COUNTING STELLER SEA LION PUPS IN ALASKA: AN EVALUATION OF MEDIUMFORMAT, COLOR AERIAL PHOTOGRAPHY

Estimates of Steller sea lion ( Eumetopias jubatus ) pup production are valuable for estimating population trend and size. Currently in Alaska, pups are counted by visiting rookeries, driving older animals into the water, then walking through the rookeries and counting the pups, a highly disruptive procedure. At smaller rookeries, with good vantage points, pups are occasionally counted from the periphery of rookeries without disturbing the sea lions. We evaluated counts made from medium-format, color, aerial photographs as an alternative to drive counts and peripheral counts. Neither the peripheral counts nor the aerial photographic counts disturbed animals on the rokeries. There were strong 1:1 linear relationships between photographic counts and drive counts ( r ²= 0.966, P < 0.001) and between photographic counts and peripheral counts ( r ²= 0.999, P < 0.001). Precision was similar for all three methods of counting. We suggest that medium-format, color, aerial photographs is appropriate for routine surveys of Steller sea lion pups in Alaska because it is not disruptive to the hauled-out sea lions and provides comparable estimates with similar precision to drive and peripheral counts. Large areas canbe rapidly surveyed during periods of good weather with a minimum of manpower.     

COMPARISON OF VERTICAL AERIAL PHOTOGRAPHIC AND GROUND CENSUSES OF STELLER SEA LIONS AT AÑO NUEVO ISLAND, JULY 1990-1993

Counts of Steller sea lion ( Eumetopias jubatus ) pups and non-pups (adults and juveniles) from aerial photographs of rookeries at Año Nuevo Island between 1990 and 1993 were significantly higher than those made on the ground. Based on regression of natural logs of photographic counts versus year, the number of pups declined at a rate of −0.099yr while non-pup numbers declined at −0.315/yr. Examination of ground count data for the same period revealed a significant decline in non-pups (−0.139/yr), but no trend was detected in the ground counts of pups. The regression coefficients from photographic and ground counts of non-pups did not differ significantly. Power analyses using the program TRENDS indicated that detectable rates of change in abundance from four annual surveys were much lower for counts of pups than counts of non-pups where sampling precision was based on fits to linear models.     

Bias in aerial estimates of the number of nests in White Ibis and Great Egret colonies

ABSTRACT Estimating detection error, as well as the magnitude of other potential survey biases, is essential when sampling efforts play a role in the estimation of population size and management of wildlife populations. We quantified visual biases in aerial surveys of nesting wading birds (Ciconiiformes) in colonies in the Florida Everglades using a negative binomial count regression model to compare numbers of nests in quadrats counted on the ground with numbers estimated from aerial photographs of the same quadrats. The model also allowed the determination of degree of difference between monitoring results based upon such factors as nest density, vegetative cover, and nest turnover rates. Aerial surveys of White Ibis (Eudocimus albus) colonies underestimated the true number of nests found during ground counts by 11.1%, and underestimates were significantly greater (P= 0.047) in a colony with high nest turnover. Error rates did not differ for quadrats that varied in the density of White Ibis nests did not differ, and visual bias did not increase with vegetative complexity (P= 0.73). Estimates of nest density in colonies of Great Egrets (Ardea alba) based on aerial surveys were higher than ground counts for 38% of the quadrats sampled, and mean visual bias was 23.1%. Species misidentification likely contributed to visibility bias for Great Egrets in our study, with some Snowy Egrets almost certainly mistaken for Great Egrets in aerial photos. Biases of the magnitude we observed fro Great Egrets and White Ibises can mask true population trends in long‐term monitoring and, therefore, we recommend that detection probability be explicitly evaluated when conducting aerial surveys of nesting birds.     

