Publications posted here are typically legacy print or electronic-only publications of value to the Scripps researchers, sometimes by non-Scripps authors. Publication here is intended to make these works of value more readily available in an open access environment. More recent individual works by Scripps' scientists are sometimes published elsewhere on this Repository site.
External and internal characters, horizontal and vertical distributions, luminescence, and food of the dwarf pelagic shark, Euprotomicrus bispinatus
The object of this paper is to coordinate and expand knowledge of Euprotomicrus bispinatus (Quoy and Caimard, 1824), the pigmy shark : a most remarkable creature, which until recent years had been known for a century and a quarter on the basis of very few, casual observations at sea and of 8 museum specimens. As a result of increasing emphasis on high-seas research we now have data on 37 specimens, and a much richer fund of information on the species.
The pigmy shark is a strange creature, defying most concepts of a shark. In the first place it is tiny: the largest known example spans only 265 mm (10 ½ in.) in total length and weighs less than 70 grams (about 234 ounces) ! Males mature at 170 mm, females at 233 mm or less. Its terete body and wee gill openings remind one of a lamprey. Its essentially diphycercal tail, with large, rounded dorsal and ventral caudal-fin lobes and horizontal termination of the spinal column, little resembles the long-drawn-out, upturned heterocercal tail that is ordinarily associated with a shark. In this, and in some other respects, the appearance of this shark is almost embryonic. Its skeleton is almost devoid of calcification (apparently an adaptation for neutral buoyancy). Its vertebrae are unexpectedly few for a shark, and in radiographs lookr strangely like those of a bony fish. The teeth are strikingly unlike in the two jaws.
This little shark has been taken only at the sea surface, almost exclusively in the vast, relatively sterile central water masses of the world ocean. Its thousands of tiny light organs can combine to produce a bright blue-green glow. We now learn that it undertakes vertical migrations to considerable depth, where it feeds on bathypelagic squids and fishes.
Systematics, distribution, and abundance of the epiplanktonic squid (Cephalopoda, Decapoda) larvae of the California Current, April, 1954- March, 1957
Our knowledge of the biology of oceanic cephalopods is extremely limited. The population sizes, distribution patterns, breeding seasons, life histories, and growth rates are virtually unknown. In view of the fact that these organisms are undoubtedly abundant and ecologically important, both as predators and prey, this state of ignorance is unfortunate. Part of the reason for this lack is attributable to the great difficulty of adequately sampling the adults. The larvae and some juveniles, however, can be caught, in the types of plankton nets and trawls generally in use. Therefore the possibility exists that the times and places of spawning, and the developmental history of many species, may be determined from zooplankton surveys. Using this approach presupposes that a sufficiently extensive area is surveyed and that the sampling is intensive in both space and time. It is also necessary that enough specimens of the adults and intermediate-sized ranges be available for accurate identification of the larvae. This is best done by tracing the morphological changes through progressively smaller individuals. The Marine Life Research Group at Scripps Institution of Oceanography (SIO) has available a very large collection of zooplankton samples taken by the California Cooperative Oceanic Fisheries Investigations (CalCOFI) in the California Current. This program has surveyed a large portion of this current system by monthly cruises for a period of ten years. It is from these samples that the data in this report are derived.
Season of attachment and rate of growth of sedentary marine organisms at the pier of the Scripps Institution of Oceanography, La Jolla, California
This paper reports the studies in progress during the past four and one-half years on the organisms, particularly invertebrates, which attached themselves to submerged blocks throughout the year.
Various investigators have described the California Current system,. Since then various small-scale studies have been made over the area, but the Point Arguello area had not received particular attention until work in January 1964. The Point Arguello area is an especially interesting part of the California Current because it is characterized by a remarkable and systematic seasonal reversal in flow.
