose rockfish 22 1.0

Painted greenling 2 <0.1

Unidentified fishes 2 <0.1

Unidentified rockfish 2 <0.1

Sebastomus sp. 1 <0.1

Squarespot rockfish 1 <0.1

Unidentified rockfish YOY 1 <0.1

Total 210

Minimum number of species 5

Total rockfish YOY 1

Total rockfishes 206

Rockfish YOY comprised 0.5% of all fishes surveyed

All rockfishes comprised 98.1% of all fishes surveyed

PLATFORM HONDO (Surveyed 2004, 2006, 2008)

Species Number Density

Squarespot rockfish 704 19.4

Bank rockfish 558 8.6

Blacksmith 271 10.1

Northern anchovy 226 2.0

Widow rockfish 107 2.5

Squarespot rockfish YOY 56 1.1

Unidentified rockfish YOY 41 0.7

Widow rockfish YOY 40 1.3

Painted greenling 33 0.8

Bocaccio 31 0.8

Pinkrose rockfish 24 0.3

Sebastomus sp. 15 0.2

Painted greenling YOY 14 0.4

Unidentified rockfish 13 0.3

Bocaccio YOY 8 0.3

Bank rockfish YOY 5 <0.1

Blue rockfish 5 0.2

Darkblotched rockfish 5 <0.1

Flag rockfish 5 <0.1

Sharpchin rockfish 5 0.1

Cabezon 4 <0.1

Unidentified fishes 3 <0.1

Olive rockfish 2 <0.1

Sebastomus YOY 2 <0.1

Unidentified Icelinus 1 <0.1

Kelp greenling 1 <0.1

Shortbelly rockfish 1 <0.1

Yellowtail rockfish 1 √

Total 2,181

Minimum number of species 18

Total rockfish YOY 152

Total rockfishes 1,628

Rockfish YOY comprised 7.0% of all fishes surveyed

All rockfishes comprised 74.6% of all fishes surveyed

PLATFORM HOLLY (Surveyed 2004–2009)

Species Number Density

Jack mackerel 10,650 457.6

Squarespot rockfish 1,660 38.5

Unidentified rockfish YOY 1,401 37.7

Blacksmith YOY 534 12.5

Squarespot rockfish YOY 261 13.7

Widow rockfish 239 13.7

Painted greenling 186 5.5

Painted greenling YOY 110 4.2

Calico rockfish 89 1.3

Widow rockfish YOY 84 3.9

Blacksmith 53 2.0

Blackeye goby 41 0.6

Copper rockfish 35 1.0

Olive rockfish 27 1.4

Bocaccio YOY 21 0.4

Halfbanded rockfish 20 0.3

Halfbanded rockfish YOY 20 0.3

Rosy rockfish 17 0.2

Unidentified Sebastomus 16 0.2

Kelp rockfish 14 1.2

Blue rockfish 12 0.4

Pile perch 11 0.8

Lingcod YOY 10 0.2

Bluebanded ronquil 8 0.1

Kelp greenling 7 0.2

Flag rockfish 6 <0.1

Sebastomus YOY 6 <0.1

Unidentified rockfish 6 0.2

Blue rockfish YOY 4 0.4

Sharpnose seaperch 4 0.3

Cabezon 3 0.2

Copper rockfish YOY 3 <0.1

Bocaccio 2 <0.1

Table 5 (continued)
19

Calico rockfish 2 <0.1

Gopher rockfish 2 <0.1

Honeycomb rockfish 2 <0.1

Shortspine combfish 2 <0.1

Unidentified fishes 2 <0.1

Unidentified ronquil 2 <0.1

Vermilion rockfish 2 <0.1

Brown rockfish 1 <0.1

Unidentified combfish 1 <0.1

Flag rockfish YOY 1 <0.1

Lingcod 1 <0.1

Olive rockfish YOY 1 <0.1

Pink seaperch 1 <0.1

Unidentified surfperch 1 <0.1

Treefish 1 <0.1

Unidentified sanddab 1 <0.1

Unidentified sculpin 1 <0.1

Yelloweye rockfish YOY 1 <0.1

Total 15,585

Minimum number of species 30

Total rockfish YOY 1,805

Total rockfishes 3,956

Rockfish YOY comprised 11.6% of all fishes surveyed

All rockfishes comprised 25.4% of all fishes surveyed

PLATFORM A (Surveyed 2004, 2006, 2007)

Species Number Density

Unidentified rockfish YOY 218 8.5

Shortbelly rockfish YOY 206 8.5

Sebastomus YOY 147 5.8

Blacksmith 142 6.5

Olive rockfish 49 1.9

Blue rockfish 29 1.1

Pile perch 29 1.2

Widow rockfish 23 0.9

Squarespot rockfish YOY 21 0.8

Sharpnose seaperch 17 0.7

Painted greenling 15 0.6

Painted greenling YOY 15 0.6

Unidentified fishes 12 0.5

California sheephead 10 0.5

Bocaccio YOY 9 0.4

Widow rockfish YOY 8 0.3

Unidentified surfperch 7 0.3

Squarespot rockfish 5 0.2

Unidentified rockfish 4 0.2

Brown rockfish 3 0.1

Kelp rockfish 2 <0.1

Rubberlip seaperch 2 <0.1

Blacksmith YOY 1 <0.1

Copper rockfish 1 <0.1

Gopher rockfish 1 <0.1

Halfbanded rockfish YOY 1 <0.1

Starry rockfish YOY 1 <0.1

White seaperch 1 <0.1

Total 982

Minimum number of species 19

Total rockfish YOY 611

Total rockfishes 728

Rock YOY comprised 62.2% of all fishes surveyed

All rockfishes comprised 74.1% of all fishes surveyed.

PLATFORM B (Surveyed 2004 and 2007)

Species Number Density

Unidentified rockfish YOY 215 9.6

Blacksmith 79 4.1

Sharpnose seaperch 35 1.7

Olive rockfish 22 1.0

Kelp bass 19 1.0

Halfmoon 16 0.9

Unidentified rockfish 16 0.7

Blacksmith YOY 15 0.9

Blue rockfish 12 0.5

Pile perch 11 0.5

California sheephead 9 0.5

White seaperch 8 0.4

Painted greenling 7 0.3

Squarespot YOY 5 0.2

Widow rockfish YOY 5 0.2

Painted greenling 4 0.2

Unidentified surfperch 4 0.2

Brown rockfish 3 0.1

Copper rockfish 3 0.1

Kelp rockfish YOY 3 0.1

Kelp rockfish 2 0.1

Garibaldi 1 <0.1

Rubberlip seaperch 1 <0.1

Senorita 1 <0.1

Unidentified fishes 1 <0.1

Total 497

Minimum number of species 19

Total rockfish YOY 228

Total rockfishes 286

Rockfish YOY comprised 46.0% of all fishes surveyd

All rockfishes comprised 57.5% of all fishes surveyed. 

PLATFORM C (Surveyed 2004, 2007)

Species Number Density

Unidentified rockfish YOY 518 23.2

Widow rockfish 373 16.6

Widow rockfish YOY 210 9.3

Blue rockfish 139 6.3

Squarespot rockfish YOY 89 4.0

Sebastomus YOY 47 2.1

Blacksmith 46 2.5

Blacksmith YOY 38 1.9

Olive rockfish 28 1.3

Painted greenling 26 1.2

Painted greenling YOY 21 1.0

Pile perch 20 1.0

White seaperch 18 0.9

Sharpnose seaperch 15 0.7

Copper rockfish YOY 7 0.3

Halfmoon 6 0.3

Bocaccio YOY 4 0.2

Kelp rockfish 4 0.2

Table 5 (continued)
20

Blackeye goby 3 0.1

Blue rockfish YOY 3 0.1

California sheephead 3 0.1

Speckled rockfish YOY 2 <0.1

Squarespot rockfish 2 <0.1

Unidentified rockfish 2 <0.1

Gopher rockfish 1 <0.1

Wolf-eel 1 <0.1

Total 1,626

Minimum number of species 19

Total rockfish YOY 1,399

Total rockfishes 1,429

Rockfish YOY comprised 86.0% of all fishes surveyed

All rockfishes comprised 87.8% of all fishes surveyed

PLATFORM HILLHOUSE (Surveyed 2004, 2007, 2009)

Species Number Density

Blacksmith YOY 569 28.2

Jack mackerel 330 12.8

Squarespot rockfish 81 3.1

Unidentified rockfish YOY 74 2.7

Unidentified surfperch 55 2.8

Blacksmith 41 2.0

Painted greenling 27 1.1

Squarespot rockfish YOY 24 0.9

Widow rockfish 17 0.6

Pile perch 13 0.6

Widow rockfish YOY 8 0.3

Olive rockfish 6 0.2

Blue rockfish 5 0.2

Halfbanded rockfish YOY 4 0.2

Kelp bass 3 0.2

Unidentified rockfish 3 0.1

Cabezon 2 0.1

Kelp rockfish 2 <0.1

Sebastomus YOY 2 <0.1

Sharpnose seaperch 2 <0.1

Blue rockfish YOY 1 <0.1

Copper rockfish 1 <0.1

Grass rockfish 1 <0.1

Rubberlip seaperch 1 <0.1

Unidentified Sebastomus 1 <0.1

Sheephead 1 <0.1

White seaperch 1 <0.1

Total 1,275

Minimum number of species 19

Total rockfish YOY 113

Total rockfishes 230

Rockfish YOY comprised 8.9% of all fishes surveyed

All rockfishes comprised 18.0% of all fishes surveyed

PLATFORM HENRY

Species Number Density

Unidentified rockfish YOY 75 12.5

Blacksmith YOY 48 9.1

Squarespot rockfish YOY 12 2.0

Widow rockfish YOY 5 0.8

Painted greenling 2 0.4

Blue rockfish YOY 1 0.2

Cabezon 1 0.2

Painted greenling YOY 1 0.2

Pile perch 1 0.1

Total 146

Minimum number of species 7

Total rockfish YOY 93

Total rockfishes 93

Rockfish YOY comprised 63.7% of all fishes surveyed

All rockfishes comprised 63.7% of all fishes surveyed

PLATFORM HABITAT (Surveyed 2004, 2007, 2009)

Species Number Density

Squarespot rockfish 1,094 30.9

Blacksmith YOY 666 26.1

Widow rockfish 565 16.1

Squarespot YOY 212 6.0

Widow rockfish YOY 163 4.6

Halfbanded rockfish 155 4.4

Unidentified rockfish YOY 100 3.0

Bocaccio YOY 85 2.4

Painted greenling 75 2.5

Blacksmith 52 1.9

Painted greenling YOY 35 1.1

Olive rockfish 25 0.8

Blue rockfish 24 0.7

Bocaccio 24 0.7

Halfbanded rockfish YOY 22 0.6

Unidentified rockfish 18 0.6

Sebastomus YOY 112 0.4

Copper rockfish 7 0.2

Sebastomus sp. 6 0.2

Flag rockfish 5 0.1

Unidentified surfperch 4 0.1

Unidentified fishes 4 0.1

Copper rockfish YOY 3 0.1

Halfmoon 3 0.1

Cabezon 2 <0.1

Calico rockfish 2 <0.1

Blackeye goby 1 <0.1

Blue rockfish YOY 1 <0.1

Gopher rockfish 1 <0.1

Kelp rockfish 1 <0.1

Rosy rockfish 1 <0.1

Total 3,368

Minimum number of species 18

Total rockfish YOY 598

Total rockfishes 2,526

Rockfish YOY comprised 17.8% of all fishes surveyed

All rockfishes comprised 75.0% of all fishes surveyed

PLATFORM GRACE (Surveyed 2004, 2005, 2007–2009)

Species Number Density

Widow rockfish YOY 8,099 225.3

Widow rockfish 2.151 57.5

Squarespot rockfish 1,868 37.3

Unidentified rockfish YOY 1,689 44.0

Squarespot rockfish 955 18.6

Table 5 (continued)
21

Bocaccio 182 4.8

Unidentified rockfish 163 3.2

Bocaccio YOY 145 2.8

Blacksmith 105 3.6

Painted greenling 25 0.6

Flag rockfish 24 0.5

Painted greenling YOY 24 0.6

Sebastomus sp. 18 0.4

Kelp rockfish 15 0.5

Blue rockfish 14 0.4

Rosy rockfish 11 0.2

Sebastomus YOY 8 0.3

Blacksmith YOY 6 0.2

Copper rockfish 6 0.2

Unidentified fishes 5 0.1

Cabezon 3 <0.1

Vermilion rockfish 3 <0.1

Greenspotted rockfish 2 <0.1

Olive rockfish 1 <0.1

Pygmy rockfish 1 <0.1

Starry rockfish 1 <0.1

Starry rockfish YOY 1 <0.1

Treefish 1 <0.1

Unidentified rockfish 1 <0.1

Total 15,527

Minimum number of species 17

Total rockfish YOY 10,897

Total rockfishes 15,358

Rockfish YOY comprised 71.0% of all fishes surveyed

All rockfishes comprised 98.9% of all fishes surveyed

PLATFORM GILDA (Surveyed 2004, 2006–2009)

Species Number Density

Shortbelly rockfish YOY 1,316 53.9

Unidentified rockfish YOY 501 20.6

Shortbelly rockfish 500 20.5

Squarespot rockfish YOY 156 6.9

Sharpnose seaperch 81 3.6

Painted greenling 61 2.8

Blacksmith YOY 35 2.1

Painted greenling YOY 27 1.1

Halfmoon 22 1.1

Blacksmith 18 0.9

Unidentified rockfish 16 0.7

Squarespot rockfish 15 0.7

Kelp rockfish 13 0.7

Pile perch 10 0.5

Cabezon 7 0.3

Sebastomus YOY 7 0.2

Copper rockfish YOY 5 0.3

Unidentified surfperch 4 0.2

Copper rockfish 2 <0.1

Opaleye 2 <0.1

Chilipepper YOY 1 <0.1

Grass rockfish 1 <0.1

Kelp greenling 1 <0.1

Olive rockfish 1 <0.1

Olive rockfish YOY 1 <0.1

Rosy rockfish YOY 1 <0.1

Stripetail rockfish 1 <0.1

Treefish 1 <0.1

Treefish YOY 1 <0.1

Unidentified fishes 1 <0.1

Total 2,808

Minimum number of species 18

Total rockfish YOY 1,989

Total rockfishes 2,539

Rockfish YOY comprised 70.8% of all fishes surveyed

All rockfishes comprised 90.4% of all fishes surveyed

PLATFORM GAIL (Surveyed 2004–2009)

Species Number Density

Squarespot rockfish 911 7.9

Unidentified rockfish YOY 805 5.8

Bocaccio YOY 624 4.8

Squarespot rockfish YOY 533 3.7

Bocaccio 525 3.7

Blacksmith 276 2.6

Widow rockfish YOY 275 3.0

Blacksmith YOY 99 0.9

Halfmoon 90 0.8

Unidentified rockfish 84 0.5

Painted greenling 76 0.6

Flag rockfish 58 0.4

Painted greenling YOY 50 0.3

Pinkrose rockfish 33 0.2

Sebastomus sp. 29 0.2

Unidentified fishes 26 0.2

Sebastomus YOY 18 0.1

Flag rockfish YOY 17 0.1

Widow rockfish 15 0.2

Cabezon 11 <0.1

Darkblotched rockfish 7 <0.1

Kelp greenling 3 <0.1

Pacific hake 3 <0.1

Bank rockfish 2 <0.1

Copper rockfish 2 <0.1

Greenblotched rockfish 2 <0.1

Greenspotted rockfish 2 <0.1

Sharpchin rockfish 2 <0.1

Unidentified sculpin 2 <0.1

Blue rockfish YOY 1 <0.1

Gopher rockfish 1 <0.1

Greenblotched rockfish YOY 1 <0.1

Kelp bass 1 <0.1

Northern anchovy 1 <0.1

Olive rockfish 1 <0.1

Shortbelly rockfish 1 <0.1

Speckled rockfish YOY 1 <0.1

Swordspine rockfish 1 <0.1

Treefish YOY 1 <0.1

Total 4,590

Minimum number of species 27

Total rockfish YOY 2,276

Total rockfishes 3,952

Rockfish YOY comprised 49.6% of all fishes surveyed

All rockfishes comprised 86.1% of all fishes surveyed

Table 5 (continued)
22

PLATFORM EDITH (Surveyed 2005–2009)

Species Number Density

Blacksmith YOY 10,982 548.0

Jack mackerel 722 32.2

Blacksmith 368 18.3

Squarespot rockfish YOY 357 11.2

Unidentified fishes 223 6.7

Unidentified rockfish YOY 212 6.1

Halfbanded rockfish 161 7.7

California sheephead 69 3.0

Garibaldi 54 2.5

Unidentified rockfish 43 1.2

Kelp rockfish YOY 35 1.0

Sebastomus YOY 27 0.9

Sharpnose seaperch 21 0.6

Painted greenling 20 0.8

Squarespot rockfish 19 0.6

Kelp rockfish 17 0.6

Cabezon 16 0.5

White seaperch 15 0.5

Painted greenling YOY 14 0.5

Senorita 13 0.6

Honeycomb rockfish YOY 4 0.1

Sharpchin rockfish 4 0.2

Pile perch 3 0.1

Unidentified Sebastomus 2 <0.1

Treefish YOY 2 <0.1

Flag rockfish YOY 1 <0.1

Honeycomb rockfish 1 <0.1

Kelp bass 1 <0.1

Widow rockfish YOY 1 <0.1

Wolf-eel 1 <0.1

Total 13,408

Minimum number of species 21

Total rockfish YOY 639

Total rockfishes 886

Rockfish YOY comprised 4.8% of all fishes surveyed

All rockfishes comprised 6.6% of all fishes surveyed

PLATFORM ELLY (Surveyed 2005–2009)

Species Number Density

Squarespot rockfish 7,920 243.5

Blacksmith YOY 2,584 136.3

Squarespot rockfish YOY 2,372 76.1

Unidentified rockfish YOY 1,970 62.7

Widow rockfish 151 4.5

Halfmoon 65 3.5

Blacksmith 55 1.9

Halfbanded rockfish 48 1.8

Sebastomus YOY 36 1.5

Bluebanded ronquil 35 1.0

Cabezon 33 1.3

Painted greenling 27 1.0

Widow rockfish YOY 21 0.7

California sheephead 20 1.0

Sharpnose seaperch 11 0.4

Kelp rockfish 10 0.4

Garibaldi 7 0.4

Unidentified fishes 6 0.2

Blue rockfish YOY 5 0.2

Shortbelly rockfish YOY 5 0.2

Gopher rockfish 4 0.1

Unidentified rockfish 4 0.1

Blue rockfish 3 <0.1

Painted greenling YOY 3 <0.1

Starry rockfish YOY 3 <0.1

Copper rockfish 2 <0.1

Lingcod 2 <0.1

Opaleye 2 <0.1

Sebastomus sp. 2 <0.1

Bocaccio 1 <0.1

Bocaccio YOY 1 <0.1

Grass rockfish 1 <0.1

Halfbanded rockfish YOY 1 <0.1

Olive rockfish 1 <0.1

Pile perch 1 <0.1

Rosy rockfish YOY 1 <0.1

Starry rockfish 1 <0.1

Yelloweye rockfish YOY 1 <0.1

Total 15,415

Minimum number of species 27

Total rockfish YOY 4,416

Total rockfishes 12,564

Rockfish YOY comprised 28.6% of all fishes surveyed

All rockfishes comprised 81.5% of all fishes surveyed

Table 5 (continued)
23

PLATFORM ELLEN (Surveyed 2005–2009)

