1969 (6th) Vol. 2 - Space, Technology, and The Space Congress® Proceedings Society

Apr 1st, 8:00 AM

Fishery Oceanography From Space

Kirby L. Drennan Dept. of the Interior

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Scholarly Commons Citation Drennan, Kirby L., "Fishery Oceanography From Space" (1969). The Space Congress® Proceedings. 2. https://commons.erau.edu/space-congress-proceedings/proceedings-1969-6th-v2/session-9/2

This Event is brought to you for free and open access by the Conferences at Scholarly Commons. It has been accepted for inclusion in The Space Congress® Proceedings by an authorized administrator of Scholarly Commons. For more information, please contact [email protected]. FISHERY OCEANOGRAPHY FROM SPACE Our initial effort at Pascagoula was to Kirby L. Drennan determine the potential application of standard aerial photographic techniques as a means of Bureau of Commercial Fisheries obtaining quantitative and qualitative data on Exploratory Fishing and Gear Research Base pelagic stocks. The field activities Pascagoula, Mississippi associated with this program were concluded in May of 1968 after more than 1,000 schools had been photographed using black and white, color, The exploration and utilization of world and color infrared films and filter combinations. oceanic fishery resources have been limited in Sixty-five of these schools were sampled in an the past for lack of a technology which could effort to determine size and species composition. provide the observations required for rapid Simultaneous sonar soundings were also obtained assessment, real time intelligence, or the en­ of a number of schools in an effort to determine vironmental monitoring necessary to determine sub-surface configuration and school density. the space time ecosystem relationships on which Preliminary results show that both the position a predictive system could be based within usable and surface configuration of fish schools at or time factors. near the surface may be precisely determined from high altitude photography. An effort is The space agency has undertaken an exten­ now being made to correlate the photographic sive study to determine if it would be eco­ imagery with the "ground truth" data and sonar nomically feasible to develop a satellite soundings obtained during the field operations. system to survey the resources of the earth. Upon completion, forty transparencies of fish This satellite would be equipped with various schools of different species will be subjected types of sensors which operate on the principle to densitometric analyses. Transmissivity of that each object on earth reflects, absorbs, the images will be measured in the red, green, or re-emits energy in a manner characteristic and blue spectral regions, and with white light. of the object's physical and molecular structure These data will then be subjected to a statisti­ giving each its own spectral signature. The cal analysis to determine correlations between Bureau of Commercial Fisheries Exploratory spectral transmissivity and species, surface Fishing and Gear Research Base, Pascagoula, area of schools and quantity of fish in school, Mississippi, in cooperation with the National and transmissivity of image and school size. It Aeronautics Space Administration's Spacecraft is believed that this study will serve to de­ Oceanography Project, is engaged in a program termine the potential application of the photo­ which seeks to apply existing remote sensing graphic techniques employed as a means of technology to the problems of fishery resource identifying and quantifying stocks. assessment, i.e., the location, identification, and quantification of surface and near-surface The distinctive color of certain species fish stocks. Several approaches are being suggests that measurements of the spectral taken in this effort. These include studies energy distribution may reveal characteristic of the reflectance spectra of fish schools and spectral signatures which may be used to locate associated surface fish oil films; the intensity and identify fish schools in their natural en­ and spectral emittance of bioluminescence vironment under certain conditions. During associated with most schools, which may permit September 1968 the Pascagoula Base and TRW night-time detection of fish schools through Systems obtained spectral reflectance measure­ the use of low-level light sensors; and the ments of fifteen schooling species in the north­ possible application of a pulsed laser system ern Gulf of Mexico. Measurements were made on which may provide a means for locating fish single fish, fish in small groups and fish in schools at sub-surface depths. Results of schools inside impoundments using a recently studies conducted in these areas by the Bureau developed TRW Water-color Spectrometer. of Commercial Fisheries, Pascagoula Base, are the subject of this paper and are discussed This Spectrometer (figure l) was designed in the following sections. for field use, is aircraft rated, and possesses the characteristics described in table 1. It Spectro-Photographic Studies receives incoming light focused by the objective lens on a narrow slit located at the focal plane Many species of pelagic fish can be dis­ of a parabolic mirror. Light which passes tinguished on the basis of color by a qualified through the slit is reflected by the spherical observer. These color differences are used mirror onto a reflection diffraction grating, by spotter pilots of the commercial fishing The diffracted light reflected from the grating industry to locate and identify commercial fish is reflected by the spherical mirror and focused stocks. The experienced spotter also uses a on the base of the rotating disc located in the number of other features in addition to color, front of the sensitive end of a multiplier photo­ to locate and identify fish. These are the tube. A slit in the rotating disc allows only presence of fish-oil films, diving birds, a small portion of the spectrum to reach the face ripples, and, in some cases, a churning of the of the phototube and as the disc rotates the slit waters. It is assumed, on the basis of these successively permits light from, all portions of and other considerations, that present airborne the spectrum to register on the face of the and spaceborne sensors, which outperform the phototube. In this study, output from the tube human eye in many important respects, may be was recorded on a paper strip chart recorder. used to locate and identify surface and near- surface fish stocks.