This final report is the result of research during the five and one-half year period from September 1948 to March 1954. Throughout the investigation the apparent decline of sport fish was causing sport fishermen great concern. Among other factors, kelp harvesting was blamed for the poor catch of the sportsman. More than a year after the beginning of this investigation, the Kelco Company approached the Scripps Institution of Oceanography of the University of California, with the request that the problems of kelp cutting in relation to the fish supply be attacked by the University under a fellowship grant, by unprejudiced research. The Company wanted to determine whether the kelp operations were adversely affecting fishing, and if so, how harvesting methods might be altered to prevent this.
The first phase of the program was concerned with observation and identification. Thousands of hours were spent above and below the surface observing the organisms in their own environment. Extensive use was made of scuba diving equipment for observations, collection, and placing of equipment. Underwater photography was developed to a point where many observations could be recorded.
The second phase of the program was to appraise the effects of kelp harvesting on fish life. Because of the lack of pertinent published data on the ecology of the inshore waters, it was necessary to investigate not only the beds of the main commercial kelp (Macrocystis pyrifera), but also many other regions, in order to obtain comparative data. Such areas included bays, rocky areas below the levels where kelp grows, rocky areas with no kelp, the surf zones, sandy areas, and regions outside the West Coast range of Macrocystis. Kelp beds were studied as far north as Monterey and as far south as the San Benito Islands, Baja California. Diving observations in the kelp were made at Monterey, Morro Bay, Goleta, Santa Barbara, Point Dume, Palos Verdes, Newport, Laguna, Dana Point, San Clemente, Del Mar, Solana Beach, La Jolla, Point Loma, Ensenada, Punta San Carlos, Punta Blanca, Punta Santa Rosalia, and numerous other points along the mainland; also at San Miguel, Santa Rosa, Santa Cruz, Anacapa, Santa Catalina, Coronado, San Martin, and San Benito Islands. Intensive studies of the problem were carried out in Orange and San Diego Counties, with special concentration on the nearby La Jolla kelp beds.
One portion of the La Jolla kelp beds was left uncut as a control. Little difference has been noted in the fish life within the bed as contrasted with harvested beds. The kelp itself became more sparse, probably because of reduced light penetration through the heavy canopy that developed temporarily. In the 1952-53 winter season much of the kelp was destroyed by storms. These studies yielded a vast amount of information bearing not only on the kelp problem but also on the life ways of the fishes.
As a result of these long and thorough studies, it is concluded that kelp harvesting, as cutrrently practiced, has no seriously detrimental effects on fishing. The various claims as to the ways in which kelp harvesting was supposed to destroy fish life and to decrease the fish catch were completely investigated and found to be in error. Spawning and nursery grounds of fish are not being destroyed. Sufficient cover and food are always available during and after harvesting. The kelp beds are not destroyed by harvesting methods. Harvesters do not frighten sportfish from an area.
For several decades California has experienced a tremendous increase in population. Cities have grown where deserts and foothills were the homes of deer, rabbits, ground squirrels, ground owls, doves,and quail. In most places these animals have largely disappeared, and with them the intertidal mollusks — Pismo clams, butter clams, abalone, and many other species. The shore fishes such as corbina and spotfin croaker are less common in the individual fisherman's catch. Over kelp beds where a man might have fished alone a decade or two ago, we may see 50 sport boats with a total of 1000 anglers. Thus, even though the annual catch may be the same as or higher than 10 or 20 years ago, the catch per fisherman is much lower.
The kelp industries have arisen indirectly from our social-economic needs for new raw materials to fill new markets. They have become established in our economy and are essential for the production of certain new products. As is typical of modern, young industries, they have conducted research to determine the maximum sustained yield. The industry naturally has no desire to destroy kelp.
The sportfishing industry is large and provides recreation, necessary for our nation's health, to thousands of persons. With the addition of thousands of newcomers to sportfishing and the reduction of catch per unit of effort, it is not difficult to understand the fishermen's concern over factors supposedly destroying their sport. It is necessary, however, to determine the real reason for the apparent decline of fish before any constructive action can be taken. It may be a problem of overfishing or of natural population fluctuations, but the blame cannot be laid to the kelp harvesting.
