To evaluate growth of the Pacific sardine in the Gulf of California, fish samples were collected from the commercial fleet during the 2010-11, 2011-12 and 2012-13 fishing seasons. Sardine samples were measured in standard length (SL) and age was determined based on counting opaque and hyaline growth increments in the otoliths. Four growth models were fitted to the age and length data: von Bertalanffy Growth Model (VBGM), Gompertz, Logistic, and Schnute, using a maximum likelihood algorithm. Confidence intervals of each parameter were calculated through likelihood profiles. The model that best explained the species growth kinetics was selected by Akaike information criteria and Akaike's weight (w(i)), while growth parameter covariance was obtained by the likelihood contour method. The sardines obtained from catches ranged in age from 0.5-6 years; sizes varied from 98-218 mm (SL). The growth model that obtained the greatest weight was VBGM (w(i) = 73.11%) whose estimated parameters and confidence intervals (CI) for the Pacific sardine were L-infinity= 201.28 (200.70-201.80) mm SL, K = 0.581 (SD: 0.577-0.586) and t(0) = -0.839 (SD: -0.855 - -0.824), showing a more accelerated growth rate of the species in the Gulf of California compared to the same species inhabiting the coasts of Baja California and California.
From 2014 to 2018, we conducted laboratory experiments to develop methods for inducing spawning in Pacific sardine (Sardinops sagax). Wild caught immature S. sagax were acclimatized for three months, reared until they were fully mature, and then induced to spawn. Fish reared at 14.5 degrees-18 degrees C and 4-12 h day-light, and fed a vitamin-enriched diet, were mature by 27 months. Fish treated with hormones prior to 24 months of rearing did not spawn, but those injected at 27 and 39 months spawned and naturally fertilized their eggs.The successful induction method consisted of human chorionic gonadotropin injections followed by a combination of carp pituitary extract and Domperidone injections 24 h later. Spawning occurred approximately 20 h after the second hormonal treatment. Eggs collected at 27 months and incubated at 11 degrees, 13 degrees, and 15 degrees C produced healthy larvae, but those spawned at 39 months did not survive to the larval stage. Ovaries were fully matured in February, but their oocytes regressed by May, suggesting that under controlled environment conditions S. sagax followed a seasonal maturity cycle similar to that of the naturally spawning population off California.
The spatial distribution, abundance, and size variability of two pelagic tunicate species, Thetys vagina and Pyrosoma atlanticutn, were examined from midwater trawl surveys to assess the historical context and geographical aspects of a major mass occurrence event throughout the California Current Large Marine Ecosystem during 2012-19. Off central California, abundance of both species were significantly greater in 2012-19 compared to 1983-2001, and their recent persistent multiyear abundance peaks were unprecedented. Coastwide abundance and distribution of T. vagina during 201319 was patchy, with no discernible shifts in distribution or changes in mean length. From 2013-18, abundance and distribution of P. atlanticum demonstrated a temporal trend of increasing abundance from south to north, and in northern areas, average P. atlanticum colony length increased over time. In 2019, high abundances of P. atlanticum occurred south of Monterey Bay, but were not found in the northern California Current. We discuss how in situ and regional-scale environmental drivers may have contributed to this recent multiyear gelatinous mass occurrence, and potential consequences to forage community structure and ecosystem function.
Juvenile north Pacific albacore (Thunnus alalunga) forage in the California Current System (CCS), supporting fisheries between Baja California and British Columbia. Within the CCS, their distribution, abundance, and foraging behaviors are strongly variable interannually. Here, we use catch logbook data and trawl survey records to investigate how juvenile albacore in the CCS use their oceanographic environment, and how their distributions overlap with the habitats of four key forage species. We show that northern anchovy (Engraulis mordax) and hake (Merluccius productus) habitat is associated with productive coastal waters found more inshore of core juvenile albacore habitat, whereas Pacific sardine (Sardinops sagax) and boreal clubhook squid (Onychoteuthis borealijaponica) habitat overlaps more consistently with that of albacore. Our results can improve understanding of how albacore movements relate to foraging strategies, and why prey-switching behavior occurs. This has relevance for the development of ecosystem models for the CCS, and for the eventual implementation of ecosystem-based fishery management.