Nest and breeding population abundance of Least Terns: assessing bias and variation in survey timing and methods

Methods commonly used to estimate the number of nests and size of the breeding population at colonies of Least Terns (Sternula antillarum) and other waterbirds include walk‐through counts of nests (ground‐nest counts) and counts of incubating adults from the colony perimeter (incubating‐adult counts). The bias and variance of different methods and the comparability of repeated surveys versus once‐annual censuses are poorly understood. Our objectives were to assess (1) the potential bias and variation of the more rapid incubating‐adult counts compared to the time‐intensive, and presumably more accurate, ground‐nest counts, and (2) how accurately a once‐annual census captured peak nesting abundance. We studied nine Least Tern colonies at Cape Lookout National Seashore (CALO), North Carolina, from April to August 2010–2012. We analyzed observer and survey method agreement with concordance correlation coefficients (ρ_c). We deployed time‐lapse cameras at 156 nests and used repeated‐measures logistic regression to determine if the proportion of time spent incubating varied with colony, time of day, or time of season. We found substantial agreement in abundance estimates of Least Tern nests and incubating adults between observers and survey methods, and among different times of day and seasons (all comparisons ρ_c > 0.97). Least Terns incubated eggs 94% of the time on average during daylight hours, irrespective of colony, nesting stage, or month. Although the nesting peak at CALO occurred during the recommended census period for Least Terns, abundance estimates for surveys conducted at different times during that period varied by as much as 39%. We recommend conducting incubating‐adult counts to estimate nest and breeding population abundance of Least Terns or other waterbirds when vegetation or dunes do not obstruct views of nesting colonies. In addition, given the variation in abundance estimates for surveys conducted at different times during the recommended survey period, incubating‐adult counts should be performed at least twice during the census period, with the maximum count reported as peak nest abundance.     

Estimating the relative abundance of emperor penguins at inaccessible colonies using satellite imagery

Emperor penguin (Aptenodytes forsteri) populations are useful environmental indicators due to the bird’s extreme reliance on sea ice. We used remote sensing technology to estimate relative adult bird abundance at two inaccessible emperor penguin colonies in the Ross Sea, Antarctica. We performed supervised classification of 12 panchromatic satellite images of the seven known Ross Sea colonies. We used regression to predict adult bird counts at the inaccessible colonies by relating the number of pixels classified as “penguin” in the satellite images of the accessible colonies to corresponding known adult bird counts from aerial photographs or ground counts. While our analysis was hampered by excessive guano and shadows, we used satellite imagery to differentiate between relatively small (<3,000 adult birds) and larger colonies (>5,000 adult birds). Remote sensing technology is logistically less intense and less costly than aerial or ground censuses when the objective is to document penguin presence and/or large emperor penguin population changes (e.g., catastrophic changes). Improvements expected soon in the resolution of the satellite images should allow for more accurate abundance estimates.     

The use of block counts,mark-resight and distance sampling to estimate population size of a mountain-dwelling ungulate

Population size estimates represent indispensable tools for many research programs and for conservation or management issues. Mountain ungulates in open areas are often surveyed through ground counts that normally underestimate population size. While the use of sample counts is desirable, few studies have compared different probabilistic approaches to estimate population size in this taxon. We compared the size estimates of a male population of Alpine chamois using mark-resight and line transect sampling methods, while block counts were used to obtain the minimum number of males alive in the study area. Surveys were conducted within the Gran Paradiso National Park (Italy), in August–September 2013, using block counts along purposely selected trails and vantage points, mark-resight over 5 consecutive resightings from vantage points and trails, and line transect sampling along 12 transects repeated 8 times. Block counts yielded a minimum number of males alive in the population of n = 72 individuals. This value was greater than the upper bound of the 95 % confidence interval achieved using line transect sampling {n = 54, CV = 14 % [95 % CI (40, 71)]} while mark-resight yielded a more realistic result of n = 93 individuals {CV = 18 % [95 % CI (63, 137)]}. Our results suggest that line transect sampling performed poorly in the Alpine environment, leading to underestimates of population size, likely due to violations of some assumptions imposed by the rugged nature of the terrain. The mark-resight yielded lower precision, possibly due to the limited number of marked individuals and resighting occasions, but it provided robustness and accurate estimates as marks were evenly distributed among animals.     

