Population Trends and Trophic Dynamics 

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FINAL TECHNICAL SUMMARY 

STUDY TITLE: Population Trends and Trophic Dynamics in Pacific OCS Ecosystems: 

What Can Monitoring Data Tell Us? 

REPORT TITLE: Population Trends and Trophic Dynamics in Pacific OCS Ecosystems: 

What Can Monitoring Data Tell Us? 

CONTRACT NUMBER: 14-35-0001-30758 

SPONSORING OCS REGION: Pacific 

APPLICABLE PLANNING AREA(S): Southern California 

FISCAL YEAR(S) OF PROJECT FUNDING: FY 97, FY 98, FY 99, FY 00, FY 01 

COMPLETION DATE OF REPORT: October 2006 

COSTS: FY 97-01 - $195,000 

CUMULATIVE PROJECT COST: $195,000 

PROJECT MANAGER: Russell J. Schmitt

AFFILIATION: Coastal Research Center, Marine Science Institute, University of 

California, Santa Barbara, CA 93106 

ADDRESS: University of California, Santa Barbara, CA 93106 

PRINCIPAL INVESTIGATORS: Russell J. Schmitt1,2 and Andrew J. Brooks1,3

ADDRESSES: 1

Coastal Research Center, 2 Department of Ecology, Evolution and Marine 

Biology, 3

Marine Science Institute, University of California, Santa Barbara, CA 93106-6150 

KEY WORDS: Trophic dynamics; climate change; food web ecology; PDO; Southern 

California bight

BACKGROUND: A number of entities (including MMS) have devoted considerable effort and 

resources to the long-term monitoring of various components of the coastal marine ecosystems in 

the Southern California outer-continental shelf (OCS) region. The primary goals of such 

monitoring programs are to estimate the current state of the biota and to identify long-term trends 

in population demographics. Data from such studies are vital to resource and regulatory 

agencies as they provide critical baseline information needed for accurate assessment of potential 

effects arising from such particular activities as offshore oil and gas production. The 
Final Technical Summary – Schmitt and Brooks 

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fundamental need for such information is evidenced by the growing number of coastal marine 

monitoring programs that have been implemented in Southern California. 

The vast amount of long-term data on nearshore biota collected by a large number of separate 

monitoring programs in the Southern California OCS region represents a relatively untapped 

“gold mine” of information for environmental managers. The occurrence of a regime shift in the 

ocean climate in the North Pacific (PDO) in the past two decades provides a unique opportunity 

to determine whether and how various components of the biota have responded to this natural 

perturbation. Data from long-term monitoring programs not only indicate the current state and 

recent history of the biota, they can reveal much about the ecological structure of various coastal 

ecosystems, including the dynamical behavior and regulation of different food webs. Such 

knowledge provides managers with better understanding and enhanced predictive ability 

regarding the potential impacts to these ecosystems from other potential sources of disturbance. 

Further, analyses of existing data sets can expose whether and how our ability to estimate or 

interpret responses of the biota may be constrained by present monitoring practices. 

OBJECTIVES: Our MMS-UC CMI funded research encompassed two separate objectives: (1) 

the analysis and synthesis of existing monitoring data for long-term trends in the biota of the 

Southern California Bight and (2) the continued annual surveys of subtidal reef communities at 

Santa Cruz Island.

DESCRIPTION: We initially obtained data from 5 separate monitoring programs enumerating 

the flora and fauna of southern California nearshore marine communities in three different 

ecological systems, subtidal rocky reef, kelp bed, and open ocean/pelagic, between 1977 and 

2006. These datasets included the CalCOFI monitoring program, King Harbor monitoring data 

collected by John Stephens Jr., Occidental College, Southern California Edison NPDES 

monitoring data for the San Onofre Nuclear Generating Station and the Huntington Beach, 

Redondo Beach and Ormond Beach Steam Electrical Generating Stations, National Park Service 

Kelp Forest Monitoring Program data for the northern Channel Islands, and data collected by 

Russell Schmitt and Sally Holbrook, University of California, Santa Barbara as part of their 

ongoing monitoring of subtidal communities around Santa Cruz Island. Subsequent to our initial 

analyses, we also obtained data collected by the National Marine Fisheries Services during their 

triennial surveys of west coast groundfishes. This last dataset covered roughly the same time 

period as our original datasets, 1977-2001, but concentrated on fish species inhabiting the deeper 

waters of the continental shelf (55-500m) along the west coast of the United States from 

Monterey Bay, California to Alaska. 

Data were standardized between studies by re-expressing data on population densities as the 

percent change in initial population density over the time period 1977 through 1999-2000 and 

then again over the time period 1999-2000 through 2005-2006. Organisms within a given 

community were assigned to one of four trophic categories, primary producer, primary, 

secondary, or tertiary consumer, mode of reproduction, extent of geographic range, association 

with benthic or pelagic food webs, and habitat based on published life history information. 

Time-series analyses were performed on these data sets to describe temporal trends and explore 

the timing and magnitude of the observed changes. 
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STUDY RESULTS: (1) The analysis and synthesis of existing monitoring data for long-term 

trends in the biota of the Southern California Bight: 

Trends in population abundances following the regime shift of the PDO to a warm water phase in 

1977 show consistent declines in all three ecological systems, subtidal rocky reef, kelp bed, and 

open ocean/pelagic, between 1977 and 2001. Within each system examined, trends for each 

component trophic level showed approximately the same magnitude of decline. This pattern 

held across spatial scales ranging from a single island (Santa Cruz Island) within the northern 

Channel Islands group to the entire Southern California Bight suggesting genuine regional 

declines in abundances rather than a redistribution of individuals in response to changing 

environmental conditions. Also interesting is the fact that data collected using extremely 

different methodologies, e.g., coastal power plant impingement studies versus diver visual 

surveys, provide similar estimates of the magnitudes of these declines. Beginning in 2001 and 

following a reversal in the PDO to a cold water phase, some of these species, e.g., foliose algae, 

mesocrustaceans and surfperches, have begun to increase in abundance. 

