Distribution of Pelagic Metamorphic-Stage Sanddabs

Abstract.-Upwelling and its as sociated offshore advection of surface Distribution of pelagic waters can affect the recruitment of nearshore organisms. Late-stage pelagic metamorphic-stage sanddabs Pacific and speckled sanddabs, Citha richthys sordidus and C. stigmaeus, were Citharichthys sordidus and collected with a midwater trawl off cen tral California during the spring and C. stigmaeus within areas of summer upwelling season. In both spe cies, otolith size increased linearly with upwelling off central California metamorphic development; standard length, however, increased asymptoti cally. Earlier stages ofboth species oc Keith M. Sakuma curred shallower in the water column, Tiburon Laboratory, Southwest Fisheries Science Center whereas later stages occurred deeper. National Marine Fisheries Service, NOM The deeper distribution oflater stages 3150 Paradise Drive. Tiburon. California 94920 may have been due to decreased buoy ancy as a resultofincreasedotolithsize and ossification of bony structures co Ralph J. Larson incident with metamorphosis. Earlier stages ofboth species were more abun Department of Biology, San Francisco State University dant offshore and less abundant in ar J600 Holloway Avenue, San Francisco, California 94132 eas of upwelling, whereas later stages were more abundant nearshore regard less ofupwelling. The difference in the horizontal distributions of early and late stages may have been passively driven by different currentpatterns as a Pacific and speckled sanddabs, Ci bathymetric distribution as settled result ofthe difference in vertical distri tharichthys sordidus and C. stig individuals (usuallyfound at depths butions between early and late stages. maeus, are abundant along the Pa of 40 m and less)(Rackowski and cific coast ofNorthAmerica (Miller Pikitch, 1989; Kramer, 1990). Both and Lea, 1976). In both species, species are widely distributed as spawningpeaks duringthe summer pelagic larvae (as far as 724 km off months butalso occurs at lower lev shore for Pacific sanddabs and 320 els during the remainder of the km offshore for speckled sanddabs) year; individuals may spawn more (Rackowski and Pikitch, 1989), but than once during a given season settled individuals occur within a (Arora, 1951; Ford, 1965; Goldberg somewhat more restricted coastal and Pham, 1987; Matarese et aI., region. 1989; Rackowski andPikitch, 1989). The existence oflate-stage Pacific Sanddabs have a long pelagic stage, and speckled sanddabs in midwater which may exceed 324 days in trawls conducted offcentral Califor speckled sanddabs and 271 days in nia by the National Marine Fisher Pacific sanddabs (Kendall, 1992; ies Service (NMFS) Tiburon Labo Brothers!), and settle ata relatively ratory (Wyllie-Echeverria et aI., large size (20 to greater than 39 mm 1990) provided an opportunity to standard length (SL) for Pacific examine ontogenetic changes in dis sanddabs and 24 to greater than 36 tribution associated with metamor mm for speckled sanddabs) (Ahl phosis and settlement ofthese two strom et aI., 1984; Matarese et aI., sanddabs. In this paper we investi 1989). Kramer (1990) noted that gated the vertical and horizontal flatfish with nearshore nurseries distribution of pelagic-stage sand had briefpelagic stages and settled dabs, with the general purpose of at small sizes, whereas those with elucidating the changes that take less restricted coastal nurseries had place at metamorphosis and settle longer pelagic stages and settled at ment. Because the NMFS collec larger sizes. Kramer (1990) placed tions were made during the spring sanddabs in the latter category; Manuscript accepted 27 February 1995. however, speckled sanddabs, in par 1 Brothers, E. B. EFS Consultants, Ithaca, Fishery Bulletin 93:516-529 (1995). ticular, have a somewhat restricted NY 14850. Personal commun., 1993. 516 Sakuma and Larson: Distribution of Citharichthys sordidus and C. stigmaeus 517 and summer upwelling season, when the associated not identified to species before 1987. Therefore, data offshore advection of surface waters can adversely were analyzed only from the 1987 through 1991 sur affect marine organisms with pelagic life stages veys. In addition to the May-June surveys in each (Parrish et aI., 1981; Bailey and Francis, 1985; year, samplingwas carried out inApril of1987, 1988, Roughgarden et aI., 19881, the effect ofupwelling on and 1990. Sanddabs were identified and enumer pelagic-stage sanddabs was also investigated. ated on board the research vessel at sea. In 1990 and 1991, samples were frozen after identification and enumeration and brought back to the labora Methods tory where standard length (SL) and stage ofmeta morphosis were additionally recorded for each speci Data collection men collected. Five