MOSER ET AL.: NEARSHORE FISH LARVAE CalCOFl Rep., Vol. 42, 2001 THE CALCOFI ICHTHYOPLANKTON TIME SERIES: POTENTIAL CONTRIBUTIONS TO THE MANAGEMENT OF ROCKY-SHORE FISHES H. GEOFFREY MOSER, RICHAKII L. CHARTER, PAUL E. SMITH, JOHN L. BUTLER, WILLIAM WATSON, IIAVII) A. AMUROSE KEVIN T. HILL ELAINE M. SANI)KNOI’, SHARON R. CHARTER Southwest Fishenes Science Center C~iliforiii.i1)rpartment of Fish and Cmir Southwect Fisheries Science Crnter N~ion~ilMaine Fisheries Service South\vest Fisliener Science Center Nmonal Mdrine Fi\henes Srrvicc P.0.Box 271 8004 La Jolla Shores I )rive P.0.Box 271 La Jolla, Californi~92038 La Jolla, Califoriii.i 92037 La Joll~,Califorilia 02038 (;cofFMoser~v,noaa.g,v ABSTRACT the past decade, the growing popularity of the live-fish Harvest of nearshore fishes off California, particularly restaurant trade has produced a highly focused nearshore species in the recently expanded live-fish fishery, has im- fishery that targets rockfishes of the subgenus Ptevopodus pacted inany of these stocks. Important taxa are cabezon, (e.g., copper, grass, gopher, brown, and kelp rockfishes) sheephead, lingcod, greenlings, and the rockfishes in- and other associated shallow-water reef fishes (e.g., cluded in the subgenus Pteropodus. Life-history infor- cabezon, greenlings, lingcod, sheephead). The impact mation and fishery-independent abundance indices are of this fishery is superimposed on long-standing coin- badly needed for the development of management strate- mercial and recreational fisheries for these species. Harvest gies for these stocks. The California Cooperative Oceanic of these nearshore stocks has progressed at a rate that Fisheries Investigations (CalCOFI) surveys can provide may place them in the same status as those in deeper- indices of abundance for larval stages of many species, water habitats (Pattison and Vejar 2000). Other key species including cabezon, sheephead, kelp and sand basses, ling- in the nearshore environment are kelp and barred sand cod, and several species of rockfishes. This paper pre- bass (Paralabmx clatlzratrrs and I! nebidlifer), nonniarket sents, as examples, data on the distribution and abundance species that have been mainstays of private and coin- of cabezon, sheephead, and Paralahrax (kelp and sand niercial sport fisheries in southern California. bass) larvae in the Southern California Bight region and The state of California has new responsibilities to compares these with data froni other nearshore ichthy- manage and conserve nearshore fish species and their oplankton surveys conducted in the region. Trends in habitats. Among the most valuable assets for such stock landings for cabezon generally match trends in CalCOFI assessments are long-term fishery-independent indices larval indices, supporting use of the larval catch data as that originate well before the expansion of the fisheries fishery-independent abundance indices. The principal and encompass the major shifts in ocean cliniate associ- recommendation for improving nearshore larval time se- ated with the history of the fishery. The 51-year-long ries is to reestablish plankton tow stations on CalCOFI ichthyoplankton time series froni the California Coop- survey cruises off central California, where standard erative Oceanic Fisheries Investigations (CalCOFI) sur- plankton tows have not been taken since the survey area veys provides such indices of abundance for larval stages was reduced in 1985. of many species. Although a primary objective of CalCOFI was to de- INTRODUCTION termine the cause for the decline of the Pacific sardine The decline of West Coast rockfish (Sebustes) popu- (Surdimp sap~x)in the middle of the last century, lations over the past several decades has left many stocks CalCOFI data have been central to our understanding at dangerously low levels (Ralston 1998). Nowhere is of population processes of a large array of marine or- this more evident than in the California trawl fishery, ganisms, from phytoplankton to mammals. CalCOFI has once dominated by bocaccio (S. pauiispiriis), a species played an important role in the successful management that now is in rebuilding status (Ralston et al. 1996; of northern anchovy (Smith 1972; Lasker 1985) and MacCall et al. 1999). The contribution of recreational Pacific sardine, which has rebounded dramatically during fisheries to the present condition of rockfish stocks is the past 20 years (Wolf 1992; Hill et al. 1999). Although demonstrated by the severely depleted cowcod (S. levis), CalCOFI surveys were designed to encompass the wide- a species highly prized by both coniniercial and recre- spread open-ocean spawning of Pacific sardine, it is a ational fisheries. It, too, is in rebuilding status and has surprising fact that trends in larval abundance of nearshore become a foundation species for new protective regula- species in CalCOFI collections usually track changes in tions in rockfish nianageinent (Butler et al. 1999). During abundance of adults quite well, even when a