ANALYSIS OF FISH POPULATIONS 

AT PLATFORMS 

OFF SUMMERLAND, CALIFORNIA

OCS Study

BOEM 2015-019

Pacific Outer Continental Shelf Region

ANALYSIS OF FISH POPULATIONS 

AT PLATFORMS 

OFF SUMMERLAND, CALIFORNIA

Authored by:

Milton S. Love

Mary M. Nishimoto

Scott Clark

Ann S. Bull

Submitted by:

Marine Science Institute

University of California

Santa Barbara, CA 93106

Prepared under:

BOEM Cooperative Agreement No. M12AC00004

The U.S. Department of the Interior

Bureau of Ocean Energy Management

Pacific OCS Region

Camarillo, CA, 93010

September 2015

OCS Study

BOEM 2015-019
Disclaimer

This report was prepared under a cooperative agreement between the Bureau of Ocean Energy Management 

and the University of California, Santa Barbara. The report has been technically reviewed by BOEM and it 

has been approved for publication. The opinions, findings, conclusions, or recommendations in this report 

are those of the authors, and do not necessarily reflect the views and policies of BOEM. Mention of trade 

names or commercial products does not constitute an endorsement or recommendation for use. 

Report Availability

To download a PDF of this report, go to the U.S. Department of the Interior, Bureau of Ocean Energy Management, Environmental Studies Program Information System (ESPIS) website and search on OCS Study 

BOEM 2015-019.

This report can also be downloaded at www.lovelab.id.ucsb.edu.

Citation

Love, M. S., M. M. Nishimoto, S. Clark, and A. S. Bull. 2015. Analysis of Fish Populations at Platforms off 

Summerland, California. U.S. Department of the Interior, Bureau of Ocean Energy Management, Pacific 

OCS Region, Camarillo, CA. OCS Study 2015-019. 60 p.
TABLE OF CONTENTS

Technical Summary i

Executive Summary vi

Analysis of Fish Populations at Platforms 

off Summerland, California 1
i

TECHNICAL SUMMARY

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

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

Contract Number: M12AC00004

Sponsoring OCS Region: Pacific

Applicable Planning Area: Southern California

Fiscal Years of Project Funding: 2012; 2013; 2014

Completion Date of the Report: September 2015

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

Cumulative Project Cost: $625,000

Project Manager: Milton Love

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

Address: Santa Barbara, CA 93106

Principal Investigator: Milton Love

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

Background and Objectives

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

rebuilding plans, as specified by the Magnuson-Stevens Fishery Conservation Act. The Pacific Fishery Man-
ii

agement Council and the State of California began to severely restrict targeted fishing for these species in 

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

for decommissioning California’s offshore oil platforms.

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

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

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

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

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

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

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

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

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

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

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

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

The primary goals of this research were:

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

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

Literature Cited

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

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

Sci. 111:15462–15467.

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

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

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

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

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

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

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

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

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

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

Cooperative Agreement no. M08AX12732.

Description

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

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

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

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

Significant Results

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

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

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

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

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

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

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

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

. A total of 5,193 fish (a minimum 

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

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

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

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

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

observed at Platform B and a low of 12 was seen at Hogan. On the other hand, the overall density of fishes at 
iv

various platform bottoms did not vary statistically with bottom depth because at most platforms overall fish 

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

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

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

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

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

calico rockfishes. 

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

. A total of 2,822 fishes, 

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

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

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

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

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

any platform was unique.

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

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

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

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

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

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

lingcod (particularly YOYs) and painted greenling. 

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

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

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

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

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

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

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

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

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

midwaters were small, 10 cm or less long. 

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

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

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

any California platforms, the implication is that bottom turbidity plays less of a role in structuring fish assemblages as do other habitat characteristics such as bottom depth.
v

Overall, the data from 2012–2013 found that: 

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

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

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

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

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

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

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

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

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

small fraction of the total fish population. 

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

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

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

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

Analysis of Fish Populations 

at Platforms 

off Summerland, California

EXECUTIVE SUMMARY

Information Needed

There are 27 oil and gas platforms in the waters off California, 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, manager must decide what to do with the structure, a process 

known as decommissioning. The BOEM defines decommissioning as the process of ending oil, gas, or sulfur 

requirements of the regulations. The BOEM works to ensure that wells are plugged to prevent pollution; that 

pipelines are decommissioned and sometimes removed to prevent seepage of hydrocarbons and to resolve 

conflicts with other uses of the OCS; and that all sites are cleared of obstructions to minimize use conflicts. 

The BOEM will conduct detailed environmental reviews of any proposed decommissioning projects to 

evaluate the impacts from platform removal on regional fish populations. Obviously, when a platform is 

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

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

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

physical habitat for fishes in an area that would otherwise be void of such associated fauna. In addition, 

recent research has shown that oil and gas platforms off the coast of California have the highest secondary 

fish production per unit area of seafloor of any marine habitat that has been studied. The majority of species 

found on California platforms are rockfishes but include many other groups of fishes including some not 

well represented on nearby natural reefs or in coastal kelp beds. 

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

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

extremely small populations remaining. Recent BOEM-funded studies have revealed that some of the platforms hold large numbers of both juvenile and reproductively mature rockfishes in numbers far greater than 

any natural reef that has been surveyed. The observed rockfish species include bocaccio and cowcod, both of 

which are species of concern, with bocaccio once considered for listing as threatened under the Endangered 

Species Act. Additionally, four more federally declared overfished species have been observed, sometimes 

in large numbers, at some platforms: canary, darkblotched, widow and yelloweye rockfishes. All of these 

species are subject to federal rebuilding plans, as specified by the Magnuson-Stevens Fishery Conservation 

Act. The Pacific Fishery Management Council and the State of California began to severely restrict targeted 

fishing for these species in 2002 and 2003 and created the Cowcod Conservation Area in southern California 

to protect that species. Since 2001, cowcod have been managed as a no-retention fishery in California. In 

addition, the State of California banned the spot prawn trawl fishery in order to eliminate all by-catch of 

bocaccio. Populations of rockfishes at platforms, and the platforms as habitat for specific life history stages 

(e.g., nursery habitat for juveniles), may prove to be vital for timely recovery of the regional rockfish populations and fisheries. However, yet unknown are the impacts of platform removal on regional populations of 

coastal organisms, particularly the economically important rockfish species, on the Pacific OCS. The assess-
vii

ment of the effects of platform activities and of the habitat created by the structure of platforms on marine 

populations greatly bears upon decommissioning issues, as questions about Essential Fish Habitat and the 

ecological role of Pacific OCS platforms are still unresolved.

Pacific OCS platforms reside in a variety of depths and oceanographic conditions and there are large differences in fish assemblages between platforms. Thus, this assemblage variability suggests that a case-by-case 

scenario is likely for decommissioning decisions. In order to analyze the environmental consequences of 

platform decommissioning on local or regional fish populations, it is essential to know the role that each 

platform plays as fish habitat. Data gaps concerning the fish assemblages exist at some of the oldest facilities, 

yet these facilities may be the first to be decommissioned. Knowledge of the potential importance of the local population at platforms to the depleted Pacific rockfish stocks is essential for fully evaluating the various 

options proposed for decommissioning California’s offshore oil platforms.

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

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

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

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

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

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

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

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

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

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

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

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

The primary goals of this research were:

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

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

Research Summary

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

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

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

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

We conducted 57 transects encompassing 34,389 m2

 of habitat. Over all platforms, we observed 108,303 

individual fish, comprising a minimum of 46 species. Rockfishes, of at least 22 species, were most characteristic of all of the assemblages; we observed 105,114 individual rockfishes and this represented 97.1% of all 
viii

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

observed. In particular, YOY rockfishes comprised most of the midwater fish assemblage (94.7% of all fishes 

observed) and about 20% of the bottom and shell mound assemblages (21.1% and 22.9%, respectively). Of 

the top ten species ranked by density, all were rockfishes and seven of these taxa were YOY stages. Of particular importance were squarespot, blue, shortbelly, widow, and halfbanded rockfishes, and bocaccio. Among 

non-rockfish species, lingcod, senorita, painted greenling, shortspine combfish, and blacksmith comprised 

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

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

. A total of 5,193 fish (a minimum 

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

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

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

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

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

observed at Platform B and a low of 12 was seen at Hogan. On the other hand, the overall density of fishes at 

various platform bottoms did not vary statistically with bottom depth because at most platforms overall fish 

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

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

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

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

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

calico rockfishes. 

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

. A total of 2,822 fishes, 

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

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

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

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

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

any platform was unique.

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

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

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

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

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

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

lingcod (particularly YOYs) and painted greenling. 

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

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

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

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

We observed between 27 (Platform B) and 14 (Platform Henry) species in the midwaters at the eight platforms. No pattern in species richness among the platforms was observed. Around most platforms, fish densities varied greatly between years and this variability was due to very large interannual differences in YOY 

recruitment of blue, shortbelly, squarespot, and widow rockfishes, bocaccio and blacksmith. Midwater fish 

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

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

midwaters were small, 10 cm or less long. 

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

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

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

any California platforms, the implication is that bottom turbidity plays less of a role in structuring fish assemblages as do other habitat characteristics such as bottom depth.

Conclusions

Overall, the data from 2012–2013 found that: 

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

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

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

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

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

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

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

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

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

small fraction of the total fish population. 

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

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

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

linked and thus fish densities at all depths and habitats may vary greatly interannually.
x
1

ANALYSIS OF FISH POPULATIONS 

AT PLATFORMS 

OFF SUMMERLAND, CALIFORNIA

Abstract

Using a remotely operated vehicle, surveys were conducted in 2012–2013, around eight platforms off 

Summerland, California. We conducted 57 transects encompassing 34,389 m2

 of habitat. Over all platforms, 

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

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

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

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

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

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

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

. A total of 5,193 fish (a minimum of 34 species) were observed. Rockfishes, of a minimum of 19 species and totaling 4,359 individuals (83.9% of all fishes observed) dominated the assemblages. About 25% of all fishes observed were YOY 

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

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

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

26 was observed at Platform B and a low of 12 was seen at Hogan. On the other hand, the overall density of 

fishes at various platform bottoms did not vary statistically with bottom depth because at most platforms 

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

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

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

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

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

halfbanded and calico rockfishes. 

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

. A total of 2,822 

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

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

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

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

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

The shell mound around Platform B was the most species rich (22 taxa) and that around Habitat (11 

species), Henry (11 species), and Hogan (10 species) harbored the fewest taxa. Similar to our observation 

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

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

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

(of 20 cm or less) were by far most abundant in this habitat at all platforms. Species that characterized this 
2

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

lingcod (particularly YOYs) and painted greenling. 

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

fishes, 98,587 (98.3% of the total) were rockfishes (of 17 species), and 96.4% of these were YOYs. YOY rockfishes dominated this habitat and comprised 94.7% of all fishes observed. Densities of five rockfish species 

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

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

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

densities varied greatly between years and this variability was due to very large interannual differences in 

YOY recruitment of blue, shortbelly, squarespot, and widow rockfishes, bocaccio and blacksmith. Midwater 

fish assemblages around these eight platforms were fairly similar – perhaps the greatest differences were 

within-platform interannual ones driven by this recruitment variability. The overwhelming importance of 

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

midwaters were small, 10 cm or less long. 

We compared the bottom and shell mound assemblages of the Summerland platforms with previous 

findings from Platforms Holly and Gilda; these structures are located within the Santa Barbara Channel and 

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

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

of any California platforms, the implication is that bottom turbidity plays less of a role in structuring fish 

assemblages as do other habitat characteristics such as bottom depth.

Overall, the data from 2012–2013 found that: 

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

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

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

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

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

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

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

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

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

small fraction of the total fish population. 

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

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

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

linked and thus fish densities at all depths and habitats may vary greatly interannually.
3

Introduction

The BOEM defines decommissioning as the process of ending oil, gas, or sulfur requirements of the 

regulations. The BOEM works to ensure that wells are plugged to prevent pollution; that pipelines are decommissioned and sometimes removed to prevent seepage of hydrocarbons and to resolve conflicts with 

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

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

from platform removal on regional fish populations. Obviously, when a platform is disassembled, habitat is 

removed, and numerous fishes and invertebrates are killed.

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

which is focused on the potential importance of fish populations residing at these facilities. These platforms 

contribute considerable hard structure habitat for marine fishes; providing both a food source and complex 

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

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

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

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

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

of the Department of Commerce’s 2000 declaration designating the West Coast groundfish fishery a disaster with extremely small populations remaining. Recent BOEM-funded studies (Love et al. 2005, Love and 

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The assessment of the effects of platform activities and of the habitat created by the structure of platforms on marine populations greatly bears upon decommissioning issues, as questions about Essential Fish 

Habitat and the ecological role of Pacific OCS platforms are still unresolved.

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

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

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

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

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

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

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

for decommissioning California’s offshore oil platforms.
4

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

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

some of the first to be in line for decommissioning (Figure 1). Problematically, these structures are situated 

in a depositional, and hence turbid-water, region. In practice, this has meant that, despite a number of attempts over 15 years, water visibility at the bottom of the platform jackets has been judged by the pilots of 

manned submersibles too poor to safely allow assessment of fish assemblages. However, a review of segments 

of a remotely operated vehicle (ROV) survey of one of these platforms, indicated that fish populations at 

these platform habitats could be adequately surveyed using a combination of SCUBA and ROV techniques. 

The goal of this research was to provide those responsible for making decommissioning decisions with a 

much more detailed assessment of the fish assemblages of these eight platforms (and by extension a more 

accurate picture of their ecological importance) than is currently available. Information is needed as soon as 

possible for the use by the State of California to consider for decommissioning options under the California 

legislation AB 2503 (the California Marine Resources Legacy Act). The Act requires California to consider 

reefing OCS oil and gas platforms, if their ecological value warrants, before decommissioning and potential removal. This study will also extend the application of the methodology to develop results applicable 

Pt. Conception

Pt. Arguello

Santa

Barbara

Ventura

San Miguel

Island

Santa Rosa

Island Santa Cruz

Island

Anacapa

Island

Avila Beach

Long Beach Palos

Verdes

BA Henry

Houchin

Habitat

Hogan Hillhouse

C

Santa Barbara Channel

C A L I F O R N I A

Area

Detailed

Area

Detailed

N

Figure 1. Locations of all oil and gas platforms off California. Study platforms off Summerland, California, are darkened and named.
5

specifically for BOEM management decisions so that BOEM can specify requirements to industry or other 

interested parties when decommissioning occurs. Using the results, BOEM can ensure that specified criteria 

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

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

Program law AB 2503 (the California Marine Resources Legacy Act). Thus, the overarching purpose of this 

research is to provide those responsible for making decommissioning decisions with a much more detailed 

assessment of the fish assemblages of these eight platforms (and by extension a more accurate picture of their 

ecological importance) than is currently available.

