Showing papers in "Marine Mammal Science in 1988"
TL;DR: No development of PB (phenobarbital)-type enzymes, and a lower activity of MC (3-methylcholanthrene)- type enzymes were suggested in small cetaceans, which implies long-term accumulation and possible reproductive toxicity of persistent organochlorines in these animals.
Abstract: Based on a comparative approach using PCB isomer and congener compositions in higher animals and their food organisms, the capacity and mode of PCB metabolism in small cetaceans were studied and the following conclusions were drawn: (1) Small cetaceans can metabolize some of the lower chlorinated biphenyls and this capacity seems to be the same in all species of these animals. (2) The values of MI, an index to evaluate the capacity of PCB metabolism, showed that the metabolic capacity of small cetaceans was extremely low as compared to those of birds and terrestrial mammals. (3) The structural requirements for PCB metabolism were different in animal species, in that small cetaceans have no capacity to metabolize a group of PCBs with adjacent non-chlorinated meta and para carbons in biphenyl rings. (4) No development of PB (phenobarbital)-type enzymes, and a lower activity of MC (3-methylcholanthrene)-type enzymes were suggested in small cetaceans, which implies long-term accumulation and possible reproductive toxicity of persistent organochlorines in these animals. The present approach should provide an important insight into the physiological responses of small cetaceans to persistent toxic chemicals.
330 citations
TL;DR: Although both species of dolphins were sighted more frequently in areas of high sea floor relief, white-sided dolphins occurred in areas where sea surface temperatures and salinities are low while common dolphins were Sighted in warmer, more saline waters.
Abstract: Sightings of white-sided (Lagenorhynchus acutus) and common dolphins (Delphinus delphis) from survey vessels operating on the continental shelf of the northeastern United States were recorded during spring and fall of six years. Distributions of these sightings were compared with sea surface temperature and salinity, and bottom topography. The apparent geographic distributions of the two species are complementary, although there is a broad overlap. White-sided dolphins occurred primarily within the Gulf of Maine, but also on Georges Bank and in the mid-Atlantic region. Common dolphins were abundant within a broad band paralleling the continental slope (100–200 m depth contour) from latitude 35°N to the northeast peak of Georges Bank. Sightings of this species were distributed primarily along the edge of the continental shelf south of 40°N in spring and north of this latitude in fall. Few sightings of common dolphins occurred in the Gulf of Maine.
Although both species of dolphins were sighted more frequently in areas of high sea floor relief, white-sided dolphins occurred in areas where sea surface temperatures and salinities are low while common dolphins were sighted in warmer, more saline waters. However, these environmental conditions may be only secondarily influencing dolphin distribution. Seasonal variation in sea surface temperature and salinity, and local nutrient upwelling in areas of high sea floor relief may affect preferred prey abundances, which in turn may affect dolphin distribution.
166 citations
TL;DR: A strong positive correlation of copper and selenium between mothers and pups indicated transfer of these elements from mother to pup in direct proportion to their concentrations in maternal liver and kidney.
Abstract: Milk samples from the stomachs of harp seal pups were analysed for Cu, Zn, Se, Cd and Hg, as were liver, kidney, and muscle from mother-pup pairs. Tissues were also analysed for MeHg. Milk contained, in addition to essential trace metals, Cd and Hg (57 ng/g and 6.5 ng/g respectively).
Pups had mercury in all three tissues. The percent methyl mercury in liver of pups was higher than in liver of mothers. Mercury in muscle was mostly methyl mercury in both mothers and pups. Total mercury in liver of mothers but not pups was correlated positively with selenium. Estimates of ingested mercury by pups indicated they had acquired most of their mercury during gestation.
Although mothers had cadmium in liver and kidney, it was not detected in tissues of pups. Cadmium did not transfer across the placenta, while mercury did. Tissue concentrations of Cu and Zn were higher in pups than mothers. The presence of metallothionein in pup tissues was postulated.
A strong positive correlation of copper and selenium between mothers and pups indicated transfer of these elements from mother to pup in direct proportion to their concentrations in maternal liver and kidney.
118 citations
TL;DR: In this article, the authors reviewed the information needed for a critical assessment of such interactions and proposed a method to estimate the quantity and size classes of each fish or invertebrate species consumed by seals and to compare this with the commercial catch.