Species Number Density

Squarespot rockfish YOY 9,140 206.5

Squarespot rockfish 4,440 102.0

Blacksmith YOY 2,505 192.4

Unidentified rockfish YOY 2,184 56.5

Widow rockfish 2,102 55.4

Widow rockfish YOY 502 13.2

Unidentified fishes 452 10.5

Blacksmith 288 9.2

Kelp rockfish 70 1.7

Sebastomus YOY 65 1.5

Bocaccio 62 1.6

Jack mackerel 55 1.3

Unidentified rockfish 52 1.3

Cabezon 40 1.0

California sheephead 38 1.0

Painted greenling 17 0.4

Sharpnose seaperch 14 0.4

Painted greenling YOY 10 0.2

Bocaccio YOY 7 0.2

Blue rockfish 6 0.2

Garibaldi 6 0.2

Copper rockfish 5 0.1

Halfmoon 5 0.3

Gopher rockfish 3 <0.1

Starry rockfish YOY 3 <0.1

Halfbanded rockfish 2 <0.1

Pile perch 2 <0.1

Lingcod 1 <0.1

Northern anchovy 1 <0.1

Rock wrasse 1 <0.1

Unidentified surfperch 1 <0.1

Treefish YOY 1 <0.1

Unidentified sculpin 1 <0.1

Total 22,081

Minimum number of species 22

Total rockfish YOY 11,902

Total rockfishes 18,592

Rockfish YOY comprised 53.9% of all fishes surveyed

All rockfishes comprised 84.2% of all fishes surveyed

PLATFORM EUREKA (Surveyed 2005–2009)

Species Number Density

Squarespot rockfish 12,128 92.0

Squarespot rockfish YOY 5,875 47.4

Unidentified rockfish YOY 4,585 32.8

Blacksmith YOY 838 9.6

Widow rockfish 762 4.7

Blacksmith 604 7.0

Unidentified rockfish 566 4.0

Jack mackerel 530 6.4

Speckled rockfish 392 2.5

Speckled rockfish YOY 252 1.8

Sebastomus sp. 179 1.2

Blue rockfish 167 1.4

Widow rockfish YOY 157 1.1

Bocaccio YOY 100 0.7

Bank rockfish 91 0.6

Copper rockfish 82 0.7

Kelp rockfish 75 0.7

Rosy rockfish 68 0.5

Dwarf-red rockfish YOY 62 0.4

Pinkrose rockfish 61 0.4

Greenblotched rockfish 58 0.4

Flag rockfish 55 0.4

Dwarf-red rockfish 54 0.4

Pygmy rockfish 42 0.3

Unidentified fishes 30 0.3

Bocaccio 29 0.2

Cabezon 25 0.2

Greenspotted rockfish 24 0.1

Starry rockfish 24 0.2

Garibaldi 23 0.2

California sheephead 22 0.2

Painted greenling 21 0.2

Honeycomb rockfish 19 0.1

Starry rockfish YOY 17 0.1

Bank rockfish YOY 15 <0.1

Darkblotched rockfish 15 <0.1

Sebastomus YOY 15 <0.1

Gopher rockfish 13 <0.1

Shortbelly rockfish YOY 13 <0.1

Freckled rockfish 10 <0.1

Painted greenling YOY 7 <0.1

Swordspine rockfish 7 <0.1

Flag rockfish YOY 6 <0.1

Blue rockfish YOY 4 <0.1

Blackeye goby 3 <0.1

Grass rockfish 3 <0.1

Rosethorn rockfish 3 <0.1

Sharpchin rockfish 2 <0.1

Vermilion rockfish 2 <0.1

Blackgill rockfish 1 <0.1

Halfbanded rockfish YOY 1 <0.1

Kelp rockfish YOY 1 <0.1

Popeye Catalufa 1 <0.1

Treefish 1 <0.1

Yelloweye rockfish 1 <0.1

Total 28,141

Minimum number of species 40

Total rockfish YOY 11,103

Total rockfishes 26,037

Rockfish YOY comprised 39.5% of all fishes surveyed

All rockfishes comprised 92.5% of all fishes surveyed

Table 5 (continued)
24

Irene

Hidalgo

Harvest

HermosaHarmony

Heritage

Hondo

Holly

Grace

Gilda

Gail

Edith

Elly

Ellen

Eureka

49 m – Edith

62 m – Gilda

64 m – Holly

73 m – Irene

77 m – Elly

80 m – Ellen

96 m – Grace

130 m – Hidalgo

183 m Hermosa

205 m – Harvest

212 m – Eureka

224 m – Gail

255 m – Hondo

326 m – Heritage

363 m Harmony

40

36

32

28

24

20

16

12

8

4

40

36

32

28

24

20

16

12

8

4

Number of Species

Number of Species Ordered by Platform Locations

Number of Species

Number of Species Ordered by Platform Bottom Depth

Number of Species – Platform Bottom

Figure 8. Number of species observed at bottoms of platforms, 2004–2009. Platforms are listed first from northernmost to southernmost and then from shallowest to deepes
25

Edith – 49 m 

Ellen – 80 m 

Elly – 77 m 

Eureka – 212 m 

Gail – 224 m 

Gilda – 62 m 

Grace – 96 m 

Harmony – 363 m 

Harvest – 205 m 

Hermosa – 183 m 

Hildalgo – 130 m 

Holly – 64 m 

Hondo – 255 m 

Irene – 73 m 

Platform Bottom

Canonical Discriminant Analysis

Standardized Transformed Densities

Discrimant 2 (23%) 

Discriminant 1 (29%) 

-20 -15 -10 -5 0 5 10 15 20 

-20 

-15 

-10 

-5 

0 

5 

10 

15 

20 

25 

Elly-Ellen

Middle Depths

Shallowest Depths Deepest Depths

Figure 9. A canonical discriminant analysis of platform bottom fish assemblages, by year, 2004–2009.

At each platform, the bottom fish assemblage was similar over the survey period (Figure 9). Bottom 

depth was a major factor in structuring bottom fish assemblages; the platforms formed three or perhaps 

four groups (Figure 9). Of particular note was the close similarity in the species assemblages of Elly and 

Ellen, platforms that lie within a few hundred meters of each other. We observed three recurrent groups of 

fishes that tended to be found together; these were 1) shallow- and 2) deep-bottom assemblages, and 3) one 

that was composed of both shallow and mid-depth taxa (Figures 10–11). In both numbers and densities, 

rockfishes comprised the vast majority of species (Figure 11, Table 6), although sea perches, blackeye goby, 

cabezon, and several hexagrammids (e.g., lingcod and painted greenling) were also characteristic of some 

platforms. 

Platform Shell Mounds

We observed between 9 (Hermosa, Harvest, and Harmony) and 30 (Holly) fish species around platform shell mounds (Figure 12, Table 7). As with the platform bottom assemblages, two peaks in taxa number 

were observed, one in moderate depths and another in deeper waters. 

We observed little change in species assemblages at any platform over the survey period (Figure 13). 

Similar to that living in the platform bottom habitat, the shell mound species composition were driven by 

bottom depth (Figures 13–15). Also similar to the platform bottom assemblages, there were three recurrent 

groups of species, a shallow and a deep one, and one shared by shallow and middle-depth bottom species. 

Rockfishes were again the dominant taxonomic group, although other bottom dwellers, including poachers, various flatfishes, and combfishes were also typical. There was considerable overlap of characteristic 

species with the bottom habitats; these included the YOY of several rockfish species, adults of a number of 

rockfishes, spotted scorpionfish, and lingcod. However, also typical of shell mounds (and less abundant at 

platform bottoms) were species characteristic of lower relief. These included bluebarred ronquil, cowcod 

YOY, longspine and shortspine combfishes, poachers, and Dover sole. 
26

All Depths Platform Bottoms

Standardized Transformed Densities

Shallow 

Middle 

Deep 

Average Density 

Species Cluster 

1 2 3

-0.8 

-0.6 

-0.4 

-0.2 

0 

0.2 

0.4 

0.6 

0.8 

Figure 10. A comparison of densities of the three bottom species clusters shown in Figure 11.

Sharpnose seaperch

Gopher rockfish

Pile perch

Cabezon

Squarespot rockfish YOY

Blackeye goby Spotted scorpionfish

Painted greenling YOY Sebastomus YOY

Shortspine combfish

Widow rockfish

Canary rockfish Swordspine rockfish

Sebastomus spp.

Unidentified rockfishes

Kelp greenling

Pink seaperch

Calico rockfish

Olive rockfish

Lingcod YOY

Unidentified sanddab

Painted greenling

Vermilion rockfish

Blue rockfish

Brown rockfish

Copper rockfish

Halfbanded rockfish YOY

Halfbanded rockfish

Starry rockfish Squarespot rockfish

Flag rockfish

Honeycomb rockfish

Rosy rockfish

Treefish

Unidentified rockfishes YOY

Bocaccio YOY

Bluebarred ronquil

Darkblotched rockfish

Greenspotted rockfish

Greenstriped rockfish

Lingcod Greenblotched rockfish

Pinkrose rockfish

Bocaccio

Cowcod

Mexican rockfish

2 4 6 8 10

Platform Bottoms All Depths 

More typical

of both shallow and

middle-depth

platform bottoms

More typical

of shallow

platform bottoms

More typical

of deeper-depth

platform bottoms

Figure 11. A cluster analysis of the characteristic species of platform bottoms, 2004–2009.
27

Irene

Hidalgo

Harvest

HermosaHarmony

Hondo

Holly

Grace

Gilda

Gail

Edith

Elly

Ellen

Eureka

49 m – Edith

62 m – Gilda

64 m – Holly

73 m – Irene

77 m – Elly

80 m – Ellen

96 m – Grace

130 m – Hidalgo

183 m Hermosa

205 m – Harvest

212 m – Eureka

224 m – Gail

255 m – Hondo

363 m Harmony

32

28

24

20

16

12

8

4

32

28

24

20

16

12

8

4

Number of Species

Number of Species Ordered by Platform Locations

Number of Species

Number of Species Ordered by Platform Bottom Depth

Number of Species – Platform Shell Mound

Figure 12. Number of species observed on shell mounds of platforms, 2004–2009. Platforms are listed first from northern most to 

southernmost and then from shallowest to deepest.
28

Discriminant 2 (23%) 

Discriminant 1 (29%) 

Platform Shell Mounds

Canonical Discriminant Analysis 

Standardized Transformed Data 

-15 -10 -5 0 5 10 15 20 25 

-20 

-15 

-10 

-5 

0 

5 

10 

15 

20 

Edith – 49 m 

Ellen – 80 m 

Elly – 77 m 

Eureka – 212 m 

Gail – 224 m 

Gilda – 62 m 

Grace – 96 m 

Harmony – 363 m 

Harvest – 205 m 

Hermosa – 183 m 

Hildalgo – 130 m 

Holly – 64 m 

Hondo – 255 m 

Irene – 73 m 

Elly-Ellen

Middle Depths

Shallowest Depths

Deepest Depths

Figure 13. A canonical discriminant analysis of platform midwater fish assemblages, by year, 2004–2009.

All Depths Platform Shell Mounds

Standardized Transformed Densities

Shallow 

Middle 

Deep 

Average Density 

Species Cluster 

1 2 3 -0.6 

-0.4 

-0.2 

0 

0.2 

0.4 

0.6 

0.8 

Figure 14. A comparison of densities of the three shell mound species clusters shown in Figure 15.
29

Wolf-eel

Halfbanded rockfish YOY

Cabezon

Painted greenling YOY

Spotted scorpionfish

Squarespot YOY

Pile perch

Blackeye goby

Sebastomus YOY

Sebastomus spp.

Unidentified rockfishes

Unidentified rockfishes YOY

Lingcod YOY

Calico rockfish

Painted greenling

Copper rockfish

Vermilion rockfish

Lingcod

Pink seaperch

Rosy rockfish

Squarespot rockfish

Honeycomb rockfish

Bluebarred ronquil

Flag rockfish

Halfbanded rockfish

Longspine combfish

Shortspine combfish

Swordspine rockfish

Bocaccio

Greenspotted rockfish

Greenstriped rockfish

Stripetail rockfish

Dover sole

Pinkrose rockfish

Greenblotched rockfish

Unidentified poachers

Blackgill rockfish

Unidentified eelpout

Cowcod YOY

Flag rockfish YOY

Pacific sanddab

3 4 5 6 7 8 9 10 11

Height

Platform Shell Mounds All Depths

More typical of

shallow platform

shell mounds

More typical of

both shallow and

middle-depth

platform shell mounds

More typical of

deep platform

shell mounds

Figure 15. A cluster analysis of the characteristic species of platform shell mounds, 2004–2009.
30

Table 6. Numbers and densities (average number per 100 m2) of fish species observed at the bottoms of platforms, 2004–2009. Rankings of total counts and average densities may differ because densities are averages of transect densities and area surveyed varied among 

transects. Young-of-the-year (YOY) and older fish are listed separately.

Platform IRENE (Surveyed 2004–2006, 2008, 2009)

Species Number Density

Halfbanded rockfish YOY 2,031 98.0

Copper rockfish 605 29.2

Shortbelly rockfish 600 28.9

Halfbanded rockfish 588 28.4

Unidentified rockfish YOY 523 25.2

Squarespot rockfish YOY 504 24.3

Vermilion rockfish 368 17.8

Painted greenling 244 11.8

Squarespot rockfish 136 6.6

Lingcod YOY 117 5.6

Calico rockfish 116 5.6

Sebastomus sp. 115 5.6

Brown rockfish 97 4.7.8

Unidentified rockfish 38 1.8

Sebastomus YOY 34 1.6

Pile perch 26 1.3

Unidentified ronquil 21 1.0

Blue rockfish 19 0.9

Canary rockfish 17 0.8

Lingcod 11 0.5

Unidentified sanddab 11 0.5

Copper rockfish YOY 10 0.5

Widow rockfish YOY 10 0.5

Flag rockfish 8 0.4

Starry rockfish YOY 8 0.4

Olive rockfish 4 0.2

Rubberlip seaperch 4 0.2

Unidentified fishes 4 0.2

Vermilion rockfish YOY 4 0.2

Blackeye goby 3 0.1

Yelloweye rockfish YOY 3 0.1

Yellowtail rockfish 3 0.1

Kelp greenling 2 0.1

Painted greenling YOY 2 0.1

Bocaccio YOY 1 <0.1

Flag rockfish YOY 1 <0.1

Greenspotted rockfish 1 <0.1

Rosy rockfish 1 <0.1

Shortbelly rockfish YOY 1 <0.1

Starry rockfish 1 <0.1

Unidentified surfperch 1 <0.1

Swordspine rockfish 1 <0.1

Treefish 1 <0.1

Widow rockfish 1 <0.1

Wolf-eel 1 <0.1

Yelloweye rockfish 1 <0.1

Yellowtail rockfish YOY 1 <0.1

Total 6,299

Minimum number of species 30

Total rockfish YOY 3,131

Total rockfishes 5,852

Rockfish YOY comprised 49.7% of all fishes surveyed

All rockfishes comprised 92.9% of all fishes surveyed

Platform HIDALGO (Surveyed 2004–2006, 2009)

Species Number Density

Halfbanded rockfish 3,278 155.2

Greenspotted rockfish 340 16.1

Vermilion rockfish 239 11.3

Sebastomus sp. 154 7.3

Flag rockfish 95 4.5

Canary rockfish 94 4.5

Painted greenling 81 3.8

Pygmy rockfish 79 3.7

Squarespot rockfish 53 2.5

Unidentified rockfish 52 2.5

Greenstriped rockfish 45 2.1

Unidentified rockfish YOY 37 1.8

Widow rockfish YOY 28 1.3

Lingcod 26 1.2

Lingcod YOY 25 1.2

Swordspine rockfish 13 0.6

Widow rockfish 12 0.6

Cowcod 10 0.5

Rosy rockfish 10 0.5

Greenblotched rockfish 9 0.4

Cowcod YOY 7 0.3

Painted greenling YOY 7 0.3

Bocaccio 4 0.2

Greenspotted rockfish YOY 3 0.1

Sebastomus YOY 3 0.1

Starry rockfish 3 0.1

Flag rockfish YOY 2 <0.1

Greenstriped rockfish YOY 2 <0.1

Shortspine combfish 2 <0.1

Unidentified fishes 2 <0.1

Kelp greenling 1 <0.1

Shortbelly rockfish YOY 1 <0.1

Swordspine rockfish YOY 1 <0.1

Wolf-eel 1 <0.1

Yelloweye rockfish 1 <0.1

Yelloweye rockfish YOY 1 <0.1

Total 4,721

Minimum number of species 22

Total rockfish YOY 92

Total rockfishes 4,576

Rockfish YOY comprised 1.9% of all fishes surveyed

All rockfishes comprised 96.9% of all fishes surveyed
31

Platform HARVEST (Surveyed 2004)

Species Number Density

Halfbanded rockfish 216 34.1

Stripetail rockfish 96 15.2

Greenstriped rockfish 41 6.5

Sebastomus sp. 19 3.0

Greenspotted rockfish 8 1.3

Pinkrose rockfish 8 1.3

Flag rockfish 7 1.1

Sharpchin rockfish 6 1.0

Lingcod 4 0.6

Greenblotched rockfish 3 0.5

Unidentified rockfish 3 0.5

Starry rockfish 2 0.3

Shortspine combfish 1 0.2

Yelloweye rockfish 1 0.2

Total 415

Minimum number of species 12

Total rockfish YOY 0

Total rockfishes 410

Rockfish YOY comprised 0% of all fishes surveyed

All rockfishes comprised 98.8% of all fishes surveyed

Platform HERMOSA (Surveyed 2004, 2006)

Species Number Density

Halfbanded rockfish 12,123 1,035.5

Sebastomus sp. 17 1.5

Greenspotted rockfish 10 0.9

Flag rockfish 7 0.6

Stripetail rockfish 5 0.4

Unidentified rockfish 5 0.4

Sebastomus YOY 3 0.3

Rosy rockfish 2 0.2

Squarespot rockfish 2 0.2

Vermilion rockfish 2 0.2

California smoothtongue 1 <0.1

Cowcod YOY 1 <0.1

Darkblotched rockfish 1 <0.1

Greenstriped rockfish 1 <0.1

Lingcod 1 <0.1

Longspine combfish 1 <0.1

Painted greenling 1 <0.1

Sharpchin rockfish 1 <0.1

Shortbelly rockfish 1 <0.1

Starry rockfish 1 <0.1

Unidentified fishes 1 <0.1

Widow rockfish YOY 1 <0.1

Total 12,188

Minimum number of species 18

Total rockfish YOY 5

Total rockfishes 12,183

Rockfish YOY comprised <0.1% of all fishes surveyed

All rockfishes comprised >99.9% of all fishes surveyed

Platform HARMONY (Surveyed 2004)

Species Number Density

Unidentified thornyheads 48 5.5

Blackgill rockfish 24 2.9

Darkblotched rockfish 20 2.4

Splitnose rockfish 15 1.8

Unidentified rockfish 9 1.1

Aurora rockfish 4 0.5

Total 118

Minimum number of species 5

Total rockfish YOY 0

Total rockfishes 72

Rockfish YOY comprised 0% of all fishes surveyed

All rockfishes comprised 61.0% of all fishes surveyed

Platform HERITAGE (Surveyed 2008)

Species Number Density

Splitnose rockfish 18 2.2

Pinkrose rockfish 4 0.5

Bank rockfish 3 0.4

Blackgill rockfish 3 0.4

Unidentified rockfish 3 0.4

Blacktail snailfish 2 0.3

Unidentified fishes 2 0.3

Unidentified witch-eel 2 0.3

Bank rockfish YOY 1 0.1

Bearded eelpout 1 0.1

Unidentified cusk-eel 1 0.1

Flag rockfish 1 0.1

Greenblotched rockfish 1 0.1

Sebastomus sp. 1 0.1

Spotted cusk-eel 1 0.1

Unidentified sculpin 1 0.1

Total 45

Minimum number of species 12

Total rockfish YOY 1

Total rockfishes 35

Rockfish YOY comprised 2.2% of all fishes surveyed

All rockfishes comprised 77.8% of all fishes surveyed

Table 6 (continued)
32

Table 6 (continued)