The California Current Ecosystem (CCE) has been in a primarily warm state since 2014, and this pattern largely continued into 2019. The CCE experienced a mild El Nino from late 2018 into 2019, and basin-scale indicators reflected this condition (elevated Oceanic Nitio Index and Pacific Decadal Oscillation; table 1). Despite the El Nino, spring upwelling was above average between southern California and Washington but below average in Baja California. Sea surface temperature (SST) was mostly near the long-term average between Washington and southern California, while surface chlorophyll a was above average in Oregon/Washington and slightly below average in most of California in spring/early summer 2019. SST changed dramatically by fall 2019, however, as a marine heat wave (MHW) that formed in May 2019 in the Gulf of Alaska impinged upon the West Coast of the United States. The expansion of the 2019 MHW followed a similar pattern to the 2014-15 MHW. Off Oregon, the zooplankton assemblage was in a mixed state as southern copepods were close to average while northern copepod abundances were positively anomalous in 2019. Off northern California, Euphausia pacifica body size was smaller than average. Euphausid abundances were well below average in both central and southern California in 2019. In the north, winter 2019 larval fish abundances were high and dominated by offshore taxa that are associated with warm conditions; spring larval and post-larval biomass were close to average; and spring surface trawls observed record-high market squid (Doryteuthis opalescens) abundances. The single most important finding in 2019 was that northern anchovy (Engraulis tnordax) adults and larvae were at record-high abundances in central and southern California. In central California, market squid and Pacific sardine (Sardinops sagax) were also abundant. In southern California warm-water mesopelagic fishes have been very abundant since 2014, and this trend continued into 2019. Indicators for future salmon returns were mixed in 2019. The abundance of northern copepods, which correlate positively with returns, was high. However, abundances of yearling Chinook salmon (Oncorhynchus tshawytscha) and coho salmon (O. kisutch), which also correlate positively with returns, were slightly below average. Winter ichthyoplankton was comprised mostly of southern or offshore taxa, which bodes poorly for future salmon returns. Seabird (common murre [Urfa aalge]; Brandt's cormorant [Phalacrocorax penidllatus]; and pelagic cormorant [Phalacrocorax pelagicus]) productivity off Oregon was the highest in years in both 2018 and 2019. In 2018, common murre chicks in Oregon consumed large amounts of young-of-the-year flatfish, a prey item known to be conducive to chick survival. Despite the prevalence of northern anchovy in central California, common murre and Brand's cormorant production was low in Southeast Farallon Island as these birds were unable to feed optimally on northern anchovy, and there was a scarcity of more appropriate prey such as young-of-the-year flat-fishes or rockfishes. California sea lions (Zalophus californianus), by contrast, benefitted greatly from the large northern anchovy forage base. In 2018, live pup count, weight, and growth rate were anomalously high, and northern anchovy remains occurred in >85% of scat samples. Humpback whale (Megaptera novaeangliae) sightings were also very high in 2019, likely because humpback whales congregated near shore to feed on northern anchovy.
The successful adaptive management of marine protected areas (MPAs) requires knowledge of spatial variability in the rates of juvenile fish recruitment to recovering fish populations.We used the foraging rates of two piscivorous seabirds (Brandt's cormorant and pelagic cormorant) to index juvenile fish abundance at 46 sites throughout California's MPA network. We used mixed effects negative binomial regression to develop models relating seabird foraging rates to coastal geography and annual upwelling strength and variability. The best models for both species included upwelling variability among years (i.e., persistent versus pulsed upwelling). The effects of upwelling variability differed depending on coastal geography. In the lees of headlands, foraging rates were highest and more stable with respect to upwelling variability. For all other coastal configurations, pulsed upwelling was associated with higher foraging rates. Thus, periods of relaxation in upwelling appear to be important for these sites. Our results suggest that coastal geography should be considered when establishing realistic expectations for the performance of individual MPAs.