Comparison of census methods for black-browed albatrosses breeding at the Ildefonso Archipelago,Chile

A breeding population of black-browed albatrosses has been known to exist at the Ildefonso Archipelago, Chile, for >90 years but the population has never been censused using scientifically defendable methods. To estimate population size, and examine the accuracy and practicality of various census methods, the population was censused in the 2002/2003 breeding season using (a) ground-truthed aerial photography, (b) yacht-based photography, (c) ground counts, (d) quadrat sampling and (e) point-distance sampling. Compared to ground-truthed aerial photography (judged the most accurate) yacht-based photography underestimated population size by 55%, ground counts by 13%, quadrat sampling by 11% and point-distance sampling by 9%. Ground-truthed air photography revealed that in the 2002/2003 breeding season 47,000 pairs of black-browed albatrosses bred at the Ildefonso Archipelago. A repeat aerial census in 2006 suggested the size of the breeding population had not changed in the 4 years between the two censuses. After the Falkland Islands/Islas Malvinas, South Georgia and Diego Ramirez, the Ildefonso Archipelago holds the fourth largest population of black-browed albatrosses in the world.     

A comparison of methods used to count the elephant population of the Addo Elephant National Park, South Africa

Evaluation of alternative techniques used to estimate elephant population sizes is important in order to assess the accuracy of the results obtained, upon which management decisions may be based. Data from annual helicopter surveys carried out in the Addo Elephant National Park (1978–97) are compared with registration counts obtained from intensive ground surveys in which all elephants within the park are individually known. On average, total population size estimated in aerial surveys is 8.0% lower than registration counts (n₁₉₉₇ = 251), aerial calf (< 1 year) counts are 48.8% lower than registration counts, and aerial carcass counts are 50% below the total number of deaths documented in ground surveys. Registration counts provide more accurate demographic data than aerial surveys, the results of which are shown to vary widely and unpredictably, thus compromising their value. Where population estimates rely exclusively on aerial surveys, replicate counts are recommended in order to generate confidence intervals.     

Assessing the accuracy of plotless density estimators using census counts to refine population estimates of the vultures of Kruger National Park

Breeding population estimates for three vulture species in Kruger National Park (KNP), South Africa, were made in 2013 using data from aerial censuses and a plotless density estimator (PDE). PDEs are distance-based methods used to assess sparse populations unsuitable for plot-based methods. A correction factor was applied to the 2013 estimates to reflect the difference between the survey counts and the PDE figures. We flew additional censuses across most of KNP and counted all visible nests to assess the 2013 estimates. Survey counts were within 95% confidence limits of corrected PDE estimates for White-backed Vulture Gyps africanus (count: 892; estimate: 904 [95% CI ±162]), at the limit of confidence for White-headed Vulture Trigonoceps occipitalis (count: 48; estimate: 60 [±13]) and outside confidence limits for Lappet-faced Vulture Torgos tracheliotos (count: 44; estimate: 78 [±18]). Uncorrected PDE estimates accurately reflected White-headed and Lappet-faced Vulture nest counts. The clustered patterns of White-backed Vulture nests and dispersed patterns of White-headed and Lappet-faced Vulture nests offer an explanation for these results and means that corrected PDE densities are inaccurate for estimating dispersed nests but accurate for estimating clustered nests. Using PDE methods, aerial surveys over ～35% of KNP are probably sufficient to assess changes in these vulture populations over time. Our results highlight these globally important breeding populations.     

Predicting the grass pollen count from meteorological data with regard to estimating the severity of hayfever symptoms in Melbourne (Australia)

