Search results

Title: At-sea mortality of seabirds based on beachcast and offshore surveys,
Description: Although seabird population biology is relatively well studied, little data exists on mortality at-sea. Beached bird surveys are used to identify patterns of seabird mortality, but resulting patterns are difficult to interpret without corresponding data on at-sea density. We examined seabird mortality relative to at-sea density in Monterey Bay, California over 10 yr by integrating data from monthly beachcast seabird and offshore seabird censuses. Beachcast seabird numbers were relatively constant (mean 2.82 ± 0.31 seabirds km -1) throughout the year. At-sea seabird density (mean 148.9 ± 16.12 seabirds km-2) peaked in the summer upwelling period and was least in the winter Davidson period. A principal components analysis of seasonal climatic, prey availability, and anthropogenic variables for Monterey Bay derived 3 significant principal components (PCs) (explaining 70% of variance) characterized by storm activity and low prey availability (PC1), river discharge and krill abundance (PC2), and oiling (PC3). These principal components were used in detailed analyses of the 2 most abundant seabird species and indicate that sooty shearwater Puffinus griseus relative mortality is greatest during decreased productivity and increased storm activity. While relative mortality of common murres Uria aalge cannot be explained by the derived principal components, relative mortality increased in late winter when prey availability decreased concurrent with the annual increase in reproductive stress. Beachcast seabird data is difficult to interpret in isolation; however, when linked to at-sea densities of seabirds, it becomes a powerful tool to examine the relative impacts of oceanography and direct human perturbations on seabird demography. © Inter-Research 2009., Cited By (since 1996):1, Marine Mammals, Birds & Turtles, CODEN: MESED, ,
Author: Newton, Croll, Nevins, Benson, Harvey, Tershy
Date: 2009-01-01T00:00:00Z

Title: Training California sea lions to record whale behavior using a rehabilitating California gray whale calf,
Description: , , ,
Author: Harvey, Hurley, Skrovan
Date: 2001-01-01T00:00:00Z

Title: Patterns in the vocalizations of male harbor seals,
Description: Comparative analyses of the roar vocalization of male harbor seals from ten sites throughout their distribution showed that vocal variation occurs at the oceanic, regional, population, and subpopulation level. Genetic barriers based on the physical distance between harbor seal populations present a likely explanation for some of the observed vocal variation. However, site-specific vocal variations were present between genetically mixed subpopulations in California. A tree-based classification analysis grouped Scottish populations together with eastern Pacific sites, rather than amongst Atlantic sites as would be expected if variation was based purely on genetics. Lastly, within the classification tree no individual vocal parameter was consistently responsible for consecutive splits between geographic sites. Combined, these factors suggest that site-specific variation influences the development of vocal structure in harbor seals and these factors may provide evidence for the occurrence of vocal dialects. © 2003 Acoustical Society of America., Cited By (since 1996):10, CODEN: JASMA, ,
Author: Van Parijs, Corkeron, Harvey, Hayes, Mellinger, Rouget, Thompson, Wahlberg, Kovacs
Date: 2003-01-01T00:00:00Z

Title: Tracking harbor seals (Phoca vitulina richardsi) to determine dive behavior, foraging activity, and haul-out site use
Description: Cited By (since 1996):27, Marine Mammals, Birds & Turtles Harbor Seals, CODEN: MMSCE
Author: Suryan, Harvey
Date: 1998-01-01T00:00:00Z

Title: Testing tag attachments to increase the attachment duration of archival tags on baleen whales
Description: As biologging technology has advanced to study whale behavior, various tag attachment methods have been developed. Suction cup attachments were developed for short-term (<24 h) studies using high-resolution archival tags, and implantable or dart attachments were developed for long-term (months) studies using coarse-resolution satellite tags. The purpose of this study was to test various tag attachment configurations to increase the deployment duration of archival tags while minimizing potential physical impacts to the whale.
Author: Szesciorka, Calambokidis, Harvey

Title: Biases associated with non-lethal methods of determining the diet of northern elephant seals,
Description: Cited By (since 1996):33, Export Date: 23 May 2014, , , ,
Author: Harvey, Antonelis
Date: 1994-01-01T00:00:00Z

Title: Acoustic evidence that harbor porpoises (Phocoena phocoena) avoid bottlenose dolphins (Tursiops truncatus)
Author: Jacobsen, Forney, Harvey