Methods

The eight platforms were surveyed using two techniques: 1) by divers using scuba in the more shallow 

areas and 2) with an ROV around the deeper midwaters, platform bottoms, and shell mounds.

ROV Surveys

We conducted fish assemblage surveys around the deeper midwaters, bottom, and surrounding shell 

mounds of each platform (see Figure 2 for a schematic of a typical platform and Table 1 for bottom depths 

of platforms) using an ROV leased from Haaland Diving Incorporated of Santa Barbara and 

launched from the M/V Danny C. The Danny C

is a vessel commonly used by platform operators as a stage for ROV structural inspections 

and other tasks and has been used by BOEM 

in past studies. These surveys were conducted 

during November of 2012 and 2013 (Table 

2). As with our previous manned submersible 

work, but in this case using an ROV, each platform was circled first on the shell mound away 

from the jacket and then at the bottom of the 

jacket. As the ROV moved forwards, belt transects were conducted using a high-definition 

video camera that was oriented to look sideways off the starboard side. Parenthetically, we 

note that this is identical to the methodology 

used in previous manned submersible surveys. 

We conducted belt transects (2 m width) about 

2 m from the substrata, while the ROV maintained a speed of about 0.5 knots. ROV surveys 

were conducted during daylight hours between 

one hour after sunrise and one hour before sunset. Again, this is identical to other surveys we 

have conducted around platforms off southern 

California and thus any effect due to daylight or 

season on the species, population, or numbers 

of fish present during surveying is consistent 

over time. During all transects we identified (to 

lowest possible taxon), counted, and estimated 

the lengths of all fishes. Fish lengths were estiFigure 2. Platform diagram. The platform midwater habitat encompasses the hard substrate of the platform structure from the water 

surface to 2 m above the seafloor, whereas the platform base habitat 

is the bottom 2 m of the platform structure. The platform structure 

consists of outer vertical pilings and horizontal crossbeams (i.e., the 

platform jacket) and the vertical oil and gas conductors in the center. Note this is a general display diagram and the designs of these 

structures vary from platform to platform.
6

mated using a pair of parallel lasers (20 cm apart) mounted on either side of the external video camera. At 

least three researchers at a time observed the ROV surveys. All of the surveys were recorded and during each 

survey, one of the researchers voiced over the recording, identifying (with the help of the other researchers) 

the fishes observed. In the laboratory, transect data was transcribed into a MS Access database. 

Scuba Surveys

For the scuba surveys, we utilized the sampling design and protocols developed to assess platform fish 

populations in previous Minerals Management Survey-funded research (Love et al. 2003, Nishimoto et al. 

2008, Nishimoto and Love 2011). Platform surveys were conducted between June and September, once in 

2012 and twice in 2013 (Table 3). For each platform survey, scuba divers recorded observations while swimming rectangular belt transects that incorporated all four corner legs and the major horizontal crossbeams 

and portions underneath the platform jacket. The transects (2 m width x 2 m height) were conducted along the 

horizontal cross members at various depths from 6.1–39.0 m (Table 3). Scuba divers identified, counted, and 

estimated the sizes of all fishes observed with the aid of a ruler on the data recording slate. Observers were trained 

to visually estimate the total length of fishes to the nearest centimeter. These surveys allowed us to estimate and 

compare the density (number of individuals per m2 surveyed) and size distribution of all fishes observed.

Data Analysis

Platform Bottoms and Shell Mounds – Varying proportions of platform base and shell mound habitats were surveyed by one or more dives each year. In some cases a segment of a platform-habitat was surveyed by more than one dive in a year. Dive densities (count/100m2) of each taxon were treated as observations and transformed to the fourth root to satisfy variance homogeneity assumptions for discriminant 

analyses. To be consistent, we used the same transformation for cluster analysis. Densities for each species 

were standardized to a mean of zero and standard deviation of one. We used the lda procedure of R 3.1.2 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. We also summarized the data 

using untransformed densities for each platform-habitat by year. Note that counts were not included in the 

summary tables because varying survey coverage of habitats precluded meaningful comparison of counts 

among platforms, habitats, and years. 

Platform Midwaters – Because previous research had demonstrated that the entirety of platform midwater fish assemblages formed a discrete entity (i.e., separate from platform bottoms and shell mounds) 

we chose to combine the results of the ROV and SCUBA surveys for characterizing midwater fish communities. However because, unlike the scuba surveys, the ROV surveys were not made on platform vertical 

Table 1. Bottom depths of platforms discussed in this report.

PLATFORM DEPTH (M)

A 59

B 60

C 63

Gilda 62

Habitat 88

Henry 55

Hillhouse 59

Hogan 47

Holly 64

Houchin 51
7

Table 2. Location, dates, and depths of ROV surveys of the midwaters, bottoms, and shell mounds of eight oil and gas platforms off 

Summerland, California, 2012–2013.

2012

PLATFORM DEPTH AT

PLATFORM DATE TRANSECT TYPE START OF TRANSECT (M)

A 11 November Bottom 59

A 11 November Shell Mound 59

A 13 November Bottom 59

A 13 November Midwater 46

B 11 November Bottom 60

B 11 November Shell Mound 60

B 11 November Midwater 56

B 11 November Midwater 47

C 10 November Bottom 63

C 10 November Shell Mound 60

C 10 November Midwater 60

C 10 November Midwater 46

C 11 November Bottom 61

C 12 November Shell Mound 61

C 12 November Midwater 57

C 12 November Midwater 45

Habitat 09 November Bottom 88

Habitat 09 November Shell Mound 88

Habitat 09 November Midwater 68

Habitat 09 November Midwater 46

Habitat 09 November Midwater 26

Habitat 13 November Bottom 90

Habitat 13 November Shell Mound 89

Habitat 13 November Midwater 66

Habitat 13 November Midwater 44

Henry 11 November Bottom 55

Henry 11 November Shell Mound 53

Henry 12 November Bottom 55

Henry 12 November Shell Mound 55

Henry 12 November Midwater 39

Hillhouse 11 November Bottom 59

Hillhouse 11 November Shell Mound 58

Hillhouse 11 November Midwater 41

Hillhouse 13 November Bottom 60

Hillhouse 13 November Shell Mound 59

Hillhouse 13 November Midwater 41

Hogan 12 November Bottom 47

Hogan 12 November Shell Mound 47

Hogan 12 November Midwater 35

Houchin 12 November Bottom 51

Houchin 12 November Shell Mound 51

Houchin 12 November Shell Mound 51

Houchin 12 November Midwater 38
8

Table 2. (Continued)

2013

PLATFORM DEPTH AT

PLATFORM DATE TRANSECT TYPE START OF TRANSECT (M)

A 09 November Bottom 56

A 09 November Shell Mound 57

A 09 November Midwater 56

A 09 November Midwater 44

B 10 November Bottom 58

B 10 November Shell Mound 58

B 10 November Midwater 56

B 10 November Midwater 44

C 09 November Bottom 59

C 09 November Shell Mound 59

C 09 November Midwater 56

C 09 November Midwater 44

C 09 November Bottom 59

C 09 November Shell Mound 59

C 09 November Midwater 55

C 09 November Midwater 44

Habitat 08 November Bottom 91

Habitat 08 November Shell Mound 95

Habitat 08 November Midwater 57

Habitat 08 November Midwater 45

Henry 10 November Bottom 53

Henry 10 November Shell Mound 53

Henry 10 November Midwater 46

Henry 10 November Midwater 38

Henry 11 November Bottom 52

Henry 11 November Shell Mound 52

Henry 11 November Midwater 37

Hillhouse 10 November Bottom 57

Hillhouse 10 November Shell Mound 59

Hillhouse 10 November Midwater 52

Hillhouse 10 November Midwater 41

Hillhouse 11 November Bottom 58

Hillhouse 11 November Shell Mound 57

Hillhouse 11 November Midwater 39

Hogan 11 November Bottom 45

Hogan 11 November Shell Mound 47

Hogan 11 November Midwater 35

Hogan 11 November Bottom 44

Hogan 11 November Shell Mound 45

Hogan 11 November Midwater 34

Houchin 11 November Bottom 48

Houchin 11 November Shell Mound 50

Houchin 11 November Midwater 37

Houchin 11 November Bottom 48

Houchin 11 November Shell Mound 47

Houchin 11 November Midwater 37
9

components, we did not include the vertical components of the scuba surveys. Midwater fish assemblages 

were analyzed in ways similar to those of platform bottoms and shell mounds with one exception; we did 

not conduct an inter-platform discriminant analysis. Our rationale for this was the following: Results of all 

mid-water surveys, regardless of depth or month, made at a platform were combined for each year - resulting in 16 observations. As there are 8 platforms and only 16 observations, only 8 taxa could be used for a 

discriminant analysis. There was not a meaningful way to choose taxa to include in a discriminant analysis, 

as many were counted in a majority of the surveys. Thus, we concluded that it would not be useful to conduct a discriminant analysis. 

Overall Midwater, Bottom and Shell Mound Comparison – For the discussion, we compared not only 

all of the Summerland study platforms, but also platforms Holly and Gilda, also located within the Santa 

Barbara Channel and in the same bottom depth range (Table 1). Unlike the limited observation and species 

issues we faced with the platform midwaters, because we had a number of years of observations around 

Holly and Gilda, we were able to conduct an overall discriminant analysis of the species assemblages of these 

and the Summerland structures (see Discussion).

Results

Overall Summary of Platform Fish Assemblages

During 2012 and 2013, we conducted 57 transects around eight platforms (Figure 1) encompassing 

34,389 m2 of habitat (Table 4). Over all platforms, we observed 108,303 individual fish, comprising a minimum of 46 species (Tables 4–6). Rockfishes, of at least 22 species, were most characteristic of all of the 

assemblages; we observed 105,114 individual rockfishes and this represented 97.1% of all fishes recorded. 

Rockfishes comprised between 76.8% (shell mounds) and 98.3% (midwaters) of all fishes observed. In particular, YOY rockfishes comprised most of the midwater fish assemblage (94.7% of all fishes observed) and 

about 20% of the bottom and shell mound assemblages (21.1% and 22.9%, respectively). Of the top ten 

species ranked by density (Table 6), all were rockfishes and seven of these taxa were YOY stages. Of particular importance were squarespot, blue, shortbelly, widow, and halfbanded rockfishes, and bocaccio. Among 

non-rockfish species, lingcod, senorita, painted greenling, shortspine combfish, and blacksmith comprised 

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

Platform Bottoms

Around platform bottoms, we conducted 29 transects, covering 4,792 m2 (Table 4). A total of 5,193 

fish (a minimum of 34 species) were observed (Table 4). Rockfishes, of a minimum of 19 species and totaling 4,359 individuals (83.9% of all fishes observed) dominated the assemblages. About 25% of all fishes 

observed were YOY rockfishes (1,098 of 4,359) (Table 4). The bottom fish assemblages were fairly similar 

Table 3. Location, dates, and depths of scuba surveys of the midwaters of eight oil and gas platforms off Summerland, California, 

2012–2013.

PLATFORM 2012 2013 DEPTHS (M)

A 26 June 6 June, 21 August 7.9, 19.5, 31.7

B 7 July 6 June, 21 August 9.1, 18.3, 31.1

C 27 July, 8 August 18 June, 21 August 7.0, 18.9, 30.5

Habitat 11 July, 27 July 2 July, 29 August 9.1, 24.1, 30.5

Henry 21 June 21 June, 4 September 7.9, 20.7, 36.0

Hillhouse 29 June 27 June, 13 September 6.1, 22.6, 39.0

Hogan 14 June, 18 June 18 June, 29 August 7.6, 20.4, 33.5

Houchin 12 June 2 July, 6 September 10.0, 23.2, 36.6
10

Table 4. A summary of the number of transects, areas surveyed (m2), numbers of fishes, numbers of rockfishes, and number of rockfish YOY from eight platforms, based on scuba and ROV surveys, 2012–2013. YOY = young-of-the-year. Scientific names are listed in 

Table 3.

 BOTTOM SHELL MOUND MIDWATER TOTAL

Number of transects 29 28 16 57

Area surveyed (m2) 4,792 4,433 20,432 34,389

Number of fishes counted 5,193 2,822 100,287 108,303

Number of rockfishes counted 4,359 2,168 98,587 105,114 

All rockfishes % of all fishes 83.9 76.8 98.3 97.1

Number of rockfish YOY 1,098 646 95,020 96,764

All rockfish YOY % of all rockfishes 25.2 29.8 96.4 92.1

All rockfish YOY % of all fishes 21.1 22.9 94.7 89.3

Minimum number of species 34 32 28 46

Minimum number of rockfish species 19 16 17 22

Table 5. Common and scientific names of fishes observed by scuba or remotely operated vehicle around eight platforms in southern 

California, 2012–2013.

Black-and-yellow rockfish Sebastes chrysomelas

Blackeye goby Rhinogobiops nicholsii

Blacksmith Chromis punctipinnis

Bluebanded ronquil Rathbunella hypoplecta

Blue rockfish Sebastes mystinus

Bocaccio Sebastes paucispinis

Brown rockfish Sebastes auriculatus

Bull sculpin Enophrys taurina

Cabezon Scorpaenichthys

marmoratus

Calico rockfish Sebastes dallii

California lizardfish Synodus lucioceps

California halibut Paralichthys californicus

California sheephead Semicossyphus pulcher

Canary rockfish Sebastes pinniger

Chilipepper Sebastes goodei

Copper rockfish Sebastes caurinus

Cowcod Sebastes levis

Flag rockfish Sebastes rubrivinctus

Garibaldi Hypsypops rubicundus

Gopher rockfish Sebastes carnatus

Grass rockfish Sebastes rastrelliger

Greenspotted rockfish Sebastes chlorostictus

Jack mackerel Trachurus symmetricus

Halfbanded rockfish Sebastes semicinctus

Halfmoon Medialuna californiensis

Honeycomb rockfish Sebastes umbrosus

Kelp bass Paralabrax clathratus

Kelp greenling Hexagrammos decagrammus

Kelp rockfish Sebastes atrovirens

Lingcod Ophiodon elongatus

Longspine combfish Zaniolepis latipinnis

Ocean sunfish Mola mola

Olive rockfish Sebastes serranoides

Opaleye Girella nigricans

Pacific sardine Sardinops sagax

Rubberlip seaperch Rhacochilus toxotes

Pacific hake Merluccius productus

Painted greenling Oxylebius pictus

Pile perch Damalichthys vacca

Pink seaperch Zalembius rosaceus

Rosy rockfish Sebastes rosaceus

Rubberlip seaperch Rhacochilus toxotes

Senorita Oxyjulis californica

Sharpnose seaperch Phanerodon atripes

Shortbelly rockfish Sebastes jordani

Shortspine combfish Zaniolepis frenata

Spotted scorpionfish Scorpaena guttata

Squarespot rockfish Sebastes hopkinsi

Starry flounder Platichthys stellatus

Starry rockfish Sebastes constellatus

Stripefin ronquil Sebastes alleni

Treefish Sebastes serriceps

Unidentified flatfishes Families Paralicthyidae and 

Pleuronectidae

Unidentified rockfishes1 Sebastes spp.