Following the marine heat wave of 2014-16, the California Current System (CCS) trended towards more typical conditions north of Point Conception, California, from mid-2017 to mid-2018, but became highly abnormal in the south by mid-2018.Two basinscale indices (Pacific Decadal Oscillation and Oceanic Nino Index) were close to neutral, but the North Pacific Gyre Oscillation was extremely low at the end of 2017 and beginning of 2018. Regional analyses demonstrated that upwelling was close to normal throughout most of the CCS with the exception of high upwelling from northern California to Washington in summer and fall of 2017. Sea surface temperature was close to normal throughout most of the CCS but warmed to record levels in summer 2018 in southern California and northern Baja California. In spring 2018, surface chlorophyll a was negatively anomalous throughout most of the US West Coast with localized hot spots around the Columbia River, in the Gulf of Farallones, and Monterey Bay. Lipid-rich copepod densities and sizes returned to normal levels in the northern CCS, and euphausiid abundances were above average in central California but below average in southern California in spring 2018. Abundances of 7 zooplankton taxa were slightly to well above average off of northern Baja California in late 2017. Pyrosomes, which are associated with warm water, were found throughout the CCS. The fish assemblage off Oregon and Washington was comprised of both northern and southern/offshore species. In the central region (near Monterey Bay) most fishes were close to long-term mean abundances; however, adult northern anchovy (Engraulis mordax) abundance was the highest on record. The ichthyoplankton assemblage off southern California had a tropical signal similar to 2014-15 as warm-water associated mesopelagic abundances were close to record highs and cold water mesopelagics abundances were very low.Anchovy larvae abundances in southern California were the highest since the 1960s. Indicators that can affect salmon survival were mixed in 2018. On the one hand, several indices forecast high salmon return (moderate-high salmon yearling abundance, high larval fish (salmon prey) abundance, normal lipid-rich copepod abundances). On the other hand, low survival was predicted by high fall PDO, high abundances of offshore larval fishes, and above average abundance of lipid-poor copepods.This unusual mix of indicators makes it difficult to forecast salmon returns in upcoming years. Common murre (Urfa aalge) reproduction was historically low in the northern CCS in 2017 as colonies experienced complete reproductive failure both at Yaquina Head, Oregon, and Castle Rock, California. In both cases, forage was scarce, birds conducted long foraging excursions which left eggs unattended for extended periods, and many eggs were consumed by avian predators. Brandt's (Phalacrocorax peniscillatus) and pelagic (P. pelagicus) cormorants had above average reproductive success in 2017 at Yaquina Head, but Brandt's cormorant also had total reproductive failure in 2017 at Castle Rock. At Southeast Farallon Island murre, Brandt's cormorant, and pelagic cormorant productivity was close to average in 2017, and Brandt's cormorant and murre were slightly above average in 2018. Preliminary 2018 results fromYaquina Head also indicated that murre successfully produced chicks for the first time since 2014. At-sea bird surveys in the north demonstrated that sooty shearwater and common murre abundances were historically low in 2017, but increased to some of the highest values on record in 2018. By contrast, the at-sea surveys off central California found that murre densities were anomalously high in 2017 but fell to an average level in 2018. Improving California sea lion (Zalophus californianus) pup condition continued from 2016 into 2017 as live pup counts, pup weight, and rate of growth were above average. Augmented pup conditions in 2016-17 was likely driven by increased availability of anchovy, as anchovy remains were found in nearly 100% of sea lion scat. There were record high encounters with Humpback whales (Megaptera novaeangliae) off central California in 2018. Overall, much of the CCS was in more of a normal state through mid-2018 relative to the past 5 years. However, remnants of the 2014-16 marine heat wave were still resonating in the north, and another highly anomalously warm water event affected the southern part of the CCS in summer 2018. Thus, while the CCS was returning to typical conditions in the north, it was anything but normal in the south in 2018.