Southern/Northern California Coastal Processes Annotated Bibliography: Coast of California Storm and Tidal Waves Study
The California Coastal Processes Bibliography comprises 2,355 references to scientific literature & technical reports on the California coast: coastal processes, geology and geomorphology, hydrology and hydraulics, and meteorology. Compiled by the Los Angeles & San Francisco Districts of the Army Corps of Engineers, this Bibliography was published as part of the landmark Coast of California Storm and Tidal Waves Study (CCSTWS) and corresponds to the following publications:
Southern California coastal processes : annotated bibliography : the coast of California storm and tidal waves study. Los Angeles. : US Army Corps of Engineers, Los Angeles District, Planning Division, Coastal Resources Branch, 1985. CCSTWS ; 85-4. Coast of California storm and tidal waves study 85-4.
Northern California coastal processes annotated bibliography : Coast of California storm and tidal waves study / prepared by U.S. Army Corps of Engineers, San Francisco District, Planning/Engineering Division, Water Resources Branch. Los Angeles : US Army Corps of Engineers, Los Angeles District, Planning Division, Coastal Resources Branch, 1987. CCSTWS 87-5. Coast of California storm and tidal waves study 87-5.
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This scientific bibliography on human-powered submarines aims to list references containing some level of technical information. The references are listed in reverse chronological order.
This annotated bibliography covers the published literature on the flora and vertebrate fauna of the islands surrounding the Baja California peninsula. While comprehensive, it cannot claim to be exhaustive; however, Biological Abstracts and Zoological Record were searched extensively, back to the beginning of those indexes. With few exceptions, the author has examined either the materials themselves or abstracts. The bibliography is annotated, not abstracted. The descriptor field lists the islands mentioned in the work, or the phrases "Gulf Islands" and "Pacific Islands". The bibliography does not include Guadalupe, Socorro, the Tres Marias or other outlying islands. It contains few references to pinniped populations, and none to fish, insects or invertebrates since it is limited to vertebrate species and the terrestrial habitat. It does not cover the Mexican or Latin American literature on the islands to any great degree. Last Updated: July, 1997
Report on the scientific results of the voyage of H.M.S. Challenger during the years 1873-76. Zoology - Vol. 4
Zoology Volume 4.
Part XI. Report on the Anatomy of the Petrels (Tubarines) ...
By W. A. Forbes
Part XII. Report on the Deep-Sea Medusae ...
By Ernst Haeckel
Part XIII. Report on the Holothurioidea ... Part I [Elasipoda].
By Hjalmar Theel
Report on the scientific results of the voyage of H.M.S. Challenger during the years 1873-76. Deep-sea deposits
Deep Sea Deposits
Report on the Deep-Sea Deposits Based on the Specimens Collected During the Voyage.
by John Murray and A. F. Renard
Appendix I. Explanation of Charts and Diagrams
Appendix II. Report on an Analytical Examination of Manganese Nodules, with Special Reference to the Presence or Absence of the Rarer Elements.
by John Gibson
Appendix III. Chemical Analyses
Report on the scientific results of the voyage of H.M.S. Challenger during the years 1873-76. Zoology - Vol. 5
Zoology Volume 5.
Part XIV. Report on the Ophiuroidea ...
By Theodore Lyman
Part XVI. Some Points in the Anatomy of the Thylacine (Thylacinus cynocephalus), Cuscus (Phalangsta maculata), and Phascogale (Phascogale calura) ... ; with an account of the Comparative Anatomy of the Intrinsic Muscles and Nerves of the Mammalian Pes.