Abstract: Most of the exploited fish stocks in the North Sea are also used as a food supply by a number of seal species; the same is true for some fish and invertebrate stocks in the Antarctic—although the fisheries there are, at present, much smaller than those in the North Sea. The information needed for a critical assessment of such interactions is reviewed. Using existing techniques it is possible to estimate the quantity and size-classes of each fish or invertebrate species consumed by seals and to compare this with the commercial catch. If fishing mortality is known, these estimates can be used to calculate the level of mortality imposed by the seals. However, a realistic evaluation requires information on the distribution and movements of the fish, the seals' feeding effort, and the fisheries effort in time and space. At present it is difficult or impossible to obtain this information, but recent technological developments in telemetry equipment will soon make it feasible. To assess the economic effects of changes in seal numbers on the fishery, or the ecological effects of changes in fisheries effort on seal populations, requires additional information on the responses of the fishery and the seals to changes in fish abundance, and of the commercial market to changes in the supply of fish.
113 citations
TL;DR: It is suggested that female attendance patterns are shaped by the increasing nutritional demands of growing pups and their increasing efficiency at suckling and that heavier pups consumed more milk than lighter ones.
Abstract: The onshore and at-sea cycles of females, suckling behavior of pups and their milk intake were studied in Steller sea lions (Eumetopias jubatus) during 1983 at Ano Nuevo Island, California. Females averaged approximately 21 h ashore and 36 h at sea. The trips to sea lengthened as pups aged, resulting in an overall decline in female time ashore to 30% by the sixth week following parturition. Activity budgets of pups showed no significant differences among suckling time, age and sex. Milk intake, estimated using labeled water studies, revealed that heavier pups consumed more milk than lighter ones (milk ingestion in ml/d = 4.26 + 0.0687 x {Pup Mass in kg]). Mean milk intake was 1.78 i 0.33 liters/d. Mean pup growth rate was 0.38 f 0.1 kg/d. The results suggest that female attendance patterns are shaped by the increasing nutritional demands of growing pups and their increasing efficiency at suckling.
111 citations
TL;DR: To gain behavioral evidence, a dolphin was trained to perform an echolocation task while wearing suction cups over its eyes and either of two neoprene robber hoods over its lower jaw.
Abstract: On the basis of disputed physiological evidence the fat-filled lower jaw of odontocete cetaceans has previously been hypothesized as the primary pathway to the inner ear for acoustic signals. To gain behavioral evidence, a dolphin was trained to perform an echolocation task while wearing suction cups over its eyes and either of two neoprene robber hoods over its lower jaw. One hood allowed returning acoustic signals to pass. The other substantially attenuated such signals. The dolphin's performance was significantly hindered while wearing the attenuating hood (P <. 001, ψ2) as would be expected if the lower jaw was critically important in the reception of high frequency signals.
81 citations
TL;DR: The present rate of population growth is used for modelling the influence of fertility and age-specific mortality and it is found that the observed high rate of increase is only realistic if female fertility rate is very high, the range of juvenile mortality rate is 0.33–0.52 and adult mortality is less than 0.15.
Abstract: The harbor seal (Phoca vitulina) population in the Kattegat-Skagerrak area has been dwindling for several centuries due to excessive hunting pressure. Corrected hunting statistics during 1890–1976 are used to estimate changes in population size over the past century. After protection was introduced in the 1960s and 1970s the harbor seal population in the area increased at an exponential rate of 0.12 and exceeded 5,000 animals in 1986. The present rate of population growth is used for modelling the influence of fertility and age-specific mortality. It is found that the observed high rate of increase is only realistic if female fertility rate is very high, the range of juvenile mortality rate is 0.33–0.52 and adult mortality is less than 0.15. Commonly cited higher mortality rates are not realistic in the Kattegat-Skagerrak area.
73 citations
53 citations
TL;DR: Because survival in the first year of captivity may be lower than subsequent years, estimates of the expected lifespan, based on data from the first few years of captivity, may be biased.
Abstract: Survival rates for three species of captive cetaceans are reported, based on records of dates of capture, birth, and death of individual animals. The annual survival rate was 0.93 for bottlenose dolphins and killer whales and 0.94 for white whales. Confidence limits of these estimates are discussed. Differences in survival rates between institutions were significant for bottlenose dolphins only. Calf survival for bottlenose dolphins was lower than non-calf survival. Survivorship of male killer whales was significantly less than survivorship of female killer whales; sex-specific survival rates were similar for the other two species. Estimates of average or maximum longevity alone were not useful in comparing rates of survival. Because survival in the first year of captivity may be lower than subsequent years, estimates of the expected lifespan, based on data from the first few years of captivity, may be biased.
46 citations
TL;DR: Mammalian remains recovered from three archaeological sites on the Oregon, U.S. coast provide strong evidence that 18th and 19th century commercial exploitation of marine mammals had major effects on the zoogeography and demography of those taxa.