Pacific sardine collected during the spawning season off the coast of California (US) were used to investigate the process of female maturation. Pacific sardine maturation is better described as an age-based rather than a length-based process, and its temporal variation is better described by annual rather than cohort effects. Temporal variation in maturation is large with the age at 50% maturity annually varying by more than 1 year. This results supports that annual variability is substantial and may be driven by environmental rather than density dependent factors. Including time-varying age-based maturation into the assessment model improved model prediction of recruitment. It is recommended that future assessments consider inclusion of this temporal variability of an age-based process.
Knowledge of biomass and demographic aspects is important in fish stock assessments. These aspects were analyzed on Micropogonias megalops in the Gulf of California, Mexico, using biological data from catches in 2010-12. Individual growth was estimated following a multi-model approach. Logistic models were used for first maturity and fishing selectivity, and natural mortality by means of empirical equations and biomass by the Pennington estimation.The results showed that the von Bertalanffy model best described growth for combined data (w(i) = 72.86 %), females (w(i) = 67.82 %) and males (w(i) = 69.42 %), but they showed sexual dimorphism on the species. First maturity was at 357.8 mm, fishing selectivity 323.35 and 366.35 mm for industrial and artisanal fleet, respectively, and average natural mortality of 0.51. Mean biomass was 14 412.9 tons contrasting the officially reported catch that represented only 8.7% of estimated biomass, showing evidence that M. megalops is still an underexploited resource.
The Pacific sardine, Sardinops sagax, is a highly migratory coastal pelagic species that occurs from the tip of Baja California to the Gulf of Alaska and in the Gulf of California. We used fishery-independent egg surveys to characterize the relative amounts of sardine spawning habitat in the exclusive economic zones (EEZ5) of Mexico and the US during spring 2000-13. Most eggs were captured in the US EEZ from San Francisco to the Mexico-US border in all years sampled. A small fraction ranging from 0% to 10% of all eggs captured occurred in the Mexican EEZ, usually from Punta Eugenia north to the border. The abundance and distribution of eggs found in warmer waters between 15 degrees C to 18 degrees C off northern Baja California appear to be dependent on periods of more intense flow of the California Current, when sardine belonging to the northern subpopulation found in central and southern California extends southward into the nearshore area off Baja California. However, a small fraction of the southern subpopulation may also have spawned in coastal areas of the US-Mexican border during May in some years.
Baseline reproductive information is crucial to identifying species responses to spatiotemporal variation and changing environmental conditions. We collected 205 central California halibut (2012 and 2013) to better understand the reproductive tactics of a batch spawner with indeterminate fecundity. We used histology to identify subphases of actively spawning fish, approximated spawning duration based on weekly proportions of reproductive females, calculated daily spawning fractions to estimate interspawning intervals, and quantified batch fecundity using the hydrated oocyte method. The spawning season lasted approximately 10 weeks. Interspawning intervals were 1.3 to 2.7 d, depending upon the spawning marker (i.e., hydrated oocytes or POFs) used. Mean batch fecundity for fish in the late hydration subphase of spawning was 597,445 +/- 318,419 eggs, resulting in annual fecundities that ranged from 5.2 x 10(6) to 8.1 x 10(7) eggs per fish.These findings provide a preliminary assessment of reproductive output for California halibut and foundation data for future spatiotemporal analyses.