Unidentified ronquil Family Bathymasteridae

Unidentified sanddab Citharichthys spp.

Unidentified sculpin Family Cottidae

Unidentified surfperch Family Embiotocidae

Vermilion rockfish Likely a combination of 

vermilion rockfish, 

S. miniatus, and sunset 

rockfish, S. crocotulus

White seaperch Phanerodon furcatus

Widow rockfish Sebastes entomelas

Wolf-eel Anarrhichthys ocellatus

Yelloweye rockfish Sebastes ruberrimus

Yellowtail rockfish Sebastes flavidus

1

These were primarily unidentified YOY rockfishes and, particularly in the platform midwaters, were members of the “KGB” 

group, composed of black-and-yellow, copper, gopher, and kelp 

rockfishes.
11

across all platforms and most different at the deepest (Habitat) and shallowest (Hogan) structures (Figures 

3–5, Table 7). 

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

26 was observed at Platform B and a low of 12 was seen at Hogan (Table 7, Figure 6). On the other hand, the 

overall density of fishes at various platform bottoms did not vary statistically with bottom depth (Figure 2) 

because at most platforms overall fish density varied greatly between years (Table 7). This was due primarily 

to substantial interannual differences in densities linked to quite variable recruitment of YOY squarespot, 

shortbelly, halfbanded, and calico rockfishes and California lizardfish, as well as changes in densities of 

somewhat older juvenile squarespot, vermilion, and blue rockfishes and bocaccio. Most of the fishes we observed around platform bottoms were relatively small, about 70% were 15 cm or less (Figure 7). These fishes 

Table 6. A summary of the average densities (fish per 100 m2) of each species observed around eight platforms, based on scuba and 

ROV surveys, 2012–2013. YOY = young-of-the-year. Scientific names are listed in Table 3.

SPECIES AVERAGE DENSITY SPECIES AVERAGE DENSITY

Squarespot rockfish YOY 38.7

Blue rockfish YOY 34.6

Shortbelly rockfish YOY 28.4

Widow rockfish YOY 18.0

Unidentified rockfishes YOY 15.3

Halfbanded rockfish 13.2

Bocaccio YOY 11.2

Squarespot rockfish 6.3

Calico rockfish 6.3

Halfbanded rockfish YOY 5.5

Vermilion rockfish 4.9

Calico rockfish YOY 3.9

Lingcod YOY 2.5

Senorita 2.3

Painted greenling 2.3

Unidentified rockfishes 2.2

Bocaccio 2.0

Blue rockfish 1.9

Copper rockfish 1.5

Olive rockfish 1.4

Shortspine combfish 1.4

Unidentified sanddab 1.0

Blacksmith YOY 1.0

Brown rockfish 0.8

Pile perch 0.7

Lingcod 0.7

Widow rockfish 0.5

Unidentified fishes 0.5

Kelp rockfish 0.5

Unidentified flatfishes 0.4

Unidentified surfperch 0.4

California lizardfish 0.3

Blacksmith 0.3

Kelp greenling 0.3

Painted greenling YOY 0.2

Sharpnosed seaperch 0.2

Sebastomus spp. 0.2

Copper rockfish YOY 0.2

Yellowtail rockfish 0.2

Vermilion rockfish YOY 0.1

Gopher rockfish 0.1

California sheephead 0.1

Kelp bass 0.1

Blackeye goby 0.1

Flag rockfish 0.1

Gopher rockfish YOY 0.1

White seaperch 0.1

Cabezon >0.1

Chilipepper >0.1

Rosy rockfish >0.1

Unidentified combfishes >0.1

Rubberlip seaperch >0.1

Longspine combfish >0.1

Treefish >0.1

Unidentified ronquil >0.1

Wolf-eel >0.1

Greenspotted rockfish >0.1

Unidentified sculpin >0.1

Shortbelly rockfish >0.1

Grass rockfish >0.1

Spotted scorpionfish >0.1

Olive rockfish YOY >0.1

Brown rockfish YOY >0.1

Yellowtail rockfish YOY >0.1

Pink seaperch >0.1

Pacific sanddab >0.1

Canary rockfish >0.1

Garibaldi >0.1

Black-and-yellow rockfish >0.1

Total 213.3

Minimum Number of Species 46

Total Rockfish YOY 156.0

Total Rockfish 198.3

% Rockfish YOY 73.2

% Rockfish 93.0
12

A

B 

C 

Habitat

Henry

Hillhouse

Hogan

Houchin

Platform Bottoms

 Canonical Discriminant Analysis

Standardized Transformed Densities

Discriminant 2 (8%) 

Discriminant 1 (79%) 

-50 -40 -30 -20 -10 0 10 20 30 40

2

0

-2

-4

-6

-8

4

6

8

10

12

Figure 3. A canonical discriminant analysis of fish assemblages around the bottoms of eight platforms off Summerland, California, 

based on centroids of surveys conducted in 2012–2013.

Base of All Platforms Average Standardized Transformed Densities

A, B, C Habitat Hogan Rest

Cluster 1

Cluster 2

-10

-8

-6

-4

-2

0

2

4

6

8

10

Platform

Average Density

Figure 4. A comparison of densities of two bottom species clusters (Cluster 1 = gopher rockfish to squarespot rockfish; Cluster 2 = 

flag rockfish to painted greenling) from eight Summerland, California, shown in Figure 5. Note that we do not include the California 

lizardfish in a cluster as it is composed of one species.
13

60 m – C

60 m – B

59 m – A

58 m – Hillhouse

53 m – Henry

51 m – Houchen

88 m – Habitat

47 m – Hogan

60 m – C

60 m – B

59 m – A

58 m – Hillhouse

53 m – Henry

51 m – Houchen

88 m – Habitat

47 m – Hogan

40

36

32

48

44

28

24

20

16

12

8

4

200

800

180

500

160

140

120

100

80

60

40

20

Density of All Species Combined at Platform Bottom

 Ordered by Platform Bottom Depth

Number of Species

Density (Fishes per 100m2

)

Number of Species at Platform Bottom

Ordered by Platform Bottom Depth

Figure 5. A cluster analysis of the characteristics species of platform bottoms, Summerland, California, 2012–2013. 60 m – C 60 m – B 59 m – A 58 m – Hillhouse 53 m – Henry 51 m – Houchen 88 m – Habitat 47 m – Hogan 60 m – C 60 m – B 59 m – A 58 m – Hillhouse 53 m – Henry 51 m – Houchen 88 m – Habitat

47 m – Hogan

40

36

32

48

44

28

24

20

16

12

8

4

200

800

180

500

160

140

120

100

80

60

40

20

Density of All Species Combined at Platform Bottom

 Ordered by Platform Bottom Depth

Number of Species

Density (Fishes per 100m2

)

Number of Species at Platform Bottom

Ordered by Platform Bottom Depth

Figure 6. Number of species and density of all species observed at the bottoms of eight platforms off Summerland, California, 

2012–2013. Platforms are listed from shallowest to deepest.
14

0

0.001

0.01

0.1

1

10

10

20

30

40

50

60

70

80

90

5 10 15 20 25 30 35 40 45 50 >50

Length Frequencies of All Fishes Observed

Length Frequencies of All Fishes Observed

25 cm and longer

Percent

Percent

Length (cm)

25 30 35 40 45 50 >50

Length (cm)

Bottom

Midwater

Shell mound

Bottom

Midwater

Shell mound

Figure 7. A length-frequency histogram of all fishes observed at platform bottoms, shell mounds, and midwaters around eight platforms off Summerland, California, 2012–2013.
15

Table 7. Densities of all fishes observed from a remotely operated vehicle around the bottom of eight platforms in the Santa Barbara 

Channel. Platforms are ordered from westernmost (C) to easternmost (Hogan) with the exception of the more offshore Platform 

Habitat (listed first). Platform bottom depth is listed after platform name. YOY = young-of-the-year. Density is in fish per 100 m2

. 

Scientific names are listed in Table 4. Note that counts of fishes are not included in this table because varying survey coverage of this 

precluded meaningful comparison of counts among platforms, habitats, and years.

PLATFORM HABITAT (DEPTH = 88 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Halfbanded rockfish 105.0 125.8 115.4 10.4

Lingcod YOY 16.2 4.7 10.4 5.8

Copper rockfish 4.1 0.9 2.5 1.6

Sebastomus spp. 4.1 0.9 2.5 1.6

Painted greenling 1.8 2.5 2.1 0.3

Flag rockfish 1.5 0.9 1.2 0.3

Unidentified rockfishes 2.3 0.0 1.2 1.2

Calico rockfish 0.3 1.9 1.1 0.8

Lingcod 1.0 0.9 1.0 0.0

Vermilion rockfish 1.3 0.0 0.6 0.6

Unidentified flatfishes 0.0 1.2 0.6 0.6

Greenspotted rockfish 0.5 0.3 0.4 0.1

Unidentified fishes 0.8 1.2 0.4 0.4

Kelp greenling 0.5 0.0 0.3 0.3

Bocaccio 0.0 0.3 0.2 0.2

Cabezon 0.0 0.3 0.2 0.2

Brown rockfish YOY 0.3 0.0 0.1 0.1

Halfbanded rockfish YOY 0.3 0.0 0.1 0.1

Kelp rockfish 0.3 0.0 0.1 0.1

Painted greenling YOY 0.3 0.0 0.1 0.1

Rosy rockfish 0.3 0.0 0.1 0.1

Shortspine combfish 0.3 0.0 0.1 0.1

Unidentified ronquil 0.3 0.0 0.1 0.1

Total 141.3 140.7 141.2 0.3

Minimum number of species 16 10 17

Total rockfish YOY 0.5 0.0 0.3

Total rockfishes 120.2 131.1 125.6

Rockfish YOY %

 of all fishes surveyed 0.4 0.0 0.2

All rockfishes %

 of all fishes surveyed 85.1 93.1 89.1

PLATFORM C (DEPTH = 63 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Calico rockfish 34.7 18.5 26.6 8.1

Squarespot rockfish 4.5 16.1 10.3 5.8

Painted greenling 8.5 3.3 5.9 2.6

Olive rockfish 0.5 9.6 5.0 4.5

Unidentified rockfishes 1.9 7.8 4.8 2.9

Lingcod YOY 7.1 1.8 4.4 2.6

Widow rockfish YOY 0.0 7.2 3.6 3.6

Vermilion rockfish 3.8 3.3 3.5 0.2

Copper rockfish 3.1 2.7 2.9 0.2

Widow rockfish 0.0 4.5 2.2 2.2
16

Pile perch 3.8 0.9 2.1 1.2

Calico rockfish YOY 3.8 0.0 1.9 1.9

Unidentified fishes 1.2 1.8 1.5 0.3

Lingcod 0.9 1.5 1.4 0.4

Bocaccio 0.2 1.5 0.9 0.6

Gopher rockfish 0.2 1.5 0.9 0.6

Brown rockfish 0.7 0.9 0.8 0.1

Blue rockfish 0.5 0.9 0.7 0.2

Kelp greenling 0.7 0.6 0.7 0.1

Halfbanded rockfish 0.9 0.3 0.6 0.3

Copper rockfish YOY 0.7 0.0 0.4 0.4

Kelp rockfish 0.7 0.0 0.4 0.4

Sharpnose seaperch 0.7 0.0 0.4 0.4

Shortbelly rockfish 0.7 0.0 0.4 0.4

Unidentified rockfishes YOY 0.7 0.0 0.3 0.4

Treefish 0.2 0.3 0.3 0.0

Painted greenling YOY 0.5 0.0 0.2 0.2

Sebastomus spp. 0.5 0.0 0.2 0.2

Unidentified surfperch 0.5 0.0 0.2 0.2

Chilipepper 0.0 0.3 0.1 0.1

Olive rockfish YOY 0.0 0.3 0.1 0.1

Blackeye goby 0.2 0.0 0.1 0.1

Canary rockfish 0.2 0.0 0.1 0.1

Halfbanded rockfish YOY 0.2 0.0 0.1 0.1

Shortbelly rockfish YOY 0.2 0.0 0.1 0.1

Total 82.7 85.7 84.2 1.5

Minimum number of species 22 18 23

Total rockfish YOY 5.7 7.5 6.6

Total rockfishes 59.1 75.6 67.3

Rockfish YOY %

 of all fishes surveyed 6.9 8.7 7.8

All rockfishes % 

 of all fishes surveyed 71.4 88.2 79.9

PLATFORM B (DEPTH = 60 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Squarespot rockfish 125.4 4.2 64.8 60.6