Abstract: Mammalian faunal remains recovered from three archaeological sites on the Oregon, U.S.A. coast provide strong evidence that 18th and 19th century commercial exploitation of marine mammals had major effects on the zoogeography and demography of those taxa. Zalophus californianus and Callorhinus ursinus bred and pupped along the Oregon coast between 3,000 and 100 yr ago. About 100 yr ago Eumetopias jubatus abandoned a major rookery that had been utilized since at least 400 yr ago. Phoca vitulina does not appear to have suffered major modifications to coastal use or demographic patterns in Oregon during the last 3,000 yr, although a minor incident of intensified utilization of one location about 1,000 yr ago is suggested. All age-sex classes of Enhydra lutris lived on the Oregon coast until about A.D. 1900. Oregon's prehistoric remains of E. lutris display some dental characters similar to modern Alaskan specimens, and other dental characters similar to modern Californian specimens, conforming to a latitudinal dine reflected by historic specimens. Additional evidence for many of these observations is found in faunal remains recovered from archaeological sites on the coast of Vancouver Island, the Washington coast, and the northern California coast.
45 citations
TL;DR: The objective of this study was to develop a reliable method for collecting viable tissue samples for establishing continuous cell cultures from skin biopsies of free-ranging whales, and a method to collect and process these samples is presented.
Abstract: For researchers studying mysticere whales few methods for determining gender or for collecting biochemical and genetic information from unrestrained animals are available. The objective of this study was to develop a reliable method for collecting viable tissue samples for establishing continuous cell cultures from skin biopsies of free-ranging whales. A method to collect and process these samples is presented. Six of seven skin biopsies from gray whales were established in cell culture. Our results suggest that the viability of the samples is improved by (1) sterile processing in the field, (2) minimizing the time between collection and delivery to the cell culture facility, (3) reducing the concentration of antifungal agent, and (4) placing tissue explants under a coverslip. While the results reported in this paper are based on a small sample size, we believe that if the procedures are followed, they will increase the probability of successfully culturing cetacean tissue. Established cell lines can supply replenishable material from identified whales still living in the wild. These cultures can then be used for determination of sex from karyotypes, and for assessing genetic relationships of cetaceans from inherited protein, chromosomal and DNA polymorphisms. These much needed analytical tools can be used to determine familial and populational relationships, leading to a better understanding of mating systems, stock identification and effective population sizes of wild cetaceans.
TL;DR: To answer the question whether pollutants affect marine mammals, the occurrence of contaminants and the response of the animals to those chemicals have to be assessed and the retrospective study of pollution effects on marine mammals might be turned into a predictive approach.
Abstract: In integrating ecotoxicology and marine mammalogy two principal themes are conceivable: (1) the impact of contaminants on marine mammals and (2) the feasibility of monitoring marine pollution with marine mammals. Monitoring should be an alert procedure, carried out with a sensitive sensor. Uncertainties in interpreting analyses and the low susceptibility of marine mammals to short-term changes in pollution, make them inappropriate for pollution monitoring at present.
To answer the question whether pollutants affect marine mammals, the occurrence of contaminants and the response of the animals to those chemicals have to be assessed. In studying the occurrence of contaminants it is essential that atmospheric and riverine input, geochemical processes, and processes involved with the occurrence of natural compounds are considered. To investigate the mechanisms by which pollutants affect physiological processes the kinetics of contaminants in the animals and their clinical toxicity effects have to be studied. Comparative reference data on physical and chemical blood parameters facilitates checking for hematological disorders, electrolyte imbalance, serum biochemistry and hormonal changes. Following such a concept the retrospective study of pollution effects on marine mammals might be turned into a predictive approach.
TL;DR: In this paper, four aerial survey projects were conducted between 1977 and 1986 to determine the abundance, density and distribution of West Indian manatees (Trichechus manatus), in the northern Banana River, Kennedy Space Center, Florida.
Abstract: Four aerial survey projects were conducted between 1977 and 1986 to determine the abundance, density and distribution of West Indian manatees (Trichechus manatus), in the northern Banana River, Kennedy Space Center, Florida. Manatee density and distribution within selected portions of the 78.5 sq km study area were determined. Peak numbers of manatees occurred in spring of each year. The maximum counts increased from 56 in 1978 to 297 in 1986. Manatee abundance was lowest in the winter of each year. Mean density per flight increased from 0.52 manatees/sq km in 1977-78 to 2.73/sq km in 1984-86. This increase may reflect increases in the east coast population or shifts in the population distribution. Distributional changes were observed in the study area through time, with a lower percentage of manatees occurring in industrial areas and a correspondingly higher percentage of manatees in nonindustrial areas by 1985.