metamorphic stages, based on the stagingsystem used by Pearcyet al. (1977), were Pelagic Pacific and speckled sanddabs were collected defined as follows: in conjunction with the annualjuvenile rockfish sur veys conducted by NMFS Tiburon Laboratory scien Stage 1 = left and right eyes positIoned sym tists aboard the National Oceanic and Atmospheric metrically on both sides ofhead; Administration (NOAA) research vessel David Starr Stage 2 = righteye hasbegun to move dorsally; Jordan. Standard stations extending from Point Stage 3 = upper edge ofright eye within close Reyes to Cypress Point (Fig. 1) were sampled with a proximity to the top ofthe right side 26 x 26 m modified Stauffer midwater trawl with a ofthe head; codend liner of 9.5-mm stretched mesh (Wyllie Stage 4 = right eye has begun to cross over to Echeverria et aI., 1990). Standardtrawling depth was the left side ofthe head; 30 m except at shallow-water stations where trawls Stage 5 = right eye completely crossed ov:er to were conducted at 10 m. At certain standard stations left side ofthe head. a series ofthree depth-stratified trawls (depths=lO m, 30 m, and 110 m) were conducted to determine bathymetric distributional patterns (Fig. 1). As time permitted, additional trawls, both standard depth and depth-stratified, were conducted at nonstandard stations. All 38 trawls were 15 minutes in duration and were completed between the hours of 2100 and 0600. Stations were sampled z during a 10-day "sweep" of the survey °......, area. Three replicate sweeps were com pleted from mid-May to mid-June of each year~ in some years one additional sweep was completed in earlyApril. CTD (conductivity, temperature, and depth) castswere made ateach trawl sta 37 tion to obtain temperature and salinity information at depth. Additional CTD casts were made during the day along SIaDdanI Depth tracklines interspersedbetweenthetrawl Deplh-Stralified station lines (Schwing et al., 1990). Sur- face temperature and salinity were also recorded continuously by a thermo- 124 123 122 salinometer aboard the vessel. CTD and thermosalinometer data were used to Longitude (oW) detennine therelationbetweenupwelling and the spatial distributions of the dif- Figure 1 ferent pelagic stages ofboth sanddabs. Location ofstandard trawling stations for Pacific and speckled sanddabs. Although the annualjuvenile rockfish Citharichthys sordidus and C. stigmaeus, collected during 1987-91. surveys began in 1983, sanddabs were 518 Fishery Bulletin 93(3). 1995 No stage-1 individuals were collected, probably be 1991, the April surveys alone, and the May-June cause their small size allowed them to pass through surveys alone. To determine changes in vertical dis. the net. tribution ~ith development, the paired comparisons To determine if metamorphic stage was a more were also carried out on each of the metamorphic useful character than SL in resolving spatial pat stages, by using data from the April and May-June terns, twenty individuals from each metamorphic surveys of1990 andfrom theMay-June surveyof1991. stage of each species were randomly selected from To determine the similarity ofhorizontal distribu the May to June survey of 1991, and their otoliths tions among metamorphic stages, Spearman rank were removed. The diameter of the largest otolith, correlation coefficients were calculatedfor the abun the sagitta, was measured with a compound micro dances of different stages over standard stations scope connected to a video camera, monitor, digitizer, during the 1990 and 1991 surveys. and computer. CTD salinity at the surface (average salinity at 3-5 m depth) and at the standard mid-depth of30 m Data analysis (average salinity at 28-32 m) from each sweep ofthe May-June surveys of 1990 and 1991 was contoured Statistical analyses were performed by using the byusing the Kriging option in the program SURFER program SAS (SAS Institute, Inc., 1988). Abundances (Golden Software, Inc., 1990). Owing to problems were transformed by In(x+1) to normalize the data. with the CTD during the second sweep ofthe May Mean abundances from theApril surveys andfor each June survey of 1991, thermosalinometer data were sweep ofthe May-June surveys were then calculated incorporated into the available CTD data to gener for all standard stations successfully sampled to de ate the surface contours. The log-transformed abun scribe temporal differences in abundance. dances ofmetamorphic stages 2 and 5 were overlaid Means and ranges of SL's of the metamorphic onto the salinity contours to observe the relation (if stages of both sanddab species were calculated by any) between the abundances ofthese two metamor using specimens measured from theApril and May phic stages and salinityfeatures indicative ofcoastal June

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