Title: Hair sampling location in harbor seals (Phoca vitulina) affects selenium and mercury concentrations: Implications for study design of trace element determination in pinnipeds
Description: Hair is used to determine trace elements exposure and status of pinnipeds because it is an excretory route for many elements and can be collected non-lethally. Despite increased use, there have been few studies on how sampling designs and procedures (e.g., hair type, collection site) affect results. The objective of this study was to determine whether concentrations of an essential (selenium; Se) and non-essential element (mercury; Hg) differed between hair samples collected from two body locations on harbor seals (Phoca vitulina). Concentrations of Se and total Hg (THg) differed between mid-dorsal midline and neck samples, and although the absolute differences were relatively small (Δabsolute Se=0.69μgg-1, Δabsolute THg=2.86μgg-1), the relative differences were large (Δrelative Se=49%, Δrelative THg=17%). These differences highlight the need to standardize the collection site for trace element determination in pinnipeds., Marine Mammals, Birds & Turtles Harbor Seals
Author: McHuron, Harvey, Castellini, O'Hara
Date: 2012-01-01T00:00:00Z

Title: Tidal movements of East Pacific green turtle Chelonia mydas at a foraging area in Baja California Sur, México,
Description: We tracked East Pacific green turtles Chelonia mydas using GPS-VHF telemetry in Estero Banderitas, a tidally-influenced foraging area in Bahía Magdalena, Baja California Sur, México. Tidal currents were measured with a bottom-mounted Acoustic Doppler Profiler (ADP) and the data used to predict tidal current speed and direction at the location and time during which turtles were tracked. Twenty-nine turtles were tracked in the summers of 2000 to 2003. Vagility (mean ± SD; 18.6 ± 11.4 km d-1) and speed (0.83 ± 0.47 km h-1) of turtles was the greatest so far reported for green turtles at foraging areas. Turtles displayed highly linear movements, and movement patterns were circatidal. Vector correlation was used to compare turtle speed and direction with tidal speed and direction. Correlation coefficients were significant for 11 out of 13 tracks, indicating significant linear interdependence between turtles and tides. Speed and direction contributed equally to the correlation. Results indicated a new paradigm for green turtles in feeding areas, where turtles are transported on continual tides that allow them to exploit a patchy and seasonal distribution of algae, their main diet component. This tidal transport is markedly different than Selective Tidal Stream Transport, in which animals use either the ebb or flood tide for transport. Tidal currents may be an accurate indicator of turtle movement in tidal areas, and this transport system has implications for foraging ecology, energetics, and growth. © Inter-Research 2009., Cited By (since 1996):8, Marine Mammals, Birds & Turtles, CODEN: MESED, ,
Author: Brooks, Harvey, Nichols
Date: 2009-01-01T00:00:00Z

Title: Book review: Otolith Atlas of Southern African Marine Fishes,
Description: , , ,
Author: Harvey, Yoklavich
Date: 1996-01-01T00:00:00Z

Title: Two sightings following release of rehabilitated harbor seals,
Description: , , ,
Author: Harvey, Brown, Mate
Date: 1983-01-01T00:00:00Z

Title: Assessing the relationship between gulls Larus spp. and Pacific salmon in central California using radiotelemetry
Description: Predation by marine birds has resulted in substantial losses to runs of Pacific salmon Oncorhynchus spp., in some cases necessitating management action. Recovery of PIT tages on a seabird breeding colony (Ano Nuevo Island) indicated that western gulls Larus occidentalis prey upon federally listed Coho Salmon Oncorhynchus kisutch and steelhead O. mykiss in central California. Whereas salmonid populations in central California have decreased in recent decades, the western gull population on Ano Nuevo Island has increased. We observed gulls Larus spp. within estuaries to document predation and used radiotelemetry to examine gull movement in relation to the availability of salmonids. During 2008 and 2009, observed predation events of out-migrating salmonids by gulls were rare; 21 events occurred during 338 h of observations at two estuaries. During the prehatch and chick-rearing phases of breeding, which coincided with migration of salmonids from fresh to salt water, 74% of the detections of radio-tagged western gulls occurred within 25 km of Ano Nuevo Island, suggesting that the relative susceptibility of predation by western gulls using Ano Nuevo Island decreased with distance from the island. Western gull presence at creek mouths was greatest during daylight hours (91% of detections), while juvenile salmonids were present predominantly at night (65% of detections). The greatest overlap between western gulls and salmonids occurred at dusk, and predation of out-migrating salmonids was likely opportunistic. Deterring gulls from creek mouths when overalp between predation and prey might otherwise occur may buffer out-migrating salmonids from predation. Our results will inform management strategies to most effectively reduce the impacts of gull predation on central California salmonids.
Author: Frechette, Osterback, Hayes, Moore, Shaffer, Pavelka, Winchell, Harvey
Date: 2015-01-01T00:00:00Z

