Deep Scattering Layer Migration and Composition: Observations from a Diving Saucer Eric G. Barham Science, New Series, Vol. 151, No. 3716 (Mar. 18, 1966), 1399-1403. Stable URL: http://links.jstor.org/sici?sici=0036-8075%2819660318%293%3A151%3A3716%3C1399%3ADSLMAC%3E2.0.CO%3B2-9 Science is currently published by American Association for the Advancement of Science. Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/about/terrns.html. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.j stor.org/joumals/aaas.html. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is an independent not-for-profit organization dedicated to creating and preserving a digital archive of scholarly journals. For more information regarding JSTOR, please contact [email protected]. http://www.jstor.org/ Tue Nov 23 04:04:412004 References and ~otes frequency bands. This strongly implies their daytime depths, and apparently 1. W. J. H. Nauta and P. A. Gygax, Stain resonant scattering from bubble-con- the French bathyscaphe dives have also Techuol. 29, 91 (1954). taining organisms (8). Recently, direct been confined to daylight hours (13). 2. P. Glees, J. Neuropath. Exp. Neural. 5, 54 (1946). observations from the bathyscaphe With the Cousteau Soucoupe Sous Ma- 3. - and W. J. H. Nauta, Monatsschr. Trieste showed that another type of rine "diving saucer" (14), four dives Psychiat. Neurol. 129, 74 (1955); D. H. L. Evans and L. 14. Hamlyn, J. Anat. London organism at the opposite end of the were made on 3 and 4 February 1965, 90, 193 (3956); D. Bowsher, A. Brodal, F. Walberg, Brain 83, 150 (1960). phylogenetic scale, siphonophores of in about 1300 m of water, approxi- 4. R. P. Eager and R. J. Barrnett, Anat. I<ec- the suborder Physonectae (9), must be mately 10 miles (16 km) southeast of ord 148, 368 (1964); R. A. Giolli, J. Histo- &em. C.~tocliem.13, 206 ( 1965). considered as the cause of some lay- Cape San Lucas, Baja California. Ob- 5. R. W. Guillerv and H. J. Ralston. Science ers (10). These polymorphic co- servations were made while the layers 143, 1331 (1964). 6. E. G. Gray and R. W. Guillery, J. Physinl. elenterates consist of various types of were at the surface; at intermediate London 157. 381 (1961). individuals arranged along a contractile depths while the layers were migrat- 7. D. C. pease, Anat. Record 142, 342 (1962). 8. L. E. Westrum and R. D. Lund, J. Cell stem. Because of its gelatinous nature, ing upward and downward; and in the Science, in press. 9. L. E. Westrum, J. Microsropie 4, 275 (1965). the colony should have a sound im- upper regions of the main layer while 10. We thank D. H. L. Evans lor advice, B. G. pedance similar to that of water. A it was at its daytime level. The saucer Cragg and E. G. Gray for reading the manu- script, and E. Mansell for technical assistance. terminally born, buoyant individual is a small, two-man vehicle which is One of us (L.E.W.) is a postdoctoral fellow (pneumatophore), however, generates limited to a depth of 300 m. This is of NIH. and retains carbon monoxide bubbles too shallow to penetrate through 27 December 1965 which approximate the resonant size most scattering layers at their daytime for echo sounder frequencies (11). levels, but maneuverability, ease of Thus, much of the acoustical evidence launching and recovery, and hovering implicating fishes with swim bladders ability make it ideally suited for such Deep Scattering Layer (5, 8, 12) is also applicable to phy- an operation. Thus, more than 14 Migration and Composition: sonects. hours of a 36-hour period were spent The causative animals, in addition in underwater observations, and two Observations from a Diving Saucer to being efficient sound scatterers, must complete cycles of scattering layer mi- Abstract. The distribution of a form widely distributed populations grations were studied in detail. This myctophid fish and physonect siphono- spatially related to the layers. Obvi- probably constitutes the first in situ phores observed during dives in the ously, they must also undergo vertical observation of migrating myctophids Soucoupe off Baja California closely migrations of the extent and rate of and physonects, and permits correla- correlates with scattering layers re- the recorded layers. Both fishes and tion of these organisms with compo- corded simultaneously with a 12-ki.y/ physonects are inadequately sampled nents of a complex scattering layer. sec echo sounder. These