Platform HONDO (Surveyed 2004, 2006, 2008)

Species Number Density

Northern anchovy 1,572 236.5

Stripetail rockfish 230 14.0

Bank rockfish 72 4.4

Pinkrose rockfish 52 3.5

Greenblotched rockfish 34 2.2

Darkblotched rockfish 28 2.1

Sebastomus sp. 25 1.7

Shortbelly rockfish 19 2.6

Splitnose rockfish 10 1.2

Unidentified rockfish 7 0.4

Sharpchin rockfish 4 0.3

Flag rockfish 3 0.2

Unidentified poachers 3 0.5

Blackgill rockfish 2 0.1

Unidentified fishes 2 0.1

Bank rockfish YOY 1 <0.1

Cowcod 1 <0.1

Dover sole 1 <0.1

Unidentified flatfish 1 <0.1

Painted greenling 1 <0.1

Unidentified eelpout 1 <0.1

Total 2,069

Minimum number of species 16

Total rockfish YOY 1

Total rockfish 488

Rockfish YOY comprised <0.01% of all fishes surveyed

All rockfishes comprised 23.6% of all fishes surveyed

Platform (Surveyed 2004–2008)

Species Number Density

Calico rockfish 1,570 94.2

Halfbanded rockfish 257 15.7

Unidentified rockfish YOY 239 14.1

Rosy rockfish 137 8.4

Vermilion rockfish 108 6.4

Copper rockfish 84 5.0

Squarespot rockfish 84 5.1

Blackeye goby 72 4.4

Painted greenling 59 3.6

Brown rockfish 42 2.5

Canary rockfish 34 2.0

Unidentified ronquil 29 1.7

Olive rockfish 22 1.3

Pink seaperch 21 1.2

Halfbanded rockfish YOY 20 1.2

Unidentified sanddabs 20 1.2

Squarespot rockfish YOY 18 1.1

Widow rockfish YOY 18 1.1

Pile perch 17 1.1

Flag rockfish 16 0.9

Honeycomb rockfish 16 0.9

Kelp greenling 13 0.8

Bluebanded ronquil 13 0.8

Bocaccio YOY 11 0.7

Sebastomus sp. 11 1.9

Unidentified rockfish 11 0.8

Vermilion rockfish YOY 10 0.6

Pacific sanddab 9 1.7

Treefish 9 0.5

Sebastomus YOY 8 0.5

Gopher rockfish 7 0.4

Lingcod 5 0.3

Sharpnose seaperch 5 0.3

Shortspine combfish 5 0.6

Starry rockfish 5 0.3

Blue rockfish 4 0.2

Kelp rockfish 4 0.2

Rubberlip seaperch 4 0.2

Starry rockfish YOY 4 0.2

Widow rockfish 4 0.2

Bull sculpin 3 0.2

Unidentified flatfish 3 0.2

Lingcod YOY 3 0.4

Painted greenling YOY 3 0.2

Yellowtail rockfish 3 0.2

Calico rockfish YOY 2 0.1

Copper rockfish YOY 2 0.1

Spotted scorpionfish 2 0.1

Yelloweye rockfish YOY 2 0.1

Brown rockfish YOY 1 0.2

California lizardfish 1 0.2

Chilipepper 1 <0.1

Honeycomb rockfish YOY 1 <0.1

Longspine combfish 1 <0.1

Rosy rockfish YOY 1 <0.1

Unidentified fish 1 <0.1

Yelloweye rockfish 1 <0.1

Total 3,056

Minimum number of species 38

Total rockfish YOY 337

Total rockfishes 2,767

Rockfish YOY comprised 11.0% of all fishes surveyed

All rockfishes comprised 90.5% of all fishes surveyed
33

Table 6 (continued)

Platform GRACE (Surveyed 2004–2005, 2007–2009)

Species Number Density

Halfbanded rockfish 13,100 579.1

Squarespot rockfish 535 23.7

Vermilion rockfish 443 19.6

Widow rockfish 433 19.1

Widow rockfish YOY 381 16.8

Unidentified rockfish YOY 168 7.4

Flag rockfish 90 4.0

Lingcod 40 1.8

Bocaccio 39 1.7

Painted greenling 28 1.2

Rosy rockfish 25 1.1

Blue rockfish 22 1.0

Calico rockfish 17 0.8

Unidentified sanddab 17 0.8

Pink seaperch 16 0.7

Sebastomus sp. 15 0.7

Greenspotted rockfish 14 0.6

Copper rockfish 13 0.6

Lingcod YOY 12 0.5

Unidentified rockfish 10 0.4

Shortspine combfish 9 0.4

Treefish 4 0.2

Bocaccio YOY 3 0.1

Canary rockfish 3 0.1

Greenstriped rockfish 3 0.1

Olive rockfish 3 0.1

Squarespot rockfish YOY 3 0.1

Unidentified fishes 3 0.1

Yellowtail rockfish 3 0.1

Kelp greenling 2 <0.1

Sebastomus sp. YOY 2 <0.1

Starry rockfish 2 <0.1

Unidentified combfish 1 <0.1

Shortbelly rockfish 1 <0.1

Swordspine rockfish 1 <0.1

Treefish YOY 1 <0.1

Total 15,462

Minimum number of species 25

Total rockfish YOY 558

Total rockfishes 15,334

Rockfish YOY comprised 3.6% of all fishes surveyed

All rockfishes comprised 99.2% of all fishes surveyed

Platform GILDA (Surveyed 2004, 2007–2009)

Species Number Density

Halfbanded rockfish 6,231 399.2

Vermilion rockfish 735 47.1

Calico rockfish 383 24.5

Painted rockfish 132 8.5

Lingcod YOY 48 3.1

Vermilion rockfish YOY 45 2.9

Copper rockfish 36 2.3

Brown rockfish 34 2.2

Unidentified flatfish 17 1.1

Pink seaperch 16 1.0

Rosy rockfish 16 1.0

Pile perch 15 <0.1

Flag rockfish 12 <0.1

Unidentified rockfish 10 <0.1

Lingcod 9 <0.1

Olive rockfish 8 <0.1

Bocaccio 7 <0.1

Canary rockfish 6 <0.1

Unidentified ronquil 6 <0.1

Cabezon 5 <0.1

Kelp rockfish 5 <0.1

Unidentified sanddab 5 <0.1

Shortspine combfish 4 <0.1

Unidentified fishes 4 <0.1

Kelp greenling 3 <0.1

Squarespot rockfish 3 <0.1

Starry rockfish 3 <0.1

Copper rockfish YOY 2 <0.1

Sebastomus sp. 2 <0.1

Treefish 2 <0.1

Blacksmith 1 <0.1

Bocaccio YOY 1 <0.1

Brown rockfish YOY 1 <0.1

California halibut 1 <0.1

Chilipepper YOY 1 <0.1

Gopher rockfish 1 <0.1

Greenspotted rockfish 1 <0.1

Spotted scorpionfish 1 <0.1

Bluebanded ronquil 1 <0.1

Unidentified surfperch 1 <0.1

Treefish YOY 1 <0.1

Unidentified sculpin 1 <0.1

Widow rockfish 1 <0.1

Yelloweye rockfish 1 <0.1

Total 7,818

Minimum number of species 31

Total rockfish YOY 51

Total rockfishes 7,596

Rockfish YOY comprised 0.4% of all fishes surveyed

All rockfishes comprised 97.2% of all fishes surveyed
34

Table 6 (continued)

Platform GAIL (Surveyed 2004–2009)

Species Number Density

Bocaccio 899 25.0

Pinkrose rockfish 402 11.2

Greenblotched rockfish 241 6.7

Lingcod 138 3.8

Cowcod 104 2.9

Sebastomus sp. 102 2.8

Mexican rockfish 93 2.6

Greenspotted rockfish 60 1.7

Greenstriped rockfish 30 0.8

Flag rockfish 12 0.3

Unidentified rockfish 7 0.2

Unidentified fishes 4 0.1

Spotted ratfish 3 <0.1

Widow rockfish 3 <0.1

Pink rockfish 2 <0.1

Unidentified ronquil 2 <0.1

Bocaccio YOY 1 <0.1

Chilipepper 1 <0.1

Unidentified flatfish 1 <0.1

Lingcod YOY 1 <0.1

Painted greenling 1 <0.1

Redbanded rockfish 1 <0.1

Rosethorn rockfish 1 <0.1

Vermilion rockfish 1 <0.1

Total 2,110

Minimum number of species 18

Total rockfish YOY 2

Total rockfishes 1,960

Rockfish YOY comprised 0.1% of all fishes surveyed

All rockfishes comprised 92.9% of all fishes surveyed

Platform EDITH (Surveyed 2005–2009)

Species Number Density

Squarespot rockfish YOY 19,448 907.4

Shortbelly rockfish YOY 8,327 384.7

Blackeye goby 854 40.5

Sebastomus YOY 567 26.5

Unidentified rockfish YOY 440 20.3

Spotted scorpionfish 320 14.9

Squarespot rockfish 206 9.5

Painted greenling 55 2.6

Pile perch 37 1.8

Cabezon 33 1.6

Sebastomus sp. 20 0.9

White seaperch 18 0.8

Lingcod 14 0.7

Painted greenling YOY 11 0.5

Rosy rockfish 11 0.5

Bocaccio YOY 5 0.2

Kelp rockfish 5 0.2

California sheephead 5 0.2

Copper rockfish 4 0.2

Sharpnose seaperch 4 0.2

Gopher rockfish 3 0.1

Honeycomb rockfish 3 0.1

Unidentified fishes 3 0.1

Brown rockfish 2 <0.1

Deepwater blenny 1 <0.1

Flag rockfish 1 <0.1

Honeycomb rockfish 1 <0.1

Rubberlip seaperch 1 <0.1

Unidentified surfperch 1 <0.1

Widow rockfish YOY 1 <0.1

Total 30,401

Minimum number of species 23

Total rockfish YOY 28,791

Total rockfishes 29,044

Rockfish YOY comprised 94.7% of all fishes surveyed

All rockfishes comprised 95.5% of all fishes surveyed

Platform ELLY (Surveyed 2005–2006, 2008–2009)

Species Number Density

Halfbanded rockfish 3,573 202.9

Unidentified rockfish YOY 3,128 177.6

Squarespot rockfish 2,314 131.4

Squarespot rockfish YOY 906 51.5

Shortbelly rockfish YOY 584 33.2

Rosy rockfish 533 30.3

Calico rockfish 487 27.7

Flag rockfish 327 18.6

Honeycomb rockfish 292 16.6

Sebastomus sp. 217 12.3

Vermilion rockfish 139 7.9

Painted greenling 85 4.8

Lingcod 83 4.7

Unidentified rockfish 80 4.5

Bocaccio 52 3.0

Treefish 46 2.6

Starry rockfish 16 0.9

Cabezon 9 0.5

Bocaccio YOY 8 0.5

Gopher rockfish 8 0.5

Olive rockfish 8 0.5

Bluebanded ronquil 8 0.5

Greenspotted rockfish 6 0.3

Pile perch 6 0.3

Unidentified fishes 6 0.3

Halfbanded rockfish YOY 5 0.3

Pink seaperch 5 0.3

Copper rockfish 4 0.2

Blue rockfish 3 0.2

Sharpnose seaperch 3 0.2

Yelloweye rockfish 3 0.2

Freckled rockfish 2 0.1

Greenblotched rockfish 2 0.1

Shortbelly rockfish 2 0.1

Speckled rockfish 2 0.1

Unidentified surfperch 2 0.1

Bank rockfish 1 <0.1

Cowcod YOY 1 <0.1

Flag rockfish YOY 1 <0.1

Kelp greenling 1 <0.1
35

Table 6 (continued)

Rosy rockfish YOY 1 <0.1

Shortspine combfish 1 <0.1

Widow rockfish 1 <0.1

Wolf-eel 1 <0.1

Yelloweye rockfish YOY 1 <0.1

Yellowtail rockfish 1 <0.1

Total 12,964

Minimum number of species 36

Total rockfish YOY 4,635

Total rockfishes 12,754

Rockfish YOY comprised 35.8% of all fishes surveyed

All rockfishes comprised 98.4% of all fishes surveyed

Platform ELLEN (Surveyed 2005–2009)

Species Number Density

Halfbanded rockfish 13,530 540.0

Squarespot rockfish 1,952 78.4

Halfbanded rockfish YOY 599 24.6

Unidentified rockfish YOY 548 22.5

Honeycomb rockfish 473 19.4

Shortbelly rockfish YOY 347 14.2

Squarespot rockfish YOY 268 11.0

Vermilion rockfish 201 8.1

Flag rockfish 177 7.1

Rosy rockfish 176 7.2

Calico rockfish 95 3.9

Painted greenling 91 3.7

Sebastomus sp. 85 3.4

Lingcod 44 1.8

Bocaccio 33 1.3

Starry rockfish 28 1.2

Treefish 24 1.0

Widow rockfish 23 0.9

Cabezon 14 0.6

Copper rockfish 14 0.6

Freckled rockfish 14 0.6

Bocaccio YOY 11 0.5

Bluebanded ronquil 11 0.5

Unidentified rockfish 11 0.4

Pink seaperch 10 0.4

Pile seaperch 7 0.3

Blue rockfish 5 0.2

Shortbelly rockfish 5 0.2

Spotted scorpionfish 4 0.2

Unidentified surfperch 4 0.2

Kelp rockfish 3 0.1

Starry rockfish YOY 3 0.1

Swordspine rockfish 3 0.1

Canary rockfish 2 <0.1

Olive rockfish 2 <0.1

Sharpnose seaperch 2 <0.1

Widow rockfish YOY 2 <0.1

Wolf-eel 2 <0.1

Blackeye goby 1 <0.1

Brown rockfish 1 <0.1

Unidentified combfish 1 <0.1

Flag rockfish YOY 1 <0.1

Greenblotched rockfish` 1 <0.1

Lingcod YOY 1 <0.1

Sebastomus YOY 1 <0.1

Threadfin bass 1 <0.1

Unidentified ronquil 1 <0.1

Total 18,832

Minimum number of species 33

Total rockfish YOY 1,780

Total rockfishes 18,638

Rockfish YOY comprised 9.5% of all fishes surveyed

All rockfishes completed 99.0% of all fishes surveyed

Platform EUREKA (Surveyed 2005, 2007, 2009)

Species Number Density

Pinkrose rockfish 214 12.7

Greenblotched rockfish 82 4.9

Sebastomus sp. 29 1.7

Vermilion rockfish 28 1.7

Bocaccio 23 1.4

Widow rockfish 15 0.9

Lingcod 10 0.6

Cowcod 8 0.5

Greenspotted rockfish 7 0.4

Flag rockfish 6 0.4

Bank rockfish 5 0.3

Unidentified rockfish 4 0.2

Speckled rockfish 2 0.1

Unidentified ronquil 2 0.1

Cabezon 1 <0.1

Dover sole 1 <0.1

Rosethorn rockfish 1 <0.1

Sebastomus YOY 1 <0.1

Squarespot rockfish 1 <0.1

Swordspine rockfish 1 <0.1

Total 441

Minimum number of species 17

Total rockfish YOY 1

Total rockfishes 427

Rockfish YOY comprised 0.2% of all fishes surveyed

All rockfishes comprised 96.8% of all fishes surveyed
36

Table 7. Numbers and densities (average number per 100 m2) of fish species observed on the shell mounds of platforms, 2004–2009. 

Rankings of total counts and average densities may differ because densities are averages of transect densities and area surveyed varied 

among transects. Young-of-the-year (YOY) and older fish are listed separately.

Platform Irene (Surveyed 2004–2006, 2008–2009)

Species Number Density

Halfbanded rockfish YOY 1,771 114.0

Halfbanded rockfish 510 30.4

Painted greenling 165 6.1

Lingcod YOY 151 7.3

Sebastomus sp. 70 3.0

Unidentified rockfish YOY 47 1.8

Copper rockfish 36 1.1

Shortbelly rockfish 32 2.1

Northern anchovy 30 1.3

Unidentified ronquil 30 0.8

Lingcod 28 1.0

Sebastomus YOY 28 0.9

Blackeye goby 27 1.0

Squarespot rockfish YOY 21 0.8

Calico rockfish 15 0.5

Canary rockfish 15 0.5

Vermilion rockfish 13 0.5

Unidentified sanddab 12 0.5

Copper rockfish YOY 9 0.3

Unidentified rockfish 9 0.4

Yellowtail rockfish 8 0.2

Flag rockfish 7 0.3

Painted greenling YOY 7 0.4

Pile perch 7 0.3

Squarespot rockfish 7 0.1

Unidentified fishes 7 0.3

Unidentified flatfish 4 0.2

Starry rockfish YOY 3 0.1

Pinkrose rockfish 2 <0.1

Brown rockfish 1 <0.1

Greenblotched rockfish 1 <0.1

Rosy rockfish 1 <0.1

Rubberlip seaperch 1 <0.1

Tiger rockfish 1 <0.1

Total 3,076

Minimum number of species 24

Total rockfish YOY 1,879

Total rockfishes 2,607

Rockfish YOY comprised 61.1% of all fishes surveyed

All rockfishes comprised 84.8% of all fishes surveyed

Platform Hidalgo (Surveyed 2004–2006, 2009)

Species Number Density

Halfbanded rockfish 76 2.5

Greenstriped rockfish 37 1.4

Painted greenling 27 1.1

Unidentified fishes 23 0.9

Lingcod YOY 19 0.8

Lingcod 14 0.6

Unidentified combfish 12 0.5

Cowcod YOY 8 0.2

Sebastomus sp. 7

0.3

Rockfish YOY 7 0.3

Pacific sanddab 6 0.2

Greenspotted rockfish 5 0.2

Shortspine combfish 5 0.2

Rosy rockfish 4 0.2

Unidentified rockfish 4 0.2

Dover sole 3 0.1

Swordspine rockfish 3 0.1

Greenblotched rockfish 2 <0.1

Greenspotted rockfish YOY 2 <0.1

Halfbanded rockfish YOY 2 <0.1

Sebastomus YOY 2 <0.1

Squarespot rockfish 2 <0.1

Flag rockfish 1 <0.1

Flag rockfish YOY 1 <0.1

Unidentified flatfish 1 <0.1

Greenstriped rockfish YOY 1 <0.1

Swordspine rockfish YOY 1 <0.1

Unidentified sanddab 1 <0.1

Total 276

Minimum number of species 18

Total rockfish YOY 24

Total rockfishes 165

Rockfish YOY comprised 8.7% of all fishes surveyed

All rockfishes comprised 59.8% of all fishes surveyed 

Platform Harvest (Surveyed 2004)

Species Number Density

Halfbanded rockfish 595 26.8

Stripetail rockfish 441 19.9

Greenstriped rockfish 16 0.7

Sebastomus sp. 9 0.4

Unidentified ronquil 4 0.2

Shortspine combfish 3 0.1

Unidentified rockfish 3 0.1

Lingcod 2 <0.1

Unidentified fishes 2 <0.1

Flag rockfish 1 <0.1

Greenblotched rockfish 1 <0.1

Lingcod YOY 1 <0.1

Unidentified poacher 1 <0.1

Total 1,079

Minimum number of species 9

Total rockfish YOY 0

Total rockfishes 1,066

Rockfish YOY comprised 0% of all fishes surveyed

All rockfishes comprised 98.8% of all fishes surveyed.
37

Platform Hermosa (Surveyed 2004, 2006)