Title: Aquatic mating strategies of the male pacific harbor seal (Phoca vitulina richardii),
Description: Compared to the harem and resource defense systems of terrestrial mating pinnipeds, males of aquatic mating species appear unable to monopolize females or resources. We investigated movements, acoustics, and aquatic territorial behavior of male harbor seals, Phoca vitulina richardii, in Elkhorn Slough, California, using VHF telemetry, hydrophones, and acoustic playback experiments. During the mating season 22 males increased time spent in the water and away from haul-out locations, exhibiting activity patterns similar to Atlantic subspecies. Two acoustic display patterns were observed. At one location multiple males aggregated to display with acoustic activity peaking one month before peak estrus. At two other locations, lone males displayed primarily during peak estrus. Acoustic display areas were non-adjacent with a mean ± SE size of 4,228 ± 576 m2, similar to harbor seal display patterns in the Moray Firth, Scotland. Underwater playbacks of male vocalizations were used to define territorial boundaries by inducing responses from territory-holding males. Four solitary males defended adjacent territories (mean area 39,571 ± 18,818 m2) along a travel corridor, similar to observations of harbor seals at Miquelon, Newfoundland. Acoustic display stations appeared to be subcomponents of larger territories. Males exhibited site fidelity to territories for at least 2-A yr. Females moved through territories freely. The establishment of male-display territories along female-traffic corridors resembles terrestrial systems described as hotspot leks., Cited By (since 1996):15, Marine Mammals, Birds & Turtles, CODEN: MMSCE, ,
Author: Hayes, Costa, Harvey, Le Boeuf
Date: 2004-01-01T00:00:00Z

Title: A new attachement device for radio-tagging large whales,
Description: , , ,
Author: Mate, Harvey, Hobbs, Maiefeski
Date: 1983-01-01T00:00:00Z

Title: The acoustic identification and enumeration of scyphozoan jellyfish, prey for leatherback sea turtles (Dermochelys coriacea), off central California
Description: Acoustic-sampling techniques were developed to estimate the abundance and distribution of scyphozoan jellyfish, prey for leatherback turtles foraging off central California. Acoustic data were analysed from regions where jellyfish were present or absent from corresponding net tows. Empirical data on bell-diameter distribution (mean 26.2 cm; s.d. 10.6) were used to estimate target strength (TS; dB re 1 m 2) at 18, 38, 70, 120, and 200 kHz using a distorted-wave Born approximation scattering model. TS measurements of in situ animals at 38 and 200 kHz averaged -63.9 and -70.5 dB, compared with the model estimates of -54.9 and -64.0 dB, respectively. The model estimates of TS at 18, 70, and 120 kHz were -53.9, -59.9, and -61.8 dB, respectively. Using these TS estimates, an algorithm was developed to extract jellyfish echoes from total acoustic backscatter. Echo-integration methods applied to regions where net catches contained jellyfish resulted in an estimate of mean numerical abundance of 3217 jellyfish (s.d. 2276) with a mean density of 251 522 jellyfish nautical mile -2 (s.d. 57 504) and a mean concentration of 0.003 jellyfish m -3 (s.d. 0.002). The novel methods developed will help characterize prey resources for leatherback turtles off central California. © United States Government, National Oceanographic and Atmospheric Administration 2010., Cited By (since 1996):5, Invertebrates, Marine Mammals, Birds & Turtles, CODEN: ICESE
Author: Graham, Harvey, Benson, Renfree, Demer

$Nitrogen isotope fractionation in amino acids from harbor seals: Implications for compound-specific trophic position calculations$