TL;DR: Findings indicate that beached dolphins and dolphins in captivity with a chronic history of illness should be examined for the presence of rays, and caution should be used in maintaining mixed exhibits of dolphins with stingray species.
Abstract: Ray spines were found associated with various tissues on necropsy of seven Atlantic bottlenose dolphins (Tursiops truncatus). In at least six cases they were considered a major factor in the death of the animal. Three mature Tursiops had ray spines located in the lung parenchyma. In two other dolphins the ray spine punctured the lateral chest wall without entering the lung tissue. A sixth Tursiops contained a ray spine located in the liver tissue, while a seventh animal had a ray spine lodged in the pancreas. Five of the dolphins were wild individuals and two had been in captivity for more than one year. These findings indicate that beached dolphins and dolphins in captivity with a chronic history of illness should be examined for the presence of ray spines. Caution should be used in maintaining mixed exhibits of dolphins with stingray species.
TL;DR: In conjunction with an Hawaiian monk seal, Monarhus schauinslandi, breeding enhancement program, fecal samples were examined for the presence of helminth parasite products (eggs, larvae, and proglottids) in the northwestern Hawaiian Islands.
Abstract: In conjunction with an Hawaiian monk seal, Monarhus schauinslandi, breeding enhancement program, fecal samples were examined for the presence of helminth parasite products (eggs, larvae, and proglottids). Eighty-rwo samples were examined from four island groups in the northwestern Hawaiian Islands: 38 from Kure Atoll, 32 from French Frigate Shoals, 11 from Laysan Island, and one from Lisianski Island. Idenrified helminth products include those of Diphyllobothrium sp.? D. canieroni, Contracaecum turgidurn, Anisahis sp., CMynosoma rauschi, and Trematoda. In addition, eggs from Hafararhne laysanae (Acari) were found in 3 samples. Eggs of C. turgiduni were present in the highest percentage (>6497zi) of samples from all locations. Eggs of Anisakis sp. and Trematoda are reported from this host for the first time.
TL;DR: The pygmy sperm whale and the bottlenose dolphin are equipped with a tapetum fibrosum and are the only carnivores known to possess this typically ungulate tapetal type, and the very large number of reflecting layers characterizing these tapeta may provide for increased spectral purity and efficiency.
Abstract: Abtract
The pygmy sperm whale (Kogia breviceps) and the bottlenose dolphin (Tursiops truncatus) are equipped with a tapetum fibrosum and, with other Cetacea, are the only carnivores known to possess this typically ungulate tapetal type. Tapeta from two regions of a retina, each with a different spectral reflectance (blue and green), were found to have significantly different fibrillar diameters and inter-fibrillar spacing. When the measured values are applied to a dielectric reflector model, the predicted wavelengths agree with the observed reflectance of the flat-mounted tapeta. The spatial properties of the fibrils change progressively from the tapetal origin in the fibroblast layer to the pigment epithelium, suggesting that different wavelengths may be reflected systematically with tapetal depth. The very large number of reflecting layers characterizing these tapeta, relative to those of other carnivores, may provide for increased spectral purity and efficiency.
TL;DR: In this article, a qualitative assessment of whether a population is above or below its MNPL can be carried out under circumstances where the value of the MNPL itself, and other details of the production curve, cannot be estimated.
Abstract: A qualitative determination of whether a population is above or below its MNPL can be carried out under circumstances where the value of the MNPL itself, and other details of the production curve, cannot be estimated. This qualitative assessment may often be sufficient for management decisions. The method proceeds by locally approximating the production curve, in the neighborhood of the present population density, from data on population sizes and harvests, and then determining whether this represents the ascending or descending arm of the curve. When the harvests are small, or when the harvests are a constant fraction of the production, the population-size data need only be relative. With adequate quantities of data, this assessment method can accommodate random measurement error and random perturbations in the dynamics of the population system.
TL;DR: In this paper, the authors applied dynamic response analysis to estimate the stock size relative to the maximum net productivity level (MNPL) for elephant seal populations from the South Farallon Islands, Aiio Nuevo Island, San Nicolas Island and San Miguel Island.