To correctly interpret trends in species’ abundance in long time series it is essential to account and correct for biases that may arise in association with changes in sampling methodology. We assess how gear changes for oblique plankton net tows (from 1 m diameter ring to 0.71 m diameter bongo net in 1977) affected ichthyoplankton abundance estimates from the California Cooperative Oceanic Fisheries Investigations (CalCOFI) program. Paired ring and bongo net samples were analyzed from 133 stations sampled in 1977–78. To quantitatively correct for net-associated bias, we first modeled abundance in bongo nets as a function of abundance in ring nets for larvae and eggs summed across all taxa during day and night with generalized linear models (GLM; identity link with gamma error structure). Models suggest that greater visual avoidance for ring than bongo nets induces bias in abundance estimates as slope estimates were greater than 1 for combined larvae during the day but did not differ significantly from 1 for combined larvae at night, or eggs during day or night. Ratios of summed abundances between bongo and ring nets for the 15 most common taxa indicated that there were significantly higher abundances for 4 taxa in the bongo than the ring net during the day but values did not differ at night between net types. To make data collected in ring nets before 1978 more comparable to data from bongo nets our results suggest it is necessary to adjust abundance estimates during the day from ring nets by a factor of 2 for Cyclothone spp., 2.17 for Diogenichthys spp., 2.06 for Engraulis mordax, and 1.53 for Vinciguerria spp. It may also be necessary to reevaluate results from past studies that utilize the CalCOFI larval time series that did not correct for net bias. More data are needed to ascertain the effect of net change on species such as Sardinops sagax or Tarletonbeania crenularis that were uncommon in the late 1970s but have been encountered frequently in recent years. INTRODUCTION Long time series are essential for truly understanding the mechanisms governing variability in the dynamics of populations and communities in all ecosystems (Krebs et al. 2001; McClatchie 2014). Short-term fluctuations are often nested within long-period dynamics and attempts to discern the causes of species variability over short time periods may produce erroneous conclusions (McClatchie et al. 2017). This is particularly true in an era of rapid climate change as the effect of changes in environmental conditions on ecosystems can be conceptualized only when placed in the context of a long time series. Therefore, it is extremely important for species management and conservation programs to maintain and build upon long time series over upcoming years and decades. Equally important as maintaining long time series is ensuring that samples collected over time are comparable to one another. Bias can arise if systematic differences in collection methods that affect the probability of capturing an organism are imposed upon the time series (MacKenzie et al. 2002). For example, trends from fisherydependent data may not reflect true population dynamics of a fished species if the fleet introduced more effective gear for catching the targeted species at some point in the time series. Accounting for methodological differences in data collection is imperative to properly interpret potential changes in species abundances for time series analysis (MacKenzie et al. 2005). The California Cooperative Oceanic Fisheries Investigations (CalCOFI) program provides some of the most complete marine ecosystem monitoring data in the world. CalCOFI has continuously sampled biological (plankton tows) and oceanographic conditions (CTD and water collections) from the same 66 core stations off southern California since 1951 (McClatchie 2014). From a biological perspective, the resultant data give information on variability in the distribution and abundance of zooplankton (McGowan and Walker 1985; McGowan et al. 1998; Lavaniegos and Ohman 2007) and ichthyoplankton (Hsieh et al. 2005; Hsieh et al. 2006; Hsieh et al. 2009; Lindegren et al. 2016) over more than six decades. At several points in the time series CalCOFI plankton sampling was changed to introduce methodological improvements. In all years, samples were obtained by lowering a net to a set depth and towing it obliquely (at a 45 ̊ angle) to the surface at a constant speed. However, THOMPSON ET AL.: CORRECTING FOR BIAS IN CALCOFI ICHTHYOPLANKTON ABUNDANCE ESTIMATES CalCOFI Rep., Vol. 58, 2017 114 lected using both nets at the same 160 stations during seven CalCOFI cruises between winter 1977 and summer 1978. At present, net effects on sampling efficiency have been thoroughly vetted for zooplankton (Smith 1974; Brinton and Townsend 1981; Ohman and Smith 1995; Rebstock 2001; Ohman and Lavaniegos 2002). However, with the exception of an investigation on northern anchovy, Engraulis mordax (Hewitt 1980), comparable analyses have not been published for ichthyoplankton. Here we evaluate if larval abundance estimates are biased by gear type and test the hypothesis that bias will be greater during the day when larvae would be able to better see and avoid the ring than the bongo net.
