Santa Cruz Island Reserve

13 Aug, 05 AM - 18 Aug, 03 AM

Sweeping changes have taken place in the marine biota off southern California during the last 35 years, including changes in the distribution and abundance of fishes, invertebrates, and kelp. I propose to extend a long-term study of nearshore fish communities off Santa Cruz Island, California, further documenting changes in the assemblage and evaluating the effects of ocean climate and kelp loss on nearshore fishes of the southern California Bight. The objective of this study is to evaluate long-term changes in southern California fish populations by extending a long-term data series collected by Ebeling et al at Santa Cruz Island in the early 1970s. This data set complements that of Stephens and colleagues because it represents a more northerly portion of the southern California Bight. Two of the researchers involved in these early Santa Cruz Island censuses, Drs. Ralph Larson and William Alevizon, repeated the surveys in August 1996. This later work showed the effects of ocean warming and the loss of kelp at some sites, but data were only collected in one year, making it difficult to assess interannual variation. In addition, short-term climatic changes occurred after this later survey. An El Ni?o event affected the eastern Pacific in 1997-98, followed by a La Ni?a in 1999. Current oceanographic data indicate a possible return to cooler ocean conditions, but there appears to be little recovery of kelp off Santa Cruz Island. If funded, this study will provide additional data that are necessary to separate the effects of climate, kelp loss and other factors such as fisheries exploitation on southern California nearshore fish communities. The goals of this study are to (a) continue to document changes in the nearshore fish assemblage off Santa Cruz Island, comparing species composition and abundance to the early 1970s and to 1996, (b) attempt to evaluate the effects of climate and other factors on the fish assemblage by comparing changes in species with different biogeographic affinities, habitat and feeding niches, and exploitation in fisheries, and (c) attempt to separate the effects of climate change per se and the effects of kelp loss on nearshore fishes by comparing species composition and abundance among sites at Santa Cruz Island with and without kelp forests,. In the 1996 survey, Larson and Alevizon found a substantial shift in species composition toward species with more southerly biogeographic affinities, and found an additional effect of kelp loss. Sampling for the proposed study will be conducted in August - September of 2004 and 2005 at five sites on the north side of Santa Cruz Island. Three sites were sampled by Ebeling et al.2 in their 1971-1974 sampling series. Two other sites, each with kelp canopies present, were added in 1996 because the kelp canopy at the original three sites had disappeared. Comparing sites with and without kelp in 1996 allowed an evaluation of the effects of climate alone vs. kelp loss on the fish assemblage. Sampling in August-September will take advantage of predictably good visibility and sea conditions, and will be consistent with previous surveys. Sampling in both 2004 and 2005 will allow evaluation of interannual variability. Funding permitting, I also propose to conduct replicate sampling at some sites within years (one set during August and another during September) to evaluate within-year sampling variability. Censuses will be conducted in the same manner as the earlier surveys, using SCUBA and underwater videography. Dr. Ralph Larson will provide training in the survey method, and will be present for each year?s surveys to ensure consistency of methods and locations. Fish will be sampled and habitat characteristics observed by means of video transects. Divers will swim 2.5 minute long transects at constant depth while panning a digital video camera to record fishes. Both canopy and bottom habitat will be sampled in this manner, with approximately 20-25 transects per site on the bottom and 15 transects per site in the canopy. Bottom transects will cover a range of depths and distances from shore, and canopy transects will be made at depths of 2-3 m, just below the mat of floating kelp fronds (for those sites with kelp present). Canopy transects will be made from the shoreward margin of the site to the outer margin of the canopy (or where the outer margin would have been had the kelp canopy been present). Additional data to be collected for each transect will include depth of filming, depth of bottom, underwater visibility, temperature and depth of thermocline. Fish will be identified and counted in the laboratory, and environmental characteristics such as bottom relief and kelp density will be scored. Once all videos are analyzed and raw data are collected, multivariate statistical techniques will be used to evaluate community changes and interannual variation in community composition. Further statistical analysis will be employed to compare fish counts among years and sites. In addition, I will compare the results of the 1996, 2204, and 2005 surveys to the results of the Channel Island National Parks surveys (Davis et al.6). They sample one of the Ebeling et al. sites, and another in the in the vicinity of my sites. This will provide an independent verification of the species composition I record, although the Park counts only a subset of the species.

Visit #4869 @Santa Cruz Island Reserve

Approved

Under Project # 3881 | Research

Temporal variation in fish communities off Santa Cruz Island

graduate_student - San Francisco State University (CSU)

Reservation Members(s)

Michelle Graves Aug 13 - 18, 2004 (6 days)
Group of 2 Faculty Aug 13 - 18, 2004 (6 days)

Reserve Resources(s) | Create Invoice

Dorm 3 Aug 13 - 18, 2004