Squarespot rockfish YOY 111.3 0.0 55.7 55.7

Shortspine combfish 65.5 0.0 32.7 32.7

Shortbelly rockfish YOY 40.9 0.0 20.5 20.5

Unidentified rockfishes YOY 18.3 0.7 9.5 8.8

Calico rockfish 12.1 6.1 9.1 3.0

Vermilion rockfish 6.9 9.6 8.3 1.4

Widow rockfish YOY 1.0 12.2 6.6 5.6

Olive rockfish 2.0 9.9 5.9 4.0

Halfbanded rockfish 8.5 0.0 4.3 4.3

Lingcod YOY 4.3 4.0 4.1 0.1

Painted greenling 6.2 1.6 3.9 2.3

Bocaccio 0.0 6.3 3.2 3.2

Table 7. (Continued)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013
17

Widow rockfish 0.7 5.4 3.0 2.4

Unidentified rockfishes 0.7 4.7 2.7 2.0

Copper rockfish 0.0 4.2 2.1 2.1

Halfbanded rockfish YOY 3.9 0.0 2.0 2.0

Pile perch 2.6 0.5 1.5 1.1

Blue rockfish 1.6 0.9 1.3 0.3

Unidentified fishes 1.3 0.9 1.1 0.2

Calico rockfish YOY 2.0 0.0 1.0 1.0

Yellowtail rockfish 0.0 1.9 0.9 0.9

Lingcod 0.3 1.4 0.9 0.5

Unidentified surfperch 1.6 0.0 0.8 0.8

Brown rockfish 0.7 0.9 0.8 0.1

Kelp rockfish 0.7 0.0 0.7 0.0

Kelp greenling 1.3 0.0 0.7 0.7

Gopher rockfish 0.7 0.5 0.6 0.1

Unidentified sanddab 0.0 0.9 0.5 0.5

Grass rockfish 0.7 0.0 0.3 0.3

Sharpnose seaperch 0.7 0.0 0.3 0.3

California lizardfish 0.0 0.5 0.2 0.2

Blackeye goby 0.3 0.0 0.2 0.2

Painted greenling YOY 0.3 0.0 0.2 0.2

Rosy rockfish 0.3 0.0 0.2 0.2

Rubberlip seaperch 0.3 0.0 0.2 0.2

Total 423.1 78.2 250.6 172.4

Minimum number of species 19 17 26

Total rockfish YOY 177.5 12.9 95.2

Total rockfishes 338.3 68.4 203.3

Rockfish YOY %

 of all fishes surveyed 42.0 16.5 38.0

All rockfish %

 of all fishes surveyed 80.0 87.4 81.1

PLATFORM A (DEPTH = 59 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Vermilion rockfish 103.7 11.1 57.4 46.3

Squarespot rockfish 4.5 25.6 15.1 10.5

Copper rockfish 17.5 9.4 13.4 4.0

Blue rockfish 25.4 0.9 13.1 12.3

Bocaccio 20.9 0.4 10.6 10.2

Calico rockfish 1.1 16.6 8.9 7.8

Brown rockfish 7.3 4.3 5.8 1.5

Calico rockfish YOY 6.2 0.0 3.1 3.1

Unidentified rockfishes 2.3 3.4 2.8 0.6

Squarespot rockfish YOY 5.1 0.4 2.2 2.3

Olive rockfish 3.4 1.3 2.3 1.1

Widow rockfish 2.3 2.1 2.2 0.1

Kelp rockfish 3.9 0.4 2.2 1.8

Unidentified surfperch 3.4 0.4 1.9 1.5

Painted greenling 1.1 1.7 1.4 0.3

Table 7. (Continued)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013
18

Halfbanded rockfish YOY 1.7 0.0 0.8 0.6

Pile Perch 1.7 0.4 1.1 0.6

Lingcod 0.0 1.7 0.9 0.9

Widow rockfish YOY 0.0 1.7 0.9 0.9

Painted greenling YOY 1.1 0.4 0.8 0.4

Sharpnose seaperch 1.1 0.0 0.6 0.6

Unidentified rockfish YOY 1.1 0.0 0.6 0.6

Kelp greenling 0.6 0.4 0.5 0.1

Lingcod YOY 0.6 0.4 0.5 0.1

Treefish 0.0 0.9 0.4 0.4

Gopher rockfish 0.6 0.0 0.3 0.3

Rubberlip seaperch 0.6 0.0 0.3 0.3

Unidentified fishes 0.0 0.4 0.2 0.2

Total 217.0 84.9 151.0 66.1

Minimum number of species 18 16 19

Total rockfish YOY 14.1 2.6 8.8

Total rockfishes 206.9 78.9 142.9

Rockfish YOY %

 of all fishes surveyed 6.5 3.0 5.5

All rockfishes %

 of all fishes surveyed 95.3 93.0 94.7

PLATFORM HILLHOUSE (DEPTH = 59 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Calico rockfish 37.1 13.4 25.2 11.8

Olive rockfish 7.9 7.5 7.7 0.2

Copper rockfish 12.1 0.3 6.2 5.9

Painted greenling 10.0 1.9 5.9 4.1

Unidentified rockfishes 10.3 6.6 8.4 1.4

Vermilion rockfish 5.6 1.2 3.1 1.9

Lingcod YOY 5.3 0.9 3.1 2.2

Halfbanded rockfish 0.3 5.6 3.0 2.7

Blue rockfish 4.4 0.0 2.2 2.2

Lingcod 1.2 2.2 1.7 0.5

Unidentified fishes 2.4 0.9 1.6 0.7

Calico rockfish YOY 2.4 0.0 1.2 1.2

Unidentified surfperch 2.4 0.0 1.2 1.2

Brown rockfish 1.8 0.0 0.9 0.9

Kelp rockfish 1.8 0.0 0.9 0.9

Pile perch 1.8 0.0 0.9 0.9

Squarespot rockfish 0.0 1.6 0.8 0.8

White seaperch 1.5 0.0 0.7 0.7

Unidentified sanddab 0.0 1.2 0.6 0.6

Kelp greenling 0.9 0.3 0.6 0.3

California lizardfish 0.0 0.6 0.3 0.3

Flag rockfish 0.0 0.6 0.3 0.3

Yellowtail rockfish 0.0 0.6 0.3 0.3

Unidentified flatfishes 0.0 0.3 0.2 0.2

Unidentified sculpin 0.0 0.3 0.2 0.2

Table 7. (Continued)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013
19

Halfbanded rockfish YOY 0.3 0.0 0.1 0.1

Rosy rockfish 0.3 0.0 0.1 0.1

Sebastomus spp. 0.3 0.0 0.1 0.1

Total 104.5 42.5 73.5 31.0

Minimum number of species 14 14 20

Total rockfish YOY 2.6 0.0 1.3

Total rockfishes 79.2 33.7 56.4

Rockfish YOY %

 of all fishes surveyed 2.5 0.0 1.8

All rockfishes % 

 of all fishes surveyed 75.8 79.4 76.8

PLATFORM HENRY (DEPTH = 55 M)

DENSITY STANDARD ERROR

SPECIES 2012 2013 2012–2013

Halfbanded rockfish YOY 35.8 0.0 17.9 17.9

Squarespot rockfish 2.4 23.1 12.8 10.4

Calico rockfish 18.9 6.3 12.6 6.3

Calico rockfish YOY 24.1 0.0 12.1 12.1

Unidentified rockfishes 2.0 9.8 5.9 3.9

Lingcod YOY 8.0 2.8 5.4 2.6

Halfbanded rockfish 8.4 0.0 4.2 4.2

Painted greenling 5.6 1.4 3.5 2.1

Olive rockfish 0.0 5.3 2.6 2.6

Unidentified rockfishes YOY 3.2 0.0 1.6 2.1

Widow rockfish 0.0 2.8 1.4 1.6

Lingcod 0.0 3.9 1.9 1.9

Unidentified rockfishes 3.2 0.0 1.6 1.6

Widow rockfish YOY 0.0 2.8 1.4 1.4

California lizardfish 0.0 2.1 1.1 1.1

Brown rockfish 0.8 0.0 0.4 0.4

Painted greenling YOY 0.4 0.4 0.4 0.0

Unidentified sanddab 0.0 0.7 0.4 0.4

Sebastomus spp. 0.4 0.0 0.2 0.2

Squarespot rockfish YOY 0.4 0.0 0.2 0.2

Unidentified ronquil 0.5 0.0 0.2 0.2

Vermilion rockfish 0.5 0.0 0.2 0.2

Wolf-eel 0.5 0.0 0.2 0.2

Unidentified fishes 0.0 0.4 0.2 0.2

Total 111.8 63.0 87.4 24.4

Minimum number of species 10 8 14

Total rockfish YOY 63.5 2.8 33.2

Total rockfishes 96.9 51.5 74.2

Rockfish YOY %

 of all fishes surveyed 56.8 4.4 37.9

All rockfishes %

 of all fishes surveyed 86.7 81.7 84.9

Table 7. (Continued)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013
20

PLATFORM HOUCHIN (DEPTH = 51 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Halfbanded rockfish YOY 84.5 0.0 42.2 42.2

Calico rockfish YOY 37.9 0.0 19.0 19.0

Calico rockfish 6.4 3.9 5.2 1.3

Painted greenling 5.7 2.5 4.1 1.6

Lingcod YOY 3.6 2.5 3.0 0.5

Yellowtail rockfish 0.0 3.3 1.7 1.7

Unidentified surfperch 2.9 0.0 1.4 1.4

Halfbanded rockfish 1.4 1.1 1.3 0.2

Pile perch 2.1 0.3 1.2 0.9

Unidentified fishes 0.7 0.6 0.6 0.1

California lizardfish 0.0 0.8 0.4 0.4

Blackeye goby 0.7 0.0 0.4 0.4

Kelp greenling 0.7 0.0 0.4 0.4

Lingcod 0.7 0.0 0.4 0.4

Olive rockfish 0.7 0.0 0.4 0.4

White seaperch 0.7 0.0 0.4 0.4

Copper rockfish 0.0 0.3 0.1 0.1

Squarespot rockfish 0.0 0.3 0.1 0.1

Unidentified combfish 0.0 0.3 0.1 0.1

Unidentified flatfish 0.0 0.3 0.1 0.1

Unidentified rockfishes 0.0 0.3 0.1 0.1

Unidentified sanddab 0.0 0.3 0.1 0.1

Widow rockfish YOY 0.0 0.3 0.1 0.1

Total 148.9 16.9 82.9 66.0

Minimum number of species 8 12 16

Total rockfish YOY 122.4 0.3 61.3

Total rockfishes 131.0 9.4 70.2

Rockfish YOY %

 of all fishes surveyed 82.2 1.6 74.0

All rockfishes %

 of all fishes surveyed 88.0 55.7 84.7

PLATFORM HOGAN (DEPTH = 47 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Calico rockfish YOY 37.0 0.3 18.6 18.4

Calico rockfish 16.8 0.9 8.8 7.9

Halfbanded rockfish YOY 9.8 0.0 4.9 4.9

Pile perch 3.5 0.3 1.9 1.6

Unidentified rockfishes YOY 2.1 0.3 1.2 0.9

Unidentified rockfishes 1.4 0.3 0.8 0.6

California lizardfish 0.0 1.5 0.7 0.7

Halfbanded rockfish 1.4 0.0 0.7 0.7

Unidentified fishes 1.4 0.0 0.7 0.7

Vermilion rockfish 0.0 0.9 0.4 0.4

Gopher rockfish 0.7 0.0 0.3 0.3

Olive rockfish 0.7 0.0 0.3 0.3

Squarespot rockfish 0.7 0.0 0.3 0.3

Lingcod YOY 0.0 0.6 0.3 0.3

Table 7. (Continued)
21

were either juvenile fishes (e.g., calico, copper, halfbanded, squarespot, and vermilion rockfishes, bocaccio, 

and lingcod) or were dwarf species such as halfbanded and calico rockfishes. 

Platform Shell Mounds

We conducted 28 transects on the shell mounds and these transects covered 4,433 m2 (Table 4). A total 

of 2,822 fishes, of at least 32 species, were observed (Tables 4, 8). As with the platform bottoms, rockfishes 

(2,168 individuals of at least 16 species) again dominated the species assemblage; they comprised 76.8% of 

all fishes observed. Almost 30% of all fishes observed were YOY rockfishes (646 of 2,168) (Table 4). While 

shell mound fish assemblages were similar across all platforms (Figure 8), we observed relatively small differences between the deeper platforms Habitat, A, and B, and the rest of the structures (Figures 9, 10 and 

Table 8). However, there was no evidence that the shell mound assemblage of any platform was unique.

The shell mound around Platform B was the most species rich (22 taxa) and that around Habitat (11 

species), Henry (11 species), and Hogan (10 species) harbored the fewest taxa (Figure 7). Similar to our observation around platform bottoms, a substantial inter-annual variation in fish densities at several platforms 

made it difficult to determine if densities varied among platforms (Table 8). Species that exhibited large 

interannual differences in densities included calico, halfbanded, shortbelly and squarespot rockfishes YOYs, 

blue, calico, halfbanded and vermilion rockfishes and California lizardfish. Again, as with platform bottoms, 

small fishes (of 20 cm or less) were by far most abundant in this habitat at all platforms (Figure 11). Species 

that characterized this habitat included calico, halfbanded, squarespot, and vermilion rockfishes, as well as 

California lizardfish, lingcod (particularly YOYs) and painted greenling. 

Platform Midwaters

We observed a total of 100,287 fishes in platform waters, composed of at least 28 species. Of these fishes, 98,587 (98.3% of the total) were rockfishes (of 17 species), and 96.4% of these were YOYs (Table 4). YOY 

rockfishes dominated this habitat and comprised 94.7% of all fishes observed. Densities of five rockfish species (i.e., blue, bocaccio, shortbelly, squarespot, and widow) greatly exceeded those of other taxa (Table 9). 

We observed between 27 (Platform B) and 14 (Platform Henry) species at the eight platforms. No 

pattern in species richness among the platforms was observed. Around most platforms, fish densities varied 

greatly between years (Table 9, Figure 12) and this variability was due to very large interannual differences 

in YOY recruitment of blue, shortbelly, squarespot, and widow rockfishes, bocaccio and blacksmith. Midwater fish assemblages around these eight platforms were fairly similar – perhaps the greatest differences were 

Table 7. (Continued)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Brown rockfish 0.0 0.3 0.1 0.1

Kelp greenling 0.0 0.3 0.1 0.1

Painted greenling 0.0 0.3 0.1 0.1

Painted greenling YOY 0.0 0.3 0.1 0.1

Total 75.4 6.1 40.7 34.6

Minimum number of species 6 9 12

Total rockfish YOY 48.9 0.6 24.7

Total rockfishes 70.5 2.9 36.7

Rockfish YOY %

 of all fishes surveyed 64.8 9.5 60.7

All rockfishes %

 of all fishes surveyed 93.5 47.6 90.1
22

A

B 

C 

Habitat

Henry

Hillhouse

Hogan

Houchin

Platform Shell Mounds 

Canonical Discriminant Analysis

 Standardized Transformed Densities

Discriminant 2 (12%) 

Discriminant 1 (78%) 

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

0

-6

-4

-2

-8

-10

-12

-14

2

4

6

8

Shell Mounds of All Platforms Average Standardized Transformed Densities

-6

-4

-2

0

2

4

6

8

10

12

Average Density

A

B

Habitat

Rest

C1 C2 C3

Cluster

Figure 8. A canonical discriminant analysis of platform shell mound fish assemblages around eight platforms off Summerland, 

California, based on centroids of surveys conducted in 2012–2013.