Species Number Density

Halfbanded rockfish 8,696 370.7

Stripetail rockfish 6 0.2

Sebastomus sp. 5 0.4

Unidentified fishes 3 0.2

Bocaccio YOY 2 <0.1

Cowcod YOY 2 0.1

Flag rockfish 2 0.2

Greenstriped rockfish 2 0.2

Sebastomus YOY 2 <0.1

Unidentified combfish 1 <0.1

Flag rockfish YOY 1 <0.1

Greenspotted rockfish 1 <0.1

Painted greenling 1 <0.1

Shortspine combfish 1 <0.1

Unidentifiable rockfish 1 <0.1

Total 8,726

Minimum number of species 9

Total rockfish YOY 7

Total rockfishes 8,720

Rockfish YOY comprised 0.1% of all fishes surveyed

All rockfishes comprised 99.9% of all fishes surveyed

Platform Harmony (Surveyed 2004)

Species Number Density

Unidentified eelpout 43 1.9

Splitnose rockfish 20 0.9

Unidentified thornyheads 9 0.4

Blackgill rockfish 4 0.2

Aurora rockfish 3 0.1

Unidentified fishes 2 <0.1

Unidentified catshark 1 <0.1

Dover sole 1 <0.1

Sharpchin rockfish 1 <0.1

Stripetail rockfish 1 <0.1

Unidentified rockfish 1 <0.1

Total 86

Minimum number of species 9

Total rockfish YOY 0

Total rockfishes 30

Rockfish YOY comprised 0% of all fishes surveyed

All rockfishes comprised 34.9% of all fishes surveyed

Platform Hondo

Species Number Density

Stripetail rockfish 319 15.2

Darkblotched rockfish 24 1.2

Unidentified poachers 23 1.1

Greenblotched rockfish 13 0.8

Bank rockfish 10 0.8

Sebastomus sp. 8 0.5

Pinkrose rockfish 7 0.5

Splitnose rockfish 7 0.4

Blackgill rockfish 6 0.3

Shortbelly rockfish 6 0.3

Unidentified rockfish 6 0.4

Unidentified eelpout 5 0.2

Unidentified flatfish 4 0.3

Sharpchin rockfish 4 0.2

Bearded eelpout 2 <0.1

Blackgill rockfish YOY 2 <0.1

Bluebarred prickleback 2 <0.1

Dover sole 2 <0.1

Unidentified sanddab 2 <0.1

Blackbelly eelpout 1 <0.1

Blacktail snailfish 1 <0.1

Cowcod 1 <0.1

Flag rockfish 1 <0.1

Sebastomus YOY 1 <0.1

Unidentified fishes 1 <0.1

Unidentified rockfish YOY 1 <0.1

Unidentified ronquil 1 <0.1

Total 460

Minimum number of species 19

Total rockfish YOY 4

Total rockfishes 416

Rockfish YOY comprised 0.8% of all fishes surveyed

All rockfishes comprised 80.6% of all fishes surveyed

Table 7 (continued)
38

Platform Holly (Surveyed 2005–2006, 2008)

Species Number Density

Calico rockfish 383 24.1

Halfbanded rockfish 69 9.6

Blackeye goby 33 1.6

Rosy rockfish 27 1.4

Vermilion rockfish 23 1.3

Copper rockfish 19 1.1

Squarespot rockfish 19 0.8

Painted greenling 16 0.9

Unidentified ronquil 14 1.4

Unidentified sanddab 14 0.8

Brown rockfish 12 0.7

Pink seaperch 10 0.6

Pacific sanddab 7 0.5

Pile perch 7 0.3

Bluebanded ronquil 7 0.3

Honeycomb rockfish 6 0.2

Longspine combfish 6 0.4

Sebastomus sp. 5 1.8

Flag rockfish 4 0.7

Kelp greenling 4 0.2

Lingcod YOY 4 2.3

Shortspine combfish 4 0.2

Lingcod 3 0.1

Bull sculpin 2 0.1

Canary rockfish 2 0.1

Squarespot rockfish YOY 2 1.2

Unidentified surfperch 2 0.1

Unidentified rockfish 2 0.1

Brown rockfish YOY 1 <0.1

Calico rockfish YOY 1 <0.1

California lizardfish 1 <0.1

Chilipepper 1 <0.1

Flag rockfish YOY 1 <0.1

Unidentified flatfish 1 <0.1

Unidentified Icelinus 1 <0.1

Rosy rockfish YOY 1 <0.1

Spotted scorpionfish 1 <0.1

Starry flounder 1 <0.1

Treefish 1 <0.1

Unidentified fishes 1 <0.1

Wolf-eel 1 <0.1

Yellowtail rockfish 1 <0.1

Total 720

Minimum number of species 30

Total rockfish YOY 6

Total rockfishes 580

Rockfish YOY comprised 0.8% of all fishes surveyed

All rockfishes comprised 80.6% of all fishes surveyed

Platform Grace (Surveyed 2004–2005, 2007–2009)

Species Number Density

Halfbanded rockfish 657 23.3

Squarespot rockfish 114 4.4

Unidentified rockfish YOY 111 2.4

Unidentified sanddabs 51 1.8

Shortspine combfish 39 1.4

Pink seaperch 33 1.2

Lingcod 26 0.8

Greenstriped rockfish 24 0.8

Flag rockfish 23 0.7

Lingcod YOY 23 0.8

Longspine combfish 22 0.7

Vermilion rockfish 15 0.4

Greenspotted rockfish 13 0.4

Painted greenling 12 0.4

Rosy rockfish 8 0.3

Sebastomus sp. 8 0.3

Unidentified fishes 8 0.3

Blue rockfish 5 0.1

Bocaccio 5 0.2

Unidentified rockfish 5 0.2

Unidentified combfish 4 0.1

Sebastomus YOY 4 0.1

Unidentified flatfish 3 0.1

Greenspotted rockfish YOY 2 <0.1

Bocaccio YOY 1 <0.1

Cabezon 1 <0.1

Copper rockfish 1 <0.1

Flag rockfish YOY 1 <0.1

Greenblotched rockfish 1 <0.1

Shortbelly rockfish 1 <0.1

Spotted ratfish 1 <0.1

Bluebanded ronquil 1 <0.1

Swordspine rockfish 1 <0.1

Widow rockfish YOY 1 <0.1

Total 1,225

Minimum number of species 25

Total rockfish YOY 120

Total rockfishes 1,001

Rockfish YOY comprised 9.8% of all fishes surveyed

All rockfishes comprised 81.7% of all fishes surveyed

Table 7 (continued)
39

Platform Gilda (Surveyed 2004, 2007–2009)

Species Number Density

Halfbanded rockfish 10,069 469.0

Calico rockfish 85 4.3

Lingcod YOY 70 4.0

Painted greenling 57 3.5

Widow rockfish 46 2.1

Vermilion rockfish 38 2.0

Lingcod 16 0.9

Pacific sanddab 15 0.8

Pink seaperch 13 0.7

Unidentified sanddab 13 0.8

Flag rockfish 11 0.6

Rosy rockfish 11 0.6

Copper rockfish 10 0.5

Pile perch 10 0.6

Vermilion rockfish YOY 8 0.5

Shortspine combfish 7 0.4

Unidentified flatfish 6 0.3

Spotted scorpionfish 6 0.4

Olive rockfish 3 0.1

Blackeye goby 2 0.1

Unidentified combfish 2 0.1

Longspine combfish 2 0.1

Squarespot rockfish 2 0.1

Unidentified fishes 2 0.1

Unidentified rockfish 2 <0.1

Wolf-eel 2 0.1

Cabezon 1 <0.1

California halibut 1 <0.1

Rubberlip seaperch 1 <0.1

Unidentified surfperch 1 <0.1

Unidentified ronquil 1 <0.1

Total 10,513

Minimum number of species 24

Total rockfish YOY 8

Total rockfishes 10,298

Rockfish YOY comprised 0.1% of all fishes surveyed

All rockfishes comprised 98.0% of all fishes surveyed

Platform Gail (Surveyed 2004–2009)

Species Number Density

Greenstriped rockfish 169 9.8

Pinkrose rockfish 149 4.6

Stripetail rockfish 76 1.3

Greenblotched rockfish 41 1.4

Lingcod 26 0.6

Shortspine combfish 24 0.3

Bocaccio 21 0.5

Unidentified poacher 19 0.5

Unidentified flatfish 14 0.3

Dover sole 10 0.2

Flag rockfish 10 0.3

Greenspotted rockfish 8 0.3

Sebastomus sp. 8 0.3

Unidentified combfish 7 0.1

Blackgill rockfish 6 0.4

Unidentified fishes 6 0.3

Unidentified rockfish 6 0.1

Darkblotched rockfish 4 <0.1

Unidentified sculpin 4 <0.1

Cowcod YOY 3 <0.1

Pacific sanddab 3 <0.1

Sharpchin rockfish 2 <0.1

Swordspine rockfish 2 <0.1

Bluebarred prickleback 1 <0.1

Cowcod 1 <0.1

Darkblotched rockfish YOY 1 <0.1

English sole 1 <0.1

Halfbanded rockfish 1 <0.1

Mexican rockfish 1 <0.1

Redbanded rockfish 1 <0.1

Squarespot rockfish 1 <0.1

Starry rockfish 1 <0.1

Unidentified eelpout 1 <0.1

Unidentified rockfish YOY 1 <0.1

Unidentified ronquil 1 <0.1

Total 630

Minimum number of species 29

Total rockfish YOY 5

Total rockfishes 513

Rockfish YOY comprised 0.8% of all fishes surveyed

All rockfishes comprised 81.4% of all fishes surveyed

Table 7 (continued)
40

Platform Edith (Surveyed 2005o2009)

Species Number Density

Squarespot rockfish YOY 3,721 166.0

Blackeye goby 1,939 83.9

Spotted scorpionfish 901 37.1

Sebastomus YOY 608 24.8

Shortbelly rockfish 88 4.2

Halfbanded rockfish YOY 70 3.1

Wolf-eel 60 2.7

Unidentified rockfish YOY 38 1.5

Pile perch 32 1.4

Painted greenling 22 0.9

Squarespot rockfish 15 0.6

Unidentified fishes 13 0.6

Cabezon 11 0.5

Painted greenling YOY 11 0.5

Sharpnose seaperch 4 0.2

Unidentified surfperch 4 0.2

White seaperch 4 0.2

Honeycomb rockfish 3 0.1

Lingcod 3 0.1

Vermilion rockfish 3 0.1

Blue rockfish 2 <0.1

Deepwater blenny 2 <0.1

Sebastomus sp. 2 <0.1

Bluebanded ronquil 2 <0.1

Unidentified sanddab 2 <0.1

Blacksmith YOY 1 <0.1

Bocaccio YOY 1 <0.1

Brown rockfish YOY 1 <0.1

Calico rockfish 1 <0.1

Calico rockfish YOY 1 <0.1

Honeycomb rockfish YOY 1 <0.1

Olive rockfish 1 <0.1

Senorita 1 <0.1

Unidentified rockfish 1 <0.1

Unidentified ronquil 1 <0.1

Total 7,570

Minimum number of species 25

Total rockfish YOY 4,529

Total rockfishes 4,557

Rockfish YOY comprised 59.8% of all fishes surveyed

All rockfishes comprised 60.2% of all fishes surveyed

Platform Elly (Surveyed 2005–2006, 2008–2009)

Species Number Density

Halfbanded rockfish 3,580 143.0

Rockfish YOY 696 32.2

Halfbanded rockfish YOY 163 7.6

Shortbelly rockfish YOY 108 5.0

Squarespot rockfish 104 4.9

Rosy rockfish 96 4.1

Pink seaperch 72 3.0

Squarespot rockfish YOY 64 3.1

Widow rockfish YOY 60 2.8

Lingcod 53 2.2

Calico rockfish 49 2.0

Painted rockfish 47 2.1

Sebastomus sp. 39 1.8

Honeycomb rockfish 37 1.6

Unidentified rockfish 34 1.6

Shortbelly rockfish 32 1.6

Unidentified sanddab 21 0.9

Blackeye goby 11 0.4

Flag rockfish 9 0.3

Shortspine combfish 7 0.3

Unidentified ronquil 7 0.3

Unidentified fishes 5 0.2

Cabezon 3 0.2

Pile perch 3 0.1

Bluebanded ronquil 3 0.2

Wolf-eel 3 0.1

Sharpnose seaperch 2 <0.1

Starry rockfish 2 <0.1

Bocaccio 1 <0.1

Unidentified combfish 1 <0.1

Cowcod 1 <0.1

Cowcod YOY 1 <0.1

Unidentified flatfish 1 <0.1

Greenspotted rockfish 1 <0.1

Lingcod YOY 1 <0.1

Pygmy rockfish 1 <0.1

Sebastomus YOY 1 <0.1

Stripetail rockfish 1 <0.1

Total 5,320

Minimum number of species 25

Total rockfish YOY 1,093

Total rockfishes 5,080

Rockfish YOY comprised 21.5% of all fishes surveyed

All rockfishes comprised 95.5% of all fishes surveyed

Table 7 (continued)
41

Platform Ellen (Surveyed 2005–2009)

Species Number Density

Halfbanded rockfish 3,401 92.5

Honeycomb rockfish 225 7.5

Squarespot rockfish 172 4.6

Unidentified sanddab 144 4.0

Rosy rockfish 105 3.5

Squarespot rockfish YOY 69 2.2

Painted greenling 50 1.6

Flag rockfish 42 1.2

Calico rockfish 38 1.2

Pink seaperch 38 1.1

Sebastomus sp. 38 1.2

Lingcod 36 1.1

Bluebanded ronquil 28 0.9

Blackeye goby 24 0.7

Halfbanded rockfish YOY 24 0.8

Unidentified surfperch 20 0.5

Unidentified rockfish YOY 16 0.5

Shortspine combfish 13 0.4

Unidentified fishes 12 0.4

Cabezon 9 0.3

Sebastomus YOY 7 0.2

Unidentified flatfish 6 0.2

Lingcod YOY 6 0.2

Spotted scorpionfish 6 0.2

Unidentified ronquil 6 0.1

Swordspine rockfish 4 0.1

Unidentified combfish 3 <0.1

Unidentified rockfish 3 0.1

Vermilion rockfish 3 0.1

White seaperch 3 0.1

Cowcod YOY 2 <0.1

Flag rockfish YOY 2 <0.1

Freckled rockfish 2 <0.1

Greenspotted rockfish 2 <0.1

Pacific electric ray 2 <0.1

Pile perch 2 <0.1

Wolf-eel 2 <0.1

California lizardfish 1 <0.1

Copper rockfish 1 <0.1

Starry rockfish 1 <0.1

Total 4,568

Minimum number of species 27

Total rockfish YOY 120

Total rockfishes 4,157

Rockfish YOY comprised 2.6% of all fishes surveyed

All rockfishes comprised 91.0% of all fishes surveyed

Platform Eureka (Surveyed 2005, 2007, 2009)

Species Number Density

Pinkrose rockfish 87 3.8

Shortspine combfish 17 0.8

Greenstriped rockfish 15 0.7

Sebastomus sp. 13 0.6

Dover sole 11 0.5

Greenblotched rockfish 8 0.4

Unidentified prickleback 8 0.3

Unidentified combfishes 7 0.3

Rosethorn rockfish 4 0.2

Unidentified poacher 3 0.1

Swordspine rockfish 3 0.1

Unidentified fishes 3 0.1

Unidentified eelpout 3 0.1

Pinkrose rockfish YOY 2 <0.1

Blackgill rockfish 1 <0.1

Cabezon 1 <0.1

Darkblotched rockfish 1 <0.1

Unidentified flatfish 1 <0.1

Greenspotted rockfish 1 <0.1

Stripetail rockfish 1 <0.1

Unidentified rockfish 1 <0.1

Total 191

Minimum number of species 16

Total rockfish YOY 1

Total rockfishes 137

Rockfish YOY comprised 0.5% of all fishes surveyed

All rockfishes comprised 71.7% of all fishes surveyed

Table 7 (continued)
42

A comparison of Platform and Natural Site Fish Assemblages

Because the composition of platform bottom and shell mound fish assemblages are driven by bottom 

depth (Figures 9, 13), we compared platform habitats and natural sites within the three depth regimes (≤83 

m, 84–136 m, ≥137 m) that characterize the natural habitat assemblages along much of the continental shelf 

of the southern California Bight (Love et al. 2009). 

Platform Midwaters and Natural Sites

The midwater fish assemblages of the shallow water platforms tended to be somewhat different from 

that occurring in reef habitat of shallow water natural sites (Figures 16–18). More typical midwater platform 

species included the YOY of painted greenling, Sebastomus sp., and blacksmith, along with juveniles and 

adults of such species as blacksmith, pile perch, senorita, sheephead, and sharpnose seaperch. Natural site 

fishes were characterized by species more typical of complex, high relief (gopher, starry, vermilion rockfishes, treefish) and soft-seafloor, low-relief dwellers (e.g., shortspine combfish and pink seaperch). Similar 

to shallower waters, midwater platform assemblages of middle-depth platforms were also different from 

middle-depth natural sites (Figures 19–21). Around middle depth platforms, the YOY of a number of species (e.g., bocaccio, starry and squarespot rockfishes, and painted greenling) were important, as were painted 

greenling and copper and widow rockfishes. None of these species were very abundant over middle depth 

natural sites. Instead, there were a wide variety of high-relief species (e.g., bocaccio, cowcod, greenspotted, 

pygmy, and squarespot rockfish), as well as lingcod. In addition, such soft bottom taxa as flatfishes and 

poachers were commonly observed. The midwater structure of deeper platforms was also quite different 

from deep natural sites (Figures 22–24). Midwater assemblages were similar to those around both shallow 

and middle depth platforms, while the natural site assemblage were characterized by deeper-welling rockfishes, spotted ratfish, Dover sole, flatfishes, and poachers.

Natural Sites 

A

B 

C 

Edith 

Ellen 

Elly 

Gilda 

Henry 

Hillhouse 

Holly 

Irene 

Shallow Depth Platform Midwaters and Natural Sites

Canonical Discriminant Analysis

Centroids Standardized Transformed Densities

Discriinant 2 (18%) 

Discriminant 1 (28%) 

-3 -2 -1 0 1 2 3 

-5 

-4 

-3 

-2 

-1 

0 

1 

2 

3 

4 

Figure 16. A canonical discriminant analysis comparing the midwater fish assemblages of shallow depth platforms (≤83 m) with 

shallow natural sites. Data is based on centroids of surveys conducted in 2004–2009.
43

Shallow Depth Platform Midwaters and Natural Sites 

Standardized Transformed Densities 

Natural Sites

Platforms 

1 2 

Average Density 

Species Cluster 

-0.4 

-0.3 

-0.2 

-0.1 

0 

0.1 

0.2 

0.3 

Figure 17. A comparison of densities of the two shallow midwaters and natural sites species clusters shown in Figure 18.

Unidentified sanddab

Unidentified rockfishes

Unidentified rockfishes YOY

Deepwater kelpfish

Halfbanded rockfish YOY

Flag rockfish

Unidentified flatfishes

Halfbanded rockfish

Pink seaperch

Shortspine combfish

Squarespot YOY

Starry YOY

Treefish

Sebastomus

Squarespot rockfish

Rosy rockfish

Starry rockfish

Blue rockfish

Blackeye goby

Vermilion rockfish

Surfperch spp.

White seaperch

Bocaccio

Copper rockfish

Gopher rockfish

Lingcod

Sharpnose seaperch

Blacksmith

Blacksmith YOY

Senorita

Sheephead

Sebastomus YOY

Kelp rockfish

Painted greenling

Painted greenling YOY

Olive rockfish

Pile perch

18 20 22 24 26

Height

More typical of

shallow depth

natural sites

More typical of

midwaters of

shallow depth

platforms

Platform Midwaters and Natural Sites

Shallow Depth Category

Figure 18. A cluster analysis of the characteristic species of platform midwaters of shallow depth platforms (≤83 m) and shallow 

natural sites. Data is based on surveys conducted in 2004–2009.
44

Natural Sites 

Grace 

Habitat 

Hidalgo 

Middle Depth Platform Midwaters and Natural Sites

Canonical Discriminant Analysis

Centroids Standardized Transformed Densities 

Discriminant 2 (20%) 

Discriminant 1 (28%) 

-4 -3 -2 -1 0 1 2 3 4 5 

-6 

-5 

-4 

-3 

-2 

-1 

0 

1 

2 

3 

Figure 19. A canonical discriminant analysis comparing the midwater fish assemblages of middle depth platforms (84–136 m) 

with middle depth natural sites. Data is based on centroids of surveys conducted in 2004–2009.