9-1 done on cloudy nights. The observational program was conducted in however, fishing is also the area extending from Cape San Bias westward dealing with the to Mexico Beach, Florida. All data were ac­ A search of the literature geographical dis­ quired aboard a Bureau vessel and from "Stage spectral characteristics and has revealed II", a Texas type tower which was made available tribution of luminescing to the Bureau of Commercial Fisheries by the the following: Defense Laboratory, Panama City, U. S. Navy Mine evident in Florida. Thirty-three of approximately 120 1. Bioluminescence is usually usually within spectra obtained during this period were ana­ the upper layers of the above the Thermocline. lyzed by TRW. Examination of these data indi­ the Euphotic Zone or that, in general, the reflectances are cate may have an separable on a species basis and are different 2. Luminescent flashes 2 microwatts per square from sea-water reflectance. The results of intensity as high as 10~ above the visual thresh­ this initial research effort prove the strong centimeter and are well potential for application of remote spectral old of the human eye. fishery resource assessment. It sensing for were appears that existing sensor technology 3. Four species of dinoflagellates also spectra with a is adequate in resolution and sensitivity to shown to have similar emission 470 and 480 ran. The discern differentials and color spectra in spectral peak between transmissivity in clear a variety of pelagic schooling species. In wavelength of maximum this study, measurements were made on a oceanic water. variety of species in an effort relatively large are recog­ an impression of the range of signatures 4. Two types of bioluminescence to gain the flash. Both might be available and the feasibility nized, the steady glow and which in Noctiluca miliaris of detecting and classifying species by remote responses can be induced mechanical stimulation. sensing. However, these data were acquired by prolonged or sudden conditions, and it must under laboratory-like agi­ whether these techniques 5. Dinoflagellates luminesce upon now be determined is observable similar results when applied to tation by schooling fish which will achieve aerial spotting of fish in the sea. The second phase from the air at night. Night schools conducted off southern this research will be concerned with the operations have been of schools. reliability and application of these techniques California to locate in a field program. During the coming months, that fish schools may be observations will be made of the reflectance 6. It appears of 10 fathoms under certain spectra of a number of commercially important seen to a depth species in their natural environment. These conditions. be made on captive schools observations will a series of range of known (monitored) en­ During the past four months under a wide by the Pascagoula conditions of sea-state, lighting tests have been conducted vironmental helicopters, fixed-wing and water turbidity. It is antici­ Base from Coast Guard conditions, oceanographic platform, the results of these tests will aircraft, a stationary pated that a Plumbicon Television the feasibility of an operational and surface vessels using determine system (figure 3). The image which will provide a means for location Image Intensifier system loaned to us by the Night Vision identification of fish school from obser­ intensifiers, and Fort Belvoir, Virginia^ amplify vations of the spectral energy distribution. Laboratories, the ambient light, or in this case the bio­ 40,000 times. This amplification Night-time Detection of Pelagic Through luminescence., is achieved through the use of a The Use of Airborne Low-Level Light Sensors of the light three-stage ijnage intensifier tube. Each stage the forward to the problem of locating is composed of a photocathode at Another approach When light fish stocks which shows end and a phosphor at the rear. and identifying pelagic stage, it acti­ use of low-level light enters the forward end of each great potential is the toward the intensifiers to detect vates an electron beam emission sensors such as image cathode, the or "fire" as it is referred phosphor end. On leaving the the bioluminescence, by an electrostatic associated with most schools. electrons are accelerated to by fishermen, at the phosphor, which con­ fishery which yields an field and focused The Spanish energy of the electron beam of 7 to 8 million pounds serves verts the kinetic annual catch The three stages in each the potential application of into visible light. to illustrate tube are interfaced by fibre In Florida this fishery is image intensifier this method. greatly intensified image on chiefly with nets and haul optics and a final, carried the third phosphor and viewed at night. The fish are sighted by the is formed on seines an eyepiece. "fire" in the water. This "fire" results through fish schools which cause from the movement of coupled to the in the water to glow The Plumbicon Television, luminescent organisms provides a highly The bodies of rapidly swimming three stage Image Intensifier, momentarily. system which combines the advantages fish are outlined with light and each leaves sensitive operation, high speed of response, and trail of fire as it moves through the water of easy a good resolution. The Plumbicon is a (figure 2). Large schools of mackerel con­ relatively tube, compared with 25-mm for most vidi- taining 5 to 10 tons are identified by indi­ 30-mm Lead oxide is used as a photoconductive vidual flashes within a larger glowing sphere cons. which gives the Plumbicon the good of bioluminescence. The "fire" can be seen surface of both the Vidicon and the Image best with the naked eye on moonless nights, qualities Orthicon,