Figure 9. A comparison of densities of three species clusters on shell mounds around eight platforms off Summerland, California, 

shown in Figure 10.
23

60 m – C

60 m – B

59 m – A

58 m – Hillhouse

53 m – Henry

51 m – Houchen

88 m – Habitat

47 m – Hogan

60 m – C

60 m – B

59 m – A

58 m – Hillhouse

53 m – Henry

51 m – Houchen

88 m – Habitat

47 m – Hogan

40

36

32

48

44

28

24

20

16

12

8

4

200

340

180

160

140

120

100

80

60

40

20

Density of All Species Combined at Shell Mound

 Ordered by Platform Bottom Depth

Number of Species

Density (Fishes per 100m2

)

Number of Species at Shell Mound

Ordered by Platform Bottom Depth

Figure 10. A cluster analysis of the characteristics species of shell mounds around eight platforms off Summerland, California, 

2012–2013.

60 m – C

60 m – B

59 m – A

58 m – Hillhouse

53 m – Henry

51 m – Houchen

88 m – Habitat

47 m – Hogan

60 m – C

60 m – B

59 m – A

58 m – Hillhouse

53 m – Henry

51 m – Houchen

88 m – Habitat

47 m – Hogan

40

36

32

48

44

28

24

20

16

12

8

4

200

340

180

160

140

120

100

80

60

40

20

Density of All Species Combined at Shell Mound

 Ordered by Platform Bottom Depth

Number of Species

Density (Fishes per 100m2

)

Number of Species at Shell Mound

Ordered by Platform Bottom Depth

Figure 11. Number of species and density of all species observed on the shell mounds of eight platforms, 2012–2013. Platforms are 

listed from shallowest to deepest
24

within-platform interannual ones driven by this recruitment variability (Figures 13, 14). The overwhelming 

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

in the platform midwaters were small, 10 cm or less long. 

Discussion

The goal of this research was to provide a more detailed assessment of the fish assemblages at the eight 

platforms off Summerland, California; platforms that are situated in a turbid area that precludes surveys 

with manned submersibles. Here we discuss 1) the species assemblages of these eight platforms and 2) compare how the results of this study dovetails with results from some other platforms.

Previous work (Love et al. 1999a, b, Love and Nishimoto 2012) demonstrated that around most or all 

California platforms there are two distinct fish assemblages; one found in the midwaters above the bottom 

and another formed by the platform bottom and adjacent shell mound. Thus shell mounds usually do not 

harbor distinct fish assemblages, but rather these assemblages have a number of attributes in common with 

those of platform bottoms. In addition, Love et al. (1999a) and Love and Nishimoto (2012) found that, 

among California platforms, the shell mound assemblage was sometimes more similar to the bottom of its 

adjacent platform than to other shell mounds. In the current study, we again found that the bottom and shell 

mound assemblages shared many of the same species across all platforms and that the two habitats were 

often very similar (Figure 15). 

Across the range of the eight platforms, what species were most characteristic of this bottom-shell 

mound habitat? While there was some variability between platforms, this assemblage was primarily composed of a suite of juveniles and adults of dwarf species (i.e. calico, halfbanded, and squarespot rockfishes 

and painted greenling) and juveniles of species that grow relatively large (i.e., copper and vermilion rockfishes) and lingcod. Thus, this was an assemblage comprised primarily of small fishes (Figure 7). Why might 60 m – C 60 m – B 59 m – A 58 m – Hillhouse 53 m – Henry 51 m – Houchen 88 m – Habitat 47 m – Hogan 60 m – C 60 m – B 59 m – A 58 m – Hillhouse 53 m – Henry 51 m – Houchen 88 m – Habitat 47 m – Hogan

40

36

32

48

44

28

24

20

16

12

8

4

200

800

180

500

160

140

120

100

80

60

40

20

Density of All Species Combined at Platform Midwater

 Ordered by Platform Bottom Depth

Number of Species

Density (Fishes per 100m2

)

Number of Species at Platform Midwater

Ordered by Platform Bottom Depth

Figure 12. Number of species and density of all species observed in the midwaters of eight platforms off Summerland, California, 

2012–2013. Platforms are listed from shallowest to deepest.
25

0.4

0.3

0.2

0.1

0

-0.1

-0.2

-0.3

-0.4

A

2012 2013

B C

Habitat

Henry

Hillhouse

Hogan

Houchin

Cluster 1

Cluster 2

Cluster 1

Cluster 2

All Platform Midwaters

Standardized Transformed Densities

Midwaters Average

Standardized Transformed Densities

Density

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

Density

Platform

Year

Figure 13. A comparison of densities of two midwater species clusters at eight platforms off Summerland, California, shown in 

Figure 13.
26

this be the case? There is substantial evidence from both platform and natural reef sites (Caselle et al. 2002, 

Love and York 2006, Love et al. 2006, Love and Yoklavich 2008) that adults of a number of rockfish species 

require sheltering sites. Around platforms, the major sheltering habitat is formed by uncovered (i.e., not 

buried by shells) and undercut bottom crossbeams. Unlike many of the other platforms we have surveyed 

off California, there is substantial shell deposition around much of the bases of the Summerland platforms 

and the result is that the bottom crossbeams are often buried. This is in contrast to the condition found in a 

number of other southern California platforms, where this crossbeam is undercut, creating extensive sheltering areas. The effect of this heavy layer of shells is that, from a fish’s perspective, the platform bottom may 

not be distinguishable from the adjacent shell mound; both lack significant sheltering sites and thus both are 

less suitable for larger individuals of many species. 

While bottom and shell mound fish assemblages share a common core of species, previous research 

from other California platforms has demonstrated that, of the two habitats, both overall species richness 

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

Height

Kelp greenling

California sheephead

Kelp rockfish

Pile perch

Shortbelly rockfish

Kelp bass

Bocaccio

Copper rockfish

Painted greenling

Squarespot rockfish

Blacksmith

Blue rockfish

Widow rockfish

Cabezon

Olive rockfish

Typical of most platforms 

but not of Habitat, 

Henry, and Houchin

More typical of 2013

rather than 2012

Figure 14. A cluster analysis of the characteristics species of platform midwaters of either platforms off Summerland, California, 

2012–2013.
27

Table 8. Densities of all fishes observed from a remotely operated vehicle on the shell mounds of eight platforms in the Santa Barbara 

Channel. Platforms are ordered from westernmost (C) to easternmost (Hogan) with the exception of the more offshore Platform 

Habitat (listed first). Platform bottom depth is listed after platform name. YOY = young-of-the-year. Scientific names are listed in 

Table 4. Note that counts of fishes are not included in this table because varying survey coverage of this precluded meaningful comparison of counts among platforms, habitats, and years.

PLATFORM HABITAT (DEPTH = 88 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Halfbanded rockfish 97.3 84.1 90.7 6.6

Lingcod YOY 8.8 7.6 8.2 0.6

Unidentified flatfishes 0.5 3.5 2.0 1.5

Sebastomus spp. 2.6 0.0 1.3 1.3

Copper rockfish 0.3 1.0 0.6 0.4

Painted greenling 0.5 0.5 0.5 0.0

Unidentified combfishes 0.5 0.5 0.5 0.0

Rosy rockfish 0.5 0.0 0.3 0.3

Unidentified rockfishes 0.5 0.0 0.3 0.3

Unidentified sanddab 0.5 0.0 0.3 0.3

Lingcod 0.0 0.5 0.3 0.3

Unidentified fishes 0.0 0.5 0.3 0.3

Calico rockfish 0.3 0.0 0.1 0.1

Greenspotted rockfish 0.3 0.0 0.1 0.1

Pacific sanddab 0.3 0.0 0.1 0.1

Shortspine combfish 0.3 0.0 0.1 0.1

Squarespot rockfish 0.3 0.0 0.1 0.1

Wolf-eel 0.3 0.0 0.1 0.1

Total 113.8 98.2 106.0 7.8

Minimum number of species 11 5 11

Total rockfish YOY 0.3 0.0 0.1

Total rockfishes 102.2 85.1 93.7

Rockfish YOY % 

 of all fishes surveyed 0.2 0.0 0.1

All rockfishes % 

 of all fishes surveyed 89.8 86.7 88.4

PLATFORM C (DEPTH = 60 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Calico rockfish 11.3 2.1 6.7 4.6

Halfbanded rockfish 0.0 13.1 6.6 6.6

Unidentified sanddab 0.0 11.9 6.0 6.0

Lingcod YOY 3.7 5.4 4.5 0.8

Painted greenling 5.2 2.4 3.8 1.4

Calico rockfish YOY 4.7 0.0 2.3 2.3

Lingcod 0.2 2.1 1.2 0.9

Squarespot rockfish 0.0 2.1 1.0 1.0

Pile perch 2.0 0.0 1.0 1.0

Unidentified flatfishes 0.0 1.8 0.9 0.9

Unidentified rockfishes 0.7 0.9 0.8 0.1

Unidentified fishes 0.7 0.0 0.4 0.4

Cabezon 0.0 0.6 0.3 0.3

Kelp greenling 0.5 0.0 0.2 0.2

Unidentified rockfishes YOY 0.5 0.0 0.2 0.2
28

Unidentified surfperch 0.0 0.3 0.1 0.1

Widow rockfish YOY 0.0 0.3 0.1 0.1

Wolf-eel 0.0 0.3 0.1 0.1

Brown rockfish YOY 0.2 0.0 0.1 0.1

Rosy rockfish 0.2 0.0 0.1 0.1

Unidentified ronquil 0.1

Total 30.2 43.3 36.8 6.5

Minimum number of species 8 9 13

Total rockfish YOY 5.4 0.3 2.9

Total rockfishes 17.7 18.5 18.1

Rockfish YOY % 

 of all fishes surveyed 17.9 0.7 7.8

All rockfishes % 

 of all fishes surveyed 58.5 42.8 49.2

PLATFORM B (DEPTH = 60 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Squarespot rockfish YOY 87.5 0.0 43.7 43.7

Unidentified rockfishes 26.6 1.1 13.8 12.8

Unidentified sanddab 0 24.4 12.2 12.2

Calico rockfish 20.0 2.8 11.4 8.6

Lingcod YOY 8.0 4.2 6.1 1.9

Shortbelly rockfish YOY 11.3 0.0 5.7 5.7

Painted greenling 9.1 1.8 5.4 3.7

Unidentified rockfishes YOY 10.6 0.0 5.3 5.3

Squarespot rockfish 8.0 1.8 4.9 3.1

Unidentified flatfishes 0.0 6.0 3.0 3.0

Vermilion rockfish 3.3 1.1 2.2 1.1

Lingcod 1.1 3.2 2.1 1.0

Unidentified fishes 1.1 2.1 1.6 0.5

Olive rockfish 1.1 1.1 1.1 0.0

Pile perch 1.5 0.4 0.9 0.6

Chilipepper 0.0 1.8 0.9 0.9

Brown rockfish 1.5 0.0 0.7 0.7

Calico rockfish YOY 1.5 0.0 0.7 0.7

Halfbanded rockfish 1.5 0.0 0.7 0.7

Blackeye goby 1.1 0.0 0.5 0.5

Blue rockfish 1.1 0.0 0.5 0.5

Kelp greenling 0.7 0.4 0.5 0.2

Bocaccio 0.0 1.1 0.5 0.5

California lizardfish 0.0 1.1 0.5 0.5

Copper rockfish 0.7 0.0 0.4 0.4

Halfbanded rockfish YOY 0.7 0.0 0.4 0.4

Painted greenling YOY 0.7 0.0 0.4 0.4

Rubberlip seaperch 0.7 0.0 0.4 0.4

Sebastomus spp. 0.4 0.0 0.2 0.2

Spotted scorpionfish 0.4 0.0 0.2 0.2

Unidentified sculpin 0.4 0.0 0.2 0.2

Unidentified surfperch 0.0 0.4 0.2 0.2

Table 8. (Continued)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013
29

Total 200.5 54.5 127.5 73.0

Minimum number of species 17 11 22

Total rockfish YOY 111.5 0.0 55.8

Total rockfishes 175.7 10.6 93.2

Rockfish YOY % 

 of all fishes surveyed 55.6 0.0 43.7

All rockfishes % 

 of all fishes surveyed 87.6 19.5 73.1

PLATFORM A (DEPTH = 59 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Halfbanded rockfish 148.0 6.6 77.3 70.7

Vermilion rockfish 77.7 1.5 39.6 38.1

Blue rockfish 25.9 0.0 13.0 13.0

Calico rockfish 2.5 12.4 7.4 5.0

Copper rockfish 8.6 1.2 4.9 3.7

Squarespot rockfish 8.6 1.2 4.9 3.7

Kelp rockfish 7.4 0.0 3.7 1.9

Brown rockfish 6.2 2.3 4.2 3.7

Olive rockfish 6.2 0.8 3.5 2.7

Lingcod 1.2 3.9 2.6 1.3

Lingcod YOY 3.7 1.2 2.4 1.3

Pile perch 2.5 3.5 2.4 1.2

Unidentified flatfishes 0.0 2.7 1.4 1.2

Painted greenling 1.2 0.4 0.8 0.4

Unidentified sanddab 0.0 1.5 0.8 0.8

Blackeye goby 1.2 0.0 0.6 0.6

Unidentified fishes 1.2 0.0 0.6 0.6

Unidentified rockfishes 0.0 1.2 0.6 0.6

Halfbanded rockfish YOY 0.0 0.4 0.2 0.2

Kelp greenling 0.0 0.4 0.2 0.2

Total 302.2 37.1 169.7 132.5

Minimum number of species 13 10 15

Total rockfish YOY 0.0 0.4 0.2

Total rockfishes 291.1 27.5 159.3

Rockfish YOY % 

 of all fishes surveyed 0.0 1.0 0.1

All rockfishes % 

 of all fishes surveyed 96.3 74.0 93.9

PLATFORM HILLHOUSE (DEPTH = 58 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Calico rockfish 30.7 5.3 18.0 12.7

