Regional and Seasonal Patterns of Epipelagic Fish Assemblages from the Central California Current

Regional and seasonal patterns of epipelagic fish assemblages from the central California Current Item Type article Authors Harding, Jeffrey A.; Ammann, Arnold J.; MacFarlane, R. Bruce Download date 23/09/2021 09:55:22 Link to Item http://hdl.handle.net/1834/25356 261 Abstract—The coastal Pacific Ocean Regional and seasonal patterns off northern and central California encompasses the strongest seasonal of epipelagic fish assemblages upwelling zone in the California Cur- rent ecosystem. Headlands and bays from the central California Current here generate complex circulation features and confer unusual oceano- Jeffrey A. Harding (contact author) graphic complexity. We sampled the coastal epipelagic fish community of Arnold J. Ammann this region with a surface trawl in the R. Bruce MacFarlane summer and fall of 2000–05 to assess patterns of spatial and temporal com- Email address for contact author: [email protected] munity structure. Fifty-three species Santa Cruz Laboratory of fish were captured in 218 hauls at Southwest Fisheries Science Center 34 fixed stations, with clupeiform spe- National Marine Fisheries Service, NOAA cies dominating. To examine spatial 110 Shaffer Road patterns, samples were grouped by Santa Cruz, California 95060 location relative to a prominent head- land at Point Reyes and the resulting two regions, north coast and Gulf of the Farallones, were plotted by using nonmetric multidimensional scaling. Seasonal and interannual patterns Twenty five percent of marine fish- and various agencies and institutions were also examined, and representa- eries catch comes from regions that are actively collecting the biological tive species were identified for each encompass a mere five percent of the and environmental data that will be distinct community. Seven oceano- world’s oceans: within the Benguela, needed to bring these plans to action graphic variables measured concur- California, Canary, Peru, and Soma- (Ecosystem Plan Development Team2). rently with trawling were plotted by lia currents (Jennings et al., 2001). The high productivity of the Cali- principal components analysis and tested for correlation with biotic Management of these highly produc- fornia Current (CC) is primarily the patterns. We found significant dif- tive coastal upwelling ecosystems result of local wind-driven season- ferences in community structure has historically been based on single al upwelling and the interaction of by region, year, and season, but no species assessments, although the alongshore currents with prominent interaction among main effects. Sig- science informing management has coastal features such as capes, head- nificant differences in oceanographic long recognized the limited power of lands, and bays that advect upwelled conditions mirrored the biotic pat- this approach. After the dramatic and water masses into complex patterns terns, and a match between biotic and unexpected collapse of several major of offshore filaments and coastal re- hydrographic structure was detected. small-pelagic fisheries worldwide circa tentive eddies (Davis, 1985; Gan and Dissimilarity between assemblages 1945–72, scientists began to advocate Allen, 2002). The zone of maximum was mostly the result of differences in abundance and frequency of occur- the need to incorporate climate, ocean spring and summer wind stress and rence of about twelve common spe- conditions, and other sources of uncer- wind-driven upwelling occurs be- cies. Community patterns were best tainty into management (Fréon et al., tween Cape Blanco in southern Or- described by a subset of hydrographic 2005; MacCall, 2009). In the last two egon (43°N) and Point Conception variables, including water depth, decades the momentum to achieve this in central California (34°N) (Nel- distance from shore, and any one of goal has increased, and some form of son, 1977). Headlands in this region several correlated variables associ- ecosystem-based management is now including Cape Mendocino, Point ated with upwelling intensity. Rather a stated policy objective of government Arena, Point Reyes, and Point Año than discrete communities with clear agencies in several nations (Link et Nuevo are the main locales of newly borders and distinct member species, al., 2002; Ecosystem Principles Advi- upwelled water. Bays located down- we found gradients in community 1 structure and identified stations with sory Panel ). Ecosystem manage- current act as retention zones where similar fish communities by region ment plans have now been proposed eddies form and trap aging upwelled and by proximity to features such as for most U.S. fisheries including the water (Paduan and Rosenfeld, 1996), the San Francisco Bay. U.S. west coast and large portions allowing concentrated phytoplankton of the California Current ecosystem, blooms to develop nearshore (Vander Manuscript submitted 7 May 2010. Manuscript accepted 18 March 2011. 