Title: Nitrogen isotope fractionation in amino acids from harbor seals: Implications for compound-specific trophic position calculations
Description: Compound-specific isotope analysis of individual amino acids (AA) is a rapidly growing tool in ecological studies to assess diet and trophic position (TP) in both modern and ancient foodwebs. We conducted the first controlled feeding study examining δ15N values in AAs in a marine mammal (harbor seal Phoca vitulina). The pattern of δ15N variation among AAs in seals was similar to that observed in other heterotrophs, although exceptions were found with proline and threonine. However, many δ15N changes with trophic transfer were very different than those reported for zooplankton and other lower TP marine consumers. In particular the measured trophic enrichment factor (TEF) now broadly used for TP estimation (TEFGlu-Phe) was much lower in harbor seals (̃4.3%) than the current commonly applied value (̃7.5%). Recently published data on wild marine birds (penguins) and elasmobranchs (stingrays) suggests that similar, low TEF values may also be characteristic of these taxa. Together, these data imply that marine mammals and other higher animals have different, but also diagnostic, changes in δ15N-AA with trophic transfer vs. organisms examined in previous feeding studies (e.g. zooplankton, bony fish and mollusks), possibly due to dietary protein content, trophic position, and/or form of nitrogen excretion (urea vs. ammonia). Therefore, we propose that for marine mammals, a multi-TEF calculation is required to account for variations of TEF between animals within a food web, and we demonstrate that this approach can predict accurate TP estimates for harbor seals. These results also have significant implication for the application of compound-specific isotope analysis of AAs on terrestrial ecology and trophic structure. © Inter-Research 2013.
Author: Germain, Koch, Harvey, McCarthy
Date: 2013-01-01T00:00:00Z

Title: Genetic substructure of the pacific harbor seal (Phoca vitulina richardsi) off Washington, Oregon, and California
Description: Genetic substructure among groups of Pacific harbor seals, Phoca vitulina richardsi, along the western coast of the United States was investigated using mitochondrial DNA sequences. Blood and tissue samples were removed from 86 seals inhabiting Puget Sound and the Pacific coasts of Washington, Oregon, and California. A 320 base-pair segment of the control region was amplified using the polymerase chain reaction and directly sequenced. These data indicated a high level of diversity. Thirty variable sites were found that define 47 mitochondrial haplotypes. Among groups of P. v. richardsi sampled, 5 haplotypes were shared, but most (42) were unique to a locality. Haplotypic frequency and an Analysis of Molecular Variance (AMOVA) revealed significant differences (P = 0.001) among regions. Phylogenetic analysis indicated Puget Sound seals possess unique divergent lineages not found in seals from the coasts of Washington, Oregon, and California. These lineages may represent haplotypes from north of Washington, which is consistent with late reproductive timing of harbor seals from Puget Sound., Cited By (since 1996):19, CODEN: MMSCE, Marine Mammals, Birds & Turtles Harbor Seals
Author: Lamont, Vida, Harvey, Jeffries, Brown, Huber, Delong, Thomas
Date: 1996-01-01T00:00:00Z

Title: Determining a correction factor for aerial surveys of harbor seals in California
Description: Counts of pinnipeds provide a minimal estimate of population size because some unknown proportion of individuals is in the water during surveys. We determined a correction factor (CF) for Pacific harbor seals (Phoca vitulina richardii) by estimating the proportion ashore of 180 seals tagged with flipper-mounted radio tags throughout California. The mean proportions of tagged individuals ashore during four complete surveys in 2004 were not different between central and northern California (F= 1.85, P= 0.18) or between sexes (F= 0.57, P= 0.45), but a lesser proportion of weaners was ashore than subadults or adults (F= 7.97, P= 0.001), especially in northern California. The CF calculated for the statewide census of harbor seals was 1.65, using transmitters operating during the survey (n= 114). Using a mark-recapture estimator for tag survival (phi) and the four telemetry surveys the mean CF for central and northern California was 1.54 ± 0.38 (95% CI). A CF for southern California of 2.86 was based on a single survey. Using the mean CF of 1.54 and a statewide count in 2009 we estimated 30,196 (95% CI = 22,745-37,647) harbor seals in California., Cited By (since 1996):3, CODEN: MMSCE
Author: Harvey, Goley
Date: 2011-01-01T00:00:00Z

Title: Selenium and mercury concentrations in harbor seals (Phoca vitulina) from central California: Health implications in an urbanized estuary
Description: We measured total selenium and total mercury concentrations ([TSe] and [THg]) in hair (n = 138) and blood (n = 73) of harbor seals (Phoca vitulina) from California to assess variation by geography and sex, and inferred feeding relationships based on carbon, nitrogen, and sulfur stable isotopes. Harbor seals from Hg-contaminated sites had significantly greater [THg], and lesser [TSe] and TSe:THg molar ratios than seals from a relatively uncontaminated site. Males had significantly greater [THg] than females at all locations. Sulfur stable isotope values explained approximately 25% of the variability in [THg], indicating increased Hg exposure for seals with a greater use of estuarine prey species. Decreased [TSe] in harbor seals from Hg-contaminated regions may indicate a relative Se deficiency to mitigate the toxic effects of Hg. Further investigation into the Se status and the potential negative impact of Hg on harbor seals from Hg-contaminated sites is warranted. © 2014 Elsevier Ltd., Harbor Seals
Author: McHuron, Harvey, Castellini, Stricker, O'Hara