Middle Depth Platform Midwaters and Natural Sites 

Standardized Transformed Densities 

Natural Sites

Platforms 

1 2 

Average Density 

Species Cluster 

-0.6 

-0.4 

-0.2 

0 

0.2 

0.4 

0.6 

Figure 20. A comparison of densities of the two middle depth midwater and natural sites species clusters shown in Figure 21.
45

Painted greenling

Painted greenling YOY

Bocaccio YOY

Copper rockfish

Widow rockfish

Squarespot rockfish YOY

Unidentified rockfishes YOY

Starry YOY

Unidentified rockfishes

Unidentified sanddab

Shortbelly rockfish

Pygmy rockfish YOY

Rosy rockfish

Bocaccio

Cowcod

Spotted ratfish

Swordspine rockfish

Squarespot rockfish

Speckled rockfish

Starry rockfish

Pygmy rockfish

Sebastomus

Sebastomus YOY

Shortspine combfish

Longspine combfish

Pink seaperch

Greenblotched rockfish

Greenstriped rockfish

Vermilion rockfish

Yellowtail rockfish

Blackeye goby

Unidentified combfishes

Flag rockfish

Halfbanded rockfish YOY

Lingcod

Greenspotted rockfish

Halfbanded rockfish

Unidentified flatfishes

Unidentified poachers

12 14 16 18

Height

More typical of

midwaters of

middle depth

platforms

More typical of

middle depth

natual sites

Platform Midwaters and Natural Sites

Middle Depth Category

Figure 21. A cluster analysis of the characteristic species of platform midwaters of middle depth platforms (84–136 m) and middle 

depth natural sites. Data is based on surveys conducted in 2004–2009.
46

Discriminant 2 (16%) 

Discriminant 1 (46%) 

Natural Sites 

Eureka 

Gail 

Harmony 

Harvest 

Heritage 

Hermosa 

Hondo 

Deep Depth Platform Midwaters and Natural Sites

Canonical Discriminant Analysis

Centroids Standardized Transformed Densities

-6 -5 -4 -3 -2 -1 0 1 2 3 4 

-4 

-3 

-2 

-1 

0 

1 

2 

3 

4 

Figure 22. A canonical discriminant analysis comparing the midwater fish assemblages of deep depth platforms (≥137 m) with deep 

depth natural sites. Data is based on centroids of surveys conducted in 2004–2009.

Deep Depth Platform Midwaters and Natural Sites 

Standardized Transformed Densities 

Natural Sites

Platforms 

1 2 

Average Density 

Species Cluster 

-0.5 

-0.4 

-0.3 

-0.2 

-0.1 

0 

0.1 

0.2 

0.3 

0.4 

Figure 23. A comparison of densities of the two deep depth midwater and natural sites species clusters shown in Figure 24.
47

Unidentified rockfishes

Squarespot rockfish

Unidentified rockfishes YOY

Speckled rockfish

Speckled rockfish YOY

Flag rockfish

Bocaccio YOY

Squarespot rockfish YOY

Widow rockfish YOY

Painted greenling

Painted greenling YOY

Cabezon

Widow rockfish

Shortbelly rockfish

Greenblotched rockfish

Pinkrose rockfish

Dover sole

Bluebarred prickleback

Stripetail rockfish

 Unidentified flatfishes

Unidentified poachers

Greenspotted rockfish

Halfbanded rockfish

Unidentified combfishes

Greenstriped rockfish

Shortspine combfish

Bocaccio

Bank rockfish

Bank rockfish YOY

Cowcod

Starry rockfish

Lingcod

Spotted ratfish

Swordspine rockfish

Pygmy rockfish

Sebastomus

Sebastomus YOY

14 16 18 20 22 24

Height

More typical of

midwaters of

deep depth

platforms

More typical of

deep depth

natual sites

Platform Midwaters and Natural Sites

Deep Depth Category

Figure 24. A cluster analysis of the characteristic species of platform midwaters of deep depth platforms (≥137 m) and deep depth 

natural sites. Data is based on surveys conducted in 2004–2009.
48

Platform Bottoms and Natural Sites

Most of the shallow-water platforms supported fish assemblages that were at least somewhat different 

from natural sites (Figures 25–27). Of the six shallow water platforms, only Edith harbored a fish assemblage 

that was very similar to natural sites. Elly and Ellen shared similar assemblages, as did Gilda and Irene, while 

platform Holly stood alone. While a very wide range of species characterized platform bottoms, few were as 

important to natural sites (Figures 26–27). In general, the differences we observed reflected higher species 

densities around platforms rather than absences of these from natural sites (Table 4). In the middle depth 

range, the bottom fish assemblages of both Grace and Hidalgo were quite different from each other and 

from the natural sites (Figures 28–30). In these habitats, there were two suites of species; one composed of 

taxa most characteristic of both bottoms and natural sites and the other of platform bottoms alone (Figures 

29–30). By comparison to shallower platforms, and with the exception of Gail, the deeper bottom platform 

assemblages tended to be more similar to natural sites (Figures 31–33). The primary difference in species 

assemblages between Gail and both the other platforms and the natural sites was the much higher densities 

of a range of shelter-oriented, often economically important species, such as cowcod, bocaccio, and greenblotched, pinkrose, and greenspotted rockfishes (Table 6).

Figure 25. A canonical discriminant analysis comparing the bottom fish assemblages of shallow depth platforms (≤83 m) with shallow natural sites. Data is based on centroids of surveys conducted in 2004–2009.

Natural Sites 

Edith 

Ellen 

Elly 

Gilda 

Holly 

Irene 

Shallow Depth Platform Bottoms and Natural Sites 

Canonical Discriminant Analysis

Centroids Standardized Transformed Densities

Discriminant 2 (16%) 

Discriminant 1 (29%) 

-5 0 5 10 15 20 

-15 

-10 

-5 

0 

5 

10 

15 
49

Figure 26. A comparison of densities of the two shallow depth platform bottom and natural sites species clusters shown in Figure 

27.

Shallow Depth Platform Bottoms and Natural Sites

Standardized Transformed Densities 

-0.3 

-0.2 

-0.1 

0 

0.1 

0.2 

0.3 

0.4 

0.5 

0.6 

Natural Sites 

Platform Bottoms 

1 2

Average Density 

Species Cluster 

Figure 27. A cluster analysis of the characteristic species of platform bottoms of shallow depth platforms (≤83 m) and shallow 

natural sites. Data is based on surveys conducted in 2004–2009. Economically important species are in bold.

Greenspotted rockfish

Pink seaperch

Shortspine combfish

Unidentified sculpin

Unidentified flatfishes

Longspine combfish

Unidentified sanddab

Swordspine rockfish

Deepwater kelpfish

Bluebarred ronquil

Sharpnose surfperch

Sheephead

Blacksmith

Senorita

Halfbanded rockfish YOY

Blue rockfish

Surfperch spp.

Gopher rockfish

Olive rockfish

Blackeye goby

Squarespot rockfish YOY

White surfperch

Sebastomus YOY

Painted greenling YOY

Cabezon

Spotted scorpionfish

Kelp rockfish

Lingcod YOY

Vermilion rockfish YOY

Painted greenling

Pile perch

Copper rockfish

Vermilion rockfish

Kelp greenling

Canary rockfish

Brown rockfish

Calico rockfish

Bocaccio

Squarespot rockfish

 Starry rockfish

Starry rockfish YOY

Lingcod

Rosy rockfish

Treefish

Unidentified rockfishes YOY

Sebastomus

Unidentified rockfishes

Bocaccio YOY

Halfbanded rockfish

Flag rockfish

Honeycomb rockfish

More typical

of shallow

natural sites

More typical

of shallow

platform bottoms

10 12 14 16 18 20

Height

Platform Bottoms and Natural Sites

Shallow Depth Category
50

Natural Sites 

Grace Bottom 

Hildalgo Bottom 

Discriminant 2 (17%) 

Discriminant 1 (54%) 

Middle Depth Platform Bottoms and Natural Sites

Canonical Discriminant Analysis

Centroids Standardized Transformed Densities 

-10 -5 0 5 10 15 20 25 30 35 40 

-10 

-8 

-6 

-4 

-2 

0 

2 

4 

6 

8 

10 

12 

Figure 28. A canonical discriminant analysis comparing the bottom fish assemblages of middle depth platforms (84–136 m) withmiddle depth natural sites. Data is based on centroids of surveys conducted in 2004–2009. 

Figure 29. A comparison of densities of the two middle depth platform bottom and natural sites species clusters shown in Figure 30.

Average Density 

Middle Depth Platform Bottoms and Natural Sites

Standardized Transformed Densities 

Species Cluster 

1 2 

-0.5 

0 

0.5 

1 

1.5 

Natural Sites

Platform Bottoms 
51

Sebastomus

Sebastomus YOY

Cowcod

Spotted ratfish

Swordspine rockfish

Speckled rockfish

Starry rockfish

Pygmy rockfish

Squarespot rockfish

Bocaccio

Unidentified rockfishes

Starry rockfish YOY

Squarespot rockfish YOY

Pygmy rockfish YOY

Unidentified rockfishes YOY

Bocaccio YOY

Rosy rockfish

Longspine combfish

Copper rockfish

Blackeye goby

Pink seaperch

Shortspine combfish

Flatfishes

Unidentified sanddab

Lingcod

Kelp greenling

Lingcod YOY

Treefish

Blue rockfish

Calico rockfish

Widow rockfish

Widow rockfish YOY

Flag rockfish

Halfbanded rockfish

Vermilion rockfish

Painted greenling

Canary rockfish

Painted greenling YOY

Cowcod YOY

Greenspotted rockfish YOY

Greenstriped rockfish YOY

Greenblotched rockfish

Greenspotted rockfish

Greenstriped rockfish

2 4 6 8 10 12 14 16

Height

Platform Bottoms and Natural Sites

Middle Depth Category

More typical

of both middle depth

platform bottoms

and natural sites

More typical

of middle depth

platform bottoms

Figure 30. A cluster analysis of the characteristic species of platform bottoms of middle depth platforms (84–136 m) and middle 

depth natural sites. Data is based on surveys conducted in 2004–2009. Economically important species are in bold.
52

Figure 31. A canonical discriminant analysis comparing the bottom fish assemblages of deep depth platforms (≥137 m) with deep 

depth natural sites. Data is based on centroids of surveys conducted in 2004–2009.

Deep Depth Platform Bottoms and Natural Sites

Canonical Discriminant Analysis 

Centroids Standardized Transformed Densities 

-5 0 5 10 15 20 25

Discriminant 1 (35%) 

-6 

-4 

-2 

0 

2 

4 

6 

8 

Discriminant 2 (13%) 

Natural Sites 

Eureka 

Gail

Harmony 

Harvest 

Heritage 

Hermosa 

Hondo 

Figure 32. A comparison of densities of the two deep depth platform bottom and natural sites species clusters shown in Figure 33.

Average Density 

Deep Depth Platform Bottoms and Natural Sites

Standardized Transformed Densities 

Species Cluster 

1 2 

-0.6 

-0.4 

-0.2 

0 

0.2 

0.4 

0.6 

0.8 

Natural Sites

Other Platform Bottoms 

Gail Bottom 
53

Figure 33. A cluster analysis of the characteristic species of platform bottoms of deep depth platforms (≥137 m) and deep depthnatural sites. Data is based on surveys conducted in 2004–2009. Economically important species are in bold.

Pink rockfish

Greenblotched rockfish

Pinkrose rockfish

Widow rockfish

Unidentified ronquil

Vermilion rockfish

Lingcod

Mexican rockfish

Bocaccio

Cowcod

Flag rockfish

Greenspotted rockfish

Bank rockfish

Bank rockfish YOY

Unidentified rockfishes

Spotted ratfish

Speckled rockfish

Pygmy rockfish YOY

Starry rockfish

Pygmy rockfish

Squarespot rockfish

Swordspine rockfish

Sebastomus

Sebastomus YOY

Unknown rockfishes YOY

Longspine combfish

Rosethorn rockfish

Sharpchin rockfish

Darkblotched rockfish

Halfbanded rockfish

Painted greenling

Stripetail rockfish

Greenstriped rockfish

Pacific argentine

Shortspine combfish

Unidentified eelpout

Dover sole

Unidentified flatfishes

Unidentified poachers

Bluebarred prickleback

Unidentified prickleback

Shortbelly rockfish

Blackgill rockfish

Pacific hake

Splitnose rockfish

Unidentified thornyheads

4 6 8 10 12 14 16 18

Height

Platform Bottoms and Natural Sites

Deep Depth Category

More typical of

Platform Gail

More typical

of most deep depth

platforms and natural sites
54

Platform Shell Mounds and Natural Sites

The shell mound assemblages of most shallow platforms were quite similar to one another (Figure 34). 

The exception was Platform Edith (Figure 34) whose assemblage more closely resembled some natural sites. 

Those species more typical of shell mounds tended to be taxa (e.g., calico rockfish, ronquils, flatfishes, pink 

seaperch) that associate with lower-relief habitats, while those more abundant on natural sites (e.g., treefish, 

rosy, squarespot, starry rockfishes, blacksmith, senorita, and sheephead) characteristically live over higher 

relief (Figures 35–36). In middle depth shell mounds, the assemblages around Grace and Hidalgo were very 

similar and these were quite different from natural sites (Figures 37–39). These differences were driven by at 

least two factors. First, there were substantial differences in what species recruited to each habitat from the 

plankton as YOYs (Figure 39). For instance, starry, squarespot, and pygmy rockfish YOY were characteristic 

of natural sites, while the YOYs of lingcod, flag and greenspotted rockfish, and cowcod were found more 

often on shell mounds. Similar to the shallow water assemblage, we found that much of the middle depth 

assemblage was composed of species favoring low relief (e.g., greenstriped rockfish, combfishes, and Pacific 

sanddab), while higher-relief taxa (e.g., cowcod, speckled, pygmy, and rosy rockfishes) characterized natural 

sites. In the deepest stratum, shell mound and natural reef assemblages were more similar with each other 

than in shallower waters (Figures 40–42), although two platforms (i.e., Gail and Hondo) harbored a somewhat different assemblage. 

Figure 34. A canonical discriminant analysis comparing the shell mound fish assemblages of shallow depth platforms (≤83 m) with

shallow natural sites. Data is based on centroids of surveys conducted in 2004–2009.

Natural Sites 

Edith

Ellen

Elly

Gilda 

Holly 

Irene 

Discriminant 2 (17%) 

Discriminant 1 (29%) 

Shallow Depth Platform Shell Mounds and Natural Sites

Canonical Discriminant Analysis

Centroids Standardized Transformed Densities 

-8 -6 -4 -2 0 2 4 6 8 10 

-10 

-8 

-6 

-4 

-2 

0 

2 

4 

6 
55

Figure 35. A comparison of densities of the two shallow depth platform shell mound and natural sites species clusters shown in 

Figure 36.

Shallow Depth Platform Shell Mounds and Natural Sites

Standardized Transformed Densities 

Natural Sites

Shell Mounds 

1 2 

Average Density 

Species Cluster 

-0.4 

-0.3 

-0.2 

-0.1 

0 

0.1 

0.2 

0.3 

0.4 

Figure 36. A cluster analysis of the characteristic species of platform shell mounds of shallow depth platforms (≤83 m) and shallow 

natural sites. Data is based on surveys conducted in 2004–2009.

Lingcod

Treefish

Starry rockfish YOY

Rosy rockfish

Squarespot rockfish

Starry rockfish

Sharpnose seafperch

Sheephead

Blacksmith

Senorita

Halfbanded rockfish YOY

Blackeye goby

Squarespot rockfish YOY

Painted greenling

Pileperch

White surfperch

Copper rockfish

Vermilion rockfish

Surfperch spp.

Gopher rockfish

Blue rockfish

Olive rockfish

Wolf-eel

Calico rockfish

Lingcod YOY

painted greenling YOY

Cabezon

Spotted scorpionfish

Sebastomus

Unidentified rockfishes

Unidentified rockfishes YOY

Bocaccio

Swordspine rockfish

Sebastomus YOY

Deepwater kelpfish

Honeycomb rockfish

Bluebanded ronquil

Unidentified sculpin

Unidentified sanddab

Unidentified flatfishes

Longspine combfish

Greenspotted rockfish

Flag rockfish

Halfbanded rockfish

Pink seaperch

Shortspine combfish

10 12 14 16 18 20

Height

Platform Shell Mounds and Natural Sites

Shallow Depth Category

More typical

of shallow-depth

natural sites

More typical

of shallow-depth

platform shell mounds
56

Figure 37. A canonical discriminant analysis comparing the shell mound fish assemblages of middle depthplatforms (84–136 m) 

with middle depth natural sites. Data is based on centroids of surveys conducted in 2004–2009.

Middle Depth Platforms Shell Mounds and Natural Sites

Canonical Discriminant Analysis

Centroids Standardized Transformed Densities 

-8 -6 -4 -2 0 2 4 6 8 

Discriminant 1 (37%) 

-10 

-8 

-6 

-4 

-2 

0 

2 

4 

6 

8 

Discriminant 2 (20%) 

Natural Sites

Grace Shell Mound 

Hildalgo Shell Mound 

Figure 38. A comparison of densities of the two middle depth platform shell mound and natural sites species clusters shown in 

Figure 39.

Middle Depth Platform Shell Mounds and Natural Sites

Standardized Transformed Densities 

Natural Sites

Shell Mounds 

-0.8 

-0.6 

-0.4 

-0.2 

0 

0.2 

0.4 

0.6 

Average Density 

1 2 

Species Cluster 
57

Figure 39. A cluster analysis of the characteristic species of platform shell mounds of middle depth platforms (84–136 m) and 

middle depth natural sites. Data is based on surveys conducted in 2004–2009.

Sebastomus

Sebastomus YOY

Spotted ratfish

Cowcod

Swordspine rockfish

Unidentified rockfishes

Bocaccio

Speckled rockfish

Starry rockfish

Pygmy rockfish

Squarespot rockfish

Starry rockfish YOY

Rosy rockfish

Squarespot rockfish YOY

Pygmy rockfish YOY

Unidentified rockfishes YOY

Lingcod

Greenstriped rockfish

Lingcod YOY

Flag rockfish YOY

Painted greenling

Shortspine combfish

Poachers

Unidentified flatfishes

Unidentified sanddab

Halfbanded rockfish

Longspine combfish

Flag rockfish

Vermilion rockfish

Blackeye goby

Pink seaperch

Cowcod YOY

Pacific sanddab

Greenspotted rockfish YOY

Greenblotched rockfish

Greenspotted rockfish

8 10 12 14 16

Height

Platform Shell Mounds and Natural Sites

Middle Depth Category

More typical of

middle-depth

natural sites

More typical of

middle-depth

platform shell mounds
58

Figure 40. A canonical discriminant analysis comparing the shell mound fish assemblages of deep depth platforms (137 m) with 

deep depth natural sites. Data is based on centroids of surveys conducted in 2004–2009.