1 Ecosystem Principles Advisory Panel. Fish. Bull. 109:261–281 (2011). 1999. Ecosystem-based fishery man- 2 Ecosystem Plan Development Team. agement. A report to Congress by the 2010. Ecosystem fishery management The views and opinions expressed National Marine Fisheries Service, 54 planning for U.S. west coast fisheries. A or implied in this article are those of the p. National Marine Fisheries Service, report to the Pacific Fisheries Manage- author (or authors) and do not necessarily Office of Science & Technology, 1315 ment Council, 35 p. Pacific Fisheries reflect the position of the National Marine East-West Highway, Silver Spring, MD Management Council, 7700 N.E. Ambas- Fisheries Service, NOAA. 20910. sador Pl., Ste. 101, Portland, OR 97220. 262 Fishery Bulletin 109(3) Woude et al., 2006). Blooms in this region often occur surveys of forage fishes and their associates, details of at cape-and-bay spatial scales and are ephemeral, typi- the spatial and temporal structure of their populations, cally lasting several days after an upwelling wind event and measurement of the oceanographic variables that (Largier et al., 2006). drive local abundance (Field et al., 2006; Samhouri Coastal topographical features also affect the dis- et al., 2009). This area is also home to several large tribution of zooplankton and larval invertebrates in state and federal marine sanctuaries and is one of the this region (Ebert and Russell, 1988; Largier, 2004). primary testing grounds for Marine Protected Areas Localized differences in zooplankton density and com- (MPAs) in the United States. Although these MPAs munity structure have been measured across distances are designed primarily for the conservation of demersal of 10 km or less in the vicinity of headlands and their fish and invertebrates, knowledge of pelagic fish habitat upwelling shadows (Graham et al., 1992; Wing et al., and community structure could also be used to inform 1998; Mace and Morgan, 2006), and across-shelf varia- decisions on size and placement of MPAs (Reese and tion in zooplankton (Morgan et al., 2003) and ichthyo- Brodeur, 2006). plankton (Auth, 2008) community structure is well Our study covered a strip of coastal ocean run- described. A complex field of mesoscale eddies and ning north–south above the inner continental shelf fronts off coastal Oregon in the summer of 2000 cor- in a region of strong seasonal upwelling off northern related spatially with four or five different zooplank- and central California. The region encompasses sev- ton assemblages, and dynamic water-mass attributes eral prominent headlands and bays, a small group of influenced by recent strong upwelling and advection offshore islands, and the outflow of the largest river appear to be the principal factors driving horizontal in the state through the San Francisco Bay. Detailed planktonic distribution (Keister et al., 2009). Seasonal patterns of spatial and temporal community structure zooplankton shifts have been linked to intensity of up- of epipelagic fishes in this portion of the CC are un- welling and variation in the timing and delivery rate of described. The objectives of this study were 1) to test subarctic and subtropical water onto the shelf (Peterson for regional, seasonal, and interannual patterns of fish and Miller, 1977; Roesler and Chelton, 1987), and in- abundance in catch data from six years of summer and terannual patterns appear related to El Niño–South- fall surface trawl surveys; 2) to identify dominant spe- ern Oscillation (ENSO) events and other multiyear cies associated with patterns of community structure, climate cycles that impact the ocean on basin-scales and correlate biotic patterns to a suite of water proper- (Rebstock, 2003). The physical processes that promote ties that may be influencing fish distribution; and 3) to rapid growth and patchiness among plankton have provide a detailed baseline record of species abundance additional downcurrent trophic effects among krill, and distribution for the region, against which future fishes, seabirds, and marine mammals (Ainley, 1990; change may be measured, and to provide primary data Croll et al., 2005; Ware and Thomson, 2005; Jahncke for ecosystem-based management for the California et al., 2008). Current ecosystem. Assemblage patterns of epipelagic fishes in the CC are known mostly from studies in the northern portion. Orsi et al. (2007) summarized broad-scale species as- Materials and methods sociations from surface trawls in both the California and the Alaska Current, in a region spanning 1100 The study area encompassed a 185-km strip of coastal km of coastline and identified

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