Title: Chronic oiling of marine birds in California by natural petroleum seeps, shipwrecks, and other sources
Description: We assessed temporal and spatial patterns of chronic oiling of seabirds in California during 2005-2010, using data on: (1) live oiled birds reported to the Oiled Wildlife Care Network (OWCN) from throughout the state, and (2) dead oiled birds found during systematic monthly beached-bird surveys in central California. A mean of 245 (±141 SD) live miscellaneous oiled birds (not associated with known oil spills) were reported to the OWCN per year, and 0.1 oiled dead birds km-1 per month were found on beach surveys in central California. Chemical fingerprinting of oiled feathers from a subset of these birds (n = 101) indicated that 89% of samples tested were likely from natural petroleum seeps off southern and central California. There was a pronounced peak during late winter in the number of oiled birds reported in southern California, which we theorize may be related to large storm waves disturbing underwater seeps. © 2013., Marine Mammals, Birds & Turtles, Article in Press
Author: Henkel, Nevins, Martin, Sugarman, Harvey, Ziccardi
Date: 2014-01-01T00:00:00Z

Title: Diving behavior of the Pacific harbor seal (Phoca vitulina richardii) in Monterey Bay, California
Description: Physical environment and physiological characteristics of marine mammals potentially affect the duration and depth of diving. Härkönen (1987b) proposed a hypothesis that the harbor seal would gain maximum energy by foraging at intermediate depths. To investigate this hypothesis, we studied diving behavior of the Pacific harbor seal (Phoca vitulina richardii) during 1995 through 1997 in Monterey Bay, California. Dive depths (n = 13,063 dives) were recorded via time-depth recorders. Approximately 80% of recorded dives were classified as square dives (type I), which typically were associated with foraging in pinnipeds. Approximately 11% of dives were V dives (type II; 1,402 dives), and the remainder (1,225 dives) were skewed dives (type III and IV). The deepest recorded dive was 481 m, while the greatest duration was 35.25 min. Body mass explained the variability of durations of long dives for females (95th percentile; D95,♀ = -5.47 + 0.18 × (mass ♀), r2 = 0.91, 95% CI for slope = [0.08, 0.28], n = 5) and for males (D95,♂ = -5.86 + 0.18 × (mass ♂), r2 = 0.83, 95% CI for slope = [0.12, 0.24], n = 11). The large proportion of variability in deep dives, however, was explained by body mass only for males (95th percentile; Z95,♂ = -363.9 + 6.05 × (mass♂), r2 = 0.83, 95% CI for slope = [3.93, 8.17], n = 11) and not for females (Z95,♀ = -148.1 + 3.11 × (mass♀), r2 = 0.58, 95% CI for slope = [-1.7, 7.9], n = 5, 95% CI for slope = [-1.7, 7.9]). Median depths of presumed foraging dives of harbor seals in the Monterey Bay area were between 5 and 100 m, which were within the range of the previously reported depths for other areas (<100 m). Our findings generally supported Härkönen's hypothesis that harbor seals forage in the intermediate depth in their environment. © 2005 by the Society for Marine Mammalogy., Cited By (since 1996):5, Marine Mammals, Birds & Turtles Harbor Seals, CODEN: MMSCE
Author: Eguchi, Harvey
Date: 2005-01-01T00:00:00Z

Title: Quantifying errors associated with using fecal samples to determine the diet of the California sea lion (Zalophus californianus),
Description: Cited By (since 1996):33, Export Date: 2 June 2014, We examined the digestion and passage times of bones and other hard parts from pollock, herring, salmon, and sandlance recovered from two juvenile captive Steller's sea lions (Eumetopias jubatus) subjected to varying activity levels. Key bones that could be identified to species were distributed over an average of 3.2 scats (range 1–6) following a single meal, with pollock remains occurring in significantly more scats than other species. Relying on otoliths alone to determine the presence of prey resulted in significantly fewer prey being identified than if other structures were also used (such as vertebrae, jaw bones, and teeth), particularly for salmon. Using either technique, there were significant differences in the likelihood that bones would be recovered from the series of scats produced following a meal, with pollock recovery exceeding herring (by three-fold) and sandlance (by eight-fold). Differences between species were reduced when recovery was calculated on a per scat basis rather than over multiple scats. Active animals passed greater numbers of bones, but the overall effect on prey recovery estimates was not significant. Defecation times of prey structures from a meal were variable and ranged from an initial 2–56 h to a final 28–148 h. The time interval to pass 95% of recovered structutes varied by a factor of two among prey species, and was highest for pollock due to retention beyond 65 h., ,
Author: Orr, Harvey
Date: 2001-01-01T00:00:00Z