Halfbanded rockfish 0.0 20.2 10.1 10.1

Unidentified sanddab 0.0 7.2 3.6 3.6

Lingcod YOY 5.8 0.6 3.6 2.6

Painted greenling 2.6 0.8 1.7 0.9

Unidentified flatfishes 0.0 3.0 1.5 1.5

Table 8. (Continued)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013
30

Unidentified surfperch 2.6 0.0 1.3 1.3

Calico rockfish YOY 1.8 0.0 0.9 0.9

Unidentified rockfishes 1.2 0.6 0.9 0.3

California lizardfish 0.0 1.7 0.8 0.8

Vermilion rockfish 1.5 0.0 0.7 0.7

Longspine combfish 0.0 1.1 0.6 0.6

Kelp greenling 0.9 0.0 0.4 0.4

Copper rockfish 0.6 0.3 0.4 0.2

Brown rockfish 0.6 0.0 0.3 0.3

Olive rockfish 0.6 0.0 0.3 0.3

Pile perch 0.6 0.0 0.3 0.3

Unidentified rockfishes YOY 0.6 0.0 0.3 0.3

Lingcod 0.3 0.3 0.3 0.0

Unidentified fishes 0.0 0.6 0.3 0.3

Pink seaperch 0.3 0.0 0.1 0.1

Rosy rockfish 0.3 0.0 0.1 0.1

Spotted scorpionfish 0.3 0.0 0.1 0.1

Flag rockfish 0.0 0.3 0.1 0.1

Gopher rockfish 0.0 0.3 0.1 0.1

Kelp rockfish 0.0 0.3 0.1 0.1

Squarespot rockfish 0.0 0.3 0.1 0.1

Unidentified combfishes 0.0 0.3 0.1 0.1

Yellowtail rockfish 0.0 0.3 0.1 0.1

Total 51.2 43.2 47.2 4.0

Minimum number of species 13 13 21

Total rockfish YOY 2.3 0.0 1.2

Total rockfishes 37.7 27.7 32.9

Rockfish YOY %

 of all fishes surveyed 4.6 0.0 2.5

All rockfishes %

 of all fishes surveyed 73.7 64.1 69.3

PLATFORM HENRY (DEPTH = 53 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Halfbanded rockfish YOY 22.1 0.0 11.1 11.1

Calico rockfish 6.4 6.7 6.5 0.1

Calico rockfish YOY 6.4 0.0 3.2 3.2

California lizardfish 0.0 4.9 2.5 2.5

Lingcod YOY 2.8 1.1 1.9 0.9

Painted greenling 2.0 1.4 1.7 0.3

Squarespot rockfish 0.8 1.8 1.3 0.5

Unidentified rockfishes YOY 1.6 0.4 1.0 0.6

Lingcod 0.4 1.1 0.7 0.3

Olive rockfish 0.0 1.4 0.7 0.7

Unidentified flatfishes 0.0 1.4 0.7 0.7

Unidentified rockfishes 0.0 1.4 0.7 0.7

Unidentified fishes 0.8 0.4 0.6 0.2

Unidentified sanddab 0.0 0.7 0.4 0.4

Unidentified sculpin 0.4 0.0 0.2 0.2

Table 8. (Continued)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013
31

Longspine combfish 0.0 0.4 0.2 0.2

Painted greenling YOY 0.0 0.4 0.2 0.2

Unidentified combfishes 0.0 0.4 0.2 0.2

Unidentified ronquil 0.0 0.4 0.2 0.2

Total 43.8 23.8 33.8 10.0

Minimum Number of Species 7 11 11

Total Rockfish YOY 30.2 0.4 15.3

Total Rockfish 37.4 11.6 24.5

Rockfish YOY percentage 

 of all fishes surveyed 68.8 1.5 45.1

All rockfishes percentage 

 of all fishes surveyed 85.3 48.5 72.4

PLATFORM HOUCHIN (DEPTH = 51 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Halfbanded rockfish YOY 86.6 0.0 43.3 43.3

Calico rockfish YOY 37.2 0.0 18.6 18.6

Brown rockfish 9.3 0.3 4.8 4.5

Calico rockfish 1.4 4.7 3.0 1.6

Painted greenling 4.3 1.7 3.0 1.3

Lingcod YOY 2.9 0.9 1.9 1.0

Unidentified rockfishes 1.4 1.5 1.4 0.0

Pile perch 2.9 0.0 1.4 1.4

Unidentified surfperch 2.1 0.0 1.1 1.1

Unidentified fishes 0.7 1.2 0.9 0.2

Sharpnose seaperch 0.0 1.7 0.9 0.9

Halfbanded rockfish 1.4 0.3 0.9 0.6

Copper rockfish 0.7 0.6 0.6 0.1

Kelp rockfish 0.7 0.0 0.4 0.4

Painted greenling YOY 0.7 0.0 0.4 0.4

Sebastomus spp. 0.7 0.0 0.4 0.4

Unidentified rockfishes YOY 0.7 0.0 0.4 0.4

Vermilion rockfish 0.7 0.0 0.4 0.4

Lingcod 0.0 0.6 0.3 0.3

California lizardfish 0.0 0.3 0.1 0.1

Olive rockfish 0.0 0.3 0.1 0.1

Squarespot rockfish 0.0 0.3 0.1 0.1

Unidentified flatfishes 0.0 0.3 0.1 0.1

Unidentified sanddab 0.0 0.3 0.1 0.1

Unidentified sculpin 0.0 0.3 0.1 0.1

Wolf-eel 0.0 0.3 0.1 0.1

Yellowtail rockfish 0.0 0.3 0.1 0.1

Total 154.6 15.4 85.0 69.6

Minimum number of species 12 13 19

Total rockfish YOY 124.6 0.0 62.3

Total rockfishes 141.0 8.1 74.6

Rockfish YOY %

 of all fishes surveyed 80.6 0.0 73.3

All rockfishes %

 of all fishes surveyed 91.2 52.8 87.7

Table 8. (Continued)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013
32

PLATFORM HOGAN (DEPTH = 47 M)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013

Calico rockfish YOY 22.3 0.3 11.3 11.0

Halfbanded rockfish YOY 13.3 0.3 6.8 6.5

Painted greenling 1.4 1.7 1.6 0.2

Calico rockfish 0.7 1.7 1.2 0.5

California lizardfish 0.0 2.3 1.2 1.2

Unidentified rockfishes YOY 0.7 0.6 0.6 0.1

Lingcod YOY 0.0 1.2 0.6 0.6

Unidentified rockfishes 0.7 0.3 0.5 0.2

Halfbanded rockfish 0.7 0.0 0.3 0.3

Lingcod 0.7 0.0 0.3 0.3

Unidentified fishes 0.7 0.0 0.5 0.3

Pile perch 0.0 0.6 0.3 0.3

Copper rockfish 0.0 0.3 0.1 0.1

Olive rockfish 0.0 0.3 0.1 0.1

Painted greenling YOY 0.0 0.3 0.1 0.1

Unidentified flatfishes 0.0 0.3 0.1 0.1

Widow rockfish YOY 0.0 0.3 0.1 0.1

Total 41.2 10.5 25.8 15.4

Minimum number of species 4 10 10

Total rockfish YOY 36.3 1.5 18.9

Total rockfish 38.4 4.1 21.2

Rockfish YOY %

 of all fishes surveyed 88.1 13.9 73.1

All rockfishes %

 of all fishes surveyed 93.2 38.9 82.2

Table 9. Densities of all fishes observed from a remotely operated vehicle and from scuba surveys around the midwaters of eight platforms in the Santa Barbara Channel. Platforms are ordered from westernmost (C) to easternmost (Hogan) with the exception of the 

more offshore Platform Habitat (listed first). YOY = young-of-the-year. Density is in fish per 100 m2

. Scientific names are listed in 

Table 4.