organism's by standard net tows, and only scant High-resolution echo sounder rec- were observed while they were migrat- data on their migratory movements are ords show that nlultiple and double ing vertically, and at their night and available from this source. Earlier ob- component layers are common (2, 5). daytime levels. They are capable of servations from submersible vehicles The deep scattering layer off Cape San rapid, extensive changes in depth. also leave this question in doubt. Be- Lucas was no exception. On 31 Janu- cause of operational limitations, the ary, and during the dives, scattering Many meso-pelagic animals under- Trieste observations had been made on layers were surveyed from the Scripps go diurnal vertical migrations of sev- vertical penetrations of the layers at Research Vessel T-441 with a hull- eral hundred meters. Keyed to ambient light (1, 2), they move upward from mid-depths at dusk, remain near the TIME 0730 0700 0630 0600 surface throughout the night, then des- I I I I I cend at dawn to their daytime levels. Parallel movements of ubiquitous, stratified zones of sonic reverberation in the oceans discovered during World War I1 (3) led Johnson (4) to the conclusion that similar organisms were the cause of these deep scatter- ing layers. In the intervening 20 years diverse methods have been used in an effort to specifically identify the respon- sible animals (5). The preponderance of evidence implicated meso-pelagic fishes, particularly the Myctophidae Fig. 1. Downward migration of scattering layers at time of saucer dive 3, 4 February 1965. Resolution between the two components of the "main" layer is vague in the (5, 6). Of acoustic importance, many photograph, but clearer in the actual recording. During most of the time, vessel of these diminutive lantern fishes T-441 was drifting. For the brief periods, from about 0601 to 0610 and again from have gas-filled swim bladders of such 0650 to 0710, the ship was under way, returning to station. At these times screw a size as to be resonant for the sound and water noise affected the resolution and intensity of the recording, and details of the separation of the "lower" layer from the "main" layer were lost. Time is recorded pulses used (12 to 24 kcy/sec) (7), from right to left, and the 20-fathom (about 40-m) depth lines are broken at 3-minute and most layers studied by appropriate intervals. Bottom is being recorded on the second cycle, and 732 m should be added methods are sharply peaked in narrow for its true depth. IS MARCH 1966 mounted, UQN 12-kcy/sec transducer, rate of rise just at sunset. From this the skiff, and adjustments in saucer a Gifft Precision Sonar Transceiver run point, upward migration was com- depth were made accordingly. During it high gain with a 0.017-sec signal pleted in about 2 hours. On two of ascent and descent of the saucer, al- length, and recorded on a Precision the observation days, weak, discrete most continuous observations were Depth Recorder model V. Heavy sur- sound reflectors (15) were present made with the use of two 1000-watt face scattering was present at night. above the main layer and rose ini- flood lamps and a 150-watt spotlight. At dawn a layer separated from the mediately above it, masking any pos- TO avoid attracting or repelling ani- surface zone and performed a dra- sible evidence of re-formation of an mals while the saucer was hovering be- matic downward migration of ap- upper layer. Diffuse scattering record- lore, during, and after passage of the proximately 300 m in 90 minutes. ed at high gain also contributcd to layers, series of 2-minute observations (Figine 1 presents the echogram oh- this masking. At dusk the lower layer were made with the lights on, alternat- tained on 4 February during the time rose rapidly, at a maximum rate of ing with 3-minute waits in darkness. of saucer dive 3, and is typical of the 12 m/min, eventually fusing with the For the first 1% minutes of the ob- morning migrations.) When the mi- main layer. The nature and behavior servational periods, the regular flooil giation was about two-thirds complet- of the layers during the 3 days of 017- lamps were used. An additional 2.5-kw ed, a diffuse upper layer split from servation were essentially the same. "movie light" mounted at the end of the main layer at the 220-m level Slight variations could be attributed an extendable arm was turned on for and disappeared from the record.