By D. J. Cunningham
Fish Bulletin No. 8. Racial and seasonal variation in the Pacific herring, California sardine and California anchovy
This study of the variation in certain commercially important clupeoid fishes of western North America is one of a series by which it is designed to determine the relation which the varying characters of fishes bear toward the physical features of their environment. Although other characters and other environmental factors are receiving attention in these investigations, chief stress is now being laid on the correlation between the average number of vertebrae and the temperature of the water. The average surface temperature of the coast waters of San Francisco Bay (Golden Gate), Monterey Bay (Pacific Grove) and San Diego (off Coronado Beach) is indicated for the whole year by the three curves on Plate I. The marked difference in temperature between the ocean water of southern California and central California is illustrated by the curves for the San Diego region and for Monterey Bay, which is really a very open gulf. The usual maximum temperature for Monterey is lower than the ordinary minimum off San Diego. These is not an even gradation of temperature between these two localities, Point Conception marking the boundary between the cold waters of the central coast and the warmer waters of southern California. In each region, moreover, there is much local variation in temperature conditions, due not only to differences in protection and depth, but also, probably, to the differential upwelling of deep, cold water (McEwen, 1912, 1916). The curve for San Diego is taken from McEwen's 1916 paper; that for Monterey is smoothed from unpublished data supplied by Director Walter K. Fisher of the Hopkins Marine Station at Pacific Grove. The temperature curve at the entrance to San Francisco Bay, constructed by slightly smoothing Davidson's (1886) monthly averages, is intermediate between the San Diego and the Monterey Bay curves. The higher temperatures at San Francisco as compared with the Monterey records are due to the greater warming of the waters in the shallows of San Francisco harbor. As the fishes here treated are of great importance from the standpoint of the commercial fisheries, this paper is published in the present form largely as a contribution to the fishery-biology of these species. An attempt to determine definitely the racial status of the various populations of each form would, however, be beyond the scope of the present paper. Our data, however, are brought to bear on such problems. This is done to suggest conclusions, and to make our data available to the fishery investigators. We have applied to our data on the herring and the anchovy a method of analysis which we have found useful in studying the seasonal variation in the number of segments in freshwater fishes (Hubbs, 1922, 1924). By this method the correlation between individual variations and environmental factors is determined. Measure is obtained, also, of the degree to which the average number of segments fluctuates on a purely individual, as contrasted with a racial basis. The results so secured are of value in interpreting the significance of observed differences in the average number of segments for samples from different localities.
Fish Bulletin No. 65. Analysis of Populations of the Pacific Sardine on the Basis of Vertebral Counts
These vertebral counts indicate that sardines from British Columbia to Pt. San Eugenio in central Lower California comprise a mixture of populations, the young of which may have been reared on nursery grounds in any of these localities. For most seasons, presumably, the nursery grounds off California and northern Lower California make the greatest contributions to the population. Sardines living off southern Lower California and in the Gulf of California probably comprise a distinct group which does not mix with the northern fish; or if a mixture occurs, the proportion of southern fish to the total northern population is small. The interchange between nursery grounds begins early, perhaps before the sardines are a year old. The number of vertebrae varies between year-classes, and certain year-classes are characterized by high or low averages in all localities. The average number of vertebrae is approximately 51.7 for all sardines north of southern Lower California and about 51.2 for sardines from southern Lower California.
This bulletin is designed as a guide to those marine fishes of California which are likely to be caught by commercial and sport fishermen. While the species included represent only a fraction of the total recorded from the State, those remaining are mostly either deep-sea forms or small fishes of inshore waters which rarely, if ever, enter the fisherman's catch. The guiding precept of likelihood of capture by fishermen results in the inclusion of some species which are actually rather rare in California and the exclusion of some common varieties.
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A surface recovery technique was developed for the retrieval of a vertically oriented array which had been anchored at a depth of 4550 meters. The array was severed within 100 meters of the bottom in order to retrieve two faulty anchor releases as well as the scientific instrumentation.