9-2 This system has been used to observe fish schools, individual fish,, SCUBA divers, and objects towed at sub-surface depths in water masses containing both low and high concen­ trations of luminescing organisms. In recent studies conducted off the west coast of Florida, imagery was obtained of thread schools at night from altitudes of 500 to 5000 feet. Results of these tests strongly suggest that low-level light sensors may be used effectively from high altitudes as a means for locating and possibly identifying pelagic fish stocks over large oceanic areas. Application

The remote sensing system which is ex­ pected to evolve from this and other research will have both daytime and night-time sensing capabilities. It will scan wide areas of the ocean at high speeds and provide real time data on the location, quantity, and species of pelagic fish stocks in the area under sur­ veillance with a high degree of accuracy. The fishery intelligence obtained would then be relayed immediately to commercial fishing vessels In the area and to receiving stations on shore which would disseminate the data to the commercial fishing industry. The impact of an airborne/spaceborne sensing system on the commercial fishing industry would be dramatic. It would result in large scale reductions in search time and, therefore, in operating costs per unit of catch. It may also make possible profitable fishing on stocks now impossible to locate with sufficient accuracy to permit economical operations. The synoptic data which could be obtained with such a system would enable us to determine the fishery potential of a particular area in terms of availability and degree of utilization. It would also permit systematic appraisals of the near surface fishery potential of vri.de oceanic areas. A possibly more significant use of the aircraft/satellite data would be in determining the movements and concentrations of fish over space and time, which would provide us with the ability to predict when and where various species of fish can be taken at lowest cost.

9-3 INLET SLIT-,

DIFFRACTION SPHERICAL GRATING MIRROR

PHOTOMULTIPLIER 1 TO RECORDER

GEAR TRAIN 3KV DC IN

Figure '1 Water Color Spectrometer Schematic

Table 1 Water Color Spectrometer Parameters

Performance Design Off-plane Elbert Spectral range 4000 to 7500 A Type 0 RCA 7265 (S-20 Spectral resolution 50 A (at central Photomultiplier wavelengths) response) 26 by 26 mm S/N at 3000 A 800 Grating aperture line density 500 lines/mm S/N at 5000 A 700 Grating blaze 5600 A S/N at 6000 A 300 Grating focal length 9 inches S/N at 7000 A 110 Mirror slit dimen­ Scan time 1.2 seconds Scanning sions 0.0185 by 0.10 inch Instantaneous field 3° by 1/2° System speed f/8.8 Continuous identi­ Spectral calibration tape, fication Recording FM magnetic or strip chart Weight sensor 25 pounds Weight electronics 20 pounds

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