In Melbourne, Australia, grass pollen is the predominant cause of hayfever in late spring and summer. The grass pollen season has been monitored in Melbourne, using a Burkard spore trap, for 13 years (1975–1981, 1985 and 1991–1997). Total counts for grass pollen were highly variable from one season to the next (approximately 1000 to >8000 grains/m³). The daily grass pollen counts also showed a high variability (0 to approximately 400 grains/m³). In this study, the grass pollen counts of the 13 years (12 grass pollen seasons, extending from October to January) have been compared with meteorological data in order to identify the conditions that can determine the daily amounts of grass pollen in the air. It was found that the seasonal total of grass pollen was directly correlated with the rainfall sum of the preceding 12 months (1 September–31 August): seasonal total of grass pollen (counts/m³)=18.161 × rainfall sum of the preceding 12 months (mm) −8541.5 (r _s=0.74,P<0.005,n=12). The daily amounts of grass pollen in the air were positively correlated with the corresponding daily average ambient temperatures (P<0.001). The daily amount of grass pollen which was to be expected with a certain daily average temperature was linked to the seasonal total of grass pollen: in years with high total grass pollen counts, a lower daily average temperature was required for a high daily pollen count than in years with low total grass pollen counts. As the concentration of airborne grass pollen determines the severity of hayfever in sensitive patients, an estimation of daily grass pollen counts can provide an indication of potential pollinosis symptoms. We compared daily grass pollen counts with the reported symptomatic responses of hayfever sufferers in November 1985 and found that hayfever symptoms were significantly correlated to the grass pollen counts (P<0.001 for nasal,P<0.005 for eye symptoms). Thus, a combination of meteorological information (i.e. rainfall and temperature) allows for an estimation of the potential daily pollinosis symptoms during the grass pollen season. Here we propose a symptom estimation chart, allowing a quick prediction of eye and nasal symptoms that are likely to occur as a result of variations in meteorological conditions, thus enabling both physicians and patients to take appropriate avoidance measures or therapy.     

Statistical power of replicated helicopter surveys in southern African conservation areas

Understanding the ecology of large ungulates in southern Africa requires accurate and precise measures of population size. Recovery or exploitation of ungulates in reserves is currently instigated when population size changes exceed 15% per annum, but monitoring is usually undertaken with single counts from helicopters, for which precision and the power to detect change are untested. In essence, power being the strength of a monitoring result in showing change over time. Retrospective power analysis is a useful technique to investigate the variability of single‐count aerial surveys. Using replicated helicopter‐based counts of southern African ungulates and post hoc analysis, we investigated the power of currently used single‐count surveys across five common ungulate species and 11 wildlife reserves. We expected high variability in count data and set α = 0.1 and 0.2 (α being the type I error rate), and asked two questions: ‘How much does power vary in replicated aerial counts of southern African wildlife across reserves and species?’ and ‘Can current single‐count aerial surveys detect population changes in response to management actions or are the statistical errors intractable?’ Single counts were mostly unreliable; only one of 42 had sufficient power to detect meaningful changes in population size or their trends at α = 0.1, and only three had sufficient power at α = 0.2. Power varied widely according to species (e.g. warthog, median power at α = 0.1; 0.12–0.37: blue wildebeest, median power at α = 0.1; 0.23–0.74), and, within species, between replicates and reserves. Our retrospective calculations demonstrated insensitivity and ineffectiveness in most currently applied single counts from helicopters. Consequently, it is impossible to interpret the effects of ungulate conservation actions on many southern African reserves. Retrospective power analyses enables determination of which previous aerial surveys were useful for population assessment and adaptive management, and which should be discarded. We recommend that prospective power analyses are undertaken to determine future helicopter survey sample size and replication requirements, especially in small reserves.     

Increasing Himalayan tahr and decreasing chamois densities in the eastern Southern Alps, New Zealand: evidence for interspecific competition

There is anecdotal evidence that increasing densities of Himalayan tahr (Hemitragus jemlahicus) are associated with declining densities of chamois (Rupicapra rupicapra) in the Southern Alps, New Zealand. To examine this phenomenon, densities of tahr and chamois were measured at 53 sites within their sympatric range in the eastern Southern Alps during 1978–1979. In sites where only one species was present, tahr density was significantly higher than chamois density (P=0.032), probably reflecting species differences in sociality. Chamois density was higher in catchments without tahr than in those with tahr (P=0.012). Similarly, tahr density was significantly higher at sites without chamois than at those with chamois (P=0.033). Sites with both species present (termed sympatric) were significantly larger than those with only chamois or tahr (P<0.001). Following the prohibition of aerial hunting of tahr in 1983, 16 of the 17 sites where tahr and chamois were sympatric during 1978–1979 were recounted during 1991–1996. There was a 6-fold increase in the mean density of tahr between the two counts (P=0.001), whereas chamois density had declined significantly (P=0.006). Chamois persisted at only three sites, two of which had the highest chamois densities in 1978–1979. This is evidence that increasing densities of tahr exclude chamois from all but the `best' habitats. We conclude that intensive aerial hunting of tahr during 1967–1983 reduced tahr densities such that chamois could co-exist with tahr. Received: 20 March 1997 / Accepted: 8 September 1997     