While observed declines in fishes inhabiting open ocean/pelagic communities occurred almost 

simultaneously with declines in pelagic zooplankton populations, declines in fishes associated 

with nearshore subtidal rocky reefs and kelp beds lagged one to two years and declines in fishes 

associated with soft bottom habitats lagged two to three years behind declining zooplankton 

populations. These patterns are consistent with an explanation that a regional decline in 

productivity was responsible for the regional declines observed in fish stocks within the southern 

California Bight. Differences in response times probably represent the effects of species being 

longer lived in rocky reef and kelp bed communities when compared with species in 

pelagic/open water communities, i.e., storage effects. Comparisons with changes in the 

population abundances of deeper water species indicated that even though many species, most 

notably several species of rockfishes, exhibited declines consistent with those observed in 

nearshore fish communities, certain species, particularly flatfishes, actually increased in 

abundance during the period 1977-2001. 

(2) The continued annual surveys of subtidal reef communities at Santa Cruz Island: 

Our detailed examinations of a simple food web indicated that for two species of viviparous 

surchperches examined (black surfperch Embiotoca jacksoni; striped surfperch E. lateralis), 

recruitment of new individuals varied comparatively little through time on some reefs while it 

fluctuated substantially on others. These fishes harvest invertebrate prey from specific benthic 

foraging microhabitats (algal turf for black surfperch; the red alga Gelidium robustum for striped 

surfperch), and these microhabitats showed a range in dynamics among the reefs examined over 

a 12 yr period. Interannual fluctuations in foraging microhabitat were a strong predictor of the 

extent to which the abundance of young-of-year surfperches fluctuated. However, the foraging 

microhabitat for black surfperch (algal turf) on a reef fluctuated independently of that for striped 

surfperch (Gelidium). As a consequence, the extent to which the abundance of young of one 

surfperch varied on a given reef was unrelated to that of its congener. These data show that the 

magnitude of temporal variation in year-class strength of reef-associated fishes was related to the 

magnitude of variation in the forage base, reefs in close proximity can show a range in resource 
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dynamics that can affect reproductive output, and the reproductive output of even closely-related 

species can fluctuate independently on the same reef. 

SIGNIFICANT CONCLUSIONS: A primary goal of environmental assessments is to quantify 

trends in species responses following a perturbation. Evaluation or predictions of the effects of 

anthropogenic perturbations typically are made based upon the observed or hypothesized 

magnitude and direction of these trends. To be valid, however, trends observed to occur at small 

spatial scales, e.g., around an offshore oil production platform, must be placed within a larger 

regional context. In the case of predicted trends, these changes should reflect not only the 

hypothesized effects due to the perturbation, but also those effects likely to occur as a 

consequence of unrelated, natural changes in regional environmental conditions. Studies 

examining long-term or large scale spatial or temporal gradients in productivity provide both a 

regional context within which observed trends may be placed and an opportunity to explore 

responses of food webs to environmental perturbations. 

STUDY PRODUCTS: 

Published works: 

Brooks, A.J., R. J. Schmitt and S. J. Holbrook. 2002. Declines in regional fish populations: 

have different species responded similarly to environmental change? Marine and Freshwater 

Research 53(2):189-198. 

Schmitt, R.J. and S.J. Holbrook. 2006. Predicting the magnitude of temporal variation in youngof-year class strength of surfperch (Teleostei: Embiotocidae). Raffles Bulletin of Zoology. 

In Press. 

Holbrook, S.J., A.J. Brooks and R.J. Schmitt. Temporal variation in temperate reef assemblages: 

have trophic levels responded similarly to environmental change? To be submitted 

December, 2006. 

Presentations: 

Brooks, A.J., R.J. Schmitt and S.J. Holbrook. “Population Trends and Trophic Dynamics, the 

Use of Long-term Datasets.” 5th Temperate Reef Symposium, Capetown, S.A., January, 

2000. 

Brooks, A.J., R.J. Schmitt and S.J. Holbrook. “Population Trends and Trophic Dynamics, the 

Use of Long-term Datasets.” American Society for Ichthyology and Herpetology, La Paz, 

Mexico, June, 2000. 

Brooks, A.J. “Declines in Regional Fish Populations: Species Responses to Environmental 

Change and the Nature of Community Organization.” Western Society of Naturalists, 

Ventura, CA, November 2001. 

Brooks, A.J. “Declines in Rocky Reef Fish Populations: Have Different Species Responded 

Similarly to Environmental Change.” Southern California Academy of Sciences, Claremont, 

CA, June, 2002. 
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Brooks, A.J., H.S. Lenihan and S. Lester. “Temporal Trends in Shallow Nearshore and Deeper 

Continental Shelf Fishes Since 1977: Do Similar Responses Suggest a Common Mechanism 

Behind Observed Declines?” Southern California Academy of Sciences, Northridge, CA, 

May 2003. 

Brooks, A.J., R.J. Schmitt and S.J. Holbrook. “Population Trends and Trophic Dynamics – 

What Can Be Learned from Long-term Monitoring.” The Nature Conservancy, Santa 

Barbara, CA, October, 2003. 

Schmitt, R.J. and S.J. Holbrook. “Predicting the magnitude of temporal variation in youngof-year class strength of surfperch (Teleostei: Embiotocidae).” 7th Indo-Pacific Fish 

Conference, Taipei, Taiwan, May, 2005.