Discriminant 2 (17%) 

Discriminant 1 (23%) 

Deep Depth Platform Shell Mounds and Natural Sites

Canonical Discriminant Analysis

Centroids Standardized Transformed Densities

-8 

-6 

-4 

-2 

0 

2 

4 

6 

-4 -2 0 2 4 6 8 10 

Natural Sites

Eureka Shell Mound 

Gail Shell Mound

Harmony Shell Mound

Harvest Shell Mound

Hermosa Shell Mound

Hondo Shell Mound

Figure 41. A comparison of densities of the two deep depth platform shell mound and natural sites speciesclusters shown in Figure 

42.

Average Density 

Deep Depth Platform Shell Mounds and Natural Sites

Standardized Transformed Densities 

Species Cluster 

1 2 

-0.4 

-0.2 

0 

0.2 

0.4 

Natural Sites 

Shell Mounds 
59

Unidentified sculpin

Rosethorn rockfish

Bank rockfish

Bank rockfish YOY

Cowcod

Bocaccio

Lingcod

Unidentified rockfishes

Spotted ratfish

Swordspine rockfish

Sebastomus

Sebastomus YOY

Unidentified rockfishes YOY

Speckled rockfish

Starry rockfish

Pygmy rockfish

Squarespot rockfish

Shortspine combfish

Cowcod YOY

Halfbanded rockfish

Flag rockfish

Greenspotted rockfish

Sharpchin rockfish

Pacific sanddab

Darkblotched rockfish

Longspine combfish

Blackgill rockfish

Splitnose rockfish

Unidentified thornyheads

Shortbelly rockfish

Greenstriped rockfish

Pacific argentine

Stripetail rockfish

Greenblotched rockfish

Pinkrose rockfish

Unidentified eelpout

Dover sole

Unidentified flatfishes

Unidentified poachers

Bluebarred prickleback

Unidentified pricklebacks

4 6 8 10 12 14 16 18

Height

Platform Shell Mounds and Natural Sites

Deep Depth Category

More typical of

deep-depth

natural sites

More typical of

deep-depth

platform shell mounds

Figure 42. A cluster analysis of the characteristic species of platform shell mounds of deep depth platforms (>137 m) and deep 

depth natural sites. Data is based on surveys conducted in 2004–2009.
60

We compared the species assemblages at Platform Hidalgo with that of nearby North Reef (Table 8), 

using data from 2005, 2006, and 2009. The platform and reef were always sampled on the same day, are 

both in the same water mass and about the same water depth (Hildalgo, 130 m; North Reef, 97 m). Analyses 

yielded four fish assemblages, midwater, bottom, shell mound, and reef (Figure 43), although there was considerable between-habitat sharing of species (Figures 44–45). In particular, a suite of both high-relief and 

low-relief species were typical of both Hidalgo bottom and North Reef. The density of YOY rockfishes was 

higher at Hidalgo than at North Reef in each of the three years (Figure 46). In 2009, densities of these YOY 

were 38 times higher at Hidalgo.

Figure 43. A canonical discriminant analysis comparing the midwaters, bottom, and shell mound fish assemblages of Platform 

Hidalgo with the fish assemblage of North Reef, 2005, 2006, and 2009. 

Discriminant 1 (97%) 

Discriminant 2 (2%) 

-250 -200 -150 -100 -50 0 50 

-15 

-10 

-5 

0 

5 

10 

15 

20 

North Reef 

Hildalgo Bottom 

Hildalgo Midwater 

Hildalgo Shell Mound 

Platform Hidalgo and North Reef

Canonical Discriminant Analysis 

Standardized Transformed Data
61

Table 8. Numbers and densities (average number per 100 m2) of fish species observed at North Reef 2005–2006 and 2008–2009.

Species Number Density

Pygmy rockfish 596 5.9

Squarespot rockfish 589 5.5

Vermilion rockfish 422 5.3

Halfbanded rockfish 387 4.0

Unidentified rockfish YOY 343 4.5

Pygmy rockfish YOY 340 4.2

Greenspotted rockfish 291 3.3

Sebastomus spp. 180 2.0

Yellowtail rockfish 101 1.2

Shortspine combfish 99 1.2

Blackeye goby 97 1.1

Starry rockfish 93 1.1

Greenstriped rockfish 45 0.5

Sebastomus YOY 45 0.5

Speckled rockfish 41 0.4

Greenblotched rockfish 38 0.5

Pink seaperch 38 0.4

Bocaccio 30 0.4

Unidentified rockfishes 26 0.3

Flag rockfish 24 0.3

Swordspine rockfish 22 0.2

Unidentified fishes 20 0.2

Widow rockfish 16 0.2

Starry rockfish YOY 13 0.2

Rosy rockfish 11 0.1

Cowcod 10 0.1

Unidentified combfishes 9 0.1

Longspine combfish 9 0.1

Pinkrose rockfish 8 <0.1

Species Number Density

Canary rockfish 7 <0.1

Lingcod 6 <0.1

Unidentified flatfishes 5 <0.1

Longnose skate 2 <0.1

Pink rockfish 2 <0.1

Rosethorn rockfish 2 <0.1

Squarespot rockfish YOY 2 <0.1

Widow rockfish YOY 2 <0.1

Unidentified cusk-eel 1 <0.1

English sole 1 <0.1

Greenspotted rockfish YOY 1 <0.1

Greenstriped rockfish YOY 1 <0.1

Kelp greenling 1 <0.1

Lingcod YOY 1 <0.1

Olive rockfish 1 <0.1

Painted greenling 1 <0.1

Red brotula 1 <0.1

Shortbelly rockfish 1 <0.1

Unidentified ronquil 1 <0.1

Tiger rockfish 1 <0.1

Yelloweye rockfish 1 <0.1

Total 3,984

Minimum number of species 37

Total rockfish YOY 747

Total rockfishes 3,692

Rockfish YOY comprised 18.8% of all fishes surveyed

All rockfishes comprised 92.7% of all fishes surveyed

Discussion

This research confirms and expands the observations we have previously reported upon (summarized 

in Love et al. 2003). The fish assemblages of California oil and gas platforms are quite diverse and not easily 

summarized. Nevertheless it is clear that:

1) There are three fish assemblages around each platform (midwaters, bottom, shell mound); 

2) Within each of these assemblages, midwater assemblages tend to be similar across platforms, 

 while there are substantial differences among those found at bottoms and shell mounds. 

 Assemblages at any platform changed little over the course of the study; 

3) In general, the assemblages of platforms and natural sites are different, and these differences 

 are mainly based on variability in species’ densities; 

4) All of the platforms we surveyed serve as nursery grounds for a variety of rockfishes and other 

 taxa and, in general, platform habitats harbor higher densities of young fishes than do many 

 natural sites. 

5) The bottoms of some platforms harbor higher densities of larger, and economically 

 important, fishes than do most or all natural sites.
62

Figure 44. A comparison of densities of the five Platform Hidalgo midwaters, bottom, and shell mound and North Reef species 

clusters shown in Figure 45.

North Reef 

Hildalgo Bottom 

Hildalgo Midwater 

Hildalgo Shell Mound 

Platform Hildalgo and North Reef

Standardized Transformed Densities 

Average Density 

1 2 3 4 5 

-0.8 

-0.6 

-0.4 

-0.2 

0 

0.2 

0.4 

0.6 

0.8 

1 

1.2 

1.4 

Species Cluster 
63

Figure 45. A cluster analysis of the characteristic species of midwaters, bottom, and shell mound of Platform Hidalgo and North 

Reef. Data is based on surveys conducted in 2005, 2006, and 2009.

Unidentified rockfish YOY

Painted greenling

Painted greenling YOY

Squarespot rockfish YOY

Unidentified rockfishes

Widow rockfish YOY

Cowcod YOY

Pink seaperch

Sebastomus YOY

Shortspine combfish

Blackeye goby

Pygmy rockfish YOY

Cowcod

Yellowtail rockfish

Vermilion rockfish

Bocaccio

Pygmy rockfish

Starry rockfish

Squarespot rockfish

Widow rockfish

Flag rockfish

Greenblotched rockfish

Greenstriped rockfish

Sebastomus spp.

Greenspotted rockfish

Halfbanded rockfish

Swordspine rockfish

Rosy rockfish

Canary rockfish

Lingcod

3 4 5 6 7 8 9

Height

Platform Hidalgo and North Reef

More typical of

Hidalgo bottom

and midwaters

More typical of Hidalgo bottom, shell mound, and North Reef

More typical of

Hidalgo bottom

and North Reef

More typical of

Hidalgo bottom

and North Reef

More typical of

Hidalgo bottom

and shell mounds
64

Platform Hidalgo Midwater and North Reef

Young-of-the-Year Rockfish Densities 2005-2009

112.71

10.43 8.34 3.38

689.55

18.19

Average Density 

2005 2006 2009

Hidalgo

North Reef

Hidalgo

North Reef

Hidalgo

North Reef

0 

20 

40 

60 

80 

100 

120 

600 

700 

Figure 46. Densities of young-of-the-year rockfishes at Platform Hidalgo midwaters and North Reef, 2005, 2006, and 2009.

A range of juvenile and adult fishes inhabits platform midwaters, although this assemblage has much 

in common among all of the platforms surveyed. Typical species whose juveniles recruit to platforms include bocaccio, flag, shortbelly, squarespot, and widow rockfishes, and also of such taxa as blacksmith, garibaldi, and painted greenling. Depending on platform, this assemblage also contains the adults of a number 

of nearshore reef species (e.g., cabezon, garibaldi, kelp bass, painted greenling, pile perch, and sheephead). 

With the exception of an occasional school of jackmackerel, we did not observe large number of pelagic 

species in this habitat. The more northerly platforms, particularly those north of Point Conception, harbor 

fewer nearshore species and thus contain a lower overall number of taxa. Because juvenile recruitment is 

driven by oceanographic conditions, it is not surprising that rockfish recruitment is highly variable between 

years and platforms (Figure 47a, b). The role that habitat complexity plays in influencing midwater assemblages is discussed in Task 2.

The bottom assemblages are quite variable among platforms and the compositions of these assemblages are driven both by platform architecture and bottom depth. As noted by Love and York (2006), those 

platforms that have a bottom cross beam that is undercut to form a “crevice” (e.g., Gail, Hidalgo, Irene) 

have higher densities of shelter-seeking fishes (e.g., bocaccio, flag and canary rockfishes, cowcod) than do 

those structures (e.g., Hermosa and Harvest) whose cross beams are either buried in mussel shells or deeply 

undercut (forming a wide gap). These latter platforms tend to have bottoms that are dominated by such species as halfbanded rockfish, a schooling mobile taxa that is not limited to complex habitats. Bottom depth is 

also an important determinant of species composition as the three species clusters that we observed around 

platform bottoms (linked to depth) are similar to those that occur over natural sites within the southern 

California Bight (Love et al. 2009). Interestingly, the peaks in species richness that we observed in platforms 

situated in about 60–80 m also occurred at natural sites throughout the southern California Bight (Love et 

al. 2009).
65

Figure 47a. Densities of young-of-the-year rockfishes in the midwaters of all platforms, by year. NS = platform not sampled 

and T = trace. 

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

1000

1500

600

550

500

150

100

50

0

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

200420052006200720082009200420052006200720082009200420052006200720082009

200420052006200720082009

200420052006200720082009

200420052006200720082009

200420052006200720082009200420052006200720082009

200420052006200720082009200420052006200720082009

200420052006200720082009200420052006200720082009

Irene Hidalgo Harvest Hermosa

Harmony Heritage Hondo Holly

A B C Hillhouse

NS NS NS NS NS NS NS NS NS NS NS NS NS

T NS NS NS NS NS NS NS NS NS T NS T NS T NS T NS T T

T NS T NS NS T NS 0 NS NS NS 0 NS NS T NS NS T NS NS

Density of All Young-of-the-Year (per 100 m2) Rockfishes

2004–2009
66

Figure 47b. Densities of young-of-the-year rockfishes in the midwaters of all platforms, by year. NS = platform not sampled 

and T = trace. 

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

350

800

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

600

700

300

250

200

150

100

50

0

450

500

400

250

200

150

100

50

0

200420052006200720082009200420052006200720082009

20042005200620072008

2009

200420052006200720082009

200420052006200720082009

200420052006200720082009

200420052006200720082009

200420052006200720082009200420052006200720082009

Henry Habitat Grace

Gail

Gilda

Eureka

Edith Elly Ellen

T NS NS NS NS NS NS NS T NS NS NS

T T

T NS T T

NS T T

NS T T T NS T T NS T T

Density of All Young-of-the-Year (per 100 m2) Rockfishes

2004–2009
67

Although platform bottoms often harbor large numbers of adults, the YOYs of a number of taxa are 

also found there. Some of these young juveniles (e.g., bocaccio, painted greenling, and squarespot rockfish) 

also occupy the platform midwaters and these individuals may have first recruited to the shallow portions of 

the platform before moving to the bottom. However, the YOYs of other fishes (e.g., lingcod and halfbanded 

rockfish) are only rarely found in platform midwaters and these may recruit from the plankton directly to 

the bottom. 

In contrast to the robust and sometimes complex habitat that platform bottoms provide, the shell 

mounds are of only moderate relief and complexity. Because of this, most of the dominant shell mound species are those that are adapted to living over relatively low relief. Typical species include the young of larger 

taxa, such as cowcod and lingcod, along with a range of diminutive species, including painted greenling, 

pink seaperch, and a variety of poachers, combfishes, and rockfishes. With only a few exceptions, these are 

small, solitary, and often benthic fishes. Exceptions are a few schooling taxa, such as halfbanded rockfish, 

that are often found in groups of hundreds or even thousands. This pattern appears to break down somewhat in deeper waters, where some larger rockfishes, such as greenblotched, greenspotted, and pinkrose, occupy both the platform bottoms and shell mounds. These species may be more “generalist” in their habitat 

needs and may move more freely from bottom to shell mound. 

The species assemblages at every platform were relatively stable throughout the survey period. That 

is, the overall interannual variability within an assemblage was low (Figures 5, 9, 13). This is not to say 

that densities of all of the species in an assemblage were identical from year to year. Clearly, for instance, 

some habitats, particularly midwater ones, are subject to great interannual variation in rockfish recruitment. 

However, despite these periodic influxes, each assemblage at every platform has a suite of “typical” species 

that do not appear to appreciably vary from year to year. 

Generally, all three of the platform species assemblages are different from those at natural sites. Importantly, these distinctions are due more to differences in species’ densities rather than to the presence or 

absence of certain taxa (Table 4). That is, there are relatively few species that are present in large numbers at 

either a platform or natural site and are completely absent from the other. What might promote these differences? First, as noted in our previous surveys (Love et al. 2003), there are generally higher densities of juvenile fishes (particularly YOY fishes) at many platforms than at most natural sites (Figure 48). For instance, 

most of the top 20 sites with highest YOY rockfish densities measured either in a single year or averaged over 

the six-year survey, were at platforms (Table 9). These high densities occurred not only in platform midwaters but also at bottoms and occasionally shell mounds (Table 9). And, as noted previously, even reefs that 

are in close proximity to platforms (e.g., North Reef and Hidalgo) almost invariably have lower densities 

of YOY rockfishes (see Figure 46). The enhanced nursery function exhibited by platforms is due to several 

factors. First, during its pelagic stage, a juvenile rockfish is more likely to encounter a platform (extending 

from sea floor to surface) than the deep natural reefs we surveyed. Second, with a few exceptions, platform 

midwaters and shell mounds, in particular, tend to harbor relatively few large fishes and thus predation rates 

on YOYs are likely low (Love and Schroeder 2006). 

Most of the fishes that we observed living around platforms and natural sites were relatively small, 

primarily 15 cm or less in length (Figure 48). These were both juveniles of a variety of taxa (e.g., bocaccio, 

lingcod, widow rockfish) and dwarf species (e.g., painted greenling, squarespot and halfbanded rockfishes). 

Larger fishes (25 cm and above) were less common (Figures 48, 49) and these were most often found around 

platform bottoms (Figure 49). In addition, and supporting observations from earlier surveys (Love et al. 

2003), some platform bottoms (e.g., Gail and Irene), harbor higher densities of species of economic importance (both juveniles and adults) than do most, or all, natural sites (Figures 27, 30, 33). It is likely that 

these high densities are due to a combination of several factors. First, and as documented by Love and York 

(2006) and Love et al. (2006), many economically important rockfishes (e.g., cowcod, bocaccio, and cop-
68

A) B)

ROCKFISH YOY ALL ROCKFISH YOY

Platform Density Platform Density

Edith, Bottom, 2005 2,821 Edith Bottom 1,116

Edith, Bottom, 2009 1,570 Irene Midwater 450

Irene Midwater, 2009 1,191 Ellen Midwater 314

Elly Bottom, 2005 836 Wolf Rock 224

Ellen Midwater, 2009 814 Elly Bottom 211

Hidalgo Midwater, 2009 690 Hidalgo Midwater 210

Edith Bottom, 2007 597 Grace Midwater 170

Irene Midwater, 2008 572 Edith Shell Mound 167

Irene Midwater, 2004 538 Anacapa Passage 132

Irene Bottom, 2009 514 Elly Midwater 115

Edith Shell Mound 2005 510 Gull Island 114

Grace Midwater 2004 484 Irene Bottom 108

Edith Bottom, 2006 396 Irene Shell Mound 84

Ellen Midwater, 2005 379 Eureka Midwater 83

Anacapa Passage, 2009 368 Ellen Bottom 73

Anacapa Passage, 2005 341 Gilda Midwater 56

Edith Shell Mound, 2009 333 Holly Midwater 52

Irene Shell Mound, 2009 277 Short Banks 51

Eureka Midwater, 2009 268 Northwest Edith Reef 49

Ellen Midwater, 2008 246 Northeast Anacapa 45

Table 9. Locations with the highest densities of young-of-the-year rockfishes (YOY) for A) a single year and B) averaged over all 

years. Density in number of fish per 100 m2.

per rockfish) are primarily found over complex substrata and mostly occupy crevices and other sheltering 

sites. Platforms that have bottom cross beams that are undercut to form a narrow gap (e.g., Irene and Gail) 

have higher densities of these species than those that do not (e.g., Hermosa and Harvest). As demonstrated 

in Task II, a unique complexity in the midwaters of one platform produced a midwater species assemblage 

similar to that found on the bottom. Thus, the importance of structural complexity to this suite of species 

should not be under estimated. Second, many, or perhaps most, platforms act as de facto marine reserves, as 

fishing pressure at these structures is likely lower than at natural sites. Fishing pressure appears to be lower 

for at least two reasons. First, some platforms are sited well away from coastal ports, in areas that are often 

exposed to wind, and thus are difficult to access. Of perhaps more importance is the perceived reluctance of 

many platform operators, in a post-9/11 world, to have vessels close to their structures. 

The shell mounds surrounding California platforms are a unique feature of these structures. They are 

created by the dislodgement (through wave action and platform cleaning) of attached invertebrates from 

the upper parts of a jacket. Composed primarily of living and dead mussels, and associated marine life, they 
69

Figure 48. A length frequency histogram of all fishes observed at platform midwaters, bottom, and shell mounds.

Natural Sites 

Platform Bottom 

Platform Midwaters 

Platform Shellmound 

Percent 

Length (cm) 

Length Frequencies of All Fishes Observed

5 10 15 20 25 30 35 40 45 50 

>50 

0 

5 

10 

15 

20 

25 

30 

35 

40 

45 

50 

Figure 49. A length frequency histogram of all fishes larger than 25 cm observed at platform midwaters, bottom, and shell mounds. 

Note that the percent observed on the y-axis is on a log scale. 