Vegetation changes during a 36-year period in northern Chobe National Park, Botswana

Changes in vegetation cover in northern Chobe National Park (Botswana) were assessed using aerial photographs from 1962, 1985 and 1998, with subsequent ground proofing. In addition, cumulative browsing by elephants and the occurrence of fire scars were recorded on random vegetation sites within shrubland (n = 20) and mixed woodland (n = 20). Coverage of woodland vegetation decreased from 60% to 30% between 1962 and 1998, while shrubland vegetation increased from 5% to 33% during the same period. During the study period, woodland has gradually retreated away from the river front. While riparian forest covered a continuous area along the riverfront in 1962, only fragments were left in 1998. We found a significant decrease in browse use with increasing distance to the Chobe river for Combretum apiculatum, Combretum elaeagnoides, Combretum mossambicense and other woody plants combined (all P < 0.0001). The occurrence of fire (P < 0.0001) and basal area (P < 0.0001) were positively related to distance to the river. Elephant browsing occurred on >70% of available stems within 2 km from the river, while less than 20% of the trees had fire scars in the same zone. Beyond 7 km from the river, elephant browsing was reduced to >50% of available stems, while more than 50% of the trees had fire scars. The density of any of the shrubs was not related to distance to the river neither within shrubland (all P > 0.05) nor within mixed woodlands (all P > 0.05).     

Satellite imagery can be used to detect variation in abundance of Weddell seals (Leptonychotes weddellii) in Erebus Bay, Antarctica

The Weddell seal population in Erebus Bay, Antarctica, represents one of the best-studied marine mammal populations in the world, providing an ideal test for the efficacy of satellite imagery to inform about seal abundance and population trends. Using high-resolution (0.6 m) satellite imagery, we compared counts from imagery to ground counts of adult Weddell seals and determined temporal trends in Erebus Bay during November 2004–2006 and 2009, and December 2007. Seals were counted from QuickBird-2 and WorldView-1 images, and these counts were compared with ground counts at overlapping locations within Erebus Bay during the same time. Counts were compared across years and within individual haul-out locations. We counted a total of 1,000 adult Weddell seals from five images across all years (for a total of 21 satellite-to-ground count comparisons), approximately 72% of the total counted on the ground at overlapping locations. We accurately detected an increase in abundance during 2004–2009. There was a strong, positive correlation (r = 0.98, df = 3, P < 0.003) between ground counts and counts derived from the imagery. The correlation between counts at individual haul-out locations was also strong (r = 0.80, df = 19, P < 0.001). Detection rates ranged from 30 to 88%. Overall, our results showed the utility of high-resolution imagery to provide an accurate way to detect the presence and variation in abundance of Weddell seals. Our methods may be applied to other species in polar regions, such as walruses or polar bears, particularly in areas where little is known about population status.     

DISTRIBUTION AND POPULATION SIZE OF THE SOUTHERN SEA LION (OTARIA FLAVESCENS) IN CENTRAL AND SOUTHERN CHUBUT,PATAGONIA, ARGENTINA