species is greatly undersanipled due to the offshore emphasis of [Manuscript received 15 February 2001 .] the CalCOFI sampling pattern (Ralston et al. 1996; 112 MOSER ET AL.: NEARSHORE FISH LARVAE CalCOFl Rep., Vol. 42, 2001 Butler et al. 1999). In addition to indices of larval abun- with procedures used in Moser et al. 2001. For these dance, the CalCOFI ichthyoplankton time series can calculations, station 60 on each of the current CalCOFI provide valuable information on spawning seasons and lines defines the outer margin of the continental bor- temperatures as well as larval dispersion and mortality. derland and the Southern California Bight region; the The objectives of this paper are to present current SCB region includes line 77 (fig. l), even though that and potential contributions of the CalCOFI ichthy- line is north of Point Conception. Station 70 was used oplankton time series to nearshore fish management and as the outer boundary for calculating occurrence of ecology, and to compare CalCOFI larval indices with cabezon larvae because they were distributed farther off- other available larval fish time series for this region. We shore than sheephead and Purulubrux spp. larvae (Moser examine trends in larval abundance of cabezon and sheep- et al. 2001). head, two important species currently under exploita- The basic plankton tow niethodology for oblique tows tion by the live-fish fishery, and kelp and barred sand and sample handling were consistent throughout the bass, important nonmarket sport fishes, and then coin- tinie series (Kramer et al. 1972; Smith and Richardson pare these with trends in the Southern California Bight 1977; Moser et al. 1993, 1994). Neuston tows have been (SCB) time series of the Natural History Museum of taken at each station on all CalCOFI survey cruises since Los Angeles County (LACM) and MEC Analytical 1978 with a manta net (Brown and Cheng 1981 ; Moser, Systems (MEC), and with trends at Diablo Canyon off Charter, Reilly et al. 2000). Hauls were made at a ship central California, monitored by Tenera Environmental speed of 1.0-2.0 knots for 15 minutes, except in 1978 Services (Tenera). Lastly, we consider how nearshore sur- when tow duration was 3 minutes. The manta net time veys could be augmented to produce more useful in- series for the species in this paper includes 4,733 tows dices, and we discuss more costly methodologies, such taken on 88 cruises. as larval and egg production estimation techniques, that Data were available froni LACM and MEC surveys, could provide &rect nieasures of absolute fish abundance. conducted over shelf areas of the SCB in the years be- tween 1978 and 1986, and from Tenera surveys con- METHODS ducted at the Diablo Canyon power plant in central Initially, CalCOFI conducted monthly surveys over California from 1990 to the present. With minor ex- a large portion of the California Current region froni ceptions, gear and tow methodology used by LACM, northern California to the tip of Baja California, MEC, and Tenera were similar to those of CalCOFI. Mexico-the spawning range of the Pacific sardine dur- The MEC oblique tows were taken in 30-second steps, ing the first decade of the CalCOFI program (see sur- but equivalent volumes of water were filtered for all por- vey map on the inside back cover of this volume). Areal tions of the water column. Surface tows taken by Tenera and temporal coverage contracted over subsequent within the intake bay at Diablo Canyon employed a 0.5 decades; since 1985, the surveys have been limited to a m ring net towed just below the surface on the sanie pattern of 66 stations in the SCB region (Hewitt 1988; transect on a weekly basis.' Moser et al. 1993, 1994). The Southern California Bight has been the most frequently occupied region of the RESULTS overall CalCOFI survey pattern. The oblique net tow time series for the species treated Demersal Habitats in the SCB in this paper comprises 11,924 tows taken on 243 cruises The inner third of the present CalCOFI survey pat- during 1951-2000 within the boundaries of the present tern overlies the continental borderland of southern CalCOFI survey. These include all standard oblique California, a region of complex topography that includes CalCOFI survey tows taken since 1985, when occu- the mainland continental shelf and slope, deep-water pancy of the present pattern was initiated. Oblique tows basins, and numerous islands and banks and their shelves used prior to 1985 are a subset from the wider-ranging and slopes (fig. 1). The islands and banks extend coastal CalCOFI surveys (Hewitt 1988; Moser et al. 1993, 1994). habitats >lo0 nmi offihore, and the basins provide deep- On surveys prior to 1985 in the Southern California water habitats and zoogeographic refugia for many mid- Bight, nearshore stations did not always correspond to water species. Point Conception fornis the zoogeographic the exact positions of the 66 nominal stations used on boundary between the Oregonian shore fauna to the surveys since 1985.