Natural Sites 

Platform Bottom 

Platform Midwaters 

Platform Shellmound 

Length (cm) 

Percent 

Length Frequencies of All Fishes Observed,

25 cm and Larger

25 30 35 40 45 50 

>50 

0.01 

0.1 

1 

10 
70

form an extensive web of low, but rugose, sea floor. The relatively small crevices created by mussel shells deter large numbers of many high-relief species (such as copper and vermilion rockfishes, and adult cowcod) 

from venturing onto these areas. Rather, most shell mound species are either the juveniles of larger species, 

whose juvenile stages require small sheltering sites (e.g. cowcod, see Love and Yoklavich 2008), or somewhat 

generalist species that live over 1) soft sea floors, 2) the ecotones between soft and low-relief hard bottom, 

and 3) low-relief reefs. While shell mound assemblages in shallow and middle depth waters tend to be different from those of natural sites of the same depths (Figures 34 and 37), deep depth shell mound assemblages 

more closely resemble those at natural sites (Figure 40).

This is likely because, as noted in Love et al. (2009b), reefs in the deeper waters of California tend to be 

low relief and thus more like shell mounds. 

Acknowledgements

We thank S. Clark, S. Liles, M. Edwards, M. McCrea, and A. Scarborough for their support. Research 

was conducted aboard the submersible Delta, piloted by C. Ijames and J. Lilly, with assistance of the crew of 

the R/V Velero. 

Literature Cited

Emery, B. M., L. Washburn, M. S. Love, M. N. Nishimoto, and J. C. Ohlmann. 2006. Do oil and gas platforms

off California reduce recruitment of bocaccio (Sebastes paucispinis) to natural habitats? Analysis on

trajectories derived from high frequency radar. Fish. Bull. 104:391-400.

Goddard, J. H. R. and M. S. Love. 2007. Megabenthic invertebrates on shell mounds under oil and gas 

platforms off California. U.S. Minerals Management Service, OCS Study MMS 2007-007.

Love, M. S. and S. R. Goldberg. 2009. A histological examination of the ovaries of Pacific sanddab, 

Citharichthys sordidus, captured at two oil platforms and two natural sites in the southern California 

Bight. Bull. S. Calif. Acad. Sci. 108:45-51.

Love, M. S. and D. M. Schroeder. 2006. Ecological performance of OCS platforms as fish habitat off 

California. OCS Study MMS 2004-005. Marine Science Institute, University of California, Santa 

Barbara. MMS Cooperative Agreement Number 1435-01-03-CA72694.

Love, M. S. and D. M. Schroeder. 2007. A characterization of the fish assemblage of deep photic zone rock 

outcrops in the Anacapa Passage, Southern California, 1995 to 2004. with evidence of a regime shift.

 ÇalCOFI Rep. 48:165-176.

Love, M. S. and M. Yoklavich. 2008. Habitat characteristics of juvenile cowcod, Sebastes levis (Scorpaenidae), 

in Southern California. Env. Biol. Fish. 82:195-202. 

Love, M. S. and A. York. 2005. A comparison of the fish assemblages associated with anoil/gas pipeline and 

adjacent seafloor in the Santa Barbara Channel, Southern California Bight. Bull Mar. Sci. 77:101-117.

Love, M. S. and A. York. 2006. The role of bottom crossbeam complexity in influencing the fish assemblages

 at California oil and gas platforms. Fish. Bull. 104:542-549.

Love, M. S., J. Caselle and L. Snook. 1999. Fish assemblages on mussel mounds surrounding seven oil 

platforms in the Santa Barbara Channel and Santa Maria Basin. Bull. Mar. Sci. 65:497-513.

Love, M. S., J. E. Caselle and L. Snook. 2000. Fish assemblages around seven oil platforms in the Santa 

Barbara Channel. Fish. Bull. 98:96-117.

Love, M. S., M. Nishimoto, and M. Saiki. 2009. Reproductive ecology and body burden of resident fish prior 

to decommissioning. MMS OCS Study 2009–019. Marine Science Institute, University of California, 

Santa Barbara, California. MMS Cooperative Agreement Number 1435–01–05–CA–39315.
71

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.

Love, M. S., D. M. Schroeder, and B. Lenarz. 2006. Gimme shelter: the importance of crevices to some fish

 species inhabiting a deeper-water rocky outcrop in southern California. CalCOFI Rep. 47:119-126.

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

 platforms and natural outcrops on fishes in southern and central California: a synthesis of 

information. U. S. Department of the Interior, U. S. Geological Survey, Biological Resources Division, 

Seattle, Washington, 98104, OCS Study MMS 2003-032.

Love, M. S., M. Yoklavich, and D. M. Schroeder. 2009. Demersal fish assemblages in the Southern California 

Bight based on visual surveys in deep water. Env. Biol. Fish. 874:55-68.

Love, M. S., E. Brothers, D. M. Schroeder, and W. H. Lenarz. 2007. Ecological performance of young-of-the 

year blue rockfish (Sebastes mystinus) associated with oil platforms and natural reefs in California as 

measured by daily growth rates. Bull. Mar. Sci. 80:147-157.

Love, M. S., M. Nishimoto, D. Schroeder, and J. Caselle. 1999. The ecological role of natural reefs and oil and

 gas production platforms on rocky reef fishes in Southern California. Final Interim Report. 

OCS Study MMS 99-0015.

Love, M. S., M. Nishimoto, D. Schroeder, A. Gharrett, and A. Gray. 1997. The ecological role of natural reefs 

and oil and gas production platforms on rocky reef fishes in southern California. 

USGS/BRD/CR-1997-0007.

Love, M. S., D. M. Schroeder, W. Lenarz, A. MacCall, A. Scarborough-Bull, and L. Thorsteinson. 2006. 

Potential utility of offshore marine structures in rebuilding an overfished rockfish species, bocaccio 

(Sebastes paucispinis). Fish. Bull. 104:383-390.

Nishimoto, M. M., M. S. Love, L. Washburn, D. M. Schroeder, and B. M. Emery. 2007. Assessing the fate of

 juvenile rockfish at offshore petroleum platforms and natural reefs in the Santa Barbara Channel. 

U. S. Minerals Management Service, OCS Study MMS 2007-008.

Page, H. M., J. E. Dugan, D. M. Schroeder, M. M. Nishimoto, M. S. Love, and J. C. Hoesterey. 2007. Trophic 

links and condition of a temperate reef fish: comparisons among offshore oil platform and natural 

reef habitats. Mar. Ecol. Prog. Ser. 344:245-256.

R (2005) The R Foundation for Statistical Computing. Version 2.1.1 (2005-06-20). 

Schroeder, D. M. and M. S. Love. 2004. Ecological and political issues surrounding oil platform 

decommissioning in the Southern California Bight. Ocean and Coastal Management 47:21-48.
72

Task 2: A Comparison of Fish Assemblages in the Midwaters of Two California Oil and Gas 

Platforms

Milton S. Love and William H. Lenarz

Abstract

Between 2005 and 2008, using the manned research submersible Delta, we compared the midwater 

fish assemblages of two southern California platforms, Gail and Eureka. Platform Gail is a typical California 

platform, with rounded crossbeams and pilings, while the midwater jacket of Eureka, studded with fascicles 

of pilings and bowl-shaped piling guides, is much more complex. While the assemblages of both platforms 

were dominated by rockfishes (Sebastes), there were also significant differences. Compared to Gail, Eureka 

harbored 1) higher densities both of all species combined and of most species held in common, 2) far more 

mature individuals of most species, 3) greater species richness, and 4) much higher densities of species that 

live over complex high relief. We propose that from a fish’s perspective, the complex midwater jacket of Eureka, with its many sheltering sites, mimics rugose natural reefs. This research both re-enforces the conclusion that many reef species have quite specific habitat requirements and that the platform decommissioning 

process must examine each platform individually. 

Introduction

In general, there are two distinct fish assemblages living around the jackets (pilings and crossbeams) 

of deeper-water California oil and gas platforms (with bottom depths >100 m). First, subadult and adult 

fishes of a number of benthic species (primarily rockfishes, genus Sebastes) inhabit the platform jacket-sea 

floor complex (Love et al. 2000). Many of these species associate with the bottom crossbeam, particularly 

where that crossbeam has been undercut leaving a long crevice (Love and York 2006). The midwaters (at 

depths below about 40 m) around most California platforms serve primarily as nursery grounds for rockfishes. The adults of those benthic species adapted to resting on or sheltering in complex habitat are rarely 

observed in the platform midwaters (Love et al. 2000).

The midwater structures of most California platforms are similarly configured. The platform jacket is 

a framework of rounded steel crossbeams and tubular vertical sleeves. The main pilings are driven through 

 EUREKA GAIL

Depth Perimeter Years Depth Perimeter Years

 Length Surveyed Length Surveyed

59 194 3 49 189 4

79 206 3 70 203 3

101 218 3 93 217 4

123 230 4 116 232 3

144 243 4 141 246 4

165 254 4 166 264 3

190 268 4 195 283 4

Table 1. Depth (m) and perimeter length (m) of cross beams surveyed and number of years survey, platforms Gail 

and Eureka, 2005-2008.
73

Figure 1. Physical characteristics of the midwater jackets of Platforms Gail and Eureka. Crossbeams (1A) and pilings (1C) of Plat

form Gail are cylindrical and lack structural complexity. Crossbeams of Platform Eureka have bowl-shaped skirt piling 

guides (view from outside a piling guide looking inwards toward a crossbeam in rear (1B) and the pilings (1D) are in 

groups of three (pilings labeled 1, 2, 3) creating a series of crevices. Adult widow rockfish, Sebastes entomelas are pictured 

in Figure 1D. 
74

Figure 2. Location and bottom depths of Platforms Gail (open circle) and Eureka (closed diamond).

C A L I F O R N I A

Area

Detailed Area

Detailed

Santa

Barbara

Ventura

Santa Cruz

Island

Anacapa

Island

Gail

224m

Long Beach Palos

Verdes

Eureka

212m

Latitude (°N)

Longitude (°W)

34°00'

33°90'

34°10'

34°20'

34°30'

Latitude (°N)

33°35'

33°45'

119°40' 119°30' 119°20' 119°10'

Longitude (°W)

118°10' 118°00'

Figure 2
75

9 11 13 15

0

50

100

150

200

250

Eureka

Gail

2005

2006

Temperature (°C)

Depth (m)

Figure 3

Figure 3. Ambient water temperatures during fish surveys of the midwaters of platforms Gail and Eureka during 2005 (shallow 

waters) and 2006 (deeper depths). Faulty data from the ctd of the Delta research submersible precluded temperature data from the 

complete water column during either year. 

these sleeves, which are located at the corners and sometimes at widely spaced intervals between the corners 

of the jacket (Figure 1a, c). While the jacket is covered with sessile invertebrates (e.g., mussels, sea stars, sea 

anemones), most of these organisms are small and do not form significant vertical relief. 

Platform Eureka is structurally unique among California platforms. Instead of pilings driven through 

the vertical sleeves, it has a series of relatively narrow “skirt pilings” that are attached to the outside of the 

jacket. The skirt pilings are in fascicles of three with a relatively narrow space between each. To guide these 

pilings into the sea floor, large circular guides were constructed at each crossbeam directly above each piling’s location (Figure 1b, d). Thus, compared to a typical California platform, these skirt pilings and guides 

add a great deal of vertical and horizontal relief to the jacket midwaters. 

In this study, we compare the midwater fish assemblages of Platform Eureka with that of Platform Gail, 

a more typically configured platform. These two platforms are similar in a number of respects. They were 

constructed at about the same time, Eureka in 1984 and Gail in 1987. Both platforms are about 13 km from 

shore and stand in similar depths: Gail in 224 m, Eureka in 212 m. Both have nine midwater crossbeams and 

these crossbeams are situated at comparable depths (Table 1). Although Eureka is found about 118 km to the 

southeast of Gail (Figure 2), both platforms are in the southern California Bight and are bathed by waters 

of similar temperatures (Figure 3). Lastly, the dominant natural reef species in the two areas are comparable 

(Ebeling et al. 1980; Stephens et al. 1984; Love et al. 2009).

Methods

Fish Surveys

We surveyed fishes in the midwaters of platforms Eureka and Gail (Figure 2) annually between 2005 

and 2008 during September or October. In each year, the two platforms were surveyed within three days of 

each other. We used the Delta research submersible, a 4.6-meter, 2-person vessel, operated by Delta Oceano-
76

Table 2. Common and scientific names of fishes mentioned in the text.

Bank rockfish Sebastes rufus 

Blackgill rockfish Sebastes melanostomus 

Blacksmith Chromis punctipinnis

Blue rockfish Sebastes mystinus 

Bocaccio Sebastes paucispinis 

Cabezon Scorpaenichthys marmoratus 

California sheephead Semicossyphus pulcher 

Copper rockfish Sebastes caurinus

Darkblotched rockfish Sebastes crameri 

Dwarf-red rockfish Sebastes rufianus 

Flag rockfish Sebastes rubrivinctus

Freckled rockfish Sebastes lentiginosus

Garibaldi Hypsypops rubicundus 

Gopher rockfish Sebastes carnatus

Greenblotched rockfish Sebastes rosenblatti 

Greenspotted rockfish Sebastes chlorostictus 

Greenstriped rockfish Sebastes elongatus 

Halfbanded rockfish Sebastes semicinctus

Honeycomb rockfish Sebastes umbrosus

Kelp bass Paralabrax clathratus

Kelp greenling Hexagrammos decagrammus

Kelp rockfish Sebastes atrovirens

Lingcod Ophiodon elongatus

Northern anchovy Engraulis mordax

Opaleye Girella nigricans

Pacific hake Merluccius productus

Painted greenling Oxylebius pictus

Pinkrose rockfish Sebastes simulator

Popeye catalufa Pristigenys serrula 

Pygmy rockfish Sebastes wilsoni 

Rosethorn rockfish Sebastes helvomaculatus 

Rosy rockfish Sebastes rosaceus

Sharpchin rockfish Sebastes zacentrus

Shortbelly rockfish Sebastes jordani 

Speckled rockfish Sebastes ovalis

Squarespot rockfish Sebastes hopkinsi 

Starry rockfish Sebastes constellatus

Swordspine rockfish Sebastes ensifer 

Treefish Sebastes serriceps

Vermilion rockfish Sebastes miniatus 

Widow rockfish Sebastes entomelas 

Yelloweye rockfish Sebastes ruberrimus 
77

Table 3. Total numbers and average densities (fish per 100 m2) of all fishes observed at the crossbeams of platforms Eureka (depths = 

59, 79, 101, 123, 144, 165, and 190 m) and Gail (depths = 49, 70, 93, 116, 141, 166, and 195 m), 2005-2008. Starred species were observed 

at only one of the two platforms.

PLATFORM EUREKA PLATFORM GAIL

Average Average

Species Number Density Species Number Density

Squarespot rockfish 9893 101.3 Squarespot rockfish 1118 11.1

Unidentified rockfishes1 1448 15.7 Bocaccio 1031 10.0

Widow rockfish 794 5.7 Unidentified rockfishes1 403 3.7

*Speckled rockfish 584 4.9 Widow rockfish 220 2.1

Unidentified Sebastomus2 137 1.6 Painted greenling 73 0.7

*Blue rockfish 135 1.1 Flag rockfish 45 0.5

Bocaccio 72 0.7 Unidentified Sebastomus2 33 0.3

Copper rockfish 62 0.7 Pinkrose rockfish 16 0.1

Pinkrose rockfish 53 0.4 Unidentified fishes 13 0.1

*Rosy rockfish 50 0.4 Cabezon 6 0.1

Greenblotched rockfish 46 0.3 Darkblotched rockfish 6 0.1

Flag rockfish 39 0.4 *Pacific hake 3 <0.1

Unidentified fishes 34 0.3 Copper rockfish 2 <0.1

*Starry rockfish 32 0.2 Sharpchin rockfish 2 <0.1

*Pygmy rockfish 30 0.3 *Unidentified sculpin 1 <0.1

Bank rockfish 29 0.2 Gopher rockfish 1 <0.1

*Kelp rockfish 26 0.3 *Kelp greenling <0.1

Dwarf-red rockfish 20 0.2 Greenspotted rockfish 1 <0.1

Greenspotted rockfish 19 0.1 Swordspine rockfish 1 <0.1

Cabezon 17 0.1 Bank rockfish 1 <0.1

Darkblotched rockfish 15 0.1 *Northern Anchovy 1 <0.1

Shortbelly rockfish 13 0.1 Greenblotched rockfish 1 <0.1

Painted greenling 12 0.1 Shortbelly rockfish 1 <0.1

*Freckled rockfish 10 0.1 Average Total Density 28.7

*Honeycomb rockfish 9 0.1

*Blacksmith 8 0.1

Swordspine rockfish 7 0.1

Gopher rockfish 4 <0.1

*Rosethorn rockfish 3 <0.1

Sharpchin rockfish 2 <0.1

*Vermilion rockfish 2 <0.1

*Blackgill rockfish 1 <0.1

*Popeye catalufa 1 <0.1

*Treefish 1 <0.1

*Yelloweye rockfish 1 <0.1

Average Total Density 135.9

Minimum Number of Species 32 20

Total Number of Fishes Observed 13,609 2,980

1

Primarily young-of-the-year rockfishes

2

Potentially freckled, greenblotched, greenspotted, honeycomb, pinkrose, rosy, starry, or swordspine rockfishes. 
78

graphics of Oxnard, California. In the platform midwater, we conducted surveys along each of the platform’s 

horizontal beams, located at 20 to 30 m intervals between near-surface waters and the bottom. We conducted belt transects around the horizontal beams at a distance of approximately 2 m from the platform, while 

the submersible maintained a speed of about 0.5 knots. 

Submersible surveys were conducted during daylight hours between one hour after sunrise and two 

hours before sunset. During each transect, the researcher made observations from a viewing port on the 

starboard side of the submersible. An externally mounted hi-8 mm video camera with associated lights 

Table 4. Results of ANOVAS based on fish densities around the midwater cross beams of platforms Eureka and Gail, 2005-2008 with 

platform, depth, and year as factors. Because not all cross beams were surveyed at each platform in each year, we present two separate 

analyses. Figure 1A includes data from 2005, 2007, and 2008, from four midwater depths, 50-59, 90-101, 140-141, and 190-192 m. Figure 1B includes data from 2005, 2006, and 2007 and includes surveys of cross beams at 116-123, 141-144, 165-166, and 190-195 m. ** 

= significant at 99% level, * = significant at 95% level, ns = non significant.

1A

Species Platform Depth Year Platform x Depth Platform x Year Depth x Year

Squarespot rockfish ** ** ns ns ns ns

Bocaccio ns ns ns ns ns ns

Widow rockfish * ns ns * ns ns

Speckled rockfish ** ** ns ** ns ns

Pinkrose rockfish ns ** ns ns ns ns

Blue rockfish   ns **  ns ns

Copper rockfish ** ** ns ** ns ns

Painted greenling * * ns ns ns ns

Flag rockfish ns * ns ns ns ns

Bank rockfish ** ** ns * ns ns

1B

Species Platform Depth Year Platform x Depth Platform x Year Depth x Year

Squarespot rockfish ** ** ns ns ns ns

Bocaccio ns * ns ns ns ns

Widow rockfish ** ns * ns ns ns

Speckled rockfish ** ns ns ns ns ns

Pinkrose rockfish * ** * ns ns ns

Greenblotched rf ** ** ns * ns ns

Bank rockfish ** * * ns ns ns

Darkblotched rf ns * ns ns ns ns

Flag rockfish ns ns ns ns ns ns

Starry rockfish ** ns ns ns ns ns
79

0

350

300

250

200

150

100

50

25 45 65 85 105 125 145 165 185 205 225

Depth (m)

Average Fish Density (100m^2)

Eureka

Gail

All Fishes Observed

Figure 5

0

20

18

16

14

12

10

8

6

2

4

Depth (m)

Number of Species

Eureka

Gail

0 50 100 150 200 250

Figure 4

Figure 4. The number of species observed at each cross beam, platforms Gail and Eureka, summarized for 2005-2008.