Population size and distribution of Otaria flavescens in central and southern Chubut, Patagonia were determined by aerial censuses conducted during the breeding season in 1989 and 1995 and outside the season. Pup numbers were corrected by means of a linear regression between pup and adult male (AM) numbers obtained from terrestrial censuses carried out in 1994 and 1996. During the 1989 breeding season, 10,557 sea lions occurred at 29 locations; 2,800 (26.3%) were pups. During the 1995 breeding season, 14,887 animals were censused at 32 sites; 3,311 (22.2%) were pups. The corrected pup number increased to 4,852, indicating that around 32% is lost when counting from photographs. The corrected total number increased to 16,483; this fell to less than one half between breeding seasons (November 1990 and 1995). The 1995 breeding season census represents the highest number since 1972 (8,800) and the widest historical dispersion (37 sites year round contrasting with 13 in the late 1940s and 1972). However, the present number is about one half of the 33,000 censused about 50 yr ago. Using a correction factor developed for the north Paragonian population (1.8 × censused number) the present population size in the area can be estimated at around 29,669 individuals.     

Protostelids from German Beech forests

A survey for protostelids from old-growth beech forests of northeastern Germany resulted in 14 species found in both ground and aerial litter, constituting the first survey of these organisms from Central Europe. Additionally the myxomycete Echinostelium bisporum was recorded as new for Germany. A detailed investigation of randomly sampled dead Fagus leaves (16 leaves on ground, 16 aerial leaves, three replicate cultures per leaf) resulted in 7 species; a hyperbolic regression of the respective species accumulation curve gives the theoretical value of 8.3 species. Protostelids occurred especially at aerial leaves with a high frequency (0.94). A program simulating random spore hits was written to calculate the minimum spore fallout necessary to explain this frequency. The resulting average value of about 3 spores per leaf can well be matched by the potential spore productivity estimated to be about 1000 spores per leaf for the most common species, Protostelium mycophaga.     

Effect of prey availability on the abundance of White‐breasted Wood‐Wrens,insectivorous birds of tropical lowland forests

Some understory insectivorous birds manage to persist in tropical forest fragments despite significant habitat loss and forest fragmentation. Their persistence has been related to arthropod biomass. In addition, forest structure has been used as a proxy to estimate prey availability for understory birds and for calculating prey abundance. We used arthropod biomass and forest structural variables (leaf area index [LAI] and aerial leaf litter biomass) to explain the abundance of White‐breasted Wood‐Wrens (Henicorhina leucosticta), tropical understory insectivorous birds, in six forests in the Caribbean lowlands of Costa Rica. To estimate bird abundance, we performed point counts (100‐m radius) in two old‐growth forests, two second‐growth forests, and two selectively logged forests. Arthropod abundance was the best predictor of wood‐wren abundance (wi = 0.75). Wood‐wren abundance increased as the number of arthropods increased, and the estimated range of bird abundance obtained from the model varied from 0.51 (0.28 – 0.93 [95%CI]) to 3.70 (1.68 – 5.20 [95%CI]) within sites. LAI was positively correlated to prey abundance (P = 0.01), and explained part of the variation in wood‐wren abundance. In forests with high LAI, arthropods have more aerial leaf litter as potential habitat so more potential prey are available for wood‐wrens. Forests with a greater abundance of aerial leaf litter arthropods were more likely to sustain higher densities of wood‐wrens in a fragmented tropical landscape.     

Large-scale spatial variation in palm fruit abundance across a tropical moist forest estimated from high-resolution aerial photographs

Fruit abundance is a critical factor in ecological studies of tropical forest animals and plants, but difficult to measure at large spatial scales. We tried to estimate spatial variation in fruit abundance on a relatively large spatial scale using low altitude, high‐resolution aerial photography. We measured fruit production for all 555 individuals of the arborescent palm Astrocaryum standleyanum across 25 ha of mapped tropical moist forest on Barro Colorado Island, Panama, by visually counting fruits from the ground. Simultaneously, we used high‐resolution aerial photographs to map sun‐exposed crowns of the palm across the same area, which were then linked to ground‐mapped stems. First, we verified that the fruit crop size of individual trees was positively associated with both crown presence on aerial photos and crown area visible on aerial photos. Then, we determined how well spatial variation in Astrocaryum fruit density across the study area was predicted by spatial densities of photo‐detected crowns and crown area compared to spatial densities of ground‐mapped stems and stem diameters. We found a positive association of fruit crop size with crown visibility on aerial photographs. Although representing just one third of all individuals in the study area, photo‐detected crowns represented 57% of all fruits produced. The spatial pattern of photo‐detected crowns was strongly correlated with the spatial pattern of fruit abundance based on direct fruit counts, and correctly showed the areas with the highest and lowest fruit abundances. The spatial density of photo‐detected crowns predicted spatial variation in fruit abundance equally well as did the spatial density of ground‐mapped stems. Photo‐detected crown area did not yield a better prediction. Our study indicates that remote sensing of crowns can be a reliable and cost‐effective method for estimating spatial variation in fruit abundance across large areas for highly distinctive canopy species. Our study is also among the few to provide empirical evidence for a positive relationship between crown exposure of forest trees and fruit production.     