Sixteen papers were presented during the symposium and asterisks denote the names of authors who have contributed to this volume. Leonard Compagno began with an overview of white shark biology and anatomy followed by Shelton Applegate and Luis Espinosa who presented two papers dealing with the fossil history of the white shark and implications concerning the habits and present status of the recent species. Peter Klimley* and Wes Pratt* and Jack Casey* presented papers on the distribution of white sharks along the California coast and in the western North Atlantic, respectively. Leighton Taylor* presented a paper on historical and contemporary records of white sharks in Hawaii. Three papers dealing with white shark physiology were presented by Frank Carey* (body temperature and capacity for activity), Scott Emery* (hematology, cardiac and gill morphology), and Joel Cohen* and Samuel Gruber* (visual system with emphasis on retinal structure)followed by Gregor Cailliet* who presented information on age and growth. Richard Huddleston presented a paper on stomach and spiral-valve contents of juvenile white sharks. The behavior of white sharks was detailed in four papers presented by John McCosker* (attack behavior and predator/prey strategies), Timothy Tricas* (feeding ethology), Donald Nelson (telemetry of white shark behavior), and David Ainley* (white shark/pinniped interactions at the Farallon Islands). Robert Lea* presented an update on shark attacks off California and Oregon. Bernard Zahuranec offered the concluding remarks. Eleven of the 16 contributed papers appear in this volume.
This book is the outcome of my analysis of all available knowledge of the Southeast Asian Waters. It is hoped that workers in the region, whether in oceanography or other branches of science may find it a source of information and a stimulus to undertake further research in these waters. Some chapters in this book are summaries and condensations of already known facts, but others offer new ideas and interpretations, particularly those chapters on monsoon circulations and their dynamics, on deep circulation and its relation to surface circulation, on the energy exchange between sea and atmosphere, and on the quantitative description of the exchange of water in the deep sea basins.
The physical oceanography of the Gulf of Thailand, Naga Expedition; Bathythermograph (BT) temperature observations in the Timor sea, Naga Expedition, Cruise S11
The Research Vessel Stranger of the Scripps Institution of Oceanography, University of California, San Diego, was engaged in the Naga Expedition in the Gulf of Thailand and the South China Sea during the period of October, 1959, to December, 1960. The expedition was jointly sponsored by the Governments of South Viet Nam, Thailand and the United States of America. It had a two-fold purpose; to collect oceanographic, biological and fisheries data and material and to train scientists and technicians from Thailand and South Viet Nam in oceanography and marine biology. This report is a description of the oceanographic environment in the Gulf of Thailand derived from oceanographic and meteorological data collected for the most part on six cruises in the Gulf between October, 1959, and December, 1960. The cruise plans for the Gulf of Thailand were designed to investigate systematically the distribution and variability of the physical properties of the Gulf waters. The station plan consisted of stations located 30 to 40 miles apart on five parallel lines running perpendicular to the east and west coasts of the Gulf. The lines were 60 to 90 miles apart. Figure 1 is a composite plan for the five Gulf cruises which made complete hydrographic measurements. The stations were numbered chronologically on each cruise. Thus, stations at approximately the same location have different numbers on each of the cruises. Within the limits of navigation the primary stations on each line were at the same location on each cruise. The following physical oceanographic data were collected at each station; reversing thermometer temperatures, salinity and oxygen determinations at standard levels—0, 10, 20, 30 and 50 m—as depth allowed and bathythermograph (BT) temperature observations. The latter were also taken midway between regular stations and at intervals parallel to shore between station lines. Meteorological observations, including wind, air temperature and sea condition, were taken at the time of each BT. Station data and a description of the physical and chemical methods may be found in Faughn, NAGA report, volume 1. The R. V. Stranger of the Scripps Institution of Oceanography carried out an extensive geophysical survey of the Timor Sea between March 29 and April 24,1961, (van Andel and Veevers, 1967) following the completion of the major oceanographic observational programs in the Gulf of Thailand and the South China Sea. During the survey, closely spaced bathythermograph (BT) temperature and wind velocity observations were made. Observed wind velocities, vertical temperature sections along the cruise tracks and horizontal distributions of temperature at standard depth levels based on BT data are the subject of this report. These observations provide a detailed description of the temperature structure of the Timor Sea and complement the more general one given by Wytrki (1961).
SIO Reference 59-10. The main emphasis of this paper is on the development of a new set of concepts in radiative transfer theory which may eventually broaden its scope of applicability and draw it closer to the discipline of topological dynamics - the mathematics of future physics.
