KOSLOW ET AL.: LOBSTER PHYLLOSOMA ABUNDANCE LINKED TO WARM CONDITIONS CalCOFI Rep., Vol. 53, 2012 A TIME SERIES OF CALIFORNIA SPINY LOBSTER (PANULIRUS INTERRUPTUS) PHYLLOSOMA FROM 1951 TO 2008 LINKS ABUNDANCE TO WARM OCEANOGRAPHIC CONDITIONS IN SOUTHERN CALIFORNIA J. ANTHONY KOSLOW LauRA ROGERS-BENNETT DOUGLAS J. NEILSON Scripps Institution of Oceanography California Department of Fish and Game California Department of Fish and Game University of California, S.D. Bodega Marine Laboratory 4949 Viewridge Avenue La Jolla, CA 92093-0218 UC Davis, 2099 Westside Rd. San Diego, CA 92123 ph: (858) 534-7284 Bodega Bay, CA 94923-0247 [email protected] ABSTRACT The California spiny lobster (Panulirus interruptus) population is the basis for a valuable commercial and recreational fishery off southern California, yet little is known about its population dynamics. Studies based on CalCOFI sampling in the 1950s indicated that the abun- dance of phyllosoma larvae may be sensitive to ocean- ographic conditions such as El Niño events. To further study the potential influence of environmental variabil- ity and the fishery on lobster productivity, we developed a 60-year time series of the abundance of lobster phyl- losoma from the historical CalCOFI sample collection. Phyllosoma were removed from the midsummer cruises when the early-stage larvae are most abundant in the plankton nearshore. We found that the abundance of the early-stage phyllosoma displayed considerable inter- annual variability but was significantly positively corre- Figure 1. Commercial (solid circles), recreational (open triangles), and total lated with El Niño events, mean sea-surface temperature, landings (solid line) of spiny lobster off southern California. Figure 1. and the Pacific Decadal Oscillation, which are signif- icantly intercorrelated. Conditions during the warm ports to reduce the proportion of “shorts” in the land- years (1950s and 1980–present) were the most produc- ings (fig. 1) (Neilson 2011). Since 2000, the commercial tive for lobster phyllosoma in the Southern California fishery has landed approximately 300 mt annually, with Bight. Total lobster fishery landings show an increasing 319 mt landed in 2010 for an ex-vessel price of $11.13 trend since 1980 due to increasing commercial land- million. While the commercial landings have been stable ings from 1980–2000 and increased recreational landings since 2000, recreational landings have increased consid- since 2005. However, this trend is not observed in the erably due to the growing popularity of hoopnet fish- phyllosoma time series or in the Baja California fishery, ing, particularly since 2005. The recreational fishery whose landings are correlated with the U.S. fishery.W e now accounts for 30%–60% of the commercial fishery suggest that the stage 1 phyllosoma may provide a use- (fig. 1). However, the fishery was considered sustain- ful fishery-independent index of spiny lobster spawning able in a recent stock assessment (Neilson 2011), and no stock biomass and stock productivity. Due to the rela- regulatory change is currently proposed for California. tionship identified here between environmental condi- Early life-history stages of marine organisms can serve tions and phyllosoma abundance, we suggest that this as an indicator of the abundance and productivity of the information could be used as an environmental indica- adult spawning stock (Hsieh et al. 2005). Egg and lar- tor for management. val surveys in California Cooperative Oceanic Fisheries Investigations (CalCOFI) are routinely used as indica- INTRODUCTION tors of spawning stock biomass for fisheries20 management The California spiny lobster (Panulirus interruptus) has (Moser et al. 2001; Lo et al. 2005). We suggest that the been fished commercially off southern California since early stage phyllosoma may also be suitable as an index the late 1800s. Commercial landings peaked around for the spawning biomass of spiny lobster: having been 1949–55, declined in the period 1955–75, and subse- in the plankton relatively briefly, their abundance has quently increased, following the requirement in 1976 not been greatly influenced by natural mortality. Because that commercial lobster traps be fitted with escape there are no other fishery-independent measures for the 132 Koslow r3 lo.indd 132 10/30/12 9:05 PM KOSLOW ET AL.: LOBSTER PHYLLOSOMA ABUNDANCE LINKED TO WARM CONDITIONS CalCOFI Rep., Vol. 53, 2012 Figure 2. The core CalCOFI sampling area with six transects from the U.S./Mexico border to north of Point Conception. Only stations 60 and inshore were used in the present study because of the coastal distribution of the early-stage phyllosoma. Figure 2. state of the spiny lobster population, we developed a losoma abundance off southern California appeared time series of early-stage lobster from the CalCOFI sam- to be enhanced during El Niño events, when there is pling program, which can potentially provide further increased northerly transport of the