PURIFICATION AND PROPERTIES OF CHOLINE ACETYLTRANSFERASE FROM THE NERVOUS SYSTEM OF DIFFERENT INVERTEBRATES

—Choline acetyltransferase has been purified from three invertebrate species, namely snail (Helix aspersa), cockroach (Periplaneta americana) and horse shoe crab (Limulus polyphemus.) All three enzymes followed a Theorell-Chance enzyme mechanism with a sequential addition of the substrates. All three enzymes were activated by sodium and potassium chloride and inhibited by high concentrations of magnesium or calcium chloride. The apparent K_m for choline and acetyl-CoA was for snail: K_mch= 370 μm ,K_mAcetyl-CoA= 51μm ; cockroach:K_mCh= 550 μm , K_mAcely-CoA= 16 μm horse shoe crab:K_mCn= 2700 μm K_mAcctyl-coA= 68 μm CoA inhibited the enzymes competitively with respect to acetyl-CoA and non-competitively with respect to choline. Acetylcholine inhibited the enzymes competitively with respect to choline and non-competitively with respect to acetyl-CoA. All the enzymes were inhibited strongly by 5,5′-dithiobis (2-nitrobenzoate), iodoacetate, acryloylcholine, chloracetylcholine and 3-bromacetonyltrimethyl-ammonium. The enzymes were only weakly inhibited by the styrylpyridine derivatives. The isoelectric points were 5.3 and 5.0 for the horse shoe crab and cockroach enzymes respectively. All three enzymes showed low affinity for a cation-exchanger (CM-Sephadex).     

SPRING HAUL-OUT BEHAVIOR OF RINGED SEALS (PUSA HISPIDA) IN KONGSFJORDEN, SVALBARD

Haul‐out behavior of ringed seals (Pusa hispida) was investigated during the spring molting period of 2003 (May–July) in Kongsfjorden, Svalbard, Norway. Hourly counts were conducted on the land‐fast ice in six spatially defined sectors in the inner fjord, from an elevated land‐based vantage point from early May through until the ice began to break up in June, from 0600 to 2200 daily (total counts n= 478). Concomitantly, measurements were made of a variety of weather parameters. Multiple regression analyses revealed that time of day (P < 0.001) and date (P < 0.001) significantly affected the number of ringed seals hauled out on the ice surface. Other factors influencing the number of seals counted on the ice were air temperature (P= 0.011) and wind speed (P < 0.001). Daily peaks occurred in the early afternoon between 1300 and 1400 and the seasonal high (n= 385) was registered during the first week in June, after which the number of seals on the ice in the fjord declined. In addition to the visual counts, 24 ringed seals were equipped with VHF transmitters, and the haul‐out behavior of individuals was monitored from May through July via an automatic recording station. The VHF‐tagged seals exhibited the same diurnal pattern seen in the total counts, with haul‐out most frequent from 1300 to 1400. Pups exhibited short and frequent haul‐outs, whereas longer haul‐out periods were seen in the older age classes; adult females had the greatest number of haul‐out periods that exceeded 24 h. The seasonal peak of haul‐out for the tagged seals preceded the peak seasonal counts by approximately 3 wk. This may reflect significant out‐ and influx of seals from and to the area, a phenomenon warranting further attention because of its implications for assessment studies.