PLATFORM HABITAT

DENSITY STANDARD ERROR

Species 2012 2013 2012-2013

Squarespot rockfish YOY 102.9 25.3 64.1 38.8

Unidentified rockfishes YOY 75.2 14.6 44.9 30.3

Bocaccio YOY 0.2 67.7 33.9 33.8

Blue rockfish YOY 1.6 55.2 28.4 26.8

Widow rockfish YOY 0.0 26.1 13.1 13.1

Bocaccio 0.0 22.3 11.2 11.2

Squarespot rockfish 2.6 5.1 3.9 1.2

Shortbelly rockfish YOY 6.6 0.5 3.5 3.1

Unidentified rockfishes 0.2 3.5 1.9 1.6

Blue rockfish 0.0 3.7 1.9 1.9

Copper rockfish 0.5 1.9 1.2 0.7

Yellowtail rockfish 0.0 2.0 1.0 1.0

Painted greenling 0.5 1.1 0.8 0.3

Olive rockfish 0.0 1.1 0.6 0.6

Painted greenling YOY 0.7 0.3 0.5 0.2

Table 8. (Continued)
33

Blacksmith 0.0 0.8 0.4 0.4

Kelp greenling 0.4 0.2 0.3 0.1

Lingcod YOY 0.0 0.5 0.2 0.2

Widow rockfish 0.0 0.5 0.2 0.2

Copper rockfish YOY 0.1 0.3 0.2 0.1

Yellowtail rockfish YOY 0.0 0.3 0.2 0.2

Unidentified fishes 0.1 0.2 0.1 0.1

Kelp rockfish 0.0 0.3 0.1 0.1

Cabezon 0.0 0.2 0.1 0.1

Olive rockfish YOY 0.0 0.2 0.1 0.1

Shortbelly rockfish 0.0 0.2 0.1 0.1

Pile surfperch 0.2 0.0 0.1 0.1

Calico rockfish 0.0 0.1 0.1 0.0

Sebastomus sp. 0.0 0.1 0.1 0.0

Total 191.7 234.3 213.0 21.3

Minimum number of species 8 16 18

Total rockfish YOY 186.4 190.3 188.4

Total rockfishes 189.8 230.9 210.4

Rockfish YOY % of all fishes surveyed 97.3 81.2 88.4

All rockfishes % of all fishes surveyed 99.0 98.6 98.8

PLATFORM C

DENSITY STANDARD ERROR

Species 2012 2013 2012-2013

Shortbelly rockfish YOY 201.9 0.3 101.0 100.8

Blue rockfish YOY 5.2 191.9 98.6 93.4

Widow rockfish YOY 0.0 129.5 64.7 64.7

Bocaccio YOY 100.5 22.7 61.6 39.0

Squarespot rockfish YOY 21.0 101.2 61.1 40.1

Unidentified rockfishes YOY 44.0 69.1 56.6 12.5

Unidentified rockfishes 5.4 7.8 6.6 1.2

Bocaccio 0.0 11.5 5.8 5.8

Squarespot rockfish 1.0 5.9 3.4 2.4

Blacksmith 0.0 5.1 2.6 2.6

Painted greenling 3.2 1.5 2.4 0.9

Widow rockfish 0.0 2.2 1.1 1.1

Pile surfperch 1.2 0.7 0.9 0.3

Blue rockfish 0.0 1.6 0.8 0.8

Blacksmith YOY 0.0 1.2 0.6 0.6

Painted greenling YOY 0.5 0.2 0.4 0.2

Kelp rockfish 0.4 0.2 0.3 0.1

Olive rockfish 0.1 0.4 0.3 0.2

Kelp bass 0.0 0.5 0.2 0.2

Copper rockfish YOY 0.2 0.3 0.2 0.1

Kelp greenling 0.3 0.2 0.2 0.1

Vermilion rockfish 0.4 0.0 0.2 0.2 

Senorita 0.0 0.3 0.1 0.1

Copper rockfish 0.1 0.2 0.1 0.1

Unidentified surfperch 0.0 0.2 0.1 0.1

Cabezon 0.1 0.1 0.1 0.1

Table 9. (Continued)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013
34

California sheephead 0.0 0.1 0.1 0.1

Calico rockfish YOY 0.1 0.0 0.1 0.1

Halfbanded rockfish 0.1 0.0 0.1 0.1

Gopher rockfish 0.0 0.1 0.1 0.1

Lingcod 0.0 0.1 0.1 0.1

Lingcod YOY 0.0 0.1 0.1 0.1

Unidentified fishes 0.00 0.1 0.1 0.1

Total 385.9 554.7 470.3 84.4

Minimum number of species 14 18 22

Total rockfish YOY 373.0 514.9 443.9

Total rockfishes 380.6 544.7 462.6

Rockfish YOY % of all fishes surveyed 96.7 92.8 94.4

All rockfishes % of all fishes surveyed 98.6 98.2 98.4

PLATFORM B

DENSITY STANDARD ERROR

Species 2012 2013 2012-2013

Squarespot rockfish YOY 11.4 235.9 123.7 112.3

Widow rockfish YOY 0.0 241.6 120.8 120.8

Blue rockfish YOY 16.1 194.5 105.3 89.2

Shortbelly rockfish YOY 21.2 69.3 45.3 24.0

Bocaccio 0.0 21.0 10.5 10.5

Unidentified rockfishes YOY 5.4 13.8 9.6 4.2

Squarespot rockfish 0.8 11.5 6.2 5.4

Bocaccio YOY 0.0 12.0 6.0 6.0

Blue rockfish 0.0 9.7 4.9 4.9

Blacksmith YOY 0.0 7.6 3.8 3.8

Blacksmith 0.0 5.8 2.9 2.9

Olive rockfish 0.1 2.4 1.2 1.1

Unidentified rockfishes 1.1 1.4 1.2 0.2

Widow rockfish 0.0 1.8 0.9 0.9

Painted greenling 0.6 1.1 0.9 0.3

Kelp rockfish 0.6 0.5 0.6 0.1

California sheephead 0.7 0.4 0.6 0.2

Painted greenling YOY 0.7 0.4 0.5 0.2

Kelp greenling 0.2 0.5 0.3 0.1

Vermilion rockfish 0.0 0.3 0.2 0.2

Yellowtail rockfish 0.0 0.3 0.2 0.2

Kelp bass 0.1 0.2 0.2 0.1

Senorita 0.1 0.2 0.2 0.1

Unidentified fishes 0.3 0.0 0.1 0.1

Pile surfperch 0.1 0.2 0.1 0.1

Lingcod 0.0 0.2 0.1 0.1

Sharpnose surfperch 0.1 0.1 0.1 0.1

Unidentified surfperch 0.2 0.0 0.1 0.1

Lingcod YOY 0.0 0.2 0.1 0.1

Garibaldi 0.1 0.1 0.1 0.1

Gopher rockfish 0.0 0.1 0.1 0.1

Shortbelly rockfish 0.1 0.0 0.1 0.1

Vermilion rockfish YOY 0.1 0.0 0.1 0.1

Black-and-yellow rockfish 0.0 0.1 0.1 0.1

Table 9. (Continued)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013
35

Brown rockfish 0.0 0.1 0.1 0.1

Cabezon 0.0 0.1 0.1 0.1

Copper rockfish 0.0 0.1 0.1 0.1

White surfperch 0.0 0.1 0.1 0.03

Total 59.9 833.2 446.5 386.6

Minimum number of species 14 25 27

Total rockfish YOY 54.2 767.1 410.7

Total rockfishes 56.8 816.3 436.6

Rockfish YOY % of all fishes surveyed 90.4 92.1 92.0

All rockfishes % of all fishes surveyed 94.8 98.0 97.8

PLATFORM A

DENSITY STANDARD ERROR

Species 2012 2013 2012-2013

Shortbelly rockfish YOY 501.6 1.2 251.4 250.2

Squarespot rockfish YOY 15.6 393.1 204.3 188.7

Blue rockfish YOY 1.1 294.0 147.5 146.4

Widow rockfish YOY 0.0 143.2 71.6 71.6

Bocaccio YOY 0.4 31.6 16.0 15.6

Blacksmith YOY 1.9 23.8 12.8 11.0

Squarespot rockfish 0.0 13.7 6.8 6.8

Unidentified rockfishes YOY 0.6 10.1 5.3 4.8

Bocaccio 0.0 9.6 4.8 4.8

Blue rockfish 6.9 0.7 3.8 3.1

Blacksmith 0.0 2.6 1.3 1.3

Sharpnose surfperch 0.0 2.1 1.1 1.1

Painted greenling 0.4 1.5 1.0 0.6

California sheephead 0.4 1.1 0.7 0.3

Kelp rockfish 0.7 0.5 0.6 0.1

Pile surfperch 0.6 0.6 0.6 0.0

Kelp greenling 0.4 0.7 0.5 0.2

Olive rockfish 0.0 1.0 0.5 0.5

Unidentified surfperch 0.7 0.0 0.4 0.4

Painted greenling YOY 0.4 0.3 0.3 0.1

Widow rockfish 0.0 0.6 0.3 0.3

Kelp bass 0.0 0.5 0.3 0.3

Vermilion rockfish 0.0 0.4 0.2 0.2

Copper rockfish 0.0 0.2 0.1 0.1

Gopher rockfish 0.0 0.2 0.1 0.1

Cabezon 0.0 0.1 0.1 0.1

Unidentified rockfishes 0.0 0.1 0.1 0.1

Brown rockfish 0.0 0.1 0.1 0.1

Lingcod 0.0 0.1 0.1 0.1

Olive rockfish YOY 0.0 0.1 0.1 0.1

Yellowtail rockfish 0.0 0.1 0.1 0.1

Total 531.5 933.5 732.5 201.0

Minimum number of species 10 21 22

Total rockfish YOY 519.3 873.2 696.2

Total rockfishes 526.9 900.2 713.5

Rockfish YOY % of all fishes surveyed 97.7 93.5 95.1

All rockfishes % of all fishes surveyed 99.1 96.4 97.4

Table 9. (Continued)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013
36

PLATFORM HILLHOUSE

DENSITY STANDARD ERROR

Species 2012 2013 2012-2013

Shortbelly rockfish YOY 390.1 0.1 195.1 195.0

Blue rockfish YOY 0.0 299.7 149.8 149.8

Squarespot rockfish YOY 94.1 154.7 124.4 30.3

Widow rockfish YOY 0.2 45.1 22.6 22.5

Unidentified rockfishes YOY 9.8 9.1 9.4 0.4

Bocaccio YOY 0.2 6.9 3.5 3.4

Gopher rockfish YOY 0.0 2.9 1.5 1.5

Painted greenling 1.0 1.5 1.3 0.3

Blue rockfish 0.0 2.3 1.2 1.2

Squarespot rockfish 0.3 1.1 0.7 0.4

Blacksmith YOY 0.0 1.4 0.7 0.7

Painted greenling YOY 0.7 0.2 0.5 0.3

Unidentified surfperch 0.9 0.0 0.4 0.4

Pile surfperch 0.7 0.0 0.4 0.4

Cabezon 0.0 0.6 0.3 0.3

Olive rockfish 0.0 0.6 0.3 0.3

Widow rockfish 0.0 0.6 0.3 0.3

Blacksmith 0.0 0.6 0.3 0.3

Yellowtail rockfish 0.0 0.5 0.3 0.3

Copper rockfish YOY 0.2 0.2 0.2 0.1

Kelp rockfish 0.2 0.2 0.2 0.1

Kelp greenling 0.2 0.1 0.1 0.1

California sheephead 0.0 0.2 0.1 0.1

Kelp bass 0.0 0.2 0.1 0.1

Unidentified rockfishes 0.0 0.1 0.1 0.1

White surfperch 0.0 0.1 0.1 0.1

Gopher rockfish 0.0 0.1 0.1 0.1

Total 498.3 529.2 513.8 15.4

Minimum number of species 9 17 19

Total rockfish YOY 494.4 518.7 506.6

Total rockfishes 494.8 524.3 509.6

Rockfish YOY % of all fishes surveyed 99.2 98.0 98.6

All rockfishes % of all fishes surveyed 99.3 99.1 99.2

PLATFORM HENRY

DENSITY STANDARD ERROR

Species 2012 2013 2012-2013

Blue rockfish YOY 6.0 176.2 91.1 85.1

Squarespot rockfish YOY 65.0 112.1 88.6 23.6

Widow rockfish YOY 0.5 152.2 76.4 75.9

Unidentified rockfishes YOY 5.1 10.6 7.9 2.8

Sharpnose surfperch 4.6 0.0 2.3 2.3

Halfbanded rockfish YOY 2.3 1.0 1.6 0.7

Painted greenling 0.5 1.2 0.8 0.4

Kelp bass 0.7 0.7 0.7 0.1

Copper rockfish YOY 0.7 0.1 0.4 0.3

Blacksmith YOY 0.0 0.7 0.4 0.4

Painted greenling YOY 0.0 0.5 0.3 0.3

Olive rockfish 0.0 0.4 0.2 0.2

Unidentified rockfishes 0.0 0.4 0.2 0.2

Table 9. (Continued)
37

Kelp greenling 0.2 0.2 0.2 0.1

Squarespot rockfish 0.0 0.4 0.2 0.2

Copper rockfish 0.2 0.0 0.1 0.1

Shortbelly rockfish YOY 0.0 0.2 0.1 0.1

Blue rockfish 0.0 0.1 0.1 0.1

Pile surfperch 0.0 0.1 0.1 0.1

Unidentified fishes 0.0 0.1 0.1 0.1

Widow rockfish 0.0 0.1 0.1 0.1

Total 85.9 457.2 271.5 185.7

Minimum number of species 9 12 14

Total rockfish YOY 79.6 452.3 266.0

Total rockfishes 79.8 453.7 266.8

Rockfish YOY % of all fishes surveyed 92.7 98.9 98.0

All rockfishes % of all fishes surveyed 93.0 99.2 98.3

PLATFORM HOUCHIN

DENSITY STANDARD ERROR

Species 2012 2013 2012-2013

Unidentified rockfishes YOY239.8 54.5 147.1 92.7

Bocaccio YOY 270.8 20.5 145.6 125.2

Blue rockfish YOY 0.0 283.7 141.8 141.8

Squarespot rockfish YOY 0.1 154.7 77.4 77.3

Widow rockfish YOY 0.0 61.2 30.6 30.6

Shortbelly rockfish YOY 0.0 22.9 11.5 11.5

Vermilion rockfish YOY 0.0 5.9 3.0 3.0

Copper rockfish YOY 0.0 2.9 1.4 1.4

Painted greenling 0.4 1.7 1.0 0.7

Kelp bass 0.6 0.1 0.3 0.3

Pile surfperch 0.5 0.2 0.3 0.2

Unidentified rockfishes 0.0 0.6 0.3 0.3

Olive rockfish 0.4 0.2 0.3 0.1

Painted greenling YOY 0.2 0.2 0.2 0.0

Kelp rockfish 0.2 0.7 0.1 0.1

Halfbanded rockfish YOY 0.0 0.2 0.1 0.1

Lingcod YOY 0.0 0.2 0.1 0.1

Squarespot rockfish 0.0 0.2 0.1 0.1

Yellowtail rockfish 0.0 0.2 0.1 0.1

Unidentified fishes 0.1 0.0 0.1 0.1

Bocaccio 0.0 0.1 0.1 0.1

California sheephead 0.0 0.1 0.1 0.1

Brown rockfish 0.0 0.1 0.1 0.1

Cabezon 0.0 0.1 0.1 0.1

Grass rockfish 0.0 0.1 0.1 0.1

Widow rockfish 0.0 0.1 0.1 0.1

Total 513.1 610.4 561.7 48.7

Minimum number of species 7 19 20

Total rockfish YOY 510.7 606.3 558.5

Total rockfishes 511.3 607.8 559.6

Rockfish YOY % of all fishes surveyed 99.6 99.3 99.4

All rockfishes % of all fishes surveyed 99.7 99.6 99.6

Table 9. (Continued)

DENSITY STANDARD ERROR

Species 2012 2013 2012–2013
38

PLATFORM HOGAN

DENSITY STANDARD ERROR

Species 2012 2013 2012-2013

Squarespot rockfish YOY 11.4 156.2 83.8 72.4

Blue rockfish YOY 9.3 125.1 67.2 57.9

Unidentified rockfishes YOY 67.7 61.3 64.5 3.2

Shortbelly rockfish YOY 96.5 1.1 48.8 47.7

Widow rockfish YOY 0.0 36.4 18.2 18.2

Squarespot rockfish 0.2 28.3 14.3 14.0

Bocaccio YOY 3.5 1.6 2.5 1.0

Blacksmith YOY 0.0 4.6 2.3 2.3

Copper rockfish YOY 0.0 4.3 2.2 2.2

Blue rockfish 0.0 3.2 1.6 1.6

Olive rockfish 0.1 2.3 1.2 1.1

Unidentified rockfishes 0.0 1.8 0.9 0.9

Painted greenling 0.5 1.2 0.8 0.4

California sheephead 0.8 0.3 0.6 0.3

Kelp rockfish 0.6 0.4 0.5 0.1

Pile surfperch 0.2 0.4 0.3 0.1

Blacksmith 0.0 0.4 0.2 0.2

Kelp greenling 0.4 0.1 0.2 0.1

Kelp bass 0.4 0.0 0.2 0.2

Painted greenling YOY 0.2 0.1 0.2 0.1

Unidentified fishes 0.1 0.1 0.1 0.1

Widow rockfish 0.0 0.1 0.1 0.1

Copper rockfish 0.1 0.0 0.1 0.1

Unidentified surfperch 0.1 0.0 0.1 0.1

Cabezon 0.0 0.1 0.1 0.1

Olive rockfish YOY 0.0 0.1 0.1 0.1

Yellowtail rockfish 0.0 0.1 0.1 0.1

Total 192.0 429.3 310.7 118.7

Minimum number of species 12 15 17

Total rockfish YOY 188.3 386.0 287.2

Total rockfishes 189.4 422.2 305.8

Rockfish YOY % of all fishes surveyed 98.1 89.9 92.4

All rockfishes % of all fishes surveyed 98.6 98.3 98.4

Table 9. (Continued)

and mean fish lengths are often greater at platform bottoms (Love et al. 2010). And indeed, in our current 

research, species richness at platform bottoms was greater at six of eight platforms (Figures 6, 11, Tables 7, 8) 

and overall mean length was slightly larger at platform bottoms (Table 10). What might lead to this disparity? We suspect that while there is substantial similarity in the dominant species found at the two habitats, 

bottom habitats with their pilings and crossbeams (if not covered over with shells) tend to provide extra 

structural complexity, providing habitat for 1) additional, but rare, species and 2) slightly larger individuals. 

On the other hand, intra-platform, overall fish densities tended to be similar at these two habitats (Love et al. 

2010) and we found this also to be true in five of eight platforms our current study; although fish densities 

at the bottoms of three platforms were higher than at adjacent shell mounds (Figure 16, Tables 7, 8).

Among California platforms, it is clear that along with habitat characteristics such as the degree of 

bottom crossbeam undercut, platform bottom depth is also a major factor in the structuring of species’ assemblages (a parameter also important on natural reefs) (Love et al. 2009, Love et al. 2010). In line with these 

observations, we compared the bottom and shell mound assemblages of the Summerland platforms with 
39

previous findings from Platforms Holly and Gilda; these structures are located within the Santa Barbara 

Channel and are in similar bottom depths (Table 1). We found that the Summerland fish assemblages are 

closely related to these two other platforms (Figure 17, Table 11). Moreover, Love et al. (2010) determined 

that this platform bottom fish assemblage is found in similar-depth platforms from north of Point Arguello 

to off Long Beach and labeled it the “shallowest depth” platform bottom assemblage. What is particularly interesting about these similarities is that they occur in platforms ranging over more than 300 km of coastline 

in platforms found within at least two water masses. Given that the Summerland platforms are arguably in 

some of the most turbid waters of any California platforms, the implication is that bottom turbidity plays 

less of a role in structuring fish assemblages as do other habitat characteristics such as bottom depth.

The midwaters of most California platforms are fish nursery grounds and are dominated by YOY and 

somewhat older juvenile fishes (primarily rockfishes, but also juveniles of such taxa as blacksmith, garibaldi, 

kelp and painted greenlings). In addition, and to a lesser extent at many platforms, there is also a suite of 

the adults of a number of “typical” reef fishes (e.g., blacksmith, garibaldi, sheephead, pile perch, and white 

seaperch) (Love et al. 1999a, Love et al. 2003, Love et al. 2010, Nishimoto and Love 2011). The midwater assemblages of the Summerland platforms followed this pattern, with YOY and juvenile rockfishes (of at least 

five species and the KGB complex [i.e., black-and-yellow, copper, gopher, and kelp) and, to a lesser extent, 

blacksmith, comprising the majority of all the fishes observed (Table 9).

This current research, and that at other platforms in previous years, demonstrates the following:

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

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

17). The Summerland platforms lie in a particularly depositional and turbid zone and, arguably, Holly and 

Gilda lie in waters that are at least somewhat less turbid. In addition, many of the species that characterize 

all of these platforms are also found over natural reefs in relatively clear waters. This implies that there is a 

suite of species that is able to tolerate a broad range of water clarity. Moreover, it also implies that platform 

bottom depth, rather than water clarity, is a major factor in generating species assemblages.

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

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

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

depths. As an example, both blue and olive rockfishes recruit to platform midwaters and are also able to tolerate the bottom depths at the Summerland platforms. This is not the case at such deeper-water platforms 

as Gail and Eureka, whose bottom depths are too deep for these species. Thus, in the case of Gail and Eureka, 

there is more of a disconnect among the species assemblages. We also note that a number of other taxa typical of platform midwaters, such as garibaldi and white seaperch, are able to live around the bottom of the 

Summerland platforms, but are unable to live at the bottom of deeper platforms.