Figure 5. Average densities of fishes surveyed at each crossbeam, platforms Gail and Eureka, for 2005-2008. 
80

filmed the same viewing fields as seen by the observer. Images recorded by the camera were laid down on 

tape. The observer identified, counted and estimated the lengths of all fishes and verbally recorded those data 

on the videotape. All fishes within two meters of the submersible were counted. Fish lengths were estimated 

using a pair of parallel lasers mounted on either side of the external video camera. The projected reference 

points were 20 cm apart and were visible both to the observer and in the video camera image. Many years 

of experience along the Pacific Coast have shown that if the Delta is moving at a constant and slow rate of 

speed, as in these surveys, there is very little obvious effect on most fishes, particularly rockfishes. Certainly, 

we noticed virtually no movement from most of the fishes in this study as the research submersible passed 

All Species

0

5

10

15

20

25

30

35

40

45

5 10 15 20 25 30 35 40 45+

Total Length (cm)

Percent

Eureka – 13,608 total number of fishes

Gail – 2980 total number of fishes

5 10 15 20 25 30 35 40 45+

Bocaccio

0

5

10

15

20

25

30

35

40

45

50

5 10 15 20 25 30 35 40 45+

Total Length (cm)

Percent

Eureka – 72 total 

Gail – 1031 total 

Squarespot Rockfish

10

20

30

40

50

60

Percent

0

5 10 15 20 25 30 35 40 45+

Total Length (cm)

Eureka – 9893 total 

Gail – 8915 total 

Widow Rockfish

0

10

20

30

40

50

60

70

80

5 10 15 20 25 30 35 40 45+

Total Length (cm)

Percent

Eureka – 794 total 

Gail – 220 total 

A B

C D

Figure 6

Figure 6. Size frequencies of all species, bocaccio, squarespot and widow rockfishes, observed at the midwater crossbeams of plat 

forms Gail and Eureka, 2005-2008. Vertical arrows denote length at 50% maturity (from Love et al. 2002). 
81

All Species

0

35

30

25

20

15

10

5

Depth (m)

Average Total Length (cm)

A

0 50 100 150 200

Eureka

Gail

Bocaccio

Average Total Length (cm)

0

40

30

35

25

20

15

10

5

B

0 50 100 150 200

Depth (m)

Eureka

Gail

Squarespot Rockfish

Average Total Length (cm)

0

18

16

14

12

10

8

6

4

2

Depth (m)

C

0 50 100 150 200

Eureka

Gail

Widow Rockfish

Depth (m)

Average Total Length (cm)

D

0

40

30

35

25

20

15

10

5

0 50 100 150 200

Eureka

Gail

Figure 7

Figure 7. The relationships between depth and average length for all species, and for bocaccio, squarespot and widow rockfishes, 

platforms Gail and Eureka, 2005-2008.

by. Unless hidden in complex substrate, fishes as small as about 5 cm in length are readily visible within two 

meters of the submersible. 

Data analyses

We used a root-root (x0.25) transformation of species densities before performing ANOVAS. Anderson 

and Yoklavich (2007) worked with similar data and found that the root-root transformation normalized 

species densities. We used the aov procedure of the statistical package R version 2.8.1 (R-Development Core 

Team, 2008) to perform balanced factorial ANOVAs of the transformed data for the most common 10 taxa 

(defined as those with highest combined densities) in two groups of three years (2005, 2007, 2008 and 2005, 

2006, 2007). We used two groups of years because we did not sample each crossbeam in each year. Thus, in 

some instances, a crossbeam was surveyed at one platform but its comparable beam was not surveyed in the 

other. ANOVAs were conducted on data from those crossbeams surveyed at both platforms in the same year. 

We used platform, depth, and year as factors. We assumed that the three-way interaction was non-significant 
82

and used it as the error term. Four depths were sampled at each platform during each year of a year group 

resulting in 24 observations. There was some overlap in the two sets of ANOVAs as two depths, two years, 

and seven species were held in common. Of the 240 observations used in one group of ANOVAs, 56 were 

also used in the other group. 

Results

We observed 13,609 fishes of at least 32 species at Platform Eureka and 2,980 fishes of at least 20 species at Platform Gail (Tables 2, 3). Total average fish density was much higher at Eureka (135.9 individuals 

per 100 m2) than at Gail (28.7 individuals per 100 m2). Rockfishes (genus Sebastes) dominated both assemblages, comprising 99.5% and 96.7% of all fishes observed at Eureka and Gail, respectively. A minimum of 

28 rockfish species (28 species at Eureka and 14 at Gail) inhabited the platform midwaters. Those species 

with highest densities at Eureka included squarespot, widow, speckled, and blue rockfishes, while squarespot 

and widow rockfishes and bocaccio dominated the midwaters of Gail (Table 3). Fifteen species were unique 

to Eureka and four species were found only at Gail. Of the species shared by the two structures, the densities of almost all species were higher at Eureka, sometimes by a factor of 10 or more. The number of species 

around the crossbeams varied with depth (ranging from 6-11 at Gail, and 14-18 at Eureka) and tended to be 

highest around the deeper members (Figure 4). Between the two platforms, species numbers were higher at 

all depths at Eureka and usually 2-3 times that of Gail. 

For a majority of the common species, there was a significant difference in densities both between platforms and among depth (Table 4). There were insignificant year effects for almost all of the tests, no significant platform-year and depth-year interactions, but the platform-depth interaction often was significant in 

the first group of tests (Table 4). At both platforms, and with only once exception, fish densities were highest 

in shallow waters and progressively declined with depth (Figure 5). Fish densities were much higher at all of 

the crossbeams at Platform Eureka compared to those at Gail as even the lowest density at Eureka (in 190 

m) was almost equal to the highest observed at Gail (in 70 m). Very few fish of any species were observed 

around Gail’s deepest three crossbeams (Figure 5). 

Most of the fishes that we observed were small, usually 20 cm TL or less long and only one fish larger 

than 30 cm was observed around Gail (Figure 6a) compared to several hundred fish, ranging to over 45 cm, 

at Eureka. Similarly, very few adult fishes lived around Gail. As an example, Gail harbored almost no adults 

of the three species that were relatively abundant at both platforms (e.g., bocaccio, squarespot, and widow 

rockfishes) (Figure 6b–d). Substantial numbers of mature individuals of all of these species were present at 

Eureka (Figure 6b–d). Most of the fish at Gail were young-of-the-year (YOY) rockfishes, primarily bocaccio, 

squarespot, and widow rockfishes (Figure 6b–d). YOY rockfishes were also a major part of Eureka’s fish assemblage, but comprised somewhat less of the total individuals observed. 

Fish sizes tended to increase with depth (Figure 7a). The average size of fish was similar between the 

platforms until a depth of about 150 m, when fish size increased abruptly at Eureka. Of the three most abundant species, bocaccio was similar sized throughout most of the depths, although fish in 200 m were much 

larger at Eureka (Figure 7b). Both squarespot and widow rockfishes generally were larger at each depth at 

Eureka (Figure 7c, d). 

Discussion

There is a substantial body of research clearly demonstrating that at relatively local scales reef fish assemblages are structured by such habitat characteristics as bottom depth, relief, and sea floor composition 

(Lecchini and Tsuchiya 2008; Anderson and Yoklavich 2007). Among deeper-water Pacific Coast reefs, many 

species differentially associate either with high relief, such as boulders (e.g., squarespot and rosy rockfishes), 

or low relief, which is often a mixture of cobble and mud (e.g., halfbanded and greenstriped rockfishes) 
83

(Anderson and Yoklavich 2007; Love et al. 2009). At an even finer scale, within high relief the presence of 

caves, crevices, and other reef complexity also has a significant effect on species composition (Caselle et al. 

2002; Love and York 2006; Love et al. 2006a). Indeed, there are a number of rockfish species, such as bocaccio, pinkrose, and copper rockfishes that, although not limited to complex habitat, are far more abundant 

there (Love and York 2006; Love et al. 2006a). In addition, habitat requirements may change as fish mature. 

For instance, newly recruited young-of-the-year cowcod (Sebastes levis) live primarily among cobbles and 

proceed to move into complex, high relief as they mature (Love and Yoklavich 2008). 

At both platforms, the characteristic fish species we observed in the midwaters are those whose primary habitat is hard substrate reefs. More specifically, in most instances these species are those taxa oriented to 

complex, high relief habitats. These species include blue, speckled, copper, pinkrose, and rosy rockfishes, and 

bocaccio (Anderson and Yoklavich 2007; Love et al. 2009). Conspicuously rare or absent from the midwaters 

of either platform, and from the midwaters of any California platform, are such species as greenstriped, halfbanded, and stripetail rockfishes (Love et al. 2000; Love et al. 2003; Nishimoto et al. 2008), all of which live 

along mud-rock interfaces and inhabit comparable depths, are abundant in the southern California Bight, 

and are found on the shell mounds surrounding some platforms (Love et al. 2000; Love et al. 2009). 

 We observed major differences between the midwater fish assemblages at platforms Gail and Eureka. 

Specifically, Platform Eureka exhibited: 1) higher overall fish densities and higher densities of most of the 

species held in common; 2) the presence of larger individuals of a number of species; 3) greater species 

richness, reflecting an assemblage containing more taxa typical of high-relief reefs. Off California, both 

species density and species richness are higher around high-relief reefs than over low relief rocks or on soft 

substrates (Yoklavich et al. 2002; Love et al. 2009). Thus, in all of these respects, compared to Gail the midwater fish assemblage of Platform Eureka more closely resembles the high relief natural reefs of the Southern 

California Bight. 

There were a few similarities in midwater species assemblage patterns. For instance, at both platforms, 

overall species densities declined with depth. This was also observed on natural reefs in the southern California Bight, where overall fish densities peaked at depths of about 100 m (Love et al. 2009). On natural 

reefs, changes in fish densities primarily reflect the depths at which most rockfishes recruit and this, in turn, 

reflects the availability of zooplankton prey. The general tendency among many species to be larger with 

depth reflects both a decrease in the abundances of young fishes and a gradual movement of juvenile fishes 

into deeper waters as they mature (Love et al. 2009). 

What is the source of the fishes we observed at the two platforms? It is likely that the vast majority of 

fishes living in platform midwaters recruit from the plankton as pelagic juveniles. During both this and a 

number of scuba-based studies we have observed YOYs of many species (e.g., blue, copper, flag, squarespot, 

and widow rockfishes, bocaccio, and painted greenling) recruiting to platform midwaters. Many of these 

species also recruit from the plankton to relatively shallow-water natural reefs (Love et al. 2002) and it would 

be expected that they would react similarly to shallow portions of platforms. A relatively small number of 

fishes might also have recruited to the platform bottom and swum up the jacket into the midwaters. However, few species recruit to the relatively deep waters at the bottoms of Eureka and Gail, although it is possible 

that some individuals of such deeper-water taxa as greenblotched, bank, and pinkrose rockfishes could have 

recruited there and moved into shallower waters along the skirt pilings and vertical sleeves (Love et al. 2009). 

Regardless of their shape, dimensions, and location, the midwaters of almost all California oil and 

gas platforms will, depending on variable annual oceanographic conditions, harbor very high densities of 

YOY rockfishes (Love et al. 2003; Love et al. 2006b; Nishimoto et al. 2008). Why then are YOYs sometimes 

present in extremely high densities in these habitats with little shelter? First, the YOYs of some species, such 

as gopher, copper, and black-and-yellow rockfishes, will hide amongst mussels and anemones. On natural 

reefs, these species often hide in the kelp or other algae (Love et al. 2002). YOYs of such species as blue and 
84

olive rockfishes and bocaccio form large schools and, at least when small, depend on these for protection, 

rather than on hiding in crevices. It appears that, as all of these species grow, the need for discrete sheltering 

sites increases, a need that cannot be filled in the midwaters of Gail and most platforms. Two species, grass 

and kelp rockfishes, are exceptions to this pattern. Both species recruit as YOYs to the midwaters of platforms and, often lying on or orienting to jacket members, will remain at the crossbeams through adulthood 

(Martin 2009). In contrast, the presence of large fishes of a number of species demonstrates that many of the 

fishes that recruit to the midwaters of Eureka remain there as they mature and become adults. 

Ultimately, the fishes living in the depths studied utilize the two structures in different ways. At Gail, 

the crossbeams function as a nursery ground for most species and young fishes remain in the midwaters for 

a few months to perhaps a year at which point a few species, such as bocaccio and probably flag rockfish, 

migrate down the jacket and take up residence at the bottom of the platform (Love et al. 2006b). Other species, such as widow rockfish, do not live at the bottom of Gail and thus must migrate away. In general, most 

of the species of rockfishes that recruit to California platforms as YOYs remain there for at most a few years. 

If the platform rests in relatively shallow waters, some of these species migrate to the sea floor and take up 

residence there. As an example, the bottom of Platform Irene, located in central California, harbors high 

densities of copper rockfish that recruit to the platform midwaters as YOYs. If a platform resides at a depth 

inappropriate for the adults of a species, they may move to natural reefs. For instance, young bocaccio tagged 

by the California Department of Fish and Game at platforms sited in about 60 m left after about one year and 

were recaptured years later on a number of natural reefs as much as 148 km away (Hartmann 1987). 

From a fish’s perspective, the crossbeams and vertical sleeves of most platforms appear to be rounded 

structures lacking substantial rugosity and sheltering sites. Because the thick invertebrate covering provides 

refuge for only the smallest of fishes, sheltering sites in the midwaters of a typical platform occur only 

where horizontal crossbeams meet vertical sleeves. We have long noted that, on a typical platform, these 

junctions are often the only places where somewhat larger rockfishes congregate. We should note that the 

high densities of fishes along Eureka’s crossbeams occur only in the narrow spaces formed between the skirt 

pilings and, in particular, in the vicinity of the bowl-shaped piling guides. Interestingly, the large schools of 

squarespot, speckled, and widow rockfishes do not form within the bowls, but rather behind them, where 

the guides meet the crossbeams. 

All platforms have finite economic lives and all will eventually be decommissioned. Decommissioned 

platforms can be totally or partially removed or left in place (Schroeder and Love 2004). One of the issues 

that will likely be addressed in the decommissioning process is the role that a platform plays as fish habitat. 

However, although there are substantial similarities among many platforms, the fish assemblages of California oil and gas platforms do not lend themselves to clean generalizations. It is clear that the shallowest waters 

of many platforms, to depths of about 30 m, harbor typical nearshore reef species, such as kelp bass, opaleye, garibaldi, painted greenling, sheephead, and YOY rockfishes. This is particularly true of the relatively 

nearshore platforms off Long Beach and those in the southeastern part of the Santa Barbara Channel (Love 

et al. 2003; Martin 2009). However, more northerly structures have fewer of these temperate reef species 

and in these midwaters only YOY rockfishes are usually abundant (Love et al. 2003). Around most offshore 

platforms, in waters below 30 m and down to the sea floor, juvenile rockfishes dominate the midwater assemblage (with the exception of Platform Eureka, which is inhabited by high densities of both juvenile and 

adult fishes). By comparison, the sea floor-jacket bottom habitat assemblage off deeper water structures is 

comprised primarily of larger rockfishes and lingcod and the shell mounds surrounding each platform harbor 

juveniles of various taxa and a number dwarf rockfishes and other benthic species (Love et al. 2000; Love et 

al. 2003). In these two sea floor habitats, bottom depth drives the species assemblages. All of this complexity 

reinforces the need to evaluate every platform on a case-by-case basis (Schroeder and Love 2004).
85

Acknowledgments

We thank M. Edwards, S. Liles, D. M. Schroeder, M. Nishimoto, A. Scarborough, M. McCrea, and S. 

Clark for their support. Research was conducted aboard the submersible Delta, piloted by C. Ijames and J. 

Lilly, with assistance of the crew of the R/V Velero. 

Literature Cited

Anderson, T. J. and M. M. Yoklavich. 2007. Multiscale habitat associations of deepwater demersal fishes 

off central California. Fish. Bull. 105:168-179.

Caselle, J. E., M. S. Love, C. Fusaro, and D. Schroeder. 2002. Trash or habitat? Fish assemblages on 

offshore oilfield seafloor debris in the Santa Barbara Channel, California. 

ICES J. Mar. Sci. 59:S258-S25.

Ebeling, A. W., R. J. Larson, W. S. Alevizon, and R. N. Bray. 1980. Annual variability of reef-fish 

assemblages in kelp forest off Santa Barbara, California. Fish. Bull. 78:31-377.

Hartmann, A. R. 1987. Movement of scorpionfishes (Scorpaenidae: Sebastes and Scorpaena) in the 

Southern California Bight. Calif. Fish Game 73:68-79. 

Lecchini, D. and M. Tsuchiya. 2008. Spatial structure of coral reef fish communities at Kudaka 

Island (Ryuku Archipelago), Japan. Ichthyol. Res. 55:321-327.

Love, M. S. and M. Yoklavich. 2008. Habitat characteristics of juvenile cowcod, Sebastes levis 

(Scorpaenidae), in southern California. Env. Biol. Fish. 82:195-202. 

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 a 

man-made platforms and (by inference) at natural reefs. Fish. Bull. 104:542-549.

Love, M. S., J. E. Caselle, and L. Snook. 2000. Fish assemblages around seven oil platforms in the 

Santa Barbara Channel area. Fish. Bull. 98:96-117.

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

production platforms and natural outcrops on fishes in southern and central California; a 

synthesis of information. U. S. Dep. Int., U. S. Geol. Survey, Biol. Res. Div., Seattle, WA, 

OCS Study MMS 2003-032.

Love, M. S., M. Yoklavich, and D. M. Schroeder. 2009. Demersal fish assemblages in the Southern 

California Bight based on visual surveys in deep water. Env. Biol. Fish. 874:55-68.

Love, M. S., M. Yoklavich, and L. Thorsteinson. 2002. The rockfishes of the northeast Pacific. 

University of California Press, Berkeley, California. 405 p.

Love, M. S., D. M. Schroeder, B. Lenarz, and G. R. Cochrane. 2006a. Gimme shelter: the importance 

of crevices to some fish species inhabiting a deeper-water rocky outcrop in southern 

California. CalCOFI Rep. 47:119-126.

Love, M. S., D. M. Schroeder, W. Lenarz, A. MacCall, A. Scarborough Bull, and L. Thorsteinson. 

2006b. Potential use of offshore marine structures in rebuilding an overfished rockfish species, 

bocaccio (Sebastes paucispinis). Fish. Bull. 104:383-390.

Martin, C. 2009. Species composition and abundance of the fishes at offshore petroleum platforms 

on the San Pedro Shelf, southern California. Master Thesis, Calif. St. Univ., Long Beach.

Nishimoto, M. M., M. S. Love, L. Washburn, D. M. Schroeder, and B. M. Emery. 2008. 

Assessing the fate of juvenile rockfish at offshore petroleum platforms and natural reefs 

in the Santa Barbara Channel. MMS OCS Study 2007-008. Marine Science Institute, 

University of California, Santa Barbara, California. MMS Cooperative Agreement 

Number 1435-01-04-CA-34031.
86

R Development Core Team. 2008. R: A language and environment for statistical computing. R Foundation 

for Statistical Computing, Vienna. Available: http://www.cran.R-project.org/mirrors.html.

Schroeder, D. M. and M. S. Love. 2004. Ecological and political issues surrounding decommissioning 

of offshore oil facilities in the Southern California Bight. Ocean Coastal Manage. 47:21-48.

Stephens, J. S. Jr., P. A. Morris, K. Zerba, and M. Love. 1984. Factors affecting fish diversity on a 

temperate reef: the fish assemblage of Palos Verdes Point, 1974-1981. Env. Biol. Fish. 11:259-275. 

Yoklavich, M., G. Cailliet, R. N. Lea, H. G. Greene, R. Starr, J. de Marignac, and J. Field. 2002. 

Deepwater habitat and fish resources associated with the Big Creek Marine Ecological Reserve. 

CalCOFI Rep. 43:120-140.