Updated abundance estimates of the central subpopulation of northern anchovy (Engraulis mordax) are developed from California Cooperative Oceanic Fisheries Investigations (CalCOFI) data on egg and larval densities for 1951-2011, with new estimates for 2012-15. We followed the approach of MacCall et al. (2016; Fish. Res.) which corrected for a hyperstability bias due to nearshore concentration of CalCOFI stations and the tendency of the anchovy population to contract into this area when abundances are low. We corrected previous estimates based on calibration using an erroneous absolute biomass value from the 1980s, and extended estimates up through 2015. Anchovy spawning biomass remains below 100,000 metric tons, at an average of 20,700 metric tons over the past 7 years. Although the most recent 2016 CalCOFI data are not yet available, recent results from the continuous underway fish egg sampler (CUFES) do not indicate any substantial recovery of the anchovy population to date.
Two Panamic fish species and one species from the Cortez-San Diegan Provinces were recorded for the first time in and near Bahia de San Quintin, Baja California, Mexico, during 2014 and 2015. The area is normally cold because of locally intense upwelling. However, during 2014 and 2015, warm water prevailed, which appears to have led to the presence of these fish species within and outside of the bay. Five specimens of Selene brevoortii (Mexican lookdown) were recorded, one individual in October 2014, and three more individuals during July 2015; another specimen, completely dry, was provided by a fisherman as evidence of their presence at an intermediate date within this period. Also in 2015, seven individuals of fish were captured with a commercial gill net set just outside of the bay; five of these were identified as Lobotes pacificus (Pacific tripletail) and the other two individuals as Albula gilberti (Cortez bonefish). Captures of these tropical species, in an usually cold-water environment are evidence of a substantial fish movement from the tropical Pacific toward the temperate waters of Baja California and California, USA, during warming conditions.
Pacific herring are important to fisheries and trophic interactions in the California Current Ecosystem (CCE). In this paper we test the hypothesis that herring biomass across the ecosystem has declined over the past three decades. Overall, herring spawning stock biomass has decreased since the mid to late 1980s, though some populations at the local to regional scale appear stable or have even increased. For regional populations in the northern CCE studied over a much longer time period (six decades), cyclic patterns of abundance are evident, suggesting that the shorter-term trend may be part of a longer-term, Pacific Decadal Oscillation (PDO)-scale cycle. In the southern part of the herring range (California and Oregon), population fluctuations are increasing, which may be related to increasing climate variability there (Sydeman et al. 2013; Black et al. 2014). Large-scale trophic mechanisms to local distribution shifts are implicated in metapopulation fluctuations. Future abundance assessments for herring in the CCE should address how climate and fisheries may synergistically impact populations.
Temperature is a primary factor separating Pacific sardine Sardinops sagax into cold and temperate stocks in the California Current Ecosystem. We collected otoliths of age-1 sardine captured in the spring off central California (1996-97) and in the Southern California Bight (SCB; 1991-92 and 1995-2004) where the cold and temperate stocks presumably overlap during seasonal migrations. To assess whether the sardine had distinguishing chemical characteristics, we compared trace element profiles of otoliths with seawater temperatures to evaluate composition and interannual variability. Ca, Mg, P, Sr, Mn, and Ba in dissolved whole otoliths were analyzed by inductively coupled plasma mass spectrometry. Cohorts from central and southern California differed by collection site in Mg/Ca and P/Ca ratios. Mg/Ca and P/Ca ratios covaried and correlated with sea-water temperature in the SCB in most years. High inter-annual variability in some trace element ratios within sites made it difficult to characterize site-specific otolith profiles. Otolith composition was likely influenced by temperature and local conditions. Stock mixing in the SCB may have contributed to interannual variability as well.
MacCall et al. (2016) recently published an estimate of the biomass of the central stock of northern anchovy (Engraulis mordax) off the coast of California, and found that this stock experienced a population crash from 2009-15. However, anecdotal observations concurrent to the collapse suggested that anchovy were extremely abundant. We used central and southern California data from two trawling surveys, ichthyoplankton time series, and aerial surveys to investigate whether or not any anchovy spawning was missed by MacCall et al. We found no evidence using additional and more recent data that 1) anchovy adults migrated north of the study area, 2) there was a large biomass of anchovies near shore, or 3) spawning was temporally missed by MacCall et al. Thus, we conclude that the 2009-15 population crash is real and that the anchovy population remnant contracted to extremely nearshore habitat where it appeared paradoxically abundant to observers.