Title: Foraging behavior of humpback whales: Kinematic and respiratory patterns suggest a high cost for a lunge,
Description: Lunge feeding in rorqual whales is a drag-based feeding mechanism that is thought to entail a high energetic cost and consequently limit the maximum dive time of these extraordinarily large predators. Although the kinematics of lunge feeding in fin whales supports this hypothesis, it is unclear whether respiratory compensation occurs as a consequence of lunge-feeding activity. We used high-resolution digital tags on foraging humpback whales (Megaptera novaengliae) to determine the number of lunges executed per dive as well as respiratory frequency between dives. Data from two whales are reported, which together performed 58 foraging dives and 451 lunges. During one study, we tracked one tagged whale for approximately 2h and examined the spatial distribution of prey using a digital echosounder. These data were integrated with the dive profile to reveal that lunges are directed toward the upper boundary of dense krill aggregations. Foraging dives were characterized by a gliding descent, up to 15 lunges at depth, and an ascent powered by steady swimming. Longer dives were required to perform more lunges at depth and these extended apneas were followed by an increase in the number of breaths taken after a dive. Maximum dive durations during foraging were approximately half of those previously reported for singing (i.e. non-feeding) humpback whales. At the highest lunge frequencies (10 to 15 lunges per dive), respiratory rate was at least threefold higher than that of singing humpback whales that underwent a similar degree of apnea. These data suggest that the high energetic cost associated with lunge feeding in blue and fin whales also occurs in intermediate sized rorquals., Cited By (since 1996):31, CODEN: JEBIA, ,
Author: Goldbogen, Calambokidis, Croll, Harvey, Newton, Oleson, Schorr, Shadwick
Date: 2008-01-01T00:00:00Z

Title: Diet of a piscivorous seabird reveals spatiotemporal variation in abundance of forage fishes in the Monterey Bay region
Description: Brandt's Cormorant (Phalacrocorax penicillatus) diet was investigated using regurgitated pellets (n = 285) collected on 19 sampling days at three locations during the 2006-07 and 2007-08 nonbreeding seasons in the Monterey Bay region. The efficacy of using nested sieves and the all-structure technique to facilitate prey detection in the pellets was evaluated, but this method did not increase prey enumeration and greatly decreased efficiency. Although 29 prey species were consumed, northern anchovy (Engraulis mordax) dominated and speckled sanddab (Citharichthys stigmaeus) also was important in the diet. Few rockfishes (Sebastes spp.) and market squid (Doryteuthis opalescens) were consumed compared with great prevalence in previous studies during the 1970s. El Niño and La Niña during the study provided a unique opportunity to examine predator response to variation in prey availability. Patterns of prey number and diversity were not consistent among locations. Greatest number and diversity of prey occurred at locations within Monterey Bay during La Niña, results not evident at the outer coast location. Short-term specialization occurred but mean prey diversity indicated a generalist feeding mode. This study demonstrated the importance of periodic sampling at multiple locations within a region to detect spatiotemporal variability in the diet of opportunistic generalists.
Author: Webb, Harvey

Title: Diet estimation in California sea lions, Zalophus californianus
Description: We performed a captive feeding experiment using California sea lions to assess biases associated with estimating pinniped diet using scats and spews. Sea lions were fed nine of their natural prey species: anchovy, sardine, Pacific mackerel, jack mackerel, hake, steelhead smolts, shortbelly rockfish, pink salmon, and market squid. Recovery percentages varied among prey species using otoliths and were improved for adult salmon and sardine using the all-structure method. Numerical and graded length correction factors provided better estimates of number and size of prey consumed. Four models used to determine the proportions of prey species consumed by a sea lion population were tested. The all-structure method and variable biomass reconstruction model, in conjunction with numerical and graded length correction factors, provided more accurate estimates than without. We provide numerical correction factors for all prey species, including correction factors for specific salmon bones: vertebrae, branchials, radials, teeth, gill rakers, and hypurals. © 2011 by the Society for Marine Mammalogy., Cited By (since 1996):2, Marine Mammals, Birds & Turtles, CODEN: MMSCE
Author: Sweeney, Harvey

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