Abstract: Dynamic response analysis, a technique for determining stock size relative to the maximum net productivity level (MNPL), was applied to northern elephant seal populations from the South Farallon Islands, Aiio Nuevo Island, San Nicolas Island and San Miguel Island. Pup counts were used as indices of population size. The application of dynamic response analysis presented here involved some methodological innovations. We present a moving interval method which involves calculating separate dynamic response analyses for intervals of various lengths ranging from four counts to the total number available for the colony. The sign of the second order polynomial regression coefficient computed from a particular interval was used to indicate the colony's apparent status (relative to its MNPL; + = above MNPL, - = below MNPL) on that interval. Consistency in the sign of the second order coefficient, as the interval was moved along the trajectory, was used to determine the minimum reliable interval size. Each colony exhibited growth similar to that of a population below its MNPL. These results are consistent with recent natural history observations at San Nicolas, San Miguel and the Souch Farallon islands. Natural history observations at Aiio Nuevo Island suggest that the colony there is now at equilibrium. Thus, if our results from dynamic response analysis of the Ai10 Nuevo colony are correct, it appears that the MNPL may be close to the carrying capacity for these animals.
TL;DR: Sixteen tooth characters were analyzed in 277 specimens of spinner dolphins from the eastern tropical Pacific to determine whether the characters were associated with size of the animal, species-stock membership or geographic location and showed that tooth differences were notassociated with size but significant differences were found in some tooth variables with stock membership, incremental changes in latitude and whether the animal was collected north or south of the equator.
Abstract: Sixteen tooth characters were analyzed in 277 specimens of spinner dolphins (Stenella longirostriJ) from the eastern tropical Pacific to determine whether the characters were associated with size of the animal, species-stock membership or geographic location. The tooth characters included 5 continuous measurements and 11 qualitative variables. Statistical analyses of the characters included twoway ANOVA tests which assessed continuous measurement variables for differences based on stock membership, latitude and longitude of collection or whether the animal was collected north or south of the equator. Principal component analyses combined factors of continuous variables with those of qualitative variables into components which were used as variables in further analyses. Discriminant analyses were performed using continuous variables alone and using principal components as potentially discriminating variables. Results showed that tooth differences were not associated with size but significant differences were found in some tooth variables with stock membership, incremental changes in latitude and whether the animal was collected north or south of the equator. A discriminant function, containing only tooth length, correctly classified 67% of northern and 78% of southern animals according to location of collection north or south of the equator. A number of dolphin populations in the eastern tropical Pacific are caught incidentally by tuna seiners during fishing operations. One such species, the spinner dolphin, Stenella longivostris, includes a number of population stocks: the eastern spinner dolphin, northern and southern whitebelly spinner dolphin, Costa Rican spinner dolphin and Hawaiian spinner dolphin (Perrin et a/. 1979, 1985). Stock membership is determined at sea by government observers using distinguishing criteria of snout and dorsal fin shape and overall body form. Another recognized category, ‘unidentified,’ are animals with an intergrade color
TL;DR: The bony falx and bony tentorium of spotted dolphins at different growth stages were observed and formed possibly by continual dietary intake of large amounts of calcium, phosphorus and vitamin D.
Abstract: The bony falx (BF) and bony tentorium (BT) of spotted dolphins (Stenella attenuata) at different growth stages were observed. The BF and BT were observed to have the shape of the entire falx cerebri (FC) and tentorium cerebelli (TC), respectively, in adults, but were not seen in fetuses at all. Partially formed BF and BT were observed in the young. The BF and BT of spotted dolphins are formed by ossification in the FC and TC in the course of aging. Based on age determination by means of dentinal growth layers of the maxillary teeth, the ossification in the FC and TC of spotted dolphins begins by about 1 yr of age, and is completed, except for the passage of nerves and blood vessels, by about 9 yr of age. The BF and BT of spotted dolphins are formed possibly by continual dietary intake of large amounts of calcium, phosphorus and vitamin D.
TL;DR: In this article, the authors evaluate the performance of dynamic response analysis on a simulated population under variable conditions with uncertain data and show that it is most sensitive to the number and precision of the population estimates and least sensitive to environmental variability and the intrinsic population growth rate.
Abstract: A new method of stock assessment, dynamic response analysis, allows a qualitative assessment of stock status relative to its level of maximum net productivity to be carried out with minimal data. This paper evaluates the performance of dynamic response analysis on a simulated population under variable conditions with uncertain data. In the no-harvest case the data consist simply of a temporal sequence of relative population sizes. Dynamic response analysis is most sensitive to the number and precision of the population estimates and least sensitive to environmental variability and the intrinsic population growth rate. Significance levels must be chosen carefully, since some combinations of parameters and error levels result in an unacceptably low proportion of correct assessments. Dynamic response analysis can be a useful stock assessment technique for the management of marine mammals, but attention must be paid to the quantity and quality of the data.