Author(s): Wells, Brian K; Schroeder, Isaac D; Bograd, Steven J; Hazen, Elliott L; Jacox, Michael G; Leising, Andrew; Mantua, Nathan; Santora, Jarrod A; Fisher, Jennifer; Peterson, William T; Bjorkstedt, Eric; Robertson, Roxanne R; Chavez, Francisco P; Goericke, Ralf; Kudela, Raphael; Anderson, Clarissa; Lavaniegos, Bertha E; Gomez-Valdes, Jose; Brodeur, Richard D; Daly, Elizabeth A; Morgan, Cheryl A; Auth, Toby D; Field, John C; Sakuma, Keith; McClatchie, Sam; Thompson, Andrew R; Weber, Edward D; Watson, William; Suryan, Robert M; Parrish, Julia; Dolliver, Jane; Loredo, Stephanie; Porquez, Jessica M; Zamon, Jeannette E; Schneider, Stephanie R; Golightly, Richard T; Warzybok, Pete; Bradley, Russell; Jahncke, Jaime; Sydeman, William; Melin, Sharon R; Hildebrand, John A; Debich, Amanda J; Thayre, Bruce
Movements of lingcod implanted with acoustic transmitters were monitored for a year in central California. Half of the tagged lingcod remained within 5 km of coastline for at least 50% of days in the year, and 30% of lingcod were detected for >80% of the study days. Lingcod demonstrated distinct patterns in residency that were correlated to sex, fish length, and season. Residence times of females decreased with total length; female lingcod >90% maturity were present during the fall spawning season and briefly during the spring. Size-specific movements were less pronounced for males, but daily detections of males declined in spring, at the end of the winter nest-guarding season. The majority of lingcod detections were constrained to a limited area, however a few lingcod exhibited movements up to several kilometers. These results indicate that marine reserves can serve to both protect lingcod and also provide fisheries benefits via spillover.
We describe the seasonal variation of hyperiid amphipods in oceanic waters between Punta Eugenia and Punta Abreojos, Baja California, during 2011, a cool year due to the influence of La Nina. Mean sea surface temperature in the study area was similar from January to July (16 degrees-17 degrees C) but cooler than usual, with anomalies of -1 to -3 degrees C in the context of 1997-2013. Further, SST increased 3 degrees C in October, restoring the typical temperature during this month (21 degrees C). Vertical salinity profiles were also similar during January, April, and July, showing the influence of subarctic water in the upper layer (33.3-33.7 psu), while in October a range of higher values (33.5-33.8 psu) was observed due to the influence of subtropical water. We recorded 63 hyperiid amphipod species in 2011, the lowest number in January and the highest in October (17 and 54, respectively). Despite seasonal changes in diversity, few species (Eupronoe minuta, Primno brevidens, Lestrigonus schizogeneios, and Simorhynchotus antennarius) were the most abundant throughout the year. The exception was the warm-water species Lestrigonus bengalensis, which was the second most abundant in October, indicating the influence of subtropical oceanic water. Similarity analysis showed similar communities for spring and summer, while winter and autumn were very dissimilar from each other and differed from the spring-summer cluster. However, the species with highest contribution to similarity were the same (E. minuta, L. schizogeneios, and P. brevidens) but with different proportions. A matrix of environmental variables was correlated with the amphipod similarity matrix through a BIOENV analysis. The best combination of environmental variables (rho S = 0.644) was the 10 m depth temperature, 10 m depth salinity, mixed layer depth, stratification in the upper 100 m, and zooplankton volume (this last used as a proxy for host availability). Finally, when the community structure was compared with data from a previous amphipod study (2005), we found that species composition was very similar, but seasonal differences in the abundance of 30 of the 52 common species persist possibly due to the effects of La Nina.