Davidson Current input to management of this resource. A phyllosoma from Baja California. The lobster mature at 65–69 mm time series can also be examined in relation to oceano- carapace length at about 5–9 years of age and recruit graphic parameters to determine if climate variability to the fishery at 82.6 mm, about two years later. Most has a significant impact on the abundance of larval or recruits are removed by the fishery each year. adult lobster. Biological indices of ocean condition have Our objectives are to utilize the CalCOFI sampling provided input to management models for sardine and to 1) develop a 60-year time series of phyllosoma and sablefish fisheries in the California Current (Jacobson 2) examine potential impacts of ocean conditions and and MacCall 1995; King et al. 2001). the fishery on phyllosoma abundance. The spawning and early life history of the Califor- nia spiny lobster was examined in the early 1950s using METHODS CalCOFI samples (Johnson 1956, 1960a, 1960b). At that The CalCOFI program has consistently sampled the time, CalCOFI sampling extended over most of the coast zooplankton, including invertebrate and fish larvae, over of California, including Baja California (Mexico) and a core area from the U.S./Mexico border to north of thus encompassed the population’s distribution, which Point Conception since 1951, with monthly to quar- extends from Point Conception to Magdalena Bay in terly sampling from nearshore to several hundred kilo- Baja California and is centered off central Baja (John- meters offshore (fig. 2). At each station, the physical and son 1960a). Spawning occurs in late summer and early chemical properties of the water column to 500 m depth autumn, with peak numbers of the early-stage phyl- are sampled, and at least one oblique zooplankton tow losoma found from July to October. Remarkably, the is undertaken: prior to 1969 to 140 m and subsequently phyllosoma drift offshore and remain in the plankton to about 210 m depth. Details of the sampling proto- for 7–10 months until the following spring, when they col21 are found in Kramer et al. 1972 and Ohman and metamorphose into the swimming puerulus stage, return Smith 1995, including the change from a 1-m ring net to shore, and settle on the bottom as benthic juvenile to the 0.71 m diameter bongo net in 1977. All fish eggs lobsters (Johnson 1956, 1960b). Pringle 1986 re-exam- and fish larvae are routinely removed from all zooplank- ined the CalCOFI time series and showed that the phyl- ton samples. However, until recently, invertebrate larvae, 133 Koslow r3 lo.indd 133 10/30/12 9:05 PM KOSLOW ET AL.: LOBSTER PHYLLOSOMA ABUNDANCE LINKED TO WARM CONDITIONS CalCOFI Rep., Vol. 53, 2012 Figure 3. The CalCOFI sampling grid showing the mean abundance of phyllosoma at each station (1951–2008) and the division of the sampling area into high-abundance and low-abundance strata inshore and offshore. including those of the spiny lobster, were only removed We examined relationships between annual mean if undertaken by a particular investigator. Spiny lobster phyllosoma abundance and environmental variables phyllosoma larvae are highly distinctive but also a rare sampled on CalCOFI cruises and indices for several component of the plankton. To re-sort all the CalCOFI large-scale environmental features. Sea-surface temper- samples would have been a laborious task. However, Dr. ature (SST) was based on the mean annual temperature Johnson sorted the samples for the period 1951–57 and measured at 10 m from CalCOFI cruises. The Multi- 1970–81, and the data were retrieved from the Scripps variate ENSO (El Niño Southern Oscillation) Index Library Archive. Since 2008, the CalCOFI program (MEI) (Wolter and Timlin 1998) was obtained from and National Marine Fisheries Service routinely sort the National Oceanic and Atmospheric Administra- for phyllosoma. The early-stage phyllosoma were only tion (NOAA) Earth System Research Laboratory MEI found in sufficiently high numbers in July/August, so we Web page: http://www.esrl.noaa.gov/psd/enso/mei; the focused on the summer CalCOFI cruises from 1958–69 Pacific Decadal Oscillation (PDO) (Mantua et al. 1997) and 1982–2008. Phyllosoma were only rarely obtained from the University of Washington: http://jisao.wash seaward of station 60, so we only examined stations on ington.edu/pdo/PDO.latest; the North Pacific Gyre the six core transects (lines 76 to 93) from inshore to Oscillation (NPGO) (Di Lorenzo et al. 2008) from the station 60 (fig. 2). All samples were sorted under a bin- website of E. Di Lorenzo: http://www.o3d.org/npgo/ ocular microscope, and the phyllosoma were staged using data/NPGO.txt; and upwelling was based on offshore the criteria in Johnson 1956. The data are available from Ekman transport at 33˚N and 119˚W (Pacific Fisher- the CalCOFI DataZoo data repository: http://ocean ies Environmental Laboratory: http://las.pfeg.noaa.gov/ informatics.ucsd.edu/datazoo/data/calcofisio/datasets?a las6_5/servlets/dataset).