Deep Sea Research (1953)最新文献

Sound from small explosions has been used to study the frequency-dependent characteristics of deep scattering layers in three areas of the western North Atlantic Ocean. Layers show resonant properties, the scattered sound being most intense in a narrow frequency band. The scatterers are presumed to be mainly the swimbladders of bathypelagic fishes. In layers peaking at frequencies above 5 kcps there is a systematic shift of peak frequency as layer depth changes during vertical migration. In two cases studied frequency changes as the $\text{5}\text{6}\text{th}$ power of the hydrostatic pressure. This suggests that in these cases the swimbladder simply expanded and contracted with changing pressure. In a third case frequency changes as the $\text{1}\text{2}\text{power}$ of the pressure. This suggests that the fish maintained neutral buoyancy throughout the depth migration by absorbing gas from the swimbladder as necessary. Layers peaking near or below 5 kcps are poorly resolved in depth. In one instance a direct relationship between frequency and depth has been established, but not well enough to define the relationship quantitatively. Pronounced depth and frequency migration is found in layers south of New England and south of Nova Scotia. Back-scattering coefficients were found to lie between − 64 and − 81 db re M⁻¹ in a small number of computations.

Collections of juvenile tunas during the period 1951–1960 from the central Pacific are recorded. Juveniles of Neothunnus macropterus (Temminck and Schlegel), Katsuwonus pelamis (Linnaeus), and Auxis sp. are described and figured. Initial results with the British Columbia midwater trawl, as modified for collecting tuna forage organisms and juvenile tunas, suggest that this trawl has considerable promise as a collecting device. Its ability to catch juvenile tuna appears much greater than that of the 10 ft Isaacs-Kidd midwater trawl. Although much has been learned in recent years abouth the biology of adult tunas, we still have very little information concerning the occurrence, distribution, and habits of their postlarval and juvenile stages. This lack is due mainly to poor success in collecting the young with the methods hitherto used, i.e., dipnetting at night-light stations, midwater trawling with small and medium-sized nets, seining with tuna bait nets, and searching the stomach contents of adult tunas and other pelagic fishes. Most of the juveniles recorded in the literature have been reported from scattered localities and have come either from the stomachs of pelagic fishes (Kishinouye, 1919, 1923, 1924, 1926; Inanami, 1942; Marr, 1948; Eckles, 1949; Shimada, 1951a; Yabe, Anraku and Mori, 1953; Yabeet al., 1958) or from dipnetting at nightlight stations (Schaefer and Marr, 1948a, 1948b; Wade, 1949, 1950; Shimada, 1951b; Klawe and Shimada, 1959). Since tuna juveniles are taken sporadically, generally in small numbers, it is important that all known captures be recorded so that the information will be available to investigators.

The pattern of the steady state, transverse current component in the surface layer of the Florida Current off Miami is described on the basis of two independent sets of data. The first consists of over 500 GEK observations obtained over an 8 year period and the second of over 1100 observations selected from Pillsbury's measurements. There is a westward component along the western edge of the Current and an eastward one across the remainder. The maximum magnitude is about 10 cm/s. Discussions of the methods of data selection, reduction, and errors are included.

Recent studies of the benthic faunas of the continental slope of western North America, highlighted by the collection of additional specimens of Neopilina galatheae Lemche, 1957, off Baja California have led to speculations regarding the origin of invertebrate faunas on the continental slope of the Eastern Pacific. It is suggested that many of the shelf and epicontinental bottom faunas migrated down the slope during the Paleozoic and early Mesozoic times in response to competition and population pressure from the newly evolved forms. In areas of relatively old, stable, deep-sea topography, some of these early forms still exist, with minor changes in external morphology. Since middle Cretaceous times, many new topographic features of the Eastern Pacific, particularly trenches, ridges, and borderlands, presumably have been formed along the continental margins. In as much as these features were formed after the Paleozoic and early Mesozoic invasion of invertebrates into the deep sea had occurred, a new migration of Tertiary and Holocene faunas may have taken place. Recent collections of benthic invertebrates in depths of 1000 to 4000 metres support this thesis, as ‘ancient’ or relict forms of invertebrates, exemplified by Neopilina, were found on outer slopes that descend directly to the sea floor, or on the undisturbed abyssal bottom. Modern, or more recently evolved faunas, which appear to have originated from fairly recent (Tertiary) shallow-water environments, as well as from older abyssal regions were found at equivalent depths in trenches and in borderland basins, inshore of the Paleozoic relicts. Animals from Arctic and Antarctic waters may have invaded abyssal and hadal depths during the cooling of the Pleistocene.

The distribution of temperature, salinity and density for the Red Sea and Gulf of Aden in June of 1958 suggests that evaporation exerts a greater influence on the circulation of the Red Sea than does the shifting wind pattern emphasized by Thompson (1939a, b,). This view is supported by evaporation rates for the Red Sea presented by J. Neumann (1952) and Privett (1959). A surface inflow from the Gulf of Aden was observed entering the Red Sea, i.e., from the direction opposite to the prevailing NNW winds of summer. A prominent outflow of warm, saline Red Sea water extends into the Gulf of Aden beneath this surface inflow. In June, the dense, isothermal, isohaline water that fills the Red Sea basin below sill depth appears to be entrapped there, exchange with the Gulf of Aden being restricted to shallower levels. Oxygen and phosphate distribution profiles support the thermo-haline circulation proposed. Red Sea water can be traced well into the Indian Ocean, as illustrated by a T-S diagram (Fig. 7).

In the Coral Sea, the correlations between the apparent oxygen utilization and the inorganic phosphate concentration on one side, the total carbon dioxide concentration on the other side, are significant. The regression curve of total carbon dioxide on apparent oxygen utilization is a straight line; the ratio atom by atom A.O.U./C. is close to $\text{1}\text{1}$ which is half of the theoretical value. The regression of inorganic phosphate on A.O.U. does not seem to be best represented by a straight line and the ratio A.O.U./P. which is smaller than $\text{180}\text{1}$ varies with depth. A possible explanation of this anomaly is found in a slight difference between the composition of the oxidizable organic matter and that of the basic molecule of carbohydrate which is considered to be the first step in the photosynthetic process; for instance the percentage of hydrogen could be smaller and the phosphorus concentration at 1000 m triple of that near the surface. Further computations show that the equatorial waters of the Pacific do not contain any preformed phosphate and that the organic matter which is synthesized in the eastern Pacific must be rich in nitrogen.