This study took place in the Santa Barbara channel region of southern California, USA. The Santa Barbara channel is a well-known biogeographic transition zone and nearshore rocky reefs and kelp forests are home to many important commercial and recreationally fished species. In particular, rockfishes (genus Sebastes) are long-lived, piscivorous reef fishes that are important predators and are both commercially and recreationally fished. Kelp bass (Paralabrax clathratus), another important fish predator makes up a major sport fishery in southern CA. Finally, CA sheephead (Semicossyphus pulcher) are predators on grazing urchins and have been shown to exert top down control on kelp forests in the area (Hamilton and Caselle, 2015). They also were the subject of an intense commercial live-fish fishery that peaked in the 1990s and are recreationally fished as well. The stock of these shallow dwelling, nearshore species in the Santa Barbara Channel would be difficult to estimate with existing data as 1) the monitoring programs that enumerate them currently focus on a subset of habitat types: predominantly large, contiguous and often high-relief rocky reefs that represent only the high-end of density and biomass ranges, and 2) the landings of these shallow nearshore species targeted in this study are largely from recreational fisheries so their numbers either go un-recorded or are recorded at very course spatial scales that would not enable species-habitat associations to be made. The objective of this study was to integrate seascape scale data (geologic and biologic) with patterns of fish community structure and abundance across a variety of habitat types. The fish data collection employed a random, stratified sampling design, which allowed statistical extrapolation to region wide metrics of abundance (biomass). While this study took place at a spatial scale that was smaller (in both geography and depth) than the species range of most of the surveyed fishes, it represents a first attempt at predicting region-wide biomass for important fishes using seascape level predictive models in southern California. Substrate was classified from multibeam sonar using the method of Cochrane (2008) for this study. Seafloor character derived from multibeam sonar data is available for the mainland coast within the study area from the California State Waters Mapping Program (Johnson and others, 2012; Johnson nad others, 2013a; Johnson and others, 2013b; Johnson and others, 2013c). The number of substrate classes was reduced because rugosity could not be derived for all areas due to the lack of bathymetry data for other data sets used in the study. Substrate was classified from sidescan sonar data using the method of Cochrane and Lafferty (2002) for this study. Sea floor character derived from towed sidescan sonar data is available for the mainland coast within the study area from USGS online publications (Cochrane and others, 2003; Cochrane and others, 2005). The number of substrate classes was reduced because rugosity could not be derived for all areas due to the lack of bathymetry data for other data sets used in the study. Seafloor character was derived from interpretations of lidar data available for the mainland coast within the study area from the California State Waters Mapping Program (Johnson and others, 2012; Johnson nad others, 2013a; Johnson and others, 2013b; Johnson and others, 2013c). The number of substrate classes was reduced because rugosity could not be derived for all areas. Sea floor character was derived from interpretations of air photo derived kelp distribution data available for the Santa Cruz Island (Kushner and others, 2013). The number of substrate classes was reduced because rugosity could not be derived for all areas.
References Cited:
Cochrane, G.R., Nasby, N.M., Reid, J.A., Waltenberger, B., and Lee, K.M., 2003, Nearshore benthic habitat GIS for the Channel Islands National Marine Sanctuary and Southern California State Fisheries Reserves, Volume 1: U.S. Geological Survey Open-File Report 03-85, http://pubs.usgs.gov/of/2003/0085/.
Cochrane, G.R., and Lafferty, K.D., 2002, Use of acoustic classification of sidescan sonar data for mapping benthic habitat in the Northern Channel Islands, California: Continental Shelf Research, v. 22, p. 683-690.
Cochrane, G.R., Conrad, J.E., Reid, J.A., Fangman, S., and Golden, N., 2005, The nearshore benthic habitat GIS for the Channel Islands National Marine Sanctuary and Southern California State Fisheries Reserves, Volume II: U.S. Geological Survey, Open-File Report 2005-1170, http://pubs.usgs.gov/of/2005/1170/.
Cochrane, G.R., 2008, Video-supervised classification of sonar data for mapping seafloor habitat, in Reynolds, J.R., and Greene, H.G., eds., Marine habitat mapping technology for Alaska: Fairbanks, University of Alaska, Alaska Sea Grant College Program, p. 185-194, accessed April 5, 2011, at http://doc.nprb.org/web/research/research%20pubs/615_habitat_mapping_workshop/Individual%20Chapters%20High-Res/Ch13%20Cochrane.pdf.
Kushner D.J., Rassweiler, A., McLaughlin, J.P., and Lafferty, K.D., 2013, A multi-decade time series of kelp forest community structure at the California channel islands: Ecology, v. 94, p. 2,655.
Johnson, S.Y., Dartnell, P., Cochrane, G.R., Golden, N.E., Phillips, E.L., Ritchie, A.C., Greene, H.G., Krigsman, L.M., Kvitek, R.G., Dieter, B.E., Endris, C.A., Seitz, G.G., Sliter, R.W., Erdey, M.E., Gutierrez, C.I., Wong, F.L., Yoklavich, M.M., Draut, A.E., Hart, P.E., and Conrad, J.E. (S.Y. Johnson and S.A. Cochran, eds.), 2013a, California State Waters Map Series—Offshore of Santa Barbara, California: U.S. Geological Survey Scientific Investigations Map 3281, 45 p., 11 sheets, scale 1:24,000, https://dx.doi.org/10.3133/sim3281/.
Johnson, S.Y., Dartnell, P., Cochrane, G.R., Golden, N.E., Phillips, E.L., Ritchie, A.C., Kvitek, R.G., Greene, H.G., Endris, C.A., Seitz, G.G., Sliter, R.W., Erdey, M.D., Wong, F.L., Gutierrez, C.I., Krigsman, L.M., Draut, A.E., and Hart, P.E. (S.Y. Johnson and S.A. Cochran, eds.), 2013b, California State Waters Map Series—Offshore of Carpinteria, California: U.S. Geological Survey Scientific Investigations Map 3261, 42 p., 10 sheets, scale 1:24,000, https://pubs.usgs.gov/sim/3261/.
Johnson, S.Y., Dartnell, P., Cochrane, G.R., Golden, N.E., Phillips, E.L., Ritchie, A.C., Kvitek, R.G., Greene, H.G., Krigsman, L.M., Endris, C.A., Clahan, K.B., Sliter, R.W., Wong, F.L., Yoklavich, M.M., and Normark, W.R. (S.Y. Johnson, ed.), 2012, California State Waters Map Series—Hueneme Canyon and Vicinity, California: U.S. Geological Survey Scientific Investigations Map 3225, 41 p., 12 sheets, scale 1:24,000, https://pubs.usgs.gov/sim/3225/.
Johnson, S.Y., Dartnell, P., Cochrane, G.R., Golden, N.E., Phillips, E.L., Ritchie, A.C., Kvitek, R.G., Greene, H.G., Krigsman, L.M., Endris, C.A., Seitz, G.G., Gutierrez, C.I., Sliter, R.W., Erdey, M.D., Wong, F.L., Yoklavich, M.M., Draut, A.E., and Hart, P.E. (S.Y. Johnson and S.A. Cochran, eds.), 2013c, California State Waters Map Series—Offshore of Ventura, California: U.S. Geological Survey Scientific Investigations Map 3254, pamphlet 42 p., 11 sheets, scale 1:24,000, https://pubs.usgs.gov/sim/3254/.