3) Based on the high densities of juveniles, one of the major functions of the Summerland platforms is as a nursery ground for a suite of species, primarily rockfishes but also including lingcod and 

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

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

fraction of the total fish population. Juvenile fishes predominate, not only because rockfishes are extremely 

important to California coastal shelf assemblages, but because the life history patterns of this group dictate 

the overwhelming importance of juvenile fishes at these structures.

Although there are a few exceptions, in general there are two life history patterns among the rockfishes:

A) Those species that recruit to shallow waters and remain there through adulthood (e.g., such nearshore species as blue, gopher, and olive rockfishes) and B) those species that recruit to shallow waters and 

move deeper as they mature (e.g., bocaccio, halfbanded, shortbelly, and widow rockfishes). However, for 

reasons discussed below, it is likely that the young of most of the characteristic Summerland platform rockfishes use the Summerland platforms only during early life stages. 
40

Table 10. Overall mean total lengths (cm) of fishes observed around the bottoms, shell mounds, and midwaters of eight platforms off 

Summerland, California, 2012–2013. 

BOTTOM SHELL MOUND MIDWATER

Number counted 5,193 2,822 100,287

Mean 13.2 12.4 6.2

Standard error 0.1 0.01 0.12

Table 11. A summary of the average densities (fishes per 100 m2) of each species observed around Platforms Gilda (surveyed all years 

between 2001 and 2009 except 2002 and 2005) and Holly (surveyed all years between 1996 and 2010 except 2000 and 2002) based on 

manned submersible surveys, all habitats and all years combined. YOY = young-of-the-year. Scientific names are listed in Table 3.

AVERAGE DENSITY

Species Platform Gilda Platform Holly Both Platforms

Halfbanded rockfish 231.6 9.5 120.6

Calico rockfish 9.9 27.6 18.7

Bocaccio 29.2 0.2 14.7

Jack mackerel 0.0 29.2 14.6

Vermilion rockfish 20.5 6.0 13.3

Shortbelly rockfish 17.3 0.1 8.6

Squarespot rockfish 0.3 14.5 7.4

Pacific sardine 0.0 12.7 6.4

Widow rockfish YOY 0.0 12.2 6.1

Unidentified rockfish YOY 5.0 6.5 5.7

Lingcod YOY 7.0 1.0 4.0

Painted greenling 4.4 2.7 3.6

Squarespot rockfish YOY 1.5 4.8 3.1

Copper rockfish 1.0 4.5 2.8

Sharpnose seaperch 0.7 2.9 1.8

Widow rockfish 1.8 1.8 1.8

Rosy rockfish 0.4 2.2 1.3

Blacksmith YOY 0.3 1.7 1.0

Unidentified rockfishes 0.7 1.3 1.0

Blackeye goby 0.1 1.9 1.0

Pink seaperch 0.5 1.3 0.9

Brown rockfish 0.6 1.1 0.8

Pile perch 0.8 0.7 0.8

Unidentified flatfishes 1.1 0.4 0.8

Painted greenling YOY 0.3 1.1 0.7

Halfbanded rockfish YOY 0.0 1.4 0.7

Lingcod 0.6 0.5 0.5

Pacific sanddab 0.2 0.8 0.5

Flag rockfish 0.4 0.7 0.5

Vermilion rockfish YOY 0.9 0.1 0.5

Unidentified ronquil 0.1 0.8 0.5

Canary rockfish 0.2 0.8 0.5

Sebastomus spp. 0.1 0.8 0.4

Olive rockfish 0.3 0.6 0.4

Kelp rockfish 0.2 0.6 0.4

Unidentified sanddab 0.5 0.3 0.4

Bocaccio YOY 0.2 0.4 0.3

Unidentified surfperch 0.1 0.5 0.3

Blacksmith 0.2 0.3 0.2

Honeycomb rockfish 0.0 0.4 0.2

White seaperch 0.4 0.0 0.2
41

Kelp greenling 0.1 0.3 0.2

Shortspine combfish 0.2 0.2 0.2

Cabezon 0.3 0.1 0.2

Blue rockfish 0.0 0.3 0.2

Unidentified fishes 0.1 0.2 0.2

Sebastomus YOY 0.1 0.2 0.2

Copper rockfish YOY 0.1 0.2 0.1

Spotted scorpionfish 0.1 0.1 0.1

Treefish 0.1 0.2 0.1

Halfmoon 0.2 0.0 0.1

Gopher rockfish 0.1 0.1 0.1

Yellowtail rockfish YOY 0.0 0.2 0.1

Bluebanded ronquil 0.1 0.1 0.1

Unidentified combfishes 0.1 0.1 0.1

Pacific hake 0.0 0.1 0.1

Calico rockfish YOY 0.1 0.1 0.1

Rubberlip seaperch 0.1 0.1 0.1

Yellowtail rockfish 0.0 0.1 0.1

Starry rockfish 0.1 0.1 0.1

Longspine combfish 0.1 0.1 0.1

Unidentified sculpin 0.1 0.1 0.1

Flag rockfish YOY 0.0 0.1 0.1

Starry rockfish YOY 0.1 0.1 0.1

Brown rockfish YOY 0.1 0.1 0.1

Stripefin ronquil 0.0 0.1 0.1

Bull sculpin 0.0 0.1 0.1

Chilipepper 0.1 0.1 0.1

Wolf-eel 0.1 0.1 0.1

Rosy rockfish YOY 0.1 0.1 0.1

California lizardfish 0.0 0.1 0.1

California halibut 0.1 0.0 0.1

Greenspotted rockfish 0.1 0.1 0.1

Olive rockfish YOY 0.1 0.1 0.1

Yelloweye rockfish 0.1 0.1 0.1

Treefish YOY 0.1 0.0 0.1

Yelloweye rockfish YOY 0.0 0.1 0.1

Opaleye 0.1 0.0 0.1

Honeycomb rockfish YOY 0.0 0.1 0.1

Starry flounder 0.0 0.1 0.1

Grass rockfish 0.1 0.0 0.1

Stripetail rockfish 0.1 0.0 0.1

Cowcod 0.0 0.1 0.1

Shortspine thornyhead 0.0 0.1 0.1

Icelinus spp. 0.0 0.1 0.1

Cowcod YOY 0.0 0.1 0.1

Ocean sunfish 0.0 0.1 0.1

Total 341.1 160.2 250.6

Minimum Number of Species 42 50 55

Total Rockfish YOY 7.8 26.3 17.1

Total Rockfish 322.3 99.7 211.1

% Rockfish YOY 2.3 16.4 6.8

% Rockfish 94.5 62.3 84.2

Table 11. (Continued)

AVERAGE DENSITY

Species Platform Gilda Platform Holly Both Platforms
42

A bottom

A shell mound

B bottom 

B shell mound

C bottom 

C shell mound

Habitat botttom

Habitat shell mound

Henry bottom

Henry shell mound

Hillhouse bottom

Hillhouse shell mound

Hogan bottom

Hogan shell mound

Houchin bottom

Houchin shell mound

Platform Bottoms and Shell Mounds

 Canonical Discriminant Analysis

Standardized Transformed Densities

Discriminant 2 (19%) 

Discriminant 1 (58%) 

-20 -10 0 10 20 30 40 50 60 70 80

5

0

-5

-10

-20

-15

10

15

Figure 15. A canonical discriminant analysis of bottom and shell mound assemblages at eight platforms off Summerland, California, 

based on centroids of surveys conducted in 2012–2013.

Let us first look at species using life history pattern A. It might be expected that species such as blue and 

olive rockfishes, having recruited to the platform midwaters, would take up permanent residence as adults. 

This would be because the adult depths of these species include the bottom depths of most of these platforms. However, the adults of these species appear to require complex habitat with suitable sheltering sites. 

As noted previously, the Summerland platforms have relatively few such sites, in fact none in midwaters and 

few at the bottoms or shell mounds. The exceptions to this need for shelter are calico and halfbanded rockfishes. These species recruit to the platform bottoms and shell mounds and, as adults, likely remain there 

throughout their lives.

Fishes that fall into category B — recruiting shallow and moving deeper as they mature — are also very 

abundant at the Summerland platforms. However, in this instance the platform bottom depths are too shallow for the adult stages; these fishes use the platforms are settlement areas and then migrate deeper, often 

within a year of arrival. As an example, movements of YOY bocaccio from the Summerland platforms to a 

variety of natural reefs were documented by Hartmann (1987). Parenthetically, we note that the bottoms of 

deepwater platforms tend to harbor larger fishes and some of these adults likely derive from individuals that 

recruit to the platform midwater and move downwards as they mature. For instance, it is highly likely that 

the high densities of adult bocaccio living at the bottom of Platform Gail are derived from YOYs that had 

settled out a few years before (M. Love, unpubl. data). Lastly, an exception to all of these patterns is probably the vermilion rockfish. YOYs of this species do not recruit to platform midwaters; rather they settle out 

in shallow, low-relief substrate in the nearshore (shallower than the Summerland platforms) and within a 

short time likely migrate to these platforms where at least some likely remain until they mature.

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

regardless of platform bottom depth, because juvenile rockfish recruitment varies (sometimes dramatically) 

between years (Nishimoto and Love 2011). At many shallower platforms (such as those off Summerland) 

the three habitat assemblages, which share a variety of juvenile rockfish species, are linked and thus fish 
43

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Figure 16. Mean overall densities (with standard errors) of all fishes observed during 2012–2013, midwaters, bottoms, and shell 

mounds of eight platforms off Summerland, California.
44

All Platforms Canonical Discriminant Analyses

A bottom

A midwater

B bottom 

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Gilda bottom

C shell mound

Gilda midwater

Gilda shell mound

Habitat bottom

Habitat midwater

Habitat shell mound

Henry bottom

Henry midwater

Henry shell mound

Hillhouse bottom

Hillhouse midwater

Hillhouse shell mound

Hogan bottom

Hogan midwater

Hogan shell mound

Holly bottom

Holly midwater

Discriminant 2 (13%) 

Discriminant 1 (45%)

-80 -60 -40 -20 0 20 40

-50

-40

-30

-20

-10

0

10

20

30

Figure 17. A canonical discriminant analysis of midwater, bottom, and shell mound assemblages at eight platforms off Summerland, 

California, and at two other platforms (Holly and Gilda) also in the Santa Barbara Channel. 

densities at all depths and habitats may vary greatly interannually (Figure 16). This contrasts with the fish assemblages at the bottoms of deeper platforms. Here adult fishes are most important. Many of these individuals are likely to be resident and thus overall fish densities are more stable over time (M. Love, unpubl. data). 

5) However, it is noteworthy that any annual large-scale variability in fish densities does not necessarily 

mean that the overall composition of any fish assemblage will substantially alter. Our research has shown 

that, regardless of recruitment success by any species in any given year, there remains a typical suite of rockfish species (along with such other taxa as blacksmith and kelp and painted greenlings) that recruit from the 

plankton to platform midwaters, bottoms, and shell mounds. Among the rockfishes, these species include 

blue, the kelp, gopher, and brown complex, olive, shortbelly, widow, and yellowtail rockfishes, as well as bocaccio. On the shell mound and platform bottoms, heavily recruiting species include calico and halfbanded 

rockfishes, as well as rockfishes of the Sebastomus subgenus (e.g., greenspotted, rosy, and swordspine), cowcod, and lingcod. Thus, absent a profound regime shift, that causes a number of fish species to either leave or 

enter California waters, the overall species assemblages are likely to remain intact. And it would be expected 

that should offshore structures for renewable energy or oil and gas production be installed in similar water 

depths, either somewhat further northwards (into central California) or southwards (below the Long Beach 

area), their species assemblages would be similar to those found around current structures.
45

Table 12. A summary of YOY recruitment patterns for five rockfish species in the midwaters of eight platforms off Summerland, 

2012–2013. Using blue rockfish as an example, at least one YOY was observed at six platforms in 2012 and at all eight platforms in 

2013. However, the highest densities of this species at each platform were observed in 2013. Data summarized from Table 8.

NUMBER OF PLATFORMS YEAR WITH HIGHEST DENSITY

RECRUITED TO

2012 2013 2012 2013

Blue rockfish 6 8 8

Widow rockfish 2 8 8

Squarespot rockfish 8 8 1 7

Bocaccio 6 7 2 5

Shortbelly rockfish 5 8 3 5

6) As noted previously, YOY rockfish recruitment varies between years at the Summerland platforms. 

However, for at least some rockfish species, there is also substantial within-year inter-platform consistency 

in both recruitment occurrences and recruitment strength. In Table 12, we have summarized YOY recruitment patterns of five rockfish species. Two of the species, blue and olive rockfishes, displayed complete homogeneity in recruitment patterns. In both instances, rockfishes recruited to at least some platforms in both 

years, but highest densities at all of the platforms for each species were observed in 2013. Recruitment of the 

three other species (i.e., shortbelly and squarespot rockfishes and bocaccio) was somewhat more variable, 

but again in each case densities of these taxa were highest in 2013. From this it is clear that, at least for these 

species, those oceanographic factors that drive recruitment success impact a taxonomically wide range of 

pelagic juvenile rockfishes. 

7) We would like to reinforce our previous findings (Love and York 2006, Love et al. 2006) that structure complexity, for instance as exemplified by degree of bottom-crossbeam undercut, appears to be a major 

factor in structuring both species richness and density, particularly of the adults of larger reef fishes. This 

is true both around the bottoms of platforms and on natural reefs. Additional evidence for the role of 

complexity comes from our surveys of the midwaters of Platform Eureka, whose crossbeams are unique 

in their quite varied complexity and whose species assemblage resembles a bottom habitat yet are actually 

in mid-water depths. (Love et al. 2010). Although there was relatively little complexity at the Summerland 

platforms, we note that Platform B, with the highest species richness, also had the most debris on bottom 

and shell mound. Although we have not yet quantified the amount of debris around platforms, our sense 

is that the bottom and shell mound of Holly, another very species-rich platform, also is one of the more 

debris-ridden. Regarding the decommissioning of California platforms, these observations might have a 

bearing on what options might be most appropriate as platforms lacking bottom complexity, and therefore 

harboring fewer species and numbers of some fishes, might be candidates for adding additional structure on 

the seafloor around the platforms.

Acknowledgments

We thank S. Clark, M. McCrea, and L. Snook for their support and W. Lenarz for the statistical analyses.
46

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