Historical Logbook Databases from California's Commercial Passenger Fishing Vessel (Partyboat) Fishery, 1936-1997
Commercial passenger fishing vessel (CPFV, or ‘partyboat’) logbook data have only been available to the public as two-page reports summarizing sport catch by port area for the calendar year. Electronic records of individual trip logs have been maintained by the Department since 1980, but trip-specific logbook records contain confidential information (vessel-specific) and are not available to the general public. From 1936 to 1978, however, the Department maintained an archive of reports (hard copy sheets) which summarize total monthly CPFV catch and effort for California Department of Fish and Game statistical areas (‘blocks’). These data are the subject of this report.
This report is on the topic of informatics and its relations to scientific research and data - rich, multi-faceted data that represent the earth and environmental systems. Data travel from field and laboratory into collections, repositories and archives. Just as data are a scientific resource, so too the work carried out with data and their organization is a resource for the environmental sciences.
Informatics is concerned with the stewardship of data, that is, with the tending of data and its flow, the design of information systems and their interfaces, and the growth of infrastructure given a distributed variety of data arenas. Enacted at the intersection of information science, environmental science and social science, informatics is evolving as we learn more about information environments and arrangements of human and technical systems. Five informatics ‘good practices’ are identified in this report:
Informatics Good Practices
1. Incorporate data problem formulation and data scoping early in the scientific planning process.
2. Recognize articulation, translation, negotiation and mediation as central to work with data.
3. Partner with appropriate information professionals for data work.
4. Create collaboration opportunities as well as coordination mechanisms for community work.
5. Recognize informatics as conducting research while carrying out information management.
The realm of informatics ranges across spatial, temporal, and organizational scales, weaving together diverse configurations, stretching over physical, digital and conceptual spaces. Many salient topics about data care remain to be discovered or investigated: data classification and provenance; data organization and modeling; data migration and data exchange; data assurance and quality control; data mediation and integration. Along with the development of roles for information professionals, we are learning about the dynamics of information environments, communities, and networks.
Informatics is happening. As we transition from use of ‘my data’ to ‘our data’, changes occur in data, collaborative, and scientific practices. Informatics provides new approaches and tools of interest to environmental scientists, information professionals, and social scientists alike.
I am an information manager privileged to work with several long-term, interdisciplinary projects within the Integrative Oceanography Division (IOD) at Scripps Institution of Oceanography and as an affiliate of the Science Studies Program at UCSD with its dynamic mix of communication, sociology, history and philosophy. Regarding my agenda with informatics, it is twofold: to be a responsible data steward and to partner with environmental science researchers by creating a contemporary information environment that supports concurrently the practice of information management and the inquiry of informatics research.
Seasonal airborne and ground-based observations of sand level changes were made along the coast of southern California from 2001 to 2008. Hourly, high alongshore spatial resolution wave estimates from a network of wave buoys and a spectral refraction wave model complement the sand level change data. Water returns from the ocean surface were removed from the airborne lidar elevation observations with a new method using tide and wave data, which was validated with concurrent in situ surveys. The resultant sand levels show high alongshore variability in seasonal shoreline position change along the 120-km survey region. Alongshore variability in wave energy, geologic factors, and sand grain size are hypothesized to control the alongshore variability of the seasonal shoreline change magnitude.
Monthly or more frequent ground-based surveys at four selected focus sites show seasonal shoreline and bathymetry change, with winter shoreline erosion and offshore bar development, and summer shoreline accretion and the loss of the offshore bar. Analysis of surveys completed after a small beach nourishment at Torrey Pines Beach showed the presence of the nourishment through more than one full seasonal cycle.
Observations from Torrey Pines Beach show the dependence of shoreline change on the initial shoreline position and the wave forcing. The observations motivated the development of an equilibrium shoreline change model, which accurately reproduces the observations with four free parameters. With at least two years of monthly surveys or multiple years of appropriately-timed biannual observations used to determine the free parameters, the model accurately predicts withheld observations and is applied at the additional survey sites. Ongoing work includes applying the model at additional locations and investigating the relationship between the tuned parameters and geologic factors.
