The ecosystem impacts of kelp forest habitat restoration, including important fishery species

Principal Investigators:

• Daniel Pondella, Vantuna Research Group, Occidental College
• Tom Ford, Santa Monica Bay Restoration Foundation
• Jeremy Claisse, Vantuna Research Group, Occidental College
• Jonathan Williams, Vantuna Research Group, Occidental College
• Laurel Fink, Vantuna Research Group, Occidental College 

Results

This research has shown that kelp forest restoration is possible in barrens when purple urchins are selectively removed. These results provide support for the large-scale habitat restoration that is now being performed along the Palos Verdes Peninsula in cooperation with other local non-profits and commercial fishermen.
(Photo courtesy of Tom Boyd)

Project Overview

Kelp forest ecosystems are iconic and productive features along the coast of California with services that span a wide array of consumptive (e.g., commercial and recreational fishing) and non-consumptive (e.g., tourism, scuba diving and diminishing coastal erosion) uses. Giant Kelp (Macrocystis pyrifera) forms a 3-dimensional habitat supporting roughly 716 species.  These habitats support fisheries for a number of invertebrates (e.g., sea urchins, spiny lobster) and finfish [e.g., Kelp Bass (Paralabrax clathratus), California Sheephead (Semicossyphus pulcher) (CDFG 2010), in addition to Giant Kelp being harvested itself for a variety of human uses. Through both fishing activities and nonconsumptive uses, California’s ocean-related activities support the state economy by bringing in 40+ billion dollars a year in revenue (Kildow and Colgan 2005).

California kelp forests have been severely depleted by human activity, mainly overfishing, which has caused several ecological shifts within the habitat, primarily attributed to the loss of key predator species (Dayton et al. 1998; Tegner and Dayton 2000). In a balanced ecosystem, sea urchin consumption of kelp is limited primarily by predation on urchins (Dayton 1985; Edwards 2004). Two species that historically controlled sea urchin populations in the SCB: the California Spiny Lobster and California Sheephead, are under significant fishing pressure, while a third species, the Southern Sea Otter, is listed as threatened under the Federal Endangered Species Act.  These factors simultaneously reduces the size and number of individuals able to successfully predate sea urchins (Cowen 1983; CDFG 2001; Lafferty 2004; California Fisheries Fund 2009).

To enable the recovery of historical kelp forests in Santa Monica Bay, the Santa Monica Bay “Kelp Project” has engaged in sea urchin relocation to reduce the density of urchins on shallow rocky reefs since 1997. The Kelp Project has demonstrated that reducing urchin density from as high as 100 sea urchins per square meter to < 2 sea urchins per square meter enabled the natural development of Giant Kelp and other macroalgae at restoration areas in Malibu and Palos Verdes.

The Ecosystem Impacts of Kelp Forest Habitat Restoration study will provide a critical evaluation of the potential for kelp restoration to improve ecosystem structure and function, including some of the most important recreational and commercial fishery species in Southern California. These results will contribute to the development of comprehensive adaptive management strategies to increase the resilience of kelp forest ecosystems to the stressors associated with urban environments (e.g. overfishing, sedimentation and runoff events) and global phenomena which may be associated with climate change (e.g. frequency of ENSO and large storm events). Additionally, establishing the impacts that urchin barrens have on common ecosystem attributes will directly relate to the evaluation of the recently established network of MPAs in the region and the associated development of long-term adaptive management plans. Results will assist resource managers, politicians and other important stakeholders in better calibrating their temporal expectations for restoration efforts.

Literature Cited Above

California Fisheries Fund (2009) California Fisheries Atlas - California Spiny Lobster. http://www.californiafisheriesfund.org/reso_atlas_lobs.html

CDFG (2001) California’s living marine resources: A status report. California Department of Fish and Game. http://www.dfg.ca.gov/marine/status/status2001.asp

Dayton PK (1985) Ecology of Kelp Communities. Annual Review of Ecology and Systematics 16: 215-245

Dayton PK, Tegner MJ, Edwards PB, Riser KL (1998) Sliding baselines, ghosts, and reduced expectations in kelp forest communties. Ecological Applications 8: 309-322

Edwards M (2004) Estimating scale-dependency in disturbance impacts: El Niños and giant kelp forests in the northeast Pacific. Oecologia 138: 436-447

Kildow J, Colgan CS (2005) California's ocean ecology. Report to the Resources Agency, State of California. Prepared by The National Ocean Economics Program. 167 pp. http://resources.ca.gov/press_documents/CA_Ocean_Econ_Report.pdf

Lafferty KD (2004) Fishing for lobsters indirectly increases epidemics in Sea Urchins. Ecological Applications 14: 1566-1573

Author Publications

• Morphometric Relationships of Marine Fishes Common to Central California and the Southern California Bight. 
• The ichthyoplankton of King Harbor, Redondo Beach, California 1974-2009.  California Cooperative Oceanic Fisheries Investigations Report 
• Kelp forest habitat restoration has the potential to increase sea urchin gonad biomass