Coastal modifications to control erosion, maintain navigation channels, and create harbors are often undertaken near surfing breaks. Surfing conditions can be improved by these activities, but they can also adversely affect existing surfing breaks. Jetties are coastal structures that on occasion improve surfing conditions. Even though there is an increasing volume of literature on the ways ordinary waves transform into surfing waves, the mechanics of surfing breaks around jetties has not been explored in detail. Four main types of surfing breaks that are created or enhanced by jetties have been identified. The types are dependent on the length of the jetty relative to surfzone width and the degree to which the ebb delta influences wave propagation. Case studies clearly show the behaviors of the different types of jetty breaks. Monochromatic wave refraction modeling of each site has identified the surfing break components that produce the surfing waves. Understanding the effects of a coastal structure on sediment transport, ecology, water quality, shoreline position, and recreation is important to minimize and mitigate any potential negative effects and to streamline coastal permitting. The effects on surfing conditions are being considered more often as the social and economic value of surfing to coastal communities is realized. This research helps to better predict the impact of jetty construction or alteration on surfing conditions.
Crangon (Alpheus) and Synalpheus are the two principal genera of noise-producing shrimp. These animals (not to be confused with commercial shrimp, which are noiseless) are about 3/4 inch to 1-1/2 inches long. They have one enlarged claw which produces a vigorous snap when closed. Over a large colony there is a continuous succession of snaps which causes an intense crackling noise resembling the burning of dry twigs. With increasing distance from the shrimp bed, the crackle merges into a sizzle or a hiss.
The directivity index which is currently used for characterizing the directional properties of transducers, refers primarily to their ability to radiate sound power. When transducers are used in echo ranging, the directivity index is, theoretically at least, of minor interest. Of greater interest is the ability of the transducer to discriminate between the echo from a target at which it is pointed, and the reverberation returned to it from this and other directions. This discrimination is measured by other quantities, called reverberation indices. One of these concerns volume, the other surface or bottom reverberation. The purpose of the present work was to study the relations between the three indices.
Conclusions drawn from a study of typical projector patterns are as follows:
1. The volume reverberation index and the surface reverberation index of a projector are linearly related to the directivity index, provided that the directivity pattern is reasonably similar to that of a circular piston in an infinite baffle. This condition is found in the echo-ranging projectors studied when they are operated at 24 kc without domes. However, the directivity index does not provide a reliable measure of the reverberation indices when the projector pattern has abnormally strong side lobes.
2. Neither projector housing studied has appreciable effect on reverberation indices.
3. The echo: reverberation ratio depends almost entirely on the shape of the main lobe of the composite directivity pattern between zero and -6 db. As a result, the reverberation indices of a transceiver can be determined by measuring the width of its directivity pattern at -6 db. Half of this angle will be termed the half-width of the pattern.
4. Since the reverberation indices can be so readily calculated from the half-width, it is recommended that this quantity be specified in describing a transducer. The directivity index usually, but not always, can be calculated from the half-width to within 3 db.
UCDWR No. U100. This investigation was undertaken to obtain information onthe northward extension of crackling underwater noises characteristicof the coastal waters of Southern California and for the purpose ofobserving if there were any seasonal changes in background noises inthe Puget Sound area which had been visited previously in November1942. The regions visited include Santa Barbar.a, San Luis Obispo,Monterey and Eureka to Crescent City in California, and AdmiraltyInlet and the San Juan Archipelago in Puget Sound.The characteristic crackling noises produced by snappingshrimps were found only at Santa Barbara, San Luis Obispo, andMonterey. In the northern California and Puget Sound areas wherethese animals have not been reported the waters were relatively freefrom biological noises, only very weak crackling and piping soundswere detected. There was no noticeable seasonal change .in noiseconditions in the Puget Sound area.